Abstract 14110: Inhibition of Lpl and CD36 Does Not Prevent Lipid Accumulation in the Hearts of Adipose Triglyceride Lipase (ATGL) Deficient Mice

Abstract

We tested whether murine ATGL deficiency-induced cardiotoxicity would be prevented by reducing uptake of circulating lipids through inhibition of lipoprotein lipase (LpL) or the fatty acid transporter CD36. Mice were created with floxed alleles for Atgl and Lpl and expression of MHC-Cre. Triglyceride content in the heart was 10x greater in the Atgl KO mice compared to control, and concurrent Lpl deletion did not change that. The Lpl Atgl DKO hearts had a comparable gross appearance and similar weights to the Atgl KO mice. The mice also had a similar survival rate with early death beginning at ~12 weeks. We then hypothesized that non-esterified fatty acids rather than triglyceride-derived fatty acids were the source of lipids in Atgl deficient hearts. To test this, we reduced CD36 expression using an antisense oligonucleotide (ASO) and also by creating heart specific combined Atgl and Cd36 knockout mice. The ASO knocked down CD36 expression in both CD31 (endothelial cells) and non-CD31 cells from the heart. It also reduced starvation lipid droplet formation and accumulated heart lipids after 3 weeks of a high fat diet. Surprisingly, neither the ASO nor genetic knockout rescued the Atgl deficient hearts from lipid accumulation or prevented early mortality. Placing mice on high fat (60%) or high sucrose (40%) diets also did not alter the development of heart dysfunction. We then hypothesized that the lipid accumulation with ATGL deficiency could occur independent of access to exogenous lipids. We tested this in vitro using H9c2(2-1) rat cardiomyocytes. After an overnight incubation in serum-free medium to deplete lipid droplets, inhibition of ATGL with Atglistatin led to cardiomyocyte accumulation of lipid droplets in the absence of a lipid source in the media. Concurrent inhibition of fatty acid synthase (FASN) with C75, cerulenin, or platensimycin prevented lipid droplet accumulation. Together, our data suggest that ATGL deficient lipid accumulation and toxicity can occur exclusive of lipid uptake.