Genetic determinants of circulating interleukin-1 receptor antagonist levels and their association with glycemic traits.
The proinflammatory cytokine interleukin (IL)-1beta is implicated in the development of insulin resistance and beta-cell dysfunction, whereas higher circulating levels of IL-1 receptor antagonist (IL-1RA), an endogenous inhibitor of IL-1beta, has been suggested to improve glycemia and beta-cell function in patients with type 2 diabetes. To elucidate the protective role of IL-1RA, this study aimed to identify genetic determinants of circulating IL-1RA concentration and to investigate their associations with immunological and metabolic variables related to cardiometabolic risk. In the analysis of seven discovery and four replication cohort studies, two single nucleotide polymorphisms (SNPs) were independently associated with circulating IL-1RA concentration (rs4251961 at the IL1RN locus [n = 13,955, P = 2.76 x 10(-21)] and rs6759676, closest gene locus IL1F10 [n = 13,994, P = 1.73 x 10(-17)]). The proportion of the variance in IL-1RA explained by both SNPs combined was 2.0%. IL-1RA-raising alleles of both SNPs were associated with lower circulating C-reactive protein concentration. The IL-1RA-raising allele of rs6759676 was also associated with lower fasting insulin levels and lower HOMA insulin resistance. In conclusion, we show that circulating IL-1RA levels are predicted by two independent SNPs at the IL1RN and IL1F10 loci and that genetically raised IL-1RA may be protective against the development of insulin resistance.