Pretranslational activation of cytochrome P450IIE during ketosis induced by a high fat diet.

Ethanol-inducible cytochrome P450 (P450IIE) is reported to be induced by ketosis. In the present study, the effects of a high fat diet on P450IIE induction and the relationship between ketone body concentration and P450IIE induction were studied by the following: 1) measurement of the activity of aniline hydroxylase, 2) immunoblot analysis for P450IIE protein, and 3) Northern blot analysis for P450IIE mRNA. The enzyme activities (aniline hydroxylase) in hepatic and renal microsomes were elevated about 2-3-fold by feeding with a high fat diet for 3 days. The increases in enzyme activities were also accompanied by 3-fold increases in immunoreactive P450IIE protein and its mRNA. In contrast, no differences were observed for the catalytic activities of N-alkoxyresorufin dealkylases or the amounts of immunoreactive P450IA and P450IIC, indicating a specific induction of P450IIE by high fat feeding. Furthermore, the increases in the levels of P450IIE mRNA correlated positively (r = 0.73) with plasma concentrations of acetoacetate and beta-hydroxybutyrate but not with that of acetone, which induces P450IIE without changing its mRNA level. Our data thus indicated that P450IIE induction during the ketosis of a high fat feeding appears to be due to pretranslational activation and that is similar to the induction mechanism of fasted and diabetic animals.