María Insenser

Circulating markers of oxidative stress and polycystic ovary syndrome (PCOS): a systematic review and meta-analysis

BACKGROUND Oxidative stress might be associated with polycystic ovary syndrome (PCOS), but relatively small studies published to date do not permit reaching a definitive conclusion. We aimed at conducting a systematic review and meta-analysis of studies evaluating circulating markers of oxidative stress in patients with PCOS. METHODS We conducted a systematic review of studies reporting circulating markers of oxidative stress in women with PCOS and controls published up to June 2012, using Entrez PubMed and EMBASE online facilities. Meta-analysis calculated standardized mean differences (SMDs) and 95% confidence intervals (95CI). RESULTS From 1633 potential studies identified electronically, 68 studies, including 4933 PCOS patients and 3671 controls, were selected. For each of nine circulating markers of oxidative stress, an individual meta-analysis was conducted. Compared with control women, patients with PCOS presented higher circulating concentrations of homocysteine (23% increase, SMD 0.6, 95CI, 0.4-0.8), malondialdehyde (47% increase, SMD 1.9, 95CI 1.2-2.6) and asymmetric dimethylarginine (36% increase, SMD 1.1, 95CI 0.6-1.6), and increased superoxide dismutase activity (34% increase, SMD 1.0, 95CI 0.5-1.4) and decreased glutathione levels (50% decrease, SMD -3.7, 95CI -6.2 to -1.2) and paraoxonase-1 activity (32% decrease, SMD -0.9, 95CI -1.3 to -0.4). Similar results were found when restricting the analyses to studies in which patients and controls were matched for age and body mass index. CONCLUSIONS Circulating markers of oxidative stress are abnormal in women with PCOS independent of weight excess. This finding suggests that oxidative stress may participate in the pathophysiology of this common disorder.

Effects of Polycystic Ovary Syndrome (PCOS), Sex Hormones, and Obesity on Circulating miRNA-21, miRNA-27b, miRNA-103, and miRNA-155 Expression

CONTEXT MicroRNAs (miRNAs) are small, noncoding RNA sequences that negatively regulate gene expression at the post-transcriptional level. miRNA-21, miRNA-27b, miRNA-103, and miRNA-155 have been associated with metabolic disorders such as obesity and diabetes, which are also associated with polycystic ovary syndrome (PCOS). OBJECTIVE We aimed to evaluate the effects of sex, sex hormones, and PCOS and their interactions with obesity on the expression in the circulation of these miRNAs. DESIGN This was a case-control study. SETTINGS The setting was an academic hospital. PARTICIPANTS We included 12 control women, 12 patients with PCOS, and 12 men selected as to have similar body mass index (BMI) and age. Six subjects per group had normal weight (BMI < 25 kg/m(2)), and six subjects per group were obese (BMI ≥ 30 kg/m(2)). INTERVENTIONS Blood samples were collected early in the morning after a 12-hour fast. MAIN OUTCOME MEASURES We measured whole blood expression of miRNA-21, miRNA-27b, miRNA-103, and miRNA-155. RESULTS Obesity significantly reduced the expression of miRNA-21, miRNA-27b, and miRNA-103. However, there was a significant interaction between obesity and the group of subjects in the expression of miRNA-21, miRNA-27b, miRNA-103, and miRNA-155 consisting of obesity reducing the expression of these miRNAs in control woman and men, but tending to increase their expression in women with PCOS. These differences paralleled those observed in serum T concentrations. CONCLUSIONS The present results suggest that miRNAs that play an important role in metabolic and immune system processes are influenced by obesity and circulating androgen concentrations.

