Resveratrol improves cardiac function and exercise performance in MI-induced heart failure through the inhibition of cardiotoxic HETE metabolites.

Numerous epidemiological studies have demonstrated that approximately 40% of myocardial infarctions (MI) are associated with heart failure (HF). Resveratrol, a naturally occurring polyphenol, has been shown to be beneficial in the treatment of MI-induced HF in rodent models. However, the mechanism responsible for the effects of resveratrol are poorly understood. Interestingly, resveratrol is known to inhibit cytochrome P450 1B1 (CYP1B1) which is involved in the formation of cardiotoxic hydroxyeicosatetraenoic acid (HETE) metabolites. Therefore, we investigated whether resveratrol could improve MI-induced cardiac remodeling and HF in rats through the inhibition of CYP1B1 and its metabolites. To do this, rats were subjected to either sham surgery or a surgery to ligate the left anterior descending artery to induce a MI and subsequent HF. Three weeks post-surgery, rats with established HF were treated with control diet or administered a diet containing low dose of resveratrol. Our results showed that low dose resveratrol treatment significantly improves % ejection fraction in MI rats and reduces MI-induced left ventricular and atrial remodeling. Furthermore, non-cardiac symptoms of HF such as reduced physical activity improved with low dose resveratrol treatment. Mechanistically, low dose resveratrol treatment of rats with established HF restored levels of fatty acid oxidation and significantly improved cardiac energy metabolism as well as significantly inhibited CYP1B1 and cardiotoxic HETE metabolites induced in MI rats. Overall, the present work provides evidence that low dose resveratrol reduces the severity of MI-induced HF, at least in part, through the inhibition of CYP1B1 and cardiotoxic HETE metabolites.

A novel complex I inhibitor protects against hypertension-induced left ventricular hypertrophy.

Since left ventricular hypertrophy (LVH) increases the susceptibility for the development of other cardiac conditions, pharmacotherapy that mitigates pathological cardiac remodeling may prove to be beneficial in patients with LVH. Previous work has shown that the activation of the energy-sensing kinase AMP-activated protein kinase (AMPK) can inhibit some of the molecular mechanisms that are involved in LVH. Of interest, metformin activates AMPK through its inhibition of mitochondrial complex I in the electron transport chain and can prevent LVH induced by pressure overload. However, metformin has additional cellular effects unrelated to AMPK activation, raising questions about whether mitochondrial complex I inhibition is sufficient to reduce LVH. Herein, we characterize the cardiac effects of a novel compound (R118), which is a more potent complex I inhibitor than metformin and is thus used at a much lower concentration. We show that R118 activates AMPK in the cardiomyocyte, inhibits multiple signaling pathways involved in LVH, and prevents Gq protein-coupled receptor agonist-induced prohypertrophic signaling. We also show that in vivo administration of R118 prevents LVH in a mouse model of hypertension, suggesting that R118 can directly modulate the response of the cardiomyocyte to stress. Of importance, we also show that while R118 treatment prevents adaptive remodelling in response to elevated afterload, it does so without compromising systolic function, improves myocardial energetics, and prevents a decline in diastolic function in hypertensive mice. Taken together, our data suggest that inhibition of mitochondrial complex I may be worthy of future investigation for the treatment of LVH.NEW & NOTEWORTHY Inhibition of mitochondrial complex I by R118 reduces left ventricular hypertrophy (LVH) and improves myocardial energetics as well as diastolic function without compromising systolic function. Together, these effects demonstrate the therapeutic potential of complex I inhibitors in the treatment of LVH, even in the presence of persistent hypertension.

Cardiac hypertrophy in the newborn delays the maturation of fatty acid ß-oxidation and compromises postischemic functional recovery.

