Aerobic Capacity and Bile Acid Metabolism

Abstract

High aerobic capacity is strongly correlated to protection from a wide range of metabolic diseases. Bile acids are now recognized as potential players in protection against metabolic disease. We tested the hypothesis that human subjects with high aerobic fitness (>45 ml/kg/min) display differences in fecal bile acid species and total bile acid excretion compared to those with low or average aerobic fitness (45 ml/kg/min) display differences in fecal bile acid species and total bile acid excretion compared to those with low or average aerobic fitness (<35 ml/kg/min) (matched for age and body weight). We also evaluated if there were differences in circulating bile acid content. Healthy women ages 18 to 35 were recruited and screened for inclusion criteria by a VO2max treadmill test. A total of 20 women were enrolled in the study, n=10 in the high-fit group, n=10 in the low-fit group. Diet intake, activity level, stool, and blood were measured at baseline before receiving a 1-week standardized diet. After the 1-week standardized diet, stool and blood were again measured, and an Oral Glucose Tolerance Test (OGTT) and body composition scan (Dual-energy X-ray Absorptiometry) were performed. Contrary to our hypothesis, no differences in circulating or fecal bile acid content was found between the high- and low-fit women. Future research should consider using direct measurements of the rate-limiting enzyme in bile acid synthesis, CYP7a1, and also the utilization of a 24+ hour fecal collection in order to account for volume differences.