The FTO gene modifies weight, fat mass and insulin sensitivity in women with polycystic ovary syndrome, where its role may be larger than in other phenotypes

Gut microbiota in diabetic-linked polycystic ovarian syndrome: Mechanisms and therapeutic insights

Polycystic ovarian syndrome (PCOS) is a complex multisystem disorder prevalent among women of reproductive age, commonly marked by insulin resistance, hyperinsulinemia, and metabolic disruptions such as hypertension and dyslipidemia, which elevate risks of cardiovascular disease and hepatic steatosis. Recent advances underscore the gut microbiome's critical role in modulating insulin resistance and metabolic homeostasis in PCOS. This review highlights novel insights into gut dysbiosis-driven inflammation, gut-brain hormonal signaling, and immune modulation as underlying mechanisms connecting PCOS with metabolic dysfunction and diabetes. We comprehensively analyzed studies up to September 2024 on gut microbiota, diabetes, PCOS, and metformin, exploring emerging perspectives on the microbiome's therapeutic potential in managing PCOS. Metformin's dual role in insulin sensitivity improvement and gut microbiome modulation is emphasized, including its indirect effects on weight management. This review also identifies gaps in current research, urging a shift toward precision therapies targeting microbiome-related pathways in PCOS. Further exploration of the gut-brain axis, pathogen-associated molecular patterns, and the need for controlled clinical trials are discussed to enhance therapeutic approaches.

FTO rs17817449 Variant Increases the Risk of Severe Obesity in a Brazilian Cohort: A Case-Control Study

Purpose

Obesity is a complex disease caused by a combination of genetic, environmental, and epigenetic factors, and is associated with an increased risk of chronic diseases. The leptin-melanocortin pathway integrates peripheral signals about the body's energy stores with a central neuronal circuit in the hypothalamus. This pathway has been extensively studied over the years, as genetic variations in genes related to it may play a crucial role in determining an individual's susceptibility to obesity. Therefore, we analyzed the association between obesity and specific polymorphisms in leptin-melanocortin-related genes such as LEPR rs1137101, POMC rs1042571, LEP rs7799039, BDNF rs6265, FTO rs17817449, CART rs121909065, and NPY rs16147/rs5574.

Patients and Methods

The study enrolled 501 participants from Rio de Janeiro, Brazil, with obesity class II or greater (BMI ≥ 35 kg/m2) and normal weight controls (18.5≤ BMI ≤24.9 kg/m2). We collected demographic, body composition, biochemical, and genotyping data by real-time PCR, and performed logistic and linear regression analyses to investigate the association of polymorphisms with severe obesity status and obesity-related quantitative parameters.

Results

Individuals with severe obesity had significantly higher anthropometric measures, blood pressure, and biochemical levels. The FTO rs17817449 TT genotype was associated with a significantly higher risk of developing severe obesity, and distinct cytokine expression was observed across the FTO rs17817449 genotypes. The BDNF rs6265 dominant-model and NPY rs16147 CC genotypes were associated with triglyceride levels and childhood obesity, respectively. Finally, individuals with obesity were more likely to carry a greater number of risk alleles than those without obesity.

Conclusion

Our study observed an important association between FTO rs17817449 polymorphism with obesity and obesity-related traits. Additionally, BDNF rs6265 dominant-model was associated with triglyceride serum levels, and NPY rs16147 may have a role in obesity onset.

Albizia ferruginea (Guill. & Perr.) Benth. leaf abates deregulation of P53, IRS, HsD17β2, FTO, and CYP11a genes in polycystic ovarian syndrome rat

OBJECTIVES

This study investigated the potential ameliorative effects of Albizia ferruginea leaves on letrozole-induced PCOS in Wistar rats.

METHODS

PCOS was induced in 25 female Wistar rats by administering letrozole (1 mg/kg), followed by treatment with 100 and 250 mg/kg body weight A. ferruginea leaf methanolic extract, as well as 1 mg/kg body weight of Clomiphene citrate as standard.

RESULTS

An acute toxicity study revealed a toxic dosage of 2,000 mg/kg for the plant extract. The A. ferruginea extract exhibited potent hydroxyl radical scavenging ability. Treatment with A. ferruginea leaf extract improved the irregular estrus cycle and hormonal imbalance. Additionally, the extract administration led to decreased testosterone and increased estradiol levels when compared to the untreated PCOS rat. Furthermore, methanol extract normalizes the levels of insulin receptor substrate (IRS), type 2 17-HSD (HsD17β2), P53, 11a-hydroxylase/17,20-desmolase (CYP11a), and fat mass and obesity-associated (FTO), genes in the cervix of PCOS rats.

CONCLUSIONS

Overall, A. ferruginea demonstrated beneficial properties on polycystic ovary circumstances in rats, presenting its potential as a promising treatment for PCOS.

