Intramyocardial Lipid Accumulation Research Articles

Fructose aggravates copper-deficiency-induced cardiac remodeling by inhibiting SERCA2a.

Accumulating evidence demonstrates that copper deficiency (CuD) is a risk factor for cardiovascular diseases, besides, fructose has been strongly linked to the development of cardiovascular diseases. However, how CuD or fructose causes cardiovascular diseases is not clearly delineated. The present study aims to investigate the mechanism of CuD or fructose on cardiac remodeling. We established a model of CuD- or fructose-induced cardiac hypertrophy in 3-week-old male Sprague-Dawley (SD) rats by CuD diet supplemented with or without 30% fructose for 4 weeks. In vitro study was performed by treating cardiomyocytes with tetrathiomolydbate (TM) and fructose. Echocardiography, histology analysis, immunofluorescence, western blotting, and qPCR were performed. Our findings revealed that CuD caused noticeable cardiac hypertrophy either in the presence or absence of fructose supplement. Fructose exacerbated CuD-induced cardiac remodeling and intramyocardial lipid accumulation. Furthermore, we presented that the inhibition of autophagic flux caused by Ca2+ disturbance is the key mechanism by which CuD- or fructose-induced cardiac remodeling. The reduced expression of sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) in cardiomyocytes accounts for the elevated cytoplasmic Ca2+ concentration. Collectively, our study suggested that fructose aggravated CuD-induced cardiac remodeling through the blockade of autophagic flux via SERCA2a decreasing-induced Ca2+ imbalance.

Treatment with recombinant Sirt1 rewires the cardiac lipidome and rescues diabetes-related metabolic cardiomyopathy.

Metabolic cardiomyopathy (MCM), characterized by intramyocardial lipid accumulation, drives the progression to heart failure with preserved ejection fraction (HFpEF). Although evidence suggests that the mammalian silent information regulator 1 (Sirt1) orchestrates myocardial lipid metabolism, it is unknown whether its exogenous administration could avoid MCM onset. We investigated whether chronic treatment with recombinant Sirt1 (rSirt1) could halt MCM progression. db/db mice, an established model of MCM, were supplemented with intraperitoneal rSirt1 or vehicle for 4weeks and compared with their db/ + heterozygous littermates. At the end of treatment, cardiac function was assessed by cardiac ultrasound and left ventricular samples were collected and processed for molecular analysis. Transcriptional changes were evaluated using a custom PCR array. Lipidomic analysis was performed by mass spectrometry. H9c2 cardiomyocytes exposed to hyperglycaemia and treated with rSirt1 were used as in vitro model of MCM to investigate the ability of rSirt1 to directly target cardiomyocytes and modulate malondialdehyde levels and caspase 3 activity. Myocardial samples from diabetic and nondiabetic patients were analysed to explore Sirt1 expression levels and signaling pathways. rSirt1 treatment restored cardiac Sirt1 levels and preserved cardiac performance by improving left ventricular ejection fraction, fractional shortening and diastolic function (E/A ratio). In left ventricular samples from rSirt1-treated db/db mice, rSirt1 modulated the cardiac lipidome: medium and long-chain triacylglycerols, long-chain triacylglycerols, and triacylglycerols containing only saturated fatty acids were reduced, while those containing docosahexaenoic acid were increased. Mechanistically, several genes involved in lipid trafficking, metabolism and inflammation, such as Cd36, Acox3, Pparg, Ncoa3, and Ppara were downregulated by rSirt1 both in vitro and in vivo. In humans, reduced cardiac expression levels of Sirt1 were associated with higher intramyocardial triacylglycerols and PPARG-related genes. In the db/db mouse model of MCM, chronic exogenous rSirt1 supplementation rescued cardiac function. This was associated with a modulation of the myocardial lipidome and a downregulation of genes involved in lipid metabolism, trafficking, inflammation, and PPARG signaling. These findings were confirmed in the human diabetic myocardium. Treatments that increase Sirt1 levels may represent a promising strategy to prevent myocardial lipid abnormalities and MCM development.

