Genetic variants in TCF7L2 and KCNJ11 genes in a Greek population with polycystic ovary syndrome

The expression profile of WNT/β-catanin signalling genes in human oocytes obtained from polycystic ovarian syndrome (PCOS) patients

Polycystic ovarian syndrome (PCOS) is a chronic hormonal turmoil that is demonstrated in 2.2-27% of women of pre-menopausal age. This disease is a complex multigenic disorder that results from the interaction between excess androgen expression, genetic susceptibility and environmental influences. PCOS is associated with 40% of female infertility and endometrial cancer. The WNT/β-catenin signalling transduction pathway regulates aspects of cell proliferation, migration and cell fate determination in the tissue along with early embryonic development and controls the proper activation of the female reproductive system, along with regulating hormonal activity in ovarian granulosa cells. In the current study, we investigated the expression profiles of WNT/β-catenin signalling pathway genes (AXIN2, FZD4, TCF4, WNT3, WNT4, WNT5A, WNT7A, WNT1, APC, GSK3B and β-catenin) in a total of 13 oocyte samples. Seven of these samples were from polycystic women and six were from healthy women. The results of this study displayed the absence of expression of AXIN2, FZD4, TCF4, WNT5A, WNT3, WNT4 and WNT7A genes in ovaries from women with PCOS and from healthy women. While APC and β-catenin expression levels were similar in the oocytes of both patients and controls, conversely, WNT1 and GSK3β genes both showed elevated expression in the oocytes of patients with PCOS, therefore suggesting an association between aberrant expression of WNT1 and GSK3β and the pathogenesis of PCOS. The observations of the current study could be helpful to provide evidence regarding the pathogenesis of PCOS and its treatment.

Interaction between TCF7L2 rs7903146 Genotype, HbA1c Levels, and the Periodontal Status of Dental Patients

OBJECTIVE

 The aim of the study was to investigate the potential interaction between TCF7L2 rs7903146 genotype, which is implicated for type-2 diabetes mellitus genetic susceptibility, HbA1c levels, and the periodontal status of dental patients.

MATERIALS AND METHODS

HbA1c levels, clinical periodontal parameters (probing depth, clinical attachment level, bleeding on probing, and plaque index), and several parameters (such as body mass index [BMI], smoking habits, education level, and age) were recorded in 150 patients who fulfilled the criteria for screening for prediabetes/diabetes of the Centers for Disease Control and Prevention. DNA was extracted and the TCF7L2 single nucleotide polymorphism (SNP) rs7903146 was genotyped in all participants.

RESULTS

 Thirty-one patients out of 150 tested were found with unknown hyperglycemia (20.7%). Regarding sex, education, parent with diabetes, normal BMI, smoking, age ≥45 years and prior testing for diabetes, no differences were observed between patients displaying HbA1c < 5.7 and ≥ 5.7% (Pearson's Chi-square test, p > 0.05). Regarding periodontal parameters and differences between subgroups (HbA1c levels ≥ 5.7 and HbA1c levels < 5.7), statistically significant differences were observed for probing depth (3.20 ± 0.94 vs. 2.81 ± 0.78 mm), clinical attachment level (3.54 ± 1.20 vs. 3.18 ± 1.06 mm) and bleeding on probing (0.62 ± 0.25 vs. 0.50 ± 0.24%) with hyperglycemic patients exhibiting worse periodontal conditions (Mann-Whitney test p < 0.05). The allelic and genotype frequencies for the transcription factor 7-like 2 (TCF7L2) gene, SNPs 7903146 did not exhibit a significant difference between the HbA1c > 5.7 and HbA1c < 5.7 groups and the periodontitis and nonperiodontitis subgroups respectively (Fisher's exact test >0.05). Statistical Analysis Patient characteristics and their association with prediabetes were tested by Pearson's Chi-square test (asymptotic, two sided). Differences of periodontal parameters between subgroups were tested with the Mann-Whitney U-test. The associations of allele and genotype frequencies in the patient and control groups were analyzed using the Fisher's exact test of independence.The significance level was set at the 0.05 for all tests.

CONCLUSION

 A statistically significant association between TCF7L2 rs7903146 genotype and periodontal condition or HbA1c levels was not observed in contrast to statistically significant differences of clinical parameters of periodontitis in patients with hyperglycemia.

