Serum and follicular resistin levels in women with polycystic ovarian syndrome during IVF-stimulated cycles

BACKGROUND: Resistin is a hormone linking obesity and insulin resistance. The aim of this study was to compare resistin levels in serum or follicular fluid from women with polycystic ovarian syndrome (PCOS) and controls, both of whom were undergoing IVF. METHODS: We compared serum and follicular resistin levels in 21 PCOS women and in 18 healthy, normal ovulation, age- and body mass index (BMI)-matched non-PCOS women undergoing IVF. Correlations between serum or follicular fluid resistin levels and reproductive outcome were evaluated. RESULTS: There was no significant difference in either serum or follicular resistin levels between the control group and the PCOS group as a whole or those with insulin resistance [homeostasis model assessment of insulin resistance index applied to oral glucose tolerance test (HOMA(OGTT)) <4.7]. However, resistin levels in follicular fluid were unexpectedly significantly lower than serum levels (P<0.0001) in both the PCOS and control groups. No significant correlation was found between resistin levels and BMI, estradiol, LH, or fasting or 2 h glucose or insulin levels or between follicular resistin levels and fertilization rate, implantation rate, clinical pregnancy rate, or early miscarriage rate in PCOS. CONCLUSION: Resistin is unlikely to be a major determining factor in the growth and maturation of oocytes during IVF-stimulated cycles in PCOS.     

Adipocyte resistin mRNA levels are down-regulated by laparoscopic ovarian electrocautery in both obese and lean women with polycystic ovary syndrome

BACKGROUND: The aim of this study was to investigate serum and adipocyte mRNA expression of resistin in lean and obese women with polycystic ovary syndrome (PCOS) before and 3 months after laparoscopic ovarian electrocauterization (LOE). METHODS: Adipose tissue obtained from 12 women with PCOS (six obese and six lean, body mass index > 27 kg m(-1) as threshold point) before and after LOE was analysed. Gene expression of resistin was measured by semi-quantitative RT-PCR. Ten lean, age-matched healthy women served as controls. RESULTS: Both lean and obese women with PCOS had significantly higher fasting and 2 h insulin and homeostasis model insulin resistance index (HOMA(IR)) values and lower fasting glucose-to-insulin ratios (G(0)/I(0)) than did the controls. The serum levels of glucose and insulin and HOMA(IR) were significantly decreased, and the G(0)/I(0) ratio was significantly increased 3 months after LOE. No difference was found in serum resistin levels between controls and either obese or lean women with PCOS before LOE, nor between PCOS patients before and after LOE. However, resistin mRNA expression levels in both lean and obese women with PCOS before LOE were significantly higher than that in controls and were decreased significantly after LOE back to control levels. CONCLUSION: Local resistin activity may be actively involved in the pathogenesis of PCOS. LOE reduces insulin resistance and down-regulates resistin mRNA expression in lean and obese women with PCOS.     

Adiponectin and resistin in PCOS: a clinical, biochemical and molecular genetic study

BACKGROUND: We conducted a cross-sectional case-control study to evaluate the possible involvement of adiponectin and resistin in the pathogenesis of polycystic ovary syndrome (PCOS). METHODS: Seventy-six PCOS patients and 40 non-hyperandrogenic women matched for BMI and degree of obesity were included. Serum adiponectin and resistin levels, anthropometrical and hormonal variables, the 45 T-->G and 276 G-->T polymorphisms in the adiponectin gene, and the -420 C-->G variant in the resistin gene, were analysed. RESULTS: Serum adiponectin concentrations were reduced in PCOS patients compared with controls (P = 0.038) irrespective of the degree of obesity, whereas serum resistin levels were increased in overweight and obese women compared with lean subjects (P = 0.016), irrespective of their PCOS or controls status. The adiponectin and resistin polymorphisms were not associated with PCOS and did not influence serum levels of adiponectin, resistin and other clinical and hormonal variables. In a multiple regression model, the waist-to-hip ratio, free testosterone levels and age, but not insulin resistance, were the major determinants of hypoadiponectinaemia. CONCLUSIONS: PCOS patients present with hypoadiponectinaemia, in relation with abdominal adiposity and hyperandrogenism. Our present results suggest that hyperandrogenism and abdominal obesity, by reducing the serum levels of the insulin sensitizer adipokine adiponectin, might contribute to the insulin resistance of PCOS.     

