PROJECT SUMMARY/ABSTRACT The purpose of this F31 application is to provide support for Mr. Nathan Greenberg, a 3rd year graduate student (1st year PhD student) in Dr. Douglas Seals’ (sponsor) laboratory at the University of Colorado Boulder, to conduct research and training that will prepare him 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). He plans to refine research skills currently under development and learn a variety of new technical, conceptual, and professional skills including working with human biospecimens, using pharmaco- dissection approaches in cultured aortic rings, conducting biochemical assays, and mastering measurement of in vivo aortic pulse wave velocity. Gut microbiome composition is uniquely altered with CVD and aging, and consequent gut-derived changes to the circulating milieu are related to CVD. However, whether these age- related changes causally increase aortic stiffness is unknown. Thus, the proposed research project seeks to establish the human gut microbiome as a key modulator of age-related aortic stiffening. Guided by strong preliminary data, Mr. Greenberg will determine, using innovative “humanized” mouse models: Aim 1: If age-related changes in the human gut microbiome directly increase aortic stiffness, accompanied by: i) increases in circulating lipopolysaccharide (LPS) and flagellin, 2 key components of bacterial cell walls that can enter circulation; ii) activation of toll-like receptors in circulating immune and/or vascular cells; iii) increased aortic inflammation and oxidative stress; iv) increased formation of advanced glycation end products; Aim 2: If aortic intrinsic mechanical stiffness is altered by the gut-derived “factors” in the circulating blood (“circulating milieu”) by exposing excised aorta rings to plasma from “humanized” mice; Aim 3: The mechanisms by which changes in the circulating milieu induced by the gut microbiome of older vs. young humans directly increases aortic stiffness using innovative “pharmaco-dissection” approaches. This research will be the first to investigate a causal role of the aging human gut microbiome and microbiome-derived circulating milieu in mediating arterial stiffening. If successful, this work will establish the human gut microbiome as a therapeutic target for treatment/prevention of age-related arterial stiffening. Overall, the proposed research has the potential to address two important NHLBI Strategic Vision research priorities: 1) investigate new pathobiological mechanisms important to the onset of CVD; and 2) identify novel therapeutic targets to prevent and treat CVD. Dr. Seals is an internationally recognized and NIH-funded scientist with a strong history of successful mentoring in translational CV research, particularly in “vascular aging”. Under his supervision and with the guidance of expert co-mentors Drs. Vienna Brunt, an...