Your gut has its own neural network. Called the enteric nervous system, it controls digestion and has as many neurons as the spinal cord.
Parkinson’s disease is a brain disorder that has been long associated with stomach upsets. These were often explained away as due to poor diet or stress, but it seems increasingly likely that the disease may also be affecting the neurons in the digestive system.
It was originally thought just to destroy dopamine neurons in a deep brain structure called the nigrostriatal pathway, an effect which causes the distinctive movement problems, but it has become clear that the disorder causes damage throughout the nervous system via the formation of protein clumps called Lewy bodies.
A new article in European Journal of Neuroscience suggests that Parkinson disease affects the enteric nervous system, which might tie together some curious findings in the medical literature that have remained unexplained for many years.
Stomach upsets, swallowing and digestion problems have long been associated with Parkinson’s but it has never really been clear why.
While we commonly think of it purely in mechanical terms, digestion is remarkably complex process and the enteric nervous system is involved in the careful regulation of the muscle ripples of the gut, secretion of digestive fluids and blood flow to aid absorption.
Damage to this system would cause exactly the sorts of problems that have been reported in Parkinson’s disease patients and this fits with some previous findings that have been ignored for many years.
Until recently, only one study had investigated whether the enteric nervous system was damaged in Parkinson’s patients. It found that large numbers of the gut’s dopamine neurons seemed to be missing in patients with the disorder.
The next study appeared more than ten years later, this time looking for protein clumps in the gut of deceased patients, and found evidence that not only were these tell-tale signs present, but that the distribution suggested that neurons in the gut may be the first to be damaged.
The author of this study, neuroscientist Heiko Braak now proposes the radical idea that while we know part of the risk for Parkinson’s is genetic, maybe an environmental trigger – a virus – could get into the nervous system via the stomach, eventually triggering the brain changes that lead to the debilitating tremors and movement problems.
Link to Parkinson’s and gut nervous system article summary.