A NIH-funded researcher explains how Parkinson's disease often starts in the gut, not the brain. About 80% of Parkinson's patients have GI issues like constipation years before tremors appear. The protein alpha-synuclein misfolds in the gut and spreads to the brain via the vagus nerve, killing dopamine neurons.
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We now have really good evidence that Parkinson's disease can start in the gut. Really? Absolutely. And this is exactly what my lab, which is funded by the National Institutes of Health, studies. So when I started seeing Parkinson's patients, I was really struck by how many of them would say things like, if I could trade away any one of my symptoms, it wouldn't be the tremors, it wouldn't be the trouble walking, it would be the constipation. And as it turns out, 80% of people with Parkinson's disease have GI symptoms, whether that's trouble swallowing, nausea, or trouble having a bowel movement. And when I started to dig deeper, as it turns out, so many of these GI symptoms start years, if not decades, before they get diagnosed with Parkinson's, before the tremors begin. And what's interesting is that this is not a new idea that the gut and the brain can be connected in Parkinson's disease. When James Parkinson, first described those series of patients in 1817, he wrote how many patients he saw had severe constipation. And it was just unfathomably bad. And he seemed to understand there was a link there. But for the next roughly 200 years, we focused a lot on how Parkinson's disease begins in the brain, in the head. But as it turns out, there's probably two different kinds of Parkinson's disease, one that begins in the head one that begins in the body and in the gut. And what happens in Parkinson's disease is that there's this protein called alpha-synuclein. Alpha-synuclein is a protein that can misfold. When it misfolds, it starts to cause other alpha-synuclein proteins to misfold with it, and they can kind of propagate and move. And we think that this misfolded alpha-synuclein protein is what's responsible for the death of the dopamine neurons in the brain that gives people the tremors and the difficulty moving. What's interesting is that when you look at autopsies of people who have had Parkinson's disease, their guts are riddled with that misfolded alpha-synuclein protein, and it's often there before it reaches the brain. So the idea is that alpha-synuclein may start to misfold somewhere here, somewhere in your gut, in your stomach, and then it starts to propagate, travel up the vagus nerve. Oh, so it actually invades from the gut. That's right. Invades from the gut, moves up the vagus nerve, and eventually reaches the brain.