Nootkatone, a Dietary Fragrant Bioactive Compound, Attenuates Dyslipidemia and Intramyocardial Lipid Accumulation and Favorably Alters Lipid Metabolism in a Rat Model of Myocardial Injury: An In Vivo and In Vitro Study.

In the present study, we assessed whether nootkatone (NKT), a sesquiterpene in edible plants, can provide protection against dyslipidemia, intramyocardial lipid accumulation, and altered lipid metabolism in a rat model of myocardial infarction (MI) induced by subcutaneous injections of isoproterenol (ISO, 85 mg/kg) on days 9 and 10. The rats were pre- and co-treated with NKT (10 mg/kg, p.o.) administered daily for 11 days. A significant reduction in the activities of myocardial creatine kinase and lactate dehydrogenase, as well as non-enzymatic antioxidants, and alterations in lipids and lipoproteins, along with a rise in plasma lipid peroxidation and intramyocardial lipid accumulation, were observed in ISO-treated rats. ISO administration induced alterations in the activities of enzymes/expressions that played a significant role in altering lipid metabolism. However, NKT treatment favorably modulated all biochemical and molecular parameters altered by ISO and showed protective effects against oxidative stress, dyslipidemia, and altered lipid metabolism, attributed to its free-radical-scavenging and antihyperlipidemic activities in rats with ISO-induced MI. Additionally, NKT decreased the accumulation of lipids in the myocardium as evidenced from Oil red O staining. Furthermore, the in vitro observations demonstrate the potent antioxidant property of NKT. The present study findings are suggestive of the protective effects of NKT on dyslipidemia and the underlying mechanisms. Based on our findings, it can be suggested that NKT or plants rich in NKT can be promising for use as a phytopharmaceutical or nutraceutical in protecting the heart and correcting lipid abnormalities and dyslipidemia, which are risk factors for ischemic heart diseases.

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.

Acute intramyocardial lipid accumulation in rats does not slow cardiac conduction per se.

Diabetic patients suffer from both cardiac lipid accumulation and an increased risk of arrhythmias and sudden cardiac death. This correlation suggests a link between diabetes induced cardiac steatosis and electrical abnormalities, however, the underlying mechanism remains unknown. We previously showed that cardiac conduction velocity slows in Zucker diabetic fatty rats and in fructose‐fat fed rats, models that both exhibit prominent cardiac steatosis. The aim of this study was to investigate whether acute cardiac lipid accumulation reduces conduction velocity per se. Cardiac lipid accumulation was induced acutely by perfusing isolated rat hearts with palmitate‐glucose buffer, or subacutely by fasting rats overnight. Subsequently, longitudinal cardiac conduction velocity was measured in right ventricular tissue strips, and intramyocardial triglyceride and lipid droplet content was determined by thin layer chromatography and BODIPY staining, respectively. Perfusion with palmitate‐glucose buffer significantly increased intramyocardial triglyceride levels compared to perfusion with glucose (2.16 ± 0.17 (n = 10) vs. 0.92 ± 0.33 nmol/mg WW (n = 9), P < 0.01), but the number of lipid droplets was very low in both groups. Fasting of rats, however, resulted in both significantly elevated intramyocardial triglyceride levels compared to fed rats (3.27 ± 0.43 (n = 10) vs. 1.45 ± 0.24 nmol/mg WW (n = 10)), as well as a larger volume of lipid droplets (0.60 ± 0.13 (n = 10) vs. 0.21 ± 0.06% (n = 10), P < 0.05). There was no significant difference in longitudinal conduction velocity between palmitate‐glucose perfused and control hearts (0.77 ± 0.025 (n = 10) vs. 0.75 m/sec ± 0.029 (n = 9)), or between fed and fasted rats (0.75 ± 0.042 m/sec (n = 10) vs. 0.79 ± 0.047 (n = 10)). In conclusion, intramyocardial lipid accumulation does not slow cardiac longitudinal conduction velocity per se. This is true for both increased intramyocardial triglyceride content, induced by palmitate‐glucose perfusion, and increased intramyocardial triglyceride and lipid droplet content, generated by fasting.

