Age-associated Arterial Dysfunction, Western Diet, and Aerobic Exercise: Role of the Gut Microbiome

In order to investigate how age-related changes to the gut microbiome, as modulated by Western diet and exercise, influences arterial function in humans, the investigators will capitalize on the plasticity of the gut microbiome to dietary perturbations. A randomized, single-blind, 2x1-week dietary intervention crossover study (with 3 week washout) will be conducted in young (18-29 years) and old (60-79 years), exercising and non-exercising, male and female adults from all races and ethnic backgrounds. Testing will take place on the University of Colorado Boulder main campus at the Clinical and Translational Research Center (CTRC - located in the Wardenburg Health Center). Subjects will undergo telephone and in-person CTRC screening, with those eligible assigned to either Group A or Group B using block randomization stratified by age and exercise status. Group A will undergo isocaloric WD feeding (high fat [40%], high sugar [25%], low fiber [15g], low nutrient) during Phase 1 (first 1-week treatment period) and non-WD feeding (low-fat [25%], low sugar [15%], high fiber [22g], high nutrient) during Phase 2 (second 1-week treatment period). Group B will undergo the dietary interventions in the opposite order. Phases 1 and 2 will be separated by a 3-week washout period to prevent carry over effects. During each 1-week intervention period, fecal swabs will be collected daily to characterize the gut microbiome and vascular function, will be measured at baseline and after 2 and 7 days of controlled feeding to gain insight into the temporal relation between these outcomes.