Genetic variants in peroxisome proliferator-activated receptor gamma influence insulin resistance and testosterone levels in normal women, but not those with polycystic ovary syndrome

The Role of Peroxisome Proliferator-Activated Receptors in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) constitutes the most common endocrine disorder in women of reproductive age. Patients usually suffer from severe menstrual irregularities, skin conditions, and insulin resistance-associated health conditions. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptor proteins that regulate gene expression. In order to investigate the role of PPARs in the pathophysiology of PCOS, we conducted a literature review using the MEDLINE and LIVIVO databases and were able to identify 74 relevant studies published between 2003 and 2023. Different study groups reached contradictory conclusions in terms of PPAR expression in PCOS. Interestingly, numerous natural agents were found to represent a novel, potent anti-PCOS treatment alternatives. In conclusion, PPARs seem to play a significant role in PCOS.

The role of polymorphism in various potential genes on polycystic ovary syndrome susceptibility and pathogenesis

Polycystic ovary syndrome (PCOS) is the most common endocrinopathies affecting the early reproductive age in women, whose pathophysiology perplexes many researchers till today. This syndrome is classically categorized by hyperandrogenism and/or hyperandrogenemia, menstrual and ovulatory dysfunction, bulky multi follicular ovaries on Ultrasonography (USG), and metabolic abnormalities such as hyperinsulinemia, dyslipidemia, obesity. The etiopathogenesis of PCOS is not fully elucidated, but it seems that the hypothalamus-pituitary-ovarian axis, ovarian, and/or adrenal androgen secretion may contribute to developing the syndrome. Infertility and poor reproductive health in women's lives are highly associated with elevated levels of androgens. Studies with ovarian theca cells taken from PCOS women have demonstrated increased androgen production due to augmented ovarian steroidogenesis attributed to mainly altered expression of critical enzymes (Cytochrome P450 enzymes: CYP17, CYP21, CYP19, CYP11A) in the steroid hormone biosynthesis pathway. Despite the heterogeneity of PCOS, candidate gene studies are the widely used technique to delineate the genetic variants and analyze for the correlation of androgen biosynthesis pathway and those affecting the secretion or action of insulin with PCOS etiology. Linkage and association studies have predicted the relationship between genetic variants and PCOS risk among families or populations. Several genes have been proposed as playing a role in the etiopathogenesis of PCOS, and the presence of mutations and/or polymorphisms has been discovered, which suggests that PCOS has a vital heritable component. The following review summarizes the influence of polymorphisms in crucial genes of the steroidogenesis pathway leading to intraovarian hyperandrogenism which can result in PCOS.

Potential environmental toxicant exposure, metabolizing gene variants and risk of PCOS-A systematic review

Exposure of environmental toxicants such as potentially toxic metals and pesticides have largely been attributed to produce adverse effects on general women's health and to be more precise on the reproductive system. In order to explore exposure of toxicants and metabolizing gene variants as risk factor for polycystic ovarian syndrome (PCOS), literature search was carried out using the databases PubMed, Central Cochrane Library, Google Scholar, Science Direct with appropriate keywords upto 6 December 2020. While most of the studies indicate higher serum Cu concentration and lower concentration of Mn as risk factor, studies also report presence of higher pesticide concentration in PCOS women. Genes such as MTHFR, CYPs participate in the metabolism of toxicants and may show different response due to underlying genetic variants. Thus, toxicant exposure are to some extent responsible for the pathogenesis of syndrome through oxidative stress and endocrine disruption, but the susceptibility may vary due to the underlying genetic polymorphism of the exposed population.

Hyperandrogenism in POMCa-deficient zebrafish enhances somatic growth without increasing adiposity

The endocrine regulatory roles of the hypothalamic-pituitary-adrenocortical axis on anxiety-like behavior and metabolic status have been found throughout animal taxa. However, the precise effects of the balancing adrenal corticosteroid biosynthesis under the influence of adrenocorticotrophic hormone (ACTH), a pro-opiomelanocortin (POMC)-derived peptide, on animal energy expenditure and somatic growth remain unknown. POMC has also been identified as one of the candidate loci for polycystic ovary syndrome, which features hyperandrogenism and some prevalence of obesity in patients. Here we show that zebrafish lacking functional POMCa exhibit similar phenotypes of stress response and body weight gain but not obesity as observed in mammalian models. In contrast with the impaired anorexigenic signaling cascade of melanocyte-stimulating hormones and leptin, which are responsible for their obesity-prone weight gain observed in various pomc mutant mammals, analyses with our pomca mutant series indicate that ACTH is the key regulator for the phenotype with enhanced somatic growth without obesity in pomca-deficient zebrafish. Hypocortisolism associated with hyperandrogenism has been observed in the pomca-deficient zebrafish, with enhanced activation of mammalian target of rapamycin complex 1; reutilization of amino acids and fatty acid β-oxidation are observed in the muscle tissue of the pomca-deficient fish. After reducing hyperandrogenism by crossing our pomca mutant fish with a cyp17a1-deficient background, the phenotype of enhanced somatic growth in pomca-deficient fish was no longer observed. Thus, our work also demonstrated that the role of POMCa in stress response seems to be conserved in vertebrates, whereas its effect on adipostasis is unique to teleosts.

