Exercise Training Independent of Intensity Lowers Plasma Bile Acids in Prediabetes

ABSTRACT Introduction People with obesity have high circulating bile acids (BA). Although aerobic fitness favors low circulating BA, the effect of training intensity before clinically meaningful weight loss on BA is unclear. This study aimed to test the hypothesis that 2 wk of interval (INT) versus continuous (CONT) exercise would lower plasma BA in relation to insulin sensitivity. Methods Twenty-three older adults with prediabetes (ADA criteria) were randomized to 12 work-matched bouts of INT ( n = 11, 60.3 ± 2.4 yr, 32.1 ± 1.2 kg·m −2 ) at 3 min at 50% HR peak and 3 min at 90% HR peak or CONT ( n = 12, 60.8 ± 2.4 yr, 34.0 ± 1.7 kg·m −2 ) at 70% HR peak cycling training for 60 min·d −1 over 2 wk. A 180-min 75-g oral glucose tolerance test (OGTT) was performed to assess glucose tolerance (tAUC), insulin sensitivity (Siis), and metabolic flexibility (RER postprandial –RER fast ; indirect calorimetry). BA ( n = 8 conjugated and 7 unconjugated) were analyzed at 0, 30, and 60 min of the OGTT. Anthropometrics and fitness (V̇O 2peak ) were also assessed. Results INT and CONT comparably reduced body mass index (BMI; P < 0.001) and fasting RER ( P < 0.001) but raised insulin sensitivity ( P = 0.03). INT increased V̇O 2peak as compared with CONT ( P = 0.01). Exercise decreased the unconjugated BA chenodeoxycholic acid iAUC 60min ( P < 0.001), deoxycholic acid iAUC 60min ( P < 0.001), lithocholic acid iAUC 60min ( P < 0.001), and glycodeoxycholic acid (GCDCA) iAUC 60min ( P < 0.001). Comparable reductions were also seen in the conjugated BA hyodeoxycholic acid iAUC 60min ( P = 0.01) and taurolithocholic acid iAUC 60min ( P = 0.007). Increased V̇O 2peak was associated with lowered UDCA 0min ( r = −0.56, P = 0.02) and cholic acid iAUC 60min ( r = −0.60, P = 0.005), whereas reduced BMI was related to higher GDCA 0min ( r = 0.60, P = 0.005) and GCDCA 0min ( r = 0.53, P = 0.01). Improved insulin sensitivity correlated with lower GCDCA iAUC 60min ( r = −0.45, P = 0.03) and GDCA iAUC 60min ( r = −0.48, P = 0.02), whereas increased metabolic flexibility was related to deoxycholic acid iAUC 60min ( r = 0.64, P = 0.004) and GCDCA iAUC 60min ( r = 0.43, P = 0.05). Conclusions Short-term training lowers some BA in relation to insulin sensitivity independent of intensity.