The ameliorative effect of CangFu Daotan Decoction on polycystic ovary syndrome of rodent model is associated with m6A methylation and Wnt/β-catenin pathway

Objective: This study investigates the effects of CangFu Daotan Decoction (CDD) on m6A methylation and Wnt/β-catenin pathway in rats with polycystic ovary syndrome (PCOS).Methods: The PCOS rat model was established by letrozole gavage. The rats were fed high-fat chow, and their body weight and blood glucose were recorded. The expressions of follicle-stimulating hormone(FSH), luteinizing hormone(LH), and testosterone(T) were quantified by ELISA. Chemical components in CDD were analyzed using UPLC-Q/TOF-MS. Based on network pharmacology methods, related targets of CDD on PCOS were screened. An enrichment analysis according to Tokyo Encyclopedia of Genes and Genomes (KEGG) was conducted to predict the potential signaling pathway of CDD in PCOS. The expressions of Wnt-1, β-Catenin, GSK-3β, C-MYC, Beclin1, LC3II, Bax, and PCNA were detected by western blotting. The expressions of Mettl3, Mettl14, Fto, Alkbh5, Ythdf1, and Ythdf2 were monitored by RT-PCR. The expressions of Mettl3, Fto, and Ythdf1 were detected by western blotting.Results: Letrozole and a high-fat diet induced ovarian dysfunction in rats, which was attenuated by CDD. CDD decreased blood glucose, LH, and T concentrations and increased FSH expression in PCOS. After removing duplicates, a total of 71 compounds were identified by UHPLC-Q/TOF-MS, among which terpenoids and flavonoids account for the main proportion. The clustering analysis showed that the active site of CDD might be in the Wnt/β-catenin pathway. CDD decreased the expressions of Wnt-1, β-Catenin, GSK-3β, C-MYC, Beclin1, LC3II, and Bax and increased PCNA expression in the ovarian tissue of PCOS rats. CDD decreased the m6A gene expressions of Mettl3, Mettl14, Fto, Alkbh5, Ythdf1, and Ythdf2 in peripheral blood and ovarian tissue of PCOS rats. CDD reduced the m6A proteins expressions of Mettl3, Fto, and Ythdf1 in the ovarian tissue of PCOS rats.Conclusion: CDD can regulate m6A modification and inhibit the Wnt/β-catenin signaling pathway in PCOS rats, thereby reducing body weight, lowering blood glucose levels, improving sex hormone disorders, and decreasing autophagy and apoptosis in ovarian tissue to promote the recovery of ovarian morphology.

N6-methyladenosine demethylase FTO related to hyperandrogenism in PCOS via AKT pathway

BACKGROUND

Polycystic ovary syndrome (PCOS) was known as the common endocrine disease in women, featured as hyperandrogenism, ovulation disorders, etc. Fat mass and obesity-associated protein (FTO), a m6A demethylase, is abnormal in the occurrence of ovarian diseases. However, the mechanism of FTO in the pathogenesis of PCOS is still unclear.

METHODS

The level of FTO in clinical samples, PCOS rat with hyperandrogenism and granulosa cells (GCs) lines effected by DHT were investigated by ELISA, qRT-PCR, WB, and IHC, while m6A RNA methylation level was studied by m6A Colorimetric and androgen level was tested through ELISA. Changes in steroid hormone synthetase and androgen receptor (AR)/prostate-specific antigen (PSA) levels in vitro were visualized by WB after transient transfection silenced FTO. The effect of DHT combined with FTO inhibitor meclofenamic acid (MA) on FTO, AR/PSA, and AKT phosphorylation were also demonstrated by WB. The co-localization of FTO and AR in KGN cells was analyzed by confocal microscopy, and the physiological interaction between FTO and AR was studied by Co-IP assay. The effect of FTO-specific inhibitor MA, AKT phosphorylation inhibitor LY294002, and the combined them on GCs proliferation and cell cycle were evaluated by drug combination index, EDU assay, and flow cytometry analysis.

RESULTS

FTO expression was upregulated in follicular fluid and GCs in PCOS patients clinically. The high FTO expression in patients was negative with the level of m6A, but positive with the level of androgen. The upregulation of FTO was accompanied with a decrease in the level of m6A in PCOS rat with hyperandrogenism. Dihydrotestosterone (DHT) promoted the FTO expression and inhibited m6A content as a dose-dependent way in vitro. In contrast, suppression of FTO with siRNA attenuated the expression of steroid hormone synthetase such as CYP11A1, CYP17A1, HSD11B1, HSD3B2 except CYP19A1 synthetase, ultimately inducing the decrease of androgen level. Suppression of FTO also decreased the biological activity of androgen through downregulation AR/PSA. MA treatment as the specific FTO antagonist decreased cell survival in time- and dose-dependent way in GCs lines. Correspondingly, MA treatment decreased the expression of FTO, AR/PSA expression, and AKT phosphorylation in the presence of DHT stimulation. Additionally, we also speculate there is a potential relation between FTO and AR according to FTO was co-localized and interacted with AR in KGN cells. Compared with AKT phosphorylation inhibitor LY294002 or MA alone, LY294002 combined with MA synergistically inhibited cell survival and increased G2/M phase arrest in GC line.

CONCLUSIONS

We first evaluated the correlation of FTO and m6A in PCOS clinically, and further explored the mechanism between FTO and hyperandrogenism in PCOS animal and cell models. These findings contributed the potential therapy by targeting the FTO for hyperandrogenism in PCOS.

Association of FTO gene variant rs9939609 with polycystic ovary syndrome from Gujarat, India

BACKGROUND

Polycystic ovary syndrome is a multifactorial endocrine disorder impacting women of reproductive age. Variations within the FTO gene have been linked to both obesity and type 2 diabetes mellitus. Given that PCOS is frequently associated with obesity and compromised glucose tolerance, we investigated the prevalence of the rs9939609 variant within the FTO gene among women diagnosed with PCOS and a control group. Our aim is to uncover potential correlations between this genetic variant, metabolic attributes, and endocrine markers within the Gujarat province of India.

METHOD

We enrolled a total of 114 participants, (62 individuals diagnosed with PCOS and 52 healthy controls). DNA extraction from venous blood was conducted for all participants. The rs9939609 polymorphism was investigated through tetra-primer amplification refractory mutation system-polymerase chain reaction. Furthermore, we performed biochemical assessments to quantify levels of estradiol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), total testosterone, prolactin (PRL), and Dehydroepiandrosterone sulfate (DHEAS). Statistical analyses were carried out utilizing SPSS version 21 (IBM, USA).

