Functional analysis of rare anti-Müllerian hormone protein-altering variants identified in women with PCOS.

Recently, rare heterozygous AMH protein-altering variants were identified in women with polycystic ovary syndrome (PCOS), causing reduced anti-Müllerian hormone (AMH) signaling. However, the exact functional mechanism remains unknown. Here, we analyzed the processing, secretion, and signaling of these AMH variants. Functional analysis of six PCOS-specific AMH variants (V12G, P151S, P270S, P352S, P362S, H506Q) and one control-specific variant (A519V) was performed in the mouse granulosa cell-line KK-1. Human (h) AMH-151S and hAMH-506Q have ∼90% decreased AMH signaling compared to wild-type (wt) AMH signaling. Coexpression of hAMH-151S or hAMH-506Q with wt-hAMH dose-dependently inhibited wt-hAMH signaling. Western blotting revealed that hAMH-151S and hAMH-506Q proteins were detected in the cell lysate but not in the supernatant. Confocal microscopy showed that HEK293 cells expressing hAMH-151S and hAMH-506Q had higher cellular AMH protein levels with endoplasmic reticulum (ER) retention compared to cells expressing wt-hAMH. Using two AMH ELISA kits, hAMH-151S was detected in the cell lysate, while only very low levels were detected in the supernatant. Both hAMH-362S and hAMH-519V were detectable using the automated AMH ELISA but showed severely reduced immunoactivity in the manual ELISA. Surprisingly, hAMH-506Q was undetectable in both the cell lysate and supernatant using either ELISA. However, in PCOS cases, heterozygous carriers of the P151S and H506Q variants still had detectable AMH in both assays. Thus, P151S and H506Q disrupt normal processing and secretion of AMH, causing ER retention. Additionally, AMH variants can impair the AMH immunoactivity. An AMH variant may be considered when serum AMH levels are relatively low in PCOS cases.

Evidence for gonadotrophin secretory and steroidogenic abnormalities in brothers of women with polycystic ovary syndrome.

STUDY QUESTION: Are there abnormalities in gonadotrophin secretion, adrenal steroidogenesis and/or testicular steroidogenesis in brothers of women with polycystic ovary syndrome (PCOS)? SUMMARY ANSWER: Brothers of women with PCOS have increased gonadotrophin responses to gonadotrophin releasing hormone (GnRH) agonist stimulation and alterations in adrenal and gonadal steroidogenesis. WHAT IS KNOWN ALREADY: PCOS is a complex genetic disease. Male as well as female first-degree relatives have reproductive features of the syndrome. We previously reported that brothers of affected women have elevated circulating dehydroepiandrosterone sulfate levels. STUDY DESIGN, SIZE, DURATION: This was a case-control study performed in 29 non-Hispanic white brothers of 22 women with PCOS and 18 control men. PARTICIPANTS/MATERIALS, SETTING, METHODS: PCOS brothers and control men were of comparable age, weight and ethnicity. Adrenocorticotrophic hormone (ACTH) and GnRH agonist stimulation tests were performed. Gonadotrophin responses to GnRH agonist as well as changes in precursor-product steroid pairs (delta, Δ) across steroidogenic pathways in response to ACTH and GnRH agonist were examined. MAIN RESULTS AND THE ROLE OF CHANCE: Basal total (T) levels did not differ, but dehydroepiandrosterone (DHEA) levels (0.13 ± 0.08 brothers versus 0.22 ± 0.09 controls, nmol/l, P = 0.03) were lower in brothers compared with control men. ACTH-stimulated Δ17-hydroxypregnenolone (17Preg)/Δ17-hydroxyprogesterone (17Prog) (7.8 ± 24.2 brothers versus 18.9 ± 21.3 controls, P = 0.04) and ΔDHEA/Δandrostenedione (AD) (0.10 ± 0.05 brothers versus 0.14 ± 0.08 controls, P = 0.04) were lower in brothers than in the controls. GnRH agonist-stimulated Δ17Prog/ΔAD (0.28 ± 8.47 brothers versus 4.79 ± 10.28 controls, P = 0.003) was decreased and luteinizing hormone (38.6 ± 20.6 brothers versus 26.0 ± 9.8 controls, IU/l, P = 0.02), follicle-stimulating hormone (10.2 ± 7.5 brothers versus 4.8 ± 4.1 controls, IU/l P = 0.002), AD (1.7 ± 1.4 brothers versus 0.9 ± 1.5 controls, nmol/l, P = 0.02) and ΔAD/ΔT (0.16 ± 0.14 brothers versus 0.08 ± 0.12 controls, P = 0.005) responses were increased in brothers compared with controls. LIMITATIONS, REASONS FOR CAUTION: The modest sample size may have limited our ability to observe other possible differences in steroidogenesis between PCOS brothers and control men. WIDER IMPLICATIONS OF THE FINDINGS: Decreased ACTH-stimulated Δ17Preg/Δ17Prog and ΔDHEA/ΔAD responses suggested increased adrenal 3ß-hydroxysteroid dehydrogenase activity in the brothers. Decreased Δ17Prog/ΔAD and increased ΔAD/ΔT responses to GnRH agonist stimulation suggested increased gonadal 17,20-lyase and decreased gonadal 17ß-hydroxysteroid dehydrogenase activity in the brothers. Increased LH and FSH responses to GnRH agonist stimulation suggested neuroendocrine alterations in the regulation of gonadotrophin secretion similar to those in their proband sisters. These changes in PCOS brothers may reflect the impact of PCOS susceptibility genes and/or programming effects of the intrauterine environment. STUDY FUNDING/COMPETING INTERESTS: This research was supported by P50 HD044405 (A.D.), K12 HD055884 (L.C.T.), U54 HD034449 (A.D., R.S.L.) from the National Institute of Child Health and Development. Some hormone assays were performed at the University of Virginia Center for Research in Reproduction Ligand Assay and Analysis Core that is supported by U54 HD28934 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Partial support for some of the clinical studies was provided by UL1 RR025741 and UL1 TR000150 (Northwestern University Clinical and Translational Sciences Institute) from the National Center for Research Resources, National Institutes of Health, which is now the National Center for Advancing Translational Sciences. The authors have no conflict of interest to declare.