Resistance to the Insulin and Elevated Level of Androgen: A Major Cause of Polycystic Ovary Syndrome

PCOS has a wide range of negative impacts on women's health and is one of the most frequent reproductive systemic endocrine disorders. PCOS has complex characteristics and symptom heterogeneity due to the several pathways that are involved in the infection and the absence of a comm14on cause. A recent study has shown that the main etiology and endocrine aspects of PCOS are the increased level of androgen, which is also known as "hyperandrogenemia (HA)" and secondly the "insulin resistance (IR)". The major underlying cause of the polycystic ovary is these two IR and HA, by initiating the disease and its severity or duration. As a consequence, study on Pathogenesis is crucial to understand the effect of "HA" and "IR" on the pathophysiology of numerous symptoms linked to PCOS. A deep understanding of the pattern of the growth in PCOS for HA and IR can help ameliorate the condition, along with adjustments in nutrition and life, as well as the discovery of new medicinal products. However, further research is required to clarify the mutual role of IR and HA on PCOS development.

Genetic construction between polycystic ovarian syndrome and type 2 diabetes

Polycystic ovarian syndrome (PCOS) in reproductive-aged women is identified to be one of the endocrine disorders. This heterogeneous disorder is categorized through oligo-anovulation and hyperandrogenemia. National institutes of health and Rotterdam criterions were used to diagnose PCOS women. Type 2 Diabetes (T2D) is one of the complications in PCOS which is connected through insulin resistance (IR), which is a condition in which liver, muscles and fat infrequently respond to the hormones, and this leads to extreme IR and consequently leads to T2D disease. PCOS is inherited by the autosomal dominant mode of inheritance and may also with the different intricate patterns. Till now, many studies have been performed in PCOS with the genes identified by T2D and till now no studies have shown the similar genetic association and pathophysiology between both the diseases. So, the current review aims to investigate the genetic relation between PCOS and T2D and why both the diseases cannot be reverted. In this review, published data were screened with the T2D related genes and single nucleotide polymorphisms in PCOS women. The case-control, hospital-based and meta-analysis molecular studies disclosed both positive and negative connotations. Genetically, no relationship has been established between PCOS and T2D. Maximum studies have shown as PCOS women had developed T2D later in life because as a risk-factor, but none of the studies documented T2D women having developed PCOS as a risk factor. Apart from this, the disease PCOS is developed in women with reproductive age and T2D develops in both the men and women during adulthood. This review concludes as there is a genetic relation only in between PCOS and T2D, but not with T2D to PCOS and further it cannot be explicitly reverted from T2D to PCOS.

Screening of Polymorphisms of Transcription Factor 7-like 2 Gene in Polycystic Ovary Syndrome using Polymerase Chain Reaction-restriction Fragment Length Polymorphism Analysis

Background:

Polycystic ovary syndrome (PCOS) is a common endocrine disorder occurring in premenopausal women, with a prevalence rate of 5%–7%. It has been observed in multiple number of studies the coexistence between diabetes mellitus 2 and obesity with this endocrinopathic disorder. Transcription factor 7-like 2 (TCF7L2) gene is shown to be associated with insulin secretion.

Aim:

To screen whether the gene variant of TCF7L2 (formerly TCF4) gene is significantly associated and has susceptibilities with type 2 diabetes in PCOS. This study is essential to uncover diabetogenic association of the TCF7L2 gene variants with PCOS.

Design:

This was a hospital-based study.

Methods:

In this work, blood samples from 43 PCOS patients with age and sex similar to 43 control samples were collected, followed by isolation of DNA. Further genotyping of the TCF7L2 gene was carried out by performing polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

Statistical Analysis:

Genotype frequencies of the TCF7L2 rs7903146 gene were checked by Hardy–Weinberg equilibrium of genotype in both PCOS and the control group, and also, the frequencies of the genotype were performed accordingly.

Results:

There was no significant allelic variation observed among the patient and the control samples. From the patient details, it was observed that women between the age group of 21 and 25 years are susceptible to PCOS.

Conclusion:

From the PCR-RFLP analysis, it can be stated that there are no expected gene polymorphisms seen in this study, unlike the study carried out on the Chinese population where they observed genotype variations CC, CT, and TT. From this study, we can conclude that TCF7L2 rs7903146 gene cannot be considered as the candidate gene for the occurrence of PCOS.

Genetic determinants of polycystic ovary syndrome: progress and future directions

The field of the genetics of polycystic ovary syndrome (PCOS) has relatively recently moved into the era of genome-wide association studies. This has led to the discovery of 16 robust loci for PCOS. Some loci contain genes with clear roles in reproductive (LHCGR, FSHR, and FSHB) and metabolic (INSR and HMGA2) dysfunction in the syndrome. The next challenge facing the field is the identification of causal variants and genes and the role they play in PCOS pathophysiology. The potential for gene discovery to improve diagnosis and treatment of PCOS is promising, though there is much to be done in the field before the current findings can be translated to the clinic.

