Cardiac Lipotoxicity Research Articles

Correlation between increased atrial expression of genes related to fatty acid metabolism and autophagy in patients with chronic atrial fibrillation.

Atrial metabolic disturbance contributes to the onset and development of atrial fibrillation (AF). Autophagy plays a role in maintaining the cellular energy balance. We examined whether atrial gene expressions related to fatty acid metabolism and autophagy are altered in chronic AF and whether they are related to each other. Right atrial tissue was obtained during heart surgery from 51 patients with sinus rhythm (SR, n = 38) or chronic AF (n = 13). Preoperative fasting serum free-fatty-acid levels were significantly higher in the AF patients. The atrial gene expression of fatty acid binding protein 3 (FABP3), which is involved in the cells' fatty acid uptake and intracellular fatty acid transport, was significantly increased in AF patients compared to SR patients; in the SR patients it was positively correlated with the right atrial diameter and intra-atrial electromechanical delay (EMD), parameters of structural and electrical atrial remodeling that were evaluated by an echocardiography. In contrast, the two groups' atrial contents of diacylglycerol (DAG), a toxic fatty acid metabolite, were comparable. Importantly, the atrial gene expression of microtubule-associated protein light chain 3 (LC3) was significantly increased in AF patients, and autophagy-related genes including LC3 were positively correlated with the atrial expression of FABP3. In conclusion, in chronic AF patients, the atrial expression of FABP3 was upregulated in association with autophagy-related genes without altered atrial DAG content. Our findings may support the hypothesis that dysregulated cardiac fatty acid metabolism contributes to the progression of AF and induction of autophagy has a cardioprotective effect against cardiac lipotoxicity in chronic AF.

Mst1 knockdown alleviates cardiac lipotoxicity and inhibits the development of diabetic cardiomyopathy in db/db mice

Diabetic cardiomyopathy (DCM) accounts for increasing deaths of diabetic patients, and effective therapeutic targets are urgently needed. Myocardial lipotoxicity, which is caused by cardiac non-oxidative metabolic fatty acids and cardiotoxic fatty acid metabolites accumulation, has gained more attention to explain the increasing prevalence of DCM. However, whether mammalian Ste20-like kinase 1 (Mst1) plays a role in lipotoxicity in type 2 diabetes-induced cardiomyopathy has not yet been illustrated. Here, we found that Mst1 expression was elevated transcriptionally in the hearts of type 2 diabetes mellitus mice and palmitic acid-treated neonatal rat ventricular myocytes. Adeno-associated virus 9 (AAV9)-mediated Mst1 silencing in db/db mouse hearts significantly alleviated cardiac dysfunction and fibrosis. Notably, Mst1 knockdown in db/db mouse hearts decreased lipotoxic apoptosis and inflammatory response. Mst1 knockdown exerted protective effects through inactivation of MAPK/ERK kinase kinase 1 (MEKK1)/c-Jun N-terminal kinase (JNK) signaling pathway. Moreover, lipotoxicity induced Mst1 expression through promoting the binding of forkhead box O3 (FoxO3) and Mst1 promoter. Conclusively, we elucidated for the first time that Mst1 expression is regulated by FOXO3 under lipotoxicity stimulation and downregulation of Mst1 protects db/db mice from lipotoxic cardiac injury through MEKK1/JNK signaling inhibition, indicating that Mst1 abrogation may be a potential treatment strategy for DCM in type 2 diabetic patients.

Globular CTRP9 protects cardiomyocytes from palmitic acid-induced oxidative stress by enhancing autophagic flux

BackgroundOxidative stress in cardiac myocytes is an important pathogenesis of cardiac lipotoxicity. Autophagy is a cellular self-digestion process that can selectively remove damaged organelles under oxidative stress, and thus presents a potential therapeutic target against cardiac lipotoxicity. Globular CTRP9 (gCTRP9) is a newly identified adiponectin paralog with established metabolic regulatory properties. The aim of this work is to investigate whether autophagy participates the protection effects of gCTRP9 in neonatal rat cardiac myocytes (NRCMs) under oxidative stress and the underlying mechanism. ResultsNRCMs were treated with PA of various concentrations for indicated time period. Our results showed that PA enhanced intracellular ROS accumulation, decreased mitochondrial membrane potential (Δψm) and increased activation of caspases 3. These changes suggested lipotoxicity due to excessive PA. In addition, PA was observed to impair autophagic flux in NRCMs and impaired autophagosome clearance induced by PA contributes to cardiomyocyte death. Besides, we found that gCTRP9 increased the ratio of LC3II/I and the expression of ATG5 which was vital to the formation of autophagosomes and decreased the level of P62, suggesting enhanced autophagic flux in the absence or presence of PA. The result was further confirmed by the methods of infection with LC3-mRFP-GFP lentivirus and blockage of autophagosome–lysosome fusion by BafA1. Moreover, gCTRP9 reestablished the loss of mitochondrial membrane potential, suppressed ROS generation, and reduced PA -induced myocyte death. However, the protective effect of gCTRP9 on the cardiac lipotoxicity was partly abolished by blockade of autophagy by autophagy-related 5 (ATG5) siRNA, indicating that the effect of gCTRP9 on cell survival is critically mediated through regulation of autophagy. ConclusionAutophagy induction by gCTRP9 could be utilized as a potential therapeutic strategy against oxidative stress-mediated damage in cardiomyocytes.