Insulin resistance and the polycystic ovary syndrome: mechanism and implications for pathogenesis.

It is now clear that PCOS is often associated with profound insulin resistance as well as with defects in insulin secretion. These abnormalities, together with obesity, explain the substantially increased prevalence of glucose intolerance in PCOS. Moreover, since PCOS is an extremely common disorder, PCOS-related insulin resistance is an important cause of NIDDM in women (Table 3). The insulin resistance in at least 50% of PCOS women appears to be related to excessive serine phosphorylation of the insulin receptor. A factor extrinsic to the insulin receptor, presumably a serine/threonine kinase, causes this abnormality and is an example of an important new mechanism for human insulin resistance related to factors controlling insulin receptor signaling. Serine phosphorylation appears to modulate the activity of the key regulatory enzyme of androgen biosynthesis, P450c17. It is thus possible that a single defect produces both the insulin resistance and the hyperandrogenism in some PCOS women (Fig. 19). Recent studies strongly suggest that insulin is acting through its own receptor (rather than the IGF-I receptor) in PCOS to augment not only ovarian and adrenal steroidogenesis but also pituitary LH release. Indeed, the defect in insulin action appears to be selective, affecting glucose metabolism but not cell growth. Since PCOS usually has a menarchal age of onset, this makes it a particularly appropriate disorder in which to examine the ontogeny of defects in carbohydrate metabolism and for ascertaining large three-generation kindreds for positional cloning studies to identify NIDDM genes. Although the presence of lipid abnormalities, dysfibrinolysis, and insulin resistance would be predicted to place PCOS women at high risk for cardiovascular disease, appropriate prospective studies are necessary to directly assess this.

Insulin administration alters gonadal steroid metabolism independent of changes in gonadotropin secretion in insulin-resistant women with the polycystic ovary syndrome.

