Obesity-induced Cardiac Dysfunction Research Articles

Sex-based differences in short- and longer-term diet-induced metabolic heart disease.

Sex-based differences in the development of obesity-induced cardiometabolic dysfunction are well documented, however, the specific mechanisms are not completely understood. Obesity has been linked to dysregulation of the epitranscriptome, but the role of N6-methyladenosine (m6A) RNA methylation has not been investigated in relation to the sex differences during obesity-induced cardiac dysfunction. In the current study, male and female C57BL/6J mice were subjected to short- and long-term high-fat/high-sucrose (HFHS) diet to induce obesogenic stress. Cardiac echocardiography showed males developed systolic and diastolic dysfunction after 4 mo of diet, but females maintained normal cardiac function despite both sexes being metabolically dysfunctional. Cardiac m6A machinery gene expression was differentially regulated by duration of HFHS diet in male, but not female mice, and left ventricular ejection fraction correlated with RNA machinery gene levels in a sex- and age-dependent manner. RNA-sequencing of cardiac transcriptome revealed that females, but not males may undergo protective cardiac remodeling early in the course of obesogenic stress. Taken together, our study demonstrates for the first time that cardiac RNA methylation machinery genes are regulated early during obesogenic stress in a sex-dependent manner and may play a role in the sex differences observed in cardiometabolic dysfunction.NEW & NOTEWORTHY Sex differences in obesity-associated cardiomyopathy are well documented but incompletely understood. We show for the first time that RNA methylation machinery genes may be regulated in response to obesogenic diet in a sex- and age-dependent manner and levels may correspond to cardiac systolic function. Our cardiac RNA-seq analysis suggests female, but not male mice may be protected from cardiac dysfunction by a protective cardiac remodeling response early during obesogenic stress.

Baicalein ameliorated obesity-induced cardiac dysfunction by regulating the mitochondrial unfolded protein response through NRF2 signaling

BackgroundThe mitochondrial unfolded protein response (UPRmt) is the first line of defense against mitochondrial dysfunction in several diseases. Baicalein, which is an extract of Scutellaria baicalensis Georgi roots, exerts mitoprotective effects on metabolic disorders and cardiovascular diseases. However, it remains unclear whether baicalein alleviates obesity-induced cardiac damage through the UPRmt. PurposeThe present research designed to clarify the role of baicalein in lipotoxicity-induced myocardial apoptosis and investigated the UPRmt-related mechanism. MethodsIn the in vitro experiment, palmitic acid (PA)-treated AC16 cardiomyocytes were established to mimic obesity-induced myocardial injury. After pretreatment of AC16 cells with baicalein, the levels of cell vitality, apoptosis, mitochondrial membrane potential, mitochondrial oxidative stress, and UPRmt-related proteins were determined. Additionally, AC16 cells were treated with ML385 or siRNA to explore the regulation of the UPRmt by NRF2 signaling. In the in vivo experiment, male db/db mice administered with baicalein for 8 weeks were used to validate the effects of baicalein on cardiac damage induced by obesity, the UPRmt, and the NRF2-related pathway. ResultsIn AC16 cardiomyocytes, PA dose-dependently increased the expression of UPRmt markers (HSP60, LONP1, ATF4, and ATF5). This increase was accompanied by enhanced production of mitochondrial ROS, reduced mitochondrial membrane potential, and elevated the expression levels of cytochrome c, cleaved caspase-3, and Bax/Bcl2, eventually leading to cell apoptosis. Baicalein treatment reversed UPRmt activation and mitochondrial damage and impeded mitochondrial-mediated cell apoptosis. Moreover, NRF2 downregulation by its inhibitor ML385 or siRNA diminished baicalein-mediated NRF2 signaling activation and UPRmt inhibition and triggered mitochondrial dysfunction. Additionally, NRF2 deficiency more intensely activated the UPRmt, resulting in mitochondrial oxidative stress and apoptosis of PA-induced cardiomyocytes, thus indicating that NRF2 plays a vital role in mitochondrial homeostasis regulation. In the in vivo study in db/db mice, baicalein inhibited the UPRmt, enhanced the antioxidant capacity, and attenuated cardiac dysfunction through a NRF2-activated pathway. ConclusionTo our best knowledge, these results provide the first insight that baicalein inhibits the UPRmt to induce a protective effect against lipotoxicity-induced mitochondrial damage and cardiomyocyte apoptosis via activating NRF2 signaling and suggest a new role of NRF2 in UPRmt regulation.

