ELOVL3, 6 and 7 Specifically Elongate Saturated Branched Chain Fatty Acids and Compete with Normal Fatty Acids

Abstract

IntroductionBranched chain fatty acids (BCFA) are saturated fatty acids (SFA) terminating with either an isopropyl or isobutyl group. They are common components in human diets, and are synthesized de novo in human skin sebaceous and meibomian glands as well as vernix caseosa. They are known to have structure specific activities but little known of the pathways for their endogenous interconversion. Multiple human ELOVLx (elongase of very long chain fatty acids) genes are responsible for interconversion of saturated fatty acids. Our objectives are to perform the first investigation of the activity of ELOVL on BCFA using anteiso‐15:0 and iso‐18:0 as examples, to characterize the substrate specificity to BCFA, and to investigate competition between BCFA and normal (n‐) SFA (n‐16:0 and n‐18:0) for the ELOVL‐mediated elongation.MethodsHuman breast cancer cell line MCF7 was used as the experiment model. MCF7 cells were grown in MEM‐α media with 10% FBS in a humidified environment at 37°C with 5% CO2. The open reading frame of ELOVL transcripts (ELOVL1, ELOVL3, ELOVL6 and ELOVL7) were cloned into a pcDNA3.1 expression vector. MCF7 cells were transfected with specific ELOVL transgene vector along with empty vector (control) for 24h using Polyplus jetPRIME transfection reagent. Then albumin‐bound fatty acids, anteiso‐15:0, iso‐18:0, n‐16:0 and n‐18:0 were dosed into cells at 0–100 μM and allowed to incubate for additional 24h. Cells were washed twice with 1 × PBS, harvested by trypsinization, fatty acid methyl esters were analyzed by GC‐FID and GC‐MS.ResultsELOVL6 chiefly elongated anteiso‐15:0 à anteiso‐17:0; ELOVL3 predominantly elongated iso‐18:0 à iso‐20:0; ELOVL7 showed moderate elongase activity toward both anteiso‐15:0 and iso‐18:0. n‐16:0 competed with anteiso‐15:0 for ELOVL6 mediated elongation, and n‐18:0 competed with iso‐18:0 for ELOVL3 mediated elongation. These latter results verified the characterized elongation activities.ConclusionHere for the first time we showed the substrate specificity of human elongase to BCFA systematically, and verified it by establishing competition between BCFA and n‐SFA.Support or Funding InformationInternal Fund