During the neonatal period, cardiac energy metabolism progresses from a fetal glycolytic profile towards one more dependent on mitochondrial oxidative metabolism. In this study, we identified the effects of cardiac hypertrophy on neonatal cardiac metabolic maturation and its impact on neonatal postischemic functional recovery. Seven-day-old rabbits were subjected to either a sham or a surgical procedure to induce a left-to-right shunt via an aortocaval fistula to cause RV volume-overload. At 3 wk of age, hearts were isolated from both groups and perfused as isolated, biventricular preparations to assess cardiac energy metabolism. Volume-overload resulted in cardiac hypertrophy (16% increase in cardiac mass, P < 0.05) without evidence of cardiac dysfunction in vivo or in vitro. Fatty acid oxidation rates were 60% lower (P < 0.05) in hypertrophied hearts than controls, whereas glycolysis increased 246% (P < 0.05). In contrast, glucose and lactate oxidation rates were unchanged. Overall ATP production rates were significantly lower in hypertrophied hearts, resulting in increased AMP-to-ATP ratios in both aerobic hearts and ischemia-reperfused hearts. The lowered energy generation of hypertrophied hearts depressed functional recovery from ischemia. Decreased fatty acid oxidation rates were accompanied by increased malonyl-CoA levels due to decreased malonyl-CoA decarboxylase activity/expression. Increased glycolysis in hypertrophied hearts was accompanied by a significant increase in hypoxia-inducible factor-1α expression, a key transcriptional regulator of glycolysis. Cardiac hypertrophy in the neonatal heart results in a reemergence of the fetal metabolic profile, which compromises ATP production in the rapidly maturing heart and impairs recovery of function following ischemia.

Isoproterenol stimulates 5'-AMP-activated protein kinase and fatty acid oxidation in neonatal hearts.

Isoproterenol increases phosphorylation of LKB, 5'-AMP-activated protein kinase (AMPK), and acetyl-CoA carboxylase (ACC), enzymes involved in regulating fatty acid oxidation. However, inotropic stimulation selectively increases glucose oxidation in adult hearts. In the neonatal heart, fatty acid oxidation becomes a major energy source, while glucose oxidation remains low. This study tested the hypothesis that increased energy demand imposed by isoproterenol originates from fatty acid oxidation, secondary to increased LKB, AMPK, and ACC phosphorylation. Isolated working hearts from 7-day-old rabbits were perfused with Krebs solution (0.4 mM palmitate, 11 mM glucose, 0.5 mM lactate, and 100 mU/l insulin) with or without isoproterenol (300 nM). Isoproterenol increased myocardial O(2) consumption (in J·g dry wt(-1)·min(-1); 11.0 ± 1.4, n = 8 vs. 7.5 ± 0.8, n = 6, P < 0.05), and the phosphorylation of LKB (in arbitrary density units; 0.87 ± 0.09, n = 6 vs. 0.59 ± 0.08, n = 6, P < 0.05), AMPK (0.82 ± 0.08, n = 6 vs. 0.51 ± 0.06, n = 6, P < 0.05), and ACC-ß (1.47 ± 0.14, n = 6 vs. 0.97 ± 0.07, n = 6, P < 0.05), with a concomitant decrease in malonyl-CoA levels (in nmol/g dry wt; 0.9 ± 0.9, n = 8 vs. 7.5 ± 1.3, n = 8, P < 0.05) and increase in palmitate oxidation (in nmol·g dry wt(-1)·min(-1); 272 ± 45, n = 8 vs. 114 ± 9, n = 6, P < 0.05). Glucose and lactate oxidation were increased (in nmol·g dry wt(-1)·min(-1); 253 ± 75, n = 8 vs. 63 ± 15, n = 9, P < 0.05 and 246 ± 43, n = 8 vs. 82 ± 11, n = 6, P < 0.05, respectively), independent of alterations in pyruvate dehydrogenase phosphorylation, but occurred secondary to a decrease in acetyl-CoA content and acetyl-CoA-to-free CoA ratio. As acetyl-CoA levels decrease in response to isoproterenol, despite an acceleration of the rates of palmitate and carbohydrate oxidation, these data suggest net rates of acetyl-CoA utilization exceed the net rates of acetyl-CoA generation.

High levels of fatty acids increase contractile function of neonatal rabbit hearts during reperfusion following ischemia.

