Increased levels of fatty acids contributed to induction of hepatic CYP3A4 activity induced by diabetes - in vitro evidence from HepG2 cell and Fa2N-4 cell lines.

Accumulating evidences have shown that diabetes upregulated the function and expression of CYP3A4, but the mechanism remained unclear. In this study, HepG2 cells were incubated with serum from diabetic rats induced by streptozotocin, and the activity of CYP3A4 was measured by substrate metabolism. Results showed that incubation with diabetic serum significantly induced CYP3A4 activity in HepG2 cells. To identify the specific factors contributing to the regulation, the abnormally altered components in diabetic serum, including glucose, insulin, cholesterol, and free fatty acids were screened. It was found that only fatty acids concentration-dependently up-regulated CYP3A4 activity, and the induction by fatty acids was further confirmed in Fa2N-4 cells. Data from western blotting and QT-PCR showed that induction of CYP3A4 activity was associated with up-regulation of CYP3A4 protein and mRNA levels. In addition, effects of pharmacological inhibitors on fatty acid-induced CYP3A4 activity were studied. The results indicated that the induction of CYP3A4 activity by oleic acid may be partly via AMPK-, PKC-, and NF-κB-dependent pathways, whereas that by palmitic acid was possibly associated with the PKC-dependent pathway. In conclusion, the increased levels of fatty acids may be one of the reasons leading to the elevated function and expression of CYP3A4 under diabetic conditions.