Association of IL-18 genotype with impaired glucose regulation in Korean women with polycystic ovary syndrome

Abstract

Polycystic ovary syndrome (PCOS) is a common endocrine disorder among women of reproductive age. The pro-inflammatory cytokine, interleukin (IL)-18, is associated with metabolic syndrome, and elevated serum IL-18 levels are related to obesity and insulin resistance in PCOS patients. However, the role of IL-18 in the PCOS remains unclear. So we examined whether or not two functional polymorphisms in the IL-18 gene, -137G>C and +183A>G, are associated with PCOS itself or glucose intolerance in Korean women with PCOS. The IL-18 genotypes of 126 women with PCOS and 113 controls were determined and their serum levels of lipid and hormone profiles measured. The insulin resistance index was calculated from the glucose and insulin concentrations obtained by oral glucose tolerance tests. There were no statistically significant differences in the distribution of -137 G>C polymorphisms among the women classified according to presence or absence of PCOS and obesity. However, the -137G/G allele was more frequent in the PCOS+impaired glucose regulation (IGR) group than PCOS+normal glucose tolerance group (X(2)=7.637, p(Bonf)=0.022). The PCOS group with only the -137G allele had a significantly increased risk of IGR compared to the PCOS group with the -137C allele (92 vs. 8%, odds ratio=6.325, 95% confidence interval=1.403-28.519). In the PCOS patients, the mean fasting and 2-h post-prandial plasma glucose level of patients with only the -137G allele was significantly higher than those of the patients with the -137C allele (88.87 ± 9.49 vs. 84.37 ± 6.19, p=0.002 and 120.07 ± 34.53 vs. 107.54 ± 27.13, p=0.038). Only one woman was heterozygous for the +183A>G polymorphism and the other 224 subjects were homozygous for the polymorphism (A/A). The IL-18 -137G allele could play a role in the predisposition to glucose intolerance in Korean women with PCOS, and the +183G allele of IL-18 is not associated with the Korean population.