Role of the Gut Microbiome in Chronic Diseases
This post is a summary of the article: The Role of the gut microbiome in chronic diseases: a narrative review by Vijay, A., and Valdes, A.M. It takes a look at the specific bacteria whose metabolites lead to certain known human disease, including some auto-immune diseases. If you have any of these issues, you might want to run a gut microbiome stool test to see if you have these associated bacteria or yeast like candida in numbers outside of the normal range.
The gut microbiome, a complex community of bacteria and other microorganisms residing in the human gut, plays a crucial role in human health. Both directly and indirectly, through mediating the effects of diet, the gut microbiome has been implicated in various health outcomes. Recent studies have highlighted the influence of gut microbiota on remote organs, mucosal, and immune functions. Understanding the development of the microbiome in the context of health outcomes and microbiome-host molecular interactions (in other words, looking at the microbiome in chronic diseases) is pivotal for developing approaches to rehabilitate disturbed microbial ecosystems and restore health.
Gut Microbiome and Autoimmune Diseases
Rheumatoid Arthritis (RA)
RA, a systemic autoimmune inflammatory condition, is characterized by joint damage. Environmental factors like diet, smoking, and infections contribute to the development of intestinal/oral dysbiosis and RA onset. Studies show germ-free mice are protected from experimental arthritis, indicating a role for the microbiome in RA pathogenesis. RA patients exhibit altered gut microbiota composition, with increased abundance of Prevotella species and decreased beneficial microbes like Faecalibacterium. Collinsella aerofaciens has been implicated in RA by increasing gut permeability and inducing IL-17A expression. Dietary intake of short-chain fatty acids (SCFAs) like butyrate suppresses inflammation in RA, highlighting the potential of targeting gut microbiota for therapeutic interventions.
Type 1 Diabetes (T1D)
Alterations in gut microbiota composition precede the onset of T1D. Studies report increased Bacteroides species and decreased SCFA-producing bacteria in T1D patients. Specifically, Faecalibacterium prausnitzii is reduced in children with diabetes-related autoantibodies. Increased gut permeability and decreased microbial diversity are linked to T1D development. SCFAs, particularly butyrate, protect against T1D by modulating immune responses. Gut permeability and inflammation play significant roles in T1D development, emphasizing the importance of gut microbiota in disease onset and progression.
Atopic Eczema and Asthma
Atopic eczema, a chronic inflammatory skin disorder, is associated with gut microbiota composition. Increased Clostridia, Clostridium difficile, Escherichia coli, and Staphylococcus aureus and decreased Bifidobacteria and Bacteroidetes are observed in patients with eczema. SCFA-producing bacteria are reduced in severe eczema cases. Asthma prevalence has risen due to altered environmental exposures affecting the gut microbiota. Early-life gut dysbiosis impacts immune-cell maturation and respiratory disease development. SCFAs and other microbial metabolites influence immune responses, reducing asthma severity.
Gut Microbiome and Gut Inflammation/Bowel Disorders
Irritable Bowel Syndrome (IBS)
IBS, characterized by abdominal pain and altered bowel habits, is linked to gut microbiota variations. Increased Firmicutes, Ruminococcus, Clostridium, and Dorea, and decreased beneficial microbes like Bifidobacterium and Faecalibacterium are observed in IBS patients. FODMAP diet restriction alleviates IBS symptoms by modulating gut microbiota composition and microbial metabolite production.
Inflammatory Bowel Disease (IBD)
IBD, including Crohn’s disease and ulcerative colitis, involves chronic inflammation of the GI tract. Microbial dysbiosis in IBD is marked by decreased Firmicutes and increased Proteobacteria. Reduced butyrate-producing bacteria, like Faecalibacterium prausnitzii and Roseburia, correlate with lower butyrate production, impacting gut health. Probiotics and dietary interventions targeting butyrate-producing bacteria show potential in restoring gut homeostasis in IBD.
