Differential effects of saturated and unsaturated fatty acid diets on cardiomyocyte apoptosis, adipose distribution, and serum leptin

Apolipoprotein J protects cardiomyocytes from lipid-mediated inflammation and cytotoxicity induced by the epicardial adipose tissue of diabetic patients

Diabetic patients present increased volume and functional alterations in epicardial adipose tissue (EAT). We aimed to analyze EAT from type 2 diabetic patients and the inflammatory and cytotoxic effects induced on cardiomyocytes. Furthermore, we analyzed the cardioprotective role of apolipoprotein J (apoJ). EAT explants were obtained from nondiabetic patients (ND), diabetic patients without coronary disease (DM), and DM patients with coronary disease (DM-C) after heart surgery. Morphological characteristics and gene expression were evaluated. Explants were cultured for 24 h and the content of nonesterified fatty acids (NEFA) and sphingolipid species in secretomes was evaluated by lipidomic analysis. Afterwards, secretomes were added to AC16 human cardiomyocytes for 24 h in the presence or absence of cardioprotective molecules (apoJ and HDL). Cytokine release and apoptosis/necrosis were assessed by ELISA and flow cytometry. The EAT from the diabetic samples showed altered expression of genes related to lipid accumulation, insulin resistance, and inflammation. The secretomes from the DM samples presented an increased ratio of pro/antiatherogenic ceramide (Cer) species, while those from DM-C contained the highest concentration of saturated NEFA. DM and DM-C secretomes promoted inflammation and cytotoxicity on AC16 cardiomyocytes. Exogenous Cer16:0, Cer24:1, and palmitic acid reproduced deleterious effects in AC16 cells. These effects were attenuated by exogenous apoJ. Diabetic secretomes promoted inflammation and cytotoxicity in cardiomyocytes. This effect was exacerbated in the secretomes of the DM-C samples. The increased content of specific NEFA and ceramide species seems to play a key role in inducing such deleterious effects, which are attenuated by apoJ.

Dietary pro-oxidant score (POS) and cardio-metabolic panel among obese individuals: a cross-sectional study

BACKGROUND

Oxidative stress is a disturbance in the natural balance between oxidative and anti-oxidative processes, which is the major effective factor in cardiovascular disorders and metabolic syndrome (MetS), due to the role of pro-oxidants in inducing oxidative stress, and as a result, the occurrence and exacerbation of components of metabolic syndrome and cardiovascular risk factors, this cross-sectional study was conducted with the aim of investigating the relationship between the status of dietary pro-oxidants score (POS) and metabolic parameters including serum lipids, glycemic markers and blood pressure among obese adults.

METHODS

338 individuals with obesity (BMI ≥ 30 kg/m ²), aged between 20 and 50 years were recruited in the present cross-sectional study. A validated food frequency questionnaire (FFQ) was used to determine the dietary pro-oxidant score (POS). Analysis of variance (ANOVA) with Tukey's post-hoc comparisons after adjustment for confounders and multivariable logistic regression analysis were performed to determine the association of cardiometabolic risk factors among the tertiles of POS.

RESULTS

Participants with higher POS had lower levels of body mass index (BMI), weight and waist circumference (WC). There were no significant associations between metabolic parameters including glycemic markers and lipid profile in one-way ANOVA and multivariate multinomial logistic regression models.

CONCLUSIONS

The findings of this study revealed that greater dietary pro-oxidant intake might be associated with lower BMI, body weight, and WC in Iranian obese individuals. Further studies with interventional or longitudinal approaches will help to better elucidate the causality of the observed associations.

Circulating sphingolipids in heart failure

Lack of significant advancements in early detection and treatment of heart failure have precipitated the need for discovery of novel biomarkers and therapeutic targets. Over the past decade, circulating sphingolipids have elicited promising results as biomarkers that premonish adverse cardiac events. Additionally, compelling evidence directly ties sphingolipids to these events in patients with incident heart failure. This review aims to summarize the current literature on circulating sphingolipids in both human cohorts and animal models of heart failure. The goal is to provide direction and focus for future mechanistic studies in heart failure, as well as pave the way for the development of new sphingolipid biomarkers.

Clinical Relevance of lncRNA and Mitochondrial Targeted Antioxidants as Therapeutic Options in Regulating Oxidative Stress and Mitochondrial Function in Vascular Complications of Diabetes

Metabolic imbalances and persistent hyperglycemia are widely recognized as driving forces for augmented cytosolic and mitochondrial reactive oxygen species (ROS) in diabetes mellitus (DM), fostering the development of vascular complications such as diabetic nephropathy, diabetic cardiomyopathy, diabetic neuropathy, and diabetic retinopathy. Therefore, specific therapeutic approaches capable of modulating oxidative milieu may provide a preventative and/or therapeutic benefit against the development of cardiovascular complications in diabetes patients. Recent studies have demonstrated epigenetic alterations in circulating and tissue-specific long non-coding RNA (lncRNA) signatures in vascular complications of DM regulating mitochondrial function under oxidative stress. Intriguingly, over the past decade mitochondria-targeted antioxidants (MTAs) have emerged as a promising therapeutic option for managing oxidative stress-induced diseases. Here, we review the present status of lncRNA as a diagnostic biomarker and potential regulator of oxidative stress in vascular complications of DM. We also discuss the recent advances in using MTAs in different animal models and clinical trials. We summarize the prospects and challenges for the use of MTAs in treating vascular diseases and their application in translation medicine, which may be beneficial in MTA drug design development, and their application in translational medicine.

A Review of Structural Features, Biological Functions and Biotransformation Studies in Adipose Tissues and an Assessment of Progress and Implications

Roles for adipose tissues in energy metabolism, health maintenance and disease onset have been established. Evidence indicates that white, brown and beige fats are quite different in terms of their cellular origin and biological characteristics. These differences are significant in targeting adipocytes to study the pathogenesis and prevention strategies of related diseases. The biotransformations of white, brown and beige fat cells constitute an intriguing topic worthy of further study, and the molecular mechanisms underlying the biotransformations of white, brown and beige fat cells remain to be elucidated. Hence, we herein collected evidence from studies on adipose tissue or adipocytes, and we extracted the structural features, biologic functions, and biotransformations of adipose tissue/adipocytes. The present review aimed to summarize the latest research progress and propose novel research directions with respect to adipose tissue and adipocytes. We posit that this work will provide new insights and opportunities in the effective treatment strategies for obesity, diabetes and other lipid-related diseases. It will also contribute to our knowledge of the basic biologic underpinnings of adipocyte biology.

High Exogenous Antioxidant, Restorative Treatment (Heart) for Prevention of the Six Stages of Heart Failure: The Heart Diet

The exact pathophysiology of heart failure (HF) is not yet known. Western diet, characterized by highly sweetened foods, as well as being rich in fat, fried foods, red meat and processed meat, eggs, and sweet beverages, may cause inflammation, leading to oxidative dysfunction in the cardiac ultra-structure. Oxidative function of the myocardium and how oxidative dysfunction causes physio-pathological remodeling, leading to HF, is not well known. Antioxidants, such as polyphenolics and flavonoids, omega-3 fatty acids, and other micronutrients that are rich in Indo-Mediterranean-type diets, could be protective in sustaining the oxidative functions of the heart. The cardiomyocytes use glucose and fatty acids for the physiological functions depending upon the metabolic requirements of the heart. Apart from toxicity due to glucose, lipotoxicity also adversely affects the cardiomyocytes, which worsen in the presence of deficiency of endogenous antioxidants and deficiency of exogenous antioxidant nutrients in the diet. The high-sugar-and-high-fat-induced production of ceramide, advanced glycation end products (AGE) and triamino-methyl-N-oxide (TMAO) can predispose individuals to oxidative dysfunction and Ca-overloading. The alteration in the biology may start with normal cardiac cell remodeling to biological remodeling due to inflammation. An increase in the fat content of a diet in combination with inducible nitric oxide synthase (NOSi) via N-arginine methyl ester has been found to preserve the ejection fraction in HF. It is proposed that a greater intake of high exogenous antioxidant restorative treatment (HEART) diet, polyphenolics and flavonoids, as well as cessation of red meat intake and egg, can cause improvement in the oxidative function of the heart, by inhibiting oxidative damage to lipids, proteins and DNA in the cell, resulting in beneficial effects in the early stage of the Six Stages of HF. There is an unmet need to conduct cohort studies and randomized, controlled studies to demonstrate the role of the HEART diet in the treatment of HF.

