Overexpression of long chain acyl‐CoA synthetase 1 increases fatty acid oxidation in primary human skeletal myotubes

Abstract

In liver, long chain acyl-CoA synthetase (ACSL) activates fatty acids and plays a key role in their partitioning toward oxidation or storage, but little data exist from human skeletal muscle. The purpose of this study was to determine the effects of ACSL-1 overexpression (ACSL-1OEX) on fatty acid oxidation (FAO; CO2 production and O2 consumption) and total lipid synthesis in human skeletal muscle cells (HSKMC). Primary myoblasts isolated from vastus lateralis (N=5) were transfected with ACSL-1 plasmid DNA, differentiated into myotubes and harvested (7 d) to measure FAO ([1-14C] palmitate), or permeabilized for determination of mitochondrial respiration. The protein levels of ACSL-1 were 38% higher in ACSL-1OEX HSKMC. Both complete (CO2) and incomplete (ASM) FAO increased by approximately 2-fold (P < 0.05). In permeabilized HSKMC supported by fatty acids, both maximal ADP-stimulated (state 3) and maximal uncoupled (FCCP-linked) oxygen consumption were significantly increased in ACSL-1OEX (P<0.05), implying greater fatty acid catabolic flux capacity. However, ACSL-1 overexpression did not affect total lipid synthesis. These data demonstrate that ACSL-1 overexpression in HSKMC increases FAO as well as maximal stimulated (ADP & FCCP) respiration without affecting total lipid storage, suggesting that activation of fatty acids is at least partially rate limiting for fatty acid oxidation. Supported by NIH DK075880 (RNC) and DK073488 (PDN).