#210 - Lp(a) and its impact on heart disease | Benoît Arsenault, Ph.D.

Hey everyone. Welcome to the Drive Podcast. I'm your host, Peter Attia. This podcast, my website and my weekly newsletter all focus on the goal of translating the science of longevity into something accessible for everyone. Our goal is to provide the best content in health and wellness, full stop, and we've assembled a great team of analysts to make this happen. If you enjoy this podcast, we've created a membership program that brings you far more in depth content. If you want to take your knowledge of this space to the next level, at the end of this episode I'll explain what those benefits are. Or if you want to learn more now, head over to peterattiamd.com subscribe Now without further delay. Here's today's episode. My guest this week is Benoit Arsenault. Benoit is an Associate professor at the University Institute of Cardiology and Pulmonology of Quebec at Laval University. He's also a research scientist in the Cardiology excess at the Quebec Heart and Lung Institute in Canada. His research background is in understanding the risk of cardiovascular disease such as atherosclerosis and aortic stenosis in relation to lifestyle and inherited risk factors. This includes extensive research in the unraveling of the role of LP, HDL metabolism, PCSK9 and lipid lowering therapies. In this episode, we really dedicate our focus to that of lp, something that many of you are aware of, especially if you've been listening to this podcast for some period of time. It's a subject, of course, that we've gone into great detail, but we haven't had a dedicated podcast on this subject matter since I did an AMA on it many years and a lot has changed since then. So you may be asking, why should I care about this? Well, as Benoit points out in the podcast, while it varies by race, about 20% of the world's population is in a high risk category of lp. This is actually higher than I thought. I had always cited the number of somewhere between 8 and 12%. On top of that, most doctors aren't checking LP with their patients, and I see a lot of my patients who show up who have never heard of this or had it tested. So that means there's going to be some of you listening to this who may not realize they have a high lp. And of course that means you're at risk. In fact, LP is the single highest genetically inherited trait that confers high risk of ascvd. All of this is to say this is a very important topic for everyone to understand, because even if you don't have an Elevated lp, chances are, you know somebody who does. Now, in this discussion, we talk about a bunch of things. Of course, we go back to the basics. What is lp? We talk about the epidemiology of it, the basic biology of it, how is it inherited? How is it measured? How does it impact things besides ascvd, such as aortic stenosis and of course, ultimately myocardial infarction. We talk about the importance of measuring it in order to get the risk factors, how to manage lipids around it, et cetera. We also talk about what we know about the possible current therapies and treatments for Lp, including niacin statins, PCSK9 inhibitors, as well as the possibility on the horizon for things called antisense oligonucleotides. So without further delay, please enjoy my conversation with Benoit Arsenault. Hey, Benoit, wonderful to sit with you today and talk about a subject matter that, you know, Honestly, I think five, certainly 10 years ago, nobody would have a clue what we were talking about. And yet today we get so many requests to go back and revisit this subject matter. So again, delighted to have you here and look forward to talking about something that probably impacts a lot more people than most might appreciate. So let's take a step back and give me a sense of where your interest in this little lipoprotein LP came from.

So first, Peter, thank you so much for the wonderful invitation. I'm really excited about our discussion today. So I got involved in LPA research actually during my postdoc years. I trained here at Laval University in Quebec City, did some work in the field of lipids, looking at LDL particle size, triglycerides, APOB, et cetera, on cardiovascular outcomes. So that was in 2006-2009, and that was really at a point where not that many people talked about LP because there had been so many negative studies on LP and the risk of cardiovascular disease, like MIS and stroke and so on. And it's really the genetic association studies that have kind of resurrected the field of LP. And these were published in 2009-2011. And that was during the time I was a postdoc in Amsterdam, and I was working over there with John Castelline, and he was working on the Treating to New Targets trial, the TNT trial, which is one of the first trial that showed that if you reduce low density lipoprotein levels by increasing the statin dose, you'll get an incremental benefit in cardiovascular outcomes. So we were working on a bunch of sub analyses in that trial and they had just measured a whole panel of emerging biomarkers that could be associated with Cardiovascular events like CRP, AntiproBNP, other markers, inflammatory markers, other biomarkers of insulin sensitivity and lp. And it turned out that of a huge list of 18 biomarkers that they had measured in thousands of individuals, LP was actually the strongest of them that was predicting residual cardiovascular risk. So that was I think the first paper I published on, on LP in those years. And at the time we were also wondering if there was any genetic variants that could explain statin response, because statin work well in most people, but there's a huge inter individual variability in terms of LDL lowering associated with statins. So this came at a time where genome wide association studies were increasingly used. And they were used to. Well, they were first used to identify genetic variants associated with specific diseases, but they were beginning to be used in pharmacogenetic studies. So we were part of a big genetic consortium that was called the GIST consortium. So genomic investigation of statin therapy. And it turned out from that big analysis that LP was the most important genetic risk factor that explain statin response. So we'd shown that if you have high lp, then your LDL wouldn't be lowered as much as if you didn't have a high lp.

Well, we're going to talk about that in some detail because right now I think many people will not understand exactly why that's the case because they won't necessarily understand the relationship between LDL and LP and why what you just described is completely intuitive today based on all the work that's been done in the last decade. But let's take a step back into that epidemiology so that for the people who aren't familiar with lp, we can give them a sense of why this is such an important topic. So we'll start with an observation, right? So we'll start with the epidemiology, which is elevated levels of this particular lipoprotein, which occur in about what fraction of.

The population, depending on ethnicity? Actually it can be very high, for instance, in individuals of African ancestry who have the highest level and all the way down to Chinese and Japanese that probably have the lowest levels. We can say, like in the ballpark, that about 20% of the world population has an LP level that puts them in a higher risk category. So if we go down in time, LP was discovered in 1963 by a Swedish scientist named Carrie Berg and he was one of the first to show in the late 70s and at the beginning of the 80s in different European cohorts that LP was associated with cardiovascular events and LP was measured probably more currently at that time in these big epidemiology studies. The thing is, however, that the assays that they were using were probably not the best. They were certainly not as good as they are today. There was a lot of variability and a lot of these studies published in the 90s and in the early 2000s came out negative. So that really was really tough for the field because nobody talked about LP at that moment.

Tell people what you mean about the studies came out negative. Negative with respect to what hypothesis and why.

The hypothesis was that high LP was associated with cardiovascular events like myocardial infarction, stroke, et cetera. So the hypothesis was that people with higher LP levels were at the highest risk. And it turned out not to be the case in many, many of those studies. So we realized afterwards that the assays that had been used were probably not very good. So the assays really did not correctly identify people with high lp. And I think this has to be attributable to the complex structure of lipoprotein little A, which has in the LP genes there's a copy number variation and the antibodies that are used against that, sometimes they can bind to different epitopes of lp. So now we have antibodies that are binding to LP on other regions, so we get a much better sense of the number of LP particles in the bloodstream. But back in the days, the assays that were used, they were overestimating the isoform size that was bigger and they were underestimating the small LP isoform size, which is associated with high lp. So a lot of research has been done on that and now we have have better assay. We don't have like optimal assays now, but most of these problems have been solved and you can really see in the literature the interest on LP that actually match this effect. Because the LP gene was cloned in the 80s by the group of Angelo Scanu at the University of Chicago. And you can see it if you just look at the PubMed search, you would see like a straight line from the 70s to the mid-80s. And when these studies came back negative, you would see like the number of PubMed searches would go down. And they came back up in 2009 and 2010 when genetic association studies were beginning to be published. Because the great thing about genetic studies is that you don't necessarily need to measure lipoprotein A level. So you can look at genetic variants, at common genetic variants that are associated with diseases. And there were three big studies published in 2009 that very convincingly shows that genetic variants associated with high LP levels we're tracking with cardiovascular events. And now you can see the PubMed searches on LP going back up again and they haven't been as high as they are today.

Yeah, and we should make sure people understand some of the semantics. So LPA is the gene that codes for apolipoprotein little A, which then binds to an LDL and then turns an LDL from being just a garden variety LDL into an lp. And I think once people understand that, it becomes easier, I think, for us to communicate in this way. So I'm going to restate that and I really want everyone to understand this. So there's a gene, LPA is the gene. And this gene, everybody has this gene, but we have different variants of it. And so a subset of the population and it varies considerably by ethnicity, so African, East Asian, also quite high, down to Caucasian, and as you mentioned, Chinese, Japanese, et cetera. So you're going to see different expressions of the apolipoprotein little A, this apolipoprotein little A, which we'll talk a lot about and what it looks like and its structure and what its heterogeneity is all about. But it wraps onto a low density lipoprotein and then it becomes kind of a supercharged low density lipoprotein, it becomes a particularly nefarious LDL and we're going to talk about all the reasons why it's not responsive to the same treatments, etc. So would you add anything to that? I don't want to make it too complicated yet, but I want to make sure everybody understands when we talk about the LP gene, which is identified during the GWAS experiments, how the genotype allows us to not know everything about the phenotype, but we can start to get into trying to impute causal relationships. And eventually we're going to talk, of course, about Mendelian randomization, where we can go even deeper. So anything you would add to that, just even though we're kind of going to keep it at the 101 level for a moment just to make sure that the listeners are following as we get into the more nuanced part of this.

No, I think you've explained it perfectly, Peter. Maybe the only thing I would add is that part of the genetic heterogeneity among different people is the apolipoprotein A isoform size, so people express different LP isoforms. Some are bigger than the other. And that actually plays an important part of the equation, explaining why some people have higher LP than others.

I'm glad you reinforced that point, because. And this is going to get into a little bit of chemistry, which I know some people will understand and some might not. One of the big challenges here, as you've now alluded to twice, is the difficulty in measurement. Now, when we look at something like apob, and people who listen to this podcast a lot will be very familiar with apob. We talk an awful lot about it. One of the things we talk about is that by measuring the concentration of apob, you can completely and accurately measure the concentration of the atherogenic particles, the majority of which are ldl. And the reason for that is twofold. The first is that Every LDL has one and only one APOB 100 particle on it. The second is that all apobs are the same size, therefore, they have a molar weight. And by knowing the mass, you know the number. Now, I always like to point out two contrasts to this. Right. The HDL particle, by contrast, has multiple APOAs on it. And this is totally different from APO Little A. So we're not going to talk about that other than to say it's APO A and therefore you don't have a unique number. And then, of course, with lp, you have the problem that you raised, which creates enormous challenges. There is no molar weight for APO little A. This is the fundamental problem in the assay of trying to measure this thing.

Exactly. And we're really moving in the right direction in terms of getting the LP measurement in nanomoles per liter. And there's more and more labs that are doing this, and this is clearly the way to go. We have to move away from measurements in milligrams per deciliter, which is really influenced by the isoform size of lp. And the measurement in nanomolar will actually give you a much better sense of the number of LP particles in the circulation.

Now, will that require electrophoresis? How will that actually be measured? Or will it use nmr?

It's going to be measured through immunoturbitimetric assays, so not by nmr. NMR can actually give you a pretty good estimate of LDL particle number, but you have to use antibodies to measure lpa.

