Diet-induced obesity promotes altered remodeling and exacerbated cardiac hypertrophy following pressure overload

Low-carbohydrate diets containing plant-derived fat but not animal-derived fat ameliorate heart failure

Cardiovascular disease (CVD) is a global health burden in the world. Although low-carbohydrate diets (LCDs) have beneficial effects on CVD risk, their preventive effects remain elusive. We investigated whether LCDs ameliorate heart failure (HF) using a murine model of pressure overload. LCD with plant-derived fat (LCD-P) ameliorated HF progression, whereas LCD with animal-derived fat (LCD-A) aggravated inflammation and cardiac dysfunction. In the hearts of LCD-P-fed mice but not LCD-A, fatty acid oxidation-related genes were highly expressed, and peroxisome proliferator-activated receptor α (PPARα), which regulates lipid metabolism and inflammation, was activated. Loss- and gain-of-function experiments indicated the critical roles of PPARα in preventing HF progression. Stearic acid, which was more abundant in the serum and heart of LCD-P-fed mice, activated PPARα in cultured cardiomyocytes. We highlight the importance of fat sources substituted for reduced carbohydrates in LCDs and suggest that the LCD-P-stearic acid-PPARα pathway as a therapeutic target for HF.

MCC950, a Selective NLRP3 Inhibitor, Attenuates Adverse Cardiac Remodeling Following Heart Failure Through Improving the Cardiometabolic Dysfunction in Obese Mice

Obesity is often accompanied by hypertension. Although a large number of studies have confirmed that NLRP3 inhibitors can improve cardiac remodeling in mice with a normal diet, it is still unclear whether NLRP3 inhibitors can improve heart failure (HF) induced by pressure overload in obese mice. The purpose of this study was to explore the role of MCC950, a selective NLRP3 inhibitor, on HF in obese mice and its metabolic mechanism. Obese mice induced with a 10-week high-fat diet (HFD) were used in this study. After 4 weeks of HFD, transverse aortic constriction (TAC) surgery was performed to induce a HF model. MCC950 (10 mg/kg, once/day) was injected intraperitoneally from 2 weeks after TAC and continued for 4 weeks. After echocardiography examination, we harvested left ventricle tissues and performed molecular experiments. The results suggest that in obese mice, MCC950 can significantly improve cardiac hypertrophy and fibrosis caused by pressure overload. MCC950 ameliorated cardiac inflammation after TAC surgery and promoted M2 macrophage infiltration in the cardiac tissue. MCC950 not only restored fatty acid uptake and utilization by regulating the expression of CD36 and CPT1β but also reduced glucose uptake and oxidation via regulating the expression of GLUT4 and p-PDH. In addition, MCC950 affected the phosphorylation of AKT and AMPK in obese mice with HF. In summary, MCC950 can alleviate HF induced by pressure overload in obese mice via improving cardiac metabolism, providing a basis for the clinical application of NLRP3 inhibitors in obese patients with HF.

Astragaloside IV ameliorates fat metabolism in the liver of ageing mice through targeting mitochondrial activity

Astragaloside IV (AST) is a major bioactive compound of Radix Astragali with medical and health benefits. Previous studies have found that AST can reduce the body weights of high-fat diet fed mice. However, the effect of AST on fat metabolism of ageing mice is unclear. In this study, naturally ageing mice were administered intragastrically with AST at 30 mg/kg/day (ageing + AST-L group) and 90 mg/kg/day (ageing + AST-H group) for 16-20 months. Adult (4 months old) and ageing mice were given 1% sodium carboxyl methylcellulose as vehicle. Energy metabolism-related biological parameters of living mice were examined. Moreover, mRNA and protein levels of key enzymes/proteins involved in triglyceride (TG) lipolysis, fatty acid β-oxidation (FAO), ketone body (KB) production and mitochondrial respiratory chain were also examined after sacrifice. Results demonstrated that treatment with AST significantly reduced body weight, white fat and liver/body weight ratio of ageing mice, significantly reduced serum/hepatic TG levels, respiratory quotient, promoted fatty acid mobilization in white adipose tissue, mitochondrial FAO and KB production and mitochondrial biosynthesis/functions in the liver of ageing mice. AST also up-regulated the expression of phosphorylated AMP-activated protein kinase, acetyl-CoA carboxylase, acetyl-coenzyme A synthetase, carnitine palmitoyltransferase 1a/1b, enoyl coenzyme A hydratase-short chain, acyl-CoA dehydrogenase medium chain and mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase-2 involved in fat metabolism. These results indicated that mitochondrial activity could be the target of AST to treat abnormal fat metabolism during ageing.

Characterization of Exercise-Induced Myocardium Growth Using Finite Element Modeling and Bayesian Optimization

Cardiomyocyte growth can occur in both physiological (exercised-induced) and pathological (e.g., volume overload and pressure overload) conditions leading to left ventricular (LV) hypertrophy. Studies using animal models and histology have demonstrated the growth and remodeling process at the organ level and tissue-cellular level, respectively. However, the driving factors of growth and the mechanistic link between organ, tissue, and cellular growth remains poorly understood. Computational models have the potential to bridge this gap by using constitutive models that describe the growth and remodeling process of the myocardium coupled with finite element (FE) analysis to model the biomechanics of the heart at the organ level. Using subject-specific imaging data of the LV geometry at two different time points, an FE model can be created with the inverse method to characterize the growth parameters of each subject. In this study, we developed a framework that takes in vivo cardiac magnetic resonance (CMR) imaging data of exercised porcine model and uses FE and Bayesian optimization to characterize myocardium growth in the transverse and longitudinal directions. The efficacy of this framework was demonstrated by successfully predicting growth parameters of 18 synthetic LV targeted masks which were generated from three LV porcine geometries. The framework was further used to characterize growth parameters in 4 swine subjects that had been exercised. The study suggested that exercise-induced growth in swine is prone to longitudinal cardiomyocyte growth (58.0 ± 19.6% after 6 weeks and 79.3 ± 15.6% after 12 weeks) compared to transverse growth (4.0 ± 8.0% after 6 weeks and 7.8 ± 9.4% after 12 weeks). This framework can be used to characterize myocardial growth in different phenotypes of LV hypertrophy and can be incorporated with other growth constitutive models to study different hypothetical growth mechanisms.

