Functional Neurology: The Brain and the Gut Microbiome Connection

Approximately 100 trillion bacteria are found in the gastrointestinal (GI) tract or gut, including Bacteroides, Bifidobacterium, Faecalibacterium, and Ruminococcus, among many others. These microscopic organisms, known as the microbiome, help digest food, process nutrients, and produce immune molecules which helps heal injuries and fight inflammation. Surprisingly, however, the gut microbiome plays a much more fundamental role in the brain. 

Although the brain and the gastrointestinal tract seem to be two independent parts of the human body, they are actually connected through a series of biochemical communications between nerve cells and immune pathways, known as the gut-brain axis. Bacteria create neuroactive compounds in the gut, including up to 90 percent of all of our neurotransmitter serotonin, which ultimately helps control our mood. Moreover, the brain also sends signals to the digestive system, by way of instance, to stimulate or suppress digestion. In the article below, we will discuss the brain and the gut microbiome connection.

The Role of the Gut Microbiome in Brain Health

A healthy microbiome consists of a diverse variety of species that protects against having one specific community from dominating and causing trouble in our gut and brain. Changes in the microbiome are believed to be associated with inflammatory bowel disease, autism, and cancer. Researchers have demonstrated that an altered microbiome may also contribute to the development of dementia and Alzheimer’s disease, among other health issues. 

“The role of the gut microbiome in brain health and neurological diseases is an exciting area at the forefront of science, however, the field is in its infancy,” stated Dr. William Depaolo, a UW Medicine gastroenterologist and director of the UW Center for Microbiome Sciences & Therapeutics. “I think about the gut microbiome like a biologist thinks about the deep sea. We know there’s something down there but we finally have the technology to help us see who’s actually there and how they are influencing our bodies and brains.” Furthermore, advanced technologies allow researchers to identify species in the gut as well as analyze the bacterial genes and protein products that affect brain health, among a variety of other fundamental systems throughout the human body. 

Recently, NIH-funded research studies conducted at the Wisconsin Alzheimer’s Disease Research Center evaluated the microbiomes of people with Alzheimer’s disease and dementia. The team of researchers, led by Barbara Bendlin, Ph.D., and Frederico Rey, Ph.D., collected stool samples from participants and utilized genetic sequencing technology to identify the bacterial species present as well as determine the microbial richness and diversity. The researchers found that people living with Alzheimer’s disease and dementia have a much different and less diverse community of gut microorganisms than participants without neurological disease. Additionally, the microbiomes of people with Alzheimer’s disease and dementia showed increases and decreases in common gut bacteria, especially reduced Bifidobacterium species, an essential inhabitant of a healthy gut. The researchers also found a connection between the abnormal levels of these microbe families and the amount of Alzheimer’s disease/dementia proteins in the participants’ spinal fluid. 

The authors of the research study suggest that the unique, gut microbiome of people with Alzheimer’s disease and dementia could be contributing to the progression of the neurological disease through the gut-brain axis. Clinical trial findings in human and mouse models ultimately help demonstrate the hypothesis that restoring healthy gut bacteria composition could perhaps prevent or slow down Alzheimer’s disease and dementia in at-risk populations. 

“We understand that diet can profoundly affect the microbiome,” stated Dr. Depaolo, whose UW lab analyzes the effects of the gut microbiome on overall health and wellness. “We also know that bacterial cells are more sensitive to medicine than human cells, so we can target them without affecting human cells. There is a lot of excitement in utilizing multi-omics technology to identify microorganisms that we could promote in specific people or find strategies to manipulate the microbiome.” However, as with all attempts to create precise, targeted therapeutics for neurological diseases, it often involves genetics. 

How Genes Affect the Gut-Brain Axis

The composition of every person’s gut microbiome is unique, created in early life by diet and environmental factors over an extended period of time. However, it is our genetic background which promotes the effects that bacteria have in our gastrointestinal (GI) tract. Moreover, it is the bacteria themselves which express a variety of different genes to make proteins that may ultimately predispose certain individuals to gut inflammation or other health issues. By way of instance, in a recent NIH-funded research study conducted by researchers in the NeuroGenetics Research Consortium, the researchers suggested that Corynebacterium actually promotes the development of Parkinson’s disease but only in specific types of people with a specific type of genotype. 

The research study focused on looking at the gene SNCA rs356219, a well-known genetic risk factor for Parkinson’s disease. According to evidence, however, it’s not strong enough to cause the neurological disease by itself. But researchers have suspected a possible trigger for many years. In the research study led by Dr. Zachary Wallen, Ph.D., and Dr. Haydeh Payami, Ph.D., of the University of Alabama, researchers utilized blood samples from 197 middle-aged patients with Parkinson’s disease as well as 115 age-matched controls and determined the “genotype,” or version, of SNCA rs356219. (Humans have one of three genotypes of SNCA rs356219: including AA, GA, or GG.) Furthermore, the researchers also extracted DNA from stool samples to see what type of gut bacteria they had and then they looked for interactions between the SNCA rs356219 genotype, gut microbiome, and Parkinson’s disease risk. 

