Light, C. | bioRxiv Science

bioRxiv2022

Genetic Architecture of Heart Mitochondrial Proteome influencing Cardiac Hypertrophy

Mitochondria play a key role in the normal function of the heart as well as in the pathogenesis of diseases. We report analysis of common genetic variations contributing to mitochondrial and heart functions using an integrative proteomics approach in a panel of inbred mouse strains called the Hybrid Mouse Diversity Panel (HMDP). We performed a whole heart proteomic analysis in the HMDP (72 strains, n=2-3 mice) and retrieved 840 mitochondrial proteins (quantified in [≥]50 strains). High-resolution association mapping on their respective abundance levels identified three trans-acting genetic loci, located on chromosome (chr) 7, chr13 and chr17, that control distinct classes of mitochondrial proteins as well as heart hypertrophy. Follow-up high resolution regional mapping identified NDUFS4, LRPPRC and COQ7 as the candidate genes for chr13, chr17 and chr7 loci, respectively, and both experimental and statistical analyses supported their causal roles. Variations of all three were associated with heart mass in two independent heart stress models, namely, isoproterenol (ISO)-induced heart failure and diet-induced obesity (DIO) models. To identify the aspects of mitochondrial metabolism regulated by these loci, we constructed co-expression protein networks using weighted gene co-expression network analysis (WGCNA). DAVID enrichment analyses of genes regulated by each of the loci revealed that the chr13 locus was highly enriched for complex-I proteins (24 proteins, P = 2.2E-61), the chr17 locus for mitochondrial ribonucleoprotein complex (17 proteins, P = 3.1E-25) and the chr7 locus for ubiquinone biosynthesis (3 proteins, P = 6.9E-05). These results indicate that common variations of certain mitochondrial proteins can act in trans to influence mitochondrial functions and contribute to heart hypertrophy, elucidating mechanisms that may underlie genetic susceptibility to heart failure in human populations.

genetics↗

bioRxiv2020

NAD+ Redox Imbalance in the Heart Exacerbates Diabetic Cardiomyopathy

BackgroundDiabetes is a risk factor of heart failure and promotes cardiac dysfunction. Diabetic tissues are associated with NAD+ redox imbalance; however, the hypothesis that NAD+ redox imbalance leads to dysfunction of diabetic hearts has not been tested. In this study, we employed mouse models with altered NAD+ redox balance to test the hypothesis. Methods and ResultsDiabetes was induced in C57BL/6 mice by streptozotocin injections, and diabetic cardiomyopathy (DCM) was allowed to develop for 16 weeks. Diabetic stress led to cardiac dysfunction and lowered NAD+/NADH ratio. This diabetogenic regimen was administered to cardiac-specific knockout mice of complex I subunit Ndufs4 (cKO), a model with lowered cardiac NAD+/NADH ratio without baseline dysfunction. Cardiac NAD+ redox imbalance in cKO hearts exacerbated systolic and diastolic dysfunction of diabetic mice in both sexes. Collagen levels and transcript analyses of fibrosis and extracellular matrix-dependent pathways did not show change in diabetic cKO hearts, suggesting that the exacerbated cardiac dysfunction was likely due to cardiomyocyte dysfunction. We found that cardiac NAD+ redox imbalance promoted superoxide dismutase 2 (SOD2) acetylation, protein oxidation, induced troponin I S150 phosphorylation and impaired energetics in diabetic cKO hearts. Importantly, elevation of cardiac NAD+ levels by nicotinamide phosphoribosyltransferase (NAMPT) normalized NAD+ redox balance, over-expression alleviated cardiac dysfunction and reversed pathogenic mechanisms in diabetic mice. ConclusionOur results show that NAD+ redox imbalance to regulate protein acetylation and phosphorylation is a critical mediator of the progression of DCM, and suggest the therapeutic potential of harnessing NAD+ metabolism in DCM.

physiology↗