Amyloid beta 42 alters cardiac metabolism and impairs cardiac function in male mice with obesity

There are epidemiological associations between obesity and type 2 diabetes, cardiovascular disease and Alzheimer’s disease. The role of amyloid beta 42 (Aβ42) in these diverse chronic diseases is obscure. Here we show that adipose tissue releases Aβ42, which is increased from adipose tissue of male mice with obesity and is associated with higher plasma Aβ42. Increasing circulating Aβ42 levels in male mice without obesity has no effect on systemic glucose homeostasis but has obesity-like effects on the heart, including reduced cardiac glucose clearance and impaired cardiac function. The closely related Aβ40 isoform does not have these same effects on the heart. Administration of an Aβ-neutralising antibody prevents obesity-induced cardiac dysfunction and hypertrophy. Furthermore, Aβ-neutralising antibody administration in established obesity prevents further deterioration of cardiac function. Multi-contrast transcriptomic analyses reveal that Aβ42 impacts pathways of mitochondrial metabolism and exposure of cardiomyocytes to Aβ42 inhibits mitochondrial complex I. These data reveal a role for systemic Aβ42 in the development of cardiac disease in obesity and suggest that therapeutics designed for Alzheimer’s disease could be effective in combating obesity-induced heart failure.

Sleeve gastrectomy improves cardiac function and glucose-lipid metabolism disorder in obese rats induced by a high-fat and high-sugar diet.

Obesity is affecting global health with multiple complications, including cardiac dysfunction. Currently, it is uncertain whether drug therapy should be applied in the early stages of obesity-induced cardiac dysfunction, with weight reduction as the first choice. Sleeve gastrectomy (SG) has been widely used to treat obesity and its complications, showing promising results. However, it remains unclear whether SG can alleviate obesity-induced cardiac dysfunction. A sudden decline in body weight and food intake was observed in both the obese and obese + SG groups, with a higher rate of increase observed in the Obese group. Elevated levels of plasma glucose, serum insulin, and glycated haemoglobin in obese rats were significantly reduced by SG. Markedly increased levels of alanine transaminase, aspartate transaminase, alkaline phosphatase albumin, total cholesterol, triglycerides, and low-density lipoprotein cholesterol levels, elevated values of heart rate, left ventricular end-systolic pressure, left ventricular end-diastolic pressure, systolic pressure, and end diastolic pressure, and decreased value of stroke volume were observed in obese rats, which were sharply reversed by SG. Furthermore, enhanced pathological changes, including inflammatory cell infiltration and loss of cytoplasm striations, enhanced oil red O staining, increased TUNEL-positive cells, upregulated Bax and cleaved-caspase-3, and downregulated Bcl-2, were observed in obese rats, which were notably alleviated by SG. Lastly, the increased levels of relative proteins observed in obese rats were significantly reduced by SG. In conclusion, SG improved cardiac function and glucose-lipid metabolism disorders in obese rats induced by a high-fat and high-sugar diet.

Celastrol confers ferroptosis resistance via AKT/GSK3β signaling in high-fat diet-induced cardiac injury.

Obesity-induced cardiac dysfunction is a severe global disease associated with high dietary fat intake, and its pathogenesis includes inflammation, oxidative stress, and ferroptosis. Celastrol (Cel) is a bioactive compound isolated from the herb Tripterygium wilfordii, which has a protective influence on cardiovascular diseases. In this study, the role of Cel in obesity-induced ferroptosis and cardiac injury was investigated. We found that Cel alleviated ferroptosis induced by Palmitic acid (PA), exhibiting a decrease in the LDH, CK-MB, Ptgs2, and Lipid Peroxidation levels. After cardiomyocytes were treated with additional LY294002 and LiCl, Cel exerted its protective effect through increased AKT/GSK3β phosphorylation and decreased level of lipid peroxidation and Mitochondrial ROS. The systolic left ventricle (LV) dysfunction of obese mice was alleviated via ferroptosis inhibition by elevated p-GSK3β and decreased Mitochondrial ROS under Cel treatment. Moreover, mitochondrial anomalies included swelling and distortion in the myocardium which was relieved with Cel. In conclusion, our results demonstrate that ferroptosis resistance with Cel under HFD conditions targets AKT/GSK3β signaling, which provides novel therapeutic strategies in obesity-induced cardiac injury.

Role of miR-181c in Diet-induced obesity through regulation of lipid synthesis in liver.

