A variant of the glucocorticoid receptor gene is not associated with adrenal androgen excess in women with polycystic ovary syndrome

The glucocorticoid receptor gene (NR3C1) is linked to and associated with polycystic ovarian syndrome in Italian families

OBJECTIVES

Components of the hypothalamic-pituitary axis (HPA) pathway are potential mediators of the genetic risk of polycystic ovarian syndrome (PCOS). Impaired glucocorticoid receptor (NR3C1) expression and function may underlie impaired HPA-axis cortisol activity, thereby also contributing to the increased adrenal cortisol and androgen production present in women with PCOS. In this study, we aimed to identify whether NR3C1 is linked or in linkage disequilibrium (LD), that is, linkage joint to association, with PCOS in Italian peninsular families.

METHOD

In 212 Italian families with type 2 diabetes (T2D) from the Italian peninsula, previously recruited for a T2D study and phenotyped for PCOS, we used microarray to genotype 25 variants in the NR3C1 gene. We analyzed the 25 NR3C1 variants by Pseudomarker parametric linkage and LD analysis.

RESULTS

We found the novel implication in PCOS risk of two intronic variants located within the NR3C1 gene (rs10482672 and rs11749561), thereby extending the phenotypic implication related to impaired glucocorticoid receptor.

CONCLUSIONS

To the best of our knowledge, this is the first study to report NR3C1 as a risk gene in PCOS.

Association of glucocorticoid receptor polymorphisms with clinical and metabolic profiles in polycystic ovary syndrome

OBJECTIVES

We aimed to investigate whether glucocorticoid receptor gene polymorphisms are associated with clinical and metabolic profiles in patients with polycystic ovary syndrome. Polycystic ovary syndrome is a complex endocrine disease that affects 5-8% of women and may be associated with metabolic syndrome, which is a risk factor for cardiovascular disease. Cortisol action and dysregulation account for metabolic syndrome development in the general population. As glucocorticoid receptor gene (NR3C1) polymorphisms regulate cortisol sensitivity, we hypothesized that variants of this gene may be involved in the adverse metabolic profiles of patients with polycystic ovary syndrome.

METHOD

Clinical, metabolic and hormonal profiles were evaluated in 97 patients with polycystic ovary syndrome who were diagnosed according to the Rotterdam criteria. The alleles of the glucocorticoid gene were genotyped. Association analyses were performed using the appropriate statistical tests.

RESULTS

Obesity and metabolic syndrome were observed in 42.3% and 26.8% of patients, respectively. Body mass index was positively correlated with blood pressure, triglyceride, LDL-c, total cholesterol, glucose and insulin levels as well as HOMA-IR values and inversely correlated with HDL-c and SHBG levels. The BclI and A3669G variants were found in 24.7% and 13.4% of alleles, respectively. BclI carriers presented a lower frequency of insulin resistance compared with wild-type subjects.

CONCLUSION

The BclI variant is associated with a lower frequency of insulin resistance in women with polycystic ovary syndrome. Glucocorticoid gene polymorphism screening during treatment of the syndrome may be useful for identifying subgroups of at-risk patients who would benefit the most from personalized treatment.

The adrenal and polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders characterized by androgen excess, oligo-ovulation and polycystic ovaries. Although ovaries are the main source of increased androgens in the syndrome, between 20 and 30% of patients with PCOS have adrenal androgen (AA) excess, detectable primarily by elevated dehydroepiandrosterone sulfate (DHEAS) levels. Patients with PCOS demonstrate a generalized hypersecretion of adrenocortical products, basally and in response to ACTH stimulation. The mechanisms of these abnormalities are unclear although AA excess in PCOS is likely a complex trait, modulated by both intrinsic and acquired factors. To date, no specific genetic defects have been identified. The production of AAs in response to ACTH appears to be closely related to altered factors regulating glucose-mediated glucose disposal, increased peripheral metabolism of cortisol, and to a less extent to the effects of extra-adrenal androgens, insulin resistance, hyperinsulinemia or obesity. Finally, DHEAS levels and the response of AAs to ACTH are relatively constant over time and are closely correlated between PCOS patients and their siblings suggesting that this abnormality is an inherited trait in PCOS.

Genetics of polycystic ovarian syndrome

Polycystic ovarian syndrome is a complex disorder with multiple factors affecting its etiology. Elucidation of specific genes and mode of inheritance remains a significant challenge. Linkage and association studies have resulted in over 50 candidate genes as a source of heritable predisposition; however, small sample sizes and failure to reproduce results have hindered efforts. In addition, low fecundity, lack of a male phenotype, and variation of diagnostic criteria represent unique challenges to discovery of polycystic ovarian syndrome genes. A concerted effort will be necessary to conclusively rule in or rule out candidate genes.