Functional resilience of C57BL/6J mouse heart to dietary fat overload

Molecular mechanisms underlying cardiac dysfunction and subsequent heart failure in diabetic cardiomyopathy are incompletely understood. Initially we intended to test the role of G protein-coupled receptor kinase 2 (GRK2), a potential mediator of cardiac dysfunction in diabetic cardiomyopathy, but found that control animals on HFD did not develop cardiomyopathy. Cardiac function was preserved in both wild-type and GRK2 knockout animals fed high-fat diet as indicated by preserved left ventricular ejection fraction (LVEF) although heart mass was increased. The absence of cardiac dysfunction led us to rigorously evaluate the utility of diet-induced obesity to model diabetic cardiomyopathy in mice. Using pure C57BL/6J animals and various diets formulated with different sources of fat-lard (32% saturated fat, 68% unsaturated fat) or hydrogenated coconut oil (95% saturated fat), we consistently observed left ventricular hypertrophy, preserved LVEF, and preserved contractility measured by invasive hemodynamics in animals fed high-fat diet. Gene expression patterns that characterize pathological hypertrophy were not induced, but a modest induction of various collagen isoforms and matrix metalloproteinases was observed in heart with high-fat diet feeding. PPARα-target genes that enhance lipid utilization such as Pdk4, CD36, AcadL, and Cpt1b were induced, but mitochondrial energetics was not impaired. These results suggest that although long-term fat feeding in mice induces cardiac hypertrophy and increases cardiac fatty acid metabolism, it may not be sufficient to activate pathological hypertrophic mechanisms that impair cardiac function or induce cardiac fibrosis. Thus, additional factors that are currently not understood may contribute to the cardiac abnormalities previously reported by many groups.NEW & NOTEWORTHY Dietary fat overload (DFO) is widely used to model diabetic cardiomyopathy but the utility of this model is controversial. We comprehensively characterized cardiac contractile and mitochondrial function in C57BL6/J mice fed with lard-based or saturated fat-enriched diets initiated at two ages. Despite cardiac hypertrophy, contractile and mitochondrial function is preserved, and molecular adaptations likely limit lipotoxicity. The resilience of these hearts to DFO underscores the need to develop robust alternative models of diabetic cardiomyopathy.

Effect of chain length and saturation of the fatty acids in dietary triglycerides on lipid metabolism in Wistar rats

We investigated the effect of the chain length and the degree of saturation of fatty acids in dietary triglycerides on serum lipid profiles and hepatic lipid metabolism in Wistar rats. Fat component of the basal diet (soybean oil) was replaced with fats with fatty acids of different chain lengths and saturation and the serum lipids were monitored for 150 days. Principal component (PC) analysis of serum lipid components was related to chain length and saturation. The combined effect of chain length and saturation on PC 1 scores was evaluated by multiple regression analysis. The results indicated that average chain length of the fatty acids of triglycerides has a higher influence on the quality of serum lipid parameters than the average degree of saturation. Expression of selected genes responsible for lipid metabolism showed similar trends in medium chain saturated and long chain polyunsaturated diet groups. PRACTICAL APPLICATIONS: Dietary lipids contain a wide range of saturated and unsaturated fatty acids with different chain lengths. Overall contribution of these different fatty acids decides the health effects of the lipids in the diet. Present study shows that the fats with medium chains and higher degree of saturation and fats with long chains and higher degree of unsaturation (lower degree of saturation) affect serum lipid parameters and expression of hepatic genes involved in the lipid metabolism in a similar manner. Such information is important for physicians to plan dietary schemes to improve the nutritional health and manage the noncommunicable diseases.

Aged Monkeys Fed a High-Fat/High-Sugar Diet Recapitulate Metabolic Disorders and Cardiac Contractile Dysfunction

Aged nonhuman primate (NHP) models are of great value for studying the pathology of metabolic heart diseases and developing therapeutic strategies. In this study, aged male cynomolgus monkeys were fed a regular diet or a high-fat/high-sugar diet (HFSD) for 8 months. Metabolic disorders were diagnosed by ¹H-NMR and serum biochemistry, and cardiac function was evaluated by echocardiography. Our results showed that serum metabolic profiles were altered in aged monkeys fed a HFSD, in line with aortic tissue damage, cardiac remodeling, and contractile dysfunction. This aged monkey model significantly increased expression of proinflammatory cytokines and altered expression and phosphorylation of intracellular signaling proteins in the heart, as compared to aged monkeys on a regular diet. Furthermore, the animals demonstrated increased phosphorylation of cardiac myofilament proteins which are causatively associated with decreased myofilament contractility. We conclude that the aged monkey model fed a HFSD exhibits metabolic disorders and cardiac contractile dysfunction.

The antithetic role of ceramide and sphingosine-1-phosphate in cardiac dysfunction

Cardiovascular diseases (CVDs) are the leading cause of death globally and the number of cardiovascular patients, which is estimated to be over 30 million in 2018, represent a challenging issue for the healthcare systems worldwide. Therefore, the identification of novel molecular targets to develop new treatments is an ongoing challenge for the scientific community. In this context, sphingolipids (SLs) have been progressively recognized as potent bioactive compounds that play crucial roles in the modulation of several key biological processes, such as proliferation, differentiation, and apoptosis. Furthermore, SLs involvement in cardiac physiology and pathophysiology attracted much attention, since these molecules could be crucial in the development of CVDs. Among SLs, ceramide and sphingosine-1-phosphate (S1P) represent the most studied bioactive lipid mediators, which are characterized by opposing activities in the regulation of the fate of cardiac cells. In particular, maintaining the balance of the so-called ceramide/S1P rheostat emerged as an important novel therapeutical target to counteract CVDs. Thus, this review aims at critically summarizing the current knowledge about the antithetic roles of ceramide and S1P in cardiomyocytes dysfunctions, highlighting how the modulation of their metabolism through specific molecules, such as myriocin and FTY720, could represent a novel and interesting therapeutic approach to improve the management of CVDs.

Dietary Options for Rodents in the Study of Obesity

Obesity and its associated metabolic diseases are currently a priority research area. The increase in global prevalence at different ages is having an enormous economic and health impact. Genetic and environmental factors play a crucial role in the development of obesity, and diet is one of the main factors that contributes directly to the obesogenic phenotype. Scientific evidence has shown that increased fat intake is associated with the increase in body weight that triggers obesity. Rodent animal models have been extremely useful in the study of obesity since weight gain can easily be induced with a high-fat diet. Here, we review the dietary patterns and physiological mechanisms involved in the dynamics of energy balance. We report the main dietary options for the study of obesity and the variables to consider in the use of a high-fat diet, and assess the progression of obesity and diet-induced thermogenesis.

Changes in Myocardial Metabolism Preceding Sudden Cardiac Death

Heart disease is widely recognized as a major cause of death worldwide and is the leading cause of mortality in the United States. Centuries of research have focused on defining mechanistic alterations that drive cardiac pathogenesis, yet sudden cardiac death (SCD) remains a common unpredictable event that claims lives in every age group. The heart supplies blood to all tissues while maintaining a constant electrical and hormonal feedback communication with other parts of the body. As such, recent research has focused on understanding how myocardial electrical and structural properties are altered by cardiac metabolism and the various signaling pathways associated with it. The importance of cardiac metabolism in maintaining myocardial function, or lack thereof, is exemplified by shifts in cardiac substrate preference during normal development and various pathological conditions. For instance, a shift from fatty acid (FA) oxidation to oxygen-sparing glycolytic energy production has been reported in many types of cardiac pathologies. Compounded by an uncoupling of glycolysis and glucose oxidation this leads to accumulation of undesirable levels of intermediate metabolites. The resulting accumulation of intermediary metabolites impacts cardiac mitochondrial function and dysregulates metabolic pathways through several mechanisms, which will be reviewed here. Importantly, reversal of metabolic maladaptation has been shown to elicit positive therapeutic effects, limiting cardiac remodeling and at least partially restoring contractile efficiency. Therein, the underlying metabolic adaptations in an array of pathological conditions as well as recently discovered downstream effects of various substrate utilization provide guidance for future therapeutic targeting. Here, we will review recent data on alterations in substrate utilization in the healthy and diseased heart, metabolic pathways governing cardiac pathogenesis, mitochondrial function in the diseased myocardium, and potential metabolism-based therapeutic interventions in disease.

