Six Weeks of Aerobic Exercise Improves Markers of Insulin Sensitivity and Metabolic Endotoxemia

Abstract

PURPOSE: Research from our laboratory indicates that six weeks of aerobic exercise alters the gut microbiota and microbial-derived short chain fatty acids (SCFAs) in both lean and obese humans. SCFAs directly modulate inflammation, insulin sensitivity and gut barrier function. Thus, the objectives of the present study were to (1) determine the effects of aerobic exercise training on circulating metabolic and inflammatory parameters indicative of inflammation, insulin sensitivity, and gut barrier function and (2) determine whether changes in these parameters paralleled shifts in the microbiota and its metabolites. METHODS: Previously sedentary but otherwise healthy adults (n=16 lean; n=11 obese) underwent a six-week aerobic exercise intervention. Blood samples collected before and after the intervention were analyzed for C-reactive protein (CRP), lipopolysaccharide binding protein (LBP), and insulin resistance by the homeostatic model assessment (HOMA-IR). Fecal samples were analyzed for microbiota composition (16S rRNA gene sequencing) and SCFA concentrations (gas chromatography). RESULTS: At baseline, obese individuals had significantly higher CRP, LBP, insulin, and HOMA-IR compared to lean individuals (p < 0.05) There were no changes in CRP as a result of exercise training. However, LBP and HOMA-IR were significantly reduced by exercise in the obese group (p < 0.05). Change in CRP over the 6-week intervention positively correlated with change in abundance of Erysipelotrichaceae (r = 0.610, p = 0.009), a microbe previously shown to be associated with metabolic syndrome. Change in abundance of Anaerostipes, a genus of known butyrate-producers, negatively correlated with change in LBP (r = -0.727, p = 0.007) and HOMA-IR (r = -0.471, p = 0.036). Both CRP and LBP levels after the intervention were negatively correlated with post fecal acetate, butyrate, and propionate levels (p < 0.01). CONCLUSIONS: Six weeks of aerobic exercise improved markers of insulin sensitivity and metabolic endotoxemia in obese individuals. These improvements may be related effects on the gut microbiota, as metabolic and inflammatory markers correlated with changes in several important microbial genera and post-intervention SCFAs.