We have investigated the hypothesis that hyperinsulinemia may cause the polycystic ovary syndrome (PCO) by directly stimulating gonadal steroidogenesis and/or gonadotropin secretion. 10 insulin-resistant women with PCO and 5 age- and weight-matched ovulatory normal women had pulsatile gonadotropin release, gonadotrope sensitivity to gonadotropin-releasing hormone, and sex hormone levels studied on two consecutive study days, basally and during the infusion of insulin (mean +/- SEM steady state insulin levels, 1,254 +/- 63 microU/ml PCO vs. 907 +/- 92 microU/ml normal, P less than or equal to 0.01). Insulin acutely increased mean delta (6 h minus prestudy) levels of androstenedione (A) (P less than or equal to 0.001) and estradiol (E2) (P less than or equal to 0.05) and decreased mean plasma pool (0-6 h) levels of testosterone (T) (P less than 0.05), nonsex hormone binding globulin-bound T (P less than 0.05), and dihydrotestosterone (P less than or equal to 0.01) in the PCO women. Insulin also decreased mean plasma 6 h A to estrone (E1) ratios and increased 6 h E1 levels (both P less than or equal to 0.05) in the PCO women. There were significant sequence effects (insulin + day) in the PCO women on T/E2 ratios, indicating a carryover action of insulin. Insulin had no effects on gonadotropin release in the PCO women. In the normal women, the only significant change was an insulin or study day effect that increased mean 6 h E2 levels (P less than or equal to 0.01). There were significant spontaneous decreases in mean luteinizing hormone (p less than 0.05) and follicle-stimulating hormone levels (p less than or equal to 0.01) in the PCO but not the normal women on the second day of study. This study indicates that insulin can directly alter peripheral sex hormone levels independent of changes in gonadotropin release in insulin-resistent PCO women. Insulin decreased the levels of potent androgens in PCO women and did not increase androgen levels in normal women, arguing against a simple, direct causal relationship between hyperinsulinemia and hyperandrogenism in PCO.

Excessive insulin receptor serine phosphorylation in cultured fibroblasts and in skeletal muscle. A potential mechanism for insulin resistance in the polycystic ovary syndrome.

We investigated the cellular mechanisms of the unique disorder of insulin action found in the polycystic ovary syndrome (PCOS). Approximately 50% of PCOS women (PCOS-Ser) had a significant increase in insulin-independent beta-subunit [32P]phosphate incorporation (3.7-fold, P < 0.05 vs other groups) in skin fibroblast insulin receptors that was present in serine residues while insulin-induced tyrosine phosphorylation was decreased (both P < 0.05 vs other groups). PCOS skeletal muscle insulin receptors had the same abnormal phosphorylation pattern. The remaining PCOS women (PCOS-n1) had basal and insulin-stimulated receptor autophosphorylation similar to control. Phosphorylation of the artificial substrate poly GLU4:TYR1 by the PCOS-Ser insulin receptors was significantly decreased (P < 0.05) compared to control and PCOS-n1 receptors. The factor responsible for excessive serine phosphorylation appeared to be extrinsic to the receptor since no insulin receptor gene mutations were identified, immunoprecipitation before autophosphorylation corrected the phosphorylation defect and control insulin receptors mixed with lectin eluates from affected PCOS fibroblasts displayed increased serine phosphorylation. Our findings suggest that increased insulin receptor serine phosphorylation decreases its protein tyrosine kinase activity and is one mechanism for the post-binding defect in insulin action characteristic of PCOS.

Body composition, not body weight, is related to cardiovascular disease risk factors and sex hormone levels in men.

To clarify the independent relationships of obesity and overweight to cardiovascular disease risk factors and sex steroid levels, three age-matched groups of men were studied: (i) 8 normal weight men, less than 15% body fat, by hydrostatic weighing; (ii) 16 overweight, obese men, greater than 25% body fat and 135-160% of ideal body weight (IBW); and (iii) 8 overweight, lean men, 135-160% IBW, but less than 15% fat. Diastolic blood pressure was significantly greater for the obese (mean +/- SEM, 82 +/- 2 mmHg) than the normal (71 +/- 2) and overweight lean (72 +/- 2) groups, as were low density lipoprotein levels (131 +/- 9 vs. 98 + 11 and 98 + 14 mg/dl), the ratio of high density lipoprotein to total cholesterol (0.207 +/- 0.01 vs. 0.308 +/- 0.03 and 0.302 +/- 0.03), fasting plasma insulin (22 +/- 3 vs. 12 +/- 1 and 13 +/- 2 microU/ml), and the estradiol/testosterone ratio (0.076 +/- 0.01 vs. 0.042 +/- 0.02 and 0.052 +/- 0.02); P less than 0.05. Estradiol was 25% greater for the overweight lean group (40 +/- 5 pg/ml) than the obese (30 +/- 3 pg/ml) and normal groups (29 +/- 2 pg/ml), P = 0.08, whereas total testosterone was significantly lower in the obese (499 +/- 33 ng/dl) compared with the normal and overweight, lean groups (759 +/- 98 and 797 +/- 82 ng/dl). Estradiol was uncorrelated with risk factors and the estradiol/testosterone ratio appeared to be a function of the reduced testosterone levels in obesity, not independently correlated with lipid levels after adjustment for body fat content. Furthermore, no risk factors were significantly different between the normal and overweight lean groups. We conclude that (a) body composition, rather than body weight per se, is associated with increased cardiovascular disease risk factors; and (b) sex steroid alterations are related to body composition and are not an independent cardiovascular disease risk factor.

