IDOL deficiency inhibits cholesterol-rich diet-induced atherosclerosis in rabbits

BACKGROUND The E3 ubiquitin ligase IDOL (Inducible Degrader of the LDL-Receptor) contributes to regulation of cholesterol metabolism through degradation of LDLR, VLDLR and ApoER2. Human genetic studies support the hypothesis that IDOL could serve as a target for the treatment of dyslipidemia. However, species-specific differences in overall lipid metabolism and IDOL regulation require new preclinical models to realize its therapeutic potential. We leveraged the advantages afforded by the rabbit model to address those limitations and generated a novel rabbit IDOL knockout, which we characterized in the context of atherosclerosis. METHODS IDOL -/- rabbits were generated by CRISPR/ Cas9 technology. IDOL -/- and wildtype littermates, on standard (SD) and atherogenic high-cholesterol diets (HCDs) were compared through assessment of lipid and lipoprotein profiles, triglyceride clearance, lipoprotein lipase (LPL) activity, liver pathology, atherosclerosis development, and fecal cholesterol, with bile acid contents assessed by mass spectrometry. Results Hepatic IDOL expression was increased in response to hypercholesterolemia and hypertriglyceridemia induced by HCD. On SD, loss of IDOL increased LDLR stability with reduced total cholesterol in plasma. On HCD, IDOL -/- rabbits showed simultaneous and remarkable reduction in hypercholesterolemia and hypertriglyceridemia associated with enhanced lipid clearance and LPL activity as well as increased bile acid excretion in feces. IDOL -/- rabbits presented markedly reduced HCD-induced atherosclerosis in the aorta and left coronary artery, without enhanced liver steatosis. CONCLUSIONS Loss of IDOL in rabbits recapitulates human genetic findings, thus setting the stage to accelerate preclinical studies towards development of strategies targeting IDOL for the treatment of atherosclerotic cardiovascular disease. ### Competing Interest Statement The authors have declared no competing interest. * ABCA1 : ATP binding cassette subfamily A member 1 ABCG1 : ATP binding cassette subfamily G member 1 ALT : alanine transaminase ApoER2 : apolipoprotein E receptor 2 AST : aspartate transaminase BW : body weight CETP : cholesteryl ester transfer protein CRISPR : clustered regularly interspaced short palindromic repeats CRP : C-reactive protein CVD : cardiovascular disease DCA : deoxycholic acid FPLC : fast-performance liquid chromatography HCD : high-cholesterol diet HDL : high-density lipoprotein IDL : intermediate-density lipoprotein IDOL : inducible degrader of theLDLR KO : knockout LCA : lithocholic acid LDL : low-density lipoprotein LDLR : LDL receptor LPL : lipoprotein lipase LXR : liver X receptor oxLDL : oxidized low-density lipoprotein qPCR : quantitative real time polymerase chain reaction PCSK9 : proprotein convertase subtilisin/kexin type 9 RXR : retinoid X receptor SD : standard diet SMC : smooth muscle cell SREBP : sterol regulatory element binding transcription factor 2 TC : total cholesterol TG : triglycerides TRL : triglyceride-rich lipoprotein VLDLR : very-low-density lipoprotein receptor WT : wild type