FADS1-FADS2 gene cluster confers risk to polycystic ovary syndrome

Dyslipidemia is common in polycystic ovary syndrome (PCOS). This study was aimed to investigate whether fatty acid desaturase genes (FADS), a dyslipidemia-related gene cluster, are associated with PCOS. We scanned variations of FADS genes using our previous data of genome-wide association study (GWAS) for PCOS and selected rs174570 for further study. The case-control study was conducted in an independent cohort of 1918 PCOS cases and 1889 age-matched controls and family-based study was conducted in a set of 243 core family trios with PCOS probands. Minor allele frequency (allele T) of rs174570 was significantly lower in PCOS cases than that in age-matched controls (P = 2.17E-03, OR = 0.85), even after adjustment of BMI and age. PCOS subjects carrying CC genotype had higher testosterone level and similar lipid/glucose level compared with those carrying TT or TC genotype. In trios, transmission disequilibrium test (TDT) analysis revealed risk allele C of rs174570 was significantly over-transmitted (P = 2.00E-04). Decreased expression of FADS2 was detected in PCOS cases and expression quantitative trait loci (eQTL) analysis revealed the risk allele C dosage was correlated with the decline of FADS2 expression (P = 0.002). Our results demonstrate that FADS1-FADS2 are susceptibility genes for PCOS.

Is the association between insulin resistance and diabetogenic haematopoietically expressed homeobox (HHEX) polymorphism (rs1111875) affected by polycystic ovary syndrome status?

Polycystic ovary syndrome (PCOS) is frequently accompanied by insulin resistance (IR). The aim of the present study was to investigate whether the genetic association between insulin resistance and two single nucleotide polymorphisms (SNPs), namely rs7903146 (C/T) in transcription factor 7-like 2 (TCF7L2) and rs1111875 (A/G) in haematopoietically expressed homeobox (HHEX), is affected by PCOS status in Iranian women. The study participants consisted of 582 women with PCOS (cases) referred to the Reproductive Endocrinology Research Center and 504 subjects without PCOS (controls), randomly selected from the Tehran Lipid and Glucose Study. Cases and controls were further subdivided to two groups according to IR status: those with and without IR. IR was identified on the basis of homeostasis model assessment of insulin resistance (HOMA-IR) ≥2.63. The SNPs in TCF7L2 and HHEX were genotyped by polymerase chain reaction-restriction fragment length polymorphism. There were no significant differences in the distribution of genotypes and alleles between cases and controls (P<0.05). Among cases, the prevalence of the CC, CT and TT genotypes was 37.8%, 46.3% and 15.9%, respectively, whereas the prevalence of the AA, AG and GG genotypes was 13.5%, 46.1% and 40.4%, respectively. In the control group, the prevalence of the CC, CT and TT genotypes was 32.2%, 53.9% and 13.9%, respectively, whereas the prevalence of the AA, AG and GG genotypes was 11.3%, 48.6% and 40.0%, respectively. After adjustment for age and body mass index, the probability of IR was decreased by 49% among carriers of the A allele in the control group (95% confidence interval 0.33-0.78; P=0.002). The findings of the present study suggest that the association between IR and diabetogenic polymorphisms may be affected by PCOS status.

Association between rs7903146 and rs12255372 polymorphisms of transcription factor 7-like 2 gene and polycystic ovary syndrome: a systematic review and meta-analysis

The present systematic review and meta-analysis of case-control studies examines the associations between rs7903146 and rs12255372 polymorphisms of the TCF7L2 gene and PCOS. A search of the literature published until August 2014 was carried out in PubMed, Cochrane Central Register of Controlled Trials, EMBASE, and LILACS. There were no other limits except for the end date. We included observational studies with women of any age diagnosed with PCOS and healthy controls that analyzed polymorphisms rs7903146 and rs12255372. We included case-control or cross-sectional studies analyzing polymorphism rs7903146 or rs12255372 in women with PCOS and healthy controls. Eighteen studies were identified after the primary literature search and seven articles were included in the meta-analysis. All employed Rotterdam criteria for the diagnosis of PCOS. The genotypic distributions in the control groups were in agreement with Hardy-Weinberg equilibrium in all studies. The pooled population included Asian descendents (Chinese, Korean), Caucasians from southern Brazil, Tunisian, and European populations (British/Irish, Northern Finns, Greeks, Czechs), including 1,892 women with PCOS and 2,695 controls. There were no significant associations between PCOS and TCF7L2 rs7903146 or rs12255372 polymorphisms, irrespective of whether allele contrast, additive, dominant, or recessive models of inheritance were used. Furthermore, no significant associations were found after stratification for ethnicity (Asian or non-Asian). There was no significant heterogeneity between studies and no publication bias. The present results suggest that rs7903146 T allele or rs12255372 is not associated with risk for PCOS in non-Asian or Asian women. This systematic review and meta-analysis are registered in PROSPERO under number CRD42013005930.