Amelioration of insulin resistance in women with PCOS via reduced insulin receptor substrate-1 Ser312 phosphorylation following laparoscopic ovarian electrocautery

BACKGROUND: Increased Ser(312) phosphorylation of insulin receptor substrate (IRS)-1 is one possible molecular mechanism of insulin resistance in polycystic ovary syndrome (PCOS). We investigated whether laparoscopic ovarian electrocautery (LOE) improved insulin sensitivity in women with PCOS and examined the underlying molecular mechanism of LOE. METHODS: Adipose tissue and blood samples from 12 women with PCOS before, and 3 months after, LOE were analysed. RESULTS: Before LOE, women with PCOS were found to have significantly higher 2 h glucose, fasting and 2 h insulin levels, homeostasis model insulin resistance index and lower fasting glucose-to-insulin ratio (G(0)/I(0)) than healthy, lean, age-matched controls. Serum levels of glucose and insulin were significantly decreased, and G(0)/I(0) ratio was significantly increased 3 months after LOE. Levels of activated extracellular signal-regulated kinase 1/2 in PCOS women were higher than in controls, but were significantly decreased after LOE. Levels of insulin receptor, glucose transporter-4 and phosphatidylinositol 3-kinase were lower in PCOS patients before LOE than in controls and increased after LOE. Levels of Ser(312)-phosphorylated IRS-1 in PCOS women before LOE were higher than in controls and decreased significantly after LOE, whereas IRS-1 tyrosine phosphorylation in PCOS women before LOE was lower than in controls and increased significantly after LOE. CONCLUSION: Over the short observation period of this study, our results demonstrated that LOE effectively ameliorated insulin resistance in women with PCOS via decreased IRS-1 Ser(312) phosphorylation.     

resistin基因过表达影响3T3-L1脂肪细胞的脂质代谢

目的观察resistin基因过表达对3T3-L1脂肪细胞的脂质代谢、糖代谢的影响。方法构建大鼠resistin真核表达载体并转染3T3-L1前体脂肪细胞,获得稳定表达resistin基因的细胞株;采用油红O染色,观察脂肪细胞分化及脂质积聚情况;采用逆转录PCR技术,检测脂肪细胞分化标志基因及葡萄糖转运体4（glucose transporter4,GLUT4）基因表达变化;采用全自动生化仪比色法,检测脂肪细胞内甘油三酯（triglyceride,TG）、游离脂肪酸（free fatty acids,FFAs）的含量变化。结果（1）resistin基因过表达脂肪细胞中,脂滴出现时间提前,且细胞内布满了小而多的圆形脂滴;（2）resistin基因过表达脂肪细胞中,分化中、晚期标志基因C/EBPα、FAS的mRNA表达水平明显上调,分化早期标志基因Pref-1的表达则明显下调;（3）re-sistin基因过表达脂肪细胞中,胞质内TG、FFAs含量均显著增加;（4）resistin基因过表达脂肪细胞中,分化第2、4、8d的GLUT4基因mRNA表达水平间无显著变化,与正常脂肪细胞中的表达水平差异也无统计学意义。结论resistin基因过表达能够显著干扰3T3-L1脂肪细胞的脂质代谢,有助于肥胖和胰岛素抵抗的发生,而并不影响GLUT4基因的表达。     

Polymorphisms in the insulin receptor substrate-1 (IRS-1) gene and the insulin receptor substrate-2 (IRS-2) gene influence glucose homeostasis and body mass index in women with polycystic ovary syndrome and non-hyperandrogenic controls

