The Nutritional Links for Gut Microbial Dysbiosis and its Metabolic and Endocrinal Fallouts
Authors: V Nikhra 
Published: November 2022

The Human Gut Microbiome: The gastro-intestinal tract, skin and genitals, and various other body organs, harbour large and diverse communities of bacteria, viruses, and other microscopic life. In the human gut, a nutrient-rich environment, reside ~ 100 trillion microbes, the vast majority of which is present in the colon. There inhabit microbial members as residents (autochthonous), while others (allochthonous) are from ingested food, water, and other components of the environment. The adult human gut microbiota is dominated by mainly two bacteria, the Bacteroidetes and Firmicutes, and an archea, Metanobrevibacter smithii. The microbial ecosystems throughout the body interact with the molecular processes, which have been linked to various aspects of human physiology. The understanding about microbiota is evolving and presents as an important research avenue. The Gut Biosphere and Ecosystem: In general, the gut microbial communities depend on their specific enzymes and molecules to utilize available nutrients, cell-surface molecular appendages to attach on to their right habitat, to evade bacteriophages, with ability to deal with immune system and avoid washout and genetic mutability to stay well-adapted. The microbiota influences various biological processes and organ physiology, including gastrointestinal processes, energy metabolism and insulin resistance, and thus influence weight gain, development of diabetes, and aging. The intestinal epithelium actively senses various bacteria and plays an essential role in maintaining host-microbial homeostasis at the mucosal interface. On the other hand, the host factors, such as dietary factors influence the host-microbial and microbial-microbial relationships. Microbiota, Health and Disease States: The evidence from clinical studies and animal models shows a link between the gut microbiome and human health. There exists a bidirectional microbiota–gut–brain communication which modulates brain function and behaviours. The research in mice and humans is beginning to establish a link between the composition of microbes in the gut and immune response to tumor cells. Certain metabolites or antigens presented by members of that microbiome may help uplift the sensitivity of immune system to tumour cells, whereas dysbiosis may lead to the loss of antitumor immunity. On the other hand, the gut microbes harbour enzymes and secrete molecules that can influence drug activation, efficacy, and metabolism. Dietary Constituents and Microbiome: The dietary components influence the gut microbiota. It has been documented that a change in diet can alter the degradative activity of the colonic microbiota in vivo and in a physiologically relevant setting influence the expression of various microbial genes. The complex plant polysaccharides in diet are not digested and enter the colon as a potential food source for the gut microorganisms, which harbour a multitude of genes involved in catabolism of carbohydrates. The reduced availability of dietary polysaccharides and fibre can trigger dysbiosis and degradation of intestinal mucin layer and affect intestinal health. The microbial production of short chain fatty acids and other metabolites has been shown to influence immune system.