Abstract Age dependent microbial dysbiosis is now considered to be a hallmark of aging. Understanding the mechanisms by which the gut microbiome modulates aging phenotypes will yield new avenues for the treatment and prevention of age-related disease. Our work has shown that high-fat diet (HFD) and intermittent fasting (IF) diet generate distinct gut microbiomes, and have contrasting-effects on cellular senescence. One central idea of the parent R01 grant is that diet dependent changes in gut microbiome composition modulate cellular senescence. However, the parent grant did not propose any molecular mechanism by which the gut microbiome may impact senescence. This diversity grant proposes a mechanistic study that tests a novel hypothesis that the microbiomes generated by HFD and IF differentially affect gut barrier function, resulting in the translocation of Molecular Associated Molecular Patterns (MAMPs) with opposing effects on senescence and macrophage function in Visceral Adipose Tissue (VAT). Aim 1 will investigate the effect of the microbiomes produced by IF and HFD on gut barrier integrity and characterize the microbiota that translocate into VAT. Single cell RNAseq will be done to reveal how microbiome composition impacts polarization of the various types of macrophages in visceral fat. Aim 2 will employ a combination of in-vivo, and in-vitro assays to directly study how translocated MAMPs affect preadipocyte, adipocytes and macrophages, with regard to senescence and macrophage function at the molecular level. This supplement proposal provides the candidate with comprehensive cross-disciplinary training in the fields of immunology, microbiome, and aging biology. This supplement will prepare the candidate to successfully undertake and complete cutting-edge research as he develops his career as geriatric immunologist.