Research from the last decade has identified cellular senescence and alteration of gut microbial composition as primary physiological processes that facilitate aging and a wide range of age-related diseases. Because of their profound impact on health and disease, they represent two promising ideas in developing innovative strategy to improve health and increase longevity. However, the interplay of the microbiome and cellular senescence in age- related metabolic dysfunction is largely unknown. The major goal of this proposed study is to elucidate the causal connection of cellular senescence and the microbiome in older mice under metabolic stress. We showed a high fat diet (HFD) induced senescent cell loads, increased the abundance of pro-inflammatory gut bacteria, and aggravated metabolic function. In contrast, caloric restriction (CR) decreased gene expression associated with senescence in humans and mice. An intermittent fasting (IF) diet that mimics CR improved metabolic function, and increased the abundance of Akkermansia known to have strong anti-inflammation and anti-aging property. Using our novel p21-Cre mouse model, we found that depletion of senescent cells expressing high levels of p21 (p21high) profoundly increased the relative abundance of Akkermansia, and improved metabolic dysfunction in male mice on a HFD. In Aim 1, we will test the hypothesis that cellular senescence modulates the microbiome composition and function. This will be achieved by directly transplanting or genetic clearance of senescent cells in older male and female mice, and determine their impact on the gut microbiome and microbial metabolites (Aim 1a). The microbiome changes will be determined at population level and functional level as these have not been well-defined previously in aging or age-related diseases. Using our novel p21-Cre mouse model, we will further assess if senescence induced alteration of the microbiome is a novel mechanism by which senescent cells influence metabolic function. We will also test the hypothesis that SASP mediates the senescence-induced microbiome changes by inactivating NF-κB in p21high senescent cells (Aim 1b). In Aim 2, we will test the hypothesis that the gut microbiome modulates senescence development. We will examine development of senescence in mice receiving fecal microbiota derived from a HFD (Aim 2a). We will determine the potential suppression of senescent cells by fecal microbiota transplantation of the microbiota derived from IF or mono- colonization of Akkermansia (Aim 2b). Establishment of reciprocal modulation of the microbiome and cellular senescence will deepen our fundamental understanding of the pathophysiology of aging and age-related metabolic diseases, and pave the way to develop robust interventions targeting senescence, microbiome or both to improve health and increase longevity.

Aging and age-related metabolic dysfunction poses unprecedented challenge to public health, and development of innovative and targetable interventions is highly warranted. Our project will examine the interplay of the microbiome and cellular senescence underlying diet-induced metabolic dysfunction in mice with older age. It will offer an integrative understanding of pathophysiology of age-related diseases, and lay a solid foundation to develop robust interventions targeting senescence, microbiome or both to improve health and increase longevity.