KCNJ11: Genetic Polymorphisms and Risk of Diabetes Mellitus

Diabetes mellitus (DM) is a major worldwide health problem and its prevalence has been rapidly increasing in the last century. It is caused by defects in insulin secretion or insulin action or both, leading to hyperglycemia. Of the various types of DM, type 2 occurs most frequently. Multiple genes and their interactions are involved in the insulin secretion pathway. Insulin secretion is mediated through the ATP-sensitive potassium (KATP) channel in pancreatic beta cells. This channel is a heteromeric protein, composed of four inward-rectifier potassium ion channel (Kir6.2) tetramers, which form the pore of the KATP channel, as well as sulfonylurea receptor 1 subunits surrounding the pore. Kir6.2 is encoded by the potassium inwardly rectifying channel, subfamily J, member 11 (KCNJ11) gene, a member of the potassium channel genes. Numerous studies have reported the involvement of single nucleotide polymorphisms of the KCNJ11 gene and their interactions in the susceptibility to DM. This review discusses the current evidence for the contribution of common KCNJ11 genetic variants to the development of DM. Future studies should concentrate on understanding the exact role played by these risk variants in the development of DM.

Relationships between TCF7L2 genetic polymorphisms and polycystic ovary syndrome risk: a meta-analysis

OBJECTIVE

This meta-analysis was performed to evaluate the relationships between genetic polymorphisms in the TCF7L2 gene and polycystic ovary syndrome (PCOS) risk.

METHODS

The PubMed, Centralised Information Service for Complementary Medicine (CISCOM), Cumulative Index to Nursing and Allied Health Literature (CINAHL), Web of Science, Google Scholar, EBSCO, Cochrane Library, and Common Biorepository Model (CBM) databases were searched for relevant articles published before November 1st, 2013, without language restrictions. Meta-analysis was conducted using the STATA 12.0 software. The relationships were evaluated by calculating the pooled odds ratios (ORs) and their 95% confidence intervals (CIs). Seven case-control studies with a total 2458 PCOS patients and 5109 healthy subjects' met our inclusion criteria for qualitative data analysis. Two common polymorphisms (rs7903146 C→T and rs12255372 G→T) in the TCF7L2 gene were assessed.

RESULTS

The results of our meta-analysis suggested that TCF7L2 genetic polymorphisms might be strongly correlated with an increased risk of PCOS (allele model, OR=1.33, 95% CI=1.15-1.54, P<0.001; dominant model, OR=1.40, 95% CI=1.12-1.75, P=0.003), especially for the rs7903146 C→T polymorphism. A subgroup analysis was done to investigate the effect of ethnicity on an individual's risk of PCOS. Our results revealed positive significant correlations between TCF7L2 genetic polymorphisms and an increased risk of PCOS among Caucasians (allele model, OR=1.26, 95% CI=1.08-1.47, P=0.004; dominant model, OR=1.33, 95% CI=1.00-1.76, P=0.046) and Asians (allele model, OR=2.02, 95% CI=1.42-2.89, P<0.001; dominant model, OR=2.02, 95% CI=1.40-2.92, P<0.001), but not among Africans (all P<0.05).

CONCLUSIONS

Our findings provide convincing evidence that TCF7L2 genetic polymorphisms may contribute to susceptibility to PCOS, especially for the rs7903146 C→T polymorphism among Caucasians and Asians.

The Genetics of Infertility: Current Status of the Field

Infertility is a relatively common health condition, affecting nearly 7% of all couples. Clinically, it is a highly heterogeneous pathology with a complex etiology that includes environmental and genetic factors. It has been estimated that nearly 50% of infertility cases are due to genetic defects. Hundreds of studies with animal knockout models convincingly showed infertility to be caused by gene defects, single or multiple. However, despite enormous efforts, progress in translating basic research findings into clinical studies has been challenging. The genetic causes remain unexplained for the vast majority of male or female infertility patients. A particular difficulty is the huge number of candidate genes to be studied; there are more than 2,300 genes expressed in the testis alone, and hundreds of those genes influence reproductive function in humans and could contribute to male infertility. At present, there are only a handful of genes or genetic defects that have been shown to cause, or to be strongly associated with, primary infertility. Yet, with completion of the human genome and progress in personalized medicine, the situation is rapidly changing. Indeed, there are 10-15 new gene tests, on average, being added to the clinical genetic testing list annually.

