Gestational diabetes mellitus (GDM) is carbohydrate intolerance in pregnant women leading to various complications. Currently, there is a search for factors predisposing to GDM. Among them are genetic polymorphisms of genes involved in insulin secretion as well as carbohydrate metabolism. Due to the similar pathogenesis of GDM to type 2 diabetes (T2DM), genetic polymorphisms associated with T2DM are considered. The aim of this study was to examine the associations between the COBLL1 rs7607980 T > C and IRS1 rs2943641 T > C gene polymorphisms and the risk of GDM as well as selected clinical parameters in women with GDM. Additionally, we examined the expression of these genes in the placenta of women with and without GDM in correlation with selected clinical parameters. This study included 328 pregnant women with normal glucose tolerance (NGT) and 251 pregnant women with GDM diagnosed on the basis of a 75 g oral glucose tolerance test (OGTT) at 24−28 weeks gestation. There were no statistically significant differences in the distribution of IRS1 rs2943641 gene polymorphisms between women with GDM and pregnant women with NGT. In the GDM group, we observed a decreased frequency of COBLL1 rs7607980 CC homozygous women (CC vs. TC+TT, p = 0.048); however, there was no statistically significant difference in the frequency of alleles between women with GDM and the control group. There were no statistically significant associations between COBLL1 rs7607980 gene polymorphism and clinical parameters in women with GDM. In GDM women with the IRS1 rs2943641 TT genotype, fasting glucose levels were significantly higher than in women with CC and TC genotypes. There was no statistically significant difference in the expression of COBLL1 and IRS1 genes in the placenta between women with GDM and healthy women. There were no statistically significant correlations between COBLL1 gene expression in the placenta and clinical parameters. The expression of IRS1 correlated significantly with an increase in BMI during pregnancy. The results of this study suggest that COBLL1 rs7607980 and IRS1 rs2943641 gene polymorphisms are not significant risk factors for GDM in our population. The IRS1 TT genotype may be associated with higher fasting glucose levels in women with GDM. Expression of the IRS1 gene in the placenta positively correlates with an increase in BMI during pregnancy in women with GDM.
Keywords: COBLL1; IRS1; gestational diabetes; polymorphism.