RESULTS

The present study did not reveal any noteworthy association between cases and controls. The frequencies of genotypes and alleles within the cohorts displayed no statistically significant differences (p = 0.25, p = 0.68, and p = 0.78, respectively). The dominant model indicated a modest risk (OR:1.13, 95%CI: 0.55 to 2.38) toward PCOS development. There was a noticeable statistical difference observed in the levels of total testosterone, DHEAS, and BMI between the case and control groups (p < 0.002, p < 0.0002, p < 0.0008). However, no variations in clinical variables were observed among genotypes within the PCOS group.

CONCLUSION

This is the first study to investigate the association of FTO gene polymorphism and PCOS in Gujarati population. Our study findings indicate that the FTO gene variant is not directly linked to the onset of PCOS. However, it appears to exert an influence on metabolic factors such as obesity and insulin resistance. Notably, our results suggest that insulin resistance is more frequently observed among PCOS patients who are obese, as compared to those with non-obese PCOS patients.

Crosstalk between FTO gene polymorphism (rs9939609) and obesity-related traits among Bangladeshi population

Background and Aims

Obesity is a growing public health concern in Bangladesh, which is influenced by a complex interplay of genetic and environmental factors. The genetic variant rs9939609 of the FTO (fat mass and obesity-associated) gene has been found to be associated with an increased risk for obesity, depending on the population studied. The purpose of this cross-sectional study is to examine the relationship between the FTO gene polymorphism (rs9939609) and lifestyle-related risk factors, and their impact on obesity-related traits and biochemical parameters in the Bangladeshi population.

Methods

A total of 280 participants were enrolled in this study, comprising of 140 individuals with overweight and obesity (body mass index [BMI] ≥ 23.0) and 140 non-overweight healthy individuals (18.5 ≤ BMI ≥ 22.9). Demographic information, dietary behaviors, and physical activity-related data were collected using a structured questionnaire. Additionally, anthropometric assessments and measurements of biochemical parameters such as lipid profile and C-reactive protein were performed. The amplification refractory mutation system-polymerase chain reaction technique was used to identify single-nucleotide polymorphism in the FTO gene. Descriptive statistics, χ,2 and one-way ANOVA were performed to evaluate the relationships between independent and dependent variables.

Results

The presence of rs9939609 was strongly associated with the obesity risk factors of increased BMI, cholesterol, triglycerides, and low-density lipoprotein. We also found a significant association (p < 0.05) of rs9939609 with overweight and obesity in codominant AA versus TT (odds ratio [OR] = 0.299, 95% CI: 0.129-0.695) and AA versus AT (OR = 2.273, 95% CI: 1.023-5.053), recessive TT versus AA+AT (OR = 5.154, 95% CI: 2.463-10.782), and overdominant AT versus AA+TT (OR = 0.244, 95% CI: 0.122-0.488) models.

Conclusion

FTO variant rs9939609 is significantly linked to obesity and an increased risk of hyperlipidemia in the Bangladeshi population. However, this association is intertwined with environmental factors such as diet and physical activity.

Does the rs9939609 FTO gene polymorphism affect fat percentage? A meta-analysis

This meta-analysis aimed to investigate the association of the rs9939609 FTO gene polymorphism and body fat percentage (BF%). To the best of our knowledge, this study is the first meta-analysis to evaluate the relationship between FTO rs9939609 polymorphism and BF%. We searched PubMed, Web of science, Scopus and Embase to identify studies investigating the relations between the rs9939609 FTO gene polymorphism and BF%. Studies that meet inclusion criteria were collected for the final analysis. There was significant differences in the level of BF% between different genotypes of FTO rs9939609 polymorphism, and the carriers of the A allele of FTO rs9939609 polymorphism had higher BF%. The association was significant between carriers of TT genotype compared to carriers of AA (p = .007) and AT genotypes (p = .04), but not between AT and AA genotypes. This study identified that the carriers of the A allele of FTO rs9939609 polymorphism have higher BF%.

Association of FTO gene variant rs9939609 with hyperandrogenemia and fasting glucose levels in South Indian women with polycystic ovarian syndrome

Background

Polycystic ovary syndrome (PCOS) is a common endocrine–metabolic disorder due to genetic and environmental factors. Genetic variants located in intron 1 of Fat mass and obesity-associated (FTO) gene are associated with increased risk of obesity and metabolic disorders. This study aims to investigate the association of common FTO polymorphism rs9939609 in South Indian women with PCOS to assess its association with metabolic and endocrine parameters. FTO genotyping was done on 100 PCOS patients and 70 controls by Sanger sequencing.

Results

The distribution of rs9939609 was observed between groups (28% TT, 57% TA, and 15% AA for PCOS and 37.1% TT, 51.4% TA, and 11.4% AA for the controls). In the PCOS group, across the carriers of different genotypes, a significant association was found between body mass index (BMI), fasting glucose levels, and testosterone with the presence of at least one risk allele of FTO rs9939609. Logistic regression analysis showed the association of fasting glucose levels and testosterone (OR 1.30 [1.03–1.63] and OR 5.83 [1.61–21.11], respectively) with FTO rs9939609.

Conclusions

Our findings indicated that FTO SNP rs9939609 was not associated with PCOS, but suggested a significant association of rs9939609 with hyperandrogenemia, fasting glucose levels, and BMI in South Indian women with PCOS.

