Loss of SIRT5 accelerates the development of pressure-overload induced heart failure upon dysregulating purine and pyrimidine metabolism

Objectives: To explore how modulation of cardiomyocyte SIRT5 levels affects the development of pathological cardiac remodeling and dysfunction. Background: SIRT5 is a mitochondrial NAD+-dependent deacylase, which regulates metabolic enzymes upon desuccinylation, demalonylation, and deglutarylation. Its role in the development of heart failure is not completely understood. Methods: Mice with cardiomyocyte-specific Sirt5 deletion (Sirt5-/-) or Sirt5 overexpression (cSirt5-Tg) underwent transverse aortic constriction (TAC) or Sham surgery. Cardiac structure and function were assessed by echocardiography and quantification of myocardial fibrosis and cardiomyocyte cell size. Metabolomic analysis and RNA sequencing were performed to identify potential novel pathways regulated by SIRT5. Results: While cardiac structure and function were similar in cSirt5-Tg compared to control mice, cSirt5-/- mice displayed exacerbated cardiac dilation, dysfunction, and fibrosis following TAC. Accumulation of metabolites involved in purine metabolism, particularly inosine and hypoxanthine, and reductions in nucleosides, adenosine and adenine, and nucleotides, AMP and ADP, were observed in hearts of cSirt5-/- mice and following TAC. Moreover, transcriptional analysis revealed upregulation of purine-nucleoside phosphorylase (PNP) and 5' nucleotidase, ecto (NT5E) and downregulation of adenosine kinase (ADK), which is likely to contribute to enhanced degradation of purine nucleotides and resulting accumulation of inosine and hypoxanthine in hearts of cSirt5-/- mice following TAC. Lastly, reduced SIRT5 expression and protein succinylation in left-ventricular tissue of patients with heart failure correlates with reduced ADK expression. Conclusions: Loss of SIRT5 aggravates cardiac remodeling and dysfunction in response to chronic pressure-overload possibly by dysregulation of genes involved in purine and pyrimidine metabolism, resulting in impaired ATP regeneration from adenosine. Overall design: All mice were housed with 12h daylight and night cycles at 22°C in individually ventilated cages in a specific pathogen free facility. Laboratory standard chow and water ad libitum were fed to all animals. Transgenic Sirt5 knockout (Sirt5-/-) mice were kindly provided by Johan Auwerx from the École Polytechnique Fédérale de Lausanne, Switzerland. David Lombard from University of Michigan, Ann Arbor, Michigan, USA kindly provided transgenic Sirt5 overexpressing (Sirt5-Tg) mice. Transgenic Sirt5-/- and Sirt5-Tg mice were crossed with hemizygote cardiomyocyte-specific recombinase expressing mice (Myh6-cre, Stock #011038, Jax) to generate cardiomyocyte-specific Sirt5 knockout (cSirt5-/-) and cardiomyocyte-specific Sirt5 overexpressing (cSirt5-Tg) mice, respectively. Recombinase non-expressing transgenic mice were used as controls.