Insulin augmentation of 17alpha-hydroxylase activity is mediated by phosphatidyl inositol 3-kinase but not extracellular signal-regulated kinase-1/2 in human ovarian theca cells.
Polycystic ovary syndrome, characterized by hyperandrogenism and chronic anovulation, is frequently associated with insulin resistance. Ample evidence implicates a role for insulin in the genesis of ovarian hyperandrogenism. The objective of this study was to begin to define the intracellular signaling pathway(s) that mediates insulin regulation of 17alpha-hydroxylase activity in human ovarian theca cells. Third-passage theca cells, isolated from the ovaries of regularly cycling premenopausal women, were used. Insulin alone had no effect on 17alpha-hydroxylase activity or CYP17 mRNA expression but required costimulation with forskolin. At the insulin concentration used (10 ng/ml), a neutralizing antibody to the insulin receptor (but not an antibody to the type I IGF receptor) blocked the insulin stimulation of 17alpha-hydroxylase activity, demonstrating that the effects were mediated by the insulin receptor. Insulin stimulated both phosphatidylinositol-3-kinase (PI3-kinase) and extracellular signal-regulated kinase-1/2 (MAPK) pathways. Specific inhibition of MAPK kinase (MEK) with PD98059 or I0126 did not decrease the 17alpha-hydroxylase activity stimulated by forskolin or forskolin plus insulin. In contrast, the PI3-kinase inhibitor LY294002 completely blocked insulin-stimulated 17alpha-hydroxylase activity. Our data demonstrate that insulin stimulates PI3-kinase and extracellular signal-regulated kinase-1/2 activities in human theca cells, but only PI3-kinase mediates the insulin augmentation of forskolin-stimulated 17alpha-hydroxylase activity.
D000728:Androgens / Q000096:biosynthesis; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011085:Polycystic Ovary Syndrome / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism*; D013799:Theca Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*
D000728:Androgens; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007004:Hypoglycemic Agents; D007328:Insulin; D012333:RNA, Messenger; D005576:Colforsin; D013254:Steroid 17-alpha-Hydroxylase; D019869:Phosphatidylinositol 3-Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one