Influence of peroxisome proliferator-activated receptor-γ exon 2 and exon 6 and insulin receptor substrate (IRS)-1 Gly972Arg polymorphisms on insulin resistance and beta-cell function in southern mediterranean women with polycystic ovary syndrome

Background and objective

The Pro12Ala (exon 2) and His447His (exon 6) polymorphisms of PPAR-γ, and Gly972Arg polymorphism of IRS-1 have been implicated in insulin resistance (IR) and adiposity. Our aim was to investigate the influence of these polymorphisms on metabolic features of polycystic ovary syndrome (PCOS).

Methods

Fifty-three PCOS women and 26 control women underwent a clinical and biochemical evaluation, including a 75-g oral glucose tolerance test. Insulin secretion and insulin sensitivity indices were calculated.

Results

Frequencies of PPAR-γ polymorphisms did not differ from those predicted by the Hardy-Weinberg equilibrium. Instead, the IRS-1 Gly972Arg allele was significantly more frequent in the PCOS group compared to controls. The most frequent allelic combinations were IRS1+/exon2-/exon6- (which prevailed in PCOS) and IRS-1-/exon2-/exon6- (which prevailed in controls). Among PCOS women, compared with the wild type patients, carriers of the Gly972Arg IRS-1 allele had lower E2 levels, while carriers of the Pro12Ala PPAR-γ (exon 2) allele had lower free testosterone levels. No other significant relationships were noted. When compared with the wild type, in PCOS group IR and beta-cell function were: (i) trendwise greater in carriers of the variant IRS-1 allele; (ii) trendwise lower in carriers of the variant PPAR-γ exon 6 allele; (iii) significantly lower in carriers of the variant PPAR-γ exon 2 allele.

Conclusions

Our data support the protective influence of PPAR-γ-exon 2 and exon 6 variants on IR and beta cell function, whereas IRS-1 polymorphism is associated with an unfavorable metabolic profile. However, these associations do not fully explain the high metabolic risk associated with PCOS.

The Association of PPARγ Pro12Ala and C161T Polymorphisms with Polycystic Ovary Syndrome and Their Influence on Lipid and Lipoprotein Profiles

BACKGROUND

The aim of present study was to clarify the role of the peroxisome proliferator-activated receptor (PPAR) γ Pro12Ala and C161T polymorphisms in the pathogenesis of polycystic ovary syndrome (PCOS) and their influence on lipid and lipoprotein profiles of patients.

MATERIALS AND METHODS

The present cross-sectional study consisted of 50 women with PCOS, who referred to the Kermanshah University of Medical Sciences Clinic between April and October 2015, and 233 unrelated age-matched healthy women from the same region (West Iran). The PPARγ Pro12Ala and PPARγ C161T polymorphisms were genotyped using the polymerase chain reaction-restriction fragment length polymorphism method. Fasting blood sugar (FBS), serum triglycerides (TG), cholesterol, low density lipoprotein- cholesterol (LDL-C), high density lipoproteincholesterol (HDL-C) and estradiol levels were measured.

RESULTS

The serum level of estradiol was significantly lower in PCOS patients compared to healthy women. The PPARγ Pro12Ala (CG) genotype increased the risk of PCOS 2.96-fold. The frequency of the PPARγ T allele (at C161T) was 21% in patients and 17.2% in controls with no significant difference (P=0.52). In all studied individuals, the PPARγ CG genotype was associated with significantly higher levels of TG. However, significantly lower levels of total cholesterol and LDL-C were observed in PPARγ TT individuals compared with those with the CC genotype. Within the PCOS group, the PPARγ CG genotype was significantly associated with lower levels of estradiol compared with the CC genotype. Also, the CG genotype was significantly associated with higher levels of TG when compared with the CC genotype.