Small Intestinal Bacterial Overgrowth (SIBO)
Small Intestinal Bacterial Overgrowth (SIBO) is a condition characterized by an abnormal increase in the number of bacteria in the small intestine, particularly types that are more commonly found in the colon. This overgrowth can disrupt the normal digestive processes, leading to symptoms such as bloating, diarrhea, abdominal pain, and malnutrition. SIBO is often associated with conditions that affect gut motility, such as irritable bowel syndrome (IBS), celiac disease, and certain surgeries that alter the digestive tract. The diagnosis of SIBO typically involves breath tests that measure the production of hydrogen or methane, gases produced by bacteria in the small intestine.
The gut microbiome, comprising trillions of microorganisms including bacteria, viruses, fungi, and other microbes, plays a crucial role in maintaining overall health. These microorganisms are involved in various functions such as digestion, immune response, and the production of vitamins and other essential nutrients. A healthy gut microbiome is diverse and balanced, but factors like diet, antibiotics, and illness can disrupt this balance, leading to dysbiosis—a state of microbial imbalance. Dysbiosis has been linked to several health issues, including SIBO, where the overgrowth of bacteria in the small intestine can further exacerbate gut health problems. Understanding the interplay between SIBO and the gut microbiome is essential for developing effective treatments and maintaining gastrointestinal health.
Gut Microbiome Composition and Cardiometabolic Diseases
Cardiovascular Disease (CVD)
Gut microbiota alterations contribute to CVD development. Studies show links between gut microbiota and myocardial infarction severity. Hypertension, a modifiable CVD risk factor, correlates with changes in gut microbiota composition. SCFAs modulate blood pressure via G-protein coupled receptors, impacting renin secretion and blood pressure regulation. Probiotics like Lactobacillus plantarum and Lactobacillus rhamnosus improve ventricular function and attenuate heart failure, suggesting potential benefits in CVD management.
Type 2 Diabetes (T2D)
T2D patients exhibit altered gut microbiota composition, with decreased butyrate-producing bacteria like Faecalibacterium and increased opportunistic pathogens. SCFAs, especially butyrate, improve insulin sensitivity and glucose metabolism. Gut microbiota-derived metabolites predict T2D risk, emphasizing the role of microbial composition in disease development.
Non-alcoholic Fatty Liver Disease (NAFLD)
NAFLD and non-alcoholic steatohepatitis (NASH) are linked to gut dysbiosis and increased intestinal permeability. Altered gut microbiota, including decreased Faecalibacterium and increased Proteobacteria, contribute to NAFLD development. SCFAs play dual roles in NAFLD, with butyrate and propionate showing protective effects while acetate correlates with disease severity. Understanding microbial signatures and SCFA balance may aid in NAFLD diagnosis and treatment. Adding SCFA foods to the daily diet can help improve a person’s outcome when fatty liver is involved.
Chronic Kidney Disease (CKD)
Gut microbiota alterations are observed in CKD patients, with decreased beneficial microbes and increased pathogens. Reduced SCFA production and increased uremic toxins contribute to CKD progression. Prebiotic, probiotic, and synbiotic supplementation show potential in restoring gut microbiota balance and reducing inflammation in CKD.
Mental Health Disorders
The gut-brain axis links gut microbiota to neurological functions. Altered gut microbiota composition is associated with mental health disorders like schizophrenia, ADHD, anxiety, PTSD, depression, and dementia. Gut-derived metabolites influence the central nervous system, affecting mental health. Psychobiotics, including pre- and probiotics, show promise in treating mental health disorders by modulating the gut-brain axis.
Therapeutic Targeting of the Gut Microbiome in Chronic Diseases
Various strategies target the gut microbiome to manage chronic diseases, including antibiotics, dietary modifications, prebiotics, probiotics (such as Bifidobacterium longum and Saccharomyces boulardii, and fecal microbiota transplantation (FMT). FMT shows success in treating antibiotic-resistant C. difficile infection and improving insulin sensitivity in metabolic syndrome. Dietary interventions, particularly high-fiber diets, promote healthier gut microbiota composition and metabolic profiles. Personalized dietary and microbial interventions hold promise for effective chronic disease management.
The gut microbiome plays a critical role in chronic disease development and management. Understanding microbial composition and function in relation to health outcomes is essential for developing effective therapeutic strategies. Nutritional interventions and microbial supplementation offer promising avenues for restoring gut health and preventing chronic diseases. Ongoing research will continue to unravel the complex interactions between gut microbiota and human health, paving the way for personalized microbiome-based therapies.