Okay, so we got a little in the weeds there. I apologize. We'll come back to that stuff later. But let's pick it up back about a decade ago, when the GWAS studies were able to distance themselves from the limitations of the assay and focus instead on the genotype and the heterogeneity of the genotype. These GWAS studies now found a much stronger association between the variants of this genotype that produced high copy numbers of apolipoprotein little A and insipid cardiovascular events. Correct.

So there were, I think, three studies that were all published in 2009. The first one was the one by Robert Clark from the uk. They used the Procardis consortium, which were, if I recall, well, there were 3,000 people with heart disease and 3,000 controls, and they've identified two SNP in the LP regions that are completely different from one another. And you really saw the dose response effect of these SNPs on LP levels with a proportional effect on the risk of heart disease. So it was like kind of the first Mendelian randomization study, where they nicely showed that if you had one LP raising allele, you had higher LP levels, whereas if you had two or more LP rising variants, then you had even higher LP levels and the risk was proportionally higher.

Also worth explaining how important this type of analysis is, because it really is the bridge between observational epidemiology and clinical trials. And of course, we're going to talk about clinical trials, many of which are ongoing. But the importance of what you just said, Benoit, is the following. There are a handful of assumptions that make this type of Mendelian randomization essential. One is the assumption that the sorting of these genes is random. Right. So, in other words, you know, we look at a population and we can look at this as though nature did an experiment and it randomized the population to different copy numbers of these alleles that are going to produce different amounts of the protein. But the second important piece of a Mendelian randomization, being able to link something causal, is the assumption that the gene of interest is not doing something else that you're unaware of. Right. In other words, if the LPA gene was on the one hand responsible for making apolipoprotein little A, which it is, but on the other side, it also changed your. I'm making this up, your susceptibility to secondhand smoke, and people who had that gene would be debilitated by secondhand smoke, people who didn't have that gene had complete immunity to secondhand smoke, imagine such a gene existed. Well, all of a sudden, the Mendelian randomization wouldn't be very helpful because those people who are at an increased risk of cardiovascular disease from having more copies of lp, you don't know if it's that or if it's the exposure or susceptibility to secondhand smoke. So do you have a sense? I mean, I think in the case of LP it's pretty straightforward because it's a relatively simple gene. But when that type of analysis was done, was it relatively easy to demonstrate that that gene wasn't doing anything else both in its coding and non coding regions?

Yeah. First let me say that I think that a lot of geneticists would disagree that LP is a relatively easy gene. I mean, there's like I think 2000 different variants that are associated with LP and you add in the isoform and each isoform has a specific set of different variants. So that being said, I think you really nicely explained it. And the beauty of working with lp, but also with most proteins in the circulation is that you're looking at cis acting SNPs. So cis acting means variants that are acting within the window of the gene that expressing their protein as in opposition to like a transacting SNP would be, for instance, a SNP in the CTP gene, for instance, which we know might be associated with lp. But CTP does a lot of other things. It regulates HDL cholesterol levels, it regulates triglycerides. So we don't use CTP genes when we do Mendelian randomization on lp. And the example that you mentioned, you know, a specific gene being associated with an intermediate phenotype that could, on the other hand influence LP would be reverse causality. And in the case of LP where very, very confident that we're using the correct genetic instruments to infer a causal relationship between LP and a wide range of atherosclerotic cardiovascular diseases.

So to put a bow on that, we really have two independent types of analyses now that make it very clear that LP is playing a causal role in the development of atherosclerotic cardiovascular disease, independent of ldl, which you referred to earlier by commenting and using the term residual risk, which I think people might not appreciate. Residual risk meaning what is the risk that remains in terms of ASCVD in the presence of LDL lowering? And of course LP would be one such example. And those two pieces of information are now the regular observational epidemiology, provided that the assays more accurately capture the measurement of lp. And now these Mendelian randomizations that effectively are nature's randomized experiments, provided those two criteria we discussed can be met, is that a fair synthesis of the state of the art today in terms of Our understanding, Yes.

I think you can also add the third assumption, which would be that the effect of the variance on the outcome, so the effect of LP variance on cardiovascular disease are explained by higher LP levels. And I think for lp, it's a fairly fair assumption to make.

Okay, so let's talk about how this is done clinically today. Over the past decade, I've seen three different types of commercial assays for measuring lp. I don't believe two of them are in existence anymore. One was the LP cholesterol content. So I assume that this was an assay that was looking at the cholesterol content of the LP, which means the LDLs that had apolipoprotein little A on them, you just measure the cholesterol content. So it was analogous to measuring LDL cholesterol, but for this narrow subset. Is that assay still in existence?

Well, I think there are certain labs that still use it, but it's really not the way that the field is moving to, because the cholesterol. And you can make the same argument for ldl, the cholesterol within certain lipoproteins does not necessarily tell you a lot of information about the number of particles that are in the bloodstream, which is the most important thing to measure if you want to estimate risk. So for LDL apob, there's some discordance, but for lp, the discordance is even higher. So what you really want to do is try to find a lab that will give you an LP measurement in nanomoles per liter.

Right now, there are some labs that have done that. I've seen a lot of those labs. So one of them was called Health Diagnostics Labs. I think that was the name of the lab. They no longer exist. They did calculate an LP in nanomole per liter. I don't know what their methodology was. Most labs are using milligrams per deciliter. So they are simply telling you. I say simply, they are telling you the mass of lp. Now, just to be clear, are we in that assay looking at the mass of the entire lp, or are they just trying to estimate the mass of the apolipoprotein little A's.

It's the mass of the particles. So it's a much better measurement than LP cholesterol that you just referred to. And we shouldn't, you know, let good be the enemy of perfect here. If you have an LP measurement in milligrams per deciliter, and it puts you in a high risk range, so let's say it gives you an LP level above 50, then the chances of the LP assay that will give you a result in nanomoles per liter. It will also give you a high level. So if you have an LP measured in milligrams per deciliter, you can obviously try to get a second measurement in nanomoles per liter. But you know, if you have a LPA in a high range, if you both methods will give you the same information that you have an LP in the higher range. Now you have to keep in mind though that if you have an LP for instance, of 50 milligrams per deciliter, the measurement in nanomoles per liter will be around 125 nanomoles per liter. So some people have measurements using both methods and they just say, well, for some reason my LP doubled. Well, that's not the case. The LPA didn't double and it's remarkably stable over time. So most guidelines will probably tell you just to measure LP once in a lifetime and it's relatively stable.

Yeah, I mean, I think that's the take home point here is unlike LDL and apob, which are so modifiable, and therefore it really matters that you know what you're measuring, because you're going to be measuring it over and over and over and over again with LP at this point in time and this is going to be changing, but at this point in time, it's basically something we measure to determine risk, after which point we don't really need to measure it. We've established risk and now we need to take measures elsewhere. So let's now kind of talk a little bit about the biology of lp. We'll include figures in the show notes to the podcast. So we'll be able to show people exactly what this thing looks like and how it intersects with and binds to the LDL particle, how it's distinct from the apob, et cetera. But let's talk a little bit about the production of this thing. Is it hepatically produced? It's produced in the liver.

Yes, exactly. So all the lipoprotein A particles originate from the apo lipoprotein little A. That's pretty much only expressed in the liver. So it's not entirely clear in the literature how or where specifically an apolipoprotein will become an lp. So where it will bind to apob and ultimately an LDL particles, there's multiple hypotheses that have been tested. So some people say that the apolipoprotein little A, which is like a glycoprotein is secreted in the bloodstream and there it will bind to whichever LDL is closer to it to form lp. There's another hypothesis that suggests that it's probably at earlier after the secretion of Lp, so not entirely in the bloodstream, but when it leaves hepatocyte in the space of this in the liver, that the binding of Apo lipoprotein literally with ldl. But now I think we have very good evidence to suggest that this happens within liver cell. The binding of APO A to Apo B to eventually form lpa. So there's good evidence to suggest that as soon as the APO is produced, it can form LPA when it meets with an apob particle.

And for whatever reason, that just seems a bit more intuitively obvious given the mechanics of it. Right. You're bringing so many LDLs to the liver, you're making apolipoprotein little A in the liver. It seems like a more obvious place for the marriage to occur than in the periphery. But again, it remains to be seen, although seems like it's more likely that that is the case. Correct?

Correct. And so the levels of LP are determined by the rate of production of LP particle and little by its catabolism. We're still not entirely sure of how the catabolism of LP occurs. Most of it is by the liver. There's a little bit of catabolism by the kidney as well. But identifying like the receptor at the surface of hepatocyte that will remove LP from the bloodstream has been challenging. So there's some evidence suggesting that the LDL receptor might be one of them. There's some evidence for and against that. And there's also the plasminogen receptor. And I think we're going to eventually talk about about the homology between apolipoprotein little A and plasminogen.

So let's go back to this point, which is that it's really the production of apolipoprotein that determines the concentration of Lp. And if that weren't the case, it might be that by simply reducing the amount of targets for it, that is reducing the amount of ldl, you might reduce the amount of Lp. But in fact, that does not appear to be true, with one notable exception that we will get to down the line. In other words, if you give somebody a statin, which is a very potent drug to lower ldl, the primary mechanism by which it does so is by increasing hepatic clearance of ldl. So you have more and longer lasting LDL receptors on the liver, and they're pulling those LDL out of circulation, which is lowering the plasma concentration. And yet that does nothing to offset the amount of lp. Which goes back to the explanation that started your journey here, which was, why is it that some people respond really well to statins and some don't? And obviously it would be the higher your lp, the worse your statin response, because there's a subset of your LDL that are not responding to the statin. So maybe let's start by explaining how a statin takes an LDL out of circulation and why this doesn't work for an lp, which is basically just an LDL with this one other little thing covalently bound to it.

Exactly. So the statins actually reduce LDL particles in the circulation by upregulating the LDL receptor at the surface of hepatocytes. So the density of the LDL receptor at the surface of the hepatocyte is super important. The more LDL receptor you have, the higher the catabolism of APOB containing lipoproteins will be because APOB binds to the LDL receptor. So under the assumption that LP is catabolized by the LDL receptor, you would think that statins would actually reduce LP levels. Whereas we see that there's not really a lowering effect of statins on lp. And there's even been more than one studies that have shown that if you put somebody on a statin, you'll even have a small increase in LP levels. Now, that shouldn't be a reason not to put someone on a statin, of course, because there's been trials like the heart Protection study that have shown that a treatment with statin is beneficial in patients with high LP level, maybe even more so than patients with low LP levels. So one should not, like, don't prescribe a statin because you're afraid of a small LP level. It might be an interesting thing to do to measure LP levels before and after the initiation of a statin, but overall, we have so much experience with statin that we know they work in the overwhelming majority of individuals, and especially even better in patients with high lp.

Yeah, I mean, one hypothesis for that might be that the statins are bringing a higher influx of LDL to the site of the production of the apolipoprotein little A, and that might possibly be why you're seeing an increase in lp. If that were true, that would make it even more likely. The scenario that that's the source of the merger between apolipoprotein Little A and ldl. What's the magnitude by which LP would go up in the context of a statin?