Metabolic Heterogeneity in Polycystic Ovary Syndrome Is Determined by Obesity: Plasma Metabolomic Approach Using GC-MS

BACKGROUND Abdominal adiposity and obesity influence the association of polycystic ovary syndrome (PCOS) with insulin resistance and diabetes. We aimed to characterize the intermediate metabolism phenotypes associated with PCOS and obesity. METHODS We applied a nontargeted GC-MS metabolomic approach to plasma samples from 36 patients with PCOS and 39 control women without androgen excess, matched for age, body mass index, and frequency of obesity. RESULTS Patients with PCOS were hyperinsulinemic and insulin resistant compared with the controls. The increase in plasma long-chain fatty acids, such as linoleic and oleic acid, and glycerol in the obese patients with PCOS suggests increased lipolysis, possibly secondary to impaired insulin action at adipose tissue. Conversely, nonobese patients with PCOS showed a metabolic profile consisting of suppression of lipolysis and increased glucose utilization (increased lactic acid concentrations) in peripheral tissues, and PCOS patients as a whole showed decreased 2-ketoisocaproic and alanine concentrations, suggesting utilization of branched-chain amino acids for protein synthesis and not for gluconeogenesis. These metabolic processes required effective insulin signaling; therefore, insulin resistance was not universal in all tissues of these women, and different mechanisms possibly contributed to their hyperinsulinemia. PCOS was also associated with decreased α-tocopherol and cholesterol concentrations irrespective of obesity. CONCLUSIONS Substantial metabolic heterogeneity, strongly influenced by obesity, underlies PCOS. The possibility that hyperinsulinemia may occur in the absence of universal insulin resistance in nonobese women with PCOS should be considered when designing diagnostic and therapeutic strategies for the management of this prevalent disorder.

A nontargeted proteomic approach to the study of visceral and subcutaneous adipose tissue in human obesity

Subcutaneous (SAT) and visceral adipose tissue (VAT) differ in biochemical and metabolic properties, especially when obesity is present. We submitted paired SAT and VAT samples from six morbidly obese patients and six non-obese persons to two-dimensional differential gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight/time-of-flight mass spectrometry. Compared with non-obese subjects, obese patients presented with increased carboxylesterase-1, zinc finger protein 324A, annexin A5, ubiquitin carboxyl-terminal hydrolase, α-crystallin B chain, osteoglycin, retinal dehydrogenase-1 and 14-3-3 protein γ, and decreased transferrin, complement C3, fibrinogen γ chain, albumin, α1-antitrypsin and peroxiredoxin-6, irrespective of the adipose tissue depot studied. SAT and VAT differed in protein species of fibrinogen and osteoglycin, whereas adipose tissue depot and obesity interacted on the protein abundance of actin, α-actinin 1, one protein species of carboxylesterase-1, retinal dehydrogenase-1 and 14-3-3 protein γ. Our nontargeted proteomic approach identified novel protein species that may be involved in the development of obesity in humans.

Proteomic analysis of plasma in the polycystic ovary syndrome identifies novel markers involved in iron metabolism, acute-phase response, and inflammation.

CONTEXT Hypothesis-free approaches such as proteomic analysis may identify novel biomarkers for disease. OBJECTIVE The objective of the study was to compare the plasma proteome of patients presenting with the polycystic ovary syndrome (PCOS) with that of women without hyperandrogenism. DESIGN This was a case-control study. SETTINGS The study was conducted at an academic hospital. PATIENTS Patients included 12 PCOS patients and 12 women without hyperandrogenism. INTERVENTIONS Interventions included basal blood sampling. MAIN OUTCOME MEASURES Two-dimensional difference in-gel electrophoresis, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry, Western blot, and ELISA analyses were measured. RESULTS Two-dimensional difference in-gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry analyses identified haptoglobin beta-chain and alpha2-macroglobulin as proteins underexpressed in PCOS samples, whereas transferrin and kappa-free light chain were overexpressed. We were able to confirm only the underexpression of haptoglobin beta-chain in subsequent Western blot and ELISA analyses. CONCLUSIONS Proteomic analysis of plasma from PCOS patients revealed changes in protein expression in several acute-phase response proteins including isoforms of plasma haptoglobin, alpha2-macroglobulin, and transferrin and in kappa-free light chain. In addition to their role as inflammatory markers, some of these molecules play major roles in iron metabolism, further suggesting that iron metabolism and low-grade chronic inflammation may be involved in the pathogenesis of insulin-resistant disorders such as PCOS.