Insulin/IGF-1 and TNF-alpha 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.

Fine mapping of genetic susceptibility to polycystic ovary syndrome on chromosome 19p13.2 and tests for regulatory activity.

CONTEXT: Little is known about genes that contribute to polycystic ovary syndrome (PCOS). We previously found linkage and association of PCOS with the dinucleotide marker D19S884 in two independent sets of families; allele 8 of D19S884 confers increased risk. OBJECTIVE/DESIGN: The objectives of the study were: 1) use the transmission/disequilibrium test (TDT) to assess linkage and association between PCOS and D19S884 (and nearby markers) in a third set of families; and 2) test D19S884 and surrounding DNA sequence for in vitro regulatory activity in lymphoblastoid cell lines (LCLs) and granulosa cells. SETTING/SUBJECTS: We studied 98 new families with a PCOS proband, father, mother, and other available offspring. We analyzed data from these families separately and in combination with data obtained previously. INTERVENTIONS: Interventions were venipuncture. MAIN OUTCOME MEASURES: Measures were transmission frequencies and in vitro functional studies. RESULTS: The first result we found was that in the 98 new families, the TDT was significant for allele 8 of D19S884 (P = 0.043). In the total collection of 465 families, the TDT evidence is very strong (nominal P < 7 x 10(-5)). Results for all other genetic markers near D19S884 were nonsignificant after correction for multiple testing. The second result was that an approximately 800-bp fragment containing various alleles of D19S884 showed modest but reproducible promoter activity in LCLs. However, no allelic differences were detected. No activity of this fragment was detected in granulosa cells. CONCLUSIONS: This is the second independent confirmation of linkage and association of D19S884 with PCOS. We found in addition that some sequence in the region of D19S884 confers in vitro promoter activity in LCLs.

Candidate gene region for polycystic ovary syndrome on chromosome 19p13.2.

CONTEXT: Polycystic ovary syndrome (PCOS) is a common endocrine disorder that is believed to have a genetic basis. However, no specific susceptibility gene or region has been conclusively identified. OBJECTIVE: The objective of this study was to duplicate a previous study that localized a PCOS susceptibility region to chromosome 19p13.2 and to narrow the susceptibility region. DESIGN: This study was designed to test for genetic linkage and association between PCOS and short tandem repeat polymorphisms in 367 families, by analysis of linkage and family-based association. SETTING: The study was conducted at academic medical centers. PATIENTS OR OTHER PARTICIPANTS: We studied 367 families of predominantly European origin with at least one PCOS patient. Families included 107 affected sibling (sister) pairs (ASPs) in 83 families, and 390 trios with both parents and an affected daughter. The data set comprises two independent groups. Set 1 consists of 44 ASPs and 163 trios. Set 2 consists of 63 ASPs and 227 trios. INTERVENTION(S): The intervention was the drawing of blood for DNA extraction. MAIN OUTCOME MEASURE: We employed measures of evidence for linkage and association between PCOS and 19 STRs. RESULTS: Linkage with PCOS was observed over a broad region of chromosome 19p13.2. The strongest evidence for association was observed with D19S884 (chi2 = 11.85; nominal P < 0.0006; permutation P = 0.034) and duplicated our earlier findings. CONCLUSIONS: The present analysis suggests that a PCOS susceptibility locus maps very close to D19S884. Additional studies that systematically characterize DNA sequence variation in the immediate area of D19S884 are required to identify the PCOS susceptibility variant.