CONCLUSION

Our study shows that, unlike PPARγ C161T, PPARγ Pro12Ala is associated with the risk of PCOS. Also, we found that the lipid and lipoprotein profiles significantly vary based on PPARγ Pro12Ala and C161T genotypes.

Association of the Pro12Ala Polymorphism with the Metabolic Parameters in Women with Polycystic Ovary Syndrome

AIM:

To investigate the association of peroxisome proliferator-activated receptor gamma (PPARG) Pro12Ala polymorphism with polycystic ovary syndrome (PCOS) and its effect on the metabolic parameters in PCOS women.

METHODS:

The study used PCR to identify the presence of the PPARG Pro12Ala polymorphism in 100 PCOS women and 120 age-matched healthy women. All participants were subjected to anthropometry, biochemical and metabolic evaluation.

RESULTS:

Significant difference in the genotypes distributions of PPARG Pro12Ala polymorphism was observed among PCOS women and controls (p = 0.03). The frequency of the polymorphic allele Ala was significantly higher in PCOS cases than that in the controls (OR = 2.01, p = 0.01). The carries of the variant allele Ala in PCOS women showed significant higher values in body mass index (BMI), systolic and diastolic blood pressure, waist circumference, waist to hip ratio, sum of skin folds, fasting blood glucose, fasting blood insulin, HOMA-IR, fasting triglycerides, total cholesterol and low-density lipoprotein than non-carriers.

CONCLUSION:

The PPARG Pro12Ala polymorphism might contribute to the risk of PCOS and abnormal metabolic parameters and could be considered as a biomarker for early diagnosis and clinic prediction of metabolic complications.

Peroxisome proliferator-activated receptor gamma rs1801282 C>G polymorphism is associated with polycystic ovary syndrome susceptibility: a meta-analysis involving 7,069 subjects

In the peroxisome proliferator-activated receptor gamma (PPARG) gene, a polymorphism (rs1801282 C>G), has been shown to change an amino acid residue and then results in alternation of PPARG function. A number of studies have explored the relationship between PPARG rs1801282 C>G variants and polycystic ovary syndrome (PCOS) risk, but yielding inconsistent findings, especially in Asian population. This study aimed to assess the role of PPARG rs1801282 C>G polymorphism in susceptibility to PCOS. Databases of Pubmed, Embase and China National Knowledge Internet (CNKI) were searched until August 2, 2015. The association of PPARG 1801282 C>G polymorphism with PCOS risk was evaluated by crude odds ratios (ORs) with their 95% confidence intervals (CIs). Finally, there were twenty-three studies involving 3,458 PCOS cases and 3,611 controls included in our pooled analysis. Significant associations were identified between PPARG rs1801282 C>G variants and decreased PCOS risk in three genetic comparison models (OR, 0.78; 95% CI, 0.69-0.89; P < 0.001 for G vs. C; OR, 0.77; 95% CI, 0.68-0.89; P < 0.001 for GG+CG vs. CC and OR, 0.79; 95% CI, 0.68-0.91; P = 0.001 for CG vs. CC). In a subgroup analysis by race, significant correlation was also observed between PPARG rs1801282 C>G variants and decreased PCOS risk in three genetic models: G vs. C (OR, 0.83; 95% CI, 0.71-0.97; P = 0.019) and GG+CG vs. CC (OR, 0.83; 95% CI, 0.70-0.99; P = 0.033) among Caucasians and in one genetic models: G vs. C (OR, 0.72; 95% CI, 0.59-0.88; P = 0.001) among Asians. In summary, our results demonstrate that PPARG rs1801282 C>G polymorphism may be a protective factor for PCOS.

Association of PPARG Pro12Ala polymorphism with insulin sensitivity and body mass index in patients with polycystic ovary syndrome

