Association of +3179G/A insulin-like growth factor-1 receptor polymorphism and insulin-like growth factor-1 serum level with systemic lupus erythematosus.

The insulin-like growth factor (IGF) system plays a prominent role in the regulation of immunity and inflammation. Inappropriate balance of IGF-1 signaling has been reported in autoimmune disorders. This study was designed to compare +3179G/A IGF-1R genotype distribution in 148 systemic lupus erythematosus (SLE) patients with a group of 240 healthy donors. We also investigated serum IGF-1 levels in SLE patients and healthy controls in an association to genotype. IGF-1 serum levels were measured by enzyme-linked immunosorbent assay and genotyping for the +3179G/A polymorphism was performed by restriction fragment length polymorphisms (RFLP)-polymerase chain reaction (PCR) assay. The higher frequency of homozygous genotype AA (22% vs. 17% with OR 1.319, 95% CI 0.71--2.44) and lower frequency of heterozygous genotype AG (42% vs. 46% with OR 0.698, 95% CI 0.38-1.27) were seen in cases versus controls. Serum IGF-1 levels were comparable between SLE patients and age- and sex-matched healthy donors, even when the groups was stratified according to +3179G/A IGF-1R genotypes. However, when patients were sub grouped according to the disease activity index (SLEDAI score), serum IGF-1 levels were increased in patients with severe disease activity. These results indicated that systemic lupus erythematosus activity is affected by a modulation of the insulin-like growth factor-1 signal pathway and +3179G/A IGF-1R polymorphism.