[Decrease of gene expression of glycerophosphate dehydrogenase by dexamethasone in differentiated 3T3-F442A cells: antagonism with insulin and antiglucocorticoid RU38486].

Preadipocyte subclones derived from mouse 3T3 cells differentiate into adipocytes; this differentiation is characterized by an increased activity of numerous enzymes required for triglyceride synthesis and/or mobilization. Among these enzymes, the role of glycerophosphate dehydrogenase in the differentiation process has been previously reported. In the present work, we studied the hormonal regulation of glycerophosphate dehydrogenase gene expression (G3PDH) in differentiated 3T3-F442A adipocytes. Dexamethasone (DEX) elicited a 50% decrease in both mRNA content and specific activity of G3PDH. This effect was due to a posttranscriptional event since DEX shortened the half life of the mRNA, whereas it did not modify the transcription rate of this gene. The DEX effect is specific to G3PDH, since the expression of another adipose-specific gene, namely adipsin, is not modified by DEX treatment. Insulin counteracts the inhibitory effect of DEX, mainly by stabilizing the mRNA encoding for G3PDH. The antiglucocorticoid RU38486 is able to reverse DEX inhibition. Latter phenomenon suggests that DEX action on G3PDH gene expression could be mediated by glucocorticoid receptors.