Association of FTO gene variants rs9939609 and rs1421085 with polycystic ovary syndrome

Background

Polycystic ovary syndrome (PCOS) is among the most common complex genetic endocrinopathy, and its etiology and pathophysiology remain controversial. FTO is a large highly polymorphic gene and was coined as the first locus associated with adiposity. The association of the intronic variant FTO rs9939609 or FTO rs1421085 with PCOS has been controversial and unclear, mainly due to ethnic differences among populations. The present study aims to investigate the association of FTO rs9939609 or FTO rs1421085 polymorphisms with PCOS in Saudi Arabian women.

Results

A total of 98 PCOS patients and 99 healthy females were included in this study. PCR and genotyping (TaqMan®SNP Genotyping Assay) were employed. For FTO rs9939609, the genotype TA and the recessive model (TA + AA) in PCOS patients were significantly different compared with control subjects (p = 0.008 and p = 0.007, respectively). The allele frequency of the FTO rs9939609 gene variant was associated significantly (p = 0.027) with PCOS, suggesting that the A allele is a risk factor for PCOS susceptibility. However, for the FTO rs1421085 variant, the genotype and allele distributions did not differ significantly between PCOS patients and controls (p > 0.05).

Conclusions

This is the first report to study the association of FTO rs9939609 and FTO rs1421085 with PCOS in Saudi women. Results suggest that the FTO rs9939609 gene variant could be a genetic predisposing factor for PCOS Saudi women.

N6-methyladenosine Demethylase FTO Induces the Dysfunctions of Ovarian Granulosa Cells by Upregulating Flotillin 2

Polycystic ovarian syndrome (PCOS) is often accompanied by overweight/obesity and insulin resistance. The dysfunctions of ovarian granulosa cells (GCs) are closely linked with the pathogenesis of PCOS. Fat mass and obesity-associated gene (FTO), an N6-methyladenosine (m6A) demethylase, has been reported to be implicated in the risks and insulin resistance of PCOS. However, the roles of FTO in the development of GCs along with its m6A-related regulatory mechanisms are poorly defined. Cell proliferative ability was detected by MTT assay. Cell apoptotic rate was measured via flow cytometry. Insulin resistance was assessed by GLUT4 transport potential. The mRNA and protein levels of FTO and flotillin 2 (FLOT2) were determined by RT-qPCR and western blot assays, respectively. FLOT2 was screened out to be a potential FTO target through differential expression analysis for the GSE95728 dataset and target prediction analysis by POSTAR2 and STARBASE databases. The interaction between FTO and FLOT2 was analyzed by RNA immunoprecipitation (RIP) assay. The effect of FTO upregulation on FLOT2 m6A level was measured by methylated RIP (meRIP) assay. FLOT2 mRNA stability was examined by actinomycin D assay. FTO overexpression facilitated cell proliferation, hindered cell apoptosis, and induced insulin resistance in GCs. FTO promoted FLOT2 expression by reducing m6A level on FLOT2 mRNA and increasing FLOT2 mRNA stability. FLOT2 loss weakened the effects of FTO overexpression on cell proliferation/apoptosis and insulin resistance in GCs. FTO induced the dysfunctions of GCs by upregulating FLOT2, suggesting that FTO/FLOT2 might play a role in the pathophysiology of PCOS.

In depth analysis of the association of FTO SNP (rs9939609) with the expression of classical phenotype of PCOS: a Sri Lankan study

Background

PCOS is a common disorder of women due to genetic, endocrine and environmental effects that manifests from puberty. The rs9939609 variant of fat mass and obesity associated (FTO) gene is linked to metabolic derangement in PCOS. We previously identified FTO (rs9939609) as a susceptibility locus for PCOS among Sri Lankan women and also explored the role of kisspeptin. Associated factors of the FTO candidate gene among South Asians with PCOS are unknown.

Methods

This study aimed to determine the association between FTO (rs9939609) polymorphism with clinical (BMI, acanthosis nigricans, hirsutism) and biochemical (serum kisspeptin and testosterone levels) characteristics of PCOS in a cohort of Sri Lankan women. Genetic and clinical data including serum kisspeptin and testosterone concentrations of our previously reported cases (n = 55) and controls (n = 110) were re-analyzed, specifically for an association with rs9939609 variant of FTO gene.

Results

Logistic regression analysis (AA – OR = 5.7, 95% CI = 2.41–13.63, p < 0.05) and genetic inheritance analysis (AA – OR = 5.49, 95%CI = 2.34–12.88, p < 0.05) showed that FTO (rs9939609) polymorphism is significantly associated with PCOS and its metabolic manifestations. Serum testosterone was significantly higher in affected women with mutant genotypes (AA+AT) than with the normal allele (TT) (p < 0.05). Although serum kisspeptin was higher in subjects with PCOS and mutant alleles than controls, this difference was not significant (p > 0.05).

Conclusion

FTO gene variant rs9939609 is associated with hyperandrogenemia and metabolic manifestations of PCOS among women of Sri Lankan descent with the well-characterized phenotype. Serum kisspeptin and the FTO genotypes lack a significant association when adjusted for confounders.

The Influence of FTO Polymorphism rs9939609 on Obesity, Some Clinical Features, and Disturbance of Carbohydrate Metabolism in Patients with Psoriasis

Background

Psoriasis is often accompanied by obesity, hyperlipidemia, diabetes, and metabolic syndrome as risk factors of cardiovascular conditions and premature mortality.

Objective

The study was aimed at investigating whether psoriatic patients, who carry risk allele of obesity-related FTO gene, are more predisposed to obesity and metabolic disturbances and whether it influences the severity of psoriasis.

Methods

197 patients with psoriasis, representing Lower Silesia region of Poland, underwent physical examination and anthropometric measurements. Blood samples for biochemical and genetic analysis were collected. All patients were genotyped for FTO gene rs9939609 variant. Identification of SNP was conducted with the use of minisequencing method.

