Raised serum, adipocyte, and adipose tissue retinol-binding protein 4 in overweight women with polycystic ovary syndrome: effects of gonadal and adrenal steroids

CONTEXT: Polycystic ovary syndrome (PCOS) is associated with insulin resistance and obesity. Recent studies have shown that serum retinol-binding protein 4 (RBP4) levels increase with obesity. Currently, no data exist on the relative expression of RBP4 in either serum or adipose tissue of PCOS women. OBJECTIVES: mRNA expression of RBP4 from sc and omental (om) adipose tissue and sc adipocytes in overweight PCOS women were compared with matched controls; RBP4 protein in adipose tissue and serum RBP4 levels were also assessed. Additionally, we studied the effects of testosterone, 17beta-estradiol, androstenedione, and dehydroepiandrosterone sulfate on RBP4 expression in adipose tissue explants. DESIGN: Real-time RT-PCR and Western blotting were used to assess the relative mRNA and protein expression of RBP4. Biochemical measurements were also performed. RESULTS: Compared with controls, there was significant up-regulation of RBP4 mRNA in sc (P < 0.05) and om (P < 0.01) adipose tissue as well as isolated sc adipocytes (P < 0.01) of PCOS women. In addition to elevated serum RBP4 levels in PCOS women (P < 0.05), RBP4 protein levels were significantly greater in sc and om adipose tissue of PCOS women (P < 0.05 and P < 0.05, respectively). Furthermore, in human sc and om adipose tissue explants, 17beta-estradiol significantly increased RBP4 mRNA expression, protein levels, and secretion into the culture media (P < 0.05). CONCLUSIONS: The precise reason for elevated levels of RBP4 in overweight PCOS women is unknown, but it appears that 17beta-estradiol may play a role in their regulation in adipose tissue.     

Increased visfatin messenger ribonucleic acid and protein levels in adipose tissue and adipocytes in women with polycystic ovary syndrome: parallel increase in plasma visfatin

CONTEXT: Polycystic ovary syndrome (PCOS) is a multifaceted metabolic disease linked with insulin resistance (IR) and obesity. Recent studies have shown that plasma levels of the insulin-mimetic adipokine visfatin increase with obesity. Currently, no data exist on the relative expression of visfatin in either plasma or adipose tissue of PCOS women. OBJECTIVES: We investigated the mRNA expression of visfatin from sc and omental (om) adipose tissue and sc adipocytes in women with PCOS compared with matched normal women, as well as visfatin protein in adipose tissue; plasma visfatin was also assessed. DESIGN: Real-time RT-PCR and Western blotting were used to assess the relative mRNA and protein expression of visfatin. Biochemical measurements were performed. RESULTS: There was significant up-regulation of visfatin mRNA in both sc (P < 0.05) and om (P < 0.05) adipose tissue of PCOS women, when compared with normal controls; these findings were also reflected in isolated sc adipocytes (PCOS > controls; P < 0.05). In addition to elevated plasma visfatin levels in women with PCOS (mean +/- sd, 30.2 +/- 10.4 vs. 11.2 +/- 6.2 ng/ml; P < 0.01) when compared with normal controls, visfatin protein levels were significantly greater in both sc and om adipose tissue of PCOS women (P < 0.05 and P < 0.01, respectively). CONCLUSIONS: The precise reason for the up-regulation of visfatin seen in women with PCOS, a proinflammatory state, is unknown. Additional studies are needed to clarify the potential role of visfatin in the pathophysiology of PCOS.     

Adipose Tissue Dysfunction in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disorder among premenopausal women. In addition to infertility, PCOS is associated with insulin resistance, features of the metabolic syndrome, and an increased risk for diabetes. Similar to individuals with metabolic syndrome, many women with PCOS manifest abdominal obesity, suggesting adipose tissue dysfunction. The adipose tissue of women with PCOS is characterized by hypertrophic adipocytes and impairments in lipolysis and insulin action. The expression and secretion of a wide variety of adipokines implicated in insulin resistance, including adiponectin and others, are also altered in PCOS. Collectively, the available data indicate that adipose tissue dysfunction plays a central role in the metabolic abnormalities observed in PCOS. Whether these abnormalities are primary or secondary to hyperandrogenism or other abnormalities in PCOS is not yet known.     