Polymorphisms of transcription factor-7-like 2 (TCF7L2) gene in Tunisian women with polycystic ovary syndrome (PCOS)

BACKGROUND AND AIMS

Polycystic ovary syndrome (PCOS) is a common endocrine disorder that affects women in their child-bearing age, and is often associated with insulin resistance and type 2 diabetes (T2DM). Given the overlap between PCOS and T2DM, we investigated the association of transcription factor-7-like 2 (TCF7L2) variants rs4506565, rs7903146, rs12243326, and rs12255372 with the susceptibility to PCOS.

SUBJECTS AND METHODS

Study subjects comprised 119 Tunisian women with PCOS (mean age 29.8±4.7years), and 150 control women (mean age 30.6±5.9years). TCF7L2 genotyping was done by the allelic discrimination/real-time PCR method.

RESULTS

Minor allele frequencies (MAFs) of rs4506565 (P=0.61), rs7903146 (P=0.68), rs12243326 (P=0.56), and rs12255372 (P=0.60) were comparable between PCOS cases and control subjects. As the four tested TCF7L2 variants were in linkage disequilibrium, 4-locus (rs4506565, rs7903146, rs12243326, rs12255372) haplotype analysis demonstrated that haplotype 2111 was initially negatively associated with PCOS [P=0.035; OR (95% CI)=0.13 (0.02-0.85)], which was later lost upon correcting for multiple comparisons [Pc=0.248].

CONCLUSION

Our data suggest that there is weak or no contribution of TCF7L2 gene polymorphism to PCOS in Tunisian women. Further studies with larger samples are necessary to confirm this observation.

PON1-108 TT and PON1-192 RR genotypes are more frequently encountered in Greek PCOS than non-PCOS women, and are associated with hyperandrogenaemia

OBJECTIVE

To investigate the frequencies of three paraoxonase (PON)1 polymorphisms in Greek polycystic ovary syndrome (PCOS) and non-PCOS women, and their genotypes association with hyperandrogenaemia and insulin resistance.

DESIGN

Case-control genetic association study.

SETTING

University Hospital Endocrine Unit.

PATIENTS

A total of 142 PCOS cases (NIH criteria) and 112 controls.

MAIN OUTCOME MEASURE

Genotyping of the c.-108C>T (PON1-108), the c.163T>A (PON1-55) and the c.575A>G (PON1-192) polymorphisms and measurement of baseline androgen and insulin resistance profile.

RESULTS

The PON1-108 TT and PON1-192 RR genotypes were more frequently encountered in the PCOS than in the control group. The PON1-192 R allele frequency was greater in the PCOS than in the control group. Comparing the PCOS and the control groups, statistical significances favoured a recessive and a dominant genetic model, respectively, for the single PON1-108 T and PON1-192 R alleles. Free Androgen Index (FAI) levels were higher in patients with PON1-108 TT, whereas Testosterone, FAI and Dehydroepiandrosterone sulphate (DHEAS) levels were higher in patients with PON1-192 RR than patients with the wild or the heterozygous genotype.

CONCLUSIONS

The decreased PON1 activity-associated PON1-108 TT and the PON1-192 RR genotypes are more frequently found in Greek PCOS women and are associated with hyperandrogenaemia. Hyperandrogenaemia must depend also on other genetic factors because the same genotypes were not associated with hyperandrogenaemia in the control group. Through identification of the involved polymorphisms, women with PCOS could potentially have a better therapeutic screening.

Genetics of the polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a highly complex endocrine disorder, characterized by hyperandrogenemia, menstrual irregularities and polycystic ovaries. A strong genetic component to the etiology of PCOS is evident. However, due to the genetic and phenotypic heterogeneity of PCOS and the lack of insufficiently large cohorts, studies to identify specific contributing genes to date have yielded only few conclusive results. In this review we discuss the current status of the genetic analysis of PCOS including the results of numerous association studies with candidate genes involved in TGF-β and insulin signaling, type 2 diabetes mellitus and obesity susceptibility. Furthermore, we address current challenges in genetic studies of PCOS, and the promise of new approaches, including genome-wide association studies and next-generation sequencing.