Increasing fatty acid oxidation prevents high fat diet induced cardiomyopathy through regulating mitophagy activity

Under obese condition, an imbalance between fatty acid uptake and fatty acid oxidation (FAO) promotes the development of cardiac lipotoxicity. We have previously demonstrated that enhancing FAO via Acetyl-CoA carboxylase 2 (ACC2) deletion prevents high fat diet (HFD) induced cardiac dysfunction and attenuates pathological remodeling in obese mice. In this study, we examined the effect of enhancing FAO in regulating mitochondrial function in obese mouse heart. ACC2 flox/flox (Con) and ACC2 flox/flox-MerCreMer+ (iKO) were injected with tamoxifen and subjected to HFD feeding for 24 weeks. Mitochondria oxygen consumption rate in Con HFD-fed hearts were reduced, which was maintained in iKO mice. Electron microscopy analysis revealed that ACC2 iKO mice prevented HFD induced accumulation of damaged mitochondria (3 ± 0.24% (CON) vs. 1.27 ± 0.36% (iKO), p < .05, n = 5). In vitro, palmitate (PA) induced mitochondria fragmation and increased reactive oxggen species production was partially attenuated in cardiomyocytes when ACC2 was knocked down. Knocking down of ACC2 also prevented PA induced cell death (65.2 ± 3.1% vs. 85.3 ± 3.9%, p < .05, n = 3). These data suggest that enhancing FAO prevents HFD induced mitochondria dysfunction. Moreover, HFD treatment reduced the expression of LC3 II and p62 in mitochondria fraction. EM analysis revealed that the number of mitochondria in autophagosome was less in Con HFD-fed heart compared with Con chow-fed group in response to starvation and CCCP treatment. Mt-Keima signal, indicative of mitophagy activity in vivo, decreased in mice with HFD feeding, suggesting that HFD treatment impairs mitophagy activity. However, ACC2 iKO mice partially restored mitophagy in response to HFD feeding. Therefore, the beneficial effect for enhancing FAO in HFD induced obesity model mediates by maintenance of mitochondria function through regulating mitophagy. Our findings suggest that promoting FAO is an effective strategy to resist the development of cardiac lipotoxicity during diet-induced obesity.

The Crosstalk between Cardiac Lipotoxicity and Mitochondrial Oxidative Stress in the Cardiac Alterations in Diet-Induced Obesity in Rats.

The impact of the mitochondria-targeted antioxidant MitoQ was evaluated in the cardiac alterations associated with obesity. Male Wistar rats were fed either a high fat diet (HFD, 35% fat) or a standard diet (CT, 3.5% fat) for 7 weeks and treated with MitoQ (200 µM). The effect of MitoQ (5 nM) in rat cardiac myoblasts treated for 24 h with palmitic acid (PA, 200 µM) was evaluated. MitoQ reduced cardiac oxidative stress and prevented the development of cardiac fibrosis, hypertrophy, myocardial 18-FDG uptake reduction, and mitochondrial lipid remodeling in HFD rats. It also ameliorated cardiac mitochondrial protein level changes observed in HFD: reductions in fumarate hydratase, complex I and II, as well as increases in mitofusin 1 (MFN1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha, and cyclophilin F (cycloF). In vitro, MitoQ prevented oxidative stress and ameliorated alterations in mitochondrial proteins observed in palmitic acid (PA)-stimulated cardiac myoblasts: increases in carnitine palmitoyltransferase 1A, cycloF, and cytochrome C. PA induced phosphorylation of extracellular signal-regulated kinases and nuclear factor-κB p65. Therefore, the data show the beneficial effects of MitoQ in the cardiac damage induced by obesity and suggests a crosstalk between lipotoxicity and mitochondrial oxidative stress in this damage

CTRP9 knockout exaggerates lipotoxicity in cardiac myocytes and high-fat diet-induced cardiac hypertrophy through inhibiting the LKB1/AMPK pathway.

