Interleukin-6 genotypes and serum levels in Chinese Hui population

Interleukin-6 (IL-6) is a key pro-inflammatory cytokine involved in different physiologic and pathophysiologic processes, and circulating levels of IL-6 differ greatly between individuals. The Chinese Hui is one of the largest ethnic minorities, little is known about the distribution of IL-6 genetic variations and their effects on serum levels in Hui population. The aim of the present study is to determine the prevalence of -174G/C (rs1800795), -597G/A (rs1800797), and -634C/G (rs1800796) polymorphisms in the IL-6 gene promoter region and their association with IL-6 serum levels in the Ningxia Hui population. A total of 96 Hui subjects, (57 men and 39 women; mean age 49.65 ± 19.73 years) unrelated nationality residents in Ningxia Hui Autonomous Region were enrolled. Genotyping of the three polymorphisms were performed by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) combined with gel electrophoresis and then confirmed by direct sequencing. The -174G/C (97.92% GG, 2.08% GC, and 0% CC) and -597G/A (98.96% GG, 1.04% GA, and 0% AA) polymorphisms were rare. The frequencies of -634C/G genotypes CC, CG, and GG were found to be 54.17%, 40.62%, and 5.21%, respectively in total studied subjects, the derived allele frequencies for the C and G alleles were 74.48% and 25.52%. Increased IL-6 levels were correlated with the IL-6 -634G allele carriers (CG+GG genotypes). The results suggest that IL-6 -174G/C and -597G/A are rare but -634C/G is common in the Ningxia Hui population, and the -634G allele is associated with circulating levels of IL-6.