Soluble Receptor for Advanced Glycation End Products: A Protective Molecule against Intramyocardial Lipid Accumulation in Obese Zucker Rats?

Most of the obesity-related complications are due to ectopic fat accumulation. Recently, the activation of the cell-surface receptor for advanced glycation end products (RAGE) has been associated with lipid accumulation in different organs. Nevertheless, the role of RAGE and sRAGE, the soluble form that prevents ligands to activate RAGE, in intramyocardial lipid accumulation is presently unknown. To this aim, we analyzed whether, in obesity, intramyocardial lipid accumulation and lipid metabolism-related transcriptome are related to RAGE and sRAGE. Heart and serum samples were collected from 10 lean (L) and 10 obese (OB) Zucker rats. Oil red staining was used to detect lipids on frozen heart sections. The lipid metabolism-related transcriptome (84 genes) was analyzed by a specific PCR array. Heart RAGE expression was explored by real-time RT-PCR and Western blot analyses. Serum levels of sRAGE (total and endogenous secretory form (esRAGE)) were quantified by ELISA. Genes promoting fatty acid transport, activation, and oxidation in mitochondria/peroxisomes were upregulated in OB hearts. Intramyocardial lipid content did not differ between OB and L rats, as well as RAGE expression. A slight increase in epicardial adipose tissue was observed in OB hearts. Total sRAGE and esRAGE concentrations were significantly higher in OB rats. sRAGE may protect against obesity-induced intramyocardial lipid accumulation by preventing RAGE hyperexpression, therefore allowing lipids to be metabolized. EAT also played a protective role by working as a buffering system that protects the myocardium against exposure to excessively high levels of fatty acids. These observations reinforce the potential role of RAGE pathway as an interesting therapeutic target for obesity-related complications, at least at the cardiovascular level.

1431Modulation of JunD by miR-494-3p causes intra-myocardial lipid accumulation and obesity cardiomyopathy: a study in mice and humans

1431Modulation of JunD by miR-494-3p causes intra-myocardial lipid accumulation and obesity cardiomyopathy: a study in mice and humans

The Sodium-Glucose Cotransporter 2 Inhibitor Dapagliflozin Prevents Cardiomyopathy in a Diabetic Lipodystrophic Mouse Model.

Type 2 diabetes mellitus (T2DM) is a well-recognized independent risk factor for heart failure. T2DM is associated with altered cardiac energy metabolism, leading to ectopic lipid accumulation and glucose overload, the exact contribution of these two parameters remaining unclear. To provide new insight into the mechanism driving the development of diabetic cardiomyopathy, we studied a unique model of T2DM: lipodystrophic Bscl2-/- (seipin knockout [SKO]) mice. Echocardiography and cardiac magnetic resonance imaging revealed hypertrophic cardiomyopathy with left ventricular dysfunction in SKO mice, and these two abnormalities were strongly correlated with hyperglycemia. Surprisingly, neither intramyocardial lipid accumulation nor lipotoxic hallmarks were detected in SKO mice. [18F]Fludeoxyglucose positron emission tomography showed increased myocardial glucose uptake. Consistently, the O-GlcNAcylated protein levels were markedly increased in an SKO heart, suggesting a glucose overload. To test this hypothesis, we treated SKO mice with the hypoglycemic sodium-glucose cotransporter 2 (SGLT2) inhibitor dapagliflozin and the insulin sensitizer pioglitazone. Both treatments reduced the O-GlcNAcylated protein levels in SKO mice, and dapagliflozin successfully prevented the development of hypertrophic cardiomyopathy. Our data demonstrate that glucotoxicity by itself can trigger cardiac dysfunction and that a glucose-lowering agent can correct it. This result will contribute to better understanding of the potential cardiovascular benefits of SGLT2 inhibitors.

