Several lines of evidence indicate a causal role of the cytokine interleukin (IL)-6 in the development of type 2 diabetes in humans. Two common polymorphisms in the promoter of the IL-6 encoding gene IL6, ؊174G>C(rs1800795) and ؊573G>C (rs1800796), have been investigated for association with type 2 diabetes in numerous studies but with results that have been largely equivocal. To clarify the relationship between the two IL6 variants and type 2 diabetes, we analyzed individual data on >20,000 participants from 21 published and unpublished studies. Collected data represent eight different countries, making this the largest association analysis for type 2 diabetes reported to date. The GC and CC genotypes of IL6 ؊174G>C were associated with a decreased risk of type 2 diabetes (odds ratio 0.91, P ‫؍‬ 0.037), corresponding to a risk modification of nearly 9%. No evidence for association was found between IL6 ؊573G>C and type 2 diabetes. The observed association of the IL6 ؊174 C-allele with a reduced risk of type 2 diabetes provides further evidence for the hypothesis that immune mediators are causally related to type 2 diabetes; however, because the association is borderline significant, additional data are still needed to confirm this finding. Diabetes 55:2915-2921, 2006

Our data provide evidence that the IL-6-174G/C polymorphism may be involved in the pathogenesis of coronary artery disease, contributing to genetic susceptibility for myocardial infarction.

Abundant evidence suggests that cytokines involve in the pathogenesis of latent autoimmune diabetes of adults (LADA). This is a slowly progressive form of type 1 diabetes, which is initially diagnosed as type 2 diabetes. In this study, healthy individuals LADA and type 2 diabetic patients were genotyped for IL-6-174G/C, TNF-alpha-308A/G, TGF-beta1-codon10T/C, TGF-beta1-codon25G/C, IL-10-1082A/G, IL-10-819T/C, IL-10-592A/C gene polymorphisms, by sequence-specific-primer polymerase chain reaction methodology. A significant difference in the frequencies of -1082A/G IL-10 alleles was observed, with the -1082*A allele (known to be associated with low IL-10 production), predominating in LADA diabetics than type 2 diabetics (p=0.036). No significant differences of genotypes, phenotypes, or haplotype frequencies in the remaining cytokine polymorphisms were observed. Analysis of allele combinations revealed a significant involvement of the low and high in vitro production IL-10 alleles in the development of LADA and type 2 diabetes, respectively. These results suggest that the G/A mutation at position -1082 of IL-10 promoter gene region might be one of the factors participating to the pathogenesis of LADA diabetes and that identification of cytokine gene polymorphisms might contribute to the characterization of the different types of diabetes mellitus.

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The novel adipokine chemerin has been related to insulin-resistant states such as obesity and non alcoholic fatty liver disease (NAFLD). However, its association with insulin resistance and beta cell function remains controversial. The main objective was to examine whether serum chemerin levels associate with insulin sensitivity and beta cell function independently of body mass index (BMI), by studying consecutive outpatients of the hepatology clinics of a European university hospital. Individuals (n=196) with NAFLD were stratified into persons with normal glucose tolerance (NGT; n=110), impaired glucose tolerance (IGT; n=51) and type 2 diabetes (T2D; n=35) and the association between serum chemerin and measures of insulin sensitivity and beta cell function as assessed during fasting and during oral glucose tolerance test (OGTT) was measured. Our results showed that serum chemerin positively associated with BMI (P=0.0007) and C peptide during OGTT (P<0.004), but not with circulating glucose, insulin, lipids or liver enzymes (all P>0.18). No BMI independent relationships of chemerin with fasting and OGTT derived measures of insulin sensitivity were found (P>0.5). Chemerin associated positively with fasting beta cell function as well as the OGTT derived insulinogenic index IGI_cp and the adaptation index after adjustment for age, sex and BMI (P=0.002-0.007), and inversely with the insulin/C peptide ratio (P=0.007). Serum chemerin neither related to the insulinogenic index IGI_ins nor the disposition index. In conclusion, circulating chemerin is likely linked to enhanced beta cell function but not to insulin sensitivity in patients with NAFLD.