Heart structure, serum cholesterol, and adiposity of rats treated with a hypercaloric diet: effectiveness of Citrus sinensis (L.) Osbeck and swimming

Abstract This study evaluated the effects of the herbal medicine red orange (Citrus sinensis (L.) Osbeck) and swimming for 84 days on the animal, heart, and abdominal fat weight and the histomorphometric aspects of heart and total cholesterol of Wistar rats. The rats were divided into seven experimental groups of 12 animals each, consisting of a normocaloric diet (Dn), hypercaloric diet (Dh), normocaloric diet and herbal medicine (DnH), hypercaloric diet and herbal medicine (DhH), normocaloric diet and swimming (DnS), hypercaloric diet and swimming (DhS), and hypercaloric diet, swimming, and herbal medicine (DhSH). The data were analyzed statistically by the Tukey test and considered significant when p<0.05. Groups treated with the normocaloric diet had lower abdominal fat weight. The normocaloric diet and herbal medicine (DnH) provided the smallest thickness of the right ventricle. The hypercaloric diet (Dh) reduced the number of cardiomyocytes and the perimeter of cardiac muscle fibers. Swimming and the red orange extract acted synergistically by reducing the deleterious effects of the hypercaloric diet and increasing the thickness of the cardiac chambers and the number of cardiomyocytes. Only the supplementation with the red orange extract did not reduce abdominal fat in rats treated with a hypercaloric diet. Therefore, red orange alone did not promote beneficial changes in the studied data, but its association with swimming increased the number of cardiomyocytes and thickness of muscle fibers, which could contribute to preventing cardiovascular diseases and maintaining health, as well as the regular swimming and a normocaloric diet, which provided less adiposity.

Comparative analysis of glucose metabolism responses of large yellow croaker Larimichthys crocea fed diet with fish oil and palm oil

In order to study the effects of dietary fatty acid compositions on glucose metabolism, large yellow croaker juveniles Larimichthys crocea (initial weight, 36.80 ± 0.39 g) were fed with two experiment diets for 12 weeks. The two diets contained 6.5% of fish oil (FO) and palm oil (PO), respectively. Results showed that the contents of saturated fatty acids in liver and muscle, levels of glucose, triglyceride (TG), non-esterified fatty acid (NEFA), and leptin in blood were significantly higher in PO group, while the hepatic glycogen and muscle glycogen significantly decreased (P < 0.05). There were no significant differences in blood insulin and adiponectin levels between the two groups (P > 0.05). Compared with the FO group, the expressions of glucokinase (GK), glucose-6-phosphate dehydrogenase, glycogen synthase (GYS), glucose transporter 2 (GLUT2), insulin receptor 1 (IR1), insulin receptor substrate 1 (IRS1), insulin receptor substrate (IRS2), and protein kinase B (AKT2) were significantly decreased, and the expressions of phosphoenolpyruvate carboxykinase (PEPCK) in liver were significantly increased in the PO group. Meanwhile, the expressions of GK, phosphofructokinase, GYS, GLUT4, and insulin receptor 2 (IR2) were significantly reduced, and the expressions PEPCK, fructose-1 and 6-diphosphatase in muscle were significantly increased in the PO group. In conclusion, palm oil in diet could inhibit the utilization of glucose and promote the endogenous glucose production in large yellow croaker by reducing the sensitivity of insulin, so as to increase the blood glucose level.

High calories but not fat content of lard-based diet contribute to impaired mitochondrial oxidative phosphorylation in C57BL/6J mice heart

Purpose

High calorie intake leads to obesity, a global socio-economic and health problem, reaching epidemic proportion in children and adolescents. Saturated and monounsaturated fatty acids from animal (lard) fat are major components of the western-pattern diet and its regular consumption leads to obesity, a risk factor for cardiovascular disease. However, no clear evidence exists whether consumption of diet rich in saturated (SFAs) and monounsaturated (MUFAs) fatty acids has detrimental effects on cardiac structure and energetics primarily due to excessive calories. We, therefore, sought to determine the impact of high calories versus fat content in diet on cardiac structure and mitochondrial energetics.

Methods

Six-week-old C57BL/6J mice were fed with high calorie, high lard fat-based diet (60% fat, HFD), high-calorie and low lard fat-based diet (10% fat, LFD), and lower-calorie and fat diet (standard chow, 12% fat, SCD) for 10 weeks.

Results

The HFD- and LFD-fed mice had higher body weight, ventricular mass and thickness of posterior and septal wall with increased cardiomyocytes diameter compared to the SCD-fed mice. These changes were associated with a reduction in the mitochondrial oxidative phosphorylation (OXPHOS) complexes I and III activity compared to the SCD-fed mice without significant differences between the HFD- and LFD-fed animals. The HFD-fed animals had higher level of malondialdehyde (MDA) than LFD and SCD-fed mice.

Conclusions

We assume that changes in cardiac morphology and selective reduction of the OXPHOS complexes activity observed in the HFD- and LFD-fed mice might be related to excessive calories with additional effect of fat content on oxidative stress.

MicroRNA-21 abrogates palmitate-induced cardiomyocyte apoptosis through caspase-3/NF-κB signal pathways

Objective:

The aim of the study was to investigate the role of microRNA-21 (miR-21) in cardiomyocyte apoptosis and to determine a possible mechanism.

Methods:

H9c2 embryonic rat heart-derived cells were used in the study. Cell viability was determined using the 3-(4.5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, and flow cytometry was used to evaluate cell apoptosis. Reverse transcription-polymerase chain reaction and western blot assays were used to detect mRNA and protein expression of the apoptosis-related proteins and miR-21. ELISA was used to detect reactive oxygen species (ROS).

Results:

Palmitate exposure greatly reduced miR-21 expression in cardiomyocytes. Apoptosis increased when miR-21 was inhibited with or without palmitate exposure. Consistently, reduced apoptosis was observed when miR-21 was overexpressed in cardiomyocytes. Caspase-3 activity was reduced after palmitate exposure. Bcl-2 protein expression was increased in H9c2 cells when transfected with the miR-21 mimic. MiR-21 overexpression alone did not induce ROS or DNA fragmentation; however, in conjunction with palmitate exposure, miR-21 mimic reduced ROS and DNA fragmentation. Moreover, palmitate administration overcame the antioxidant effect of 3 mM N-acetylcysteine to significantly inhibit apoptosis, DNA fragmentation, and caspase-3 activity. The exposure to palmitate greatly reduced p65 and p-p38 expression in the nucleus. A p38 inhibitor had no effect on the expression of Bcl-2 and cleaved caspase-3 in H9c2 cells alone; however, when combined with exposure to palmitate the p38 inhibitor induced Bcl-2 expression and inhibited caspase-3 activity. The p38 inhibitor by itself did not induce apoptosis, ROS production, or DNA fragmentation in H9c2 cells, but when palmitate was included with the p38 inhibitor, apoptosis, ROS production, and DNA fragmentation were reduced.

Conclusion:

miR-21 protects cardiomyocytes from apoptosis that is induced by palmitate through the caspase-3/NF-κB signal pathways.