CTRP9 has been reported to regulate lipid metabolism and exert cardioprotective effects, yet its role in high‐fat diet (HFD)‐induced cardiac lipotoxicity and the underlying mechanisms remain unclear. In the current study, we established HFD‐induced obesity model in wild‐type (WT) or CTRP9 knockout (CTRP9‐KO) mice and palmitate‐induced lipotoxicity model in neonatal rat cardiac myocytes (NRCMs) to investigate the effects of CTRP9 on cardiac lipotoxicity. Our results demonstrated that the HFD‐fed CTRP9‐KO mice accentuated cardiac hypertrophy, fibrosis, endoplasmic reticulum (ER) stress‐initiated apoptosis and oxidative stress compared with the HFD‐fed WT mice. In vitro, CTRP9 treatment markedly alleviated palmitate‐induced oxidative stress and ER stress‐induced apoptosis in NRCMs in a dose‐dependent manner. Phosphorylated AMPK at Thr172 was reduced, and phosphorylated mammalian target of rapamycin (mTOR) was strengthened in the heart of the HFD‐fed CTRP9‐KO mice compared with the HFD‐fed control mice. In vitro, AMPK inhibitor compound C significantly abolished the effects of CTRP9 on the inhibition of the apoptotic pathway in palmitate‐treated NRCMs. In a further mechanistic study, CTRP9 enhanced expression of phosphorylated LKB1 at Ser428 and promoted LKB1 cytoplasmic localization. Besides, silencing of LKB1 gene by lentivirus significantly prohibited activation of AMPK by CTRP9 and partially eliminated the protective effect of CTRP9 on the cardiac lipotoxicity. These results indicate that CTRP9 exerted anti‐myocardial lipotoxicity properties and inhibited cardiac hypertrophy probably through the LKB1/AMPK signalling pathway.

Cardiac Lipid Metabolism Is Modulated by Casimiroa edulis and Crataegus pubescens Aqueous Extracts in High Fat and Fructose (HFF) Diet‐Fed Obese Rats

AbstractThis study aim to evaluate the effect of Casimiroa edulis and Crataegus pubescens aqueous extracts on cardiac lipotoxicity in obese rats. Both extracts decrease cardiac hypertrophy and steatosis in high fat and fructose (HFF)‐diet‐fed obese rats. C. pubescens decreases the cardiac content of 16 and 18 carbon‐length fatty acids, whereas C. edulis extract does not alter the fatty acid profile. Regarding lipotoxic compounds, C. pubescens reduces the cardiac content of 16 and 18 carbon‐length ceramides and diacylglycerols, whereas C. edulis extract reduces ≥20 carbon‐length lipotoxic compounds. Both extracts down‐regulate fatty acid synthase (Fasn) and acetyl‐CoA carboxylase (Acaca) (lipogenesis), glyceril‐3‐phosphate acyltransferase (Gpat) (diacylglycerol synthesis) and serine palmitoyltransferase 1 (Spt1) (ceramide synthesis), and up‐regulate carnitine palmitoyltransferase 1 (Cpt1) and acyl‐CoA dehydrogenase (Acadm) (β‐oxidation), and the greatest effect is observed with C. pubescens. In addition, C. edulis exerts the greatest cardiac anti‐inflammatory activity, whereas C. pubescens shows the highest cardiac antioxidant activity. The cardioprotective effect of C. pubescens may be associated with its content of (−)‐epigallocatechin gallate, (+)‐catechin, chlorogenic acid, caffeic acid, and β‐campesterol, whereas the beneficial effect of C. edulis may be related to its high content of steroidal saponins and alkaloids. Therefore, these results demonstrate that both herbal aqueous extracts ameliorate cardiac lipotoxicity in HFF‐diet‐fed rats, and C. pubescens exerts a greater beneficial effect.Practical Applications: This study proposes the characterization of fatty acids and lipotoxic compounds (ceramides and diacylglycerols) of cardiac tissue in combination with the determination of the expression of specific genes related to lipid metabolism to identify the mechanisms associated with the cardioprotective effects of herbal extracts. The results obtained in this study demonstrate the cardioprotective potential of Casimiroa edulis and Crataegus pubescens aqueous extracts through the modulation of cardiac lipid metabolism in high fat and fructose diet fed obese rats. Therefore, these herbs can be used for the development of functional beverages or the extraction of bioactive compounds with cardioprotective effect.

Abstract 641: Drosophila Adipogenesis Regulates Cardiac Function

High-calorie diets are associated with obesity, type 2 diabetes, and cardiovascular disease. Recently, several investigators have proposed a model of "maximum adipose expandability," where the limited ability of animals to store fat as triglycerides results in cellular toxicity via fatty acid overflow into alternative fates, or lipotoxicity. Tissue-specific loss-of-function studies targeting metabolic pathways in the Drosophila fat storage organ, the fat body, were used to determine the relationship between fat body lipogenesis and cardiac physiology. Our data support a model where when caloric excess overwhelms fat body lipid storage capacity, cardiac lipotoxicity ensues. Metabolomics studies in hearts and blood from these animals may help us to identify specific lipotoxins that are “conserved” between flies and humans.