We recently identified a nuclear-encoded miRNA (miR-181c) in cardiomyocytes that can translocate into mitochondria to regulate mitochondrial gene mt-COX1 and influence obesity-induced cardiac dysfunction through the mitochondrial pathway. Because liver plays a pivotal role during obesity, we hypothesized that miR-181c might contribute to the pathophysiological complications associated with obesity. Therefore, we used miR-181c/d-/- mice to study the role of miR-181c in hepatocyte lipogenesis during diet-induced obesity. The mice were fed a high-fat (HF) diet for 26 weeks, during which indirect calorimetric measurements were made. Quantitative PCR (qPCR) was used to examine the expression of genes involved in lipid synthesis. We found that miR-181c/d-/- mice were not protected against all metabolic consequences of HF exposure. After 26 weeks, the miR-181c/d-/- mice had a significantly higher body fat percentage than did wild-type (WT) mice. Glucose tolerance tests showed hyperinsulinemia and hyperglycemia, indicative of insulin insensitivity in the miR-181c/d-/- mice. miR-181c/d-/- mice fed the HF diet had higher serum and liver triglyceride levels than did WT mice fed the same diet. qPCR data showed that several genes regulated by isocitrate dehydrogenase 1 (IDH1) were more upregulated in miR-181c/d-/- liver than in WT liver. Furthermore, miR-181c delivered in vivo via adeno-associated virus attenuated the lipogenesis by downregulating these same lipid synthesis genes in the liver. In hepatocytes, miR-181c regulates lipid biosynthesis by targeting IDH1. Taken together, the data indicate that overexpression of miR-181c can be beneficial for various lipid metabolism disorders.

Abstract 14470: Novel Autophagy Mechanisms of NP-6A4 Protection in Heart Disease Induced by Untreated Obesity

Introduction & Hypothesis: Untreated obesity induces insulin resistance and heart disease affecting 42% of the US population. Autophagy, a conserved homeostatic process for cellular quality control, plays a critical role in maintaining health. Heart tissues of obese humans and rodent models show impaired autophagy. Drugs that can regulate autophagy are thus of high clinical significance. We reported recently that NP-6A4, a new peptide agonist of the cardiovascular protective angiotensin receptor AT2R, mitigated obesity-induced cardiac dysfunction and damage in rats with untreated obesity and pre-diabetes. We hypothesized that activation of autophagy by NP-6A4 is involved in NP-6A4-AT2R-induced cardioprotection in untreated obesity. Methods & Results: 7-week old female ZDF rats fed high fat diet (D12468, Research Diet) for 6 weeks were randomized to receive either NP-6A4 (10mg/kg/day), NP6A4+AT2R antagonist PD123319 (PD, 5mg/kg/day) delivered subcutaneously (N=6/group), or vehicle (N=5) for 4 weeks. Echocardiography showed that NP-6A4 reduced abnormal E/A ratio from 2.1 to 1.45 (P<0.006), and isovolumic contraction (P<0.004) and relaxation times (P<0.02), and increased myocardial radial strain (P<0.019) and radial strain rate (P<0.033). PD reversed these effects. Immunohistochemistry (IHC) and Western blot analysis revealed a significant 5.9-fold increase (p<0.0006) in LC3 puncta (Fig. A-B) and 2.2-fold increase (p<0.0008) in lipidated autophagy marker LC3-II (Fig. C) compared to vehicle controls. The autophagy activation by NP-6A4 was not seen with the co-administration of PD (Fig. A-C). Cardiac proteome analysis showed that Sec16a, an important partner of autophagy initiators ULK1/2 is increased in ZDF rat heart by NP-6A4 (2.75 fold; P<0.020), but PD suppressed this effect. Conclusions: We identified NP-6A4’s dual targeting of AT2R and novel autophagy regulation to mitigate cardiac dysfunction induced by untreated obesity in female rats

Curcumin analogue C66 attenuates obesity-induced myocardial injury by inhibiting JNK-mediated inflammation

Obesity has been recognized as a major risk factor for the development of chronic cardiomyopathy, which is associated with increased cardiac inflammation, fibrosis, and apoptosis. We previously developed an anti-inflammatory compound C66, which prevented inflammatory diabetic complications via targeting JNK. In the present study, we have tested the hypothesis that C66 could prevent obesity-induced cardiomyopathy by suppressing JNK-mediated inflammation. High-fat diet (HFD)-induced obesity mouse model and palmitic acid (PA)-challenged H9c2 cells were used to develop inflammatory cardiomyopathy and evaluate the protective effects of C66. Our data demonstrate a protective effect of C66 against obesity-induced cardiac inflammation, cardiac hypertrophy, fibrosis, and dysfunction, overall providing cardio-protection. C66 administration attenuates HFD-induced myocardial inflammation by inhibiting NF-κB and JNK activation in mouse hearts. In vitro, C66 prevents PA-induced myocardial injury and apoptosis in H9c2 cells, accompanied with inhibition against PA-induced JNK/NF-κB activation and inflammation. The protective effect of C66 is attributed to its potential to inhibit JNK activation, which led to reduced pro-inflammatory cytokine production and reduced apoptosis in cardiomyocytes both in vitro and in vivo. In summary, C66 provides significant protection against obesity-induced cardiac dysfunction, mainly by inhibiting JNK activation and JNK-mediated inflammation. Our data indicate that inhibition of JNK is able to provide significant protection against obesity-induced cardiac dysfunction.