Results

Around 63% of patients were carriers of at least one risk allele A and 20% were AA homozygotes. The A allele was associated with increased BMI and hip and waist circumferences. The carriers of risk allele had increased PASI and CRP values and tended to have an increased insulin concentration.

Conclusion

Psoriatic patients, carriers of risk allele of FTO gene rs9939609, have an increased risk for more severe psoriasis and obesity and may develop obesity-induced insulin resistance.

Polycystic ovary syndrome and the risk of cardiometabolic complications in longitudinal studies

The purpose of this study was to perform a review of the longitudinal studies to determine whether polycystic ovary syndrome is associated with higher prevalence of metabolic complications and cardiovascular morbidity and mortality. The primary outcomes included body mass index, metabolic syndrome and its components (waist circumference, lipid profile, arterial hypertension, abnormal glucose metabolism (impaired fasting glucose, impaired glucose tolerance, type 2 diabetes), insulin resistance, and cardiovascular diseases like stroke, angina, and coronary heart disease. Complications in pregnant women were beyond the scope of this review. PubMed database (1992-2018) was searched to identify proper publications. Finally, data from 47 articles were analysed. Studies differed in the design (prospective, retrospective, cohort, observational), research methods, polycystic ovary syndrome diagnostic criteria, studied populations, race, and ethnicity of the participants. Based on the data collected, it appears that women with polycystic ovary syndrome have higher prevalence of obesity, abdominal fat distribution, dyslipidaemia and deterioration of glucose metabolism, but increased prevalence of cardiovascular diseases is not proven.

Neuroendocrine Regulation of Food Intake in Polycystic Ovary Syndrome

Several peripheral and central signals are involved in the sophisticated regulation of food intake. Women with polycystic ovary syndrome (PCOS) are prone to consume a diet higher in saturated fat and foods with high glycemic index and show impaired appetite regulation and measures of satiety. As a consequence, obesity, mostly of the central type, is prevalent in the syndrome and worsens the endocrine and metabolic profile of the affected patients. This review article briefly analyzes the current knowledge about the neuroendocrine mechanisms underlying the interplay between feeding behavior, obesity, and reproductive abnormalities in PCOS.

The importance of gene-environment interactions in human obesity

The worldwide obesity epidemic has been mainly attributed to lifestyle changes. However, who becomes obese in an obesity-prone environment is largely determined by genetic factors. In the last 20 years, important progress has been made in the elucidation of the genetic architecture of obesity. In parallel with successful gene identifications, the number of gene-environment interaction (GEI) studies has grown rapidly. This paper reviews the growing body of evidence supporting gene-environment interactions in the field of obesity. Heritability, monogenic and polygenic obesity studies provide converging evidence that obesity-predisposing genes interact with a variety of environmental, lifestyle and treatment exposures. However, some skepticism remains regarding the validity of these studies based on several issues, which include statistical modelling, confounding, low replication rate, underpowered analyses, biological assumptions and measurement precision. What follows in this review includes (1) an introduction to the study of GEI, (2) the evidence of GEI in the field of obesity, (3) an outline of the biological mechanisms that may explain these interaction effects, (4) methodological challenges associated with GEI studies and potential solutions, and (5) future directions of GEI research. Thus far, this growing body of evidence has provided a deeper understanding of GEI influencing obesity and may have tremendous applications in the emerging field of personalized medicine and individualized lifestyle recommendations.

Polymorphisms of the FTO and MTHFR genes and vascular, inflammatory and metabolic marker levels in postmenopausal women

OBJECTIVE

To determine the prevalence of three single nucleotide polymorphisms (SNPs) in postmenopausal women with and without the metabolic syndrome (METS) and to explore levels of circulating biomarkers of inflammation, vascular and metabolic dysfunction according to SNP genotypes.

METHODS

DNA was extracted from the whole blood of 192 natural postmenopausal women (40 to 65 years) screened for the METS and tested for three gene SNPs related to obesity: the fat mass obesity (FTO: rs9939609) and the methylenetetrahydrofolate reductase (MTHFR: C677T and A1298C). Blood levels of angiopoietin, IL-8, sFASL, IL-6, TNF-α, sCD40L, PAI-1, u-PA, leptin, adiponectin, resistin, ghrelin, visfatin, adipsin and insulin were measured in a subgroup, with and without the METS, using multiplex technology (n = 100) and compared according to SNP genotypes.

RESULTS

Genotype frequency of the three studied SNPs did not differ in relation to the presence of the METS. However, genotypes CT+TT (C677T) and AT (rs9939609) were more prevalent in women with high triglyceride levels. Pooled sub-analysis (n = 100) found that median sCD40L and visfatin levels were higher in women with genotypes AT+TT (rs9939609) as compared to AA (1178 vs. 937.0 pg/mL and 0.93 vs. 0.43 ng/mL, respectively, p < 0.05).

CONCLUSION

Two SNP genotypes related to obesity were more prevalent in women with abnormal triglyceride levels and two vascular and inflammatory serum markers were higher in relation to the rs9939609 SNP.

Interaction between common variants of FTO and MC4R is associated with risk of PCOS

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common and complex endocrine-metabolic disease. One of the well-documented characteristics of PCOS is obesity or overweightness. It is possible to be genetically predisposed to becoming obese or overweight, and several potentially causative single nucleotide polymorphisms (SNPs), such as rs9939609 (A/T) in the fat mass, and obesity-associated gene (FTO) and rs17782313 (T/C) in the melanocortin-4 receptor gene (MC4R), have been investigated. Further investigation of association between obesity-associated SNPs and PCOS susceptibility will contribute to a better understanding of the disease.

