Neurodegeneration.

What is neurodegeneration?

Neurodegeneration is the progressive loss of structure or function of neurons. Many neurodegenerative diseases—such as multiple sclerosis, Parkinson's disease, and  Alzheimer's disease occur as a result of neurodegenerative processes. Neurodegeneration can be had at many different levels of neuronal circuitry, ranging from molecular to systemic. 

A healthy brain is maintained by the blood-brain barrier. The blood brain barrier protects the sensitive brain tissue from toxins present in blood and lymphatic circulation. This ensures a pristine environment for the sensitive brain tissue and its executive functions.

Many things can cause increased permeability of the blood brain barrier, leading to neuroinflammation and damaged neurons.

In 2008, the National Institute of Health’s Human Microbiome Project began to spotlight how important the microbial environment of the gut is. The brain affects the microbiome in the gut, and the microbiome affects the brain through the gut-brain axis. The microbiome is responsible for everything from digestion, nutrient absorption, blood sugar balance, detoxification, and the immune response. The microbiome produces short-chain fatty acids, amino acids, neurotransmitters, and vitamins- all building blocks for every essential function of the body. When there is a variety of beneficial species, they work together to provide a powerful barrier between toxins and foreign proteins within the intestines and the rest of the body and play a significant role in disease prevention and/or recovery.

When there is a reduction in microbial diversity and a loss of beneficial bacteria caused by any number of factors, disease susceptibility is increased. The tight junctions between the cells of the gut barrier break down and become permeable creating intestinal hyperpermeability or “leaky gut”. Food proteins and endotoxins can pass through a leaky gut into the blood where they activate an immune response. This immune response causes a release of inflammatory chemicals called cytokines, which can lead to brain inflammation and neurodegenerative diseases. This systemic inflammation may target the brain, increasing the permeability of the blood brain barrier causing leaky brain. Once the BBB is breached, the brain’s immune cells are activated, which causes one of the foundations of all brain injury- neuroinflammation.

Additionally, the gut-brain communication travels through the vagus nerve, which senses changes in the microbiome and sends cytokines and other inflammatory chemicals to the brain. The conversation between the gut and brain is incredibly important in the control of neuroinflammation, which is a crucial factor in neurodegenerative conditions.

Chronic leaky gut is also linked to hippocampal neurogenesis, which is the brain’s ability to create new neurons. Decreased hippocampal neurogenesis secondary to neuroinflammation also damages mitochondrial DNA, detrimentally affecting energy production in brain cells. Together, neuroinflammation and mitochondrial dysfunction further damage neurons by increasing production of reactive oxygen species (ROS) and are thought to play a fundamental role in the pathogenesis of neurological disorders such as MS and Parkinson’s. 

Neurogenesis, the process by which new neurons are produced by neural stem cells, healthy mitochondrial function, and the production of BDNF, (brain-derived neurotrophic factor) are all needed to keep the brain healthy. BDNF is a growth factor that consolidates the connections between neurons and helps to wire them together so they fire together reliably. This is all linked to a healthy gut. Through using the approach of “heal the gut, heal the brain,” there are many powerful steps to take to restore microbiome diversity. Diet, exercise, stress resiliency are all good places to start.

*excerpts from Dr. Teri Jaklin’s article ‘Solving the Brain Puzzle’