From polymorphism to phenotype: FADS2 rs174538, fatty acid signatures and disease activity in Japanese Crohn’s disease

Abstract

Crohn’s disease (CD) arises from an interplay between genetic susceptibility, immune dysregulation, and environmental factors, including diet and lipid metabolism. Polyunsaturated fatty acids (PUFAs) and their desaturase enzymes have attracted interest because they generate inflammatory lipid mediators. Matsuzawa et al recently published a study in World Journal of Gastroenterology, examining how the FADS2 polymorphism rs174538 shapes fatty acid profiles and CD activity in a homogeneous cohort of Japanese patients. Using serum and erythrocyte membrane measures and refined δ-6 and δ-5 desaturase indices, the authors demonstrate that rs174538 is associated with lower erythrocyte delta-6 desaturase index (rd.d6di) and, strikingly, with decreased d5di and lower arachidonic acid levels, an effect that Matsuzawa et al largely attribute to tight linkage with FADS1 variants. Although rs174538 itself did not stratify CD activity, rd.d6di correlated positively with the CD Activity Index (CDAI) in rs174538 wild-type patients, suggesting that erythrocyte-based indices of desaturase activity may serve as integrative biomarkers of inflammatory burden and possibly treatment response. Limitations include modest sample size, predominantly mild disease, and no prospective dietary assessment, which temper inference and generalizability. Nonetheless, the work provides a genotype-stratified link between membrane PUFA metabolism and C-reactive protein or CDAI in CD, strengthening the case for metabolically informed biomarkers.

Keywords: Crohn’s disease; FADS2; rs174538; Fatty acids; Desaturase index; Arachidonic acid; Observational study

Core Tip: FADS variants shape polyunsaturated fatty acids (PUFAs) fatty-acid profiles, but it is uncertain whether this matters in Crohn’s disease (CD). Matsuzawa et al bring this question into a CD cohort by linking rs174538 to stable erythrocyte membrane fatty-acid patterns and desaturase indices. Notably, the relationship between an erythrocyte delta-6 desaturase index and CD Activity Index was present only in rs174538 wild-type carriers and disappeared in mutant carriers. This highlights that the same metabolic marker can carry different clinical information depending on genetic background, offering a clearer framework for interpreting lipid biomarkers and inconsistent omega-3 (n-3) PUFAs trial results in inflammatory bowel disease.