Insulin resistance is one of the key factors in the pathogenesis of polycystic ovary syndrome (PCOS). The peroxisome proliferator-activated receptor gamma (PPARG) plays a role in the regulation of insulin sensitivity. The aim of the present study was to establish a possible association of the PPARG Pro12Ala polymorphism with PCOS and its effect on family and personal history, as well as on the metabolic and endocrine parameters in PCOS patients. A total of 151 PCOS patients and 179 healthy women of reproductive age were enrolled. History, body mass index (BMI), waist-to-hip ratio and the presence of phenotypic hyperandrogenism were recorded. Hormonal, metabolic and biochemical profiles were assessed. A molecular analysis for the genetic polymorphism was performed. One third (29.8%) of the PCOS patients were found to be carriers of at least one variant of the Ala allele (X/Ala), while 70.2% carried two wild-type Pro alleles (Pro/Pro), with an equal distribution observed in the control group. The PCOS patients carrying the X/Ala alleles exhibited lower serum fasting insulin levels, homeostatic model assessment of insulin resistance (HOMA-IR) and BMI compared to Pro/Pro carriers. This finding was significant only in the lean PCOS group. The polymorphic genotype exerted no effect on history, hormonal and clinical hyperandrogenism, lipid status or C-reactive protein, leptin, adiponectin, resistin and ghrelin serum levels in women with PCOS. In conclusion, although the PPARG Pro12Ala polymorphism is not a major determinant of PCOS in the Croatian population, it may exert a positive effect on insulin sensitivity and BMI. As these associations were recorded exclusively in the lean group of patients with PCOS, this polymorphism potentially contributes to a protective role against hyperinsulinemia and obesity.

Genetic variants associated with insulin signaling and glucose homeostasis in the pathogenesis of insulin resistance in polycystic ovary syndrome: a systematic review

BACKGROUND

Polycystic ovary syndrome must be recognized as a serious issue due to its implication on long term health regardless of an individual's age. PCOS and insulin resistance are interlinked, as approximately 40 % of women with PCOS are insulin resistant. However, the detailed molecular basis for insulin resistance that is coupled with PCOS remains poorly understood.

OBJECTIVE

To review the published evidence that polymorphisms in genes that are involved in insulin secretion and action are associated with an increased risk of PCOS.

METHODS

We reviewed articles published through November 2012 which concerned polymorphisms of genes related to insulin signaling and glucose homeostasis as well as their associations with PCOS. The articles were identified via Medline searches.

CONCLUSIONS

No consistent evidence emerged of a strong association between the risk of PCOS and any known gene that is related to insulin signaling and glucose homeostasis. Moreover, recent genome-wide association studies are inconsistent in identifying the associations between PCOS and insulin metabolism genes. Many of the studies reviewed were limited by heterogeneity in the PCOS diagnosis and by not have having a sufficient number of study participants. Further studies are warranted to determine predisposing risk factors which could modify environmental factors and thus reduce the risk of PCOS. Large genome-wide association studies devoted solely to PCOS will be necessary to identify new candidate genes and proteins that are involved in PCOS risk.

Peroxisome proliferator activated receptor gamma gene variants influence susceptibility and insulin related traits in Indian women with polycystic ovary syndrome

PURPOSE

Peroxisome proliferator activated receptor gamma (PPARγ), a transcription factor involved in glucose and lipid metabolism is one of the candidate genes associated with polycystic ovary syndrome (PCOS). We investigated individual and combined associations of Pro12Ala and His447His polymorphisms of PPARγ with PCOS susceptibility and its related traits (hyperinsulinemia, hyperandrogenemia and lipid parameters) in Indian women.

METHOD

Genotyping of PPARγ polymorphisms in this case-control study was performed in PCOS (n = 450) and age-matched controls (n = 300) by direct sequencing. Clinical, anthropometric, hormonal and metabolic parameters were estimated in 275 women with PCOS and 169 controls. Chi-square test was used to compare the categorical data while regression analysis was used to evaluate association of genotypes with PCOS as well as its related phenotypes.

RESULTS

The frequencies of CC and CG + GG genotypes of Pro12Ala (χ² = 15.3, p < 0.0001) and CC and CT + TT genotypes of His447His (χ² = 12.7, p = 0.0004) polymorphisms were significantly different between PCOS and controls. Logistic regression analysis revealed a significant association of PCOS with Pro12Ala but not the His447His polymorphism. Carriers of variant genotypes at both PPARγ loci showed significantly reduced 2 h glucose levels while carriers of variant His447His genotype showed lower fasting insulin and HOMA-IR levels in PCOS women.

CONCLUSIONS

Pro12Ala polymorphism of PPARγ showed significant association with decreased PCOS susceptibility. Both polymorphisms influenced insulin related traits (2 h glucose, fasting insulin and HOMA-IR) and improved glucose metabolism in these women. This is the first report to establish that variations in PPARγ gene influence the insulin resistance pathophysiology in Indian women with PCOS.