Polycystic ovary syndrome is not associated with genetic variants that mark risk of type 2 diabetes

Polycystic ovary syndrome (PCOS) is a disorder of irregular menses, hyperandrogenism and/or polycystic ovary morphology. A large proportion of women with PCOS also exhibit insulin resistance, β-cell dysfunction, impaired glucose tolerance and/or type 2 diabetes (T2D). We therefore hypothesized that genetic variants that predispose to risk of T2D also result in risk of PCOS. Variants robustly associated with T2D in candidate gene or genome-wide association studies (GWAS; n = 56 SNPs from 33 loci) were genotyped in women of European ancestry with PCOS (n = 525) and controls (n = 472), aged 18-45 years. Metabolic, reproductive and anthropomorphic data were examined as a function of the T2D variants. All genetic association analyses were adjusted for age, BMI and ancestry and were reported after correction for multiple testing. There was a nominal association between variants in KCNJ11 and risk of PCOS. However, a risk score of 33 independent T2D-associated variants from GWAS was not significantly associated with PCOS. T2D variants were associated with PCOS phenotype parameters including those in THADA and WFS1 with testosterone levels, ENPP/PC1 with triglyceride levels, FTO with glucose levels and KCNJ11 with FSH levels. Diabetes risk variants are not important risk variants for PCOS.

Polycystic ovary syndrome is not associated with polymorphisms of the TCF7L2, CDKAL1, HHEX, KCNJ11, FTO and SLC30A8 genes

OBJECTIVE

Insulin resistance is a core feature of polycystic ovary syndrome (PCOS). Recently, genome-wide association studies have reported a number of single-nucleotide polymorphisms (SNPs) with reproducible associations and susceptibilities to type 2 diabetes. We examined the potential association between the diabetogenic genes uncovered in the genome-wide association studies and PCOS in Korean women.

DESIGN

Case-control study.

PATIENTS

Women with or without PCOS.

MEASUREMENTS

DNA samples from 377 patients with PCOS and 386 age-matched controls were genotyped.

RESULTS

None of the 12 SNPs in the six genes (KCNJ11, TCF7L2, SLC30A8, HHEX, FTO and CDKAL1) uncovered in the genome-wide association studies were associated with PCOS. For further analysis, the patients with PCOS were divided into two or three subgroups according to genotype, and the associations between the genotypes and insulin resistance or insulin secretory capacity were assessed. No SNPs were significantly associated with HOMA-IR, HOMA (βcell) (%), or 2-h 75-g oral glucose tolerance test insulin levels in the patients with PCOS; there were no significant associations with other serum hormonal and metabolic markers, such as androgen or glucose levels.

CONCLUSIONS

Our results suggest that the six type 2 diabetes-associated genes identified in genome-wide association studies are not associated with PCOS.

Common variants of transcription factor 7-like 2 (TCF7L2) are associated with reduced insulin secretion in women with polycystic ovary syndrome

Common variants of the transcription factor 7-like 2 (TCF7L2) gene were identified as one of the few genetic polymorphisms with powerful effects on the risk of type 2 diabetes (T2D). Given the genetic overlap between polycystic ovary syndrome (PCOS) and T2D, the present study was undertaken to investigate whether the TCF7L2 variants are also associated with PCOS. We analyzed single nucleotide polymorphisms (SNPs) rs11196218 and rs290487 of the TCF7L2 gene, which showed robust associations with T2D in Chinese population, in 430 PCOS patients and 360 control subjects by pyrosequencing, and also assessed the effect of genotype on clinical and biochemical traits in the PCOS group. We found no evidence for association between SNP rs11196218 and PCOS. The SNP rs290487 showed marginal differences in genotype frequencies between the PCOS and control group, with the minor C allele being the at-risk allele for PCOS. In PCOS women, the C allele carriers of rs290487 had higher levels of 2h blood glucose but lower insulinogenic index than noncarriers, suggesting impaired insulin secretion. Our data suggested that the TCF7L2 variants may confer an increased risk for early impairment of glucose homeostasis in PCOS.

Metabolic and cardiovascular genes in polycystic ovary syndrome: a candidate-wide association study (CWAS)

The role of metabolic disturbance in polycystic ovary syndrome (PCOS) has been well established, with insulin resistance and the resulting compensatory hyperinsulinemia thought to promote hyperandrogenemia. Genome-wide association studies (GWAS) have established a large number of loci for metabolic conditions such as type 2 diabetes and obesity. A subset of these loci has been investigated for a role in PCOS; these studies generally have not revealed a confirmed role for these loci in PCOS risk. However, a large scale investigation of genes related to these pathways has not previously been performed. We conducted a two stage case control association study of 121,715 single nucleotide polymorphisms (SNPs) selected to represent susceptibility loci associated with traits such as type 2 diabetes, obesity measures, lipid levels and cardiovascular function using the Cardio-Metabochip in 847 PCOS cases and 845 controls. Several hypothesis-generating associations with PCOS were observed (top SNP rs2129107, P=3.8×10(-6)). We did not find any loci definitively associated with PCOS after strict correction for multiple testing, suggesting that cardio-metabolic loci are not major risk factors underlying the susceptibility to PCOS.

The link between polycystic ovary syndrome and both Type 1 and Type 2 diabetes mellitus: what do we know today?

