Type 2 diabetes is associated with the MTNR1B gene, a genetic bridge between circadian rhythm and glucose metabolism, in a Turkish population.

Type 2 diabetes (T2D) is a complicated public health problem in Turkey as well as worldwide. Genome-wide approaches have been guiding in very challenging situations, such as the elucidation of genetic variations underlying complex diseases such as T2D. Despite intensive studies worldwide, few studies have determined the genetic susceptibility to T2D in Turkish populations. In this study, we investigated the effect of genes that are strongly associated with T2D in genome-wide association (GWA) studies, including MTNR1B, CDKAL1, THADA, ADAMTS9 and ENPP1, on T2D and its characteristic traits in a Turkish population. In 824 nonobese individuals (454 T2D patients and 370 healthy individuals), prominent variants of these GWA genes were genotyped by real-time PCR using the LightSNiP Genotyping Assay System. The SNP rs1387153 C/T, which is located 28 kb upstream of the MTNR1B gene, was significantly associated with T2D and fasting blood glucose levels (P < 0.05). The intronic SNP rs10830963 C/G in the MTNR1B gene was not associated with T2D, but it was associated with fasting blood glucose, HbA1C and LDL levels (P < 0.05). The other important GWA loci investigated in our study were not found to be associated with T2D or its traits. Only the SNP rs1044498 (A/C variation) in the ENPP1 gene was determined to be related to fasting blood glucose (P < 0.05). Our study suggests, consistent with the literature, that the MTNR1B locus, which has a prominent role in glucose regulation, is associated with T2D development by affecting blood glucose levels in our population.

PIK3R1 gene polymorphisms are associated with type 2 diabetes and related features in the Turkish population.

BACKGROUND: The phosphatidylinositol 3-kinase p85 alpha regulatory subunit 1 gene (PIK3R1) encodes the PIK3R1 protein, which plays a direct role in insulin signaling. PIK3R1 (p85 regulatory subunit) connects firmly with the p110 catalytic subunit, and together these proteins form the phosphatidylinositol 3-kinase (PI3K) protein. PI3K is a key protein in the Akt signaling pathway, which regulates cell survival, growth, differentiation, glucose trafficking, and utilization. Defects in the insulin signaling cascade play an important role in the development of insulin resistance, which shares a common genetic basis for metabolic diseases such as type 2 diabetes (T2D), obesity and cardiovascular diseases. OBJECTIVES: In our study, we investigated the effect of single nucleotide polymorphisms (SNPs) rs3756668 in 3'UTR region, rs706713 and rs3730089 in exons 1 and 6, respectively, rs7713645 and rs7709243 in intron 1, and rs1550805 in intron 6 of PIK3R1 gene on T2D. MATERIAL AND METHODS: This study enrolled a total of 840 individuals, including 427 diabetic individuals (206 obese and 221 non-obese) and 413 nondiabetic individuals (138 obese and 275 non-obese). The target SNPs were analyzed using real-time polymerase chain reaction (RT-PCR). Statistical analysis was performed using SPSS18.0 (IBM Corp., Armonk, USA). The p-values ≤0.05 were considered statistically significant. RESULTS: The SNPs rs706713 (Tyr73Tyr) and rs3730089 (Met326Ile) located in exons, and rs7713645, rs7709243 and rs1550805 located in introns were determined to be significantly associated with T2D and phenotypic features such as obesity, insulin resistance and the lipid parameters. The association with SNP rs3756668, which is located in the 3'UTR, was not significant. CONCLUSIONS: Our study supports the role of PIK3R1, an important candidate gene due to its critical role in insulin signal transduction, in T2D development.