The team of researchers found that people with the GG genotype had the most amount of Corynebacterium. Every person who had the GG genotype and Corynebacterium in their digestive system also had Parkinson’s disease. "Could there be something about the GG genotype that affects or jumpstarts this bacterium’s production of disease proteins in the gut?" the researchers asked. Corynebacterium is a common bacterium found on human skin and researchers don’t know how it enters the gut, why several people have more of it than others, or if it could be a target for an antibiotic. The clinical trial findings were presented at the 142nd Annual Meeting of the American Neurological Association. Further research studies are still ultimately required. 

Although the research study needs to be replicated in a much larger population, the clinical trial findings demonstrate how fundamental it is to consider a patient’s genetic factors in gut microbiome research studies. “The issue of genetic influence cannot be ignored in this field,” says Dr. Depaolo. “We don’t yet know how genetics influence the microbiome, or how genes in bacteria are regulated. Before we start giving bacteria, antibiotics, or fecal transplants to people, we need to address the very basic question of how different genetic backgrounds can affect the microbiome as well as overall health and wellness.” 

Probiotics for Gut and Brain Health

Although we can’t change our genes, we can change our environmental factors and diet to support our microbiome as we age. Consuming fermented foods has several benefits in gut and brain health, especially for people on antibiotic medicines. These include foods that are rich in healthy probiotic bacteria, such as yogurt, kefir, kombucha, sauerkraut, and kimchi. Common foods that then feed the healthy gut bacteria include garlic, onions, Jerusalem artichoke, leeks, asparagus, bananas, barley, oats, apples, cocoa, wheat bran, burdock root, and flaxseeds, among several other prebiotics or prebiotic foods. 

“To get your microbiome into the best composition you can, I think it’s reasonable to make sure you get enough fiber into your diet,” stated Dr. Angela Hanson, MD, research scientist and geriatrician at UW Memory and Brain Wellness Center. “Consider eating yogurt with active cultures, or any other foods rich in healthy probiotics, and talking to your doctor about the possibility of taking probiotic supplements if you need to be on antibiotics for an infection.” 

There’s an entire list of questions to answer before diet advice can get more specific than simply consuming yogurt: How does diet affect the microbiome long-term? How long does it take to permanently change the gut microbiome? Can healthy bacteria in fermented foods actually establish long-lasting communities in the gut? There have been fewer research studies on the effects of fermented foods or probiotic supplements that aren't FDA approved. 

Consuming healthy bacteria can have a lot of health benefits. “Probiotics do stimulate immune and epithelial cells and produce anti-inflammatory short-chain fatty acids in the digestive system, which can help keep gut inflammation from getting out of control,” stated Dr. Depaolo. “However, simply taking just any probiotic won’t replace a community of Lactobacillus after you’ve lost it. You would have to take a probiotic that's best for your individual needs.” 

Individualized probiotics don’t exist yet, however, the microbiome is starting to be considered in Alzheimer’s disease and dementia research studies, mainly through the NIH-funded Alzheimer's Disease Metabolomics Consortium. In addition, NIH Alzheimer’s Disease Research Centers around the country are collecting microbiome samples of research study participants, in support of efforts to finally map the microbiome gut-brain communication axis in people with Alzheimer’s disease and dementia. Our microbiome has kept us alive for many years and the 100 trillion microorganisms still need a little more help. 

Brain health issues and neurological diseases can happen due to a variety of factors. However, recent research studies have shown that the gut microbiome can ultimately affect overall brain well-being. The gut-brain axis is the physical and chemical connection between the gut and brain. Millions of neurons are found throughout the brain and gut where neurotransmitters and other chemicals created in the gut can also affect brain health and wellness. However, by changing the types of bacteria in the gut, it may be possible to improve overall brain well-being. A naturopathic doctor or chiropractor can help assess the source of a patient's symptoms and determine the best course of treatment for the neurological diseases. - Dr. Alex Jimenez D.C., C.C.S.T. Insight

Approximately 100 trillion bacteria are found in the gastrointestinal (GI) tract or gut, including Bacteroides, Bifidobacterium, Faecalibacterium, and Ruminococcus, among many others. These microscopic organisms, known as the microbiome, help digest food, process nutrients, and produce immune molecules which helps heal injuries and fight inflammation. Surprisingly, however, the gut microbiome plays a much more fundamental role in the brain. 

Although the brain and the gastrointestinal tract seem to be two independent parts of the human body, they are actually connected through a series of biochemical communications between nerve cells and immune pathways, known as the gut-brain axis. Bacteria create neuroactive compounds in the gut, including up to 90 percent of all of our neurotransmitter serotonin, which ultimately helps control our mood. Moreover, the brain also sends signals to the digestive system, by way of instance, to stimulate or suppress digestion. In the article above, we discussed the brain and the gut microbiome connection. 

The scope of our information is limited to chiropractic, musculoskeletal, and nervous health issues or functional medicine articles, topics, and discussions. We use functional health protocols to treat injuries or disorders of the musculoskeletal system. Our office has made a reasonable attempt to provide supportive citations and has identified the relevant research study or studies supporting our posts. We also make copies of supporting research studies available to the board and or the public upon request. To further discuss the subject matter above, please feel free to ask Dr. Alex Jimenez or contact us at 915-850-0900. 

Curated by Dr. Alex Jimenez 

References:

• DePaolo, William, and Angela Hanson. “The Gut Microbiome and Brain Health.” The Gut Microbiome and Brain Health - Memory and Brain Wellness Center, Dimensions Magazine, 4 Oct. 2018, depts.washington.edu/mbwc/news/article/the-gut-microbiome-and-brain-health.