Seed oil of Rosa roxburghii Tratt against non-alcoholic fatty liver disease in vivo and in vitro through PPARα/PGC-1α-mediated mitochondrial oxidative metabolism

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD), characterized by hepatic steatosis and hepatocyte injury, is an obesity-induced metabolic dysregulation with few available therapeutic options. Enhancement of the mitochondrial function was considered as an effective treatment for NALFD. Unsaturated fatty acids (UFAs) have been shown to have beneficial effects on metabolic syndrome disease such as hyperlipidemia, coronary artery disease and cardiovascular diseases. The seed oil of Rosa roxburghii Tratt (ORRT) was of high quality in terms of its high amount of unsaturated fatty acids. However, the effects of ORRT on NALFD have not been reported so far.

PURPOSE

The study aimed to evaluate the protective effects and molecular mechanism of ORRT for the treatment of NAFLD in vivo and in vitro.

METHODS

The beneficial effects, especially improving the mitochondrial function, and the potential mechanism of ORRT on NAFLD were studied both in vivo and in vitro. Lipid levels were determined by triglyceride (TG), total cholesterol (TC), and Oil Red O staining. Oxidative stress and inflammation were assessed by detecting antioxidant enzyme activity, MDA content, and ELISA assay. Blood TG, TC, HDL-c and LDL-c levels were measured in HFD mice. Western blot analyses were used to determine the levels of the protein involved in fatty acid oxidation, oxidative metabolism, and mitochondria biogenesis and function. The mitochondrial membrane potential level was measured by JC-1 staining to teste the effect of ORRT on mitochondrial function in vitro. GW6471 (inhibitor of PPARα) was used to confirm the relationship between PPARα and PGC-1α.

RESULTS

ORRT significantly restrained NAFLD progression by attenuating lipid accumulation, oxidative stress and inflammatory response. Furthermore, ORRT upregulated thermogenesis-related gene expressions, such as uncoupling protein 1 (UCP1) and p38 mitogen-activated protein kinase (p38 MAPK). The results showed that the expression of key genes involved in fatty acid oxidation (e.g., CPT-1α, ACADL, PPARα) and in mitochondrial biogenesis and function (e.g., TFAM, NRF1, PGC-1α, and COX IV) was significantly increased. Together with the observed MMP improvement, these findings suggested that ORRT activated the mitochondrial oxidative pathway. Additionally, GW6471 inhibited the ORRT on promoting the expression of PGC-1α, CPT-1α, and ACADL. In conclusion, ORRT possessed the potential to prevent lipid accumulation via the PPARα/PGC-1α signaling pathway, which could be developed as a natural health-promoting oil against NAFLD.

High-Fructose Intake Impairs the Hepatic Hypolipidemic Effects of a High-Fat Fish-Oil Diet in C57BL/6 Mice

BACKGROUND

Overnutrition of saturated fats and fructose is one of the major factors for the development of nonalcoholic fatty liver disease. Because omega-3 polyunsaturated fatty acids (n-3fa) have established lipid lowering properties, we tested the hypothesis that n-3fa prevents high-fat and fructose-induced fatty liver disease in mice.

METHODS

Male C57BL/6J mice were randomly assigned to one of the following diet groups for 14 weeks: normal diet (ND), high-fat lard-based diet (HFD), HFD with fructose (HFD + Fru), high-fat fish-oil diet (FOD), or FOD + Fru.

RESULTS

Despite for the development of obesity and insulin resistance, FOD had 65.3% lower (P < 0.001) hepatic triglyceride levels than HFD + Fru, which was blunted to a 38.5% difference (P = 0.173) in FOD + Fru. The lower hepatic triglyceride levels were associated with a lower expression of lipogenic genes LXRα and FASN, as well as the expression of genes associated with fatty acid uptake and triglyceride synthesis, CD36 and SCD1, respectively. Conversely, the blunted hypotriglyceride effect of FOD + Fru was associated with a higher expression of CD36 and SCD1.

CONCLUSIONS

During overnutrition, a diet rich in n-3fa may prevent the severity of hepatic steatosis; however, when juxtaposed with a diet high in fructose, the deleterious effects of overnutrition blunted the hypolipidemic effects of n-3fa.