Apolipoprotein A-IV as a novel gene associated with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common endocrine-metabolic disorder, affecting 6-10% of women of reproductive age. The etiology remains poorly understood. To investigate the differentially expressed proteins from PCOS patients versus healthy women, the protein expression in follicular fluid was analyzed using two-dimensional electrophoresis (2-DE). Since follicular fluid contains a number of secretory proteins required for oocyte fertilization and follicle maturation, it is possible that follicular fluid can be used as a provisional source for identifying pivotal proteins associated with PCOS. In this study, six overexpressed proteins [kininogen 1, cytokeratin 9, antithrombin, fibrinogen γ-chain, apolipoprotein A-IV (apoA-IV) precursor and α-1-B-glycoprotein (A1BG)] in follicular fluids from PCOS patients were identified with matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF-MS) and nano LC-MS/MS. Western blot analysis confirmed that the protein expression levels of apoA-IV precursor and A1BG were increased in follicular fluid from PCOS patients compared with those from normal controls. The analysis of protein expression for other proteins revealed individual variation. These results facilitate the understanding of the molecular mechanisms of PCOS and provide candidate biomarkers for the development of diagnostic and therapeutic tools.

A meta-analysis on the association between PPAR-γ Pro12Ala polymorphism and polycystic ovary syndrome

PURPOSE

To investigate the influence of the peroxisome proliferator activated receptor gamma (PPAR-γ) Pro12Ala polymorphism on the susceptibility of polycystic ovary syndrome (PCOS) and body mass index (BMI), fast insulin levels, homeostasis model assessment of insulin resistance (HOMA-IR) in PCOS patients.

METHODS

PubMed, EMBASE, MEDLINE and CENTRAL databases were searched to identify eligible studies. We then conducted a meta-analysis to examine the association between Pro12Ala polymorphism and PCOS.

RESULTS

Seventeen eligible studies, including 2,149 patients and 2,124 controls were enrolled in this meta-analysis. Pro12Ala polymorphism was significantly associated with the susceptibility of PCOS (odds ratio [OR] 0.74, 95 % confidence interval [CI] [0.61, 0.90] for allele; OR 0.70, 95 % CI [0.57, 0.86] for genotype). In the European subgroup of PCOS, the X/Ala genotype was associated with lower BMI (mean difference [MD] -1.08, 95 % CI [-2.08, -0.09]) and fast insulin levels (MD -19.82, 95 % CI [-34.07, -5.58]). However, this polymorphism did not display an impact on HOMA-IR in PCOS patients.

CONCLUSIONS

Ala variant would decrease the risk of PCOS and result in lower BMI and fast insulin levels in a European population, but had no impact on HOMA-IR in PCOS patients. Further studies are required to elucidate these associations more clear.

Correlation between PPARγ protein expression level in granulosa cells and pregnancy rate in IVF program

BACKGROUND

Peroxisome proliferative-activated receptors (PPARs) are nuclear receptors that involved in cellular lipid metabolism and differentiation. The subtype γ of the PPAR family (PPARγ) plays important roles in physiologic functions of ovaries.

OBJECTIVE

To determine correlation between PPARγ protein level in granulosa cells and pregnancy rate in women undergoing in-vitro fertilization (IVF) treatment.

MATERIALS AND METHODS

In this cross-sectional study, twenty-five samples of granulosa cells were collected from women referred to an IVF treatment center. PPARγ protein expression level in granulosa cells was determined in comparison with β-actin level as control gene with Western blot test. Laboratory pregnancy was determined by a rise in blood β-hCG level fourteen days after embryo transfer. Correlation analyses were used to test for associations between the oocytes and pregnancy occurrence as outcome variables and PPARγ protein expression level.

RESULTS

Correlation analysis indicated that there was no significant relationship between granulosa cells PPARγ protein level with IVF parameters including number of matured oocytes and the ratio of fertilized to matured oocytes. Comparison of granulosa cells PPARγ protein level with positive and negative laboratory pregnancy revealed also no significant relationship.

CONCLUSION

According to the results of this study, PPARγ protein level in granulosa cells could not be directly correlated to the success rate of IVF.

PPAR Gamma: Coordinating Metabolic and Immune Contributions to Female Fertility

Peroxisome proliferator-activated receptor gamma (PPARG) regulates cellular functions such as adipogenesis and immune cell activation. However, new information has indicated additional roles of PPARG directing the cyclic changes that occur within ovarian tissue of female mammals, including those that facilitate the release of oocytes each estrous cycle. In addition to ovarian PPARG expression and function, many PPARG actions within adipocytes and macrophages have additional direct and indirect implications for ovarian function and female fertility. This encompasses the regulation of lipid uptake and transport, insulin sensitivity, glucose metabolism, and the regulation of inflammatory mediator synthesis and release. This review discusses the developing links between PPARG activity and female reproductive function, and highlights several mechanisms that may facilitate such a relationship.

