The Role of FADS1 and FADS2 Genes in Oleic Acid (18:1n‐9) Metabolism: FADS1 Δ7‐Desaturates Gondoic Acid (20:1n‐9, 11–20:1) to 7,11–20:2

Abstract

IntroductionIn mammals, FADS2 catalyzes “front‐end” Δ4‐, Δ6‐, and Δ8‐desaturation of fatty acyl chains, whereas FADS1 has Δ5‐desaturase activity. 18‐ and 20‐carbon precursors of highly unsaturated omega‐3 and omega‐6 fatty acids are common substrates for FADS1 and FADS2.Our main objective was to characterize the metabolic fate of oleic acid (OA) by FADS gene product.MethodsMCF‐7 cells were stably transformed with either FADS1 or FADS2 via pcDNA3.1 expression vector. A series of dose‐response experiments were conducted with albumin‐bound fatty acid substrates (18:1n‐9 and 20:1n‐9) provided in concentrations ranging from 0–100 μm. Cells were harvested after 24 h, fatty acid methyl esters were analyzed by GC‐FID and structures were confirmed by GC‐covalent adduct chemical ionization tandem mass spectrometry (GC‐CACI‐MS/MS).ResultsWhen stable cells were incubated with 18:1n‐9, FADS1 and control cells elongated 18:1n‐9 ‐> 20:1n‐9, and FADS2 cells Δ6‐desaturated, elongated and then Δ5‐desaturated via FADS1‐coded activity in MCF7 cells: 9–18:1 ‐> 6,9–18:2 ‐>8,11–20:2 ‐>6,8,11–20:3 (20:3n‐9). Surprisingly, FADS1 cells Δ7‐desaturated 20:1n‐9 ‐> 7,11–20:2. Our results imply two pathways for oleic acid metabolism: 18:1n‐9 ‐> (Δ6‐desaturation) ‐> 18:2n‐9 ‐> (Elongation) ‐> 20:2n‐9 ‐> (Δ5‐desaturation) ‐> 20:3n‐9 and 18:1n‐9 ‐> (Elongation) ‐> 20:1n‐9 ‐> (Δ7‐desaturation) ‐> 7,11–20:2.ConclusionAlternative pathways for oleic acid metabolism exist, with the metabolic fate of OA dependent on the relative FADS2 or elongase activities. Additionally, we present the first evidence of Δ7‐desaturation via the FADS1 gene product.Support or Funding InformationNIH R01 AT007003