Inconsistent effects of the proline12 --> alanine variant of the peroxisome proliferator-activated receptor-gamma2 gene on body mass index in children and adolescent girls

Puberty and polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a heterogeneous familial disorder characterized by chronic anovulation and hyperandrogenism. This multi-system, polygenic, multi-factorial disorder is associated with an increased risk for metabolic abnormalities such as type 2 diabetes mellitus. Signs and symptoms of PCOS often emerge during the peri-pubertal years with premature pubarche (PP) being the earliest manifestation for some girls. Insulin resistance and hyperinsulinemia are important pathophysiological features that are common to both PP and PCOS. Future investigations are needed to uncover the relevant genetic and hormonal factors and identify effective interventions.

Genomic variants in polycystic ovary syndrome

The polycystic ovary syndrome (PCOS) is a common disorder in premenopausal women, characterized by the presence, among other traits, of hyperandrogenism, insulin resistance, and hyperinsulinism. The familial aggregation of PCOS lead the interest to the molecular genetic basis of this syndrome, especially to the genes encoding proteins involved in androgen synthesis and the regulation of insulin synthesis and action. Considering the relationship between insulin resistance and chronic inflammation, and the clustering of inflammatory markers in PCOS patients, recent studies focused on the involvement of proinflammatory genotypes on the pathogenesis of PCOS. Mounting evidence suggest at present a complex model of inheritance for PCOS, in which predisposing and protecting genomic variants interact with environmental factors such as obesity and a sedentary lifestyle, finally leading to the classic phenotype of this syndrome. Moreover, the association of hyperandrogenism, insulin resistance and chronic inflammation raised the possibility of an increase risk of cardiovascular disease in women suffering from PCOS. In the present review we will summarize the most important findings published to date regarding the molecular genetic mechanisms underlying the association of PCOS with insulin resistance and chronic inflammation, and the possible interaction of these mechanisms with environmental factors.

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.

Genetic Basis of Metabolic Abnormalities in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a common heterogeneous disorder characterized by hyperandrogenism and chronic anovulation. The syndrome is frequently associated with an increased risk for insulin resistance and type 2 diabetes mellitus; obesity exacerbates insulin resistance and favors the progression from impaired glucose tolerance to diabetes in these patients. In young women, precocious pubarche and hyperinsulinemia are early manifestations of PCOS. The familial clustering of women with PCOS suggests that heredity is implicated in the origin of the syndrome. However, genetic approaches to its pathogenesis have been hampered by the heterogeneity of phenotypic features within families, and the lack of uniform criteria for diagnosis. Currently, PCOS is considered a polygenic trait that might result from the interaction of susceptibility and protective genomic variants under the influence of environmental factors. Both linkage analysis and association studies are valid tools for the study of the genetics of PCOS. Candidate genes for PCOS include those related to androgenic pathways and metabolic associations of the syndrome. More recently, genes encoding inflammatory cytokines have been identified as target genes for PCOS, as proinflammatory genotypes and phenotypes are also associated with obesity, insulin resistance, type 2 diabetes, PCOS, and increased cardiovascular risk. This paper reviews the candidate genes involved in the metabolic pathways that are altered in patients with PCOS. Despite a significant amount of research in this area, none of the genes studied so far has been identified as the PCOS susceptibility gene for the majority of cases. PCOS is the first component of the metabolic syndrome to be detected in many women, so the identification and correct diagnosis of PCOS has important preventive and therapeutic implications for the affected women and their families. In the future, new therapeutic approaches to PCOS will rely on knowing the genes, environmental influences, and etiologic mechanisms associated with the disorder.

Frequency of the T228A polymorphism in the SORBS1 gene in children with premature pubarche and in adolescent girls with hyperandrogenism

OBJECTIVE

Because the metabolic actions of insulin are more impaired than the mitogenic pathways in polycystic ovary syndrome (PCOS), genes coding for proteins involved in insulin-mediated glucose transport can be considered as candidate genes. The sorbin and SH3-domain-containing-1 (SORBS1) gene codes for c-Cbl-associated protein (CAP) involved in insulin-mediated glucose uptake. An association study showed that a missense variant of the SORBS1 gene is protective against obesity and diabetes. We tested the hypothesis that the frequency of the protective allele would be decreased in children with premature pubarche and adolescent girls with hyperandrogenism.

DESIGN

Association study.

SETTING

Academic research environment.

PATIENT(S)

Children referred for the evaluation of premature pubarche (n = 79), adolescent girls with hyperandrogenism (n = 56), and healthy nondiabetic controls (n = 50).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Frequency of the T228A allele in our patients and the relationship of body mass index to presence or absence of the T228A variant in our patient population.

RESULT(S)

Using allele-specific restriction fragment length polymorphism, allele frequencies were found to be similar among the premature pubarche, hyperandrogenism, and control groups (6.0%, 4.6%, and 8.0%, respectively). No statistically significant relationships were found between the SORBS1 genotypes and body mass index or hormone status.

CONCLUSION(S)

This SORBS1 polymorphism does not play a major role in premature pubarche, hyperandrogenism, and/or polycystic ovary syndrome in our patient population.

Genetics and the pathophysiology of obesity

Obesity is a complex disease that involves interactions between environmental and genetic factors. Obesity results from an imbalance between food intake and energy expenditure over several years. The genetic approach both in animal models and in humans has allowed immense progress in the understanding of body weight regulation. Monogenic forms of obesity in humans have been characterized and result from mutations in genes involved in the central pathways of food intake regulation. However, these cases are extremely rare and generally obesity must be considered as a complex polygenic disease involving interactions between multiple genes and the environment. Numerous studies, including studies in children, have tried to identify "susceptibility" genes. At present, the results are not conclusive inasmuch as they are highly variable between studies and because the relative risk associating a specific gene allele and obesity remains low. Thus, it seems highly premature to genotype obese patients on a large scale for predictive testing. When specific pharmacological treatments based on recent discoveries become available, however, genetic testing could help discriminate between the subtypes of obesity that may respond differentially to treatment.

Analysis of the relationship between the Pro12Ala variant in the PPAR-gamma2 gene and the response rate to therapy with pioglitazone in patients with type 2 diabetes

OBJECTIVE

To investigate the influence of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) gene variants on the response rate to therapy with the thiazolidinedione (TZD) pioglitazone, because in vitro studies have suggested that genetic variants of the PPAR-gamma gene may influence the drug efficacy of TZD.

RESEARCH DESIGN AND METHODS

A total of 131 patients were treated in an open-label, randomized, multicenter study with pioglitazone (45 mg o.d.) during a course of >or=26 weeks. Response to the pioglitazone therapy was defined by either a >20% decrease in fasting plasma glucose or a >15% decrease in HbA(1c) values after 26 weeks of pioglitazone treatment. We evaluated the association between the PPAR-gamma genotype and the response rate to pioglitazone treatment.

RESULTS

The Pro12Ala and the Pro12Pro variants in the PPAR-gamma gene are not associated with the response rate to pioglitazone treatment in patients with type 2 diabetes. However, we identified initial fasting plasma glucose level >11.0 mmol/l, HbA(1c) value >9.0%, BMI >32 kg/m(2), and fasting C-peptide concentrations at baseline >2.5 pmol/l as predominant confounding factors for the responder frequency to pioglitazone treatment.

CONCLUSIONS

The Pro12Ala variant in the PPAR-gamma gene does not affect the therapy efficacy of pioglitazone, suggesting that the drug-treatment response is independent from pharmacogenetic effects between PPAR-gamma and its ligand pioglitazone. Whether the Ala12Ala genotype plays a role in the response rate to TZD therapy remains to be determined.