Two common polymorphisms in the peroxisome proliferator-activated receptor γ gene may improve fertilization in IVF

Genetic factors play an important role in women's fertility and embryonic development and may also contribute to the efficacy of assisted reproduction techniques. The aim of this study was to investigate the effect of His447His and Pro12Ala peroxisome proliferator-activated receptor γ (PPARγ) gene polymorphisms on oocytes and fertilization in women undergoing IVF. Follicular fluid and blood samples were obtained from 98 IVF patients referred to Tabriz Alzahra Hospital. Samples were analysed for fatty acid content by gas-liquid chromatography and for polymorphisms of the PPARγ gene using polymerase chain reaction-restriction fragment length polymorphism-based methods. Multiple regression analyses were used to test the independence of associations between the number of mature and fertilized oocytes as outcome variables and the polymorphisms of PPARγ gene. For both polymorphisms, fertilization ratio was significantly (P<0.05) higher in carriers of the rare alleles than homozygous wild-type genotypes. The associations of His447His (P=0.003) and Pro12Ala (P=0.015) polymorphisms remained statistically significant in the multiple regression analyses. This study suggests that the two common gene polymorphisms of PPARγ may improve fertilization in vitro and, thus possibly, female fertility.

The role of genetic variation in peroxisome proliferator-activated receptors in the polycystic ovary syndrome (PCOS): an original case-control study followed by systematic review and meta-analysis of existing evidence

OBJECTIVE

To study the association of polymorphisms in the genes encoding peroxisome proliferator-activated receptors (PPARs) with the polycystic ovary syndrome (PCOS).

DESIGN

Case-control study and meta-analysis of published evidence.

PATIENTS

One hundred and sixty-one polycystic ovary syndrome patients and 113 non-hyperandrogenic women.

MEASUREMENTS

Genotyping for PPAR-gamma coactivator-1 gene (PPARGC1A) Gly482Ser, PPAR-alpha Leu162Val, PPAR-delta rs2267668A/G, PPAR-delta-87T/C, PPAR-gamma2 Pro12Ala and PPAR-gamma2 -681C/G variants and systematic review of the literature using the Entrez-PubMed search engine, followed by meta-analysis whenever possible.

RESULTS

Polycystic ovary syndrome patients carried the Gly482Ser variant in PPARGC1A more frequently than controls (72%vs. 58%, chi(2 )=( )5.54 P = 0.019), whereas carriers of the PPAR-alpha Leu162Val, PPAR-delta rs2267668A/G, PPAR-delta-87T/C, PPAR-gamma2 Pro12Ala and PPAR-gamma2 -681C/G variants were distributed similarly among both groups. The interaction between the PPARGC1A Gly482Ser and PPAR-delta-87T/C variants was also associated with PCOS (OR = 1.24, 95% CI 1.05-1.50, P = 0.008). The systematic review identified 31 studies addressing associations between PPARs variants and PCOS; meta-analysis was possible for nine studies focusing on the PPAR-gamma2 Pro12Ala variant. Although the individual studies did not reveal any statistically significant association, meta-analysis uncovered that carrying the PPAR-gamma2 Pro12Ala variant was associated with a reduced probability of having PCOS (OR = 0.77, 95% CI 0.61-0.96, P = 0.025), and that this association may be mediated by an effect on insulin sensitivity.

CONCLUSIONS

Common polymorphisms in the PPARGC1A, PPAR-delta and PPAR-gamma2 loci are associated with PCOS.

The Pro12Ala polymorphism of the PPAR-gamma gene is not associated with the polycystic ovary syndrome

OBJECTIVE

Insulin resistance is a key factor in the pathogenesis of polycystic ovary syndrome (PCOS). Peroxisome proliferator-activated- receptor-gamma (PPAR-gamma) has been implicated in insulin resistance and adiposity. The aim of the study was to investigate the possible involvement of the Pro12Ala polymorphism of the PPAR-gamma gene in the pathogenesis of PCOS.

DESIGN

We studied 180 women with PCOS and 140 healthy controls. Body mass index (BMI) was recorded. Blood samples were drawn after overnight fasting and serum glucose, insulin, lipid and hormonal profiles were determined. The fasting glucose/insulin ratio and HOMA index were calculated. Moreover, 100 women with PCOS underwent a 75g oral glucose tolerance test and the area under the curve for insulin and glucose was estimated. DNA was extracted from peripheral blood leucocytes and the Pro12Ala polymorphism was genotyped.

