Exercise Reduces Intrahepatic Triglyceride And Improves Insulin Action In Adults With Nonalcoholic Fatty Liver Disease

Abstract

The effects of aerobic exercise (AE) alone without weight loss on reducing intrahepatic triglyceride content (IHTG) and improving insulin action in patients with nonalcoholic fatty liver disease (NAFLD, IHTG >5%) is unknown. PURPOSE: We determined the effects of 4 months of a minimum of 150min/wk of verified brisk walking (∼50% of VO2max) in previously sedentary, overweight (mean ± SE, BMI =27.7 ± 2.9) adults (age 21.0±2.2yrs) on IHTG and hepatic and skeletal muscle insulin sensitivity. METHODS: Participants were randomized to AE (N=12, 6 Male (M), 6 Female (F)) or control (C, N=6, 3M, 3 F) groups. At baseline and after 4 months of verified AE the following procedures were performed: 1) a euglycemic-hyperinsulinemic clamp procedure, in conjunction with isotope tracer([2H2]glucose) infusion, was conducted to assess hepatic and muscle insulin sensitivity and 2) proton magnetic resonance spectroscopy was performed to determine IHTG. Both groups maintained their normal ad-libitum diet and activities of daily living. RESULTS: Subjects in the AE completed 96% ± 2% of the recommended exercise sessions and averaged 225 ± 22min/wk of verified exercise. Subjects in the AE group were weight stable from baseline (105.9 ± 5.1kg) to 4 months (105.5±6.2kg) as well as the C group (113.8 ± 6.3kg vs. 114.2 ± 5.8kg). IHTG significantly (P<0.05) decreased (-15% ± 5%) in the AE group compared to a slight non-significant increase (5.6%±5%) in the C group resulting in a significant between group difference, P<0.05. Hepatic insulin sensitivity index, a function of hepatic glucose production rate and plasma insulin concentration, increased by 22 ±16% (p<0.001) after 4 months of AE compared to no change in the C group for a significant between group difference, P<0.05. Insulin-mediated muscle glucose uptake significantly increased in the AE (15 ± 14.2%) (p≤0.01), but not in the C group (2.0 ± 10.2%) resulting in a significant between group difference, P<0.05. CONCLUSIONS: In adults with NAFLD, aerobic exercise, independent of weight loss, is an effective treatment for reducing IHTG and improving insulin sensitivity in both skeletal muscle and liver.