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

FTO: a critical role in obesity and obesity-related diseases

In recent years, obesity is a growing pandemic in the world and has likely contributed to increasing the incidence of obesity-related diseases. Fat mass and obesity-associated gene (FTO) is the first gene discovered which has a close connection with fat. Recent studies suggested that FTO gene has played an important role in the molecular mechanisms of many diseases. Obesity is considered to be a hereditary disease and can evoke many kinds of diseases, including polycystic ovary syndrome (PCOS), type 2 diabetes mellitus (T2DM), cancer, etc., whose exact possible molecular mechanisms responsible for the effect of FTO on obesity and obesity-related diseases remain largely unknown. In this review, we comprehensively discuss the correlation between FTO gene and obesity, cancer, PCOS, T2DM, as well as the molecular mechanism involved in these diseases.

Differential Association of FTO Gene variants and Haplotypes with the Susceptibility to Polycystic Ovary Syndrome According To Obesity in Women with PCOS

We explored the relation between FTO single gene variants (rs1861868, rs9939973, rs1421085, rs1121980, rs17817449, rs8050136, rs9939609, rs9930506, and rs8044769) and polycystic ovary syndrome (PCOS), in particular, according to the obesity status. This retrospective population-based case-control study involved women with PCOS (583) and 713 eumenorrheic control women; genotyping was done by real-time PCR. Significantly higher minor allele frequency (MAF) of rs9939973, rs17817449, rs9939609, and rs9930506 and lower MAF of rs1121980 were seen in PCOS cases. Lower risk of PCOS was associated with rs1121980 and rs8050136 heterozygous and minor allele-homozygous genotypes, while an elevated risk of PCOS was seen with minor allele-homozygous rs9939973, rs17817449, and r9939609 heterozygous and genotypes and minor allele-homozygous rs9930506 and rs8044769 genotype. While none of the tested FTO SNPs variants was associated with PCOS in normal body weight/lean subjects, rs9939973, rs9939609, and rs9930506 were negatively associated with PCOS in overweight subjects. In comparison, rs1861868 was negatively, while rs8044769 was positively associated with PCOS in obese subjects. Haplotype analysis identified haplotypes GACCTCTAT, AACCTCTAT, AACCTATAT and AGTTGCAGC, and GACCTCTAC to be positively associated with PCOS, while haplotypes GGTTGAAGC, GACCTATAT, GGTTGCAGC, and GATCTATAT were negatively associated with PCOS. Apart from GGTTGAAGC, these haplotypes remained associated with altered risk of PCOS after adjusting for covariates. In addition to rs17817449, rs9939609, rs9930506, and rs1121980, this study is the first to demonstrate association of rs9939973 and rs8044769 with altered risk of PCOS and the first to confirm the BMI dependency on the association of FTO variants with PCOS. This underscores the role of FTO gene variants as predisposing factors of PCOS.

Risk variants of obesity associated genes demonstrate BMI raising effect in a large cohort