Well, that depends on the study. There's been a lot of studies that have shown that statins don't have an effect, and most of the studies have shown like a 10% increment in LP level. So if you have low LP levels and you're treated with a statin, you'll still remain with a low LP level. And if you have high LP level, then you'll obviously still remain with a high LP level, although it's going to be a little bit higher. So it's important to say that as we move forward with LP lowering drugs that are being tested on top of statin therapy at the moment. So we have published a paper in patients with aortic valve stenosis, the ASTRONOMER trial, where you can actually give, I think it was a 20% increment in lipoprotein, so it might not be trivial. So the signal is there. But let me restate that statins are very effective in patients with LP even though there's a small increment of lp.

Yeah, and an easy way to think about this would be if you give a statin and let's say in the most aggressive case, the LP goes up by 10%, but the APOB comes down by 60%. You'd have to make the case that an LP is six times more atherogenic on a particle for particle basis for that to be an equivalence maneuver. So that begs the question, what is it about LP that's so virulent? What is it about LP that makes it, I assume, more atherogenic on a particle for particle basis than its garden variety apob bearing cousins.

Yeah, there's no question about this, Peter. I mean, on a per particle basis, LP is much more atherogenic than an equivalent LDL particles. Well, first of all, an LP has an LDL particle on it. So by definition it's, you know, as atherogenic. Just to start with, there's also evidence that LPA might influence the rates of thrombosis because LP has a sequence homology with plasminogen, which plays, plays a role in clotting and has antifibrinolytic activity. But I think the most important thing is the number of oxidized phospholipids that are transported by lipoprotein, which is much higher than the amount of oxidized phospholipids that you see on LDL particles. And oxidized phospholipids have effects on a wide variety of cells. Endothelial cells, smooth muscle cells, macrophages, cells of the aortic valve, like valvular interstitial cells. Now, they're sending in signals that will drive pro inflammatory, maybe prothrombotic and pro calcifying signals to these cells. So that is probably the most important reason why, on a per particle basis, LP is more atherogenic than LPL than ldl. Sorry.

So let's talk about these oxidized phospholipids. I think most people might not be familiar with what a phospholipid is. But before we do that, let's explain to people what an LDL looks like physically in relation to an ldl. So if an LDL is a largely spherical compound that has on its surface a single lipoprotein called APOB100 that wraps around it, how does that now interact with the apolipoprotein little A to become an lp?

Okay, so to answer this question, I'm going to tell you a little bit about the structure of apolipoprotein little A. And to explain that, I'm going to talk about plasminogen for a minute. So plasminogen is a gene that's expressed on chromosome 6. It has five Kringle repeats. It's called a kringle because it resembles a Danish pastry. So it's a little round of proteins, and you have five of them that are one another in the protein. Now, LPA is the gene right next to plasminogen on chromosome 6. And we have reasons to believe that along the lines of evolution, it probably emerged from a duplication of the plasminogen.

Gene, which would have been very important tens and hundreds of thousands of years ago because trauma was such a threat to our species, much more than it is today. And of course, trauma carries with it, in the short term, an immediate risk of hemorrhagic shock, blood loss. Ultimately, septic shock probably would have killed just as many people from the infection. But anything that would have reduced your risk of hemorrhagic shock would have been generally positive thing up until a hundred years ago or a couple hundred years ago. So tell people exactly how plasminogen would have played a role in that and why this is something that, if a duplication was created, probably worked to an evolutionary advantage again until we lived long enough for it not to.

Yeah, there's a lot of hypotheses out there, and the Effect of LP on wound healing is certainly one of them. And this is being studied ex viv. So that might be one of the reason why we have high LP levels in 20% of the population and why before that even there was the duplication of the plasminogen gene. Now, when we're talking about that duplication, it's only the Kringle4 and Kringle5 that remain in the LP gene. And the Kringle4 is even separated in 10 different subunits. So there's the Kringle4 type 1 all the way to the Kringle4 type 10. Now, the most important is probably the Kringle4 type 2, which is where the copy number variation is. So one can have one Kringle4 type 2 or only a couple. And you can also have the way all up to 40 Kringle 4 type 2 repeats. So this is where when we talk about LPA isoform size, it's due to variation in Kringle 4 type 2. So there's other Kringle parts that are important. Kringle 4 type 10 is probably the most important for the binding of oxidized phospholipid. And to answer your question, Peter, about the interaction between Apo A and Apob, you have to look at the Kringle 4 type 9, which contains cysteine residues, which are important to do a disulfide bridge with apob, so it's a covalent bound that's happening because of the cysteine residues on Kringle 4 type 9.

So, interesting sort of thought experiment. The reason I'm asking this question is not just to be difficult. It's to try to understand the pathophysiology a bit better, especially as it pertains to the oxidized phospholipid. If you could create a drug that would cleave that disulfide bond so it wouldn't lower apob and it wouldn't lower apolipoprotein Little A, it would just prevent their union and therefore it would eliminate lp. But you still had a high concentration of apolipoprotein Little A floating around by itself, dragging with it oxidized phospholipids. Would you guess that it would still be problematic or would your guess be that no, because it wouldn't be able to gain residence in the tissues, such as the subendothelial space, the interstitial space of the aortic valve, all the places where it wreaks havoc.

Yeah, I'm only going to speculate here, Peter. Of course, I don't think there's solid data on the form of APOA that's not bound to LDL particles. So we know that APOA can still have oxidized phospholipids, and we are not entirely sure how. If you're talking about lpa, how it gets inside the cells, if it gets inside the cells. Now, we have some evidence, and we've published that with a colleague of mine, Patrick Mathieu here, who's a heart surgeon, we've looked at an LP receptor in the valvular interstitial cell. So these are the types of cells that are very abundant in the aortic valve. And just to remind our audience, LP is also associated to a very significant extent to aortic valve stenosis. And when I'm talking about LPA receptor, I'm not talking about the receptor for lipoprotein little A, I'm talking about the receptor for lysophosphatidic acid, which is generated by LPA by an enzyme called ototaxin, which is actually carried by LP in the blood. So on top of oxidized phospholipids, apob, ldl, LP has its specific proteome. So it carries a lot of different proteins that have different function. That makes LP even more atherogenic. Now, these oxidized phospholipids can have a signaling effect in the aortic valve, and that might be totally independent from ldl. So we don't know. I'm only speculating here, but there's some signaling effects of oxidized phospholipids that I think are very important. And they activate a lot of different inflammatory processes and also osteoblastic processes, because these types of valvular interstitial cells are becoming like osteoblasts, which are the cell types that make bones. So it makes a lot of sense, you know, when you're talking about aortic valve calcification, that there's a bone like process that's happening within this tissue.

Yeah. For all of our patients that have elevated lp, one of the first tests we do is get a baseline look at their aortic valve. So typically we'll do it with an echocardiogram if we can get a good enough view. If not, we'll use a cardiac mri. But it's for exactly this reason. What's the approximate hazard ratio? How much does risk go up for aortic stenosis in an individual with elevated lp, and how much does it depend on whether or not they have a normal aortic valve to begin with, with which has three leaflets, a so called tricuspid valve, versus if they have a relatively common anatomic variant with only two leaflets, which is called a bicuspid valve, which even outside of lp would increase your risk for stenosis.

Exactly. So there's not really good evidence showing that LP is associated with bicuspid aortic valve stenosis, because we're studying genes that are associated with bicuspid aortic valve stenosis and we don't see really an effect of LP there. Now that being said, it might accelerate the formation of aortic stenosis in patients with bicuspid aortic valve who are already at risk. Exactly. So LP is probably an initiator of aortic valve stenosis. And we've known that since 2013 when George Tanasoulis and Wendy Post published this genome wide association studies of aortic valve calcification in the CHARGE consortium. And they've shown that lp, that one variant associated with high LP level, was the most important variant associated with aortic valve disease. Now, we had known for a few years that LP was present in the valve, and in the valve it actually co localizes with oxidized phospholipids. So we knew this, but that study was really, I think, a game changer for our understanding of aortic valve stenosis. Now, when we're looking at the effect of high LP on aortic valve stenosis, it really depends on the level of Lp. So if you're looking at patients that have high ish Lp levels, such as, let's say 50 milligrams per deciliter or 125 nanomolar, their risk can be increased by 50% to maybe 100% or double. But when you're going and you look at patients that have very high lp, the risk can increase quite substantially. So if you have patients with very high LP level, then what you're doing looking at the aortic valve, especially by echo, because it's probably the most widely available tool to investigate this. In our lab we performed sodium fluoride petct, so positron emission tomography coupled with computed tomography, using a radio tracer that's called sodium fluoride, and in patients that have high LP levels, but these were patients from the general population, we can already see like a signal before the onset of aortic valve calcification using this radio tracer. So this really tells you that there's an effect of LP on the initiation of the process of aortic valve stenosis.

So you're seeing before any gradient appears, before any flow related metric, you're seeing a metabolic change at the valve.

Yeah, exactly. So the sodium fluoride will actually bind to a chemical called hydroxyapatite, which is literally a complex of calcium and phosphorus, which will eventually be involved in the pathophysiology of aortic valve stenosis. And we see that process happening at the earliest stage of the disease, and we also see an effect of LP on the later stage of the disease. So the data that's available so far that have looked at the progression rates of aortic valve stenosis has shown that patients with high LP might even progress more rapidly than patients who have low lp, especially within younger patients that have high lp. Because when you're looking at patients, you know, that are above 75 or 80, there's a lot of calcium that's already present in the valve. And the mechanism might be very different in younger patients compared to older patients. When we're investigating the progression of aortic valve stenosis.

Yeah. And if we're going to create a public service announcement here for primary care physicians, it's so important to identify aortic stenosis in its earliest stages because the outcome data are quite clear that the earlier you intervene, the better the outcome. So, you know, I think 25 years ago, we had a certain threshold in terms of surface area of the valve and gradient of pressure across the valve, at which point you would replace the aortic valve. If you look at the literature today, it seems that you're getting better and better outcomes when you proceed earlier and earlier, before the heart is overly taxed, based on that pressure head that it faces, and of course, the increased risk of spontaneous cardiac death and other things that goes up with aortic stenosis. So. So aortic stenosis is a very serious problem, independent of ascvd, atherosclerotic cardiovascular disease, which is what most people think of when they think of lp, assuming they know something about what we're talking about in terms of this molecule. So let's go back to another point you raised. And again, I think when people look at the diagram, this will be much easier. We get into the anatomy of the fourth and fifth region of these Kringle repeats and which of the subunits can create this vast heterogeneous. Why two people can have an LPA gene that overexpresses, well, LPA through apolipoprotein lin, one of them can have A molar mass that's very high, one can have a molar mass that's very low because of these number of Kringle repeats. What does the number of these repeats tell us about the pathophysiology of this?