Abstract 390: End-stage Human Heart Failure is Characterized by a Deficit in Energetic Lipids in Both Diabetic and Non-diabetic Patients

Introduction: Animal models and human studies have identified increased intramyocardial lipid accumulation and a lipotoxicity hypothesis has been emerging as a mechanism of myocardial dysfunction in diabetes. We have identified a significant decrease in energetic lipids in chronic advanced non-diabetic heart failure. We hypothesized that intramyocardial lipid species would be increased in diabetic as compared to non-diabetic end-stage heart failure patients. Methods: Left ventricular samples procured at the time of orthotopic heart transplantation from non-diabetic (IDCM n=8) and diabetic (DCMDM n=8) patients as well as organ donors with (NFDM) and without a history of diabetes (Donor) were quantitated for lipids with high-resolution mass spectrometry . Stable isotope labeled essential nutrient in cell culture internal standards for acyl-CoAs were generated using [ 13 C 3 15 N 1 ]-pantotheonate in Hepa1c1c7 cells. Results: The lipidomic signature of end-stage failing myocardium marked by a significant decrease in energetic lipids, a decreased myocardial Succinyl CoA (p-value 0.0079 for failing versus non-failing diabetic subjects) and a decreased ratio of [Succinyl CoA]/[Acetyl Coa] consistent with deficient TCA cycling, is indistinguishable in diabetic and non-diabetic patients (Figure 1). Discussion: Despite the known bioenergetic deficits in insulin-resistant diabetes, we have not identified any significant differences between diabetic and non-diabetic subjects in the lipidomic signature of end-stae failing myocardium. Future studies are needed with focused metabolomics to elucidate differences in the diabetic phenotype of human heart failure.

NORMAL DEVELOPMENT OF CONDUCTION VELOCITY IN RATS IS PREVENTED BY FRUCTOSE-FAT FEEDING

Background: Diabetes and metabolic syndrome causes cardiac electrical abnormalities that increase the risk for arrhythmias and sudden death. We have established fructose-fat fed rats (FFFRs) as a prediabetic model, which after 6 weeks of feeding exhibit intramyocardial lipid accumulation, decreased cardiac conduction velocity (CV), and increased risk of ventricular fibrillation following ischemia–reperfusion. CV slowing was not explained by changes in Naþ, Kþ, or gap junction channel function; however, CV may be altered by a depolarized resting membrane potential (RMP). Therefore, the aim of this study was to investigate the time dependence of diet-induced cardiac lipid accumulation, CV disturbances, and changes in RMP and action potential (AP) morphology. Methods: Four-week-old male Sprague-Dawley rats were fed ad libitum with either normal chow or a diet consisting of 60% fat in the chow and 10% fructose in the drinking water. After 1, 3, and 6 weeks of feeding, we measured cardiac CV in right ventricular tissue strips with extracellular electrodes, AP morphology, and RMP using intracellular microelectrodes, and triglyceride content by thin layer chromatography. Results: CV increased from 68.5 0.24 cm/s to 77.7 0.23 cm/s from 1 to 6 weeks in control rats, whereas FFFRs failed to increase CV during the same period (68.9 0.23 cm/s after 1 week vs 67.9 0.23 cm/s after 6 weeks). Intramyocardial triglyceride levels were already significantly higher in FFFRs compared to controls, after 3 weeks of feeding, a time point when CV was not significantly different between controls and FFFRs (70.5 0.15 cm/s vs 70.3 0.20 cm/s). RMP and AP morphology were not different between the 2 groups at any point, except for time to 20% repolarization (APD20), which was significantly longer for FFFRs after 6 weeks (5.69 0.33 ms vs 4.62 0.43 ms). Conclusions: Rats on normal chow increase CV between 1 and 6 weeks of feeding (approximate age 5–6 and 10–11 weeks, respectively), whereas fructose-fat feeding prevents CV development. Lipid accumulation is already present after 3 weeks of fructose-fat feeding, preceding CV slowing. CV slowing could not be explained by changes in RMP or AP upstroke velocity.

