Background-The angiotensin-converting enzyme 2 and angiotensin-(1-7) (Ang 1-7)/MasR (Mas receptor) axis are emerging as a key pathway that can modulate the development of diabetic cardiomyopathy. We studied the effects of Ang 1-7 on diabetic cardiomyopathy in db/db diabetic mice to elucidate the therapeutic effects and mechanism of action. Methods and Results-Ang 1-7 was administered to 5-month-old male db/db mice for 28 days via implanted microosmotic pumps. Ang 1-7 treatment ameliorated myocardial hypertrophy and fibrosis with normalization of diastolic dysfunction assessed by pressure-volume loop analysis and echocardiography. The functional improvement by Ang 1-7 was accompanied by a reduction in myocardial lipid accumulation and systemic fat mass and inflammation and increased insulin-stimulated myocardial glucose oxidation. Increased myocardial protein kinase C levels and loss of phosphorylation of extracellular signal-regulated kinase 1/2 were prevented by Ang 1-7. Furthermore, Ang 1-7 treatment decreased cardiac triacylglycerol and ceramide levels in db/db mice, concomitantly with an increase in myocardial adipose triglyceride lipase expression. Changes in adipose triglyceride lipase expression correlated with increased SIRT1 (silent mating type information regulation 2 homolog 1) levels and deacetylation of FOXO1 (forkhead box O1). Conclusions-We identified a novel beneficial effect of Ang 1-7 on diabetic cardiomyopathy that involved a reduction in cardiac hypertrophy and lipotoxicity, adipose inflammation, and an upregulation of adipose triglyceride lipase. Ang 1-7 completely rescued the diastolic dysfunction in the db/db model. Ang 1-7 represents a promising therapy for diabetic cardiomyopathy associated with type 2 diabetes mellitus. (Circ Heart Fail. 2014;7:327-339.)

ObjectiveBrown and white adipose tissue exerts pleiotropic effects on systemic energy metabolism in part by releasing endocrine factors. Neuregulin 4 (Nrg4) was recently identified as a brown fat-enriched secreted factor that ameliorates diet-induced metabolic disorders, including insulin resistance and hepatic steatosis. However, the physiological mechanisms through which Nrg4 regulates energy balance and glucose and lipid metabolism remain incompletely understood. The aims of the current study were: i) to investigate the regulation of adipose Nrg4 expression during obesity and the physiological signals involved, ii) to elucidate the mechanisms underlying Nrg4 regulation of energy balance and glucose and lipid metabolism, and iii) to explore whether Nrg4 regulates adipose tissue secretome gene expression and adipokine secretion.MethodsWe examined the correlation of adipose Nrg4 expression with obesity in a cohort of diet-induced obese mice and investigated the upstream signals that regulate Nrg4 expression. We performed metabolic cage and hyperinsulinemic-euglycemic clamp studies in Nrg4 transgenic mice to dissect the metabolic pathways regulated by Nrg4. We investigated how Nrg4 regulates hepatic lipid metabolism in the fasting state and explored the effects of Nrg4 on adipose tissue gene expression, particularly those encoding secreted factors.ResultsAdipose Nrg4 expression is inversely correlated with adiposity and regulated by pro-inflammatory and anti-inflammatory signaling. Transgenic expression of Nrg4 increases energy expenditure and augments whole body glucose metabolism. Nrg4 protects mice from diet-induced hepatic steatosis in part through activation of hepatic fatty acid oxidation and ketogenesis. Finally, Nrg4 promotes a healthy adipokine profile during obesity.ConclusionsNrg4 exerts pleiotropic beneficial effects on energy balance and glucose and lipid metabolism to ameliorate obesity-associated metabolic disorders. Biologic therapeutics based on Nrg4 may improve both type 2 diabetes and non-alcoholic fatty liver disease (NAFLD) in patients.