METHODS

In the present study, we enrolled 733 patients with PCOS and 892 control subjects. The common variants FTO rs9939609 and MC4R rs17782313 were genotyped and their relationship with obesity-related traits was evaluated.

RESULTS

Rs9939609 and rs17782313 are associated with PCOS and obesity-related traits and profiles. The association found between PCOS and FTO rs9939609 (p=0.0302) was attenuated after adjustment for BMI (p=0.187). MC4R rs17782313 did not confer an increased risk for PCOS (p=0.368) even after adjustments (p=0.715). Interestingly, the interaction of FTO and MC4R polymorphisms was more significantly associated with PCOS (p=0.031, adjusted for age and BMI). The FTO variant rs9939609 is associated with Chinese women with PCOS; however, this association is affected by BMI.

CONCLUSIONS

The combined pathogenic effect of FTO and MC4R polymorphisms indicates a direct role of the interaction between FTO and MC4R polymorphisms in the development of PCOS.

FTO gene variants are not associated with polycystic ovary syndrome in women from Southern Brazil

BACKGROUND AND AIMS

Polycystic ovary syndrome (PCOS) is a common endocrine disorder, presenting polygenic traits as well as determined by environmental factors. Given the overlap between PCOS and obesity, we assessed the frequencies of SNPs rs9939609 and rs8050136 in intron 1 of the FTO gene and their haplotypes in women with PCOS and healthy controls with regular cycles from Southern Brazil and investigated their relationship with metabolic traits and endocrine parameters.

SUBJECTS AND METHODS

The sample comprised 298 women (199 with PCOS and 99 non-hirsute women with regular ovulatory cycles). FTO genotyping was done by real-time PCR. Haplotypes were constructed from the combination of both polymorphisms. Frequencies were inferred using PHASE 2.1.1 software.

RESULTS

The distribution of rs9939609 (PCOS: 32.6% TT, 45.9% TA, 21.5% AA; controls: 33.3% TT, 49.0% TA, 17.7% AA) and rs8050136 (PCOS: 21.7% AA, 43.3% AC, 35.0% CC; controls: 14.9% AA, 48.9% AC, 36.2% CC) was similar between groups. The mean age of participants was 22.7±7.1years. Women with PCOS had significantly higher BMI, waist circumference, total testosterone, and FAI vs. controls. In the PCOS group, no differences between genotypes and haplotypes were found for clinical variables. The presence of at least one risk allele for polymorphisms rs9939609 and rs8050136 was associated with higher fasting glucose levels.

CONCLUSION

Our findings indicate that neither the FTO rs9939609 and rs8050136 polymorphisms nor its haplotypes are related to PCOS, but suggest an association between the presence of risk alleles of SNPs rs9939609 and rs8050136 in FTO and glucose levels in women from Southern Brazil.

FTO Gene Variants Are Associated with PCOS Susceptibility and Hyperandrogenemia in Young Korean Women

BACKGROUND

The fat mass and obesity-associated (FTO) gene is associated with obesity and type 2 diabetes mellitus. Obesity and insulin resistance are also common features of polycystic ovary syndrome (PCOS). Therefore, the FTO gene might be a candidate gene for PCOS susceptibility. The aim of the present study was to evaluate the effects of FTO gene variants on PCOS susceptibility and metabolic and reproductive hormonal parameters.

METHODS

We recruited 432 women with PCOS (24±5 years) and 927 healthy women with regular menstrual cycles (27±5 years) and performed a case-control association study. We genotyped the single nucleotide polymorphisms rs1421085, rs17817449, and rs8050136 in the FTO gene and collected metabolic and hormonal measurements.

RESULTS

Logistic regression revealed that the G/G genotype (rs1421085, 1.6%), the C/C genotype (rs17817449, 1.6%), and the A/A genotype (rs8050136, 1.6%) were strongly associated with an increased risk of PCOS (odds ratio, 2.551 to 2.559; all P<0.05). The strengths of these associations were attenuated after adjusting for age and BMI. The women with these genotypes were more obese and exhibited higher free androgen indices (P<0.05) and higher free testosterone levels (P=0.053 to 0.063) compared to the other genotypes. However the significant differences disappeared after adjusting for body mass index (BMI). When we analyzed the women with PCOS and the control groups separately, there were no significant differences in the metabolic and reproductive hormonal parameters according to the FTO gene variants.

CONCLUSION

The rs1421085, rs17817449, and rs8050136 variants of the FTO gene were associated with PCOS susceptibility and hyperandrogenemia in young Korean women. These associations may be mediated through an effect of BMI.

Gene dose effect between a fat mass and obesity-associated polymorphism and body mass index was observed in Korean women with polycystic ovary syndrome but not in control women

OBJECTIVE

To examine the association between fat mass and obesity-associated (FTO) polymorphisms and polycystic ovary syndrome (PCOS) in Korean women.

DESIGN

Case-control study.

SETTING

University department of obstetrics and gynecology.

PATIENT(S)

Women with (n = 552) or without (n = 559) PCOS.

INTERVENTION(S)

Genotyping was performed.

MAIN OUTCOME MEASURE(S)

FTO rs9939609 genotype distribution and correlation between variants in this gene and PCOS phenotypes.

