Role of Gut Microbiome on Metabolic Disorders

Microbiome that reside in the human gut are key contributors to host metabolism and are considered potential sources of novel therapeutics in metabolic disorders. This review discusses the role of gut microbiome in the pathogenesis of obesity, type 2 diabetes mellitus (T2DM), chronic kidney disease and cardiovascular disease. Gut microbiome remains quite stable, although changes take place between birth and adulthood due to external influences, such as diet, disease and environment. Understanding these changes is important to predict diseases and develop therapies. In gut heamostasis, Gut microbiome converts high fibres intake into short-chain fatty acids like butyrate, propionate and acetate which normalize intestinal permeability and alter de novo lipogenesis and gluconeogenesis through reduction of free fatty acid production by visceral adipose tissue. This effect contributes to reduce food intake and to improve glucose metabolism. Propionate can also bind to G protein coupled receptors (GPR)-43 expressed on lymphocytes in order to maintain appropriate immune defence. Butyrate activates peroxisome proliferator-activated receptor-γ (PPAR-γ) leading to beta-oxidation and oxygen consumption, a phenomenon contributing to maintain anaerobic condition in the gut lumen. In contrast, diets most especially western diet consisting among others of high fat and high salt content has been reported to cause gut dysbiosis. This alteration of gut microbiome result to chronic bacterial translocation and increased intestinal permeability that can drive a systemic inflammation leading to macrophage influx into visceral adipose tissue, activation of hepatic kuffer cells and insulin resistance in type 2 diabetes. This effect contributes to lower mucus thickness, decrease butyrate and propionate producing bacteria, L-cells secrete less gut peptides, lack of PPAR-γ activation lead to higher oxygen available for the microbiome at the proximity of the mucosa and increases the proliferation of Enterobacteriaceae with commensurate increase in opportunistic pathogens. However, Gut microbiome are major biomarker for early prognosis of diabetes and other metabolic disorders.