Abstract 259: Resistin Accelerates Fibroblast-Myofibroblast Differentiation and Induces Myocardial Fibrosis

Background: Cardiac fibrosis (CF) is a major cause of heart failure in patients with ischemic insult, obesity, and diabetes. CF, characterized by excessive deposition of extracellular matrix proteins and myofibroblast differentiation, leads to profound changes in ventricular architecture and geometry, and thereby reduces cardiac function. Resistin, an adipokine has been linked to obesity, insulin resistance and diabetes. Our previous findings have implicated resistin in CF, however the molecular mechanisms underlying this process are still unclear. In this study, we investigated whether resistin regulates the transdifferentiation of fibroblasts into myofibroblasts as well as the molecular pathways leading to resistin-induced fibrotic response. Methods: Fibroblast-to-myofibroblast differentiation was induced with resistin, TGFβ1 or FBS for 48hours in isolated cardiac fibroblasts from adult mouse and mouse embryonic fibroblasts (NIH3T3 cells). Resistin knockout mice were challenged with high fat diet for 16 weeks to stimulate cardiac lipotoxicity. Fibrotic response and markers were determined in harvested hearts. Results: Adult cardiac fibroblasts stimulated with resistin displayed increased fibroblast-to-myofibroblast differentiation, with significantly increased levels of collagen, fibronectin, and connective tissue growth factor. Mechanistically, we demonstrated that resistin promotes fibrogenesis via Jak-Stat and c-Jun signaling pathways, independently of TGFβ1. In-vivo study confirmed the role of resistin in cardiac fibrosis. Resistin knockout mice, when challenged with high fat diet to stimulate cardiac lipotoxicity, showed a decrease in fibrosis paralleled with reduced mRNA levels of various markers of fibrosis such as collagen, fibronectin and connective tissue growth factor compered to wild type hearts. A significant improvement in heart function was also observed in resistin knockout mice. Conclusions: To our knowledge, these findings are the first to demonstrate a role of resistin in the process of cardiac fibroblast-to-myofibroblast conversion through Jak-Stat and c-Jun signaling. These results bring new insights into the mechanisms by which resistin may contribute to cardiac fibrosis.

An attempt to reverse cardiac lipotoxicity by aerobic interval training in a high-fat diet- and streptozotocin-induced type 2 diabetes rat model

BackgroundDiabetes mellitus (DM) is an important risk factor for cardiovascular disease. Aerobic interval training (AIT) has been recommended to patients as a non-pharmacological strategy to manage DM. However, little is known about whether AIT intervention at the onset of DM will reverse the process of diabetic cardiomyopathy (DCM). In this study, we sought to evaluate whether AIT can reverse the process of DCM and explore the underlying mechanisms.MethodsFifty Wistar rats were randomly divided into a control group (CON), DCM group (DCM) and AIT intervention group (AIT). A high-fat diet and streptozotocin (STZ) were used to induce diabetes in rats in the DCM group and AIT group. Rats in the AIT group were subjected to an 8-week AIT intervention. Fasting blood glucose (FBG), lipid profiles and insulin levels were measured. Haematoxylin and eosin (HE) staining and oil red O staining were used to identify cardiac morphology and lipid accumulation, respectively. Serum BNP levels and cardiac BNP mRNA expression were measured to ensure the safety of the AIT intervention. Free fatty acid (FFA) and diacylglycerol (DAG) concentrations were analysed by enzymatic methods. AMPK, p-AMPK, FOXO1, CD36 and PPARα gene and protein expression were detected by RT-PCR and Western blotting.ResultsAIT intervention significantly reduced rat serum cardiovascular disease risk factors in DCM rats (P < 0.05). The safety of AIT intervention was illustrated by reduced serum BNP levels and cardiac BNP mRNA expression (P < 0.05) after AIT intervention in DCM rats histological analysis and FFA and DAG concentrations revealed that AIT intervention reduced the accumulation of lipid droplets within cardiomyocytes and alleviated cardiac lipotoxicity (P < 0.05). CD36 and PPARα gene and protein expression were elevated in the DCM group, and these increases were reduced by AIT intervention (P < 0.01). The normalized myocardial lipotoxicity was due to increased expression of phosphorylated AMPK and reduced FOXO1 expression after AIT intervention.ConclusionAIT intervention may alleviate cardiac lipotoxicity and reverse the process of DCM through activation of the AMPK–FOXO1 pathway.

