Analysis Of Cardiac Mitochondrial Proteome Dynamics Shows Decreased Rate Of Protein Synthesis In Heart Failure

We developed a novel method to assess the synthesis rate of individual mitochondrial proteins using deuterium labeled water (D2O) as a stable isotopic tracer and advance mass spectrometric analysis. Here we assess the impact of heart failure (HF) on mitochondrial protein synthesis. HF was induced in rats by pressure overload with transverse aortic constriction for 22 weeks. Individual protein synthesis rates were assessed by giving 5% D2O in drinking water for up to 80 days, and measuring deuterium incorporation into mitochondrial proteins. There was clear HF, with 44% increase in left ventricular (LV) mass, and 40% decrease in LV fractional shortening compared to shams. Subsarcolemmal mitochondria were isolated. State 3 respiration decreased by 16% with HF using palmitoyl carnitine as the substrate, but was unaffected with non‐lipid substrates. Mitochondrial protein synthesis rates were measured by LTQ Orbitrap MS. Initial analysis showed that the fatty acid oxidation (FAO) enzyme trifunctional protein alpha subunit had a half‐life (t1/2) of 29 days in shams, which increased to 41 days with HF. The t1/2 of the electron transport chain (ETC) protein complex 3 core 2 subunit increased dramatically from 76 days in shams to 166 days in TAC rats. In conclusion, HF induced by cardiac hypertrophy slows the synthesis rate of key mitochondrial proteins, with a greater effect on ETC proteins than on FAO proteins.