Background: Branched chain amino acids (BCAA) can impair insulin signaling, and cardiac insulin resistance can occur in the failing heart. We, therefore, determined if cardiac BCAA accumulation occurs in patients with dilated cardiomyopathy (DCM), due to an impaired catabolism of BCAA, and if stimulating cardiac BCAA oxidation can improve cardiac function in mice with heart failure. Method: For human cohorts of DCM and control, both male and female patients of ages between 22 and 66 years were recruited with informed consent from University of Alberta hospital. Left ventricular biopsies were obtained at the time of transplantation. Control biopsies were obtained from non-transplanted donor hearts without heart disease history. To determine if stimulating BCAA catabolism could lessen the severity of heart failure, C57BL/6J mice subjected to a transverse aortic constriction (TAC) were treated between 1 to 4-week post-surgery with either vehicle or a stimulator of BCAA oxidation (BT2, 40 mg/kg/day). Result: Echocardiographic data showed a reduction in ejection fraction (54.3 ± 2.3 to 22.3 ± 2.2%) and an enhanced formation of cardiac fibrosis in DCM patients when compared to the control patients. Cardiac BCAA levels were dramatically elevated in left ventricular samples of patients with DCM. Hearts from DCM patients showed a blunted insulin signalling pathway, as indicated by an increase in P-IRS1ser636/639 and its upstream modulator P-p70S6K, but a decrease in its downstream modulators P-AKT ser473 and in P-GSK3β ser9. Cardiac BCAA oxidation in isolated working hearts was significantly enhanced by BT2, compared to vehicle, following either acute or chronic treatment. Treatment of TAC mice with BT2 significantly improved cardiac function in both sham and TAC mice (63.0 ± 1.8 and 56.9 ± 3.8% ejection fraction respectively). Furthermore, P-BCKDH and BCKDK expression was significantly decreased in the BT2 treated groups. Conclusion: We conclude that impaired cardiac BCAA catabolism and insulin signaling occur in human heart failure, while enhancing BCAA oxidation can improve cardiac function in the failing mouse heart.

Fukushima A, Alrob OA, Zhang L, Wagg CS, Altamimi T, Rawat S, Rebeyka IM, Kantor PF, Lopaschuk GD. Acetylation and succinylation contribute to maturational alterations in energy metabolism in the newborn heart. Am J Physiol Heart Circ Physiol 311: H347-H363, 2016. First published June 3, 2016; doi:10.1152/ajpheart.00900.2015.-Dramatic maturational changes in cardiac energy metabolism occur in the newborn period, with a shift from glycolysis to fatty acid oxidation. Acetylation and succinylation of lysyl residues are novel posttranslational modifications involved in the control of cardiac energy metabolism. We investigated the impact of changes in protein acetylation/succinylation on the maturational changes in energy metabolism of 1-, 7-, and 21-day-old rabbit hearts. Cardiac fatty acid ␤-oxidation rates increased in 21-day vs. 1-and 7-day-old hearts, whereas glycolysis and glucose oxidation rates decreased in 21-day-old hearts. The fatty acid oxidation enzymes, long-chain acyl-CoA dehydrogenase (LCAD) and ␤-hydroxyacylCoA dehydrogenase (␤-HAD), were hyperacetylated with maturation, positively correlated with their activities and fatty acid ␤-oxidation rates. This alteration was associated with increased expression of the mitochondrial acetyltransferase, general control of amino acid synthesis 5 like 1 (GCN5L1), since silencing GCN5L1 mRNA in H9c2 cells significantly reduced acetylation and activity of LCAD and ␤-HAD. An increase in mitochondrial ATP production rates with maturation was associated with the decreased acetylation of peroxisome proliferator-activated receptor-␥ coactivator-1␣, a transcriptional regulator for mitochondrial biogenesis. In addition, hypoxiainducible factor-1␣, hexokinase, and phosphoglycerate mutase expression declined postbirth, whereas acetylation of these glycolytic enzymes increased. Phosphorylation rather than acetylation of pyruvate dehydrogenase (PDH) increased in 21-day-old hearts, accounting for the low glucose oxidation postbirth. A maturational increase was also observed in succinylation of PDH and LCAD. Collectively, our data are the first suggesting that acetylation and succinylation of the key metabolic enzymes in newborn hearts play a crucial role in cardiac energy metabolism with maturation.Listen to this article's corresponding podcast at http://ajpheart.podbean. com/e/acetylation-control-of-energy-metabolism-in-newborn-hearts/. myocardial fatty acid oxidation; lysine acetylation; lysine succinylation; newborn heart NEW & NOTEWORTHYThe present study is the first showing that alterations in acetylation and succinylation control of metabolic enzymes contribute to the dramatic shift in cardiac energy metabolism from glycolysis to fatty acid ␤-oxidation seen during maturation. Our results suggest that lysine acetylation enhances cardiac fatty acid ␤-oxidation and inhibits glycolysis during maturation.OVER 1% OF NEWBORNS ARE DIAGNOSED with congenital heart disease (CHD), with one-third of these needing surgery within the first months of life (36). Despite the major advance...

