Sex-specific associations of TCF7L2 variants with fasting glucose, type 2 diabetes and coronary heart disease among Turkish adults.

OBJECTIVE: TCF7L2 is a repressor and transactivator of genes, and its variants are strongly associated with diabetes. This study aimed to evaluate the sex-specific relationship between the most common TCF7L2 gene variants (-98368G>T, rs12255372 and -47833C>T, rs7903146) with diabetes and coronary heart disease in Turkish Adult Risk Factor (TARF) Study. METHODS: Single nucleotide variants (SNVs) have been genotyped using the TaqMan allelic discrimination assays in 2,024 (51.3% in women, age: 55±11.8) Turkish adults participating in the TARF study. Statistical analyses were used to investigate the association of genotypes with clinical and biochemical measurements. RESULTS: Among the TARF study participants, 11.7%, 24.3%, 14.1%, and 38.3% had diabetes, hypertension, coronary heart disease (CHD), and obesity, respectively. The frequencies of T allele for -47833C>T and -98368G>T in Turkish adults were determined to be 0.35 and 0.33, respectively. -47833C>T was significantly associated with higher fasting glucose concentrations in all participants, especially in men. Both SNVs were significantly associated with diabetes and CHD in all participants (p<0.05). When study population was stratified according to sex, -98368G>T was associated with diabetes in women (p=0.041) and -47833C>T was associated with diabetes and CHD in men (p=0.018 and p=0.032, respectively). Also, both SNVs and the diplotypes of common haplotype (H1) remained strongly associated with type 2 diabetes after risk factors were adjusted (p<0.05). CONCLUSION: T allele homozygosity of two SNVs as well as the diplotype H1-/H1- reflects risk of diabetes primarily in men. Enhanced CHD risk is determined by the presence of diplotype H1-/H1- among nondiabetic participants.

Risk of obesity and metabolic syndrome associated with FTO gene variants discloses clinically relevant gender difference among Turks.

Gene variations in the fat mass- and obesity-associated gene (FTO) have shown controversial associations with obesity and metabolic syndrome (MetS) in several populations. We explored the association of FTO gene with obesity, MetS, and insulin-related parameters separately in men and women. Two SNPs in the FTO, gene rs9939609 and rs1421085, were genotyped by the Taqman System in 1967 adults (mean age of the whole group 50.1 ± 12.0; 48.4 % male). A random sample of the Turkish Adult Risk Factor cohort was cross-sectionally analyzed. Both SNPs exhibited strong linkage disequilibrium (r(2) = 0.85) and minor alleles were associated with risk of obesity in women and of MetS in men. Carriers of the rs1421085 C-allele exhibited higher body mass index (BMI) in each gender. Adjusted fasting insulin and HOMA index were significantly higher in C-allele carriers in men alone. Logistic regression analysis demonstrated significantly increased likelihood for obesity in female C-risk allele carriers (OR 1.61; 95 % CI 1.19-2.18), after adjustment for age, smoking status, alcohol usage, physical activity grade and presence of diabetes mellitus. Male C-allele carriers were at increased risk for MetS (OR 1.44; 95 % CI 1.07-1.95), adjusted for age, smoking status, alcohol consumption, and physical activity. Further adjustment for BMI attenuated the MetS risk, indicating interaction between C-allele, gender and BMI. The FTO gene in Turkish adults contributes independently to obesity in women and-by interacting with BMI-to MetS and insulin resistance in men.