Relationship of Insulin Gene (SNP rs3842752G>A), TCF7L2 Gene (SNP rs12255372 G>T), and SLC30A8 Gene (SNP rs13266634T>C) with Serum Insulin Level in Type II Diabetic Patients in Iraq

Abstract Background: Type II diabetes is a health challenge all over the world, with both environmental and genetic factors involved in its occurrence. Moreover, its genetic factors have diversity among population groups and races in the world. Objectives: Our study aims to find the association of SNPs(rs3842752G>A- Insulin Gene, rs12255372 G>T- TCF7L2 Gene, and rs13266634T>C- SLC30A8 Gene), with type II diabetes mellitus and with serum insulin levels in patients with type II diabetes in Iraq. Materials and Methods: In total, 88 individuals (34 nondiabetics and 54 type 2 diabetics millets) participated from Baghdad. Insulin concentration was measured using an enzyme-linked immunoassay. The genotype of the SNP rs3842752 in the insulin gene was analyzed using the RFLP technique. While the genotypes of SNP rs12255372 in the TCF7L2 gene and the SNP rs13266634 in the SLC30A8 gene were analyzed using the SSCP-genotyping technique. Sequence analysis was performed by Macrogen Inc., South Korea. Results: The results of the current study showed that there was a significant difference ( P < 0.05) for insulin concentrations between the T2DM group and the ND group. In addition, the results of the genetic analysis showed the presence of alleles (G and A) in rs3842752, (C and T) in rs13266634 and in rs12255372 were (G and A), which indicated the presence of the allele (A) in Iraqis as a substitute for the allele (T), which was related to type II diabetes in many studies in the world. On the other hand, the results of the Hardy-Weinberg equilibrium test showed that there was a high significant difference ( P <0.0001) between the frequency of the (C and T) alleles in the SLC30A8 gene, which may indicate the functional role of the (C) allele in susceptibility to type II diabetes in Iraqis. However, no significant differences were seen between the distributions of alleles and genotypes as they did not indicate the relationship with type II diabetes, and no significant difference was seen in insulin concentrations between carriers of genotypes at the three single nucleotide polymorphisms in the current study. Conclusions: We concluded from the results of the current study that the single nucleotide polymorphism rs3842752, which did not appear to be related to type II diabetes and had no effect on insulin levels in Iraqis, may have a different functional role that may need more research to determine it. Moreover, Previous studies around the world showed that single nucleotide polymorphisms (SNPs rs13266634 and rs12255372) are related to type II diabetes and have an effect on insulin levels, but the failure to show the same results in the current study may be, due to the small size of the studied sample, in addition, the single nucleotide polymorphisms in the current study may have a different functional role in the Iraqis. However, the current results need other studies with a larger number of participants, perhaps from other Iraqi provinces, to interpret and support the current results.