Well, if you had asked me that question 10 years ago, I would have said a lot. But our understanding of the pathophysiology of LP is, is increasing every week now, basically. So maybe 10 years ago there was this debate about LP as to whether or not it was the LP concentration that matter, or if LP concentration didn't matter at all because it's the APOA isoform size that matter, small isoform size being associated with higher LP levels. And there has been some epidemiological studies that have, have measured APOA isoform size, either through PCR or immunoblotting, et cetera. So in the same patient, you can have LPA levels measured and you can have the APOA isoform size. And using the techniques that were available back then, they did multiple adjustments, adjusting LP concentration for the APO isoform size and looking at the association of APO isoform size with outcome, adjusting for LP levels. And the data back then was going all over the place, basically. So some studies were saying it's the concentration, some other studies were saying it's the APO isoform size that matters. Once again, these questions were ultimately resolved by looking at genetics. So there's one variant that's associated with small LP isoform size, but that's also associated with a low lpa. So you can see this was our way to do a discordance analysis by looking at that specific snp. And that genetic variant was not associated with cardiovascular diseases at all. And in many studies now it's been shown that probably the best study that has investigated that is a study from the Decode cohort, which is a cohort from Iceland. They did whole genome sequencing, and I think it was 15,000 individuals. And they've shown unequivocally that the LP isoform size, even though you can sequence it, really was not associated with the risk of heart attacks and strokes once you take into consideration LP levels. So it's really the LP number that matters, and that's actually very positive for the feedback because there's so many puzzles that we still need to figure out in terms of the association between LP and risk. So at least we can convincingly say that it's the number of LP particles that matter and not necessarily the isoform size, and that the isoform size matters because it's associated with different levels of LP and not through an independent effect.

So really, this, for once, creates a beautiful symmetry here, which is it mirrors apob. The first, second and third order factor in the harm caused by an LDL particle is the number of the particles, the size. All of those things only factor into the number. So why is it that smaller particles are more often associated with a poor phenotype? Because when you have smaller particles, you generally have more of them. So that's good to know. Do we have a sense of. Of the complexity in why some families? Because again, we didn't talk about the inheritance of this. So before I ask this question, let's go back and explain the inheritance of this. It's a very important piece of the puzzle. How is this gene inherited? And what are the implications for people who have elevated levels of this as far as their offspring?

That's a very good question. So the pattern of inheritance is through autosomal dominance. Pattern of inheritance. So, like for instance, if you compare it with a monogenic disorder, let's say familial hypercholesterolemia in Quebec, we have a very famous mutation, which is a 15 kilobase deletion in the LDL receptor. So if you inherit at least one copy, you know you'll have FH for lp. If you inherit a genetic variant that's associated with high lpa, chances are you'll have high LP as well, because you only need one variant and not necessarily two. So you need either the allele from your father or your mother that will rise lp. But it's a bit more complex than that, because we cannot necessarily consider it a monogenic disorder, because there's 2,000 different variants in the LP region that are associated with high LP. So your father can have a high LPA because of a specific variant, and your mother can have an LP variant that lowers LPA. But it depends on the combination of SNPs that you will ultimately get. So it's not as clear as any monogenic disorder, even though it's a dominant mode of inheritance. It's been shown that the children, they have very different LP levels than their mothers and fathers, and you cannot really estimate it. So you really have to measure it. And for people that are asking the question, at what time I should get an LP measurement, let's say if I had a heart attack at an early age and I want to prevent that in my children, then we know that the LP gene is fully expressed by age 2 in the liver, of course, and that the levels that you will get at 5 years old are probably going to remain. Well, maybe not the same levels, but if you have high levels by age five, it will increase through adulthood, but very, very slowly.

Yeah. So again, some very important information there. Right. Piece one of that is you cannot predict the phenotype of the offspring from the phenotype of the parents. And let's contrast this with apoe, the gene. By the way, there's a lot of parallels between APOE and lpa. APOE is a gene that today doesn't seem to serve much of a purpose. All it seems to do is increase your risk of of Alzheimer's disease and even increase your risk of cardiovascular disease. Independent of that, there are three isoforms, the 2, 3, 4 type and it's this fourth type that's high risk. So you can argue how in the world does this gene exist? And of course the answer is evolution wasn't really thinking about Alzheimer's disease, so therefore there must have been some benefit of it. And of course we now know there is. Right. This genotype was associated with protection from parasitic infections in the brain. Brain, which would have been far more to our advantage 100,000 years ago, 50,000 years ago, 10,000 years ago, than the downside of Alzheimer's disease in your 70s or 80s. But with APOE, because you have these three discrete isoforms, you only have six combinations and therefore, if you know what the parents isoforms are, you can probabilistically give a distribution for what the children will be. You still would need to measure it, of course, but there's a finite number of outcomes. Now, of course, there you're measuring genotype and not phenotype. We don't measure the phenotype of APOE yet. So here you have so many genes that are associated with this thing that if the parents are both elevated, the probability that the offspring are going to be elevated seems pretty high. If one parent is elevated and the other is not, there's a pretty decent chance that the offspring will not. Tell me about the situation in which both parents are not elevated but yet could carry variants of LP that when combined could elevate. Has that been observed or does one safely say if both of your parents are below 30 milligrams per deciliter, the probability that you are going to be north of 50 is very small. Small.

I think it's very small, but you still have to measure it. To be honest, I don't think I would know the answer to that. Most guidelines will tell you to measure it in everybody at least once. In their lifetime.

And when do the guidelines suggest that that start? Do the guidelines suggest doing it in adolescence when you have a long enough Runway to take action? If the LP is elevated, or do they not specify?

I don't think they specify that. And the guidelines are actually just starting to advise for LP measurements. So some guidelines, like the American Heart association guidelines, which are probably less favorable for LP measurement, they'll tell you to measure. I don't remember exactly, but in patients with atherosclerotic cardiovascular disease or with a family history of atherosterotic cardiovascular disease, in patients with familial hypercholesterolemia, or in patients with aortic valve stenosis.

So in other words, measure the LP once they've demonstrated that the disease that it causes is present?

Pretty much.

That's fantastic advice. That's excellent insight.

Yeah. But if you look at the Canadian guidelines, they'll tell you to measure it in everybody at least once in their lifetime.

And by the way, this is where Canadians also stand out over Americans. Canadians have long adopted the measurement of APOB as the superior measurement to quantify LDL risk. And yet here in the United States, the guidelines still favor the use of LDL cholesterol, which is clearly inferior to apob.

Yeah, absolutely. So I would like to comment on that. I think the Canadian guidelines are much more up to date with the recent literature on that. There's clearly no doubt about it.

As are the European guidelines, while we're on the topic. Right. The European guidelines, the Canadian guidelines are in line with the available evidence, and the United States guidelines are. Are just 40 years out of date. But that's all.

Yeah, absolutely. And the European guidelines actually advised to measure LP in everybody for a different reason. It was to identify patients who have very, very high LP levels, because we realize throughout the years that having a super high LP might be a cause for familial hypercholesterolemia. You need to measure LDL to diagnose familial hypercholesterolemia. And after mutation in the ldl, recept variation in the LPA gene might even be the second cause of familial hypercholesterolemia. And the reason for that is quite simple, because when you measure ldl, you also measure LP cholesterol. So if you have a very high LDL and also a very high lp, there's a very good chance that the high LDL cholesterol will actually be high, high LP cholesterol. I think it's really underappreciated. And actually that's the reason why it's in the European guidelines. But now I think most of the guidelines that will be put forward will just simply for whatever reason, to measure LP at least once. And I don't know if it's in the pediatric guidelines because I don't really follow that literature. But maybe in children who have strokes at a young age, many of them have high lp. So it's not as clean as the literature in adults, but there's been a lot of studies looking at high LP and stroke in children. So if you have a family history or relatives that had stroke at a young age, it might be a good idea to measure LP as well.

Yeah, that's actually a terrifying thought, by the way. My view on these things, of course, is just the amount of energy that goes into debating it is so ridiculous compared to the relatively low cost of simply measuring the thing. People who debate why would you spend $14 on an APOB test? It's like if your life isn't worth $14, we shouldn't be having this discussion. Same is true for measuring lp. So I think it should be done on everybody. Non negotiable. Certainly before your 18th birthday. That would be my thinking on this. So let's go back now. What's the greatest that you've seen? Number of LP to ldl? I had a patient once when we were measuring both in nanomole per liter who had an LP of 690 nanomole per liter in the context of an LDL particle concentration of about 1800 nanomole per liter. So a little over one third of his LDL were lp. I assume you've seen numbers even in excess of that.

Yeah, well, just to be clear, Peter, I don't see patients. I'm a biochemist and I've seen some very interesting case reports on children that have FH and high lpa. Some of them even had to have liver transplant because the lipids were just so high and they were having events in children years. But those are only case reports. Of course, it's not mainstream and I wouldn't want to scare anybody, but this is as dangerous as it can get.

So let's talk about other therapies that have been proposed. So there was certainly a day. And sadly there are still a number of physicians that I interact with, including those who carry the title of lipidologist, who are recommending the use of niacin to lower lp. Can you talk a little bit about the history of that? And at the risk of spoiling the punchline, why we do not believe that is a good idea.

Well, it was even in the latest guidelines of the European Atherosclerosis Society to advise niacin treatment in some patients with high lpa. We did not have large cardiovascular outcome studies on literally any effect of niacin therapy. Now, we know that niacin therapy will actually reduce LP levels, it will increase hd, it will lower triglycerides. So the effects on plasma lipids are actually pretty good. However, you know, if you're looking at LPA, the reduction, the mean reduction will probably be about 20 or 30% with niacin. And there are, as you say, some lipidologists that have seen, like, very important reductions of LP with niacin that they've decided to keep those patients on niacin. And I don't see any problem with that. The thing is, however, when you look at the actual evidence, we have two large cardiovascular outcomes trials, we have the AIM High Trial and the Heart Protection Study, two Trive trial, that have shown that there's no cardiovascular benefits in treating anyone with niacin. And we see a lot of side effects as well, flushing being the most important side effect of niacin. So we have those risks and we don't have that many benefits. So that's why niacin is not as prescribed as it once was. There are still people that are using it. Niacin reduces the production of LP and LP still predicts the risk of events in patients treated with niacin. So we know that from the AIM High trial. So when you're looking at the cost to benefit ratio for niacin, the evidence really isn't there to support niacin treatment.

Why do you think this is? If we look at the effect of niacin on raising hdl, which it does, right, HDL cholesterol goes up with niacin administration at a high enough dose. But the outcome trials are very clear that that does not translate into benefit. It makes you think a little bit of the CTEP trials where you give a CTEP inhibitor, HDL cholesterol goes up. In some cases you actually saw more events, but usually at best, you see no effect there. It's a little easier to argue why that could be happening when you look at the complexity of HDL biology and you understand how much we don't understand and therefore that HDL functionality is what really matters, and we don't have an assay for HDL functionality. So these things that we measure, like the amount of cholesterol in an HDL particle is a Pretty useless measurement in that it tells us nothing about how the HDL actually works. Works, especially when you consider that you can have high cholesterol in an HDL particle because of all the cholesterol that's entering it. Or you could have high cholesterol in an HDL particle because not much cholesterol is leaving it. Those would be two completely different states of affairs. And again, it makes sense why you can dismiss the notion that raising HDL cholesterol is valuable pharmacologically. In the case of lp, it's a bit more confusing because as you said, niacin actually inhibits the production of apolipoprotein. And for all of the nastiness associated with LDL and lp, their biology is actually easier to understand. In other words, the things that they're doing to hurt you are easier to understand than what HDL is doing to help you. So why do you think there is not a more clear signal between the use of niacin and the reduction of events?