Polycystic ovary syndrome (PCOS) and Type 2 diabetes mellitus (T2D) are both obesity-related conditions that share epidemiological and pathophysiological factors. Insulin resistance is a key factor whereby obesity influences the expression of each condition. However, the mechanisms by which insulin resistance contributes towards the manifestation of PCOS and T2D differ in important ways: in PCOS, compensatory hyperinsulinemia results in pleiotropic effects including co-gonadotrophic stimulation of ovarian and adrenal steroidogenesis; in T2D, insulin resistance contributes towards β-cell exhaustion and ultimately to hyposecretion of insulin with resultant dysglycemia. The link between PCOS and Type 1 diabetes mellitus is believed to implicate supraphysiological concentrations of insulin within the systemic circulation. Further progression of the obesity epidemic will ensure even greater prominence of important obesity-related conditions such as PCOS and T2D. Research to gain a clearer understanding of the mechanisms linking each condition should be a priority.

Worldwide distribution of type II diabetes-associated TCF7L2 SNPs: evidence for stratification in Europe

Type II diabetes is a multifactorial disease with a complex etiology. Numerous genes have been implicated in disease pathogenesis. In particular, SNPs at the TCF7L2 locus have consistently shown strong associations with type II diabetes. This study characterizes the global distribution of type II diabetes-associated TCF7L2 SNPs utilizing HapMap, HGDP-CEPH, and Alfred databases and the literature. High frequencies of rs7903146(T), rs12255372(T), and rs7901695(C) SNPs are observed in Africa, Europe, and the Middle East, but they are reduced and almost absent in Southeast Asian and Native American populations. In contrast, rs11196218(A) has the highest frequency in Eurasia but is reduced in sub-Saharan African and Native American populations. Regional variations in rs7903146(T) follow a gradient of decreasing frequency from southern into northeastern Europe. These findings demonstrate extensive global and regional variations in the frequencies of TCF7L2 SNPs, which may contribute to differences in the incidence of type II diabetes worldwide.

Contemporary genetic technologies and female reproduction

BACKGROUND

The Fifth Evian Annual Reproduction (EVAR) Workshop Meeting discussed knowledge regarding contemporary genetics in female reproduction.

METHODS

Specialist reproductive medicine clinicians and geneticists delivered presentations based on published literature and current research. The content of this report is based on the expert presentations and subsequent group discussions that took place during this Workshop.

RESULTS

Numerous ovarian genes with a role in infertility have been identified. Future challenges for genetic screening of patients, such as those with polycystic ovary syndrome, primary ovarian insufficiency or endometriosis, include the identification of high-throughput strategies and how to apply these findings to infertile patients. The identification of high-quality embryos in IVF using objective technologies remains a high priority in order to facilitate single-embryo transfer. Gene expression profiling of cumulus cells surrounding the oocyte, and proteomic and metabolomic approaches in embryo culture media may significantly improve non-invasive embryo quality assessment.

CONCLUSIONS

The way forward in advancing the knowledge of genes involved in reproduction was considered to be through genome-wide association studies involving large numbers of patients. Establishing international collaboration is required to enable the application of such technologies in sufficient numbers of patients.

Polymorphisms of the HSD17B6 and HSD17B5 genes in Chinese women with polycystic ovary syndrome

OBJECTIVES

To investigate the polymorphisms of the 17β-hydroxysteroid dehydrogenase type 5 and type 6 (HSD17B5 and HSD17B6) genes in Chinese women with polycystic ovary syndrome (PCOS).

METHODS

Two hundred twenty-two PCOS patients and 283 controls were studied. Menarche age was recorded. Body mass indices (BMI) were calculated. Blood samples were obtained for single nucleotide polymorphism (SNP) analyses and hormone measurements. Genotyping of HSD17B6 and HSD17B5 in cases and controls was performed by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

The SNP rs898611 of the HSD17B6 gene (TT, CT, CC) in women with PCOS (0.680, 0.270, 0.050, respectively) did not differ from those in controls (0.700, 0.258, 0.042, respectively), and the SNP rs3763676 of the HSD17B5 gene (AA, AG, GG) was rare in Chinese women. Total testosterone and other reproductive hormones, such as follicle-stimulating hormone (FSH), luteinizing hormone (LH), LH/FSH, and estradiol (E(2)), were also similar among the different genotypes of the HSD17B6 in the PCOS subjects and the controls, whereas BMI was different in the three genotypes of the HSD17B6 in PCOS subjects.

CONCLUSIONS

Our data suggest that there is no association of HSD17B6 and HSD17B5 variants with the occurrence of PCOS in the Chinese population, but the polymorphism of SNP rs898611 is associated with BMI in PCOS patients.