Differential Translocation of the Fatty Acid Transporter, FAT/CD36, and the Glucose Transporter, GLUT4, Coordinates Changes in Cardiac Substrate Metabolism During Ischemia and Reperfusion

Fatty acid and glucose transporters translocate between the sarcolemma and intracellular compartments to regulate substrate metabolism acutely. We hypothesised that during ischemia fatty acid translocase (FAT/CD36) would translocate away from the sarcolemma to limit fatty acid uptake when fatty acid oxidation is inhibited. Wistar rat hearts were perfused during preischemia, low-flow ischemia, and reperfusion, using (3)H-substrates for measurement of metabolic rates, followed by metabolomic analysis and subcellular fractionation. During ischemia, there was a 32% decrease in sarcolemmal FAT/CD36 accompanied by a 95% decrease in fatty acid oxidation rates, with no change in intramyocardial lipids. Concomitantly, the sarcolemmal content of the glucose transporter, GLUT4, increased by 90% during ischemia, associated with an 86% increase in glycolytic rates, 45% decrease in glycogen content, and a 3-fold increase in phosphorylated AMP-activated protein kinase. Following reperfusion, decreased sarcolemmal FAT/CD36 persisted, but fatty acid oxidation rates returned to preischemic levels, resulting in a 35% decrease in myocardial triglyceride content. Elevated sarcolemmal GLUT4 persisted during reperfusion; in contrast, glycolytic rates decreased to 30% of preischemic rates, accompanied by a 5-fold increase in intracellular citrate levels and restoration of glycogen content. During ischemia, FAT/CD36 moved away from the sarcolemma as GLUT4 moved toward the sarcolemma, associated with a shift from fatty acid oxidation to glycolysis, while intramyocardial lipid accumulation was prevented. This relocation was maintained during reperfusion, which was associated with replenishing glycogen stores as a priority, occurring at the expense of glycolysis and mediated by an increase in citrate levels.

A mouse model reveals an important role for catecholamine‐induced lipotoxicity in the pathogenesis of stress‐induced cardiomyopathy

Stress-induced cardiomyopathy (SIC), also known as takotsubo cardiomyopathy, is an acute cardiac syndrome with substantial morbidity and mortality. The unique hallmark of SIC is extensive ventricular dysfunction (akinesia) involving apical segments with preserved function in basal segments. Adrenergic overstimulation plays an important role in initiating SIC, but the pathomechanisms involved are unknown. We tested the hypothesis that excessive catecholamines cause perturbation of myocardial lipid metabolism and that cardiac lipotoxicity is responsible for the pathogenesis of SIC. A single dose injection of isoprenaline (ISO; 400 mg/kg) induced SIC-like regional akinesia in mice. Oil red O staining revealed severe lipid accumulation in the heart 2 h post-ISO. Both intramyocardial lipid accumulation and cardiac function were normalized within 1 week post-ISO and no significant amount of fibrosis was detected. We found that gene expression of lipid importers and exporters (ApoB lipoprotein) was depressed 2 h post-ISO. These results were confirmed by similar findings in SIC patients and in ISO/patient serum-stressed HL-1 cardiomyocytes. Moreover, overexpression of ApoB in the heart was found to protect against the development of ISO-induced cardiac toxicity and cardiac dysfunction. We also found that ISO-induced intramyocardial lipid accumulation caused electrophysiological disturbance and stunning in ISO/patient serum-stressed HL-1 cardiomyocytes. The present study demonstrates that lipotoxicity is closely associated with catecholamine-induced myocardial dysfunction, including neurogenic stunning, metabolic stunning, and electrophysiological stunning. Cardiac lipotoxicity may originate from direct inhibition of myocardial ApoB lipoprotein and subsequent decreased lipid export, caused by supraphysiological levels of catecholamines.

