A functional variation in CHI3L1 is associated with severity of liver fibrosis and YKL-40 serum levels in chronic hepatitis C infection

Background/Aims YKL-40 is a chitinase-like protein involved in matrix remodelling and a non-invasive fibrosis marker. We assessed whether a functional promoter polymorphism in CHI3L1 , encoding YKL-40, is associated with HCV-induced liver fibrosis and influences YKL-40 serum concentrations. Methods The CHI3L1 −131G → C promoter polymorphism was genotyped in two cohorts of HCV infected patients ( n = 440) by 5′-endonuclease assays. Histological fibrosis scores and YKL-40 serum levels (ELISA) were associated with CHI3L1 −131G → C by quantitative and qualitative genetic analyses and corrected by multivariate analysis. Results CHI3L1 −131G → C genotype was strongly associated with the stage of liver fibrosis in the screening ( n = 265, P = 0.001) and validation cohort ( n = 175, P = 0.009). Homozygous carriers of the G allele were protected from severe fibrosis (F3/F4). This association was confirmed after correction for age and gender. Functionally, the G allele was associated with reduced serum levels of YKL-40 in HCV infected patients ( P = 0.002). Conclusions The CHI3L1 promoter polymorphism −131G → C determines YKL-40 serum levels and is associated with the severity of HCV-induced liver fibrosis. These results suggest a functional role of YKL-40 in liver fibrogenesis and should be taken into account when using YKL-40 as a non-invasive fibrosis marker.