Genetic basis of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is associated with obesity and manifests with reproductive, hyperandrogenic and metabolic features. Although the etiology of PCOS is complex and incompletely understood, genetics plays an important role (heritability: ∼70%). Potential problems with studying the genetics of PCOS include the heterogeneity of the condition and associated sub-fertility. A candidate gene approach has been used in over 70 published studies on PCOS, most of which have been inadequately powered to detect a statistically meaningful association. Furthermore, these studies often fail to replicate prior published studies on the same candidate gene in different populations. The first genome-sequence variant (identified from a genome-wide association study in subjects with Type 2 diabetes mellitus) to be studied in PCOS (FTO gene) has been shown by our group to associate with susceptibility for the development of PCOS. This is the first genetic corroboration of a link between PCOS and obesity. Future directions include a genome-wide association study in PCOS.

Genetic variants of cyclin-dependent kinase 5 regulatory subunit associated protein 1-like 1 and transcription factor 7-like 2 are not associated with polycystic ovary syndrome in Chinese women

Polycystic ovary syndrome (PCOS) is a common disorder in women that shares many genetic features with type 2 diabetes mellitus. Novel risk loci for type 2 diabetes, single nucleotide polymorphism (SNP) rs7756992 in cyclin-dependent kinase 5 (CDK5) regulatory subunit associated protein 1-like 1 (CDKAL1), rs290487 and rs11196218 in transcription factor 7-like 2 (TCF7L2), were recently identified. The aim of this study was to test whether these loci are also associated with PCOS. We recruited 826 patients with PCOS and 620 healthy controls for case-control analysis. The genotypes of these three SNPs were identified. The relationships between PCOS-related clinical endocrine and metabolic features and genotypes were also analyzed. Genotype distribution of these three loci in case and control groups showed no deviation from the Hardy-Weinberg equilibrium. No significant differences in genotype and allele frequencies were found between patients with PCOS and healthy controls. No associations were observed between genotypes of the three SNPs and the clinical endocrine and metabolic features of patients with PCOS in case group after adjustment for body mass index. We concluded that rs7756992 in CDKAL1, rs290487 and rs11196218 in TCF7L2 have no associations with PCOS or PCOS-related clinical features.

Polymorphisms of TCF7L2 and HHEX genes in Chinese women with polycystic ovary syndrome

PURPOSE

This study was to evaluate whether polymorphisms of TCF7L2 (rs7903146) and HHEX (rs1111875) genes responsible for insulin secretion are associated with the polycystic ovary syndrome (PCOS) in Chinese people.

METHODS

326 PCOS patients and 290 healthy individuals as controls were studied. Blood samples were obtained for DNA analyses and hormone measurements. Genotyping of the TCF7L2 (rs7903146) and HHEX (rs1111875) genes was carried out by the polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

We did not find statistically significant differences in the distribution of the TCF7L2 rs7903146 and HHEX rs1111875 polymorphisms between the Chinese women with PCOS and the controls. Levels of hormones such as insulin, FSH, LH, LH/FSH, P, T and E2 were also similar between the different genotypes of the genes TCF7L2 and HHEX, respectively, which was confirmed within either the PCOS subjects or controls.

CONCLUSIONS

There was no association of either of the two variants, rs7903146 of TCF7L2 and rs1111875 of HHEX, with the occurrence of PCOS in the Chinese population.

Angiotensin-converting enzyme gene polymorphism and risk of insulin resistance in PCOS

The aim of this study was to establish the frequency of angiotensin-converting enzyme (ACE) insertion (I) or deletion (D) gene polymorphism in women with polycystic ovary syndrome (PCOS) and to examine the association of this polymorphism with insulin resistance. A total of 32 women with PCOS and 31 healthy, age- and body mass index-matched controls were studied. Serum lipids, fasting glucose, insulin and other hormones concentrations were measured. Homeostasis model assessment was used to estimate insulin resistance (HOMA-IR). DNA was extracted from peripheral blood leukocytes and genotyping of ACE I/D polymorphism was carried out by polymerase chain reaction. ACE genotypes were distributed as follows: DD was present in 16 (50%), ID in 12 (37.5%) and II in four (12.5%) PCOS patients, and DD in seven (22.6%), ID in 20 (64.5%) and II in four (12.9%) of healthy subjects. The frequency of D and I alleles were found in 69% and 31% of the PCOS group and 55% and 45% in the control group, respectively. There were no significant differences regarding the genotypic distribution and allelic frequency between the groups. However the ACE DD genotype was significantly associated with serum insulin concentrations and HOMA-IR measurement (both P=0.005). ACE DD genotype is associated with an increased insulin resistance in women with PCOS.