Abstract P121: Cardiac Deletion of Aryl Hydrocarbon Nuclear Translocator (Hypoxia-Inducible Factor 1-β) in the Adult Heart Results in Cardiomyopathy

Rongxue Wu, Kusum Chawla, Yoshihiko Ichikawa, Mohsen Granefar Hossein Ardehali Background: Aryl hydrocarbon receptor nuclear translocator (ARNT) is a member of basic helix-loop-helix Per/ARNT/Sim (bHLH-PAS) proteins and serves as a binding partner for a number of other family members. ARNT is also a required dimerization partner of HIF1a. Although HIF1a is known to be required for normal cardiac development, the role of ARNT in basal cardiac function in the adult heart is not known. We hypothesized that ARNT is required for normal cardiac physiology, and its deletion in adult heart results in cardiomyopathy. Methods and Results: The deletion of ARNT gene in the heart of 3 month old mice was achieved by crossing ARNT flox/flox mice with αMHC-MCM (tamoxifen-inducible heart specific Cre) transgenic mice followed by administration of tamoxifen chow. MHC-MCM/ARNT +/+ (WT) littermates were used as a control. The ARNT knock out (KO) mice exhibited enlarged left ventricle with a significant reduction in ejection fraction (KO vs. WT: 35.8 ± 3.6% vs. 61.2 ± 2.8%, n=12, p&lt;0.01) and fractional shortening (KO vs. WT: 18.3 ± 1.5 % vs. 30.1 ± 1.1%, p&lt;0.01), assessed by Echocardiography. Closed-chest catheterization also demonstrated reduced +dP/dt (KO vs. WT: 4355 ± 538 vs. 9426 ± 180 mmHg, p&lt;0.01) and increased left ventricular end diastolic pressure (KO vs. WT: 3.12 ± 1.1 vs. 8.47± 1.2 mmHg, P&lt;0.05) in KO mice but not in WT mice. The worsened cardiac function in the KO mouse heart was associated with increase in ANF and BNP expression, interstitial fibrosis, and apoptosis as determined by TUNEL staining. Furthermore, electron microscopy reveals a variety of degenerative changes and some lipid droplet in the KO hearts, and histological studies demonstrated intramyocardial lipid accumulation in the perivascular area in the KO mouse hearts. Analysis of gene expression in the KO heart revealed up-regulation of peroxisome proliferator-activated receptor alpha. Conclusion: ARNT is essential for the maintenance of structural and functional homeostasis in the adult heart, and its inactivation leads to cardiac contractile dysfunction. Our findings implicate a novel critical transcriptional requirement for ARNT in the maintenance of adult cardiac function.

High free fatty acids level related with cardiac dysfunction in obese rats

AimTo determine whether reducing free fatty acids (FFAs) concentration has a protective effect on cardiac structure and function in high-fat-diet-induced obese rat. MethodsSprague–Dawley rats were randomly divided into normal control, obesity and fenofibrate group. After 8 or 16 weeks, the maximum velocity of myocardial contraction (+dP/dt) and diastole (−dP/dt) were measured. The concentrations of triglyceride, FFAs and angiotensin II were measured. Mitochondrial cytochrome C release and protein levels of NF-kappa B (NF-κB) and inducible nitric oxide synthase (iNOS) in myocardium were analyzed. ResultsThe triglyceride, FFAs and angiotensin II levels were significantly higher in circulating and myocardium in obese rats, associated with lipid deposition, increased mitochondrial cytochrome C release and protein levels of NF-κB and iNOS in myocardium. These alterations were reversed by fenofibrate, in parallel with improvement in +dP/dt, −dP/dt and ultrastructures of myocardial mitochondrion. The cardiac dysfunctions had negative correlation with intramyocardial lipid deposition, FFAs, angiotensin II, and protein levels of NF-κB and iNOS. ConclusionCardiac dysfunction of obese rats could be improved by reducing FFAs level. Intramyocardial lipid accumulation may increase the risk of heart failure in obese rats by increasing renin–angiotensin systems activity and protein levels of NF-κB and iNOS in myocardium.

