In fight against Parkinson’s and other disorders, two-way connection may someday lead to a breakthrough.
For Jo Keefe, the trembling hands and trouble walking were bad, but it was the nausea that was truly debilitating.
“For two or three years, I was having nausea for several hours every day,” said Keefe, a retired lawyer living in New Hampshire who suffers from Parkinson’s disease. “I’d wake up in the morning feeling sick and I couldn’t make any plans at all. Fortunately, I was retired, but I wasn’t planning on this for my retirement.”
Parkinson’s is a neurodegenerative disorder affecting cells that control movement. Patients and the doctors who treat them have long known that severe gastrointestinal issues — nausea, abdominal pain, diarrhea, constipation — are a feature of the condition, in some cases preceding neurological dysfunction by decades. But in recent years research around the disease has started to point to a connection that is more than incidental. The gut, experts say, may be where Parkinson’s starts.
Such a model, if supported by future research, would revolutionize our understanding of the nation’s second most common neurodegenerative disorder, opening a path for specialists to help patients like Keefe before neurological symptoms appear. It would also have the potential to inform treatment of other neurodegenerative disorders, including some of the most devastating in human health.
“What if you were able to get your screening colonoscopy and be told there’s a sign that you’ll progress to Parkinson’s unless we intervene now. And wouldn’t it be wonderful if we had a way to intervene now?”
Trisha Pasricha, specialist in neurogastroenterology and director of clinical research at Beth Israel’s Institute for Gut-Brain Research
“Everyone’s goal is to find an early biomarker for Parkinson’s and our hope is that we can find one in the gut,” said Trisha Pasricha, a specialist in neurogastroenterology and director of clinical research at Beth Israel Deaconess Medical Center’s Institute for Gut-Brain Research. “What if you were able to get your screening colonoscopy and be told there’s a sign that you’ll progress to Parkinson’s unless we intervene now? And wouldn’t it be wonderful if we had a way to intervene now? There are many steps that need to happen, but that’s the goal.”
Central to Pasricha’s vision is the gut’s enteric nervous system, which contains as many neurons as the spinal cord and presides over digestive processes that function as the body’s intake department: proteins, carbohydrates, alcohol, drugs, fiber, agricultural pesticides, hormones given to livestock, chemicals used in food processing, bacteria, viruses, and on and on. The system processes signals about what we’ve consumed and how to respond: throw it back up or move it along; speed it up or slow it down.
Also key: a focus on the two-way nature of the gut-brain connection. Stress caused by the perception of potential danger can cause digestive ills, for example, while signals from the gut’s own nervous system, the enteric nervous system, can spur the brain into mobilizing the body via hunger, cravings, nausea, and pain.
“The enteric nervous system is this large network that runs throughout the gut,” Pasricha said. “It’s constantly signaling, influencing our mood, our wants, our needs. Some of the earliest animals had an enteric nervous system well before anyone developed a brain, well before anyone developed a central nervous system, because we all had to eat. It’s like the OG of our bodies.”