Secretion of adiponectin by human placenta: differential modulation of adiponectin and its receptors by cytokines

Aims/hypothesis Pregnancy, a state of insulin resistance, is associated with elevated levels of cytokines and profound alterations in metabolism. Serum adiponectin, an adipokine with anti-inflammatory and insulin-sensitising properties, has been shown to be lower in patients with gestational diabetes mellitus, a state of greater insulin resistance than normal pregnancies. Hypothesising that the human placenta is a source of adiponectin, we investigated its expression and secretion, and the regulation by cytokines of adiponectin and its receptors.Methods Real-time RT-PCR, radioimmunoassay, Western blotting, radioligand binding and immunofluorescent analyses were applied to demonstrate the expression, secretion and functionality of placental adiponectin.Results Adiponectin gene expression and protein were found in the human term placenta, with expression primarily in the syncytiotrophoblast. RIA of conditioned media from explant experiments revealed that the placenta can secrete adiponectin in vitro. Addition of conditioned media to HEK-293 cells transfected with the gene for adiponectin receptor-1 (ADIPOR1) altered the phosphorylation status of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase, an effect abolished after preabsorption with adiponectin antibody. Cytokines, including TNF-α, IFN-γ, IL-6 and leptin, differentially modulated placental adiponectin receptors as well as adiponectin gene expression and secretion. Interestingly, in placentae from women with gestational diabetes mellitus, we observed significant downregulation of adiponectin mRNA, significant upregulation of ADIPOR1 expression, and a non-significant increase in ADIPOR2 expression. Conclusions/interpretation Our results indicate that the human placenta produces and secretes adiponectin, and that adiponectin and its receptors are differentially regulated by cytokines and their expression altered in women with gestational diabetes mellitus. Collectively, our novel data suggest that adiponectin may play a role in adapting energy metabolism at the materno-fetal interface.     

Thyrotropin receptors in brown adipose tissue: thyrotropin stimulates type II iodothyronine deiodinase and uncoupling protein-1 in brown adipocytes

It has been demonstrated that TSH receptors are expressed not only in thyroid gland but also in extrathyroidal tissues. Brown adipose tissue of guinea pig has been reported to express TSH receptor messenger RNA (mRNA), but the physiological roles of TSH receptors in brown adipose tissue have not been understood. We studied the expression and function of TSH receptors in rat brown adipose tissue and cultured rat brown adipocytes. Northern analysis demonstrated the expression of TSH receptor mRNA in rat brown adipose tissue and cultured rat brown adipocytes. TSH receptor mRNA in rat brown adipose tissue was decreased by cold exposure of the rat, and its mRNA in cultured rat brown adipocytes was also decreased by incubation with TSH or (Bu)(2)cAMP. TSH increased the intracellular cAMP concentration in cultured rat brown adipocytes in a dose dependent manner. Type II iodothyronine deiodinase mRNA, its activity, and uncoupling protein-1 mRNA in cultured rat brown adipocytes were significantly increased by incubation with TSH in a dose-dependent manner. These results suggest the expression of functional TSH receptors in brown adipose tissue, which may be involved in regulation of the expression of type II iodothyronine deiodinase and uncoupling protein-1.     

肥胖小鼠脂肪组织缺氧对脂联素表达的转录抑制作用

目的观察缺氧对脂肪细胞脂联素mRNA和蛋白表达的影响,探讨肥胖小鼠脂肪组织缺氧导致脂肪组织脂联素表达下降的机制。方法采用实时定量聚合酶链反应（qRT—PCR）和蛋白免疫印迹法（Western blotting）检测遗传型肥胖小鼠（ob／ob,12周）和高脂饮食肥胖小鼠（HFD,53周）的附睾旁脂肪中脂联素mRNA和蛋白的表达;用小鼠3T3-L1脂肪细胞系为模型,采用RT—PCR和荧光素酶报告基因方法检测缺氧处理后脂联素和过氧化物酶体增殖物激活受体（PPAR）-mRNA的表达和稳定性、脂联素启动子的活性;用Western blotting和荧光素酶报告基因检测缺氧对PPAR-γ在核蛋白中集聚以及PPAR-γ转录因子活性的影响。组间数据比较采用t检验。结果（1）缺氧时两种肥胖小鼠的脂肪组织中脂联素mRNA和蛋白的表达均显著下降（P〈0．01）;333-L1脂肪细胞系在缺氧8h和24h后,脂联素mRNA表达量分别下降至0．65±0．05和0．29±0．05,较对照组（1．00±0．04）明显降低,差异有统计学意义（t=11．548、24．893,均P〈0．01）,但缺氧对脂联素mRNA的稳定性并没有影响;荧光素酶报告基因方法表明,脂联素启动子的活性受到缺氧的抑制。（2）在两种肥胖小鼠的脂肪组织中,PPAR-γmRNA和蛋白的表达均明显下降（P〈0．01）;小鼠333-L1脂肪细胞系在缺氧8h和24h后,PPAR- γmRNA的表达量分别下降至0．72±0．09和0．54±0．07,与对照组（1．00±0．09）相比,差异有统计学意义（t：5．134、9．876,均P〈0．01）;PPAR一1蛋白的核转位以及PPAR一^y转录因子活性也受到缺氧的抑制。结论肥胖小鼠脂肪组织缺氧抑制了脂联素的表达,抑制作用可能发生在转录水平;其机制可能是通过抑制PPAR-γmRNA的表达和PPAR-γ转录因子的活性而实现的。     

