Andrea Dunaif

Insulin/IGF-1 and TNF-α stimulate phosphorylation of IRS-1 at inhibitory Ser307 via distinct pathways

Serine/threonine phosphorylation of IRS-1 might inhibit insulin signaling, but the relevant phosphorylation sites are difficult to identify in cultured cells and to validate in isolated tissues. Recently, we discovered that recombinant NH2-terminal Jun kinase phosphorylates IRS-1 at Ser307, which inhibits insulin-stimulated tyrosine phosphorylation of IRS-1. To monitor phosphorylation of Ser307 in various cell and tissue backgrounds, we prepared a phosphospecific polyclonal antibody designated alphapSer307. This antibody revealed that TNF-alpha, IGF-1, or insulin stimulated phosphorylation of IRS-1 at Ser307 in 3T3-L1 preadipocytes and adipocytes. Insulin injected into mice or rats also stimulated phosphorylation of Ser307 on IRS-1 immunoprecipitated from muscle; moreover, Ser307 was phosphorylated in human muscle during the hyperinsulinemic euglycemic clamp. Experiments in 3T3-L1 preadipocytes and adipocytes revealed that insulin-stimulated phosphorylation of Ser307 was inhibited by LY294002 or wortmannin, whereas TNF-alpha-stimulated phosphorylation was inhibited by PD98059. Thus, distinct kinase pathways might converge at Ser307 to mediate feedback or heterologous inhibition of IRS-1 signaling to counterregulate the insulin response.

Prevalence and predictors of dyslipidemia in women with polycystic ovary syndrome

PURPOSE Women with polycystic ovary syndrome are hyperandrogenemic and insulin resistant, which are associated with alterations in circulating lipid and lipoprotein levels. We sought to determine the prevalence of, and risk factors for, lipid abnormalities in these women. SUBJECTS AND METHODS Non-Hispanic white women with polycystic ovary syndrome (n = 195) and ethnically matched control women (n = 62) had fasting blood obtained for hormone and lipid levels. Subjects were categorized by body mass index (nonobese <27 kg/m(2), obese > or =27 kg/m(2)), and analyses were adjusted for age. RESULTS Total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels increased significantly in obese women with polycystic ovary syndrome (n = 153) compared with obese control women (n = 35; mean difference in total cholesterol level = 29 mg/dL; 95% confidence interval [CI]: 14 to 45 mg/dL; P <0.001; mean difference in LDL-C level = 16 mg/dL; 95% CI: 4 to 30 mg/dL; P = 0.006). Similarly, total cholesterol and LDL-C levels increased significantly in nonobese women with polycystic ovary syndrome (n = 42) compared with nonobese control women (n = 27; mean difference in total cholesterol = 32 mg/dL; 95% CI: 13 to 52 mg/dL; P <0.001; mean difference in LDL-C level = 32 mg/dL; 95% CI: 15 to 52 mg/dL; P <0.001). In obese women, high-density lipoprotein cholesterol (HDL-C) and triglyceride levels increased significantly in women with polycystic ovary syndrome compared with control women (mean difference in HDL-C level = 6 mg/dL; 95% CI: 2 to 12 mg/dL; P = 0.002; mean difference in triglyceride level = 34 mg/dL; 95% CI: 1 to 77 mg/dL; P = 0.04). Differences in LDL-C and HDL-C levels, but not triglyceride levels, remained significant after adjusting for alcohol intake, smoking, and exercise. Although age, body mass index, and polycystic ovary syndrome status were significant predictors of lipid levels, these factors accounted for no more than 25% of the variance. CONCLUSIONS In this large study of non-Hispanic white women, elevations in LDL-C levels were the predominant lipid abnormality in women with polycystic ovary syndrome, independent of obesity. The characteristic dyslipidemia of insulin resistance was absent. Indeed, obese women with polycystic ovary syndrome had relatively elevated HDL-C levels, which may confer some protection against cardiovascular disease.

Consensus on women's health aspects of polycystic ovary syndrome (PCOS)

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in females with a high prevalence. The etiology of this heterogeneous condition remains obscure and its phenotype expression varies. Two, widely cited, previous ESHRE/ASRM-sponsored PCOS consensus workshops focused on diagnosis (published in 2004) and infertility management (published in 2008). The present third PCOS consensus paper summarizes current knowledge and identifies knowledge gaps regarding various womens health aspects of PCOS. Relevant topics addressed-all dealt with in a systematic fashion-include adolescence, hirsutism and acne, contraception, menstrual cycle abnormalities, quality of life, ethnicity, pregnancy complications, long-term metabolic and cardiovascular health and finally cancer risk. Additional, comprehensive background information is provided separately in an extended online publication.

INSULIN ACTION IN THE POLYCYSTIC OVARY SYNDROME

Research on insulin action in PCOS has been intensive after the identification of insulin resistance as a feature of the syndrome in 1980. It is now clear that PCOS is a metabolic as well as a reproductive disorder and an important cause of type 2 diabetes mellitus in women. The cellular and molecular mechanisms of insulin resistance in PCOS are distinct from those in other insulin resistance syndromes. Elucidating these mechanisms promises to provide considerable insight into insulin receptor signal specificity. Conversely, insulin resistance is now known to have an important role in the pathogenesis of the reproductive disturbances of PCOS. It is thought that one or several genetic defects may cause both the insulin resistance and reproductive abnormalities characteristic of PCOS.

