The Gut-Brain Axis

Our gastrointestinal (GI) tract has a complex nervous system called the enteric nervous system (ENS), which sends signals to the brain via connecting nerves. This ‘gut-brain axis’ informs the brain about the food that is consumed, pathogens and toxins that have been ingested, and the status of the gut microbiome. When the brain receives these signals, it sends messages throughout the body to prepare various organs to deal with what has just been ingested. Some of those signals entrain the circadian rhythms controlled by the brain, regulate sleep-wake cycles, adjust body temperature, gastric emptying, digestion and peristalsis.

The Gut & Neurodegeneration

Over the past few years, groundbreaking research has shown that a protein called alpha synuclein (αS) accumulates within the nerves of the intestine of people who develop Parkinson’s Disease (PD). This protein is a normal component of the ENS and its exact function is unknown. In patients who develop PD, the ENS is overwhelmed by these αS deposits, which cause damage and destruction within the nerve.

Some gene mutations predispose people to PD, by either leading to overproduction of αS, production of αS variants that have a tendency to aggregate, or problems with the cellular system that normally helps the cell eliminate surplus αS. As the disease progresses, αS deposits spread from the nerves of the GI tract towards the brain, first damaging nerve cells within the brainstem important for the function of the autonomic nervous system, and then moving upward into the centers that control mobility and muscular control.

The nerves that relay information from the GI tract to the brain become ‘clogged’ with αS aggregates and like ‘damaged wires’ fail to relay important information required for the normal functioning of the body. In other words, PD begins in the gut and travels up to the brain via the vagus nerve and the sympathetic chain.