Genetics of polycystic ovary syndrome: searching for the way out of the labyrinth

Polycystic ovary syndrome (PCOS) is a complex and heterogeneous disorder presenting a challenge for clinical investigators. It is the most common endocrine disorder of women in reproductive age, a multifaceted reproductive, cosmetic and metabolic problem, with an enigmatic pathophysiological and molecular basis. Although the familial segregation has been noticed very early in the description of the syndrome and family studies in first-degree relatives of women diagnosed with PCOS reveal clustering of the disease, the genetic studies have not as yet determine the pattern of heredity. Part of the problem in genetic studies has been the lack of uniform criteria for diagnosis, heterogeneity of phenotypic features and the fact that the disorder is only expressed clinically in women during their reproductive years. Even within affected families and between sisters with polycystic ovaries, there is heterogeneity in presentation. However, regardless of diagnostic criteria used to identify profanes and to determine affected status in the kindred, the foundation of genetic studies suggests a strong familial component. Currently, PCOS is considered a polygenic trait that might result from the interaction of susceptible and protective genomic variants under the influence of environmental factors, whose role is under intensive investigation. Candidate genes cover a broad spectrum of an endless list of molecules which participate on every step of reproductive and metabolic pathways of this syndrome. Focused research in identification of these genes may provide valuable information and shed some light on the way out of the genomic labyrinth, elucidating the underlying pathophysiology and aiming at a more efficient therapeutic approach of this complicated endocrine disorder.

The molecular-genetic basis of functional hyperandrogenism and the polycystic ovary syndrome

The genetic mechanisms underlying functional hyperandrogenism and the polycystic ovary syndrome (PCOS) remain largely unknown. Given the large number of genetic variants found in association with these disorders, the emerging picture is that of a complex multigenic trait in which environmental influences play an important role in the expression of the hyperandrogenic phenotype. Among others, genomic variants in genes related to the regulation of androgen biosynthesis and function, insulin resistance, and the metabolic syndrome, and proinflammatory genotypes may be involved in the genetic predisposition to functional hyperandrogenism and PCOS. The elucidation of the molecular genetic basis of these disorders has been burdened by the heterogeneity in the diagnostic criteria used to define PCOS, the limited sample size of the studies conducted to date, and the lack of precision in the identification of ethnic and environmental factors that trigger the development of hyperandrogenic disorders. Progress in this area requires adequately sized multicenter collaborative studies after standardization of the diagnostic criteria used to classify hyperandrogenic patients, in whom modifying environmental factors such as ethnicity, diet, and lifestyle are identified with precision. In addition to classic molecular genetic techniques such as linkage analysis in the form of a whole-genome scan and large case-control studies, promising genomic and proteomic approaches will be paramount to our understanding of the pathogenesis of functional hyperandrogenism and PCOS, allowing a more precise prevention, diagnosis, and treatment of these prevalent disorders.

The genetics of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a heterogeneous disorder. There is evidence for a genetic component in PCOS based on familial clustering of cases. The majority of the evidence supports an autosomal dominant form of inheritance. Steroidogenesis has been shown to be upregulated in PCOS theca cells, suggesting that the genetic abnormality in PCOS affects signal transduction pathways controlling the expression of a family of genes. Although a number of candidate genes have been proposed, the putative PCOS gene(s) has yet to be identified. Linkage and association studies implicate a region near the insulin receptor gene at chr 19p13.3. New genetic approaches, such as microarray technology, hold promise for elucidation of the pathophysiology underlying PCOS.

The relation between two polymorphisms in the glucocorticoid receptor gene and body mass index, blood pressure and cholesterol in obese patients

OBJECTIVE

We have recently reported that, in healthy elderly Dutch individuals, a N363S polymorphism in the glucocorticoid receptor (GR) gene is associated with higher sensitivity to low-dose dexamethasone (0.25 mg), evaluated as both cortisol suppression and insulin response, and with an increased body mass index (BMI). In the present study we investigated the role of the N363S polymorphism, and a BclI restriction site polymorphism in a group of Italian patients with severe obesity.

DESIGN

Two hundred and seventy-nine patients (mean BMI 45.9 +/- 0.9 kg/m2) were genotyped using both PCR-restriction fragment length polymorphism analysis and Taqman Sequence Detection System. Determination of several metabolic and antropometric parameters was also performed in order to correlate them to the genotype.

RESULTS

In this group of obese patients, 13 subjects (eight female, five males) were heterozygous for the N363S variant (allelic frequency 2.3%) and had significantly higher BMI (P < 0.04), resting energy expenditure (P < 0.03) and food intake (P < 0.01) when compared to wild-type homozygotes. When the data were analysed according to sex, female heterozygotes for the N363S allele had significantly higher BMI (P = 0.04), resting energy expenditure (P = 0.03) and food intake (P = 0.008) than obese women with the wild-type 363 GR gene. Male carriers of this variant also had higher values for these variables although the differences did not reach statistical significance. A case-control study with homozygous wild-type obese subjects which were age-, sex- and BMI-matched, revealed no difference in resting energy expenditure and food intake. The allele frequency of the BclI variant was 27% (89 females and 41 males out of 269 subjects). No differences in anthropometric and metabolic parameters were found between subjects heterozygous or homozygous for this variant GR in this obese population. However, when we studied the effect of the presence of the BclI polymorphism and the N363S variant in the same individual, we found that the subjects who carried both polymorphisms had a tendency towards higher systolic and diastolic blood pressure and significantly higher total and LDL-cholesterol levels (P = 0.005 and P = 0.05, respectively).