Cardiac function and intracellular Ca2+ handling proteins are not impaired by high-saturated-fat diet-induced obesity

Obesity is often associated with changes in cardiac function; however, the mechanisms responsible for functional abnormalities have not yet been fully clarified. Considering the lack of information regarding high-saturated-fat diet-induced obesity, heart function, and the proteins involved in myocardial calcium (Ca²⁺) handling, the aim of this study was to test the hypothesis that this dietary model of obesity leads to cardiac dysfunction resulting from alterations in the regulatory proteins of intracellular Ca²⁺ homeostasis. Male Wistar rats were distributed into two groups: control (C, n=18; standard diet) and obese (Ob, n=19; high-saturated-fat diet), which were fed for 33 weeks. Cardiac structure and function were evaluated using echocardiographic and isolated papillary muscle analyses. Myocardial protein expressions of sarcoplasmic reticulum Ca²⁺-ATPase, phospholamban (PLB), PLB serine-16 phosphorylation, PLB threonine-17 phosphorylation, ryanodine receptor, calsequestrin, Na⁺/Ca²⁺ exchanger, and L-type Ca²⁺ channel were assessed by western blot. Obese rats presented 104% increase in the adiposity index (C: 4.5±1.4 vs Ob: 9.2±1.5%) and obesity-related comorbidities compared to control rats. The left atrium diameter (C: 5.0±0.4 vs Ob: 5.5±0.5 mm) and posterior wall shortening velocity (C: 36.7±3.4 vs Ob: 41.8±3.8 mm/s) were higher in the obese group than in the control. The papillary muscle function was similar between the groups at baseline and after inotropic and lusitropic maneuvers. Obesity did not lead to changes in myocardial Ca²⁺ handling proteins expression. In conclusion, the hypothesis was not confirmed, since the high-saturated-fat diet-induced obese rats did not present cardiac dysfunction or impaired intracellular Ca²⁺ handling proteins.

Association between Cardiac Remodeling and Metabolic Alteration in an Experimental Model of Obesity Induced by Western Diet

The high consumption of fat and sugar contributes to the development of obesity and co-morbidities, such as dyslipidemia, hypertension, and cardiovascular disease. The aim of this study was to evaluate the association between dyslipidemia and cardiac dysfunction induced by western diet consumption. Wistar rats were randomly divided into two experimental groups and fed ad libitum for 20 weeks with a control diet (Control, n = 12) or a high-sugar and high-fat diet (HSF, n = 12). The HSF group also received water + sucrose (25%). Evaluations included feed and caloric intake; body weight; plasma glucose; insulin; uric acid; HOMA-IR; lipid profile: [total cholesterol (T-chol), high-density lipoprotein (HDL), non-HDL Chol, triglycerides (TG)]; systolic blood pressure, and Doppler echocardiographic. Compared to the control group, animals that consumed the HSF diet presented higher weight gain, caloric intake, feed efficiency, insulin, HOMA-IR, and glucose levels, and lipid profile impairment (higher TG, T-chol, non-HDL chol and lower HDL). HSF diet was also associated with atrial-ventricular structural impairment and systolic-diastolic dysfunction. Positive correlation was also found among the following parameters: insulin versus estimated LV mass (r = 0.90, p = 0.001); non-HDL versus deceleration time (r = 0.46, p = 0.02); TG versus deceleration time (r = 0.50, p = 0.01). In summary, our results suggest cardiac remodeling lead by western diet is associated with metabolic parameters.

Inhibition of protein kinase R protects against palmitic acid-induced inflammation, oxidative stress, and apoptosis through the JNK/NF-kB/NLRP3 pathway in cultured H9C2 cardiomyocytes

BACKGROUND AND PURPOSE

Double-stranded RNA-dependent protein kinase (PKR) is a critical regulator of apoptosis, oxidative stress, and inflammation under hyperlipidemic and insulin resistance conditions. Saturated free fatty acids, such as palmitic acid (PA), are known inducers of apoptosis in numerous cell types. However, the underlying molecular mechanism is not fully understood. The aim of the present study was to examine the effect of PA on cultured rat H9C2 cardiac myocytes cells and to investigate the PKR mediated harmful effects of PA in vitro in cultured cardiomyocytes.

EXPERIMENTAL APPROACH

PKR expression was determined by immunofluorescence and immunoblotting. Oxidative stress and apoptosis were determined by flow cytometry and assay kits. The expression of different gene markers of apoptosis, oxidative stress, and inflammation were measured by Western blot analysis and reverse transcription polymerase chain reaction.

KEY RESULTS

PKR expression, reactive oxygen species levels as well as apoptosis were increased in PA-treated cultured H9C2 cardiomyocytes. The harmful effects of PA were attenuated by a selective PKR inhibitor, C16. Moreover, we observed that upregulation of c-Jun N-terminal kinase (JNK), nuclear factor-kB (NF-kB) and NACHT, LRR and PYD domains-containing protein 3 (NLRP3) pathways is associated with increased expression of interleukin 6 and tumor necrosis factor-α in PA-treated cardiomyocytes and attenuation by a selective PKR inhibitor.

CONCLUSION AND IMPLICATIONS

Our study reports, for the first time, that PKR-mediated harmful effects of PA in cultured cardiomyocytes via activation of JNK, NF-kB, and NLRP3 pathways. Inhibition of PKR is one of the possible mechanistic approaches to inhibit inflammation, oxidative stress, and apoptosis in lipotoxicity-induced cardiomyocyte damage.

Palmitate-induced lipotoxicity is crucial for the pathogenesis of nonalcoholic fatty liver disease in cooperation with gut-derived endotoxin

Although previous studies have indicated important roles of palmitate, a saturated fatty acid, in the pathogenesis of nonalcoholic fatty liver disease (NAFLD), it remains unclear how palmitate contributes to inflammation and fibrosis in the liver. Administration of palmitate in high fat diet (HFD)-fed but not basal diet (BD)-fed mice resulted in an increase in serum alanine aminotransferase (ALT) levels. Surprisingly, combined administration of very low dose lipopolysaccharide in palmitate-treated mice led to a marked increase in serum ALT levels despite BD-fed conditions. Administration of palmitate alone in BD-fed mice caused inflammatory cell infiltration and liver fibrosis mediated by the toll-like receptor 4 pathway without ALT elevation. In addition, a significant correlation between serum free fatty acid levels and liver fibrosis stage was observed in patients with NAFLD. These results indicate that palmitate may play crucial roles in the pathogenesis of NAFLD in the presence of gut-derived endotoxin.

Molecular mechanism of diabetic cardiomyopathy and modulation of microRNA function by synthetic oligonucleotides

Diabetic cardiomyopathy (DCM) is a chronic complication in individuals with diabetes and is characterized by ventricular dilation and hypertrophy, diastolic dysfunction, decreased or preserved systolic function and reduced ejection fraction eventually resulting in heart failure. Despite being well characterized, the fundamental mechanisms leading to DCM are still elusive. Recent studies identified the involvement of small non-coding small RNA molecules such as microRNAs (miRs) playing a key role in the etiology of DCM. Therefore, miRs associated with DCM represents a new class of targets for the development of mechanistic therapeutics, which may yield marked benefits compared to other therapeutic approaches. Indeed, few miRs currently under active clinical investigation, with many expressing cautious optimism that miRs based therapies will succeed in the coming years. The major caution in using miRs based therapy is the need to improve the stability and specificity following systemic injection, which can be achieved through chemical and structural modification. In this review, we first discuss the established role of miRs in DCM and the advances in miRs based therapeutic strategies for the prevention/treatment of DCM. We next discuss the currently employed chemical modification of miR oligonucleotides and their utility in therapies specifically focusing on the DCM. Finally, we summarize the commonly used delivery system and approaches for assessment of miRNA modulation and potential off-target effects.

Metabolomic Analysis in Heart Failure

It is thought that at least 6,500 low-molecular-weight metabolites exist in humans, and these metabolites have various important roles in biological systems in addition to proteins and genes. Comprehensive assessment of endogenous metabolites is called metabolomics, and recent advances in this field have enabled us to understand the critical role of previously unknown metabolites or metabolic pathways in the cardiovascular system. In this review, we will focus on heart failure and how metabolomic analysis has contributed to improving our understanding of the pathogenesis of this critical condition.