Phenotype and genotype in polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is a common disorder in premenopausal women and is characterized by hyperandrogenic chronic anovulation. The cause is unknown. PCOS is associated with significant insulin resistance as well as with defects in insulin secretion. These abnormalities place these women at substantial risk for developing type 2 diabetes mellitus. A defect in insulin-mediated receptor autophosphorylation has been found in a substantial proportion of PCOS women. Both PCOS and the insulin resistance that accompanies it appear to have major genetic components. Family studies of PCOS have supported this, although they suffer from incomplete phenotyping of probands and first-degree relatives. The phenotype in males and nonreproductive age females is uncertain. Despite the shortcomings of the family studies of PCOS, they have consistently indicated familial clustering and suggested that the mode of inheritance is dominant. Our initial studies of 50 families of PCOS probands indicate that 24% of sisters are affected with PCOS. There also appears to be an intermediate phenotype of sisters with regular menstrual cycles who are hyperandrogenic per se (22% of sisters). Additionally, there appears to be a major familial defect, with 50% of first-degree relatives having glucose intolerance (impaired glucose tolerance by oral glucose tolerance test or type 2 diabetes mellitus). These findings suggest that hyperandrogenism in females and glucose intolerance may be genetic traits in PCOS kindreds. Systematic phenotyping will allow assignment of affected status for eventual linkage analysis.

Evidence for chromosome 2p16.3 polycystic ovary syndrome susceptibility locus in affected women of European ancestry.

CONTEXT A previous genome-wide association study in Chinese women with polycystic ovary syndrome (PCOS) identified a region on chromosome 2p16.3 encoding the LH/choriogonadotropin receptor (LHCGR) and FSH receptor (FSHR) genes as a reproducible PCOS susceptibility locus. OBJECTIVE The objective of the study was to determine the role of the LHCGR and/or FSHR gene in the etiology of PCOS in women of European ancestry. DESIGN This was a genetic association study in a European ancestry cohort of women with PCOS. SETTING The study was conducted at an academic medical center. PARTICIPANTS Participants in the study included 905 women with PCOS diagnosed by National Institutes of Health criteria and 956 control women. INTERVENTION We genotyped 94 haplotype-tagging single-nucleotide polymorphisms and two coding single-nucleotide polymorphisms mapping to the coding region of LHCGR and FSHR plus 20 kb upstream and downstream of the genes and test for association in the case control cohort and for association with nine quantitative traits in the women with PCOS. RESULTS We found strong evidence for an association of PCOS with rs7562215 (P = 0.0037) and rs10495960 (P = 0.0046). Although the marker with the strongest association in the Chinese PCOS genome-wide association study (rs13405728) was not informative in the European populations, we identified and genotyped three markers (rs35960650, rs2956355, and rs7562879) within 5 kb of rs13405728. Of these, rs7562879 was nominally associated with PCOS (P = 0.020). The strongest evidence for association mapping to FSHR was observed with rs1922476 (P = 0.0053). Furthermore, markers with the FSHR gene region were associated with FSH levels in women with PCOS. CONCLUSIONS Fine mapping of the chromosome 2p16.3 Chinese PCOS susceptibility locus in a European ancestry cohort provides evidence for association with two independent loci and PCOS. The gene products LHCGR and FSHR therefore are likely to be important in the etiology of PCOS, regardless of ethnicity.

The Inflammatory Gene Pathway Is Not a Major Contributor to Polycystic Ovary Snydrome

CONTEXT Although inflammation is clearly associated with obesity, diabetes, and insulin resistance, the role of chronic inflammation in the etiology of polycystic ovary syndrome (PCOS) is unclear. OBJECTIVE To determine whether chronic inflammation plays a causal role in the etiology of PCOS, we tested for an association between PCOS and genetic markers mapping to 80 members of the inflammatory pathway. DESIGN This was a case-control association study. SETTING The setting was an academic medical center. PATIENTS OR PARTICIPANTS A total of 905 index case patients with PCOS and 955 control women (108 intensively phenotyped subjects with normal androgen levels and regular menses and 847 minimally phenotyped subjects with regular menses and no history of PCOS). INTERVENTIONS Subjects were genotyped at single nucleotide polymorphisms mapping to 80 inflammatory genes. Logistic regression was used to test for an association between 822 single nucleotide polymorphisms and PCOS after adjustment for population stratification, body mass index, and/or age. In the index patients, we also tested for association with 11 quantitative traits (body mass index and testosterone, fasting insulin, fasting glucose, 2-hour postchallenge glucose, LH, FSH, total cholesterol, high-density lipoprotein, low-density lipoprotein, and triglyceride levels). MAIN OUTCOME MEASURES The evidence for an association with PCOS and with 11 quantitative traits was investigated. RESULTS Nominally significant evidence for an association was observed with MAP3K7, IKBKG, TNFRS11A, AKT2, IL6R, and IRF1, but no results remained statistically significant after adjustment for multiple testing. CONCLUSIONS Genetic variation in the inflammatory pathway is not a major contributor to the etiology of PCOS or related quantitative traits in women with PCOS.