Ethnicity and polycystic ovary syndrome are associated with independent and additive decreases in insulin action in Caribbean-Hispanic women.

This study was conducted to determine the impact of polycystic ovary syndrome and ethnicity on insulin action. Thirteen Caribbean-Hispanic and 10 non-Hispanic white polycystic ovary syndrome women were compared with 5 Caribbean-Hispanic and 8 non-Hispanic white normal women matched for age, weight, and body composition. All subjects underwent a 2-h 75 g oral glucose tolerance test and euglycemic glucose clamp study with a 40 mU.m-2 x min-1 insulin dose. Hepatic glucose production was determined basally and throughout the euglycemic clamp study. Polycystic ovary syndrome was associated with significant increases in fasting insulin levels (P < 0.05) and in 2-h postglucose-load glucose and insulin levels (P < 0.001). Ethnicity was not associated with any changes in these parameters. Polycystic ovary syndrome but not ethnicity was also associated with hepatic insulin resistance, because significant (P < 0.05) residual hepatic glucose production occurred during the euglycemic clamp in the polycystic ovary syndrome women. However, significant independent effects existed for both polycystic ovary syndrome (P < 0.01) and ethnicity (P < 0.05) that resulted in decreased insulin-mediated glucose disposal. Similarly, significant independent effects of polycystic ovary syndrome (P < 0.005) and ethnicity (P < 0.05) occurred, resulting in increased steady-state insulin levels during the euglycemic clamp. This appeared to be, in part, secondary to a decrease in the metabolic clearance rate of insulin associated with ethnicity (P < 0.05). We conclude that polycystic ovary syndrome and ethnicity result in independent and additive decreases in insulin sensitivity in Caribbean-Hispanic women.(ABSTRACT TRUNCATED AT 250 WORDS)

Profound peripheral insulin resistance, independent of obesity, in polycystic ovary syndrome.

Hyperinsulinemia secondary to a poorly characterized disorder of insulin action is a feature of the polycystic ovary syndrome (PCO). However, controversy exists as to whether insulin resistance results from PCO or the obesity that is frequently associated with it. Thus, we determined in vivo insulin action on peripheral glucose utilization (M) and hepatic glucose production (HGP) with the euglycemic glucose-clamp technique in obese (n = 19) and nonobese (n = 10) PCO women and age- and body-composition-matched normal ovulatory women (n = 11 obese and n = 8 nonobese women). None had fasting hyperglycemia. Two obese PCO women had diabetes mellitus, established with an oral glucose tolerance test; no other women had impairment of glucose tolerance. However, the obese PCO women had significantly increased fasting and 2-h glucose levels after an oral glucose load and increased basal HGP compared with their body-composition-matched control group. There were statistically significant interactions between obesity and PCO in fasting glucose levels and basal HGP (P less than .05). Steady-state insulin levels of approximately 100 microU/ml were achieved during the clamp. Insulin-stimulated glucose utilization was significantly decreased in both PCO groups whether expressed per kilogram total weight (P less than .001) or per kilogram fat free mass (P less than .001) or when divided by the steady-state plasma insulin (l) level (M/l, P less than .001). There was residual HGP in 4 of 15 obese PCO, 0 of 11 obese normal, 2 of 10 nonobese PCO, and 0 of 8 nonobese normal women. The metabolic clearance rate of insulin did not differ in the four groups. We conclude that 1) PCO women have significant insulin resistance that is independent of obesity, changes in body composition, and impairment of glucose tolerance, 2) PCO and obesity have a synergistic deleterious effect on glucose tolerance, 3) hyperinsulinemia in PCO is not the result of decreased insulin clearance, and 4) PCO is associated with a unique disorder of insulin action.

Evidence for distinctive and intrinsic defects in insulin action in polycystic ovary syndrome.

