PROJECT SUMMARY Research on the gut microbiome as a target for disease prevention and therapy is an intriguing arena for public health because microbes and their metabolites are modifiable. Observational studies, murine models and a few trials in humans suggest dietary factors exert many of their health effects in the host through modification of the gut microbiome and its associated metabolome. Moreover, early evidence indicates the microbiome and metabolome modify the effects of diet interventions on health outcomes, suggesting the microbiome and metabolome have a role in precision nutrition. However, rigorously controlled feeding trials in humans are still needed to determine the effects of whole diet inverventions on the microbiome and metabolome, and to test if the microbiome and metabolome modify or mediate the effects of diet on cardiovascular risk factors, including blood pressure. Of particular interest are the effects of dietary patterns and level of sodium (Na+) intake. The primary objective of this study is to examine the effects of the American Heart Association recommended Dietary Approaches to Stop Hypertension (DASH) diet (compared to a typical U.S. diet) and lower dietary Na+ intake vs. higher dietary Na+ intake on the gut microbiome and the untargeted and targeted metabolome— including short chain fatty acids—in a multi-racial cohort of adults with type 2 diabetes enrolled in the DASH4D trial – a recently funded randomized, cross-over, isocaloric controlled feeding trial. A secondary objective is to explore if the gut microbiota and their metabolites modify and/or mediate the effects of diet patterns and Na+ on blood pressure, thusly informing precision nutrition. We will also examine if effects vary by sex. In particular, we propose to perform whole genome shotgun metagenomics, high-throughput metabolomics profiling, and targeted quantification of short chain fatty acid metabolites. We will jointly investigate the microbiome and metabolome measured in stool and blood collected before and after each of the diet periods in the feeding trial. Dr. Mueller (PI) will carry out this research with an outstanding group of interdisciplinary co-investigators in the collaborative and eminent environments of the Johns Hopkins Welch Center for Prevention, Epidemiology and Clinical Research and the Bloomberg School of Public Health. Dr. Mueller’s co-investigators have complementary expertise in feeding trials (Appel), -omic statistics (Zhao), bioinformatics (Debelius, Bittinger), metabolomics (Rebholz), and short chain fatty acids (Pluznick). With the support of Dr. Mueller’s research team, he is well positioned to complete the proposed activities. The findings have great potential to: (a) identify objective measures of adherence to the DASH diet and lower dietary Na+ intake; (b) reveal novel mechanisms underlying the BP effects of dietary patterns and Na+ intake; (c) offer new disease prevention strategies and therapeutic possibilities and; ...