Omega-3 polyunsaturated fatty acids alleviate hepatic steatosis-induced inflammation through Sirt1-mediated nuclear translocation of NF-κB p65 subunit in hepatocytes of large yellow croaker (Larmichthys crocea)

Hepatic steatosis induced inflammation is becoming increasingly prevalent in farmed fish. This study was conducted to investigate the protective effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) against hepatic steatosis-induced inflammation and its potential molecular mechanisms in hepatocyte of large yellow croaker (Larmichthys crocea). We found that the hepatic steatosis-induced inflammation was relieved by ω-3 PUFAs, meanwhile, the Sirt1 activity and transcript expression was increased by ω-3 PUFAs. The increased Sirt1 activity can decrease the hepatic steatosis-induced inflammation. The protective effects of ω-3 PUFAs against hepatic steatosis-induced inflammation was reversed by the treatment with Sirt1 inhibitor EX-527. The nuclear translocation of nuclear transcription factor kappa-B (NF-κB) p65 was significantly decreased after ω-3 PUFAs treatments compared to the palmitic acid stimulation group. The ω-3 PUFAs induced cytoplasm translocation of NF-κB p65 was reversed by EX-527. Together, ω-3 PUFAs alleviate hepatic steatosis-induced inflammation through Sirt1-mediated nuclear translocation of NF-κB p65 subunit in hepatocytes of large yellow croaker. The present study provides important insight into the mechanisms of the protective effects of ω-3 PUFAs, providing theory bases for alleviating the hepatic steatosis induced inflammation of farmed fish, thereby offering great benefits to the aquaculture industry and fish consumers.

Saturated high-fat diet-induced obesity increases adenylate cyclase of myocardial β-adrenergic system and does not compromise cardiac function

Obesity is a worldwide pandemic associated with high incidence of cardiovascular disease. The mechanisms by which the obesity leads cardiac dysfunction are not fully elucidated and few studies have evaluated the relationship between obesity and proteins involved in myocardial β‐adrenergic (βA) system. The purpose of this study was to evaluate the cardiac function and βA pathway components in myocardium of obese rats. Male Wistar rats were distributed into two groups: control (n = 17; standard diet) and obese (n = 17; saturated high‐fat diet) fed for 33 weeks. Nutritional profile and comorbidities were assessed. Cardiac structure and function was evaluated by macroscopic postmortem, echocardiographic and isolated papillary muscle analyzes. Myocardial protein expression of β₁‐ and β₂‐adrenergic receptors, Gαs protein, adenylate cyclase (AC) and protein kinase A (PKA) was performed by Western blot. Cardiac cyclic adenosine monophosphate (cAMP) levels and PKA activity were assessed by ELISA. Obese rats showed increased adiposity index (P < 0.001) and several comorbidities as hypertension, glucose intolerance, insulin resistance, and dyslipidemia compared with control rats. Echocardiographic assessment revealed increased left atrium diameter (C: 4.98 ± 0.38 vs. Ob: 5.47 ± 0.53, P = 0.024) and posterior wall shortening velocity (C: 37.1 ± 3.6 vs. Ob: 41.8 ± 3.8, P = 0.007) in obese group. Papillary muscle evaluation indicated that baseline data and myocardial responsiveness to isoproterenol stimulation were similar between the groups. Protein expression of myocardial AC was higher in obese group than in the control (C: 1.00 ± 0.21 vs. Ob: 1.25 ± 0.10, P = 0.025), whereas the other components were unchanged. These results suggest that saturated high‐fat diet‐induced obesity was not effective in triggering cardiac dysfunction and impair the beta‐adrenergic signaling.

Lipid Use and Misuse by the Heart

The heart utilizes large amounts of fatty acids as energy providing substrates. The physiological balance of lipid uptake and oxidation prevents accumulation of excess lipids. Several processes that affect cardiac function, including ischemia, obesity, diabetes mellitus, sepsis, and most forms of heart failure lead to altered fatty acid oxidation and often also to the accumulation of lipids. There is now mounting evidence associating certain species of these lipids with cardiac lipotoxicity and subsequent myocardial dysfunction. Experimental and clinical data are discussed and paths to reduction of toxic lipids as a means to improve cardiac function are suggested.

Metabolic Remodeling in Diabetic Cardiomyopathy

Diabetes is a risk factor for heart failure and cardiovascular mortality with specific changes to myocardial metabolism, energetics, structure, and function. The gradual impairment of insulin production and signalling in diabetes is associated with elevated plasma fatty acids and increased myocardial free fatty acid uptake and activation of the transcription factor PPARα. The increased free fatty acid uptake results in accumulation of toxic metabolites, such as ceramide and diacylglycerol, activation of protein kinase C, and elevation of uncoupling protein-3. Insulin signalling and glucose uptake/oxidation become further impaired, and mitochondrial function and ATP production become compromised. Increased oxidative stress also impairs mitochondrial function and disrupts metabolic pathways. The diabetic heart relies on free fatty acids (FFA) as the major substrate for oxidative phosphorylation and is unable to increase glucose oxidation during ischaemia or hypoxia, thereby increasing myocardial injury, especially in ageing female diabetic animals. Pharmacological activation of PPARγ in adipose tissue may lower plasma FFA and improve recovery from myocardial ischaemic injury in diabetes. Not only is the diabetic heart energetically-impaired, it also has early diastolic dysfunction and concentric remodelling. The contractile function of the diabetic myocardium negatively correlates with epicardial adipose tissue, which secretes proinflammatory cytokines, resulting in interstitial fibrosis. Novel pharmacological strategies targeting oxidative stress seem promising in preventing progression of diabetic cardiomyopathy, although clinical evidence is lacking. Metabolic agents that lower plasma FFA or glucose, including PPARγ agonism and SGLT2 inhibition, may therefore be promising options.

Exercise mediated protection of diabetic heart through modulation of microRNA mediated molecular pathways

Hyperglycaemia, hypertension, dyslipidemia and insulin resistance collectively impact on the myocardium of people with diabetes, triggering molecular, structural and myocardial abnormalities. These have been suggested to aggravate oxidative stress, systemic inflammation, myocardial lipotoxicity and impaired myocardial substrate utilization. As a consequence, this leads to the development of a spectrum of cardiovascular diseases, which may include but not limited to coronary endothelial dysfunction, and left ventricular remodelling and dysfunction. Diabetic heart disease (DHD) is the term used to describe the presence of heart disease specifically in diabetic patients. Despite significant advances in medical research and long clinical history of anti-diabetic medications, the risk of heart failure in people with diabetes never declines. Interestingly, sustainable and long-term exercise regimen has emerged as an effective synergistic therapy to combat the cardiovascular complications in people with diabetes, although the precise molecular mechanism(s) underlying this protection remain unclear. This review provides an overview of the underlying mechanisms of hyperglycaemia- and insulin resistance-mediated DHD with a detailed discussion on the role of different intensities of exercise in mitigating these molecular alterations in diabetic heart. In particular, we provide the possible role of exercise on microRNAs, the key molecular regulators of several pathophysiological processes.

Fatty old hearts: role of cardiac lipotoxicity in age-related cardiomyopathy

Age-related cardiomyopathy accounts for a significant part of heart failure cases. Imbalance of the energetic equilibrium of the heart along with mitochondrial dysfunction and impaired β-adrenergic receptor signaling contributes in the aggravation of cardiac function in the elderly. In this review article, studies that correlate cardiac aging with lipotoxicity are summarized. The involvement of inhibition of peroxisome proliferator-activated receptor-α, β-adrenergic receptor desensitization, and mitochondrial dysfunction as underlying mechanisms for the lipid-driven age-related cardiomyopathy are presented with the aim to indicate potential therapeutic targets for cardiac aging.