Tomato-Oleoresin Anti-Inflammatory Effect Recovers Obesity-Induced Cardiac Dysfunction by Modulating Myocardial Calcium Handling.

Considering the importance of inflammation on obesity-related disorders pathogenesis, including cardiac dysfunction, the interest in natural anti-inflammatory therapeutic strategies has emerged. The lycopene is a carotenoid presents in tomato and red fruits that displays anti-inflammatory properties. In this sense, we will evaluate the anti-inflamma- tory effect of tomato-oleoresin supplementation on obesity- related cardiac dysfunction by modulating myocardial calcium kinetic. Male Wistar rats were initially randomized into 2 experimental groups: (Control, n= 20) or high sugar- fat diet (HSF, n=20) for 20 weeks. At week 20th, once detected the cardiac dysfunction (cardiac remodeling, systolic and diastolic dysfunction) by echocardiography in HSF group, animals were randomly divided to begin the treatment with tomato-oleoresin, performing 4 groups: Control (n= 10); Control + tomato tomato-oleoresin supplementation (Control + Ly, n= 10); HSF (n= 10) or HSF + tomato tomato-oleoresin supplementation (HSF + Ly, n= 10). Tomato oleoresin was mixed with maize oil equivalent to 10mg lycopene/kg body weight (BW) per day and given orally, by gavage, every morning for a 10-week period. It was analyzed cardiac inflammatory parameters by the enzyme-linked immunosorbent assay (ELISA) and in vivo (echocardiography) and in vitro (studying isolated papillary muscles from the left ventricle) cardiac function. The groups were compared by Two-Way analysis of variance (ANOVA). The HSF diet induced cardiac dysfunction (FS(%) C: 60.4±1.3; C+Ly: 60.9±1.3; HSF: 51.7±1.3; HSF+Ly: 59.4±1.4) and inflammation (TNF-α: C:1.88±0.41; C+Ly: 1.93±1.01; HSF: 4.58±1.99; HSF+Ly: 2.03±0.55; IL-6: C:0.58±0.16; C+Ly: 0.40±0.16; HSF: 2.00±0.45; HSF+Ly: 0.53±0.26; MCP-1: C:0.31±0.08; C+Ly: 0.43±0.22; HSF: 1.54±0.32; HSF+Ly: 0.50±0.16). Tomato-oleoresin supplementation improved cardiac remodeling and dysfunction, cardiac inflammation and myocardial calcium kinetic. the anti-inflammatory effect of tomato-oleoresin supplementation treated the obesity-induced cardiac dysfunction by modulating myocardial calcium handling.

Nuclear-mitochondrial communication involving miR-181c plays an important role in cardiac dysfunction during obesity

AimsIn cardiomyocytes, there is microRNA (miR) in the mitochondria that originates from the nuclear genome and matures in the cytoplasm before translocating into the mitochondria. Overexpression of one such miR, miR-181c, can lead to heart failure by stimulating reactive oxygen species (ROS) production and increasing mitochondrial calcium level ([Ca2+]m). Mitochondrial calcium uptake 1 protein (MICU1), a regulatory protein in the mitochondrial calcium uniporter complex, plays an important role in regulating [Ca2+]m. Obesity results in miR-181c overexpression and a decrease in MICU1. We hypothesize that lowering miR-181c would protect against obesity-induced cardiac dysfunction. Methods and resultsWe used an in vivo mouse model of high-fat diet (HFD) for 18 weeks and induced high lipid load in H9c2 cells with oleate-conjugated bovine serum albumin in vitro. We tested the cardioprotective role of lowering miR-181c by using miR-181c/d−/− mice (in vivo) and AntagomiR against miR-181c (in vitro). HFD significantly upregulated heart levels of miR-181c and led to cardiac hypertrophy in wild-type mice, but not in miR-181c/d−/− mice. HFD also increased ROS production and pyruvate dehydrogenase activity (a surrogate for [Ca2+]m), but the increases were alleviated in miR-181c/d−/− mice. Moreover, miR-181c/d−/− mice fed a HFD had higher levels of MICU1 than did wild-type mice fed a HFD, attenuating the rise in [Ca2+]m. Overexpression of miR-181c in neonatal ventricular cardiomyocytes (NMVM) caused increased ROS production, which oxidized transcription factor Sp1 and led to a loss of Sp1, thereby slowing MICU1 transcription. Hence, miR-181c increases [Ca2+]m through Sp1 oxidation and downregulation of MICU1, suggesting that the cardioprotective effect of miR-181c/d−/− results from inhibition of Sp1 oxidation. ConclusionThis study has identified a unique nuclear-mitochondrial communication mechanism in the heart orchestrated by miR-181c. Obesity-induced overexpression of miR-181c increases [Ca2+]m via downregulation of MICU1 and leads to cardiac injury. A strategy to inhibit miR-181c in cardiomyocytes can preserve cardiac function during obesity by improving mitochondrial function. Altering miR-181c expression may provide a pharmacologic approach to improve cardiomyopathy in individuals with obesity/type 2 diabetes.