Early Impairment of Transmural Principal Strains in the Left Ventricular Wall After Short-Term, High-Fat Feeding of Mice Predisposed to Cardiac Steatosis

myocardial lipid accumulation precedes some cardiomyopathies, but little is known of concurrent effects on ventricular mechanics. We tested the hypothesis that intramyocardial lipid accumulation during a short-term, high-fat diet (HFD) affects 2-dimensional strains in the heart. We examined the hearts of nontransgenic (NTG) mice and of transgenic mice predisposed to elevated triacylglyceride (TAG) storage linked to low-level overexpression of peroxisome proliferator activated receptor (PPAR-α). myocardial lipid and transmural principal strains E1 and E2 were determined in vivo with (1)H magnetic resonance spectroscopy/imaging before and after 2 weeks of an HFD in both PPAR-α and NTG littermate mice. Baseline lipid was elevated in PPAR-α compared with NTG mice. An HFD increased mobile lipid by 174% in NTG mice (P<0.05) and by 79% in PPAR-α mice (P<0.05). After an HFD, lipid and TAG were higher in PPAR-α versus NTG mice by 63% and 81%, respectively. However, TAG in PPAR-α mice after an HFD was similar to TAG in PPAR-α mice fed a regular diet, suggesting that the magnetic resonance spectroscopy signal from lipid is not exclusive to TAG. Only at the highest lipid contents, achieved in PPAR-α mice, were strains affected. Endocardial strain was most compromised, with a negative correlation to lipid (P<0.05). a short-term HFD elevated myocardial lipid measures as determined by magnetic resonance spectroscopy, which became dissociated from TAG content in hearts predisposed to cardiac steatosis. The increased lipid was associated with concurrent, transmural reductions in E1 and E2 strains across the left ventricular wall. Strains were attenuated at the highest levels of lipid accumulation, suggesting a threshold response. Thus, 2-dimensional strains are impaired early and without left ventricular diastolic dysfunction, owing to cardiac steatosis.

Western diet changes cardiac acyl-CoA composition in obese rats: a potential role for hepatic lipogenesis

The "lipotoxic footprint" of cardiac maladaptation in diet-induced obesity is poorly defined. We investigated how manipulation of dietary lipid and carbohydrate influenced potential lipotoxic species in the failing heart. In Wistar rats, contractile dysfunction develops at 48 weeks on a high-fat/high-carbohydrate "Western" diet, but not on low-fat/high-carbohydrate or high-fat diets. Cardiac content of the lipotoxic candidates--diacylglycerol, ceramide, lipid peroxide, and long-chain acyl-CoA species--was measured at different time points by high-performance liquid chromatography and biochemical assays, as was lipogenic capacity in the heart and liver by qRT-PCR and radiometric assays. Changes in membranes fluidity were also monitored using fluorescence polarization. We report that Western feeding induced a 40% decrease in myocardial palmitoleoyl-CoA content and a similar decrease in the unsaturated-to-saturated fatty acid ratio. These changes were associated with impaired cardiac mitochondrial membrane fluidity. At the same time, hepatic lipogenic capacity was increased in animals fed Western diet (+270% fatty acid elongase activity compared with high-fat diet), while fatty acid desaturase activity decreased over time. Our findings suggest that dysregulation of lipogenesis is a significant component of heart failure in diet-induced obesity.

Cardiac and metabolic changes in long-term high fructose-fat fed rats with severe obesity and extensive intramyocardial lipid accumulation

