YKL-40 as a clinical biomarker in adult patients with CF: Implications of a CHI3L1 single nucleotide polymorphism in disease severity

YKL-40 (chitinase 3-like 1 gene; CHI3L1) is an inflammatory marker that is increased in the blood of patients with inflammatory diseases, including cystic fibrosis (CF). The objective of our study was to explore the relationship between circulating levels of YKL-40, selected CHI3L1 single nucleotide polymorphisms (SNPs) and the severity of CF disease.A prospective cohort of 188 adult patients with CF was established in 2015. Blood samples and clinical data were collected over 2 years to analyze the circulating levels of YKL-40 and to genotype selected CHI3L1 SNPs. We also looked for an association between these factors and clinical parameters.We found that according to the serum YKL-40 concentration, the patients could be categorized into two distinct groups: low and high YKL-40. Compared to the patients in the low YKL-40 group, the patients in the high YKL-40 group had lower lung function (P0.001), a higher proportion of delF508 homozygote mutations (P= 0.027) and dysglycemia (P= 0.015). They were also more colonized with Pseudomonas aeruginosa (P= 0.003) and required more frequent antibiotic intravenous courses (P0.001). We also observed that patients expressing the C/C-rs4950928 genotype had higher levels of YKL-40 in their blood and were more frequently dysglycemic.Our study suggests that YKL-40 could be a potential biomarker of CF disease severity. Furthermore, the CHI3L1 rs4950928 SNP could be a susceptible gene that could be used by CF health professionals to identify patients who are the most at risk of having a severe clinical profile.