RESULT(S)

The mean body mass index (BMI) of the patients was significantly higher than that of the control subjects (22.0 ± 4.1 kg/m(2) vs. 20.1 ± 2.5 kg/m(2)), but most (81.3%) of the patients were not obese. FTO rs9939609 was not significantly associated with PCOS itself. However, a positive correlation was observed between the number of variant alleles and BMI in women with PCOS: Each additional copy of the variant allele increased BMI by a mean (95% confidence interval) of 4.8% (1.4%-8.3%) or 1.11 kg/m(2) (1.03-1.20 kg/m(2)) after adjusting for age. This correlation was not observed in the control subjects.

CONCLUSION(S)

FTO rs9939609 was not a major determinant of PCOS. However, in the women with PCOS who were primarily nonobese, a gene dose effect was observed for BMI. The FTO gene may play an influential role in predisposition to PCOS via an association with obesity.

Childhood obesity and its impact on the development of adolescent PCOS

Obesity exacerbates the reproductive and metabolic manifestations of polycystic ovary syndrome (PCOS). The symptoms of PCOS often begin in adolescence, and the rising prevalence of peripubertal obesity has prompted concern that the prevalence and severity of adolescent PCOS is increasing in parallel. Recent data have disclosed a high prevalence of hyperandrogenemia among peripubertal adolescents with obesity, suggesting that such girls are indeed at risk for developing PCOS. Obesity may impact the risk of PCOS via insulin resistance and compensatory hyperinsulinemia, which augments ovarian/adrenal androgen production and suppresses sex hormone-binding globulin (SHBG), thereby increasing androgen bioavailability. Altered luteinizing hormone (LH) secretion plays an important role in the pathophysiology of PCOS, and although obesity is generally associated with relative reductions of LH, higher LH appears to be the best predictor of increased free testosterone among peripubertal girls with obesity. Other potential mechanisms of obesity-associated hyperandrogenemia include enhanced androgen production in an expanded fat mass and potential effects of abnormal adipokine/cytokine levels. Adolescents with PCOS are at risk for comorbidities such as metabolic syndrome and impaired glucose tolerance, and concomitant obesity compounds these risks. For all of these reasons, weight loss represents an important therapeutic target in obese adolescents with PCOS.

BMI-associated alleles do not constitute risk alleles for polycystic ovary syndrome independently of BMI: a case-control study

Introduction

Polycystic Ovary Syndrome (PCOS) has a strong genetic background and the majority of patients with PCOS have elevated BMI levels. The aim of this study was to determine to which extent BMI-increasing alleles contribute to risk of PCOS when contemporaneous BMI is taken into consideration.

Methods

Patients with PCOS and controls were recruited from the United Kingdom (563 cases and 791 controls) and The Netherlands (510 cases and 2720 controls). Cases and controls were of similar BMI. SNPs mapping to 12 BMI-associated loci which have been extensively replicated across different ethnicities, i.e., BDNF, FAIM2, ETV5, FTO, GNPDA2, KCTD15, MC4R, MTCH2, NEGR1, SEC16B, SH2B1, and TMEM18, were studied in association with PCOS within each cohort using the additive genetic model followed by a combined analysis. A genetic allelic count risk score model was used to determine the risk of PCOS for individuals carrying increasing numbers of BMI-increasing alleles.

Results

None of the genetic variants, including FTO and MC4R, was associated with PCOS independently of BMI in the meta-analysis. Moreover, no differences were observed between cases and controls in the number of BMI-risk alleles present and no overall trend across the risk score groups was observed.

Conclusion

In this combined analysis of over 4,000 BMI-matched individuals from the United Kingdom and the Netherlands, we observed no association of BMI risk alleles with PCOS independent of BMI.

Association between fat mass- and obesity-associated (FTO) gene polymorphism and polycystic ovary syndrome: a meta-analysis

Aims

Many studies have investigated the relationship between FTO gene polymorphism and polycystic ovary syndrome (PCOS) susceptibility but revealed mixed results. In this study, we aimed to perform a meta-analysis to clarify this association.

Methods

Published literature from PubMed, Embase and CNKI was retrieved. Meta-analysis was performed to calculate pooled odds ratio (OR) with 95% confidence interval (CI) using the random- or fix- effects model.

Results

A total of 5 studies (4778 cases and 4272 controls) were included in our meta-analysis. The results suggested that FTO rs9939609 polymorphism (or its proxy) was marginally associated with PCOS risk after adjustment for body mass index (BMI) (OR = 1.26; 95%CI: 1.02–1.55). However, the marginal association was not stable after sensitivity analysis. In the subgroup analysis by ethnicity, the association was significant in East Asians (OR = 1.43, 95%CI = 1.30–1.59) but not in Caucasians (OR = 1.04, 95%CI = 0.85–1.29).

Conclusions

Our present meta-analysis indicated that FTO rs9939609 polymorphism (or its proxy) might not be associated with risk of PCOS in overall population. However, in East Asians, there might be a direct association between FTO variant and PCOS risk, which is independent of BMI (adiposity).

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.

Impact of FTO genotypes on BMI and weight in polycystic ovary syndrome: a systematic review and meta-analysis

AIMS/HYPOTHESIS

FTO gene single nucleotide polymorphisms (SNPs) have been shown to be associated with obesity-related traits and type 2 diabetes. Several small studies have suggested a greater than expected effect of the FTO rs9939609 SNP on weight in polycystic ovary syndrome (PCOS). We therefore aimed to examine the impact of FTO genotype on BMI and weight in PCOS.

METHODS

A systematic search of medical databases (PubMed, EMBASE and Cochrane CENTRAL) was conducted up to the end of April 2011. Seven studies describing eight distinct PCOS cohorts were retrieved; seven were genotyped for SNP rs9939609 and one for SNP rs1421085. The per allele effect on BMI and body weight increase was calculated and subjected to meta-analysis.

