Cardiac dysfunction and peri-weaning mortality in malonyl-coenzyme A decarboxylase (MCD) knockout mice as a consequence of restricting substrate plasticity

Abstract

Inhibition of malonyl-coenzyme A decarboxylase (MCD) shifts metabolism from fatty acid towards glucose oxidation, which has therapeutic potential for obesity and myocardial ischemic injury. However, ~ 40% of patients with MCD deficiency are diagnosed with cardiomyopathy during infancy.AimTo clarify the link between MCD deficiency and cardiac dysfunction in early life and to determine the contributing systemic and cardiac metabolic perturbations.Methods and resultsMCD knockout mice (−/−) exhibited non-Mendelian genotype ratios (31% fewer MCD−/−) with deaths clustered around weaning. Immediately prior to weaning (18 days) MCD−/− mice had lower body weights, elevated body fat, hepatic steatosis and glycogen depletion compared to wild-type littermates. MCD−/− plasma was hyperketonemic, hyperlipidemic, had 60% lower lactate levels and markers of cellular damage were elevated. MCD−/− hearts exhibited hypertrophy, impaired ejection fraction and were energetically compromised (32% lower total adenine nucleotide pool). However differences between WT and MCD−/− converged with age, suggesting that, in surviving MCD−/− mice, early cardiac dysfunction resolves over time. These observations were corroborated by in silico modelling of cardiomyocyte metabolism, which indicated improvement of the MCD−/− metabolic phenotype and improved cardiac efficiency when switched from a high-fat diet (representative of suckling) to a standard post-weaning diet, independent of any developmental changes.ConclusionsMCD−/− mice consistently exhibited cardiac dysfunction and severe metabolic perturbations while on a high-fat, low carbohydrate diet of maternal milk and these gradually resolved post-weaning. This suggests that dysfunction is a common feature of MCD deficiency during early development, but that severity is dependent on composition of dietary substrates.

Proteomic and metabolomic changes driven by elevating myocardial creatine suggest novel metabolic feedback mechanisms

“…Hence, existing in silico models are of limited utility in understanding these findings, which suggest deep interconnections that are not part of current metabolic models. For example, the CardioNet metabolic flux model we have used previously (Aksentijevic et al 2014a ) is insensitive to altered creatine levels.…”

Intracellular sodium elevation reprograms cardiac metabolism

“…The relative contributions of exogenous 13 C substrates (palmitate vs glucose) to oxidative phosphorylation were determined from 13 C glutamate isotopomer labelling patterns ( Fig. 1b) using tcaCALC tm software (v2.07) 22,24 .…”

Age-Dependent Decline in Cardiac Function in Guanidinoacetate-N-Methyltransferase Knockout Mice

“…Snap frozen heart tissue (mean age 84 weeks) was used for metabolic profiling using previously published protocols: high resolution 1 H NMR spectroscopy (Chung et al, 2017), creatine kinase (Aksentijevic et al, 2014b) adenylate kinase (AK total , isoforms AK 1 and AK remnant ) and glycolytic enzyme activities [glyceraldehyde-3-phosphate dehydrogenase (GAPDH), 3phosphoglycerate kinase (PGK), and pyruvate kinase (PK)] assessments (Aksentijevic et al, 2010), pyruvate dehydrogenase (PDH) assay, myocardial glycogen and triacylglycerol (TAG) content assessment (Aksentijevic et al, 2014a), HPLC analysis of the total adenine nucleotide pool (ATP + ADP + AMP), creatine and phosphocreatine (PCr) (Aksentijevic et al, 2010). Method for the spectrophotometric assessment of maximal F 1 -ATPase hydrolytic activity in isolated mitochondria was developed for the purpose of this study (Supplementary Material).…”