Women with PCO have a unique but poorly characterized disorder of insulin action. Obese (n = 16) and nonobese (n = 14) PCO women and age- and weight-matched normal, nondiabetic ovulatory women (obese, n = 15; nonobese, n = 17) had insulin action determined in vivo with sequential multiple insulin dose euglycemic clamps and in isolated abdominal adipocytes to clarify the mechanisms of insulin resistance. PCO resulted in significant increases in the ED50 insulin for glucose utilization in vivo (P less than 0.001) and in adipocytes (P less than 0.01), without significant changes in adipocyte insulin-binding sites. PCO also resulted in significant decreases in maximal insulin-stimulated rates of glucose utilization in vivo (P less than 0.01) and in adipocytes (P less than 0.01). Obesity resulted in smaller decreases in insulin sensitivity than PCO (ED50 insulin, P less than 0.001 in vivo and P less than 0.05 in adipocytes), but greater decreases in insulin responsiveness (Vmax, P less than 0.001 in vivo and in adipocytes). The ED50 insulin for suppression of HGP was increased only in obese PCO women (P less than 0.001), and the interactions between PCO and obesity on this parameter were statistically significant. No significant correlations between androgen or estrogen levels and adipocyte insulin binding or action were found. Because insulin binding was not changed, we conclude that the major lesion causing insulin resistance in PCO is a striking decrease in insulin sensitivity secondary to a defect in the insulin receptor and/or postreceptor signal transduction. PCO also is associated with modest but significant decreases in glucose transport. These defects in insulin action appear to represent intrinsic abnormalities that are independent of obesity, metabolic derangements, body fat topography, and sex hormone levels. Conversely, changes in hepatic insulin sensitivity appear to be acquired with obesity.

New perspectives in polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is, perhaps, the most common endocrinopathy affecting premenopausal women. Of such women, 5%-10% have the classic endocrine syndrome of hyperandrogenism and chronic anovulation. The syndrome not only has these long-appreciated reproductive morbidities, but it also has more recently recognized important metabolic consequences related to insulin resistance. This article reviews the current state of the field with respect to the pathogenesis of PCOS and the insulin resistance associated with it.

Hirsutism.

The clinical presentation and management of the hirsute woman is illustrated in cases of idiopathic hirsutism, polycystic ovarian disease, and nonclassical congenital adrenal hyperplasia. Therapeutic regimens manage hyperandrogenic signs, induce ovulation, and protect the endometrium.

The effects of experimental hyperinsulinemia on steroid secretion, ovarian [125I]insulin binding, and ovarian [125I]insulin-like growth-factor I binding in the rat.

We randomized 32 cycling female Sprague-Dawley rats (82 days old) into experimental and control groups (16 animals/group). Hyperinsulinemia was induced and maintained for 22 days in the experimental group with NPH human insulin (Novolin, Squibb-Novo, Princeton, NJ) as previously described. Controls received an identical volume of vehicle. Fifteen minutes before death, each rat received a sc injection of 100 ng synthetic GnRH (Factrel, Ayerst Laboratories, New York, NY). The mean serum insulin level was significantly higher in the insulin-treated group than in the control group (165 +/- 57 vs. 49 +/- 9 microU/ml; P less than 0.05). The mean final weight also was significantly higher in the insulin-treated group (283 +/- 4 vs. 242 +/- 7 g; P less than 0.001). There were no significant differences in mean final serum levels of testosterone, estradiol, estrone, or androstenedione or in GnRH-stimulated serum levels of LH or FSH. The androstenedione to estrone ratio, however, was significantly lower in the insulin-treated group (2.5 +/- 0.3 vs. 3.4 +/- 0.2; P less than 0.01), suggesting that aromatase activity increased with hyperinsulinemia. Specific [125I]insulin binding to ovarian tissue homogenates was lower in the insulin-treated group (1.7 +/- 0.1% vs. 2.6 +/- 0.6%/0.2 mg protein; P greater than 0.05), suggesting that ovarian insulin receptors tended to down-regulate with hyperinsulinemia. Specific [125I]insulin-like growth factor I [( 125I]IGF-I) binding to ovarian tissue homogenates, in contrast, was significantly higher in the insulin-treated group (13.3 +/- 1.4% vs. 7.2 +/- 0.6%/0.2 mg protein; P less than 0.05), suggesting that ovarian IGF receptors up-regulated with hyperinsulinemia. The affinity of neither [125I]insulin binding nor that of [125I]IGF-I binding changed significantly, with the 50% inhibition point remaining between 2.0 and 5.0 ng/ml for each peptide in both groups. We conclude that hyperinsulinemia increases ovarian [125I]IGF-I binding and stimulates aromatase activity in the rat. These phenomena, if also true in women, could be important factors contributing to the ovarian hyperstimulation observed in various hyperinsulinemic states.