In the neonatal heart the transition from using carbohydrates to using fatty acids has not fully matured and oxidative metabolism/ATP generation may be limiting contractile function after ischemia. This study tested the hypothesis that increasing fatty acid availability increases recovery of left ventricular (LV) work by increasing palmitate oxidation, tricarboxylic acid (TCA) cycle activity, and ATP generation. Isolated working hearts from 7-day-old rabbits were perfused with Krebs solution containing low (0.4 mM) or high (2.4 mM) palmitate and 5.5 mM glucose. Hearts were subjected to 35-min global ischemia before 40-min reperfusion, and rates of glycolysis, glucose oxidation, and palmitate oxidation were assessed. LV work was similar before ischemia but was greater during reperfusion in hearts perfused with 2.4 mM palmitate compared with hearts perfused with 0.4 mM palmitate [6.98 +/- 0.14 (n = 15) vs. 3.01 +/- 0.23 (n = 16) mJ.beat(-1).g dry wt(-1); P < 0.05]. This was accompanied by increased LV energy expenditure during reperfusion [35.98 +/- 0.16 (n = 8) vs. 19.92 +/- 0.18 (n = 6) mJ.beat(-1).g dry wt(-1); P < 0.05]. During reperfusion the rates of palmitate oxidation [237.5 +/- 28.10 (n = 7) vs. 86.0 +/- 9.7 (n = 6) nmol.g dry wt(-1).min(-1); P < 0.05], total TCA cycle activity [2.65 +/- 0.39 (n = 7) vs. 1.36 +/- 0.14 (n = 6) micromol acetyl-CoA.g dry wt(-1).min(-1); P < 0.05], and ATP generation attributable to palmitate oxidation [26.6 +/- 3.1 (n = 7) vs. 12.6 +/- 1.7 (n = 6) micromol.g dry wt(-1).min(-1); P < 0.05] were greater in hearts perfused with 2.4 mM palmitate. These data indicate that the neonatal heart has decreased energy reserve, and, in contrast to the mature heart, increasing availability of fatty acid substrate increases energy production and improves recovery of function after ischemia.

Myocardial hypertrophy and the maturation of fatty acid oxidation in the newborn human heart.

After birth dramatic decreases in cardiac malonyl CoA levels result in the rapid maturation of fatty acid oxidation. We have previously demonstrated that the decrease in malonyl CoA is due to increased activity of malonyl CoA decarboxylase (MCD), and decreased activity of acetyl CoA carboxylase (ACC), enzymes which degrade and synthesize malonyl CoA, respectively. Decreased ACC activity corresponds to an increase in the activity of 5'-AMP activated protein kinase (AMPK), which phosphorylates and inhibits ACC. These alterations are delayed by myocardial hypertrophy. As rates of fatty acid oxidation can influence the ability of the heart to withstand an ischemic insult, we examined the expression of MCD, ACC, and AMPK in the newborn human heart. Ventricular biopsies were obtained from infants undergoing cardiac surgery. Immunoblot analysis showed a positive correlation between MCD expression and age. In contrast, a negative correlation in both ACC and AMPK expression and age was observed. All ventricular samples displayed some degree of hypertrophy, however, no differences in enzyme expression were found between moderate and severe hypertrophy. This indicates that increased expression of MCD, and the decreased expression of ACC and AMPK are important regulators of the maturation of fatty acid oxidation in the newborn human heart.

Co-administration of resveratrol with doxorubicin in young mice attenuates detrimental late-occurring cardiovascular changes.

Aims: Doxorubicin (DOX) is among the most effective chemotherapies used in paediatric cancer patients. However, the clinical utility of DOX is offset by its well-known cardiotoxicity, which often does not appear until later in life. Since hypertension significantly increases the risk of late-onset heart failure in childhood cancer survivors, we investigated whether juvenile DOX exposure impairs the ability to adapt to angiotensin II (Ang II)-induced hypertension later in life and tested a treatment that could prevent this. Methods and results: Five-week-old male mice were administered a low dose of DOX (4 mg/kg) or saline once a week for 3 weeks and then allowed to recover for 5 weeks. Following the 5-week recovery period, mice were infused with Ang II or saline for 2 weeks. In another cohort, mice were fed chow containing 0.4% resveratrol 1 week before, during, and 1 week after the DOX administrations. One week after the last DOX administration, p38 mitogen-activated protein kinase (MAPK) was activated in hearts of DOX-treated mice demonstrating molecular signs of cardiac stress; yet, there was no change in cardiac function between groups. However, DOX-treated mice failed to develop compensatory cardiac hypertrophy in response to Ang II-induced hypertension later in life. Of importance, mice receiving DOX with resveratrol co-administration displayed normalization in p38 MAPK activation in the heart and a restored capacity for cardiac hypertrophy in response to Ang II-induced hypertension. Conclusion: We have developed a juvenile mouse model of DOX-induced cardiotoxicity that displays no immediate overt physiological dysfunction; but, leads to an impaired ability of the heart to adapt to hypertension later in life. We also show that co-administration of resveratrol during DOX treatment was sufficient to normalize molecular markers of cardiotoxicity and restore the ability of the heart to undergo adaptive remodelling in response to hypertension later in life.

