Randomized trial of exercise effect on intrahepatic triglyceride content and lipid kinetics in nonalcoholic fatty liver disease

Abstract

Nonalcoholic fatty liver disease (NAFLD) and alterations in hepatic lipoprotein kinetics are common metabolic complications associated with obesity. Lifestyle modification involving diet-induced weight loss and regular exercise decreases intrahepatic triglyceride (IHTG) content and very low density lipoprotein (VLDL) triglyceride (TG) secretion rate. The aim of this study was to evaluate the weight loss-independent effect of following the physical activity guidelines recommended by the Department of Health and Human Services on IHTG content and VLDL kinetics in obese persons with NAFLD. Eighteen obese people (body mass index [BMI]: 38.1 ± 4.6 kg/m(2)) with NAFLD were randomized to 16 weeks of exercise training (45%-55% VO(2peak) , 30-60 minutes × 5 days/week; n = 12) or observation (control; n = 6). Magnetic resonance spectroscopy and stable isotope tracer infusions in conjunction with compartmental modeling were used to evaluate IHTG content and hepatic VLDL-TG and apolipoprotein B-100 (apoB-100) secretion rates. Exercise training resulted in a 10.3% ± 4.6% decrease in IHTG content (P < 0.05), but did not change total body weight (103.1 ± 4.2 kg before and 102.9 ± 4.2 kg after training) or percent body fat (38.9% ± 2.1% before and 39.2% ± 2.1% after training). Exercise training did not change the hepatic VLDL-TG secretion rate (17.7 ± 3.9 μmol/min before and 16.8 ± 5.4 μmol/min after training) or VLDL-apoB-100 secretion rate (1.5 ± 0.5 nmol/min before and 1.6 ± 0.6 nmol/min after training).

Conclusion: Following the Department of Health and Human Services recommended physical activity guidelines has small but beneficial effects on IHTG content, but does not improve hepatic lipoprotein kinetics in obese persons with NAFLD.

Trial registration: ClinicalTrials.gov NCT00771108.

Figure 1

Diagram of study subject flow.

Figure 2

Intrahepatic triglyceride content in the Control (n = 6) and Exercise (n = 11) groups before and after the 16 week intervention. Data are means ± SEM. ANCOVA revealed a significant group x time interaction (p = 0.044).

Figure 3

VLDL-TG secretion rate (A) and VLDL-ApoB-100 secretion rate (B) before (white bars) and after (black bars) intervention in the Control and Exercise groups. Relative contribution of non-systemic fatty acids (gray speckled bars) and systemic fatty acids (white speckled bars) to secreted VLDL-TG (C). Data are means ± SEM.