Palmitic Acid Reduces Circulating Bone Formation Markers in Obese Animals and Impairs Osteoblast Activity via C16-Ceramide Accumulation

Obesity and impaired lipid metabolism increase circulating and local fatty acid (FA) levels. Our previous studies showed that a high high-saturated -fat diet induced greater bone loss in mice than a high high-unsaturated-fat diet due to increased osteoclast numbers and activity. The impact of elevated FA levels on osteoblasts is not yet clear. We induced obesity in 4 week old male mice using a palmitic acid (PA)- or oleic acid (OA)-enriched high fat high-fat diet (HFD) (20 % of calories from FA), and compared them to mice on a normal (R) caloric diet (10 % of calories from FA). We collected serum to determine FA and bone metabolism marker levels. Primary osteoblasts were isolated; cultured in PA, OA, or control (C) medium; and assessed for mineralization activity, gene expression, and ceramide levels. Obese animals in the PA and OA groups had significantly lower serum levels of bone formation markers P1NP and OC compared to normal weight animals (*p < 0.001), with the lowest marker levels in animals on an PA-enriched HFD (*p < 0.001). Accordingly, elevated levels of PA significantly reduced osteoblast mineralization activity in vitro (*p < 0.05). Elevated PA intake significantly increased C16 ceramide accumulation. This accumulation was preventable through inhibition of SPT2 (serine palmitoyl transferase 2) using myriocin. Elevated levels of PA reduce osteoblast function in vitro and bone formation markers in vivo. Our findings suggest that saturated PA can compromise bone health by affecting osteoblasts, and identify a potential mechanism through which obesity promotes bone loss.

Different Serum Free Fatty Acid Profiles in NAFLD Subjects and Healthy Controls after Oral Fat Load

BACKGROUND

Free fatty acid (FFA) metabolism can impact on metabolic conditions, such as obesity and nonalcoholic fatty liver disease (NAFLD). This work studied the increase in total FFA shown in NAFLD subjects to possibly characterize which fatty acids significantly accounted for the whole increase.

METHODS

21 patients with NAFLD were selected according to specified criteria. The control group consisted of nine healthy subjects. All subjects underwent an oral standard fat load. Triglycerides; cholesterol; FFA; glucose and insulin were measured every 2 h with the determination of fatty acid composition of FFA.

RESULTS

higher serum FFA levels in NAFLD subjects are mainly due to levels of oleic, palmitic and linoleic acids at different times. Significant increases were shown for docosahexaenoic acid, linolenic acid, eicosatrienoic acid, and arachidonic acid, although this was just on one occasion. In the postprandial phase, homeostatic model assessment HOMA index positively correlated with the ω3/ω6 ratio in NAFLD patients.

CONCLUSIONS

the higher serum levels of FFA in NAFLD subjects are mainly due to levels of oleic and palmitic acids which are the most abundant circulating free fatty acids. This is almost exactly corresponded with significant increases in linoleic acid. An imbalance in the n-3/n-6 fatty acids ratio could modulate postprandial responses with more pronounced effects in insulin-resistant subjects, such as NAFLD patients.

Classification of different degrees of adiposity in sedentary rats

In experimental studies, several parameters, such as body weight, body mass index, adiposity index, and dual-energy X-ray absorptiometry, have commonly been used to demonstrate increased adiposity and investigate the mechanisms underlying obesity and sedentary lifestyles. However, these investigations have not classified the degree of adiposity nor defined adiposity categories for rats, such as normal, overweight, and obese. The aim of the study was to characterize the degree of adiposity in rats fed a high-fat diet using cluster analysis and to create adiposity intervals in an experimental model of obesity. Thirty-day-old male Wistar rats were fed a normal (n=41) or a high-fat (n=43) diet for 15 weeks. Obesity was defined based on the adiposity index; and the degree of adiposity was evaluated using cluster analysis. Cluster analysis allowed the rats to be classified into two groups (overweight and obese). The obese group displayed significantly higher total body fat and a higher adiposity index compared with those of the overweight group. No differences in systolic blood pressure or nonesterified fatty acid, glucose, total cholesterol, or triglyceride levels were observed between the obese and overweight groups. The adiposity index of the obese group was positively correlated with final body weight, total body fat, and leptin levels. Despite the classification of sedentary rats into overweight and obese groups, it was not possible to identify differences in the comorbidities between the two groups.

Characterization of Cyclooxygenase-2 and its induction pathways in response to high lipid diet-induced inflammation in Larmichthys crocea

The present study was conducted to investigate the effects of a high-lipid diet (HLD) on cyclooxygenase (Cox)-2 expression and the signalling pathways related to low-grade inflammation in the large yellow croaker (Larmichthys crocea). An isolated 2508 bp cDNA clone of cox-2 contained an open reading frame spanning 1827 bp encoding a protein with 608 amino acid residues. The over-expression of cox-2 was consistent with the activation of c-Jun N-terminal kinases (JNKs) and p38 mitogen-activated protein kinase (MAPK) in HLD-fed fish. The activation of the activator protein-1 (AP-1) and the nuclear transcription factor kappa-B (NF-κB) signalling pathways in HLD-fed fish and the significant increase of cox-2 promoter-luciferase activity in vitro indicated that AP-1 and NF-κB could combine cox-2 promoter to promote its transcription, respectively. Together, HLD-induced inflammation up-regulates cox-2 expression via JNKs and p38 MAPK-dependent NF-κB and AP-1 pathways. The present study provides important insight into the signal transduction pathways involved in HLD-induced inflammation, which is detrimental to the health and production of fish as well as to the health of fish consumers.

MuRF2 regulates PPARγ1 activity to protect against diabetic cardiomyopathy and enhance weight gain induced by a high fat diet

BACKGROUND

In diabetes mellitus the morbidity and mortality of cardiovascular disease is increased and represents an important independent mechanism by which heart disease is exacerbated. The pathogenesis of diabetic cardiomyopathy involves the enhanced activation of PPAR transcription factors, including PPARα, and to a lesser degree PPARβ and PPARγ1. How these transcription factors are regulated in the heart is largely unknown. Recent studies have described post-translational ubiquitination of PPARs as ways in which PPAR activity is inhibited in cancer. However, specific mechanisms in the heart have not previously been described. Recent studies have implicated the muscle-specific ubiquitin ligase muscle ring finger-2 (MuRF2) in inhibiting the nuclear transcription factor SRF. Initial studies of MuRF2-/- hearts revealed enhanced PPAR activity, leading to the hypothesis that MuRF2 regulates PPAR activity by post-translational ubiquitination.

METHODS

MuRF2-/- mice were challenged with a 26-week 60% fat diet designed to simulate obesity-mediated insulin resistance and diabetic cardiomyopathy. Mice were followed by conscious echocardiography, blood glucose, tissue triglyceride, glycogen levels, immunoblot analysis of intracellular signaling, heart and skeletal muscle morphometrics, and PPARα, PPARβ, and PPARγ1-regulated mRNA expression.

RESULTS

MuRF2 protein levels increase ~20% during the development of diabetic cardiomyopathy induced by high fat diet. Compared to littermate wildtype hearts, MuRF2-/- hearts exhibit an exaggerated diabetic cardiomyopathy, characterized by an early onset systolic dysfunction, larger left ventricular mass, and higher heart weight. MuRF2-/- hearts had significantly increased PPARα- and PPARγ1-regulated gene expression by RT-qPCR, consistent with MuRF2's regulation of these transcription factors in vivo. Mechanistically, MuRF2 mono-ubiquitinated PPARα and PPARγ1 in vitro, consistent with its non-degradatory role in diabetic cardiomyopathy. However, increasing MuRF2:PPARγ1 (>5:1) beyond physiological levels drove poly-ubiquitin-mediated degradation of PPARγ1 in vitro, indicating large MuRF2 increases may lead to PPAR degradation if found in other disease states.

CONCLUSIONS

Mutations in MuRF2 have been described to contribute to the severity of familial hypertrophic cardiomyopathy. The present study suggests that the lack of MuRF2, as found in these patients, can result in an exaggerated diabetic cardiomyopathy. These studies also identify MuRF2 as the first ubiquitin ligase to regulate cardiac PPARα and PPARγ1 activities in vivo via post-translational modification without degradation.