RESULTS

The PPAR-gamma genotypes were found to be in the Hardy-Weinberg equilibrium in both study groups. No difference was found in the distribution of the Pro12Ala polymorphism between PCOS and controls. Insulin resistance indices and lipid and hormonal profile were not different among the various genotypes of the Pro12Ala polymorphism.

CONCLUSIONS

The Pro12Ala polymorphism of the PPAR-gamma gene is not involved in the pathogenesis or the phenotypic expression of PCOS.

Pro12Ala and His447His polymorphisms of PPAR-gamma are associated with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common endocrine disorder that affects 4-12% of women of reproductive age, and is specified when two of the three following criteria are present: hyperandrogenism, oligomenorrhoea and polycystic ovary morphology by ultrasonography. PCOS is characterized by infertility, obesity and hyperinsulinaemia. However, the aetiology of PCOS has not yet been fully identified due to complex metabolic mechanisms. Many researchers have demonstrated that polymorphisms of putative genes related to symptoms are associated with PCOS. In the reproductive system, energy metabolism and hormonal regulation are important to differentiate granulosa cells in the ovary. Peroxisome proliferator-activated receptor gamma (PPAR-gamma) is a transcription factor, and is known to be associated with insulin sensitivity. Furthermore, it is highly expressed in granulosa cells. It was recently reported that various polymorphisms of PPAR-gamma are associated with PCOS in different ethnic backgrounds. This study has shown that both Pro12Ala and His447His polymorphisms of PPAR-gamma are associated with PCOS in a Korean population.

The role of genetic variation in the lamin a/c gene in the etiology of polycystic ovary syndrome

OBJECTIVE

We performed this study to test the hypothesis that variation in the lamin a/c gene (LMNA) contributes to milder phenotypes of insulin resistance, hyperandrogenism, and/or metabolic syndrome associated with polycystic ovary syndrome (PCOS).

RESEARCH DESIGN AND METHODS

We resequenced the coding region, flanking intronic, and proximal promoter regions of the lamin a/c gene in 43 women with PCOS with evidence of upper-body obesity (waist circumference >88 cm) and identified 56 variants, two of which were nonsynonymous substitutions (lmna11 exon1 E98D; lmna24 exon 7 R455C). We genotyped 53 single-nucleotide polymorphisms (44 identified through resequencing and nine included to maximize informativeness of the entire gene) in 624 index (PCOS) cases and 544 controls of European ancestry. We tested for association between these variants and PCOS. In a subset of individuals, we also tested for association with metabolic syndrome and quantitative traits (body mass index, waist circumference, total testosterone, dehydroepiandrosterone sulfate, fasting glucose and insulin, low-density lipoprotein, and total triglycerides).

RESULTS

After correction for multiple testing, none of the variants showed significant evidence for association with PCOS, the metabolic syndrome, or any of the quantitative traits tested.

CONCLUSIONS

Whereas these studies cannot exclude the role of genetic variation in the lamin a/c gene in isolated cases of PCOS, we can conclude that common variation in the lamin a/c gene does not contribute to the etiology of PCOS in women of European ancestry.

Genetic variations of solute carrier family 30 (zinc transporter) member 8 (SLC30A8) are not associated with polycystic ovary syndrome

No statistically significant differences in genotype and allele frequencies of single nucleotide polymorphism (SNP) rs13266634 in gene SLC30A8 were found between patients with polycystic ovary syndrome (PCOS) and healthy controls. No associations were observed between genotype of rs13266634 and the quantitative clinical features of PCOS patients in the PCOS group after adjustment for body mass index.

Functional genetic polymorphisms and female reproductive disorders: Part I: Polycystic ovary syndrome and ovarian response

BACKGROUND

The identification of polymorphisms associated with a disease can help to elucidate its pathogenesis, and this knowledge can be used to improve prognosis for women with a particular disorder, such as polycystic ovary syndrome (PCOS). Since an altered response to ovarian stimulation is also a characteristic of the disease, further knowledge about its aetiology could help in defining the parameters that determine the response of an individual to ovarian stimulation.

METHODS

PubMed and EMBASE databases were systematically searched for gene association studies published until the end of August 2007, using search criteria relevant to PCOS and ovarian response to stimulation. Data from additional papers identified through hand searches were also included; 139 publications were reviewed.

RESULTS

Several genes involved in ovarian function and metabolism are associated with increased susceptibility to PCOS, but none is strong enough to correlate alone with susceptibility to the disease, or response to therapy. A single-nucleotide polymorphism in exon 10 of the FSH receptor (FSHR) gene, FSHR p.N680S, was consistently identified as having a significant association with ovarian response to FSH.

