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 (BMI: 38.1 ± 4.6 kg/m2) with NAFLD were randomized to 16 weeks of exercise training (45-55% V̇O2peak, 30-60 min × 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). Conclusions: 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.

The benefits of exercise for patients with non-alcoholic fatty liver disease

“…It is generally accepted that regular exercise leads to non-significant or small amounts of weight loss, but there are multiple benefits nonetheless. Human data clearly demonstrate that regular exercise itself reduces liver fat and can do so in the absence of clinically significant weight loss [4][5][6][7]. These data are supported by cross-sectional analyses which collectively demonstrate an inverse relationship between physical activity, physical fitness and NAFLD [8].…”

“…With respect to aerobic exercise, these guidelines promote moderate-intensity cardiorespiratory exercise training for ‡30 min on at least 5 days per week, or vigorous cardiorespiratory exercise training for ‡20 min on 3 days per week, or a combination of both and align with global recommendations for health, fitness and disease prevention [10]. Exercise interventions meeting these guidelines consistently demonstrate reduction in liver fat of 10-43% in patients with NAFLD [5,6,[11][12][13][14][15][16].…”

Exercise Training as Treatment of Nonalcoholic Fatty Liver Disease

“…Nine randomized control trials and four uncontrolled studies have investigated the effects of aerobic training in NAFLD (Table 1) [9][10][11][19][20][21][22][23][24][25][26][27][28]. All of the studies included at least one aerobic training experimental group, with three studies containing multiple aerobic training groups of differing exercise intensities [11,22,24].…”

“…While weight loss has remained fundamental to disease management, the benefits of exercise extend beyond weight loss alone. Exercise improves NAFLD independent of weight loss, however, the optimal exercise dose and pathophysiologic mechanisms by which exercise confers improvement in NAFLD remains unknown [9][10][11][12]. The practice guidelines for the management of NAFLD of the American Association for the Study of Liver Diseases (AASLD) recommends exercise; however, no specific approach or duration of exercise is otherwise detailed for practitioners [13].…”

NAFLD therapy and monitoring disease progression

“…58,59 Exercise Exercise may improve insulin sensitivity and hepatic steatosis, regardless of weight loss. 60 All patients should be advised to carry out of 150-300 minutes of moderately-intense physical exercise per week in 3-5 sessions. 46,57 The volume of exercise is an important factor and it has been shown that 250 minutes of weekly exercise was more effective than 150 minutes.…”