Obesity is highly polygenic disease where several genetic variants have been reportedly associated with obesity in different ethnicities of the world. In the current study, we identified the obesity risk or protective association and BMI raising effect of the minor allele of adiponectin, C1Q and collagen domain containing (ADIPOQ), cholesteryl ester transfer protein (CEPT), FTO alpha-ketoglutarate dependent dioxygenase (FTO), leptin (LEP), and leptin receptor (LEPR) genes in a large cohort stratified into four BMI-based body weight categories i.e., normal weight, lean, over-weight, and obese. Based on selected candidate genetic markers, the genotyping of all study subjects was performed by PCR assays, and genotypes and allele frequencies were calculated. The minor allele frequencies (MAFs) of all genetic markers were computed for total and BMI-based body weight categories and compared with MAFs of global and South Asian (SAS) populations. Genetic associations of variants with obesity risk were calculated and BMI raising effect per copy of the minor allele were estimated. The genetic variants with higher MAFs in obese BMI group were; rs2241766 (G = 0.43), rs17817449 (G = 0.54), rs9939609 (A = 0.51), rs1421085 (C = 0.53), rs1558902 (A = 0.63), and rs1137101 (G = 0.64) respectively. All these variants were significantly associated with obesity (OR = 1.03–4.42) and showed a high BMI raising effect (β = 0.239–0.31 Kg/m²) per copy of the risk allele. In contrast, the MAFs of three variants were higher in lean-normal BMI groups; rs3764261 A = 0.38, rs9941349 T = 0.43, and rs7799039 G = 0.40–0.43). These variants showed obesity protective associations (OR = 0.68–0.76), and a BMI lowering effect per copy of the protective allele (β = -0.103–0.155 Kg/m²). The rs3764261 variant also showed significant and positive association with lean body mass (OR = 2.38, CI = 1.30–4.34). Overall, we report six genetic variants of ADIPOQ, FTO and LEPR genes as obesity-risk markers and a CETP gene variant as lean mass/obesity protective marker in studied Pakistani cohort.

Associations of the KiSS-1 and GPR54 genetic polymorphism with polycystic ovary syndrome in Yunnan, China

BSCKGROUND

Polycystic ovary syndrome (PCOS) is a heterogeneous condition that increases the risk for serious health complications among women. Thus, in this study, we aimed to identify polymorphisms in the KiSS-1 and GPR54 genes and investigate the associations between KiSS-1, BMI, FSH, LH, and estradiol in Chinese women with PCOS.

METHODS

This study recruited women with PCOS (n = 60) and controls (n = 60). We collected blood samples and measured endocrine indicators (kisspeptin, FSH, LH-FSH ratio, estradiol, prolactin, and testosterone). PCR and Snapshots were performed to screen single nucleotide polymorphisms (SNPs) of the KiSS-1 and GPR54 genes.

RESULTS

Compared with the controls, endocrine and metabolic disturbances in women with PCOS were reflected in significantly higher levels of BMI, LH, LH-FSH ratio, prolactin, and testosterone. Serum kisspeptin levels were significantly higher and positively correlated with LH and T levels (p < 0.05). No identified SNPs of KiSS-1 and GPR54 showed significant differences in frequency between patients and controls. The mutant G allele was highly predisposed to polymorphism in the PCOS GPR54 gene r10407968. We observed a significant difference in estradiol (p = 0.023, p = 0.012) after comparing the values of LH, FSH, estradiol, progesterone, and testosterone among the three genotypes of rs4889 and rs5780218. The KiSS-1 rs4889 CC genotype and rs5780218 AA genotype showed significantly higher estradiol levels compared with the other two genotypes.

CONCLUSIONS

These results suggest that kisspeptin plays a potential role in the etiology of PCOS.

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.

Fat mass and obesity-associated gene expression and disease severity in type 2 diabetes mellitus

Obesity and visceral adiposity are major risk factors for type 2 diabetes mellitus (T2DM). The fat mass and obesity-associated (FTO) gene is associated with increased risk of obesity and T2DM. The aim of this work was to study the association between FTO gene expression and serum FTO protein level with disease severity in T2DM patients.

PATIENTS AND METHODS

One hundred T2DM patients were divided into two equal groups according to diabetes control and complications and fifty healthy controls were included in this study. FTO messenger ribonucleic acid (mRNA) expression level was analyzed by Real time polymerase chain reaction (PCR) technique and serum level of FTO protein was measured by ELISA.

RESULTS

FTO gene expression and FTO protein levels were increased in the two T2DM groups compared to the control group with significant further increases in patients with severe disease. FTO gene expression and FTO protein levels were positively correlated with obesity, insulin resistance and blood glucose indices as well as the presence of diabetic complications. Regression analyses showed that FTO gene expression and FTO protein levels were risk factors for T2DM severity.

CONCLUSIONS

Increased FTO gene expression and its serum protein levels are associated with increased T2DM severity.