Thiopental sodium loaded solid lipid nano-particles attenuates obesity-induced cardiac dysfunction and cardiac hypertrophy via inactivation of inflammatory pathway

This work evaluates solid lipid nanoparticles of thiopental sodium against obesity-induced cardiac dysfunction and hypertrophy and explores the possible mechanism of action. TS loaded SLNs were formulated by hot-homogenization and solvent diffusion method. TS-SLNs were scrutinized for entrapment efficiency, drug loading capacity, gastric stability, particle size, in vitro drug release. Mice were feed with the normal chow or high-fat diet for 08 weeks to induce obesity and primary cardiomyocytes. The therapeutic effects of thiopental sodium in the high fat diet (HFD) induced cardiac hypertrophy. Systolic blood pressure (SBP) was estimated at a regular time interval. At the end of the experimental study, systolic pressure left ventricular, LV end-diastolic pressure and rate of increase of LV pressure and antioxidant, apoptosis, cytokines and inflammatory scrutinized. HFD induced group mice exhibited a reduction in the body weight and enhancement of cardiac hypertrophy marker and dose-dependent treatment of thiopental sodium up-regulation the body weight and down-regulated the cardiac hypertrophy. Thiopental sodium significantly (p < .001) dose-dependently altered the antioxidant, biochemical, cardiac parameters and remodeling. Thiopental sodium significantly (p < .001) dose-dependently reduced the SBP. Thiopental sodium altered the apoptosis marker, pro-inflammatory cytokines, inflammatory parameters along with reduced the p38-MAPK level. The cardiac protective effect of thiopental sodium shed light on future therapeutic interventions in obesity and related cardiovascular complications via inflammatory pathway.

3-Weeks of Exercise Training Increases Ischemic-Tolerance in Hearts From High-Fat Diet Fed Mice.

Physical activity is an efficient strategy to delay development of obesity and insulin resistance, and thus the progression of obesity/diabetes-related cardiomyopathy. In support of this, experimental studies using animal models of obesity show that chronic exercise prevents the development of obesity-induced cardiac dysfunction (cardiomyopathy). Whether exercise also improves the tolerance to ischemia-reperfusion in these models is less clear, and may depend on the type of exercise procedure as well as time of initiation. We have previously shown a reduction in ischemic-injury in diet-induced obese mice, when the exercise was started prior to the development of cardiac dysfunction in this model. In the present study, we aimed to explore the effect of exercise on ischemic-tolerance when exercise was initiated after the development obesity-mediated. Male C57BL/6J mice were fed a high-fat diet (HFD) for 20–22 weeks, where they were subjected to high-intensity interval training (HIT) during the last 3 weeks of the feeding period. Sedentary HFD fed and chow fed mice served as controls. Left-ventricular (LV) post-ischemic functional recovery and infarct size were measured in isolated perfused hearts. We also assessed the effect of 3-week HIT on mitochondrial function and myocardial oxygen consumption (MVO2). Sedentary HFD fed mice developed marked obesity and insulin resistance, and demonstrated reduced post-ischemic cardiac functional recovery and increased infarct size. Three weeks of HIT did not induce cardiac hypertrophy and only had a mild effect on obesity and insulin resistance. Despite this, HIT improved post-ischemic LV functional recovery and reduced infarct size. This increase in ischemic-tolerance was accompanied by an improved mitochondrial function as well as reduced MVO2. The present study highlights the beneficial effects of exercise training with regard to improving the ischemic-tolerance in hearts with cardiomyopathy following obesity and insulin resistance. This study also emphasizes the exercise-induced improvement of cardiac energetics and mitochondrial function in obesity/diabetes.

Pyridostigmine alleviates cardiac dysfunction via improving mitochondrial cristae shape in a mouse model of metabolic syndrome

