Caloric restriction mimetics improve gut microbiota: a promising neurotherapeutics approach for managing age-related neurodegenerative disorders.

The gut microbiota (GM) produces various molecules that regulate the physiological functionality of the brain through the gut-brain axis (GBA). Studies suggest that alteration in GBA may lead to the onset and progression of various neurological dysfunctions. Moreover, aging is one of the prominent causes that contribute to the alteration of GBA. With age, GM undergoes a shift in population size and species of microflora leading to changes in their secreted metabolites. These changes also hamper communications among the HPA (hypothalamic-pituitary-adrenal), ENS (enteric nervous system), and ANS (autonomic nervous system). A therapeutic intervention that has recently gained attention in improving health and maintaining communication between the gut and the brain is calorie restriction (CR), which also plays a critical role in autophagy and neurogenesis processes. However, its strict regime and lifelong commitment pose challenges. The need is to produce similar beneficial effects of CR without having its rigorous compliance. This led to an exploration of calorie restriction mimetics (CRMs) which could mimic CR's functions without limiting diet, providing long-term health benefits. CRMs ensure the efficient functioning of the GBA through gut bacteria and their metabolites i.e., short-chain fatty acids, bile acids, and neurotransmitters. This is particularly beneficial for elderly individuals, as the GM deteriorates with age and the body's ability to digest the toxic accumulates declines. In this review, we have explored the beneficial effect of CRMs in extending lifespan by enhancing the beneficial bacteria and their effects on metabolite production, physiological conditions, and neurological dysfunctions including neurodegenerative disorders.