Metabolic syndrome and obesity-related diseases are affecting more and more people in the Western world. The basis for an effective treatment of these patients is a better understanding of the underlying pathophysiology. Here, we characterize fructose- and fat-fed rats (FFFRs) as a new animal model of metabolic syndrome. Sprague-Dawley rats were fed a 60 kcal/100 kcal fat diet with 10% fructose in the drinking water. After 6, 12, 18, 24, 36, and 48 wk of feeding, blood pressure, glucose tolerance, plasma insulin, glucose, and lipid levels were measured. Cardiac function was examined by in vivo pressure volume measurements, and intramyocardial lipid accumulation was analyzed by confocal microscopy. Cardiac AMP-activated kinase (AMPK) and hepatic phosphoenolpyruvate carboxykinase (PEPCK) levels were measured by Western blotting. Finally, an ischemia-reperfusion study was performed after 56 wk of feeding. FFFRs developed severe obesity, decreased glucose tolerance, increased serum insulin and triglyceride levels, and an initial increased fasting glucose, which returned to control levels after 24 wk of feeding. The diet had no effect on blood pressure but decreased hepatic PEPCK levels. FFFRs showed significant intramyocardial lipid accumulation, and cardiac hypertrophy became pronounced between 24 and 36 wk of feeding. FFFRs showed no signs of cardiac dysfunction during unstressed conditions, but their hearts were much more vulnerable to ischemia-reperfusion and had a decreased level of phosphorylated AMPK at 6 wk of feeding. This study characterizes a new animal model of the metabolic syndrome that could be beneficial in future studies of metabolic syndrome and cardiac complications.

Myocardial lipid accumulation in patients with pressure-overloaded heart and metabolic syndrome

We evaluated the role of sterol-regulatory element binding protein (SREBP)-1c/peroxisome proliferator activated receptor-gamma (PPARgamma) pathway on heart lipotoxicity in patients with metabolic syndrome (MS) and aortic stenosis (AS). Echocardiographic parameters of heart function and structural alterations of LV specimens were studied in patients with (n = 56) and without (n = 61) MS undergoing aortic valve replacement. Tissues were stained with hematoxylin-eosin (H and E) and oil red O for evidence of intramyocyte lipid accumulation. The specimens were also analyzed with PCR, Western blot, and immunohistochemical analysis for SREBP-1c and PPARgamma. Ejection fraction (EF) was lower in MS compared with patients without MS (P < 0.001); no difference was found in aortic orifice surface among the groups. H and E and oil red O staining of specimens from MS patients revealed several myocytes with intracellular accumulation of lipid, whereas these alterations were not detected in biopsies from patients without MS. Patients without MS have low levels and weak immunostaining of SREBP-1c and PPARgamma in heart specimens. In contrast, strong immunostaining and higher levels of SREBP-1c and PPARgamma were seen in biopsies from the MS patients. Moreover, we evidenced a significative correlation between both SREBP-1c and PPARgamma and EF and intramyocyte lipid accumulation (P < 0.001). SREBP-1c may contribute to heart dysfunction by promoting lipid accumulation within myocytes in MS patients with AS; SREBP-1c may do it by increasing the levels of PPARgamma protein.

Thiazolidinediones may contribute to the intramyocardial lipid accumulation in diabetic myocardium: effects on cardiac function

To the editor: Treatment with thiazolidinedione (TZD), an agonist of peroxisome proliferator-activated receptor-γ (PPARγ), has been associated with a significant increase in heart failure in type 2 diabetic patients.1 These...

CD36 Expression Contributes to Age-Induced Cardiomyopathy in Mice

Cardiac remodeling and impaired cardiac performance in the elderly significantly increase the risk of developing heart disease. Although vascular abnormalities associated with aging contribute to the age-related decline in cardiac function, myocardium-specific events may also be involved. We show that intramyocardial lipid accumulation, as well as a reduction in both fatty acid and glucose oxidation and a subsequent deterioration in cardiac ATP supply, also occurs in aged mice. Consistent with an energetically compromised heart, hearts from aged mice display depressed myocardial performance and cardiac hypertrophy. Associated with this is a dramatic increase in the fatty acid transport protein CD36 in aged hearts compared with young hearts, which suggests that CD36 is a mediator of these multiple metabolic, functional, and structural alterations in the aged heart. In accordance with this, hearts from aged CD36-deficient mice have lower levels of intramyocardial lipids, demonstrate improved mitochondria-derived ATP production, have significantly enhanced function compared with aged wild-type mice, and have a blunted hypertrophic response. These findings provide evidence that CD36 mediates an age-induced cardiomyopathy in mice and suggest that inhibition of CD36 may be an approach for the treatment of the detrimental age-related effects on cardiac performance.