Gut microbiota and geriatric health

Each individual has a distinct gut microbiota composition that serves a variety of important roles in the metabolism of the host's nutrients, immunomodulation, and maintains immunity and inflammatory response and influences the gut–brain axis (GBA). In addition to modulating the immune system, the hypothalamic–pituitary–adrenal (HPA) axis, and tryptophan metabolism, microorganisms can synthesize several neurotransmitters and generate metabolites, such as short-chain fatty acids (SCFAs), that have neuroactive features. The gut microbiome is highly susceptible to lifestyle modifications, diet and xenobiotics, which leads to dysbiosis. Dysbiosis in the geriatric population can cause numerous disease conditions like Alzheimer's and Parkinson's disease, cardiovascular disease, gastrointestinal disease, and cancer. Dysbiosis of the gut microbiota has been associated with behavioural and neurological disorders such as depression, Alzheimer's, Parkinson's, and autism spectrum disorder. Furthermore, SCFA administration and microbiota alteration have been suggested as therapy objectives for these illnesses. DNA-based culture-independent methods, including next-generation sequencing, which provide quantitative information on the human gut microbiota are used to define the entire gut health and its relation to various disorders. The current review aims to summarize the available literature on the role of gut microbiota in ageing and dysbiosis in disease conditions.