Insulin resistance and autonomic imbalance are important pathological processes in metabolic syndrome–induced cardiac remodeling. Recent studies determined that disruption of mitochondrial cristae shape is associated with myocardial ischemia; however, the change in cristae shape in metabolic syndrome–induced cardiac remodeling remains unclear. This study determined the effect of pyridostigmine (PYR), which reversibly inhibits cholinesterase to improve autonomic imbalance, on high-fat diet (HFD)–induced cardiac insulin resistance and explored the potential effect on the shape of mitochondrial cristae. Feeding of a HFD for 22 weeks led to an irregular and even lysed cristae structure in cardiac mitochondria, which contributed to decreased mitochondrial content and ATP production and increased oxygen species production, ultimately impairing insulin signaling and lipid metabolism. Interestingly, PYR enhanced vagal activity by increasing acetylcholine production and exerted mito-protective effects by activating the LKB1/AMPK/ACC signal pathway. Specifically, PYR upregulated OPA1 and Mfn1/2 expression, promoted the formation of the mitofilin/CHCHD3/Sam50 complex, and decreased p-Drp1 and Fis1 expression, resulting in tight and parallel cristae and increasing cardiac mitochondrial complex subunit expression and ATP generation as well as decreasing release of cytochrome C from mitochondria and oxidative damage. Furthermore, PYR improved glucose and insulin tolerance and insulin-stimulated Akt phosphorylation, decreased lipid toxicity, and ultimately ameliorated HFD-induced cardiac remodeling and dysfunction. In conclusion, PYR prevented cardiac and insulin insensitivity and remodeling by stimulating vagal activity to regulate mitochondrial cristae shape and function in HFD-induced metabolic syndrome in mice. These results provide novel insights for the development of a therapeutic strategy for obesity-induced cardiac dysfunction that targets mitochondrial cristae.

THERAPEUTIC IMPACT OF BERRIES (MORUS ALBA AND MORUS RUBRA) FRUIT EXTRACT IN THE REGRESSION OF HIGH-FAT DIET-INDUCED CARDIAC DYSFUNCTION IN RATS

Objective: The aim of the present study is to investigate the effect of Morus alba (MA) and Morus rubra L. (MR) fruit extract on obesity-induced cardiac dysfunction and fibrosis in cardiac tissue.Methods: Seventy male Wistar albino rats were randomly divided into five groups of ten rats each. MA and MR have been administered for 6 weeks in obese rats induced by high-fat diet (HFD). Adiponectin, glucagon, troponin, plasminogen activator inhibitor, cell adhesion molecules-1 (intracellular and vascular respectively), C-reactive protein, collagen type II and collagen alpha-1 (III) chain, and lipoxygenase activity were also estimated in serum of obese rats. Histopathological investigation of cardiac tissue was carried out.Results: MA and MR treatments significantly normalized cardiac dysfunction biomarkers as well as cardiac fibrosis as examined by histopathological examination with higher percentage of improvement for MR extract.Conclusion: Hence, it could be concluded that MA and MR extracts have useful effects on obesity-associated cardiac diseases through lipid metabolism regulation, cardiac functions and reversed cardiac fibrosis.

Differential effects of Mas receptor deficiency on cardiac function and blood pressure in obese male and female mice.

Angiotensin-(1-7) [ANG-(1-7)] acts at Mas receptors (MasR) to oppose effects of angiotensin II (ANG II). Previous studies demonstrated that protection of female mice from obesity-induced hypertension was associated with increased systemic ANG-(1-7), whereas male obese hypertensive mice exhibited increased systemic ANG II. We hypothesized that MasR deficiency (MasR-/- ) augments obesity-induced hypertension in males and abolishes protection of females. Male and female wild-type (MasR+/+ ) and MasR-/- mice were fed a low-fat (LF) or high-fat (HF) diet for 16 wk. MasR deficiency had no effect on obesity. At baseline, male and female MasR-/- mice had reduced ejection fraction (EF) and fractional shortening than MasR+/+ mice. Male, but not female, HF-fed MasR+/+ mice had increased systolic and diastolic (DBP) blood pressures compared with LF-fed controls. In HF-fed females, MasR deficiency increased DBP compared with LF-fed controls. In contrast, male HF-fed MasR-/- mice had lower DBP than MasR+/+ mice. We quantified cardiac function after 1 mo of HF feeding in males of each genotype. HF-fed MasR-/- mice had higher left ventricular (LV) wall thickness than MasR+/+ mice. Moreover, MasR+/+ , but not MasR-/- , mice displayed reductions in EF from HF feeding that were reversed by ANG-(1-7) infusion. LV fibrosis was reduced in HF-fed MasR+/+ but not MasR-/- ANG-(1-7)-infused mice. These results demonstrate that MasR deficiency promotes obesity-induced hypertension in females. In males, HF feeding reduced cardiac function, which was restored by ANG-(1-7) in MasR+/+ but not MasR-/- mice. MasR agonists may be effective therapies for obesity-associated cardiovascular conditions.NEW & NOTEWORTHY MasR deficiency abolishes protection of female mice from obesity-induced hypertension. Male MasR-deficient obese mice have reduced blood pressure and declines in cardiac function. ANG-(1-7) infusion restores obesity-induced cardiac dysfunction of wild-type, but not MasR-deficient, male mice. MasR agonists may be cardioprotective in obese males and females.