Yeah, it's a very good question. The Mendelian randomization studies have been very clear that you will need a very large reduction in LP to produce cardiovascular benefits. The first study I suggested, because it's basically only modeling, right? There's no trial data, so we can at best estimate the treatment effect. So it's suggested that you needed 100 milligrams per deciliter reduction in LP to get, get a benefit in a trial that would be comparable to a statin treatment. Like a 20% reduction over what period.

Of time you'd need to see that in a five year window.

Yeah, well that's actually the problem because when you're looking at Mendelian randomization studies, you're looking at primary prevention and we're looking at lifelong reduction. So it's very hard to estimate a trial.

Oh. So the Mr. Says if you want to take that mortality curve down to the next rung, it's 100 milligram per deciliter reduction and lifetime exposure.

There was one study that showed that. There's other study that came out after that that said, well, it's probably not 100. It might be around 50 milligrams per deciliter, but it's still high. So you need a large effect. So it's not a 20% reduction, but.

There'S a bigger point there, which you alluded to, that's over the course of your life. That means over five years you might have to basically obliterate it. If you're going to want to See a benefit.

Yes. And. Well, that's what the antisense oligol nucleotides will do, and I guess we'll come back to that later. But when they compare it to ldl, though, they also compare it to lifelong exposure to lower ldl. So they're not necessarily comparing lifelong reduction to trial data that, you know, with statin trials, we have between two and seven years length of treatment in patients that already have disease. So you cannot really compare apple and orange oranges. But when you compare the lifelong effect, and that's obviously a caveat of those studies, because you're trying to estimate the results of a trial using lifelong effects. So you have to take some and leave some for those kinds of studies. But I want to come back to something that you said about CTP inhibitors, because we do have evidence, at least for the anacetrapib, that it might lead to cardiovascular benefits.

Was that the Merck one?

Yes, it's the Merck one.

And they stopped the trial even though it was trending in a positive direction, is that correct?

Exactly. So there's one reason for that, was that they saw a lot of drug accumulation in adipose tissue, which is not something you want if you want to prescribe a lifelong treatment. And the second thing is that while the treatment effect was not spectacularly high, I think it was was a 6% reduction in the rate of events. I'm saying this because you talk about HDL and functionality, and in that trial, I don't remember the name of the trial. It was a reveal trial.

Yeah, that was stopped about two years ago. It was relatively recent. Maybe three years ago. Right.

Maybe a little bit more than that. But it was a big trial, I think 30,000 patients. So this is why we need big trials in that arena. So what they showed is that it was the reduction in the number of APOB lipoproteins that actually mattered. It really didn't matter. Like, the risk was not proportional to the HDL rising effect. It was proportional to the APOB lowering effect. And when you're looking, and if you plot all the clinical trials together, if you plot the APOB lowering effect to the reduction in cardiovascular disease, you can see that all these trials line perfectly on the line. And even that specific trial with Anisatopib, it fell right on the line. Same with PCSK9 inhibitors, same with Ezetimibe. Any LDL lowering drug that's out there, maybe a few exceptions, but it will land on this line. So it's really not about hdl. So Much. When they developed the drug, they thought it was about hdl, of course, but it's really funny because actually it just further convinced us to hit on APOB containing lipoproteins as hard as we can.

Yeah, it is kind of the silver lining in all of this. Sometimes it's easy, if you think about this stuff too much philosophically, to lament the fact that we even have apob. Right. Because there's no real need for apob. You know, we could survive with no circulating APOB and we wouldn't have any atherosclerotic disease. So every time you get a little depressed and have that thought, you can also realize how fortunate are we that the biology of APOB is so much more well understood than that of APO A. Now I'm talking apobig A. And that eradicating APOB is becoming easier and easier and easier and safer and safer and safer. And it's the single most important thing that you can do in the plasma to reduce the risk of atherosclerotic disease. I mean, all of these things make for a very fortunate turn of events for our species. And that's why turning to this pesky LP is so important. Important because of what you described at the outset, which is this residual risk in the individuals. And it's interesting, you talked about 20%. That's higher than the number I quote my patients. I usually tell my patients it's 10%. So I've been understating this for some time. I didn't realize it. So all comers, 20% of the population would be over 50 milligrams per deciliter.

Yeah. Depending on ethnicity. So it's certainly above 15%, no doubt about it. And in some population, especially in populations of African ancestry, they have the highest LP levels. And they also have the highest LP levels, adjusted for LP isoform size as well. So in most individuals, if you look at the distribution of LP in the population, it's really skewed towards the null. So it means that there's a lot of patient. Most individuals have very low levels of LP. And there's some individuals, as we mentioned, 15 to 20% that have high LP levels. Now, in individuals of African ancestry, it's a more like a Gaussian distribution. So that's one of the reason why they have higher lp. Does that mean they have higher risk if they have higher lp? Not necessarily, because the risk is really proportionate to the link level.

So there's nobody within shouting distance of what I'm about to Say I believe, which is LP is hands down the most common hereditary driver of ascvd. Correct. I mean, FH wouldn't even get within the same zip code. When you think about genetic things that are driving atherosclerotic cardiovascular disease. Correct.

It is by far the most prevalent form of dyslipidemia. So you can argue that. That and we have to talk about penetrance as well. So the penetrance is the proportion of individuals with a certain genotype that will have the disease. So the penetrance is obviously not 100% right. So when I hear people say that, you know, LPA for the pharmaceutical industry is a market of 1.4 billion people, I say, well, hold on a second. It's not everyone that has a high LPA that will have an event. And we need to figure out what are the drivers of risk in patients with high lp. And we're starting to study that, and we see that there is some residual risk effect even in patients with high lpa. So we see that, for instance, if you have a high LPA but have lower CRP levels or lower inflammation, you might not have a risk that's as high as if you have high crp. So you can argue that residual inflammation is very important. But there need to be more studies on this, because one can make the case that while it might be the same for smoking or type 2 diabetes or any other cardiovascular risk factor that you can think of, but even then, even if LP is not fully penetrant, it is so common that it is by far the most important form of dyslipidemia that will explain a lot of cardiovascular events at the population level.

And what I find so tragic about that statement is the number of good physicians out there, really great doctors that are working hard taking care of patients, frontline physicians, family medicine physicians, internists who have no idea what it is. You know, you ask them about it and they look at you as though you've asked them something in a different language. I still struggle to understand that disconnect. Given its urgency, I wonder if that's a uniquely American phenomenon. Do you have any insight? I know you're not a clinician, but do you have an insight as to whether or not the literacy around this in Canada and Europe is higher?

I don't have any reasons to believe that the literacy in Canada or Europe is higher than it is in America.

Even with your guidelines being more forward leaning.

Oh yeah. But these guidelines are new and it will take a lot of time before they implement it. Sometimes it takes a full decade before it's transmitted to younger generation of physician and people actually talk about it. So that's one of the reasons I'm so glad that we get to do this podcast. Hopefully this will raise awareness for the physicians out there that didn't have any information about lp. And, you know, you can't blame them because, well, it's obviously in the guidelines, but, you know, not all physicians read all the lipids guidelines. There's so many guidelines out there that you can't blame them for that. But I mean, that's why we have to do more education to physicians. And I think one of the reason that people are reluctant to measure LP is that because there's no treatment, any medical procedure that you do, even if it's asking for a measurement of any labs that you can mention, it has benefits, but it also has consequences. You don't want to stress anybody saying, hey, you have this risk factor, it's super important and you don't want to do like an over diagnosis and over treatment. I used to think that a lot, but now we're in the age of shared decision making. We can communicate the correct information to patient, tell them what we know. And even though there's no specific therapy for high lp, it doesn't mean you can't do anything. There's trial data showing that if you prescribe, for instance, a statin, and if you lower LDL cholesterol levels in patients that have some risk factors for cardiovascular disease, you'll reduce their risk of events. So in patients with high lp, lpa, you need to manage ldl, you need to manage lp, you need to manage lifestyle, smoking cessation and et cetera. And we've actually shown that. I've been working for more than 15 years with investigators in Amsterdam and Cambridge on the EPIC Norfolk study. So the EPIC Norfolk Study is the European Prospective investigation into cancer and nutrition. And they have LP measurement in 18,000 individuals. Individuals. And we've looked in that population at the effect of LP on the risk of events. But according to what the American Heart association calls the Life simple seven, so smoking, having a healthy diet, being physically active, having low body weight, LDL cholesterol, no diabetes and blood pressure, that's on target. And if you look at patients that have high LP and that, that manage all of these risk factors, it's observational study, of course, but if you consider it a causal relationship, you could reduce your risk by 2/3. So that's not trivial. So that's one reason why we should measure lp if it's just to target the other risk factors, we'll have a lot of benefits in terms of prevention of cardiovascular diseases at the population level.

And I think this is another great example of the parallel with ApoE, the gene end at the type. As recently as even a couple of years ago, I would have enormous arguments with physicians about patients that we were co managing. Right. So this would be a patient who has both of us as their physician. And the patient would say, look, I want to have my APOE genotype measured. I would say, I completely concur. The other physician would say that's an absolutely horrible idea. What good comes of that if they discover that they have an APOE4 gene and their risk is high, higher. All you've done is create anxiety, to which I would argue perhaps in some individuals. Sure. And that's why it should be something that is done with consent. But that assumption assumes you can do nothing about it. And while you can't change the gene, the evidence that you can modify behaviors that will lower the risk is enormous. Now, in the case of apoe, it's even more complicated because we now know what we didn't know a few years ago, which is there are so many other genes that will either amplify or attenuate the risk of APOE. So frankly, today, knowing that you're APOE 4 positive, in my opinion, carries much less information than it once did. So I want to ask you about something parallel with Lp. I've had patients who have had modest Lp, meaning 150, 125 nanomole per liter, 60 milligram per deciliter, who have had the most devastating ASCVD that you can shake a stick at. I mean, six vessel disease calcium scores of 2000. I mean, these are people who are having coronary artery bypass surgery in their 50s and their LP is, you know, a little elevated. And by the way, way their LDL and APOB were not through the roof. They're not smokers, they're not hypertensive, they're not type 2 diabetic, et cetera. Hard to explain those ones. Similarly, I've had patients whose family histories do not suggest advanced or premature ASCVD. And I told you about one of them earlier, 690 nanomole per liter LP. Now, this person had a zero calcium score. Admittedly they were in their 40s. So, you know, a calcium score of zero in your 40s doesn't generally tell you anything, but it at least tells you that this person isn't having advanced atherosclerosis Their family history is very uninspiring, and at least one of their parents had to have an elevated level. Grandparents, nothing. And I scratch my head, and I think, why is it that this person seems somehow somewhat immune from their very elevated lp, whereas this other person, who's elevated but not through the roof, is ravaged by it?

