Abstract P3172: Elamipretide Reduces Mitochondrial Hyperacetylation In Left Ventricular Myocardium Of Dogs With Chronic Heart Failure

Abstract

Background: The failing heart manifests abnormalities of mitochondrial (MITO) function characterized by reduced respiration and membrane potential and increased acetylation of MITO proteins. The cause(s) of MITO protein hyperacetylation is unclear, but can be due to reduced sirtuin 3 (Sirt3) possessing deacetylase activity and increased CD38 possessing NADase activity and increased NADH/NAD ratio. Long-term therapy with elamipretide (ELAM), a MITO-targeting tetra-peptide, was shown to improve MITO function in dogs with microembolization-induced heart failure (HF). Hypothesis: We tested the hypothesis that MITO hyperacetylation caused by dysregulation of Sirt3 and CD38 and increased NADH/NAD ratio in MITO of left ventricular (LV) myocardium of HF dogs can be normalized after chronic therapy with ELAM. Methods: MITO fractions were isolated from LV tissue of 14 HF dogs randomized to 3 months monotherapy with subcutaneous injections of ELAM (HF+ELAM, 0.5 mg/kg once daily, n=7) or no therapy at all (control, HF-CON, n=7) and from LV tissue of 6 normal (NL) dogs for comparison. An NAD/NADH quantitation kit was used to determined levels of NADH and NAD in MITO fractions. Protein levels of CD38, Sirt3, and porin, an internal MITO loading control, were determined in Mito-SDS-extracts using Western blotting and band intensity expressed in densitometric units (du). Protein levels of CD38 and Sirt3 were normalized to porin. Results: Protein levels of porin were similar among NL, HF-CON and HF+ELAM dogs. In HF-CON dogs, NADH/NAD ratio increased (0.70 ± 0.14 versus 0.32 ± 0.05, p<0.05 versus HF) compared to NL dogs and decreased significantly in HF+ELAM (0.36 ± 0.02, p<0.05 versus HF-CON). In HF-CON dogs, Sirt3 (0.50 ± 0.0.05 versus 1.24 ± 0.13, p<0.05 versus NL) was significantly reduced and CD38 (1.69 ± 0.12 versus 0.70 ± 0.03, p<0.05 versus NL) was significantly increased compared to NL dogs. Treatment with ELAM normalized Sirt3 (1.0 ± 0.11, p<0.05 vs. HF-CON) and CD38 (0.92 ± 0.051, p<0.05 vs. HF-CON). Conclusions: ELAM normalized levels of Sirt3 and CD38 and reduced NADH/NAD ratio in MITO of LV of HF dogs suggesting normalization of MITO acetylome. The later may be partly responsible for improved MITO function and possibly LV function in HF dogs treated with ELAM.