Silencing the Very Low-density Lipoprotein Receptor (VLDLR) Prevents Obesity Associated with Excess Lipid Deposition (P21-040-19)

ObjectivesObesity is associated with an insulin resistant state, characterized by abnormalities in lipid metabolism, a leading cause of morbidity and mortality in cardiovascular diseases (CVD). Very low-density lipoprotein receptor (VLDLR), a member of the LDL receptor family, binds and increases the catabolism of apolipoprotein E triglyceride-rich lipoproteins. Although VLDLR is highly expressed in the heart, its role in obesity associated lipotoxicity is not well understood. MethodsIn the current study, lean WT, VLDLR-deficient (VLDLR−/−), genetically obese leptin-deficient (Lepob/ob), and leptin–VLDLR double-null (Lepob/ob/VLDLR−/−) mice were used to determine the impact of VLDLR deficiency on obesity-induced cardiac lipotoxicity. ResultsThe results showed that insulin sensitivity and glucose uptake were reduced in the hearts of Lepob/ob mice, and at the same time, VLDLR expression was upregulated and associated with increased VLDL uptake resulting in excess lipid deposition. These changes were accompanied by upregulation of cardiac NADPH oxidase (Nox) expression and increased production of Nox-dependent superoxides. Silencing the VLDLR in Lepob/ob mice reduced VLDL uptake and prevented excess lipid deposition. Moreover, VLDLR deficiency reduced superoxide overproduction and normalized glucose uptake. In isolated cardiomyocytes, VLDLR deficiency prevented VLDL-mediated induction of NOx activity and superoxide overproduction while improving insulin sensitivity and glucose uptake. An important observation showed that Lepob/ob/VLDLR−/− mice compared to Lepob/ob mice, had significantly improved heart performance and energetic reserves. ConclusionsThese findings suggest that that when VLDLR is silenced (deficiency), lipid deposition is also reduced, preventing cardiac lipotoxicity in obesity. In addition, the effects may be linked to the role of VLDLR on VLDL uptake, which triggers a cascade of events leading to insulin resistance and superoxide overproduction. Funding SourcesInstitutional Support.Howard University, Washington DC 20059Hackensack University Medical Center, NJ 07601

Cardiomyopathy in obesity, insulin resistance and diabetes.

The prevalence of obesity, insulin resistance and diabetes is increasing rapidly. Most patients with these disorders have hypertriglyceridaemia and increased plasma levels of fatty acids, which are taken up and stored in lipid droplets in the heart. Intramyocardial lipids that exceed the capacity for storage and oxidation can be lipotoxic and induce non-ischaemic and non-hypertensive cardiomyopathy, termed diabetic or lipotoxic cardiomyopathy. The clinical features of diabetic cardiomyopathy are cardiac hypertrophy and diastolic dysfunction, which lead to heart failure, especially heart failure with preserved ejection fraction. Although the pathogenesis of the cardiomyopathy is multifactorial, diabetic dyslipidaemia and intramyocardial lipid accumulation are the key pathological features, triggering cellular signalling and modifications of proteins and lipids via generation of toxic metabolic intermediates. Most clinical studies have shown no beneficial effect of anti-diabetic agents and statins on outcomes in heart failure patients without atherosclerotic diseases, indicating the importance of identifying underlying mechanisms and early interventions for diabetic cardiomyopathy. Here, we summarize the molecular mechanisms of diabetic cardiomyopathy, with a special emphasis on cardiac lipotoxicity, and discuss the role of peroxisome proliferator-activated receptor α and dysregulated fatty acid metabolism as potential therapeutic targets.

High Saturated and Unsaturated Fat Diets Yield Different Disease Phenotypes in Mice

