Genes Involved in the Metabolism of Poly-Unsaturated Fatty-Acids (PUFA) and Risk for Crohn's Disease in Children & Young Adults

BACKGROUND AND OBJECTIVES Epidemiological evidence for the role of polyunsaturated fatty-acids (PUFA) in Crohn's disease (CD) is unclear, although the key metabolite leucotriene B4 (LTB(4)) is closely linked to the inflammatory process. We hypothesized that inherited variation in key PUFA metabolic enzymes may modify susceptibility for CD. METHODS AND PRINCIPAL RESULTS A case-control design was implemented at three pediatric gastroenterology clinics in Canada. Children ≤20 yrs diagnosed with CD and controls were recruited. 19 single nucleotide polymorphisms (SNPs) across the ALOX5 (4) CYP4F3 (5) and CYP4F2 (10) genes, were genotyped. Associations between SNPs/haplotypes and CD were examined. A total of 431 cases and 507 controls were studied. The mean (±SD) age of the cases was 12.4 (±3.3) years. Most cases were male (56.4%), had ileo-colonic disease (L3±L4, 52.7%) and inflammatory behavior (B1±p, 87%) at diagnosis. One genotyped CYP4F3 SNP (rs2683037) not in Hardy-Weinberg Equilibrium was excluded. No associations with the remaining 4 CYP4F3 SNPs with CD were evident. However haplotype analysis revealed associations with a two-marker haplotype (TG) (rs3794987 & rs1290617) (p = 0.02; permuted p = 0.08). CYP4F2 SNPs, rs3093158 (OR (recessive) = 0.56, 95% CI = 0.35-0.89; p = 0.01), rs2074902 (OR (trend) = 1.26, 95% CI = 1.00-1.60; p = 0.05), and rs2108622 (OR (recessive) = 1.6, 95% CI = 1.00-2.57; p = 0.05) were significantly associated whereas rs1272 (OR (recessive) = 0.58, 95% CI = 0.30-1.13; p = 0.10) showed suggestions for associations with CD. A haplotype comprising these 4 SNPs was significantly associated (p = 0.007, permuted p = 0.02) with CD. Associations with SNP rs3780901 in the ALOX5 gene were borderline non-significant (OR (dominant) = 1.29, 95% CI = 0.99-1.67; p = 0.056). A haplotype comprising the 4 ALOX5 SNPs (TCAA, p = 0.036) was associated with CD, but did not withstand corrections for multiple comparisons (permuted p = 0.14). CONCLUSIONS Inherited variation in enzymes involved in the synthesis/metabolism of LTB(4) may be associated with CD. These findings implicate PUFA metabolism as a important pathway in the CD pathogenesis.