Plasma levels of fibrinogen and C-reactive protein are related to interleukin-6 gene −572C>G polymorphism in subjects with and without hypertension

Hypertension is an important risk factor for cardiovascular diseases. There is increasing evidence suggesting that inflammation is involved in the development of hypertension. Interleukin-6 (IL-6) is an important mediator of inflammatory response and the major regulator of hepatic production of acute phase proteins, such as fibrinogen and C-reactive protein (CRP), which have been associated with hypertension and cardiovascular diseases. Therefore, we studied the association of single nucleotide polymorphism (SNP) in the IL-6 gene (IL6) promoter with plasma levels of fibrinogen, CRP and hypertension. Five hundred and two Hong Kong Chinese subjects (282 normotensives and 220 hypertensives) were recruited. IL-6 gene promoter was examined for polymorphism and the study subjects were genotyped for any SNP identified. The IL6 −572C>G polymorphism (rs1800796) was found with a frequency of 0.23 for the minor G allele. Subjects with the −572G allele had significantly higher plasma fibrinogen (3.06±0.57 vs 2.83±0.60, P=0.002) and CRP (interquartile range 0.33–1.56 vs 0.12–0.93, P=0.003) levels than those without. The −572C>G polymorphism was found to be an independent predictor of fibrinogen and CRP levels after adjusting for confounding factors. Plasma concentrations of fibrinogen and CRP correlated with systolic blood pressure. However, the −572C/G genotype frequencies did not differ between hypertensive and normotensive subjects, and there was no association between −572C>G polymorphism and blood pressure. Our results provide evidence that there is a clear genetic influence of IL6 −572C>G polymorphism on plasma levels of fibrinogen and CRP, but this polymorphism does not lead to elevated blood pressure.