Intracellular localization of prolactin receptor and prolactin in the rat ovary by immunocytochemistry.

The localization of the PRL receptor as well as of PRL has been studied by immunoperoxidase techniques in the ovaries of cycling, pregnant, and lactating rats. Specific antisera to the receptor and to the hormone were used. By light microscopy, immunostaining for the PRL receptor coincided with that for the hormone. Staining was found intracellularly in most components of the ovary, except the theca, and was most striking in the luteal cells. Both PRL and its receptor were concentrated heavily in the ovum. Beginning 24-36 h postpartum, there was a change in the pattern of luteal cell staining, with a shift in the intensity of staining products to the periphery of the luteal cell, giving a ring appearance to these cells. The results suggest roles for PRL in ovarian function involving both maintenance of the corpus luteum and maturation of the ovum. This study also demonstrates the intracellular localization of a polypeptide hormone in association with its specific receptor.

Do androgens directly regulate gonadotropin secretion in the polycystic ovary syndrome?

This study was designed to investigate whether androgens directly, independent of their aromatization to estrogens, disrupt gonadotropin secretion in hyperandrogenic women with the polycystic ovary syndrome (PCO). Pulsatile gonadotropin release and gonadotroph sensitivity to GnRH were determined on consecutive study days basally and during a primed continuous infusion of testosterone (T; n = 4; 100 micrograms/h; twice the mean production rate of T in PCO) or dihydrotestosterone (DHT; n = 5; 50 micrograms/h). To determine if the gonadotropin secretory changes during T infusion were secondary to spontaneous variation, four patients had two consecutive basal studies, and all patients received DHT on the third study day. T infusion that increased mean plasma T levels from 76 +/- 12 (+/- SE) to 315 +/- 28 ng/dl produced no significant changes in the amount or pattern of LH release or in LH sensitivity to GnRH. Mean plasma FSH levels decreased slightly but significantly during T infusion (basal, 242 +/- 29 vs. T 226 +/- 30 ng/ml LER-907; P less than 0.05 by two-tailed paired t test), but the pulsatile pattern of FSH release and FSH sensitivity to GnRH did not change. DHT infusion increased plasma DHT levels from 17 +/- 3 to 244 +/- 31 ng/dl, but did not alter the mean levels, pulsatile patterns, or sensitivity to GnRH of LH or FSH. These data suggest that androgens do not directly alter gonadotropin release in PCO. Thus, regulation of the hypothalamic-pituitary axis in women with PCO is different from that in men despite chronic exposure to hyperandrogenemia.

Selective insulin resistance in the polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is characterized by hyperandrogenemia that is amplified by insulin in the presence of resistance to insulin's action to stimulate glucose uptake in muscle and fat. To explore the mechanisms for this paradox, we examined the metabolic and mitogenic actions of insulin and insulin-like growth factor I (IGF-I) in cultured skin fibroblasts from PCOS (n = 16) and control (n = 11) women. There were no significant decreases in the number or affinity of insulin- or IGF-I-binding sites in PCOS compared to control fibroblasts. Basal rates were similar, but there were significant decreases in insulin-stimulated (control, 51.8 +/- 7.0; PCOS, 29.5 +/- 2.9 nmol/10(6) cells x 2 h at 1,000,000 pmol/L; P < 0.005) and IGF-I-stimulated (control, 48.9 +/- 6.7; PCOS, 33.0 +/- 3.2 PCOS nmol/10(6) cells x 2 h at 100,000 pmol/L IGF-I; P < 0.05) glucose incorporation into glycogen in PCOS fibroblasts, a metabolic action of insulin. Stimulation of thymidine incorporation, a mitogenic action of insulin, was similar in PCOS and control fibroblasts in response to both insulin and IGF-I. There were also no significant differences in insulin- or IGF-I-stimulated insulin receptor substrate-1-associated phosphatidylinositol-3-kinase activity in PCOS compared to control fibroblast cells. We conclude that 1) there is a selective defect in insulin action in PCOS fibroblasts that affects metabolic, but not mitogenic, signaling pathways; 2) there is a similar defect in IGF-I action, suggesting that insulin and IGF-I stimulate glycogen synthesis by the same postreceptor pathways; and 3) insulin receptor substrate-1-associated phosphatidylinositol 3-kinase activation by insulin and IGF-I is similar to the control value, suggesting that the metabolic signaling defect is in another pathway or downstream of this signaling step in PCOS fibroblasts.

