Association of a functional 17β-estradiol sensitive IL6-174G/C promoter polymorphism with early-onset type 1 diabetes in females

The type 1 diabetes mellitus (T1DM) candidate gene SNP IL6-174G/C was genotyped in 253 Danish T1DM families (1129 individuals). TDT analysis demonstrated linkage in the presence of association between the IL6-174C allele and T1DM in the 416 T1DM offspring, P-tdt = 0.04. Gender conditioned TDT analyses revealed that linkage and association with T1DM were present in females exclusively; P-tdt = 6.5 x 10(-4) and P-tdt = 2.4 x 10(-4), respectively. Random transmission of the IL6-174C/G alleles was found in T1DM males, non-T1DM males and non-T1DM females; all P-tdt greater than or equal to 0.37. Heterogeneity analyses (T1DM versus non-T1DM females) excluded preferential meiotic segregation in females, P = 4.6 x 10(-3), and demonstrated differences in the transmission patterns between female and male T1DM offspring, P = 5.1 x 10(-3). The IL6-174 CC genotype was associated with younger age at onset of T1DM in females (P = 0.002). The impact of 17beta-estradiol (E-2) on the IL6-174G/C variants was investigated by reporter studies. The PMA stimulated activity of the T1DM risk IL6-174C variant exceeded that of the T1DM protective IL6-174G variant by similar to70% in the absence of E-2 (P-c = 0.004), but not with E-2 present (P-c = 0.12). The PMA stimulated activity of the IL6-174G variant was repressed without E-2 present, but was derepressed by addition of E-2, P-c = 0.024. In contrast, the PMA stimulated IL6-174C activity was unaffected by E-2 as were the constitutive activities of the IL6-174G/C variants. In conclusion, higher IL6 promoter activity may confer risk to T1DM in very young females. This excess risk is negated with increasing age, possibly by the increasing E-2 levels in puberty.