Abstract 13458: Caspase Recruitment Domain-Containing Protein 9 Deficiency Mitigates Obesity-Induced Cardiac Dysfunction

Obesity has become an epidemic and is associated with cardiovascular anomalies. Obesity-induced low-grade chronic inflammation and macrophage infiltration into the heart plays a critical role in the development of cardiac dysfunction. Because the adaptor protein caspase recruitment domain-containing protein 9 (CARD9) regulates the innate immunity in macrophages via activation of pro-inflammatory cytokines, we hypothesized that CARD9 mediates chronic inflammation and plays a detrimental role in obesity-associated cardiac dysfunction. Male C57BL/6 wild-type (WT) and CARD9 knockout (CARD9-/-) mice were fed normal chow (ND, 12% fat) or a Western diet (WD, 45% fat) for 5 months starting at 4 weeks of age. At the end of 5-month WD feeding, cardiac geometry and function were evaluated using echocardiography. Immunofluorescence assay was performed to detect macrophage infiltration in the heart. Heart tissue homogenates, plasma, and supernatants from cultured macrophages were collected to measure the activities of pro-inflammatory cytokines by ELISA kits. Western immunoblotting analyses were performed on isolated peritoneal macrophages and heart tissue to dissect the pro-inflammatory signaling pathways. WD feeding induced insulin resistance and glucose intolerance in the WT mice and the effects were attenuated in the CARD9-/- mice. Myocardial fractional shortening and ejection fraction were significantly compromised in the WD-fed WT mice and CARD9 knockout preserved cardiac function. CARD9 knockout also significantly decreased the number of infiltrated macrophages in the heart. In addition, myocardium-, plasma- and macrophage-derived cytokines IL-6, IL-1β and TNFα were attenuated in the CARD9-/- mice compared to the WT mice. WD feeding resulted in increased protein phosphorylation levels of p38 MAPK in the heart and macrophages which were suppressed in the CARD9-/- mice. Taken together, these results suggest that CARD9 knockout ameliorates obesity-induced cardiac dysfunction, potentially through reduction of macrophage infiltration and suppression of p38 MAPK phosphorylation in the heart.

Partial deletion of ROCK2 protects mice from high-fat diet-induced cardiac insulin resistance and contractile dysfunction.

Obesity is associated with cardiac insulin resistance and contractile dysfunction, which contribute to the development of heart failure. The RhoA-Rho kinase (ROCK) pathway has been reported to modulate insulin resistance, but whether it is implicated in obesity-induced cardiac dysfunction is not known. To test this, wild-type (WT) and ROCK2(+/-) mice were fed normal chow or a high-fat diet (HFD) for 17 wk. Whole body insulin resistance, determined by an insulin tolerance test, was observed in HFD-WT, but not HFD-ROCK2(+/-), mice. The echocardiographically determined myocardial performance index, a measure of global systolic and diastolic function, was significantly increased in HFD-WT mice, indicating a deterioration of cardiac function. However, no change in myocardial performance index was found in hearts from HFD-ROCK2(+/-) mice. Speckle-tracking-based strain echocardiography also revealed regional impairment in left ventricular wall motion in hearts from HFD-WT, but not HFD-ROCK2(+/-), mice. Activity of ROCK1 and ROCK2 was significantly increased in hearts from HFD-WT mice, and GLUT4 expression was significantly reduced. Insulin-induced phosphorylation of insulin receptor substrate (IRS) Tyr(612), Akt, and AS160 was also impaired in these hearts, while Ser(307) phosphorylation of IRS was increased. In contrast, the increase in ROCK2, but not ROCK1, activity was prevented in hearts from HFD-ROCK2(+/-) mice, and cardiac levels of TNFα were reduced. This was associated with normalization of IRS phosphorylation, downstream insulin signaling, and GLUT4 expression. These data suggest that increased activation of ROCK2 contributes to obesity-induced cardiac dysfunction and insulin resistance and that inhibition of ROCK2 may constitute a novel approach to treat this condition.

High-fat diet induces cardiac remodelling and dysfunction: assessment of the role played by SIRT3 loss.

Mitochondrial dysfunction plays an important role in obesity-induced cardiac impairment. SIRT3 is a mitochondrial protein associated with increased human life span and metabolism. This study investigated the functional role of SIRT3 in obesity-induced cardiac dysfunction. Wild-type (WT) and SIRT3 knockout (KO) mice were fed a normal diet (ND) or high-fat diet (HFD) for 16 weeks. Body weight, fasting glucose levels, reactive oxygen species (ROS) levels, myocardial capillary density, cardiac function and expression of hypoxia-inducible factor (HIF)-1α/-2α were assessed. HFD resulted in a significant reduction in SIRT3 expression in the heart. Both HFD and SIRT3 KO mice showed increased ROS formation, impaired HIF signalling and reduced capillary density in the heart. HFD induced cardiac hypertrophy and impaired cardiac function. SIRT3 KO mice fed HFD showed greater ROS production and a further reduction in cardiac function compared to SIRT3 KO mice on ND. Thus, the adverse effects of HFD on cardiac function were not attributable to SIRT3 loss alone. However, HFD did not further reduce capillary density in SIRT3 KO hearts, implicating SIRT3 loss in HFD-induced capillary rarefaction. Our study demonstrates the importance of SIRT3 in preserving heart function and capillary density in the setting of obesity. Thus, SIRT3 may be a potential therapeutic target for obesity-induced heart failure.

