Enhanced mitogenic signaling in skeletal muscle of women with polycystic ovary syndrome.
Insulin resistance in polycystic ovary syndrome (PCOS) results from a postbinding defect in signaling. Insulin receptor and insulin receptor substrate (IRS)-1 serine hyperphosphorylation by an unidentified kinase(s) contributes to this defect. We investigated whether insulin resistance is selective, affecting metabolic but not mitogenic pathways, in skeletal muscle as it is in cultured skin fibroblasts in PCOS. Extracellular signal-regulated kinase (ERK)1/2 activation was increased in skeletal muscle tissue and in cultured myotubes basally and in response to insulin in women with PCOS compared with control women. Mitogen-activated/extracellular signal-regulated kinase kinase (MEK)1/2 was also activated in PCOS, whereas p38 mitogen-activated protein kinase phosphorylation and signaling from the insulin receptor to Grb2 was similar in both groups. The activity of p21Ras was decreased and Raf-1 abundance increased in PCOS, suggesting that altered mitogenic signaling began at this level. MEK1/2 inhibition reduced IRS-1 Ser312 phosphorylation and increased IRS-1 association with the p85 subunit of phosphatidylinositol 3-kinase in both groups. We conclude that in PCOS skeletal muscle, 1) mitogenic signaling is enhanced in vivo and in culture, 2) ERK1/2 activation inhibits association of IRS-1 with p85 via IRS-1 Ser312 phosphorylation, and 3) ERK1/2 activation may play a role in normal feedback of insulin signaling and contribute to resistance to insulin's metabolic actions in PCOS.
Corbould
Anne
A
Division of Endocrinology, Metabolism and Molecular Medicine, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Chicago, IL 60611, USA.
Zhao
Haiyan
H
Mirzoeva
Salida
S
Aird
Fraser
F
Dunaif
Andrea
A
D000328:Adult; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D020935:MAP Kinase Signaling System / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D010750:Phosphoproteins / Q000502:physiology; D010766:Phosphorylation; D011085:Polycystic Ovary Syndrome / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000502:physiology; D016283:Proto-Oncogene Proteins p21(ras) / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D002070:Butadienes; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; D009570:Nitriles; D010750:Phosphoproteins; C113580:U 0126; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D016283:Proto-Oncogene Proteins p21(ras)