Excessive consumption of unsaturated or saturated fatty acids have adverse effects on certain health parameters, namely increased risk of obesity, diabetes, and cardiovascular disease. Specifically, saturated fats are linked to increased cardiovascular risk while unsaturated fats are suggested to protect against cardiovascular disease. Our previous work suggested that various high fat diets have differential effects on cardiac hypertrophy and function. However, it was not clear whether a high saturated fat diet (HSFD) or high unsaturated fat diet (HUFD) could elicit different disease phenotypes. Therefore, the purpose of this study was to evaluate the effects of HSFD or HUFD on the development of obesity, diabetes, and cardiac lipotoxicity in mice. Male, C57BL/6J mice received normal chow (CON, n=12), HSFD (n=15) or HUFD (n=15) for 12 weeks. Body weight and food intake were measured weekly. After 12 weeks, the adipose tissue and heart were removed and weighed. Glucose, fatty acids, and cholesterol were analyzed in serum using biochemical assays. Cardiac triglycerides (TG) were measured in heart tissue extracts. Both HSFD and HUFD significantly increased body weight above CON. Interestingly, body weight increased by ~63% in the HUFD while the HSFD increased ~41% (P&lt;0.05). Adipose tissue mass was increased 5‐fold in both HFD groups and was ~10% greater in the HUFD. Surprisingly, caloric intake was higher in the HSFD (15.3±0.8) compared to HUFD (12.8±0.1) and CON (11.9±0.7). Serum cholesterol levels were elevated in both HSFD and HUFD. Blood glucose was significantly increased only in the HUFD while serum fatty acids were increased only in the HSFD. Cardiac hypertrophy, assessed by the heart weight to tibia length ratio, was increased in the HSFD but not HUFD group. Cardiac TGs were ~25% higher in HSFD but &lt;10% in HUFD compared to CON. These data show that excess consumption of saturated or unsaturated fats increased body weight and adiposity in mice. However, high consumption of unsaturated fatty acids resulted in a pronounced increase in body weight, body fat, and hyperglycemia, consistent with an obese and diabetic phenotype. Conversely, high consumption of saturated fatty acids caused elevated serum lipids, cardiac hypertrophy, and cardiac lipid accumulation, consistent with cardiac lipotoxicity. In conclusion, the fatty acid composition of diets may be critical in the development of disease phenotypes resulting from high fat feeding in mice.Support or Funding InformationThis work was supported by funding from the American Heart Association and Ursinus College.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Preservation of Acyl Coenzyme A Attenuates Pathological and Metabolic Cardiac Remodeling Through Selective Lipid Trafficking.

Metabolic remodeling in heart failure contributes to dysfunctional lipid trafficking and lipotoxicity. Acyl coenzyme A synthetase-1 (ACSL1) facilitates long-chain fatty acid (LCFA) uptake and activation with coenzyme A (CoA), mediating the fate of LCFA. The authors tested whether cardiac ACSL1 overexpression aids LCFA oxidation and reduces lipotoxicity under pathological stress of transverse aortic constriction (TAC). Mice with cardiac restricted ACSL1 overexpression (MHC-ACSL1) underwent TAC or sham surgery followed by serial in vivo echocardiography for 14 weeks. At the decompensated stage of hypertrophy, isolated hearts were perfused with 13C LCFA during dynamic-mode 13C nuclear magnetic resonance followed by in vitro nuclear magnetic resonance and mass spectrometry analysis to assess intramyocardial lipid trafficking. In parallel, acyl CoA was measured in tissue obtained from heart failure patients pre- and postleft ventricular device implantation plus matched controls. TAC-induced cardiac hypertrophy and dysfunction was mitigated in MHC-ACSL1 hearts compared with nontransgenic hearts. At 14 weeks, TAC increased heart weight to tibia length by 46% in nontransgenic mice, but only 26% in MHC-ACSL1 mice, whereas ACSL1 mice retained greater ejection fraction (ACSL1 TAC: 65.8±7.5%; nontransgenic TAC: 45.9±7.3) and improvement in diastolic E/E'. Functional improvements were mediated by ACSL1 changes to cardiac LCFA trafficking. ACSL1 accelerated LCFA uptake, preventing C16 acyl CoA loss post-TAC. Long-chain acyl CoA was similarly reduced in human failing myocardium and restored to control levels by mechanical unloading. ACSL1 trafficked LCFA into ceramides without normalizing the reduced triglyceride storage in TAC. ACSL1 prevented de novo synthesis of cardiotoxic C16- and C24-, and C24:1 ceramides and increased potentially cardioprotective C20- and C22-ceramides post-TAC. ACLS1 overexpression activated AMP activated protein kinase at baseline, but during TAC, prevented the reduced LCFA oxidation in hypertrophic hearts and normalized energy state (phosphocreatine:ATP) and consequently, AMP activated protein kinase activation. This is the first demonstration of reduced acyl CoA in failing hearts of humans and mice, and suggests possible mechanisms for maintaining mitochondrial oxidative energy metabolism by restoring long-chain acyl CoA through ASCL1 activation and mechanical unloading. By mitigating cardiac lipotoxicity, via redirected LCFA trafficking to ceramides, and restoring acyl CoA, ACSL1 delayed progressive cardiac remodeling and failure.

