PROJECT SUMMARY/ABSTRACT The purpose of this F31 application is to provide support for Ms. Abigail Casso, a 2nd year PhD student in Dr. Douglas Seals’ (sponsor) laboratory at the University of Colorado Boulder, to conduct research and training that will prepare her to become an independent investigator in the field of translational cardiovascular (CV) aging research aimed at the prevention and treatment of age-related CV diseases (CVD). As part of her proposed training plan, she aims to both refine research skills presently under development and learn a variety of new technical, conceptual, and professional skills, including the use of preclinical mouse models and gaining new experiences using human biospecimens, cell culture bioassays, and metabolomics approaches. Her proposed research project seeks to investigate the role of age-related changes in the human gut microbiome and circulating gut microbiome-derived metabolites in impairing vascular endothelial function. Gut microbiome composition is uniquely altered with CVD and aging, and age-related changes in circulating concentrations of certain gut-derived metabolites have been related to CVD. However, whether these age-related changes causally impair endothelial function is unknown. Guided by strong preliminary data, Ms. Casso will determine: (Aim 1) If age-related changes in the human gut microbiome impair endothelial function due to increased oxidative stress and reduced nitric oxide bioavailability using innovative “humanized” mouse models and ex vivo “pharmaco-dissection” techniques; (Aim 2A) The effect of age-related, gut microbiome-induced changes in plasma circulating factors on endothelial function using cell culture bioassays; (Aim 2B) Which circulating metabolites are altered by the aging human gut microbiome via targeted metabolomics; and (Aim 3) If specific gut-derived metabolites that are increased in circulation with age directly induce endothelial dysfunction using cell culture and isolated vessel approaches. The expected results will identify novel gut microbiome-related and circulating gut-derived metabolite modulators of endothelial function and may facilitate translation of these metabolites as new therapeutic targets for prevention and treatment of age-related endothelial dysfunction. Overall, the proposed research has the potential to address important NHLBI Strategic Vision research priorities, including: 1) investigate new pathobiological mechanisms important to the onset of CVD; and 2) identify novel therapeutic targets to prevent and treat CVD113. Dr. Seals is an internationally recognized and NIH-funded scientist with a strong history of successful mentoring in translational CV research, particularly in the emerging field of “vascular aging”. Under his supervision and with the guidance of content expert co- mentors Drs. Vienna Brunt, Angelo D’Alessandro, and Tiffany Weir, Ms. Casso will be able to successfully complete the proposed research and training plan, facilita...