Muscle ring finger-3 protects against diabetic cardiomyopathy induced by a high fat diet

BACKGROUND

The pathogenesis of diabetic cardiomyopathy (DCM) involves the enhanced activation of peroxisome proliferator activating receptor (PPAR) transcription factors, including the most prominent isoform in the heart, PPARα. In cancer cells and adipocytes, post-translational modification of PPARs have been identified, including ligand-dependent degradation of PPARs by specific ubiquitin ligases. However, the regulation of PPARs in cardiomyocytes and heart have not previously been identified. We recently identified that muscle ring finger-1 (MuRF1) and MuRF2 differentially inhibit PPAR activities by mono-ubiquitination, leading to the hypothesis that MuRF3 may regulate PPAR activity in vivo to regulate DCM.

METHODS

MuRF3-/- mice were challenged with 26 weeks 60% high fat diet to induce insulin resistance and DCM. Conscious echocardiography, blood glucose, tissue triglyceride, glycogen levels, immunoblot analysis of intracellular signaling, heart and skeletal muscle morphometrics, and PPARα, PPARβ, and PPARγ1 activities were assayed.

RESULTS

MuRF3-/- mice exhibited a premature systolic heart failure by 6 weeks high fat diet (vs. 12 weeks in MuRF3+/+). MuRF3-/- mice weighed significantly less than sibling-matched wildtype mice after 26 weeks HFD. These differences may be largely due to resistance to fat accumulation, as MRI analysis revealed MuRF3-/- mice had significantly less fat mass, but not lean body mass. In vitro ubiquitination assays identified MuRF3 mono-ubiquitinated PPARα and PPARγ1, but not PPARβ.

CONCLUSIONS

These findings suggest that MuRF3 helps stabilize cardiac PPARα and PPARγ1 in vivo to support resistance to the development of DCM. MuRF3 also plays an unexpected role in regulating fat storage despite being found only in striated muscle.

Sequestration of fatty acids in triglycerides prevents endoplasmic reticulum stress in an in vitro model of cardiomyocyte lipotoxicity

We used human cardiomyocyte-derived cells to create an in vitro model to study lipid metabolism and explored the effects of PPARγ; ACSL1 and ATGL on fatty acid-induced ER stress. Compared to oleate, palmitate treatment resulted in less intracellular accumulation of lipid droplets and more ER stress, as measured by upregulation of CHOP, ATF6 and GRP78 gene expression and phosphorylation of eukaryotic initiation factor 2a (EIF2a). Both ACSL1 and PPARγ adenovirus-mediated expression augmented neutral lipid accumulation and reduced palmitate-induced upregulation of ER stress markers to levels similar to those in the oleate and control treatment groups. This suggests that increased channeling of non-esterified free fatty acids (NEFA) towards storage in the form of neutral lipids in lipid droplets protects against palmitate-induced ER stress. Overexpression of ATGL in cells incubated with oleate-containing medium increased NEFA release and stimulated expression of ER stress markers. Thus, inefficient creation of lipid droplets as well greater release of stored lipids induces ER stress.

Chronic high-fat diet-induced obesity decreased survival and increased hypertrophy of rats with experimental eccentric hypertrophy from chronic aortic regurgitation

Background

The composition of a diet can influence myocardial metabolism and development of left ventricular hypertrophy (LVH). The impact of a high-fat diet in chronic left ventricular volume overload (VO) causing eccentric LVH is unknown. This study examined the effects of chronic ingestion of a high-fat diet in rats with chronic VO caused by severe aortic valve regurgitation (AR) on LVH, function and on myocardial energetics and survival.

Methods

Male Wistar rats were divided in four groups: Shams on control or high-fat (HF) diet (15 rats/group) and AR rats fed with the same diets (ARC (n = 56) and ARHF (n = 32)). HF diet was started one week before AR induction and the protocol was stopped 30 weeks later.

Results

As expected, AR caused significant LV dilation and hypertrophy and this was exacerbated in the ARHF group. Moreover, survival in the ARHF group was significantly decreased compared the ARC group. Although the sham animals on HF also developed significant obesity compared to those on control diet, this was not associated with heart hypertrophy. The HF diet in AR rats partially countered the expected shift in myocardial energy substrate preference usually observed in heart hypertrophy (from fatty acids towards glucose). Systolic function was decreased in AR rats but HF diet had no impact on this parameter. The response to HF diet of different fatty acid oxidation markers as well as the increase in glucose transporter-4 translocation to the plasma membrane compared to ARC was blunted in AR animals compared to those on control diet.

Conclusions

HF diet for 30 weeks decreased survival of AR rats and worsened eccentric hypertrophy without affecting systolic function. The expected adaptation of myocardial energetics to volume-overload left ventricle hypertrophy in AR animals seemed to be impaired by the high-fat diet suggesting less metabolic flexibility.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2261-14-123) contains supplementary material, which is available to authorized users.

Animal models of insulin resistance and heart failure

The incidence of heart failure (HF) and diabetes mellitus is rapidly increasing and is associated with poor prognosis. In spite of the advances in therapy, HF remains a major health problem with high morbidity and mortality. When HF and diabetes coexist, clinical outcomes are significantly worse. The relationship between these two conditions has been studied in various experimental models. However, the mechanisms for this interrelationship are complex, incompletely understood, and have become a matter of considerable clinical and research interest. There are only few animal models that manifest both HF and diabetes. However, the translation of results from these models to human disease is limited, and new models are needed to expand our current understanding of this clinical interaction. In this review, we discuss mechanisms of insulin signaling and insulin resistance, the clinical association between insulin resistance and HF, and its proposed pathophysiologic mechanisms. Finally, we discuss available animal models of insulin resistance and HF and propose requirements for future new models.

Long-term obesity promotes alterations in diastolic function induced by reduction of phospholamban phosphorylation at serine-16 without affecting calcium handling

Few studies have evaluated the relationship between the duration of obesity, cardiac function, and the proteins involved in myocardial calcium (Ca(2+)) handling. We hypothesized that long-term obesity promotes cardiac dysfunction due to a reduction of expression and/or phosphorylation of myocardial Ca(2+)-handling proteins. Thirty-day-old male Wistar rats were distributed into two groups (n = 10 each): control (C; standard diet) and obese (Ob; high-fat diet) for 30 wk. Morphological and histological analyses were assessed. Left ventricular cardiac function was assessed in vivo by echocardiographic evaluation and in vitro by papillary muscle. Cardiac protein expression of sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA2a), calsequestrin, L-type Ca(2+) channel, and phospholamban (PLB), as well as PLB serine-16 phosphorylation (pPLB Ser(16)) and PLB threonine-17 phosphorylation (pPLB Thr(17)) were determined by Western blot. The adiposity index was higher (82%) in Ob rats than in C rats. Obesity promoted cardiac hypertrophy without alterations in interstitial collagen levels. Ob rats had increased endocardial and midwall fractional shortening, posterior wall shortening velocity, and A-wave compared with C rats. Cardiac index, early-to-late diastolic mitral inflow ratio, and isovolumetric relaxation time were lower in Ob than in C. The Ob muscles developed similar baseline data and myocardial responsiveness to increased extracellular Ca(2+). Obesity caused a reduction in cardiac pPLB Ser(16) and the pPLB Ser(16)/PLB ratio in Ob rats. Long-term obesity promotes alterations in diastolic function, most likely due to the reduction of pPLB Ser(16), but does not impair the myocardial Ca(2+) entry and recapture to SR.

Cardioprotective effects of dietary lipids evident in the time-dependent alterations of cardiac function and gene expression following myocardial infarction

We have previously shown that prolonged high–saturated fat feeding (SAT) for 8 weeks after myocardial infarction (MI) improves ventricular function and prevents the metabolic remodeling commonly observed in heart failure. The current study was designed to delineate the interplay between markers of energy metabolism and indices of cardiac remodeling with 2 and 4 weeks of post‐MI SAT in male Wistar rats. By 2 weeks, less remodeling was noted in MI‐SAT evidenced by diminished chamber dilation and greater ejection fraction assessed by echocardiography and hemodynamic measures. In addition, gene expression of energy metabolism targets involved in FA uptake, oxidation, and glucose oxidation regulation was increased in MI‐SAT with respect to MI alone, although no change in PDH phosphorylation was observed. The regulatory kinase, phosphoinositide 3 kinase (Pi3k), was strongly induced by 2 weeks in the MI‐SAT group, although AKT protein content (a primary downstream target of PI3K that affects metabolism) was decreased by both MI and SAT alone, indicating early involvement of cellular signaling pathways in lipid‐mediated cardioprotection. Our results demonstrate that cardioprotection occurs acutely with SAT following MI, with improvement in indices of both cardiac function and fatty acid oxidation, suggesting a mechanistic role for energy metabolism in the beneficial effects of high dietary fat following cardiac injury.

e12019

A diet rich in saturated fats is cardioprotective after myocardial infarction. The cardioprotective effect is noted by 2 weeks and includes functional and genomic changes indicative of a relationship with preservation of metabolic flexibility.

