In vitro exposure to copper influences lipid metabolism in hepatocytes from grass carp (Ctenopharyngodon idellus)

In the present study, three different copper (Cu) concentrations (control, 10 and 100 mu M, respectively) and three incubation times (24, 48 and 96 h) were chosen to assess in vitro effect of Cu on lipid metabolism in hepatocytes of grass carp Ctenopharyngodon idellus. Increased glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and carnitine palmitoyltransferase I activities were observed in hepatocytes with increasing Cu concentration and exposure duration. Cu decreased mRNA levels of several lipogenic and lipolytic genes at 24 h. However, at 48 h, Cu down-regulated the process of lipogenesis but up-regulated that of lipolysis. The Cu-driven up-regulation of lipolytic genes was maintained after 96 h and accompanied by a decreased intracellular triglyceride accumulation, while no effect on lipogenic genes was shown. Thus, 96-h Cu exposure induced lipid depletion, possibly due to the up-regulation of lipolysis. Although in this process, lipogenesis might be up-regulated, it was not enough to compensate lipid consumption. Our study represents the first approach to concentration- and time-dependent in vitro effects of Cu on lipid metabolism of fish hepatocytes and provides new insights into Cu toxicity in fish at both enzymatic and molecular levels.