Association of interleukin-6 gene G-174C polymorphism and plasma plasminogen activator inhibitor-1 level in Chinese patients with and without hypertension

Background The interleukin-6 (IL-6) gene promoter G-174C polymorphism has been associated with insulin resistance, hypertension, and coronary artery disease; however, its relationship with plasma PAI-1 level has not yet been studied. Methods The G-174C genotypes and plasma PAI-1 antigen and activity were determined in 424 Chinese subjects, 207 with hypertension and 217 without, to study the possible effects of IL-6 genotypes on the regulation of PAI-1 and blood pressure. Results Hypertensive patients showed significantly greater percentage of IL-6 GG genotype (51.7% v 33.2%, P< .001) and G allele frequency (71.7% v 59%, P< .001) than normotensive subjects. The GG genotypic group had significantly higher plasma PAI-1 activity (16.1 ± 9.8 v 12.3 ± 7.5 IU/mL, P = .03) and antigen (32.4 ± 23.2 v 23.2 ± 13.5 ng/mL, P = .01) than the CC genotypic group, with intermediate values in the GC genotypic group (15.9 ± 9.0 IU/mL and 29.1 ± 17.5 ng/mL). Multiple linear regression analysis in all study subjects and in normotensive subjects documented an independent dominant effect of IL-6 G-174C gene polymorphism on plasma levels of PAI-1 activity (P = .02 and .01) and antigen (P = .02 and .03) after log transformation and adjustment for confounding factors. Conclusions The present study showed a positive association of the IL-6 GG genotype with hypertension and with elevated plasma PAI-1 level in normotensive individuals in a Chinese population in Taiwan. Our findings suggest that the IL-6 gene promoter G-174C polymorphism may affect the regulation of PAI-1 and blood pressure through an inflammatory mechanism.