Empagliflozin Prevents Worsening of Cardiac Function in an Experimental Model of Pressure Overload-Induced Heart Failure.

This study sought to determine whether the sodium/glucose cotransporter 2 (SGLT2) inhibitor empagliflozin improved heart failure (HF) outcomes in nondiabetic mice. The EMPA-REG OUTCOME (Empagliflozin, Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients) trial demonstrated that empagliflozin markedly prevented HF and cardiovascular death in subjects with diabetes. However, despite ongoing clinical trials in HF patients without type 2 diabetes, there are no objective and translational data to support an effect of SGLT2 inhibitors on cardiac structure and function, particularly in the absence of diabetes and in the setting of established HF. Male C57Bl/6 mice were subjected to either sham or transverse aortic constriction surgery to induce HF. Following surgery, mice that progressed to HF received either vehicle or empagliflozin for 2 weeks. Cardiac function was then assessed in vivo using echocardiography and ex vivo using isolated working hearts. Although vehicle-treated HF mice experienced a progressive worsening of cardiac function over the 2-week treatment period, this decline was blunted in empagliflozin-treated HF mice. Treatment allocation to empagliflozin resulted in an improvement in cardiac systolic function, with no significant changes in cardiac remodeling or diastolic dysfunction. Moreover, isolated hearts from HF mice treated with empagliflozin displayed significantly improved ex vivo cardiac function compared to those in vehicle-treated controls. Empagliflozin treatment of nondiabetic mice with established HF blunts the decline in cardiac function both in vivo and ex vivo, independent of diabetes. These data provide important basic and translational clues to support the evaluation of SGLT2 inhibitors as a treatment strategy in a broad range of patients with established HF.

Trimetazidine therapy prevents obesity-induced cardiomyopathy in mice.

Obesity is a significant risk factor for the development of cardiovascular disease. Inhibiting fatty acid oxidation has emerged as a novel approach for the treatment of ischemic heart disease. Our aim was to determine whether pharmacologic inhibition of 3-ketoacyl-coenzyme A thiolase (3-KAT), which catalyzes the final step of fatty acid oxidation, could improve obesity-induced cardiomyopathy. A 3-week treatment with the 3-KAT inhibitor trimetazidine prevented obesity-induced reduction in both systolic and diastolic function. Therefore, targeting cardiac fatty acid oxidation may be a novel therapeutic approach to alleviate the growing burden of obesity-related cardiomyopathy.

Inhibition of serine palmitoyl transferase I reduces cardiac ceramide levels and increases glycolysis rates following diet-induced insulin resistance.

OBJECTIVE: Diet-induced obesity (DIO) leads to an accumulation of intra-myocardial lipid metabolites implicated in causing cardiac insulin resistance and contractile dysfunction. One such metabolite is ceramide, and our aim was to determine the effects of inhibiting de novo ceramide synthesis on cardiac function and insulin stimulated glucose utilization in mice subjected to DIO. MATERIALS AND METHODS: C57BL/6 mice were fed a low fat diet or subjected to DIO for 12 weeks, and then treated for 4 weeks with either vehicle control or the serine palmitoyl transferase I (SPT I) inhibitor, myriocin. In vivo cardiac function was assessed via ultrasound echocardiography, while glucose metabolism was assessed in isolated working hearts. RESULTS: DIO was not associated with an accumulation of intra-myocardial ceramide, but rather, an accumulation of intra-myocardial DAG (2.63±0.41 vs. 4.80±0.97 nmol/g dry weight). Nonetheless, treatment of DIO mice with myriocin decreased intra-myocardial ceramide levels (50.3±7.7 vs. 26.9±2.7 nmol/g dry weight) and prevented the DIO-associated increase in intra-myocardial DAG levels. Interestingly, although DIO impaired myocardial glycolysis rates (7789±1267 vs. 2671±326 nmol/min/g dry weight), hearts from myriocin treated DIO mice exhibited an increase in glycolysis rates. CONCLUSIONS: Our data reveal that although intra-myocardial ceramide does not accumulate following DIO, inhibition of de novo ceramide synthesis nonetheless reduces intra-myocardial ceramide levels and prevents the accumulation of intra-myocardial DAG. These effects improved the DIO-associated impairment of cardiac glycolysis rates, suggesting that SPT I inhibition increases cardiac glucose utilization.