BACKGROUND: We aimed to evaluate the influence of the Gly972Arg variant of the insulin receptor substrate-1 gene (IRS-1) and the Gly1057Asp variant in IRS-2 on insulin resistance and glucose tolerance in women with polycystic ovary syndrome (PCOS) and healthy controls. METHODS: Genotypes, allelic frequencies, indexes of insulin resistance, glucose tolerance and hormone profiles were studied in a large sample of Spanish PCOS (n = 103) women compared with a control group (n = 48) of healthy women matched for body mass index. RESULTS: No differences in genotype or allelic frequencies were found between PCOS patients and healthy controls. When considering control subjects and PCOS patients as a whole, IRS-1 Arg972 carriers also presented with increased fasting insulin (133 +/- 60 versus 95 +/- 67 pmol/l, P = 0.008) and insulin resistance measured by homeostasis model assessment (4.3 +/- 2.1 versus 3.1 +/- 2.4, P = 0.009) compared with subjects homozygous for Gly972 alleles. These differences were even higher when restricting the analysis to PCOS patients. Subjects homozygous for the Gly1057 allele of IRS-2 presented with increased 60 and 90 min oral glucose tolerance test (OGTT) glucose levels compared with carriers of one or two Asp1057 alleles (7.9 +/- 2.1 versus 7.1 +/- 2.1 mmol/l, P = 0.042 and 7.0 +/- 2.1 versus 6.0 +/- 1.8 mmol/l, P = 0.014), and a similar tendency was observed for 120 min OGTT glucose levels. CONCLUSIONS: The Gly972Arg in IRS-1 and Gly1057Asp in IRS-2 polymorphisms influence glucose homeostasis in premenopausal women, but are not associated with PCOS.     

The role of insulin-like growth factor-1 (IGF-1) and IGF binding protein-1 (IGFBP-1) in the pathogenesis of polycystic ovary syndrome.

The objective of this study was to elucidate the relationship and role of insulin-like growth factor-1 (IGF-1), IGF binding protein-1 (IGFBP-1), insulin and luteinizing hormone (LH) in the pathogenesis of polycystic ovary syndrome (PCOS). In a pilot study, serum concentrations of IGF-1 were determined in women with PCOS (n = 10), hypopituitarism (n = 12) and normal controls (n = 10). In the main study, serum concentrations of IGF-1, IGFBP-1, insulin and LH in women with anovulation associated (n = 23) and not associated (n = 47) with PCOS were determined. Serum concentrations of IGF-1 were not different in women with PCOS, anovulatory non-PCOS and healthy women but were low in those with hypopituitarism. Mean serum IGFBP-1 in PCOS (33.8 +/- 21.2 micrograms/l) was decreased compared with anovulatory non-PCOS (60.0 +/- 22 micrograms/l) (P = 0.0001), and correlated negatively with insulin concentrations (r = -0.67, P = 0.0006). Patients with PCOS could be separated into those with high LH and those with high insulin levels. It was concluded that women with PCOS have normal serum IGF-1 concentrations but IGFBP-1 levels, regulated by insulin, are low. Hyperinsulinaemia and raised LH are independently capable of stimulating ovarian androgen production. Growth factors may have an important role in the pathogenesis of PCOS.     

Glucose intolerance, insulin resistance and cardiovascular risk factors in first degree relatives of women with polycystic ovary syndrome

BACKGROUND: The aim of the present study was to evaluate insulin resistance (IR), glucose tolerance status and cardiovascular risk factors in first degree relatives of patients with polycystic ovary syndrome (PCOS). METHODS: A total of 120 family members [Mothers(PCOS) (n = 40), Fathers(PCOS) (n = 38), Sisters(PCOS) (n = 25) and Brothers(PCOS) (n = 17)] of 55 patients with PCOS and 75 unrelated healthy control subjects without a family history of diabetes or PCOS (four age- and weight-matched subgroups, i.e. Control(Mothers), Control(Fathers), Control(Sisters) and Control(Brothers)) were studied. IR was assessed by homeostatic model assessment (HOMA IR), log HOMA, insulin sensivity index (ISI), the quantitative insulin sensitivity check index (QUICKI) and area under the curve for insulin during the oral glucose tolerance test (AUCI, AUCG) in with normal glucose tolerance (NGT) subjects and controls. Serum adiponectin, resistin, homocysteine and lipid levels were measured. RESULTS: The prevalence of any degree of glucose intolerance was 40% in Mothers(PCOS) and 52% in Fathers(PCOS). In total, six (15%) glucose tolerance disorders were identified in the Control(Mothers) and Control(Fathers) in first degree relatives of control subjects. The first degree relatives of PCOS patients had significantly higher serum fasting insulin, HOMA-IR, Log HOMA and AUCI levels in all subgroups than the control subjects. The control subjects had significantly elevated QUCKI, ISI levels and serum adiponectin levels compared to the first degree relatives of PCOS subjects in all subgroups. The serum Hcy and resistin levels increased significantly in both Fathers(PCOS) and Mothers(PCOS) groups but not Brothers(PCOS) and Sister(PCOS). CONCLUSION: The results of the present study support the finding that the first degree relatives of PCOS patients carry an increased risk of cardiovascular disease, as do PCOS patients.     

