Abstract P620: Microbiota Composition and Diversity Are Associated With Fat Tissue Quality: Findings From Baltimore Longitudinal Study of Aging

Background: Human studies have reported associations of the gut microbiome with central adiposity, including with pathologic visceral adipose tissue (AT) area. However, AT quality (e.g., lipid content, fibrosis) can vary at similar AT areas. Lower AT x-ray radiodensity reflects lower AT quality and has been associated with greater cardiometabolic risk. To our knowledge, no studies have examined associations of gut microbiome features with AT radiodensity. Objective: To test the hypothesis that gut microbiota diversity and composition are associated with abdominal AT area and radiodensity. Methods: The Baltimore Longitudinal Study of Aging is a cohort of community-dwelling older adults. From 2013 to 2017, we collected fecal samples for shotgun metagenomic sequencing; a subset of participants (N=428) also had abdominal computed tomography scans. We measured area and radiodensity of both subcutaneous (SAT) and visceral (VAT) AT. We examined associations of microbiota alpha and beta diversities with fat measures using linear regression and PERMANOVA, respectively. We tested for bacterial species associations using ANCOM-BC. We adjusted statistical models for age, sex, race, education, and physical activity. Results: Our study sample had a mean age of 73.6 years and BMI of 27.6 kg/m 2 , was 52.8% female, and 26.9% identified as Black. A 1-SD increment in the alpha diversity Shannon Index metric was associated with -600.8 mm 2 lower VAT area (95%CI: -1106.0, -95.5), but was not associated with other fat measures. VAT area and VAT or SAT radiodensity were associated with weighted UniFrac. Multiple bacterial species associated with larger VAT area were also associated with lower VAT or SAT radiodensity, including species previously associated with central adiposity (e.g., Ruminococcus gnavus ). Conclusion: In this large cohort of older US adults, bacterial species associated with larger VAT area were also associated with a measure of worse AT quality, suggesting these bacterial species may drive adipocyte dysfunction.