What is the Gastrointestinal (GI) Microbiome?
The term gastrointestinal microbiome refers to the genome of all microbiota (bacteria, fungi and other microorganisms) that live in the gastrointestinal tract. The majority of these microbes live in the colon. Most of the organisms are bacteria, but the microbiome is also composed of genes that come from fungi, viruses and Archaea that normally inhabit the GI tract of all animals. There are ~100 trillion organisms in total. In the average human being, the weight of these micro-organisms is ~5 pounds! There are anywhere from 500 to 1,000 different species that normally inhabit the GI tract. Although every individual has a unique microbiome composition, in general the microbiome of dogs and humans is very similar. We share ~20% of our microbiome with pets and family members that live in our household. In addition to the sheer number of organisms living inside our GI tract, each of these organisms has their own genome. Collectively there are more than 3 million genes that arise from these microbiota. This is approximately 130 times larger than human genome and 160 times larger than the canine genome!
What is the function of the microbiome?
The microbiota play a huge role in the digestion and absorption of nutrients. These organisms also are extensively involved with the function of the immune system. Approximately 70% of the body’s immune system cells are found in the intestinal tract. A normal microbiome is important for immune tolerance so that immune-mediated diseases do not develop. A normal microbiome is also important in the protection against infectious diseases. The micro-organisms residing in the GI tract produce over 1,000 metabolites, including beneficial short chain fatty acids, Vitamin K, B12, thiamine, riboflavin, and many others. The microbiome is intimately involved in the metabolism of many drugs.
What is Intestinal Dysbiosis and what are the Potential Consequences?
- Intestinal dysbiosis is defined as an imbalance among the types of microorganisms in the GI tract. This could be due to an overgrowth of potential pathogens, a decrease in commensal organisms, a decreased overall abundance of organisms, or any combination of these scenarios. When dysbiosis occurs, it leads to inflammation through the production of pro-inflammatory cytokines. This can lead to many different chronic diseases. Some of the diseases that have been associated with dysbiosis in people and in rodent research models include:
- Alzheimer’s disease (type 3 diabetes)
- Autoimmune disease (rheumatoid arthritis, others)
- Cancer (colorectal, breast cancer, pancreatic cancer, lymphoma, others)
- Chronic recurrent UTIs
- Depression (major depressive disorder)
- Diabetes mellitus
- Heart disease
- Irritable Bowel Disease (IBD)
- Metabolic syndrome
- Parkinson’s disease
- Periodontal disease
- Seizure disorders
- Skin disease (rosacea, psoriasis, eczema)
This is an extensive list, but not an exhaustive list. The association with some of these diseases is just an association, but more and more research continues to come out in the realm of dysbiosis, and many studies are now starting to show evidence that intestinal dysbiosis is contributing to the cause of some of these diseases.
What are Some of the Causes of Intestinal Dysbiosis?
The use of antibiotics is a major cause of intestinal dysbiosis. Unfortunately, all antibiotics can cause dysbiosis, as they will kill commensal flora in addition to potential pathogens. Diet is a major contributor to a healthy microbiome, and we will discuss this in great detail in an upcoming article. Some dietary components that can cause dysbiosis include sugar, food additives, and processed food ingredients.
Pesticides in food and in the environment can lead to dysbiosis. C-section birth can also lead to dysbiosis, although this is not as big of a problem in dogs as it is in humans because of the relative rarity of C-section birth in dogs. In children, there is an increased association with asthma and atopy in children born by C-section. Poor dental hygiene has been shown to be a cause of dysbiosis, as well as high levels of stress and anxiety.
Gastrointestinal Diseases can Occur Simultaneously with Intestinal Dysbiosis
Intestinal dysbiosis can occur in the absence of apparent intestinal disease. However, most of the time dysbiosis occurs in conjunction with an intestinal disease. In these instances, it is hard to determine if the dysbiosis caused the intestinal disease, or if the dysbiosis developed because of the intestinal disease.
Here is a list of intestinal diseases that have been associated with intestinal dysbiosis:
- Chronic enteropathies
- Food responsive
- Antibiotic responsive
- Inflammatory bowel disease (IBD)
- Acute diarrhea due to various causes, infectious and non-infectious
- Intestinal stasis and other motility disorders
- Decreased gastric acid output
- Administration of acid suppressing drugs (H2-blockers, proton pump inhibitors)
- Exocrine pancreatic insufficiency
Ethos Discovery Research
Intestinal dysbiosis is an alteration in the composition and/or richness of the normal bacteria that are found in the gastrointestinal tract (microbiota). It has been suggested that states of intestinal dysbiosis exist and may possibly correlate with disease processes that affect the health of the intestine and other organs and diseases, such as cancer and immune-mediated diseases. The effect of intestinal dysbiosis on the progression of various diseases is currently lacking in both human and veterinary medicine. Ethos Discovery now asks what the influence of intestinal dysbiosis is on a variety of non-GI diseases in veterinary patients.
In this program we will first determine if dysbiosis is associated with distant diseases and then use this as a starting point to:
- Develop new blood-based tests for the diagnosis of dysbiosis.
- Develop novel diets and other treatments for clinically important dysbiosis.
This article was originally published on our sister site: Ethos Discovery under the title “About Intestinal Dysbiosis and why it is a Priority for Ethos Discovery”. To learn more about Ethos Discovery, please visit the website.