Abstract 12205: A New Mouse Model of Myocardial Lipids, Fibrosis, Arrhythmia and Diastolic Dysfunction Induced by Hyperlipidemia and Cardiac LDLR

Abstract

Background: Hyperlipidemia is a major risk factor for CVD. Patients with HF with preserved ejection fraction (HFpEF) have more myocardial lipid accumulation than patients with reduced EF (HFrEF). RNASeq data from cardiac biopsies showed downregulation of the gene for lipoprotein lipase (LPL) that degrades triglycerides, in HFpEF patients compared to healthy and HFrEF controls. Poloxamer-407 (p407) induces hyperlipidemia by blocking LPL and subsequent increase in plasma triglycerides and low-density lipoprotein (LDL) cholesterol. We hypothesized that mice treated with p407 and cardiac LDL-Receptor (LDLR) over-expression (OE) develop hyperlipidemia, myocardial lipid accumulation, and diastolic dysfunction resulting in HFpEF and arrhythmias. Methods: Baseline cardiac function was assessed by echo for male and female C57Bl6 mice (n=9) for 2 groups: 4wk biweekly i.p. p407-injections with (n=4) or without (n=3) single i.v. injection with AAV9-cTnT-LDLR. Cardiac function was assessed by echocardiography at 3 and 4 wks. Blood Pressure (BP) and Whole Body Plethysmography (WBP) were assessed during wk4. Ttest was used for statistics. PR and ORO staining and telemetry were performed at wk4. Results: At wk3, P407 and LDLR OE led to alterations in diastolic function (increased IVCT, IVRT, MV E/E’, MPI, and NFT) and increased LV wall thickness, p<0.05. At wk4, there was pulmonary hypertension (increased mean pulmonary arterial pressure, decreased pulmonary acceleration time p <.05).Histology showed excessive myocardial lipids and fibrosis, and telemetry showed incidents of second-degree and higher-degree AV block. The group injected solely with p407 show e d alterations in diastolic function (increased IVCT, IVRT, NFT, LVMPI, LVMPI NFT p<.05 ) and decreased EDV, ESV, EDLVM, ESLVM, p<.05 at wk4. All groups had preserved %EF and no abnormalities in BP or WBP. Conclusions: P407 and cardiac LDLR OE induce a drastic decline in cardiac diastolic function over a shorter period of time compared to p407 alone. Diastolic dysfunction was observed in wk3 followed by pulmonary hypertension, arrhythmia, myocardial lipid accumulation and fibrosis in wk4. This new model may allow for more rapid investigations of cardiac abnormalities seen in HFpEF patients.