Cardiac-specific adipose triglyceride lipase overexpression protects from cardiac steatosis and dilated cardiomyopathy following diet-induced obesity

Although obesity increases the risk of developing cardiomyopathy, the mechanisms underlying the development of this cardiomyopathy are incompletely understood. As obesity is also associated with increased intramyocardial triacylglycerol (TAG) deposition, also referred to as cardiac steatosis, we hypothesized that alterations in myocardial TAG metabolism and excess TAG accumulation contribute to obesity-induced cardiomyopathy. To test if increased TAG catabolism could ameliorate obesity-induced cardiac steatosis and dysfunction, we utilized wild-type (WT) mice and mice with cardiomyocyte-specific overexpression of adipose triglyceride lipase (MHC-ATGL mice), which regulates cardiac TAG hydrolysis. WT and MHC-ATGL mice were fed either regular chow (13.5 kcal% fat) or high fat-high sucrose (HFHS; 45 kcal% fat and 17 kcal% sucrose) diet for 16 weeks to induce obesity and mice were subsequently studied at the physiological, biochemical and molecular level. Obese MHC-ATGL mice were protected from increased intramyocardial TAG accumulation, despite similar increases in body weight and systemic insulin resistance as obese WT mice. Importantly, analysis of in vivo cardiac function using transthoracic echocardiography showed that ATGL overexpression protected from obesity-induced systolic and diastolic dysfunction and ventricular dilatation. Ex vivo working heart perfusions revealed impaired cardiac glucose oxidation following obesity in both WT and MHC-ATGL mice, which was consistent with similar impaired cardiac insulin signaling between genotypes. However, hearts from obese MHC-ATGL mice exhibited reduced reliance on palmitate oxidation when compared with the obese WT, which was accompanied by decreased expression of proteins involved in fatty acid uptake, storage and oxidation in MHC-ATGL hearts. These findings suggest that cardiomyocyte-specific ATGL overexpression was sufficient to prevent cardiac steatosis and decrease fatty acid utilization following HFHS diet feeding, leading to protection against obesity-induced cardiac dysfunction.

Tauroursodeoxycholic Acid Mitigates High Fat Diet-Induced Cardiomyocyte Contractile and Intracellular Ca2+ Anomalies

ObjectivesThe endoplasmic reticulum (ER) chaperone tauroursodeoxycholic acid (TUDCA) has exhibited promises in the treatment of obesity, although its impact on obesity-induced cardiac dysfunction is unknown. This study examined the effect of TUDCA on cardiomyocyte function in high-fat diet-induced obesity.MethodsAdult mice were fed low or high fat diet for 5 months prior to treatment of TUDCA (300 mg/kg. i.p., for 15d). Intraperitoneal glucose tolerance test (IPGTT), cardiomyocyte mechanical and intracellular Ca2+ property, insulin signaling molecules including IRS-1, Akt, AMPK, ACC, GSK-3β, c-Jun, ERK and c-Jun N terminal kinase (JNK) as well as ER stress and intracellular Ca2+ regulatory proteins were examined. Myocardial ultrastructure was evaluated using transmission electron microscopy (TEM).ResultsHigh-fat diet depressed peak shortening (PS) and maximal velocity of shortening/relengthenin as well as prolonged relengthening duration. TUDCA reversed or overtly ameliorated high fat diet-induced cardiomyocyte dysfunction including prolongation in relengthening. TUDCA alleviated high-fat diet-induced decrease in SERCA2a and phosphorylation of phospholamban, increase in ER stress (GRP78/BiP, CHOP, phosphorylation of PERK, IRE1α and eIF2α), ultrastructural changes and mitochondrial permeation pore opening. High-fat diet feeding inhibited phosphorylation of AMPK and promoted phosphorylation of GSK-3β. TUDCA prevented high fat-induced dephosphorylation of AMPK but not GSK-3β. High fat diet promoted phosphorylation of IRS-1 (Ser307), JNK, and ERK without affecting c-Jun phosphorylation, the effect of which with the exception of ERK phosphorylation was attenuated by TUDCA.ConclusionsThese data depict that TUDCA may ameliorate high fat diet feeding-induced cardiomyocyte contractile and intracellular Ca2+ defects through mechanisms associated with mitochondrial integrity, AMPK, JNK and IRS-1 serine phosphorylation.