Delta‐6 Desaturase Substrate Competition between 16:0 and 18:2n‐6 or 18:3n‐3 May Limit the Accumulation of 16:1n‐10

Abstract

IntroductionThe FADS2 gene codes for protein that mediates fatty acid desaturation of at least nine substrates. Among these are 16:0, 18:2n‐6, and 18:3n‐3. Desaturation of 16:0 yields sapienic acid, the most abundant unsaturated fatty acid on human skin. Competition for delta‐6 desaturase (D6D) activity among these substrates is poorly understood. Our main objective was to test competition for D6D among these fatty acids using human cells expressing FADS2.Methods.MCF‐7 cells stably expressing FADS2 were created using pcDNA3.1 expression vector system. Stable FADS2 cells at confluence were treated with albumin‐bound fatty acid substrates (16:0, 18:2n‐6, 18:3n‐3), empty vector cells were used as controls. 16:0 levels were fixed at 50 uM, while 18:2n‐6 or 18:3n‐3 levels varied from low to high (0 uM, 20 uM, 50 uM and 100 uM). Cells were harvested after 24 hours, FAME prepared and analyzed by GC‐FID.Positive structural assignments were made by covalent adduct chemical ionization tandem mass spectrometry (CACI‐MS/MS).Results.Increasing availability of 18:2n‐6 or 18:3n‐3 resulted in decreased bioconversion of 16:0 to 16:1n‐10, simultaneously increasing the levels of HUFA precursors (18:3n‐6 and 20:3n‐6 or 18:4n‐3 and 20:4n‐3).ConclusionOur study shows existence of competition between 16:0 and 18:2n‐6 or 18:3n‐3 for accessing D6D. Increasing EFA substrate availability may limit accumulation of 16:1n‐10 in MCF7 cells.