CONCLUSIONS

No consistent association between gene polymorphism and PCOS could be identified. The FSHR gene may play a significant role in the success of ovarian stimulation, and can be used as a marker to predict differences in FSHR function and ovarian response to FSH. Genotyping the FSHR p.N680S polymorphism may provide a means of identifying a population of poor responders before in vitro fertilization procedures are initiated.

Single gene contributions: genetic variants of peroxisome proliferator-activated receptor (isoforms alpha, beta/delta and gamma) and mechanisms of dyslipidemias

PURPOSE OF REVIEW

Polymorphisms in peroxisome proliferator-activated receptor isoforms may be among the most important single-gene contributors to dyslipidemias, insulin resistance, and maturity-onset diabetes.

RECENT FINDINGS

Familial partial lipodystrophy is a rare but characteristic phenotype associated with carriers of peroxisome proliferator-activated receptor-gamma missense mutations. Mutant receptors are transcriptionally defective, exhibit aberrant affinity for co-regulator molecules, and can exert dominant-negative or haplo-insufficiency effects on normal peroxisome proliferator-activated receptor-gamma function. The P12A variant of isoform gamma is estimated to reduce diabetes risk by 19% in many populations, and has a large attributable risk because of high prevalence of the normal allele. Variants L162V and V227A of isoform alpha (common in white and Oriental populations, respectively) are associated with sexually dimorphic perturbations of lipid metabolism and cardiovascular risk. Polymorphisms in isoforms alpha and beta/delta are reported to influence lipid and glucose utilization. Apart from lipodystrophic syndromes, metabolic and cardiovascular risk in peroxisome proliferator-activated receptor variants is apparently modulated by dietary and exercise interventions, and interactions with polymorphisms in other genetic loci.

SUMMARY

Polymorphisms in peroxisome proliferator-activated receptors are critical susceptibility risk factors for dyslipidemias and diabetes. They provide attractive targets for gene-environment interventions to reduce the burden of metabolic disease.

Association study between single nucleotide polymorphisms in the VEGF gene and polycystic ovary syndrome

OBJECTIVE

To investigate single nucleotide polymorphisms (SNPs) in vascular endothelial growth factor (VEGF) gene that have significant associations with the pathogenesis of polycystic ovary syndrome (PCOS) in a Korean population.

DESIGN

Case-control study.

SETTING

University-based hospital.

PATIENT(S)

One hundred thirty-four patients with PCOS and 100 healthy women as controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Frequencies of genotypes for SNPs in VEGF gene, which were specifically expressed in a Korean population.

RESULT(S)

After genotypic analysis, we found that among 10 SNPs, one novel SNP at site +9812 and one known SNP at site +13553 have P values lower than .05 (+9812: odds ratio [95% confidence interval] 0.61 [0.39-0.95]; +13553: odds ratio [95% confidence interval] 0.59 [0.37-0.93]) and one haplotype (ht4) also has a P value in the significant range (odds ratio [95% confidence interval] 0.34 [0.16-0.74]).

CONCLUSION(S)

We concluded that one novel SNP at +9812 site, one known SNP at +13553 site, and one selected haplotype in the VEGF gene have a high possibility of significant associations with the pathogenesis of PCOS in a Korean population.

The role of the Pro12Ala polymorphism in peroxisome proliferator-activated receptor gamma in diabetes risk

PURPOSE OF REVIEW

To provide a timely update of the literature regarding the role of the Pro12Ala polymorphism of the peroxisome proliferator-activated receptor gamma gene in type 2 diabetes and related phenotypes.

RECENT FINDINGS

The adipocyte-specific gamma2 isoform of peroxisome proliferator-activated receptor gamma is now considered to be one of the best-replicated genetic risk factors of common type 2 diabetes. The effect is relatively weak (pooled odds ratio is about 1.2) but because of the high prevalence and population-attributable risk, this polymorphism becomes relevant for assessing genetic susceptibility for type 2 diabetes. Less clear is the association with prediabetes subphenotypes where effects were only detectable in selected subgroups. Furthermore this review gives an overview about possible mechanisms of peroxisome proliferator-activated receptor gamma effects, gene-environment interactions, relevance to the therapeutic response to thiazolidinediones and further clinical observations.

SUMMARY

In conclusion, the Pro12 allele of peroxisome proliferator-activated receptor gamma is a robust diabetes-risk allele, as confirmed by many replications. There are many more clinical observations related to the Pro12Ala genotype which could be interesting and these clearly need to be analyzed in future studies.