Well, you're describing my next grand proposal, Peter. So this is exactly what we're trying to study. I alluded earlier to the penetrance of high lp, and that's exactly what you're referring to.

Oh, I misunderstood, Benoit. I thought you were referring to the penetrance in terms of the expression of. Of the protein. You were referring to the penetrance of the disease.

Yes, exactly. Exactly. But, you know, we can say a lot about that. In our lab, we isolated the LP particle from the blood of donors and patients with aortic valve stenosis. So the reason being that. Well, we're going to study those particles because those patients, they were matched for age, sex, statin therapy, smoking, et cetera. So they're the same people demographically speaking, but one of them has a disease and the other one doesn't. They all have high LP and they were matched for LP levels. So we thought, well, maybe there's something happening in the particle. Maybe they have more oxidized phospholipids, maybe they have different proteins. So we've studied that, and we realized that these patients might have more cell adhesion molecules that are transported by Lp, which make them more, quote, unquote, sticky to endothelial cells, or fibrin clots, or maybe even macrophages, because patients with high LPA also have activated macrophages, which can penetrate much more easier in the vessel wall. There's more apoptosis in the macrophages. There's more cytokine production, like IL6, illustration, phthalate, etc. So there might be something that's different in the LP particle. That's just an hypothesis. This was a study of. I think there were 20 patients in each study arm, because it's not easy to remove LP from the blood and have it in a sufficient quantity that you can actually do proteomics on it. So this is. It took a PhD student of mine at least one year just to recruit the patients and isolate their LP, and they were 40 of them.

And that's just because the electrophoresis is complicated. Is it getting it out of the body that's complicated, or isolating it once it's ex vivo?

Well, once it's ex vivo, you have to isolate it. It's not difficult to isolate it because you need to do ultracentrifugation, but it has the same size as LDL and the same density as hdl. So you have to do chromatography columns to just basically separate it from LDL particles and also HDL particles. So you need to do a size exclusion chromatograph and an affinity based chromatography. So it took a lot of time just to set up that technique. And we worked with a great colleague of mine, Marla Skoshinsky, who's at the Robarts Research Institute in London, Ontario. And she's been doing this for ages, but she helped us doing that. And we're actually, I think, one of the first to actually isolate LP from the blood of patients. So that might be an explanation for this different expression of the disease in people that have have all high lp, but some that are lower than others. So that's just a hypothesis. You need to look at other risk factors. Maybe there's another gene that's out there that might code for a receptor of ldl. There's labs that are really devoted to finding other genes aside LP that might explain this.

And the GWAS hasn't identified any, because that would be your first tool before I'd go looking for that gene or that receptor. Rather I would would be trying to just find out what the association is.

Right, absolutely. And those studies have been done. Probably the best GWAS on LP levels was published I think last year by the group of George Tanasulis and Ed McGill in Montreal and James Engert. What they showed is that, well, obviously the biggest hit was at the LP locus, and we had known this for a while, that APOE actually also regulates high LP levels. So that's another reason why is there.

Some concordance with APOE and lp?

Yeah, so APOE allele that will rise. The risk of heart attacks will also rise LP levels. So you have that you have the CTP gene. And then we haven't talked about the LP lowering effect of CTP inhibitors, which is actually higher than what you can get with niacin therapy. So some have suggested that the quote, unquote benefits of CTP inhibition might be due to a certain extent to high LP levels. But the problem with niacin trials and CETP trials is that they weren't done particularly in patients with high lp. So I guess we'll never know.

So they're probably underpowered, at least when it comes to trying to understand that.

Yeah, because you would have to recruit only patients that have high LPA, which would mean to get rid of 80% of the trial population. So these trials will be very hard to do. And when you look at the other genes, you have CTP, and you also have have APOH, which is on another chromosome, and APOH codes for beta 2 glycoproteins. And that protein might actually influence the presence of oxidized phospholipids on apo. So that might be interesting. And I can't think of a study that have tried to look at that locus with high LPA to see if it has a modulatory effect on outcomes, but that would be a very interesting study to do. So these are the genes that I can think of, interestingly, the LDL receptor and also the most probably important regulator of LDL receptor, PCSK9. They did not pop up in that GWAS, which was a little bit surprising to me, given the effect of PCSK9 inhibitors on LP8.

Before we get to that, I want to go back to and really make sure we flush out this oxidized phospholipid plasminogen and basically the atherogenicity of this particle. Is it clear that LPs enter the subendothelial space as LDLs do, or is that unclear?

There's not as much research that's been done on lp, but if you look at postmortem studies, you can see LP in atherosclerotic plaques, and you can certainly see it on aortic valves. Aortic valve are much more easier to get than atherosclerotic plaques. You can remove the valve and you can study it under the microscope. So there's good evidence that the LP can actually penetrate there. Usually what they do is they will bind to clots that are in the region of the AT aroma, and that's one of the reasons why they might also be present there. And they can also send their oxidized phospholipid to different receptors, because we don't really know what is the receptor for LP in those tissues. So at the surface of macrophages, there are scavenger receptors, toll like receptors, CD36, that might bind LP. They bind a bunch of things, but they also might bind npa, which will ensure that LP gets trapped in the macrophages and myeloperoxidase. Lpa. Sorry, sorry. I meant lpa. Yeah.

Oh, lpa. Okay, okay. If I'm hearing you correctly, Benoit, it would almost suggest that LP plays less of a role in the initiation of atherosclerosis, which is really initiated by the monocyte becoming the macrophage in the subendothelial space and engulfing the oxidized LDL to become that foam cell that's really the initiating trigger. You're saying LP might not be playing a role in that? Or maybe it is. I want to make sure I'm not misquoting you. But where it really lights things on fire is once you already have a. A plaque, that's where the ability to form a clot goes up, potentially. If you say it has more VCAMs on it, it's attracting even more macrophages to the site of injury. Am I capturing what you're saying correctly?

Absolutely. I think it's actually both. So the macrophages of patients with high LP are already activated, and they will get. As soon as there's some endothelial dysfunction, they'll get the. There. They might even cause endothelial dysfunction. So L.P. is probably a main driver before the onset of any discernible plaque. But it also has this double whammy where it initiates the disease, but it also is associated with the progression of the disease. And we see it in. For instance, I talked to you a little bit earlier about the PET imaging with sodium fluoride. Fluoride. These studies have also been done by Eric Strus in Amsterdam. What they showed is that if you don't use sodium fluoride, but you use fdg, so fluorodeoxyglucose, which is basically a marker of macrophage activation. And if you looked at the carotids and also the aorta of patients that have no disease, but that are separated on the basis of whether or not they have high lp, you'll see a lot of light in patients with high lpa. So that tells you that it's also associated with inflammation with the inflammatory plaque, even in patients that don't have established disease. So that's one of the reasons why this kind of particle is so dangerous.

And the association is obviously very strong for ASCVD and aortic stenosis. How high is the association? Specifically for cerebrovascular disease?

It's clearly not as high. So there's obviously a signal. If I would have to rank those atherosclerotic cardiovascular disease, the first one will be aortic valve stenosis. It's obviously less prevalent than MI or stroke, but.

But there are fewer contributing factors beyond LP the way you have apartment ob.

Exactly. So the relative risk is actually higher. The Absolute risk is lower because there's not that many people that have that might be 2% of the population age above 60. But if you look at top quintile versus lower quintile, the biggest risk is with aortic valve stenosis. After that, it depends on the study. Sometimes it's myocardial infarction, sometimes it's peripheral artery disease, and we haven't talked about that. But LP is very strongly associated with PAD as well. So it's aortic valve stenosis, PAD and mi, then ischemic stroke. And it's important to make the distinction between hemorrhagic and ischemic stroke because LP is only associated with ischemic stroke. It's also associated with chronic kidney disease.

Oh, so that's it really. It's only associated with aortic stenosis, mis, peripheral vascular disease, ischemic cerebral strokes and kidney disease. But aside from that it really does nothing.

Yeah, there was some literature maybe 15 or 20 years ago on deep vein thrombosis and L.P. and there has been new studies published on that. There's been genome wide association studies and we really don't see a signal for, for LP being associated with deep vein thrombosis too. So that was part of the conversation for a while, but now I think it's pretty clear that it's really more closely associated with atherosclerotic cardiovascular diseases and less with thrombolic events.

We do have an assay, I believe, for OxLDL, correct?

Yeah.

Is that assay picking up the oxidized phospholipid of LP included in, in that calculation?

Absolutely not.

So totally different.

Yeah, well, there is actually an assay to measure oxidized phospholipids on APOB containing lipoproteins.

Is that Sam Tamikis assay?

Exactly. So they have an assay that measures OXPLs on APOB, including LP, of course, and also OXPLs on apolipoprotein lips. But the correlation coefficient between these two is very high. And the correlation between LP levels and OXPL on APOB is also very high. So of course that can provide some information. And obviously Sam Tsimikis has measured OXPL on APOB in all of the cohorts that he could put his hands on. And it's a good predictor of, of all of the diseases that we've just mentioned.

But is it a predictor beyond the level and the number of LP particles?

No, I don't think there's good evidence to suggest that it's A better marker or it predicts above and beyond lp. I think we should advise people to measure lp. That would be a gigantic step. And then we can see if at some point we have convincing evidence that, you know, measuring oxidized phospholipid will bring an added value. But I haven't seen much data that.

Suggests I stopped measuring OX LDL because I didn't see any benefit to it over apob. So it sounds like it's potentially the same thing here. And of course, you'd hope that it would have benefit above and beyond so that it would help you stratify risk further. But interesting that it does not. Very complicated to know what to make of this. These oxidized phospholipid tails that are sitting around there wreaking havoc and potentially also forming part of this explanation for the differential expression of the disease.

Yeah, and it's the same for LDL as well. So the LDL particles, they get oxidized. They also have oxidized phospholipids. And that's one of the reasons why LDL particle cause atherosclerotic cardiovascular disease. But the measuring them in the plasma, it will not tell you how many oxidized LDL particles you have in your plaques. So that's why we need to stick with APOB and lpa, because you'll get a sense of all of the lipoproteins that cause atherosclerotic cardiovascular diseases.

So you alluded earlier to a PCSK9 protein, which we'll talk about, tell people, before we get into the drug, tell people about the PCSK9 protein, how it works, what its relationship is to the LDL receptor.

Absolutely. So PCSK9, it means proprotein convertase subtilizin kexin type 9. It was discovered in 2003 by a collaboration between Nabil Seda, who is at Montreal, and Catherine Boileau, who is in France. They had identified this family in France that had familial hypercholesterolemia, but they couldn't find a mutation in the LDL receptor gene that explained the familial hypercholesterolemia.