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Aims Ketones have been proposed to be a “thrifty” fuel for the heart and increasing cardiac ketone oxidation can be cardioprotective. However, it is unclear how much ketone oxidation can contribute to energy production in the heart, nor whether increasing ketone oxidation increases cardiac efficiency. Therefore, our goal was to determine to what extent high levels of the ketone body, β-hydroxybutyrate (βOHB), contributes to cardiac energy production, and whether this influences cardiac efficiency. Methods and Results Isolated working mice hearts were aerobically perfused with palmitate (0.8mM or 1.2mM), glucose (5mM) and increasing concentrations of βOHB (0, 0.6, 2.0mM). Subsequently, oxidation of these substrates, cardiac function and cardiac efficiency were assessed. Increasing βOHB concentrations increased myocardial ketone oxidation rates without affecting glucose or fatty acid oxidation rates where normal physiological levels of glucose (5mM) and fatty acid (0.8mM) are present. Notably, ketones became the major fuel source for the heart at 2.0mM βOHB (at both low or high fatty acid concentrations), with the elevated ketone oxidation rates markedly increasing TCA cycle activity, producing a large amount of reducing equivalents and finally, increasing myocardial oxygen consumption. However, the marked increase in ketone oxidation at high concentrations of βOHB was not accompanied by an increase in cardiac work, suggesting that a mismatch between excess reduced equivalents production from ketone oxidation and cardiac ATP production. Consequently, cardiac efficiency decreased when the heart was exposed to higher ketone levels. Conclusions We demonstrate that while ketones can become the major fuel source for the heart, they do not increase cardiac efficiency, which also underscores the importance of recognizing ketones as a major fuel source for the heart in times of starvation, consumption of a ketogenic diet or poorly controlled diabetes. Translational Perspective Recent clinical interest has focused on ketones as a potential fuel source for the failing heart, primarily because ketones have been popularized as a “thrifty” fuel that may increase cardiac efficiency. However, we have directly assessed cardiac ketone oxidation rates alongside their competing energy substrates and found that: not only can ketones become the major fuel of the heart with no inhibitory effect on cardiac glucose oxidation, but they can provide the healthy heart with an excess energy supply, with no changes to cardiac function, resulting in a mismatch between reducing equivalents supply and cardiac ATP production, ultimately contributing to a decrease in cardiac efficiency.

Aims: Obesity is associated with high rates of cardiac fatty acid oxidation, low rates of glucose oxidation, cardiac hypertrophy and heart failure. Whether weight loss can lessen the severity of heart failure associated with obesity is not known. We therefore determined the effect of weight loss on cardiac energy metabolism and the severity of heart failure in obese mice with heart failure.Materials and methods: Obesity and heart failure were induced by feeding mice a highfat (HF) diet and subjecting them to transverse aortic constriction (TAC). Obese mice with heart failure were then switched for 8 weeks to either a low-fat (LF) diet (HF TAC LF) or caloric restriction (CR) (40% caloric intake reduction, HF TAC CR) to induce weight loss.Results: Weight loss improved cardiac function (%EF was 38 ± 6% and 36 ± 6% in HF TAC LF and HF TAC CR mice vs 25 ± 3% in HF TAC mice, P < 0.05) and it decreased cardiac hypertrophy post TAC (left ventricle mass was 168 ± 7 and 171 ± 10 mg in HF TAC LF and HF TAC CR mice, respectively, vs 210 ± 8 mg in HF TAC mice, P < 0.05). Weight loss enhanced cardiac insulin signalling, insulin-stimulated glucose oxidation rates (1.5 ± 0.1 and 1.5 ± 0.1 μmol/g dry wt/min in HF TAC LF and HF TAC CR mice, respectively, vs 0.2 ± 0.1 μmol/g dry wt/min in HF TAC mice, P < 0.05) and it decreased pyruvate dehydrogenase phosphorylation. Cardiac fatty acid oxidation rates, AMPK Tyr172 /ACC Ser79 signalling and the acetylation of ß-oxidation enzymes, were attenuated following weight loss.Conclusions: Weight loss is an effective intervention to improve cardiac function and energy metabolism in heart failure associated with obesity. K E Y W O R D Sacetylation, fatty acid oxidation, glucose oxidation, heart failure, obesity, weight loss

FoxO1 inhibition alleviates type 2 diabetes-related diastolic dysfunction by increasing myocardial pyruvate dehydrogenase activity Graphical abstract Highlights d Diabetic cardiomyopathy is characterized by diastolic dysfunction d Genetic and pharmacological inhibition of FoxO1 improves diastolic dysfunction in T2D d FoxO1 inhibition increases myocardial glucose oxidation rates in T2D d FoxO1 inhibition improves diastolic dysfunction in T2D by increasing PDH activity