Abstract 21171: Combinatorial Aso-Mediated Knockdown of ApoB and DGAT2 Inhibits Both VLDL Secretion and High Fat Diet Induced Hepatic Steatosis

Abstract

We previously demonstrated that mice fed a Western-type and treated with apoB antisense (ASO) for 6 weeks had both reductions in VLDL secretion and the same levels of hepatic triglycerides (TG) as did mice receiving control ASO. The reduction in hepatic TG was due to trapping of TG that had been transferred to the ER lumen by MTP where it was trapped because of the knockdown (KD) of apoB. Trapped ER-TG stimulated endoplasmic reticulum (ER) autophagy (A), which transported ER-TG to lysosomes where it was hydrolyzed to fatty acids (FA) that were oxidized by mitochondria. We have used this model in test if ASO treatment to KD apoB together with either diacylglycerol-acylt-transferase-1 (DGAT1) or DGAT2 ASO-KD would (1) reduce hepatic TG to levels below mice receiving only control ASO, and (2) provide insights into whether either DGAT1 or DGAT2 preferentially transferred newly synthesized TG into the ER. ASO-KD of either DGAT1 or DGAT2 alone reduced secretion of apoB and TG about 30-40%, but hepatic TG was much greater than controls with DGAT1 KD and less than controls with DGAT2 KD. Combined KD of either apoB and DGAT1 or apoB and DGAT2 inhibited apoB and TG secretion similarly by about 70-80%, the same degree of inhibition as with apoB ASO alone. Both double KD approaches reduced hepatic TG to below that of either control or apoB ASO alone, but hepatic TG with combined apoB-DGAT2 KD was about half of that seen with apoB-DGAT1 KD: combined apoB-DGAT2 KD had hepatic TG that was reduced by 75% versus control ASO-treated mice and similar to levels we see with chow diets. As we previously reported, apoB KD for 6 weeks caused ER autophagy and increased FA oxidation; levels of ER autophagy and FA oxidation with combined apoB-DGAT1 KD were similar to apoB KD alone. Importantly, combined apoB-DGAT2 KD had both more ER autophagy and greater increases in FA oxidation than either apoB KD or apoB-DGAT1 KD. Thus, apoB-DGAT2 KD could be a promising therapy for reduction of apoB-lipoproteins without hepatic steatosis. The results also indicate that TG synthesized by DGAT1 is preferentially transferred to the ER compared to DGAT2 generated TG.