The gut microbiome and ageing trajectories: mechanisms and clinical implications.

This Review discusses the current state of knowledge on the contribution of the gut microbiome as a potential key actor in defining how we age. The gut microbiome is a complex ecosystem that establishes lifelong dynamic interactions with the host at multiple levels (several gut-organ axes), differently influencing ageing patterns and age-related disease onset and progression across populations. Accordingly, the definition of a 'normative' gut microbiome remains elusive, depending largely on the interaction with the external environment. In this complex scenario, the causal role of the gut microbiome in defining the ageing trajectory and its precise contribution to various organ-specific age-related diseases is still uncertain in clinical terms and could be context specific. Multiparametric and uniqueness indexes within a given population have shown a certain capacity for predicting disability and mortality. However, the gut microbiome is shaped over time by exposure to different intrinsic and environmental factors, resulting in a high degree of inter-individual variability, a key phenomenon that should be considered to develop novel personalized strategies to counteract age-related disease and frailty.