AN ILLUSTRATIVE VIEW OF THE GUT MICROBIOME
Impact on Health
Gastrointestinal Health
Inflammatory Bowel Disease
Alteration of the gut microbiome
Inflammation of the gut
Inflammatory bowel disease is an umbrella term for Crohn’s disease and Ulcerative colitis with the characteristics of chronic relapsing inflammation of the gut. This may be caused by environmental factors, changes in the gut microbiome, altered innate immunity or altered mucosal barrier function.
Studies have shown a link between the gut microbiome and the development of inflammatory bowel disease. Through the use of metagenomics and metatranscriptomics, the identification of specific changes of bacteria in the gut has been achieved.
These changes include:
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Decreased bacterial diversity
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Alteration of dominating bacteria
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Increase in short-chain fatty acid (SCFA)-producing bacteria
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Decrease in expression of carbohydrate metabolising genes
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As we know that SCFAs have a role in the epithelial cell maintenance, it is thought that a decrease in this bacterial product is involved in the development of IBD.
The question of whether changes in the gut microbiome are a cause or consequence of disease still remains unanswered. However, it has been suggested that recurrent inflammation seen in IBD may be explained by a vicious cycle of inflammation and alteration of the gut microbiome which causes further inflammation
Mental Health
Anxiety & Depression
It has been suggested that changes in microbial content, immune stimulation, neural pathways and bacterial metabolites such as SCFAs, are potential mechanisms for altered mental wellbeing.
In healthy individuals, a protective barrier is formed in the gut from epithelial cells, mucus layer and commensal bacteria, however, changes in gut microbiota have shown to cause damage to this protective barrier allowing for microbial invasion through the epithelial cells.
This increased permeability means harmful bacterial products may enter the systemic circulation and make their way to the brain. They can then cross the blood-brain barrier causing changes in electrical layout of neural membranes which may lead to mental health disorders, such as anxiety and depression.
The Gut-Brain Axis
As mental health problems are often associated with gastrointestinal problems, it may also be that an overactive immune system is a cause of mental health disorders, as inflammation causes bacteria to leak through the epithelial cells lining the gut.