Insulin enhances the transcription of luteinizing hormone-β gene

Objective Hyperinsulinemia and insulin resistance are implicated in the pathophysiology of polycystic ovary syndrome, a condition associated with elevated levels of LH. We tested the hypothesis that insulin enhances the transcriptional activity of LHβ promoter. Study design We transfected the gonadotrope cell line LβT2 with a plasmid that expresses the proximal promoter of LHβ gene upstream of luciferase, and determined insulin effect on endogenous LHβ mRNA. Results We found that insulin stimulated (2-4 fold) the activity of this promoter in a time- and concentration-dependent manner. Accordingly, insulin up-regulated the level of LHβ mRNA. In contrast, insulin had no significant effect on GnRH-dependent LHβ expression. The expression of Egr-1 and SF-1, which are essential for transcription of LHβ gene, was unchanged by insulin. Conclusion Insulin enhances the transcription of LHβ gene. This modulation may contribute to the pathophysiology of polycystic ovary syndrome.