Beta-cell dysfunction independent of obesity and glucose intolerance in the polycystic ovary syndrome.

Several distinct groups of subjects at high risk to develop noninsulin-dependent diabetes mallitus (NIDDM) have been found to have insulin secretory defects when beta-cell function is assessed in the context of peripheral insulin sensitivity. We investigated this with a modified frequently sampled iv glucose tolerance test to determine acute insulin responses to glucose (AIRg) as well as insulin action by minimal model analysis in 28 women with polycystic ovary syndrome (PCOS; 15 obese and 13 nonobese) and 29 age- and weight-matched normal women (14 obese and 15 nonobese). No subject, PCOS or control, had fasting hyperglycemia, but seven PCOS women (six obese and one nonobese) had impaired glucose tolerance or NIDDM. The PCOS women had significantly decreased insulin sensitivity compared to the normal women (P < or = 0.001), and the obese women were less sensitive than the nonobese women (P < or = 0.001). The empiric measure of insulin release, AIRg, was significantly increased by obesity (P < or = 0.01), but not by PCOS. However, the disposition index (insulin sensitivity x AIRg) was significantly decreased by both PCOS (< or = 0.005) and obesity (< or = 0.005), suggesting that AIRg was inadequate for the degree of insulin resistance. When the PCOS women with impaired glucose tolerance or NIDDM were removed from the analysis, all of the reported PCOS-related changes in insulin action and secretion remained significant. We conclude that both obese and nonobese PCOS women have beta-cell dysfunction as well as insulin resistance. However, this was not associated with glucose intolerance in the majority of PCOS women.

The impact of obesity and chronic hyperinsulinemia on gonadotropin release and gonadal steroid secretion in the polycystic ovary syndrome.

We investigated whether obesity was a marker for a neuroendocrinologically distinct form of the polycystic ovary syndrome (PCO). Further, since women with PCO have significantly higher basal and/or glucose-stimulated plasma insulin levels, we also examined the effects of chronic hyperinsulinemia on gonadotropin and gonadal steroid secretion. Ten obese women (nine with acanthosis nigricans) and five nonobese women (one with acanthosis nigricans) with PCO as well as seven obese and six nonobese women of comparable age and weight in the midfollicular phase of their cycles were studied. Pulsatile gonadotropin release was determined for 6-24 h as well as gonadotroph sensitivity to GnRH (10 micrograms, iv). The obese PCO women had significantly increased basal and glucose-stimulated plasma insulin levels compared to the other groups, the nonobese PCO and the obese normal women had similar insulin levels, and the nonobese normal women had the lowest insulin levels. All four groups had similar plasma estradiol levels. Both the obese and the nonobese PCO women had similar and significantly higher mean plasma LH levels, LH pulse amplitude, and integrated LH responses to GnRH compared to values in both normal groups (P less than 0.01 to P less than 0.001); the obese PCO women did not differ from the nonobese PCO women. The mean LH pulse frequencies per 6 h were similar in the four groups. FSH secretion did not differ significantly in the four groups. The levels of the putative gonadal feedback steroids, plasma total and non-sex hormone-binding globulin-bound testosterone, non-sex hormone-binding globulin-bound estradiol, and estrone, were similar in both PCO groups and were significantly higher than those in both normal groups (all P less than 0.001). The only independent effect of obesity was on plasma androstenedione levels and the androstenedione to estrone ratio, both of which were significantly higher in PCO women than normal women (P less than 0.01 to P less than 0.001), but significantly lower in the obese (PCO and normal) women than in nonobese (PCO and normal) women (P less than 0.05). These findings suggest that 1) the impact, if any, of obesity in PCO is not reflected in discernible changes in gonadotropin release or in the gonadal steroid feedback environment; and 2) insulin does not have a major role in the perpetuation of PCO, since obese and nonobese PCO women had similar reproductive hormone levels despite significantly different degrees of hyperinsulinemia.