By the way, before you get into this, I just want to say this is one of my absolute favorite stories in all of medicine, certainly in the modern era of medicine, if you think the last 20, 30 years, this story is remarkable. So please indulge us.

Thanks for doing me the honor. So they had identified this family that had FH without a mutation in the LDL receptor. And the paper was published in nature genetics in 2003. So you can think that they had been working on this for a few years. So that was probably at the time where the human genome was being sequenced. So that was during the days of. So that was pre genome wide association studies and whole genome sequencing where you were doing linkage analyses with satellite DNA. And yeah, so I was an undergrad at that time. I was learning these techniques weeks and I wasn't in the lipids field. So I heard that story after. But what they found is that they were able to map the gene in that family to a protein that was at the time called NARC one. So they didn't know that it was a proprotein convertase. So when they identified that family in France, they partnered up with Nabil Seda, who's a world renowned scientist on proprotein convertases, and, and they mapped it to Narc1, which eventually became PCSK9. So the way PCSK9 works is that it's a regulator of the LDL receptor. So when the cells make an LDL receptor, it will also make PCSK9. Now PCSK9 can bind to the LDL receptor. That can happen inside the cell. And when that happens, the LDL receptor gets degraded in the lysosome. That can also happen extracellularly when the LDL receptor obviously in the hepatocyte gets stuck at the membrane, but PCSK9 gets secreted. So you can actually measure PCSK9 levels in the blood, but when it gets secreted, it can actually bind the LDL receptor. And when that happens, the LDL receptor cannot bind LDL particles. And I told you earlier that that LDL receptor density at the surface of hepatocyte is super important for LDL clearance. So because PCSK9 can be secreted. And by the time that they had realized that, they had shown that there were actually families in Montreal that had gain of function mutation in PCSK9, that had familial hypercholesterolemia. And then in 2006, the group of Helen Hobbs at UT Southwestern had shown that their there are common variants in PCSK9 that are associated with lower levels of PCSK9, lower levels of LDL and protection against cardiovascular diseases. Now, the pharmaceutical industry didn't need much more information to develop PCSK9 inhibitors. Right.

And I remember that paper like it was yesterday. I mean, it's hard to believe. It's been. What is that now, 16 years ago? Makes me feel old.

I remember I was a master's student at the time and we were witnessing that. And it was a very exciting time.

Let me just make sure we synthesize that for people, because it's such a big deal, right? So familial hypercholesterolemia is a very heterogeneous disease. There are at least 3,500 mutations that produce the exact same phenotype. Very, very elevated cholesterol. These are patients that have total cholesterol, typically north of 300 milligrams per deciliter. LDL cholesterol, by definition above 190 milligrams per deciliter of therapy, and often much higher. This disease is unequivocally linked to accelerated ASCVD. And what was discovered in 2003 was yet another gene that was associated with it. But what made it different is most of the genes, not all, but most of the genes associated with FH directly involved the LDL receptor. This one didn't seem to. Instead, they discovered that it was this protein that wreaks havoc on the LDL receptor when it's overexpressed, either by degrading the LDL receptor in the lysosome before it gets brought to the surface, or frankly, just interfering with the receptor when it's at the surface. Does PCSK9 also degrade LDL receptors or increase their turnover when they are at the surface of hepatocytes?

That's exactly what I was going to say. That's the third mechanism through which PCSK9 can influence LDL receptor density. Because what people don't really appreciate is that the LDL receptor, when it does its job of bringing LDL particles within the hepatocytes, gets recycled at the surface of the hepatocyte. And that can happen a hundred times in the life of the LDL receptor because it takes a lot of energy to the cell to produce the LDL receptor. And once a PCSK9 is bound to an LDL receptor, then it prevents its recycling. So the cell has to make more LDL receptor. And when it does that, because they're under genetic control of the SREBP2 transcription factor, so then the LDL receptor gets produced, and so is PCSK9. So you can have this vicious cycle.

And it's interesting to think that if the story had stopped there, it's not clear we'd be where we are today without the 2006 paper which showed, wow. As bad as that gain of function is, the loss of function is really amazing. Where now you found these people who had the opposite of FH, these are people who were basically missing their PCSK9. Not completely, just significantly underexpressed. And these were people that, as adults, walked around with neonate levels of LDL cholesterol. 10, 20, 30 milligrams per deciliter.

Yeah. So the most frequent variant that they look at was present in 2% of the population, and they saw very mild LDL reduction. So 20% reduction in LDL, but, you know, it's a lifelong reduction, right?

That's right. The Mr. Would still suggest that that's beneficial.

Exactly. But there has been some studies on, as you say, individuals that have virtually no LDL because they have no PCSK9. Really? And they don't have, of course, atherosclerotic cardiovascular disease, because you need LDL for that. But they're perfectly fit. You know, doesn't influence reproduction or hormones or anything.

Exactly. No increase in the risk of other diseases. So they have normal risk for cancer, Alzheimer's disease, every other disease, and they just don't have the risk of ASCVD. And their LDL cholesterol is 10, 20 milligrams per deciliter. Very important teaching point here, I think, for the listener, which is it might be tempting to say, how can someone with such little cholesterol in their plasma not have other problems when we understand the importance of cholesterol in creating lipid bilayers of cells and being a precursor to steroidal hormones. And I addressed this in a previous podcast, but I think it's worth stating this again. When you look at how much cholesterol is in the body and isolate that fraction which is in the plasma, even if you take that to zero, you've maybe reduced the total body pool of cholesterol by about 10%.

And there's still some cholesterol in the blood. Right. Because the liver will secrete very low density lipoproteins that will not necessarily be targeted by PCSK9. So you have to make the distinction.

And there's high density lipoprotein as well. So you still have a total cholesterol that might fall from 180 milligrams per deciliter. It might fall to 70 milligrams per deciliter or 60 milligrams per deciliter, but it's not zero. You're right. The point is you still have so much cholesterol in extra apob tissue. Right. The red blood cells, all of the tissue, the hepatocytes, et cetera.

We're seeing that also in the trials because, well, obviously the industry developed antibodies, monoclonal antibodies, against PCSK9. And these have been tested in two large cardiovascular outcomes trials. And they've shown that if you reduce LDH through these PCSK9 inhibitors, you get a reduction in cardiovascular events. And now in these trials, now these were all patients that were already treated with statins. And you add on to that a PCSK9 inhibitor and you really bring LDL cholesterol levels to the floor. And in postdoc analysis of these trials, you can see that the benefits was also correlated with the reduction in LDL levels. So patients that have the lowest LDL levels had the lowest risk of having a second event. I say second event because these trials were done in patients with stable CAD and also acute coronary syndrome. So it really tells us that we haven't identified yet the level of LDL that's so low that it's going to harm any physiological or disease. Process.

Process. It's such an important point. And again, I think you're referring to Fourier and Odyssey. I gotta tell you, this is one of those beautiful moments again where I was a little worried that Fourier and Odyssey were not going to be positive trials, especially Fourier, because you'll recall Fourier, the patients had an average starting LDL cholesterol in the 70s. I can't remember if it was 71 or 76.

I think the mean was 90. And they brought it back down to 30 milligrams per deciliter.

Well, was the mean 90? I thought the mean at the beginning was in the 70s, but I could be wrong.

There was not an entry level of ldl. Sometimes you see that in these kinds of trials you have to bring the LDL down to a certain level. But that was not the case. So they were just being treated with a standard of care, which is obviously a high intensity statin.

Yeah. So these were on very high doses of statins. So if they came in on a statin maximally and their LDL was 90, that's still very low. That still puts them at the 10th percentile. I thought it was 70, so that would have been at the 5th percentile. But the point is, when patients come in and they already have such a low LDL, you add a drug that lowers them to the 30s. But the trial was only five years. And my thought was, there's no way in five years that's not long enough to see a benefit when the patients are starting out so low. And that turned out to be wrong.

So the trial was supposed to last five years, but they saw a benefit at 2.2 years.

That's right. It was 2.2 and Odyssey was 2.4 years or something.

Exactly. So basically they stopped the trial when they knew they had an effect. But when the trial was published, that was in 2017, I think.

August of 15, I think.

Okay, well, that long? Okay. Well, there had been postdoc analyses from phase 3 trials that were very positive in the New England Journal. I don't know if you're referring to these papers, but anyway.

Sorry, yes, I'm referring to the FDA approval, which was on the earliest analysis, which was August of 15. Obviously subsequent analyses came after, but I believe at that point you had the 2.2 and the 2.4 year data, because basically Repatha and Proluent were approved within a month of each other, if my memory serves me correctly.

Yeah. Based on their LDL lowering and not necessarily on their effect of cardiovascular disease. So I was actually very surprised because in that trial, the relative risk reduction, if you compare PCSK9 with placebo, was only 50, 15%. So people were kind of expecting like a 20 plus percent reduction. And many people were kind of disappointed by that. But I mean, it happened over 2.2 years only, so that's what's underappreciated.

I can't remember if I wrote a blog post about this, and if I didn't, I'm sure I wrote it in an email to a friend and I hope I could find that email, but. And it was a friend of mine who worked at a hedge fund. Yeah. So it must have been an email. I don't think I wrote a blog post. He said, because you remember Amgen's price, share price declined with those results. I think it was because they didn't hit the relative risk reduction. It was so modest. And I said to him, that tells me Wall street doesn't understand atherosclerosis. If you can hit a 15% relative risk reduction, which ultimately turned into a bigger risk reduction in 2.2 years on a group of patients who show up on the maximum dose of a statin whose LDL is already at the 10th percentile. You've changed the field of cardiovascular medicine.

I completely agree. And I remember thinking this, that if they really wanted to make a trial to increase their stock price, they would have made it to the full four years. Right. Because then you would have seen the biggest increase. Because if you look at the Kaplan Meier curve, they're still going in opposite direction. They haven't stabilized. And I talked earlier about the cholesterol treatment trial S curve, the data from the Fourier and Odyssey trial, they fall exactly on the same curve where you're looking at achieved APOB levels and reduction in event. It's right there at the lower end of the curve, of course, because that's a trial in which they saw the biggest reduction in LDL apob.

So let's go back and close the loop on one thing before we now talk about PCSK9 and Lp. So you've explained now why a PCSK9 inhibitor, the drugs we're talking about, are so effective in lowering apob, because they're basically mimicking the most extreme loss of function of this gene. You're taking away that protein that does those three things to reduce LDL clearance. Why is it remind us that statins don't lower lp? You would think, well, we know why statins get the LDL receptor to be more dense. That should do it. So the obvious explanation here is LDL receptors don't clear lp. But why is that? Isn't an LP just an LDL with a little extra thing on it? Why is that causing so much difficulty for the statin?

I told you earlier that LP levels were determined by their rate of production. And one of the players that was an unanticipated player in LPA Apoa production is actually PCSK9. Because if you incubate liver cells with PCSK9, you'll see the expression of APOA going up. And in lipoprotein turnover study studies, you also see that. So if you treat people with PCSK9 inhibitor, you will actually see a reduction in the production rate of apoa. And there was a nice study that's a bit complex to fully appreciate by Gerald Watts, who's in Perth, Australia, he's shown this, but he also showed in a second group that if you treat patients with a PCSK9 inhibitor inhibitor and the statin, you see, and that's probably where the LDL receptor presence gets maximized at the surface of the liver cells. You can actually see clearance or increment in the fractional catabolic rate of lp. So there's still so much that we don't know in this area. And it's not totally clear why we see this difference of PCSK9 inhibitors. That's depending on whether or not you're treated with a certain statin.

