Lifestyle intervention and fatty liver disease: the importance of both disrupting inflammation and reducing visceral fat

Dietary capsaicin prevents nonalcoholic fatty liver disease through transient receptor potential vanilloid 1-mediated peroxisome proliferator-activated receptor δ activation

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic lipid deposition and coincides often with cardiometabolic diseases. Several dietary factors attenuate NAFLD. Here, we report beneficial effects of chronic dietary capsaicin intake on NAFLD which is mediated by the transient receptor potential vanilloid 1 (TRPV1) activation. The results showed that TRPV1 activation by capsaicin reduced free fatty acids (FFAs) induced the intracellular lipid droplets in HepG2 cells and prevented fatty liver in vivo. Chronic dietary capsaicin promoted lipolysis by increasing hepatic phosphorylated hormone-sensitive lipase (phospho-HSL), carnitine palmitoyltransferase 1 (CPT1), and peroxisome proliferator-activated receptor δ (PPARδ) in wild-type (WT) mice. This effect was absent in TRPV1(-/-) mice. Dietary capsaicin did not affect lipogenesis, as indicated by the detection of hepatic fatty acid synthase (FAS), sterol regulatory element-binding protein-1 (SREBP-1), PPARα, and liver X receptor (LXR) in mice. Importantly, TRPV1 causes PPARδ activation which significantly increased the expression of autophagy-related proteins, such as light chain 3 (LC3)II, Beclin1, Atg5, and Atg7 in HepG2 cells. In the in vivo study, TRPV1 activation by dietary capsaicin enhanced hepatic PPARδ and autophagy-related proteins and reduced hepatic enzymes and inflammatory factor in WT but not TRPV1(-/-) mice. TRPV1 activation by dietary capsaicin prevents NAFLD through PPARδ-dependent autophagy enhancement in mice. Dietary capsaicin may represent a beneficial intervention in populations at high risk for NAFLD.

TRPV1 activation prevents nonalcoholic fatty liver through UCP2 upregulation in mice

Nonalcoholic fatty liver is characterized by the fatty deformation and lipid deposition of hepatic parenchymal cells that are associated with cardiometabolic diseases. In this study, we report the effect of capsaicin on its receptor, transient receptor potential vanilloid 1 (TRPV1) cation channel, in preventing fatty liver formation. Functional TRPV1 has been detected in hepatocytes and liver tissues. TRPV1 activation by capsaicin reduced lipid accumulation and triglyceride level in the liver from wild-type (WT) mice. However, these effects were absent in the liver from TRPV1(-/-) mice. Chronic dietary capsaicin increased the hepatic uncoupling protein 2 (UCP2) expression in WT but not in TRPV1(-/-) mice (P < 0.01). We conclude that TRPV1 long-time activation might prevent high-fat diet-induced fatty liver in mice through upregulation of hepatic UCP2. Dietary capsaicin may represent a promising intervention in populations at high risk for fatty liver.

NAFLD, Estrogens, and Physical Exercise: The Animal Model

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.

NAFLD, Estrogens, and Physical Exercise: The Animal Model

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.