The Impact of Cardiac Lipotoxicity on Cardiac Function and Mirnas Signature in Obese and Non-Obese Rats with Myocardial Infarction

Cardiac lipotoxicity is involved in the cardiac functional consequences associated with obesity. Therefore, the aim of this study was to explore whether changes in the mitochondrial lipid cardiac profile could reflect differences in cardiac function and structure in obese and non-obese rats with myocardial infarction (MI). Whether these changes can also be reflected in a specific plasma miRNA signature as markers of cardiac damage was also evaluated. Rats were fed with either standard (3.5% fat) or high fat diet (35% fat) for 6 weeks before the induction of MI and sacrificed 4 weeks later. MI showed cardiac lipotoxicity independently of the presence of obesity, although obese and non-obese rats did not present the same cardiac lipid profile at mitochondrial level. Several cardiac lipid species in mitochondria, including cardiolipins and triglycerides, were associated with myocardial fibrosis, with mitochondrial triglyceride levels being independently associated with it; this supports that lipotoxicity can affect cardiac function. MI down-regulated plasma levels of miRNA 15b-5p and 194-5p in obese and non-obese animals, which were associated with cardiac function, mitochondrial lipids and myocardial fibrosis, with miRNA 15b-5p levels being independently associated with cardiac fibrosis. This could support that lipotoxicity could affect heart function by modulating plasma miRNAs.

Intergenerational inheritance of high fat diet-induced cardiac lipotoxicity in Drosophila

Obesity is strongly correlated with lipotoxic cardiomyopathy, heart failure and thus mortality. The incidence of obesity has reached alarming proportions worldwide, and increasing evidence suggests that the parents’ nutritional status may predispose their offspring to lipotoxic cardiomyopathy. However, to date, mechanisms underlying intergenerational heart disease risks have yet to be elucidated. Here we report that cardiac dysfunction induced by high-fat-diet (HFD) persists for two subsequent generations in Drosophila and is associated with reduced expression of two key metabolic regulators, adipose triglyceride lipase (ATGL/bmm) and transcriptional cofactor PGC-1. We provide evidence that targeted expression of ATGL/bmm in the offspring of HFD-fed parents protects them, and the subsequent generation, from cardio-lipotoxicity. Furthermore, we find that intergenerational inheritance of lipotoxic cardiomyopathy correlates with elevated systemic H3K27 trimethylation. Lowering H3K27 trimethylation genetically or pharmacologically in the offspring of HFD-fed parents prevents cardiac pathology. This suggests that metabolic homeostasis is epigenetically regulated across generations.

Cardiac metabolic modulation upon low-carbohydrate low-protein ketogenic diet in diabetic rats studied in vivo using hyperpolarized 13 C pyruvate, butyrate and acetoacetate probes.

To investigate the effects of long-term low-carbohydrate low-protein ketogenic diet (KD) on cardiac metabolism and diabetic cardiomyopathy status in lean diabetic Goto-Kakizaki (GK) rats. Diabetic GK rats were fed with KD for 62 weeks. Cardiac function and metabolism were assessed using magnetic resonance imaging and 13 C magnetic resonance spectroscopy (13 C-MRS), at rest and under dobutamine stress. 13 C-MRS was performed following injection of hyperpolarized [3-13 C]acetoacetate, [1-13 C]butyrate or [1-13 C]pyruvate to assess ketone body, short-chain fatty acid or glucose utilization, respectively. Protein expression and cardiomyocyte structure were determined via Western blotting and histology, respectively. KD lowered blood glucose, triglyceride and insulin levels while increasing blood ketone body levels. In KD-fed diabetic rats, myocardial ketone body and glucose oxidation were lower than in chow-fed diabetic rats, while myocardial glycolysis and short-chain fatty acid oxidation were unaltered. Dobutamine stress revealed an increased cardiac preload and reduced cardiac compliance in KD-fed diabetic rats. Dobutamine-induced stimulation of myocardial glycolysis was more enhanced in KD-fed diabetic rats than in chow-fed diabetic rats, which was potentially facilitated via an upregulation in basal expression of proteins involved in glucose transport and glycolysis in the hearts of KD-fed rats. The metabolic profile induced by KD was accompanied by cardiac hypertrophy, a trend for increased myocardial lipid and collagen content, and an increased marker of oxidative stress. KD seems to exacerbate diabetic cardiomyopathy in GK rats, which may be associated with maladaptive cardiac metabolic modulation and lipotoxicity.

IL-6: A Potential Role in Cardiac Metabolic Homeostasis.

Interleukin-6 (IL-6) is implicated in multiple biological functions including immunity, neural development, and haematopoiesis. Recently, mounting evidence indicates that IL-6 plays a key role in metabolism, especially lipid metabolic homeostasis. A working heart requires a high and constant energy input which is largely generated by fatty acid (FA) β-oxidation. Under pathological conditions, the precise balance between cardiac FA uptake and metabolism is perturbed so that excessive FA is accumulated, thereby predisposing to myocardial dysfunction (cardiac lipotoxicity). In this review, we summarize the current evidence that suggests the involvement of IL-6 in lipid metabolism. Cardiac metabolic features and consequences of myocardial lipotoxicity are also briefly analyzed. Finally, the roles of IL-6 in cardiac FA uptake (i.e., serum lipid profile and myocardial FA transporters) and FA metabolism (namely, β-oxidation, mitochondrial function, biogenesis, and FA de novo synthesis) are discussed. Overall, understanding how IL-6 transmits signals to affect lipid metabolism in the heart might allow for development of better clinical therapies for obesity-associated cardiac lipotoxicity.

