PT  - JOURNAL ARTICLE
AU  - I De Waziers
AU  - M Garlatti
AU  - J Bouguet
AU  - P H Beaune
AU  - R Barouki
TI  - Insulin down-regulates cytochrome P450 2B and 2E expression at the post-transcriptional level in the rat hepatoma cell line.
DP  - 1995 Mar 01
TA  - Molecular Pharmacology
PG  - 474--479
VI  - 47
IP  - 3
4099  - http://molpharm.aspetjournals.org/content/47/3/474.short
4100  - http://molpharm.aspetjournals.org/content/47/3/474.full
SO  - Mol Pharmacol1995 Mar 01; 47
AB  - Cytochromes P450 (P450s) are inducible drug-metabolizing enzymes involved in the metabolism of numerous endogenous and exogenous substrates. The regulation of some of these enzymes during experimental diabetes has been reported, but the direct involvement of insulin and the mechanism of its action remain unclear. The aim of our work was to study the effects of insulin on P450 2B and 2E expression in differentiated Fao hepatoma cells. Exposure of the cells to 0.1 microM insulin caused 60% and 80% decreases in the steady state levels of P450 2B and 2E proteins, respectively, within 24 hr. Before this, a rapid decrease in the corresponding messages was observed. Indeed, 5-6 hr of insulin treatment produced 80 and 50% decreases in P450 2B and 2E mRNA levels, respectively. Nuclear run-on transcription and mRNA turnover studies were performed to determine the mechanism (transcriptional and/or post-transcriptional) by which insulin modulated these mRNA levels. From our results, it can be concluded that insulin down-regulates the expression of P450 2B by shortening the half-life of its mRNA (half-lives of 6.9 hr without insulin and 3.6 hr with insulin), whereas it down-regulates the expression of P450 2E both by weak repression of the transcription rate (-30%) and, in particular, by acceleration of its mRNA turnover (half-lives of 8.5 hr without insulin and 3.3 hr with insulin).