Abstract 233: Metabolic Trapping Effects of ACS1 for Fatty Acid Uptake and Intracellular Trafficking are Different in Hearts of Males and Females

Abstract

Disruption of cardiomyocyte lipid metabolism has been observed in the responses to both pathogenic and nutrient stresses in human patients and animal models, with distinct sex differences. This investigation examined cardiac acyl CoA synthetase-1 (ACS)-mediated, LCFA uptake and trafficking with hearts of male and female mice. Isolated mouse hearts with cardiac specific overexpression of ACS1 (MHC-ACS) and non-transgenic littermates (NTG) were perfused with buffer containing 13C palmitate, 10 mM glucose, and 1 mM lactate. Dynamic 13C NMR elucidated the two phases of LCFA incorporation into triacylglycerol (TAG). The time constant (τ) of the initial exponential phase, corresponding to LCFA trans-sarcolemmal uptake, was lower, indicating faster LCFA uptake and esterification in male ACS hearts compared to NTG males (ACS male τ = 1.59±0.67 min vs NTG male τ = 2.85±0.90 min, P<0.05). Consistent with greater metabolic trapping, acyl CoA content was 470% higher in male ACS hearts (NTG male 57.5±9.4 vs ACS male 327.4±42 pmol/mg protein. P<0.001). Despite no differences in ACS content, NTG females displayed faster uptake than NTG males at a rate similar to ACS males, which was reversed by ovariectomy (OVX) indicating an estrogen dependent response (NTG female τ = 1.56±0.46 min, P<0.05 vs NTG OVX female τ = 3.02±0.77 min, P<0.05). Despite prior reports of ACS localization distal from the sarcolemma, ACS level and female gender both independently accelerated LCFA uptake without affecting TAG content or turnover. The data are consistent with metabolic trapping to facilitate LCFA uptake due to ACS activity. ACS also leads to higher total ceramide in hearts, with specific elevation of C18 and C22 in both genders, C24 in males, and C20 in females (male P<0.05; female P<0.01). ACS overexpression induced lower content of the cardiac fatty acid transporter (FATP) isoform, FATP6, indicating cooperative regulation of LCFA uptake between membrane transport proteins and intracellular acyl chain activation (P<0.05 male; P<0.001 female and female OVX). These results demonstrate that perturbation of LCFA metabolism though facilitated metabolic trapping by ACS1 affects sarcolemma transporter expression and induces the conversion of the CoA activated LCFA to ceramide.