Abstract 282: Increasing Cardiac Fatty Acid Oxidation Protects Against High Fat Diet Induced Mitochondria Dysfunction and Cardiomyopathy in Mice

In the obese and diabetic heart, an imbalance between fatty acid uptake and fatty acid oxidation (FAO) promotes the development of cardiac lipotoxicity. In this study, we tested the hypothesis that enhancing FAO via ACC2 deletion in an adult heart would prevent the cardiac lipotoxic phenotype in a mouse model of diet-induced obesity. ACC2 flox/flox (CON) and ACC2 flox/flox-MerCreMer+ (iKO) were injected with tamoxifen and subjected to a high fat diet (HFD) for 24 weeks. In isolated Langendorff-perfused heart experiments, HFD feeding increased FAO 1.6-fold in CON mice which was further increased to 1.9-fold in iKO mice compared with CON on chow diet. HFD induced systolic and diastolic dysfunction was abolished in iKO mice compared with CON mice (Fractional shortening 32.8±2.8% (CON) vs. 39.2±3.2% (iKO), E’/A’ ratio 0.91±0.09 (CON) vs. 1.11±0.08 (iKO), p&lt; 0.05, n=5-6). Heart weight /Tibia length ratio was significantly higher in CON than iKO mice after HFD feeding (7.19±0.22 vs. 6.47±0.28, p&lt;0.05, n=6). These data indicate that enhancing myocardial FAO via ACC2 deletion prevents HFD induced cardiac dysfunction and attenuates pathological hypertrophy in obese mice. We then examined the mitochondrial respiration activity under chow and HFD fed conditions. HFD feeding significantly reduced mitochondria oxygen consumption rate in Con hearts but not in iKO mice (332 vs. 418 pmoles/min, p&lt;0.05, n=5), suggesting that enhancing FAO prevented HFD induced mitochondria dysfunction. In vitro, palmitate (PA) induced mitochondria fragmentation and increased reactive oxygen species production was partially attenuated in ACC2 knocked down cardiomyocyte. Knocking down of ACC2 also prevented PA induced cell death. Moreover, HFD treatment significantly reduced the expression of LC3 and p62 in mitochondria fraction, indicative of impaired mitophagy in obese mice, which was attenuated in iKO mice. Therefore, the beneficial effect for enhancing cardiac fatty oxidation in HFD induced obesity model is mediated, in part, by maintenance of mitochondrial function through regulating mitophagy activity. Taken together, our findings suggest that promoting cardiac FAO is an effective strategy to prevent the development of cardiac lipotoxicity during diet-induced obesity.

Glucagon-like peptide-1 ameliorates cardiac lipotoxicity in diabetic cardiomyopathy via the PPARα pathway.

SummaryLipotoxicity cardiomyopathy is the result of excessive accumulation and oxidation of toxic lipids in the heart. It is a major threat to patients with diabetes. Glucagon‐like peptide‐1 (GLP‐1) has aroused considerable interest as a novel therapeutic target for diabetes mellitus because it stimulates insulin secretion. Here, we investigated the effects and mechanisms of the GLP‐1 analog exendin‐4 and the dipeptidyl peptidase‐4 inhibitor saxagliptin on cardiac lipid metabolism in diabetic mice (DM). The increased myocardial lipid accumulation, oxidative stress, apoptosis, and cardiac remodeling and dysfunction induced in DM by low streptozotocin doses and high‐fat diets were significantly reversed by exendin‐4 and saxagliptin treatments for 8 weeks. We found that exendin‐4 inhibited abnormal activation of the (PPARα)‐CD36 pathway by stimulating protein kinase A (PKA) but suppressing the Rho‐associated protein kinase (ROCK) pathway in DM hearts, palmitic acid (PA)‐treated rat h9c2 cardiomyocytes (CMs), and isolated adult mouse CMs. Cardioprotection in DM mediated by exendin‐4 was abolished by combination therapy with the PPARα agonist wy‐14643 but mimicked by PPARα gene deficiency. Therefore, the PPARα pathway accounted for the effects of exendin‐4. This conclusion was confirmed in cardiac‐restricted overexpression of PPARα mediated by adeno‐associated virus serotype‐9 containing a cardiac troponin T promoter. Our results provide the first direct evidence that GLP‐1 protects cardiac function by inhibiting the ROCK/PPARα pathway, thereby ameliorating lipotoxicity in diabetic cardiomyopathy.