Impairments in mitochondrial palmitoyl-CoA respiratory kinetics that precede development of diabetic cardiomyopathy are prevented by resveratrol in ZDF rats

Alterations in lipid metabolism within the heart may have a causal role in the establishment of diabetic cardiomyopathy; however, this remains equivocal. Therefore, in the current study we determined cardiac mitochondrial bioenergetics in ZDF rats before overt type 2 diabetes and diabetic cardiomyopathy developed. In addition, we utilized resveratrol, a compound previously shown to improve, prevent or reverse cardiac dysfunction in high-fat-fed rodents, as a tool to potentially recover dysfunctions within mitochondria. Fasting blood glucose and invasive left ventricular haemodynamic analysis confirmed the absence of type 2 diabetes and diabetic cardiomyopathy. However, fibrosis was already increased (P < 0.05) ∼70% in ZDF rats at this early stage in disease progression. Assessments of mitochondrial ADP and pyruvate respiratory kinetics in permeabilized fibres from the left ventricle revealed normal electron transport chain function and content. In contrast, the apparent Km to palmitoyl-CoA (P-CoA) was increased (P < 0.05) ∼60%, which was associated with an accumulation of intracellular triacylgycerol, diacylglycerol and ceramide species. In addition, the capacity for mitochondrial reactive oxygen species emission was increased (P < 0.05) ∼3-fold in ZDF rats. The provision of resveratrol reduced fibrosis, P-CoA respiratory sensitivity, reactive lipid accumulation and mitochondrial reactive oxygen species emission rates. Altogether the current data support the supposition that a chronic dysfunction within mitochondrial lipid-supported bioenergetics contributes to the development of diabetic cardiomyopathy, as this was present before overt diabetes or cardiac dysfunction. In addition, we show that resveratrol supplementation prevents these changes, supporting the belief that resveratrol is a potent therapeutic approach for preventing diabetic cardiomyopathy.

Magnolia extract (BL153) protection of heart from lipid accumulation caused cardiac oxidative damage, inflammation, and cell death in high-fat diet fed mice

Magnolia as an herbal material obtained from Magnolia officinalis has been found to play an important role in anti-inflammation, antioxidative stress, and antiapoptosis. This study was designed to investigate the effect of Magnolia extract (BL153) on obesity-associated lipid accumulation, inflammation, oxidative stress, and apoptosis in the heart. C57BL/6 mice were fed a low- (10 kcal% fat) or high-fat (60 kcal% fat) diet for 24 weeks to induce obesity. These mice fed with high-fat diet (HFD) were given a gavage of vehicle, 2.5, 5, or 10 mg/kg body weight BL153 daily. The three doses of BL153 treatment slightly ameliorated insulin resistance without decrease of body weight gain induced by HFD feeding. BL153 at 10 mg/kg slightly attenuated a mild cardiac hypertrophy and dysfunction induced by HFD feeding. Both 5 mg/kg and 10 mg/kg of BL153 treatment significantly inhibited cardiac lipid accumulation measured by Oil Red O staining and improved cardiac inflammation and oxidative stress by downregulating ICAM-1, TNF-α, PAI-1, 3-NT, and 4-HNE. TUNEL staining showed that BL153 treatment also ameliorated apoptosis induced by mitochondrial caspase-3 independent cell death pathway. This study demonstrates that BL153 attenuates HFD-associated cardiac damage through prevention of HFD-induced cardiac lipid accumulation, inflammation, oxidative stress, and apoptosis.

Palmitic acid and DGAT1 deficiency enhance osteoclastogenesis, while oleic acid-induced triglyceride formation prevents it

Both obesity and diabetes mellitus are associated with alterations in lipid metabolism as well as a change in bone homeostasis and osteoclastogenesis. We hypothesized that increased fatty acid levels affect bone health by altering precursor cell differentiation and osteoclast activation. Here we show that palmitic acid (PA, 16:0) enhances receptor activator of NF-κB ligand (RANKL)-stimulated osteoclastogenesis and is sufficient to induce osteoclast differentiation even in the absence of RANKL. TNFα expression is crucial for PA-induced osteoclastogenesis, as shown by increased TNFα mRNA levels in PA-treated cells and abrogation of PA-stimulated osteoclastogenesis by TNFα neutralizing antibodies. In contrast, oleic acid (OA, 18:1) does not enhance osteoclast differentiation, leads to increased intracellular triglyceride accumulation, and inhibits PA-induced osteoclastogenesis. Adenovirus-mediated expression of diacylglycerol acyl transferase 1 (DGAT1), a gene involved in triglyceride synthesis, also inhibits PA-induced osteoclastogenesis, suggesting a protective role of DGAT1 for bone health. Accordingly, Dgat1 knockout mice have larger bone marrow-derived osteoclasts and decreased bone mass indices. In line with these findings, mice on a high-fat PA-enriched diet have a greater reduction in bone mass and structure than mice on a high-fat OA-enriched diet. Thus, we propose that TNFα mediates saturated fatty acid-induced osteoclastogenesis that can be prevented by DGAT activation or supplementation with OA.

Cardiac lipotoxicity: molecular pathways and therapeutic implications

Diabetes and obesity are both associated with lipotoxic cardiomyopathy exclusive of coronary artery disease and hypertension. Lipotoxicities have become a public health concern and are responsible for a significant portion of clinical cardiac disease. These abnormalities may be the result of a toxic metabolic shift to more fatty acid and less glucose oxidation with concomitant accumulation of toxic lipids. Lipids can directly alter cellular structures and activate downstream pathways leading to toxicity. Recent data have implicated fatty acids and fatty acyl coenzyme A, diacylglycerol, and ceramide in cellular lipotoxicity, which may be caused by apoptosis, defective insulin signaling, endoplasmic reticulum stress, activation of protein kinase C, MAPK activation, or modulation of PPARs.

Age-dependent effects of high fat-diet on murine left ventricles: role of palmitate

Obesity-associated heart disease results in myocardial lipid accumulation leading to lipotoxicity. However, recent studies are suggestive of protective effects of high-fat diets (HFD). To determine whether age results in differential changes in diet-induced obesity, we fed young and old (3 and 18 months) male C57Bl/6 mice control diet, low-fat diet (both 10 kcal% fat) or HFD (45 kcal% fat) for 16 weeks, after which we analyzed LV function, mitochondrial changes, and potential modifiers of myocardial structure. HFD or age did not change LV systolic function, although a mildly increased BNP was observed in all old mice. This was associated with increased myocardial collagen, triglyceride, diacylglycerol, and ceramide content as well as higher caspase 3 activation in old mice with highest levels in old HFD mice. Pyruvate-dependent respiration and mitochondrial biogenesis were reduced in all old mice and in young HFD mice. Activation of AMPK, a strong inducer of mitochondrial biogenesis, was reduced in both HFD groups and in old control or LFD mice. Cardiomyocytes from old rats demonstrated significantly reduced AMPK activation, impaired mitochondrial biogenesis, higher ceramide content, and reduced viability after palmitate (C16:0) in vitro, while no major deleterious effects were observed in young cardiomyocytes. Aged but not young cardiomyocytes were unable to respond to higher palmitate with increased fatty acid oxidation. Thus, HFD results in cardiac structural alterations and accumulation of lipid intermediates predominantly in old mice, possibly due to the inability of old cardiomyocytes to adapt to high-fatty acid load.