Changes of endocrine function of adipose tissue in anorexia nervosa: comparison of circulating levels versus subcutaneous mRNA expression

OBJECTIVE: To study the influence of chronic malnutrition in patients with anorexia nervosa on endocrine function of adipose tissue on both circulating and subcutaneous fat mRNA expression level. PATIENTS AND DESIGN: A total of 12 patients with anorexia nervosa and 18 normal weight age-matched women underwent anthropometric examination, single blood drawing and subcutaneous adipose tissue biopsy. MEASUREMENTS: Serum concentrations of high-sensitive CRP (hsCRP), leptin, soluble leptin receptor, adiponectin, resistin, interleukin-6 and insulin were measured by Luminex, enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay (RIA) kits. Subcutaneous adipose tissue mRNA expression of the same adipokines, adiponectin receptors 1 and 2 and immunocompetent cells marker CD68 was measured by real-time polymerase chain reaction (PCR). RESULTS: Decreased body fat content of patients with anorexia nervosa was accompanied by reduced hsCRP, leptin and increased adiponectin and soluble leptin receptor. Resistin, interleukin-6 and insulin levels did not differ from those of the control group. Fat mRNA adiponectin, leptin, interleukin-6 and CD68 expression was reduced, resistin mRNA expression was increased and adiponectin receptor 1 and 2 expression were unchanged as compared to the control group. CONCLUSIONS: Local perturbations in resistin, adiponectin and interleukin-6 mRNA expression in subcutaneous adipose tissue are not reflected by its circulating levels. These changes could be involved in some local metabolic disturbances in subcutaneous adipose tissue of anorexia nervosa patients.     

Response of adipose tissue to early infection with Trypanosoma cruzi (Brazil strain)

Brown adipose tissue (BAT) and white adipose tissue (WAT) and adipocytes are targets of Trypanosoma cruzi infection. Adipose tissue obtained from CD-1 mice 15 days after infection, an early stage of infection revealed a high parasite load. There was a significant increase in macrophages in infected adipose tissue and a reduction in lipid accumulation, adipocyte size, and fat mass and increased expression of lipolytic enzymes. Infection increased levels of Toll-like receptor (TLR) 4 and TLR9 and in the expression of components of the mitogen-activated protein kinase pathway. Protein and messenger RNA (mRNA) levels of peroxisome proliferator-activated receptor γ were increased in WAT, whereas protein and mRNA levels of adiponectin were significantly reduced in BAT and WAT. The mRNA levels of cytokines, chemokines, and their receptors were increased. Nuclear Factor Kappa B levels were increased in BAT, whereas Iκκ-γ levels increased in WAT. Adipose tissue is an early target of T. cruzi infection.     

TNFalpha release by the nonfat cells of human adipose tissue

OBJECTIVE: The primary aim was to investigate the relative importance of the adipocytes vs the nonfat cells present in human adipose tissue with respect to release of immunoreactive tumor necrosis factor-alpha (TNFalpha). The second aim was to examine the correlation between body mass index (BMI) and the subsequent release of adiponectin and TNFalpha by explants of human subcutaneous and visceral adipose tissue incubated in primary culture for 48 h. RESULTS: We found that the maximal release of TNFalpha was seen during the first 4 h of a 48-h incubation by explants of human adipose tissue in primary culture. Over 95% of the TNFalpha released to the medium by human adipose tissue explants over a 4-h incubation came from the nonfat cells present in the adipose tissue. The release of TNFalpha by the nonfat cells released during collagenase digestion was slightly higher than that by the cells present in the adipose tissue matrix after collagenase digestion. TNFalpha release by the combined matrix and isolated nonfat cells was greater than that by explants of tissue indicating some upregulation induced by collagenase digestion. Immunoreactive TNFalpha disappeared from the medium with a half-time of approximately 10 h. There was a positive correlation coefficient of 0.79 between TNFalpha release by tissue explants and the BMI of the fat donors as well as a correlation of 0.52 between BMI and release by adipocytes. TNFalpha release negatively correlated [-0.60] with adiponectin release by adipose tissue. The release of TNFalpha was far less than that of adiponectin or IL-6, and less than that of plasminogen activator inhibitor-1, hepatocyte growth factor, or leptin over a 4-h incubation of human adipose tissue explants. TNFalpha release over 4 h was enhanced by lipopolysaccharide and inhibited by a cyclooxygenase-2 inhibitor. CONCLUSION: The release of TNFalpha by adipose tissue of obese humans is primarily due to the nonfat cells present in adipose tissue. TNFalpha is a short-lived adipokine whose release by human adipose tissue in primary culture correlates with the BMI of the fat donors.