Proteomic and metabolomic approaches to the study of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is considered a complex multifactorial disorder resulting from the interaction of genetic, environmental, and lifestyle influences. Nontargeted proteomics and metabolomics have been used in the past years with the aim of identifying molecules potentially involved in the pathophysiology of this frequent disorder. The biomolecules identified so far participate in many metabolic pathways, including energy metabolism (glucose and lipid metabolism), protein metabolic processes and protein folding, cytoskeleton structure, immune response, inflammation and iron metabolism, fibrinolysis and thrombosis, oxidative stress and intracellular calcium metabolism. These molecules provide key information about molecular functions altered in PCOS and raise questions concerning their precise role in the pathogenesis of this syndrome. The biomolecules identified by nontargeted proteomic and metabolomic approaches should be considered as candidates in future studies aiming to define specific molecular phenotypes of PCOS.

Evidence for masculinization of adipokine gene expression in visceral and subcutaneous adipose tissue of obese women with polycystic ovary syndrome (PCOS).

CONTEXT Sex hormones, particularly androgens, may influence not only adipose tissue distribution but also its functions. OBJECTIVE We explored the possibility of sexual dimorphism in adipose tissue and skeletal muscle function. DESIGN This was a case-control study. SETTING The setting was an academic hospital. PARTICIPANTS Participants were severely obese men (n = 7), control women (n = 7), and hyperandrogenic women presenting with polycystic ovary syndrome (PCOS) (n = 7) submitting to bariatric surgery and an independent series of 40 patients with PCOS and 40 control women matched for age and body mass index. INTERVENTIONS Samples of subcutaneous (SAT) and visceral adipose tissue (VAT) and skeletal muscle were obtained during bariatric surgery in severely obese subjects. MAIN OUTCOME MEASURES Gene expression of chemerin, lipocalin-2, and omentin-1 in tissue samples was measured. We analyzed the effects of PCOS and obesity on serum concentrations of these adipokines in the larger series of women with PCOS and in control women. RESULTS Expression of chemerin and lipocalin-2 was higher in VAT than in SAT in men and women with PCOS; the opposite was observed in control women. Omentin-1 expression was higher in VAT than in SAT in the three groups. No differences were observed in the skeletal muscle expression of these adipokines. Obesity increased serum chemerin and lipocalin-2 levels and tended to decrease omentin-1, irrespective of PCOS. CONCLUSIONS The present results suggest that there is sexual dimorphism in some adipose tissue functions and that this dimorphism may be related to differences in androgen concentrations because women with PCOS show a masculinized pattern of expression of some adipokines.

Sexual dimorphism in adipose tissue function as evidenced by circulating adipokine concentrations in the fasting state and after an oral glucose challenge

