Abstract
Arachidonic acid (C20:4) is related to a wide range of biological effects including lipid homeostasis. The fatty acid desaturase-2 (FADS2) gene encodes for the delta-6-desaturase, which is involved in the biosynthesis of C20:4 from linoleic acid (C18:2). The purpose of this study was to characterise mutations in the promoter of the porcine FADS2, evaluating in particular the effect of one haplotype tagging polymorphism (rs321384923A > G) on the biosynthesis pathway of C20:4. A total of 1,192 Duroc barrows with records on fatty acid composition in muscle and subcutaneous fat were genotyped. Pigs carrying the A allele showed, irrespective of fat content, both enhanced FADS2 expression and higher C20:4 in muscle and exhibited increased ratios of C20:4 to C18:2 and of C20:4 to eicosadienoic acid (C20:2) in both muscle and adipose tissue. Despite the inverse relationship observed between C20:4 and fat content, the rs321384923 polymorphism had no impact on lean weight. It is concluded that the haplotype encompassing the rs321384923 polymorphism at the porcine FADS2 affects the n-6 fatty acid profile by specifically modifying the desaturation efficiency of C18:2 to C20:4 rather than by concomitant variations in C18:2 following changes in fat content.
Highlights
Arachidonic acid (C20:4, all-cis-5,8,11,14–20:4) is the precursor of several bioactive lipid mediators of the eicosanoid family related to a wide range of biological effects including lipid homeostasis and inflammatory response
The lack of fatty acid desaturase-2 (FADS2) leads to obesity resistance and, as reported by Stoffel et al.[9] using auxotrophic mice mutants, it may activate a surrogate reaction in which C18:2 is elongated to eicosadienoic acid (C20:2, all-cis-11,14–20:2) and to eicosatrienoic acid but not to C20:4 to eicosadienoic acid (C20):4
A total of 5 SNP polymorphisms and one 12 bp insertion were segregating in the proximal promoter of the pig FADS2 gene (Supplementary Fig. S1)
Summary
Arachidonic acid (C20:4, all-cis-5,8,11,14–20:4) is the precursor of several bioactive lipid mediators of the eicosanoid family related to a wide range of biological effects including lipid homeostasis and inflammatory response. FADS2 is a TATA-less gene and such genes are often subjected to complex transcription mechanisms This makes the promoter region of FADS2 a sensible location for screening for DNA polymorphisms. The aim of our study was to describe genetic variants in the promoter of the porcine FADS2 and to further investigate their association with C20:4 and fat content in the main lipogenic tissues. To this end, we made use of a biorepository of fat, muscle and liver specimens from a high-fat Duroc pig line where at least two relevant genes for fatty acid composition are segregating[14,15]
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