And I think all comers, we see that a PCSK9 inhibitor is lowering LP by about 30% is the. On average.

Yeah. And so the average is probably between 25 and 30% in all comers.

But the variability is enormous.

Exactly. The Variability is very important. And it's another example where we need to study patients that have high lpa, because these are the patients that we want to provide an end answer to. And there's only been one trial that had tested the effect of a PCSK9 inhibitor in patients with Lp. There had been sub analyses in Fourier and Odyssey Outcomes. And when you look at that trial, it's called the Anichko trials, and all these postdoc analyses of randomized controlled trials of PCSK9 inhibitors, you see that in patients with high LPA, the reduction, reduction is approximately 15%. So it's not spectacular. And in the Anschko trial, what they did is that they've looked at arterial wall inflammation using fluorodeoxyglucose. This is a trial run by Zai Fayed at Mount Sinai in New York and Eric Strus in Amsterdam. They showed that even though you reduce LDL by, I don't know know what percentage, but it was a spectacular reduction in LDL, very small reduction in LP of 15%, you don't see any effect on arterial wall inflammation. So that means that, you know there's an important residual risk that's associated with LP, because if you lower LDL with PCSK9 inhibitors, you know, there's no outcomes data, although they did link LP with recurrent cardiovascular disease. And these trials, you see that the pro inflammatory effect of LP on the vasculature still remains. So we're going to have to go after LP even in patients that have very low levels of ldl.

There's no doubt about that is one interpretation of the fact that PCSK9 inhibitors can lower LP by 30%. But that might not be sufficient to ameliorate the LP risk specifically is that it's just simply not enough. It gets back to what you said earlier. You're going to have to eliminate LP and it becomes a bit more of a step function than the gradient we see with apob.

I don't know if we need to eliminate lp, but we need to take a higher LPA level and bring it down to a lower level.

Yeah. So that brings us to where we are today. Right, so what's the state of the art today in 2022 with my patients who have elevated LP, I take a two prong effect when it comes to lipid management. Obviously, there's many things we're doing outside of lipid management. The first is absolutely eradicating apob. So we're very aggressive on this because it's very clear that you can do this safely and effectively, we target an apob of about 30 to 40 milligrams per deciliter. So we target an APOB at what we would call a physiologic level. So the level that a child would have. It's clear that a child can have an APOB of 30 and have no problems with development, which is the most cholesterol demanding period of their life. So there's absolutely no reason that we shouldn't be able to take an adult there without side effects, meaning provided we can do it without side effects from the medications. But the second thing we do is we're very liberal in the use of PCSK9 inhibitors because even though we don't know the answer yet, our belief is even if it whacks at 30%, which is about what we see, we see on average about a 30% reduction LP, it's worth it until we get to antisense oligonucleotides. So let's talk about antisense oligonucleotides. What are they?

Before we get into that, I'll tell you that I do the same thing. I mean, I'm going to turn 40 this year. So I decided to have a lipid check and, and have my LPA remeasured and it's very high, it's at 200 nanomolars. I knew that because I had my genotype done with direct to consumer company and they let you look at your own data so they'd send you all of your SNP information. So I went and look at my favorite SNP in LPA and I was a carrier of one of the most famous variants in lpa. So, and that's exactly what I decided to do. So my LDL was a bit higher than average, my LPA was high. So I just started to take a statin and of course I, I've been on close to vegetarian diet for more than three years. I, I'm physically active, but you know, at some point you have to look at your labs and say, well, I need to do more. So even I started the taking a statin even though I'm not 40 yet, because I see those studies and I see the importance of going after LDL very early and very aggressively. Now I'm not on a super high dose, I need to check it after three months, but if it doesn't go down, I'll increase the dose. And that's, I think, what people who have high LP should do. So coming down to the antisense oligonucleotides against lp. This is a very exciting time for LP research. So the probably the first horse in the race will be the compound by Ionis Pharmacy. So it is an antisense oligonucleotide against the LPA gene. Well, all of them will be. And the second one is, and they just released some data on this in the, in Nature Medicine a couple of months ago. And it's called Olpaciran. It's not an oligonucleotide, it's an Sirna against lpa. It's the compound by Amgen. And I believe they'll need to do a phase three trial, but with the first one with the Ionis compound.

And Ionis is the company that used to be called isis, like before it became horrible to have the name isis. It's a San Diego based company. I remember I used to swim with a guy who worked there. His duffel bag, which was from Works, had ISIS on it. And I was like, yeah, you're probably going to want to change that.

Yeah, you can't board a plane with that. So, yeah. So they already have phase two data that's been published in 2020 in patients with atherosclerotic cardiovascular disease, a very nice dose ascending study. And they've shown that in the dose that they're going to use in their trial, which is a monthly injection, you can get mean reduction of Lp levels of 80% even in patients with high Lp. So that's very encouraging because this is what we're going to need to prevent heart attacks and obviously to have successful cardiovascular outcomes trial. And in that study they also showed that 90% of patients who were treated on that dose had LP levels below 50 milligrams per deciliter. So it's very potent. It's a second generation antisense oligonucleotide. And they have launched a trial, a cardiovascular outcomes trial trial that's called Horizon. And they're recruiting a little under 8,000 patients with stable cardiovascular diseases and they will study the effect of LP in their antisense oligonucleotides in the prevention of major atherosclerotic cardiovascular events.

And is this a secondary prevention trial?

It is a secondary prevention trial trial. So this is where you have to take the patients that have the highest risk to have a positive trial. To my knowledge, there's no plan for a trial in primary prevention, but that will eventually have to come.

That will be the off label use. Do you have a sense of how far they are in their enrollment? Because this trial and maybe it's just because of how emotionally invested I am in this. I have a normal lp, but it's just I think I take care of enough patients that don't. This trial feels to me like the molasses rolling uphill in January trial. And as a Quebecois, you can appreciate the speed with which molasses will roll uphill in January. What is taking so long? This is a trial that feels like it's a year away from being completed every year for the past seven years.

Yeah. Well, first of all, being an investigator in a research center and at times of COVID was very, very difficult to bring people into the hospital for an exploratory trial. So I don't know for that specific trial, but I can tell you for any lab or any clinical research facility, any patient that were recruited, and especially in our hospital, we're the COVID hospital for the entire region. So people don't want to come here during pandemic. So I'm thinking that this is probably part of the explanation. So we'll have the result of that trial probably in 2025. Because I told you earlier that trial is going to be 8,000 patients. When I saw that, I thought, well, this is not enough. I mean, they need to do a big trial. And this is kind of risky to do a trial in only 8,000 patients. But the way I understand it is that they're going to use the full four years of their treatment period. So even though you have less patients and for instance, Fourier or Odyssey outcomes that have north of 15,000, so they're recruiting half for the roughly the same population, so they're going to study it for a longer period. So that might also explain why it's not going to be published anytime soon. And we need to be patient. And I'm really looking forward to seeing the results of that trial because they hold the fate of the entire field in their hands. So really looking forward, especially for the patients, really looking forward to seeing the results of that trial. And I hope that there will be other companies. I know there's three companies that have antisense oligonucleotides against lp. So you have Ionis, which is partnering with Novartis for the trial. Amgen has one. And there's also another Sirna company called Silence Therapy Therapeutics that have an LP inhibitor. I don't think they have released their phase one study yet, but I think we'll see more and more of these companies because there's still money to make. I think in that area of residual cardiovascular risk because we can target LDL as low as we want, and there's still a underappreciated amount of residual risk that's associated with different things with triglycerides, inflammation. But the first thing that comes to mind to be me is the risk associated with high lp.

It's an amazing decade we're in. If in fact this study is published in 2025, you'll have exactly a decade between the approval of PCSK9 inhibitors and potentially the approval of this antisense oligonucleotide for lp. And you could argue that those two things will have an outsized effect on human health. So, Benoit, I want to thank you very much for spending all this time with me today and by extension with all of our listeners. This is such an important topic that I think of this almost as a public service announcement. If you're listening to this podcast, there's at least a 10 and maybe a 20% chance that your LP is elevated. You really need to demand that your physician checks this level. We think that the milligram per deciliter mass measurement is probably sufficient. And if you're elevated on that level, at least at this moment in time, the best thing that we can do is keep APOB as low as possible and manage all of the other manageable risk factors, hypertension, smoking, insulin resistance, et cetera, that traffic with atherosclerotic cardiovascular disease. The other thing I think we can at least I would be comfortable recommending. I know you're not a physician, so you probably wouldn't be comfortable making a recommendation. I would also insist that you at least once have an echocardiogram to look for even the earliest signs of aortic stenosis, as it is imminently more treatable and the outcomes are better if it is addressed earlier.

Well, thank you Peter, for having me. And thank you for raising awareness on health. PA it was a real pleasure talking to you today.

Yeah, the pleasure was mine. Thanks, Benoit. Thank you for listening to this week's episode of the Drive. If you're interested in diving deeper into any topics we discuss, we've created a membership program that allows us to bring you more in depth exclusive content. Content without relying on paid ads. It's our goal to ensure members get back much more than the price of the subscription. Now, to that end, membership benefits include a bunch of things. One totally kick ass comprehensive podcast show notes that detail every topic, paper, person, thing we discuss on each episode. The word on the street is nobody's show notes rival these monthly AMA episodes or Ask Me Anything Episodes Hearing these episodes completely Access to our private podcast feed that allows you to hear everything without having to listen to spiels like this the Qualys, which are a super short podcast that we release every Tuesday through Friday highlighting the best questions, topics and tactics discussed on previous episodes of the Drive. This is a great way to catch up on previous episodes without having to go back and necessarily listen to everyone. Steep discounts on products that I believe but for which I'm not getting paid to endorse and a whole bunch of other benefits that we continue to trickle in as time goes on. If you want to learn more and access these member only benefits, you can head over to Peterattiamd.com forward/subscribe. You can find me on Twitter, Instagram and Facebook, all with the ID Peteratti md. You can also leave us a review on Apple Podcasts or whatever podcast player you listen on this podcast. Podcast is for general informational purposes only and does not constitute the practice of medicine, nursing or other professional healthcare services, including the giving of medical advice. No doctor patient relationship is formed. The use of this information and the materials linked to this podcast is at the user's own risk. The content on this podcast is not intended to be a substitute for professional medical advice, diagnosis or treatment. Users should not disregard or delay in obtaining medical advice from any medical condition they have, and they should seek the assistance of their healthcare professionals for any such conditions. Finally, I take conflicts of interest very seriously. For all of my disclosures and the companies I invest in or Advise, please visit PeterAttiamD.com about where I keep an up to date and active list of such companies.