STUDY QUESTION Do the circulating levels of a panel of adipokines involved in glucose metabolism exhibit sexual dimorphism in the fasting state and after an oral glucose load? SUMMARY ANSWER Our results indicate sexual dimorphism in the circulating concentrations of adipokines involved in intermediate metabolism in the fasting state and during an oral glucose load. This finding suggests an influence of sex steroids on adipose tissue function. WHAT IS KNOWN ALREADY Sexual dimorphism in adipose tissue distribution fully develops after puberty and modulates the risk for cardiometabolic disorders. However, the possibility that adipose tissue function exhibits sexual dimorphism as well as its distribution is unproved. STUDY DESIGN, SIZE, DURATION Cross-sectional case-control study including 32 subjects. PARTICIPANTS/MATERIALS, SETTING, METHODS Sixteen subjects with weight excess (8 men and 8 women, including 4 overweight and 4 obese subjects in each group) and 16 normal weight healthy volunteers (8 men and 8 women) presenting with similar age were submitted to a 75-g oral glucose tolerance test (oGTT). We measured circulating concentrations of insulin, glucose, chemerin, lipocalin-2, omentin-1, leptin and adiponectin and calculated their areas under the oGTT curve (AUC). MAIN RESULTS AND THE ROLE OF CHANCE Leptin and adiponectin concentrations were higher throughout the oGTT in women compared with men. Lipocalin-2 concentrations decreased during the oGTT in the whole group of study subjects. However, these levels remained higher in men with weight excess compared with normal weight men, whereas in women with weight excess lipocalin-2 levels at the end of the oGTT were lower compared with normal weight women. Sex was among the main determinants of the AUC of omentin-1 and leptin in linear regression models, and lower estradiol and testosterone concentrations were related to higher AUC of chemerin and omentin-1, respectively. Subjects with weight excess had higher AUC of chemerin and leptin and lower AUC of omentin-1 and adiponectin levels, independently of sex. LIMITATIONS, REASONS FOR CAUTION We included a relatively small sample size and, because this was a cross-sectional study, we cannot infer causality to the associations between the changes in circulating adipokine concentrations and the variables studied here. WIDER IMPLICATIONS OF THE FINDINGS Sexual dimorphism in adipose tissue function should be considered when studying adiposity and obesity, and also when designing strategies for their diagnosis and management.

A Nontargeted Proteomic Study of the Influence of Androgen Excess on Human Visceral and Subcutaneous Adipose Tissue Proteomes

CONTEXT Sex hormones, particularly androgens, may influence not only adipose tissue distribution but also its functions. OBJECTIVE We aimed to evaluate if sexual dimorphism in body composition is accompanied by differences in the protein abundance of adipose tissue by applying a nontargeted proteomic approach. DESIGN This was a case-control study. SETTINGS The setting was an academic hospital. PATIENTS Twenty-one morbidly obese patients, including 7 men, 7 women showing no evidence of androgen excess, and 7 hyperandrogenic women with polycystic ovary syndrome. INTERVENTIONS We obtained subcutaneous (SAT) and visceral (VAT) adipose tissue samples during bariatric surgery. MAIN OUTCOME MEASURES Protein abundance in VAT and SAT was analyzed by 2-dimensional differential gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight/time-of-flight coupled to mass spectrometry. Results were validated by RT-PCR. RESULTS The abundance of 2 spots of peroxiredoxin 6, creatine kinase B-type, 2 spots of selenium-binding protein 1, ruvB-like 2, 4-trimethylaminobutyraldehyde dehydrogenase, and albumin were higher in VAT compared with SAT in women with polycystic ovary syndrome. Men showed a similar pattern, whereas no difference between adipose tissue depots was observed in control women. Other proteins showed differences between VAT and SAT, confirming previous studies, or between the groups of subjects, without interaction between both effects. Several findings were confirmed by RT-PCR. CONCLUSIONS Sexual dimorphism influences the abundance of several proteins in VAT and SAT. The patterns of abundance in adipose tissue depots of several proteins involved in metabolic processes were similar in women with androgen excess and in men, suggesting that androgens influence adipose tissue function.

Mediators of Low-Grade Chronic Inflammation in Polycystic Ovary Syndrome (PCOS)

Chronic low-grade subclinical inflammation has been increasingly recognized as an interposer in the endocrine, metabolic and reproductive disturbances that characterize the polycystic ovary syndrome (PCOS). Abdominal adiposity and obesity are often present in PCOS. Mounting evidence indicates that adipose tissue is involved in innate and adaptive immune responses. Continuous release of inflammatory mediators such as cytokines, acute phase proteins, and adipokines perpetuates the inflammatory condition associated with obesity in women with PCOS, possibly contributing to insulin resistance and other long-term cardiometabolic risk factors. Genetic variants in the genes encoding inflammation-related mediators underlie the development of PCOS and their interaction with environmental factors may contribute to the heterogeneous clinical phenotype of this syndrome. In the future, strategies ameliorating inflammation may prove useful for the management of PCOS and associated conditions.