The brown adipose cell: a model for understanding the molecular mechanisms of insulin resistance

Type 2 diabetes mellitus is a complex metabolic disease that occurs when insulin secretion can no longer compensate insulin resistance in peripheral tissues. At the molecular level, insulin resistance correlates with impaired insulin signalling. This review provides new insights into the molecular mechanisms of insulin action and resistance in brown adipose tissue and pinpoints the role of this tissue in the control of glucose homeostasis. Brown adipocytes are target cells for insulin and IGF-I action, especially during late foetal development when insulin supports survival and promotes both adipogenic and thermogenic differentiation. The main pathway involved in insulin induction of adipogenic differentiation, monitored by fatty acid synthase expression, is the cascade insulin receptor substrate (IRS)-1/phosphatidylinositol 3-kinase (PI3K)/Akt. Glucose transport in these cells is maintained mainly by the activity of GLUT4. Acute insulin treatment stimulates glucose transport largely by mediating translocation of GLUT4 to the plasma membrane, involving the activation of IRS-2/PI3K, and the downstream targets Akt and protein kinase C zeta. Tumour necrosis factor (TNF-alpha) caused insulin resistance on glucose uptake by impairing insulin signalling at the level of IRS-2. Activation of stress kinases and phosphatases by this cytokine contribute to insulin resistance. Furthermore, brown adipocytes are also target cells for rosiglitazone action since they show a high expression of peroxisome proliferator activated receptor gamma, and rosiglitazone increased the expression of the thermogenic uncoupling protein 1. Rosiglitazone ameliorates insulin resistance provoked by TNF-alpha, completely restoring insulin-stimulated glucose uptake in parallel to the insulin signalling cascade. Accordingly, foetal brown adipocytes represent a model for investigating insulin action, as well as for the mechanism by which rosiglitazone increase insulin sensitivity under situations that mimic insulin resistance.     

氧化苦参碱改善高脂诱导ApoE~(-/-)小鼠的胰岛素抵抗

目的:观察氧化苦参碱对高脂诱导胰岛素抵抗小鼠的作用并初步探讨可能机制。方法:Apo E~(-/-)小鼠高脂喂养16周,分为胰岛素抵抗组以及氧化苦参碱25、50、100 mg/kg组,C57BL/6J小鼠设为对照组,每组10只。灌胃给药8周后,进行小鼠葡萄糖耐量实验;测定血清空腹血糖(FBG)、甘油三酯(TG)、胆固醇(TC)、游离脂肪酸(FFA)和空腹胰岛素(FINS)的含量;实时荧光定量PCR测定肝组织胰岛素受体(INSR)、胰岛素受体底物-2(IRS-2)和葡萄糖转运子2(GLUT_2)的mRNA表达;Western blot法测定肝组织GLUT_2、INSR、IRS-2、p-INSR、p-IRS-2、磷脂酰肌醇3-激酶(PI3K)、p-PI3K、丝氨酸/苏氨酸蛋白激酶(AKT)和p-AKT的蛋白水平。结果:氧化苦参碱能不同程度降低FBG、TG、TC、FFA和FINS水平,改善胰岛素抵抗;氧化苦参碱组INSR、IRS-2和GLUT_2的mRNA表达比胰岛素抵抗组升高(P0.05),p-INSR/INSR、p-IRS-2/IRS-2、p-PI3K/PI3K、p-AKT/AKT和GLUT_2的蛋白水平也升高(P0.05)。结论:氧化苦参碱能通过PI3K/AKT通路,改善高脂诱导小鼠的胰岛素抵抗。