The hexosamine biosynthetic pathway induces gene promoter activity of acetyl-CoA carboxylase beta

The cardiac isoform of acetyl-CoA carboxylase (ACC beta) produces malonyl-CoA, a potent inhibitor of mitochondrial fatty acid (FA) uptake. Higher ACC beta activity decreases FA utilization, potentially leading to intracellular myocardial lipid accumulation and insulin resistance (IR). Since increased hexosamine biosynthetic pathway (HBP) flux is linked to IR onset, we hypothesized that HBP activation leads to the induction of ACC beta gene promoter activity. Rat H9c2 cardio-myoblasts were transiently transfected with a 1317 bp human ACC beta promoter-luciferase construct (pPII beta-1317) an expression construct encoding the HBP rate-limiting step, i.e., glutamine:fructose 6-phosphate amidotransferase (GFAT) +/- various HBP modulators. The administration of L-glutamine (HBP substrate) dose-dependently increased, while HBP inhibitors attenuated pPII beta-1317 activity. Co-transfections with dominant-negative GFAT constructs diminished pPII beta-1317 activity. To explore underlying transcriptional mechanisms, we co-transfected with upstream stimulatory factor (USF) expression constructs and found that USF2 induced pPII beta-1317 activity vs. controls. Moreover, co-transfection of a GFAT expression construct + USF reporter-promoter construct (with consensus USF binding elements) led to induction of pPII beta-1317 activity vs. controls. We next performed transfections with GFAT full length ACC beta and seven truncated promoter-luciferase constructs, respectively. Here GFAT-mediated ACC beta promoter induction was blunted when co-transfected with the pPII beta-38/+65 deletion construct indicating that USF2 binds to the proximal ACC beta promoter region (near start codon). Our study demonstrates that HBP activation induces ACC beta gene promoter activity in H9c2 cells via USF2. We propose that such ACC beta induction may elicit serious downstream effects, e.g. the inhibition of FA beta-oxidation and the onset of IR. (C) 2014 Elsevier Inc. All rights reserved.