Exercise and fat accumulation in the human liver. Curr Opin Lipidol

Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
Current opinion in lipidology (Impact Factor: 5.66). 12/2010; 21(6):507-17. DOI: 10.1097/MOL.0b013e32833ea912
Source: PubMed


Fat accumulation in the liver is strongly associated with metabolic dysfunction. Regular exercise improves many cardiometabolic risks factors; however, its effect on intrahepatic triglyceride (IHTG) content remains elusive. This article summarizes available data regarding the effects of exercise on IHTG.
Several but not all observational studies report negative associations of habitual physical activity and cardiorespiratory fitness with IHTG and the prevalence of fatty liver. Aerobic exercise training in combination with hypocaloric diet reduces IHTG by a considerable amount (20-60%), even when weight loss is mild (<5%); hence weight loss per se may not be a critical factor. Longitudinal studies involving exercise training without dietary restriction and no weight loss demonstrate that increased cardiorespiratory fitness and reduced intra-abdominal adiposity are not invariably associated with liver fat depletion, whereas relatively large exercise-induced reductions in IHTG content (20-40%) can occur even in the absence of changes in body weight, body composition, or visceral adipose tissue. Although the majority of studies have examined aerobic training, resistance exercise has also been shown to be inversely associated with the prevalence of fatty liver in humans and effectively reduces IHTG content in animals.
Exercise does hold promise as an effective treatment for hepatic steatosis; this field of research is still in its infancy, and there is much more to be learned.

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    • "However, liver triglyceride levels in trained groups were significantly lower than control groups. In accordance with this finding, previous studies indicated that resistance training could reduce liver fat content [43]. For example, significant reduction of liver fat was observed in patients with non-alcoholic fatty liver after 8 week resistance training a long with improve in glucose metabolism [44]. "
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    ABSTRACT: Type 1 diabetes mellitus is associated with a high risk for early atherosclerotic complications. Altered lipids and lipoprotein metabolism in chronic diabetes mellitus is associated with pathogenesis of atherosclerosis and other cardiovascular diseases. The aim of this study was to investigate the effects of 4 weeks resistance training on plasma lipid profile, fatty acid binding protein (FABP) 4 and apolipoprotein (apo) A-I levels in type 1 diabetic rats. Thirty two male Wister rats (12-14 weeks old) were randomly divided into four groups: non-diabetic control; non-diabetic trained; diabetic control; diabetic trained. The rats in training groups were subjected to a resistance training program (3 days/wk, for 4 wk) consisted of climbing a ladder carrying a load suspended from the tail. Diabetic inducing increased plasma apoA-I and decreased FABP4 levels compared with non-diabetic control group (respectively, P = 0.001 & P = 0.041). After 4 weeks' resistance training, plasma levels of apoA-I and FABP4 in the diabetic trained rats were significantly higher compared with the diabetic control group (respectively, P = 0.003 & P = 0.017). Plasma HDL-C level in diabetic trained group was higher than diabetic control group (P = 0.048). Liver triglycerides concentrations were significantly lower in both trained (non-diabetic and diabetic) groups compared with their control groups (respectively, P = 0.041 and P = 0.002). These data indicated that resistance training may be an efficient intervention strategy to increase plasma apoA-I, HDL-C and FABP4 concentrations, along with decreases liver triglycerides in streptozotocin induced diabetic rats. Further research is needed to elucidate physiological significance of circulating FABP4 levels.
    Journal of Diabetes and Metabolic Disorders 03/2014; 13(1):41. DOI:10.1186/2251-6581-13-41
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    • "The effect of exercise on IHTG content has recently attracted much scientific interest in light of the apparent detrimental metabolic effects of excessive liver fat accumulation. Although the results from a few studies in human subjects are promising, as exercise appears to reduce IHTG [11], the importance of the factors highlighted herein on the basis of studies in animals has never been evaluated in man. Future studies should at least control for—in order to avoid confounding—or directly investigate the role of these factors in affecting the exercise-induced changes in liver fat content. "
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    ABSTRACT: An increase in intrahepatic triglyceride (IHTG) content is the hallmark of nonalcoholic fatty liver disease (NAFLD) and is strongly associated with insulin resistance and dyslipidemia. Although regular aerobic exercise improves metabolic function, its role in regulating fat accumulation in the liver is incompletely understood, and human data are scarce. Results from exercise training studies in animals highlight a number of potential factors that could possibly mediate the effect of exercise on liver fat, but none of them has been formally tested in man. The effect of exercise on IHTG content strongly depends on the background diet, so that exercise is more effective in reducing IHTG under conditions that favor liver fat accretion (e.g., when animals are fed high-fat diets). Concurrent loss of body weight or visceral fat does not appear to mediate the effect of exercise on IHTG, whereas sex (males versus females), prandial status (fasted versus fed), and duration of training, as well as the time elapsed from the last bout of exercise could all be affecting the observed exercise-induced changes in IHTG content. The potential importance of these factors remains obscure, thus providing a wide array of opportunities for future research on the effects of exercise (and diet) on liver fat accumulation.
    Journal of nutrition and metabolism 01/2012; 2012(1):827417. DOI:10.1155/2012/827417
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    • "On the whole, it seems that postmenopausal women with high levels of physical activity have lower body and abdominal fat and are less likely to gain fat (total and abdominal) during menopause than those with lower levels of physical activity [81]. Endurance training has been reported to be very effective in reducing intrahepatic triglycerides content in human (for a recent review see [103]). More recently, a 12-month intensive lifestyle intervention in patients with type 2 diabetes has been reported to reduce hepatic steatosis by as much as 25% [104]. "
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    ABSTRACT: One segment of the population that is particularly inclined to liver fat accumulation is postmenopausal women. Although nonalcoholic hepatic steatosis is more common in men than in women, after menopause there is a reversal in gender distribution. At the present time, weight loss and exercise are regarded as first line treatments for NAFLD in postmenopausal women, as it is the case for the management of metabolic syndrome. In recent years, there has been substantial evidence coming mostly from the use of the animal model, that indeed estrogens withdrawal is associated with modifications of molecular markers favouring the activity of metabolic pathways ultimately leading to liver fat accumulation. In addition, the use of the animal model has provided physiological and molecular evidence that exercise training provides estrogens-like protective effects on liver fat accumulation and its consequences. The purpose of the present paper is to present information relative to the development of a state of NAFLD resulting from the absence of estrogens and the role of exercise training, emphasizing on the contribution of the animal model on these issues.
    Journal of nutrition and metabolism 01/2012; 2012(3):914938. DOI:10.1155/2012/914938
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