No abstract

Non-alcoholic fatty liver disease (NAFLD) is often linked with impaired hepatic autophagy. Here, we studied the alterations in hepatocellular autophagy by high cholesterol and high-fat diet (HC-HF) diet in C57BL/6J mice, and by palmitic acid (PA), in AML-12 and HepG2 cells. Further, we analysed role of Trigonelline (TG), a plant alkaloid, in preventing NAFLD, by modulating autophagy. For this, C57BL/6J mice were fed with Standard Chow (SC) or HC-HF diet, with and without TG for 16 weeks. In-vitro; AML-12 cells and HepG2 cells, were exposed to PA with and without TG, for 24 h. Cellular events related to autophagy, lipogenesis, and lipo-toxicity were studied. The HC-HF diet fed mice showed hepatic autophagy blockade, increased triglycerides and steatosis. PA exposure to AML-12 cells and HepG2 cells induced impaired autophagy, ER stress, resulting in lipotoxicity. TG treatment in HC-HF fed mice, restored hepatic autophagy, and prevented steatosis. TG treated AML-12, and HepG2 cells exposed to PA showed autophagy restoration, and reduced lipotoxicity, however, these effects were diminished in Atg7-/- HepG2 cells, and in the presence of chloroquine. This study shows that HC-HF diet-induced impaired autophagy, and steatosis is prevented by TG, which attributes to its novel mechanism in treating NAFLD.

The aim of the present investigation was to study the events associated with palmitic acid induced metabolic and lipotoxic changes in human hepatoma cells (Hep3B, Huh7 and HepG2). The cells were lipidoverloaded with varied concentrations of saturated fatty acid ( palmitic acid). It was observed that (a) SFA induced significant metabolic changes including CD36/FAT, SREBP1, PPARγ and SCD1 upregulation and decreased Mttp levels in HepG2 and Huh7 cells but not in Hep3B cells; (b) the toxic manifestations including changes in Ca 2+ levels, mitochondrial dysfunction and activation of the PERK-eIF2α-CHOP pathway due to SFA were more pronounced in Huh7 and Hep3B cells as compared to HepG2 cells; (c) induction of CYP2E1 and oxidative stress by SFA was observed in all three hepatoma cells. Interestingly, CYP2E1 overexpressing cells (E47 cells) were found to be significantly sensitized towards lipotoxicity; and (d) metabolic and toxic manifestations including altered blood biochemistry, ER stress and CYP2E1 induction were evident in C57BL/6J mice fed with a diet rich in cholesterol and saturated fatty acids (2% cholesterol/12% SFA-HC/HF) for 16 weeks (the model used to confirm the key events taking place in the in vitro system). Histopathological analysis of livers of HC/HF fed mice showed micro-and macro-vesicular steatosis, hepatocyte ballooning, infiltration of neutrophils and prominence of Kupffer cells. In conclusion our data suggest that palmitic acid alters lipid metabolism, causes oxidative stress and disturbs the intracellular Ca 2+ balance that terminates in CYP2E1 induction, ER stress and lipoapoptosis. † Electronic supplementary information (ESI) available. See