DISCUSSION

Taking the results of this study and those obtained in the Dutch population, we speculate that heterozygous carriers of the N363S variant who develop obesity, may become even more obese, possibly because they have a hypersensitive insulin response and thus, via activation of lipogenesis, store fat more efficiently. Furthermore, these data suggest that N363S carriers who carry the BclI polymorphism as well, tend to have a slightly unfavourable cardiovascular profile.

Application of denaturing gradient gel electrophoresis (DGGE) to screen for mutations of the human glucocorticoid receptor alpha gene (hGRalpha)

OBJECTIVES

In a previous publication, we had presented a sensitive method to detect mutations of the segment of the human glucocorticoid receptor alpha (hGRalpha) gene encoding the ligand binding domain (LBD) and part of the DNA binding domain (DBD) of hGRalpha, as several types of glucocorticoid resistance syndromes have been correlated with mutations in the respective nucleotide sequences. However, mutations affecting various regions covering the whole length of hGRalpha are increasingly reported in a variety of disease states. We now present an expanded screening methodology to detect mutations covering the whole length of hGRalpha.

DESIGN AND METHODS

We developed a sensitive, simple screening PCR-DGGE method to detect mutations in the aminoterminal domain and DNA-binding domain of the hGRalpha. Wild type hGRalpha cDNA and mutant samples were included in the analysis to ensure the accuracy and sensitivity of the method.

RESULTS

The PCR-DGGE method identified the mutant samples and discriminated them from wild type hGRalpha.

CONCLUSIONS

The method described is accurate, sensitive, simple, cheap and fulfills the critera for a screening method which will be useful in delineating possible involvement of hGRalpha mutations in the aetiopathology of diseases correlated to derangements of glucocorticoid action.

Variations of the human glucocorticoid receptor gene (NR3C1): pathological and in vitro mutations and polymorphisms

Glucocorticoid (GC) resistance can occur in a number of diseases. It can be either generalized (i.e., familial glucocorticoid resistance) or localized (i.e., asthma). In many cases, a reason for this resistance to steroids lies with mutations or polymorphisms present in the glucocorticoid receptor gene (GR/NR3C1) that belongs to a large family of nuclear receptors. A number of GC-resistant cell lines have been isolated in vitro, some of which arose or may have arisen in vivo. These and the mutations defined in them are included in this review as well as mutations engineered in plasmids and expressed in vitro. It also lists polymorphisms and the individual studies where association-related studies have been performed. NR3C1 is located on chromosome 5q31 and contains 10 exons that code for a 777 amino acid protein. There are two naturally occurring isoforms of the NR3C1, GRalpha (functional) and GRbeta (no hormone-binding ability). A total of 15 missense, three nonsense, three frameshift, one splice site, and two alternative spliced mutations have been reported in the NR3C1 gene associated with glucocorticoid resistance as well as 16 polymorphisms. Mutation and polymorphism data for NR3C1 will soon be found on the newly created locus-specific database.

Molecular progress in infertility: polycystic ovary syndrome

OBJECTIVE

To review the evidence that polycystic ovary syndrome is a genetic disease.

DESIGN

Review of published literature.

RESULTS

The existing literature provides a strong basis for arguing that PCOS clusters in families. However, the mode of inheritance of the disorder is still uncertain, although the majority of studies are consistent with an autosomal dominant pattern, modified perhaps by environmental factors. In addition, studies on PCOS cells (theca, muscle, and adipocytes) in culture have documented a persistent biochemical and molecular phenotype that distinguishes them from normal cells. Although several loci have been proposed as PCOS genes including CYP11A, the insulin gene, and a region near the insulin receptor, the evidence supporting linkage is not overwhelming. The strongest case can be made for the region near the insulin receptor gene, as it has been identified in two separate studies. However, the responsible gene at chromosome 19p13.3 remains to be identified. Association studies have provided a number of potential loci with genetic variants that may create or add to a PCOS phenotype, including Calpain 10, IRS-1 and -2, and SHBG.

CONCLUSIONS

Collectively, these findings are consistent with the concept that a gene or several genes are linked to PCOS susceptibility. Because the mutations/genotypes associated with PCOS are rare, and their full impact on the phenotype incompletely understood, routine screening of women with PCOS or stigmata of PCOS for these genetic variants is not indicated at this time. Currently the treatment implications for individually identified genetic variants is uncertain and must be addressed on a case by case basis.