RESULTS

A total of 2,548 women with PCOS were included in the study; 762 were TT homozygotes, 1,253 had an AT/CT genotype, and 533 were AA/CC homozygotes. Each additional copy of the effect allele (A/C) increased the BMI by a mean of 0.19 z score units (95% CI 0.13, 0.24; p = 2.26 × 10(-11)) and body weight by a mean of 0.20 z score units (95% CI 0.14, 0.26; p = 1.02 × 10(-10)). This translated into an approximately 3.3 kg/m(2) increase in BMI and an approximately 9.6 kg gain in body weight between TT and AA/CC homozygotes. The association between FTO genotypes and BMI was stronger in the cohorts with PCOS than in the general female populations from large genome-wide association studies. Deviation from an additive genetic model was observed in heavier populations.

CONCLUSIONS/INTERPRETATION

The effect of FTO SNPs on obesity-related traits in PCOS seems to be more than two times greater than the effect found in large population-based studies. This suggests an interaction between FTO and the metabolic context or polygenic background of 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.

Impact of the FTO gene variation on fat oxidation and its potential influence on body weight in women with polycystic ovary syndrome

CONTEXT

Polycystic ovary syndrome (PCOS) is a heterogeneous disorder where insulin resistance might be involved in the development of endocrine and metabolic abnormalities. It has recently been shown that the FTO gene modifies weight, fat mass and insulin sensitivity in women with PCOS, where its role might be larger than in other phenotypes.

OBJECTIVE

The aim of this study was to estimate the effect of a variation of the FTO gene on carbohydrate and lipid oxidation in PCOS women.

PATIENTS

The study group consisted of 65 women with PCOS and 28 healthy, normally menstruating women.

MEASUREMENTS

Clinical examination, anthropometric measurements, euglycaemic hyperinsulinaemic clamp and measurements of serum sex hormones were performed. Carbohydrate and lipid oxidation were evaluated with indirect calorimetry in the baseline state and during last 30 min of the clamp. The FTO rs9939609 polymorphism was genotyped using the restriction fragment length polymorphism method.

RESULTS

There were no differences in carbohydrate and lipid oxidation between PCOS and control women. In the PCOS group, TT homozygotes had higher baseline fat oxidation in comparison with carriers of the A allele (P = 0·018), which was not found in the control group. We did not observe the effect of the FTO gene variation on insulin-stimulated lipid oxidation and neither on the baseline nor on the insulin-stimulated carbohydrate oxidation.

CONCLUSION

Our data show that this FTO gene variation might influence the baseline lipid oxidation in PCOS patients. This might potentially be one of the mechanisms explaining the impact of the FTO gene on body weight 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.

Molecular mechanistic associations of human diseases

Background

The study of relationships between human diseases provides new possibilities for biomedical research. Recent achievements on human genetic diseases have stimulated interest to derive methods to identify disease associations in order to gain further insight into the network of human diseases and to predict disease genes.

Results

Using about 10000 manually collected causal disease/gene associations, we developed a statistical approach to infer meaningful associations between human morbidities. The derived method clustered cardiometabolic and endocrine disorders, immune system-related diseases, solid tissue neoplasms and neurodegenerative pathologies into prominent disease groups. Analysis of biological functions confirmed characteristic features of corresponding disease clusters. Inference of disease associations was further employed as a starting point for prediction of disease genes. Efforts were made to underpin the validity of results by relevant literature evidence. Interestingly, many inferred disease relationships correspond to known clinical associations and comorbidities, and several predicted disease genes were subjects of therapeutic target research.

Conclusions

Causal molecular mechanisms present a unifying principle to derive methods for disease classification, analysis of clinical disorder associations, and prediction of disease genes. According to the definition of causal disease genes applied in this study, these results are not restricted to genetic disease/gene relationships. This may be particularly useful for the study of long-term or chronic illnesses, where pathological derangement due to environmental or as part of sequel conditions is of importance and may not be fully explained by genetic background.

Large effects on body mass index and insulin resistance of fat mass and obesity associated gene (FTO) variants in patients with polycystic ovary syndrome (PCOS)

Background

The polycystic ovary syndrome (PCOS), a common endocrine disorder in women of child-bearing age, mainly characterised by chronic anovulation and hyperandrogenism, is often associated with insulin resistance (IR) and obesity. Its etiology and the role of IR and obesity in PCOS are not fully understood. We examined the influence of validated genetic variants conferring susceptibility to obesity and/or type 2 diabetes mellitus (T2DM) on metabolic and PCOS-specific traits in patients with PCOS.

Methods

We conducted an association study in 386 patients with PCOS (defined by the Rotterdam-criteria) using single nucleotide polymorphisms (SNPs) in or in proximity to the fat mass and obesity associated gene (FTO), insulin-induced gene-2 (INSIG2), transcription factor 7-like 2 gene (TCF7L2) and melanocortin 4 receptor gene (MC4R). To compare the effect of FTO obesity risk alleles on BMI in patients with PCOS to unselected females of the same age range we genotyped 1,971 females from the population-based KORA-S4 study (Kooperative Gesundheitsforschung im Raum Augsburg, Survey 4).

Results

The FTO risk allele was associated with IR traits and measures of increased body weight. In addition, the TCF7L2 SNP was associated with body weight traits. For the SNPs in the vicinity of INSIG2 and MC4R and for the other examined phenotypes there was no evidence for an association. In PCOS the observed per risk allele effect of FTO intron 1 SNP rs9939609 on BMI was +1.56 kg/m², whereas it was +0.46 kg/m² in females of the same age range from the general population as shown previously.

Conclusion

The stronger effect on body weight of the FTO SNP in PCOS might well have implications for the etiology of the disease.