Cardiac Energy Metabolism in Heart Failure

Alterations in cardiac energy metabolism contribute to the severity of heart failure. However, the energy metabolic changes that occur in heart failure are complex and are dependent not only on the severity and type of heart failure present but also on the co-existence of common comorbidities such as obesity and type 2 diabetes. The failing heart faces an energy deficit, primarily because of a decrease in mitochondrial oxidative capacity. This is partly compensated for by an increase in ATP production from glycolysis. The relative contribution of the different fuels for mitochondrial ATP production also changes, including a decrease in glucose and amino acid oxidation, and an increase in ketone oxidation. The oxidation of fatty acids by the heart increases or decreases, depending on the type of heart failure. For instance, in heart failure associated with diabetes and obesity, myocardial fatty acid oxidation increases, while in heart failure associated with hypertension or ischemia, myocardial fatty acid oxidation decreases. Combined, these energy metabolic changes result in the failing heart becoming less efficient (ie, a decrease in cardiac work/O₂ consumed). The alterations in both glycolysis and mitochondrial oxidative metabolism in the failing heart are due to both transcriptional changes in key enzymes involved in these metabolic pathways, as well as alterations in NAD redox state (NAD⁺ and nicotinamide adenine dinucleotide levels) and metabolite signaling that contribute to posttranslational epigenetic changes in the control of expression of genes encoding energy metabolic enzymes. Alterations in the fate of glucose, beyond flux through glycolysis or glucose oxidation, also contribute to the pathology of heart failure. Of importance, pharmacological targeting of the energy metabolic pathways has emerged as a novel therapeutic approach to improving cardiac efficiency, decreasing the energy deficit and improving cardiac function in the failing heart.

Mechanisms of Chronic Metabolic Stress in Arrhythmias

Cardiac arrhythmias are responsible for many cardiovascular disease-related deaths worldwide. While arrhythmia pathogenesis is complex, there is increasing evidence for metabolic causes. Obesity, diabetes, and chronically consuming high-fat foods significantly increase the likelihood of developing arrhythmias. Although these correlations are well established, mechanistic explanations connecting a high-fat diet (HFD) to arrhythmogenesis are incomplete, although oxidative stress appears to be critical. This review investigates the metabolic changes that occur in obesity and after HFD. Potential therapies to prevent or treat arrhythmias are discussed, including antioxidants.

KLF15 is a protective regulatory factor of heart failure induced by pressure overload

The aim of the present study was to investigate the protective effect of Kruppel‑like factor 15 (KLF15) overexpression on heart failure (HF) induced by left ventricular (LV) pressure overload in mice. Wild‑type (WT) mice and cardiac‑specific KLF15‑overexpressed transgenic (TG) mice were selected as research subjects, and an LV pressure overload model was constructed by ascending aortic constriction surgery. Changes in cardiac morphology and function, and ultrastructure and molecular expression were observed via M‑mode echocardiography, histological and immunohistochemical staining, ELISA and western blotting at 2 and 6 weeks of LV overload. WT and TG mice subjected to 2 weeks of overload displayed adaptive LV hypertrophy characterized by ventricular thickness, cardiomyocyte size, ejection fraction and fractional shortening of heart‑lung weight ratio and KLF15, and increases in vascular endothelial growth factor (VEGF) expression without other pathological changes. WT mice subjected to 6 weeks of overload displayed enlargement of the LV chamber, severe interstitial remodeling, and HW/LW, cardiac capillary and heart function decline, accompanied by downregulated expression of KLF15 and VEGF, and upregulated expression of connective tissue growth factor, phosphorylated p38 (p‑p38) and phosphorylated Smad3 (p‑Smad3). In contrast, TG mice exhibited improved resistance to 6 weeks of overload and a slighter molecular expression response compared with WT mice. KLF15 was revealed to be a critical factor regulating the expression of CTGF, VEGF, p‑p38 and p‑Smad3, and could alleviate the progression from adaptive LV hypertrophy to decompensatory cardiac insufficiency.

Huoxue Qianyang decoction ameliorates cardiac remodeling in obese spontaneously hypertensive rats in association with ATF6-CHOP endoplasmic reticulum stress signaling pathway regulation

OBJECTIVE

Endoplasmic reticulum (ER) stress is involved in hypertension related cardiac remodeling. We aimed to evaluate the effects of Huoxue Qianyang (HXQY) decoction on cardiac remodeling in obese spontaneously hypertensive rats (SHRs), and explore its impacts on the activating transcription factor 6 (ATF6)-C/EBP homologous protein (CHOP) ER stress signaling pathway.

METHODS

Twenty-seven obese SHRs were randomly divided into Obese SHR, Obese SHR + HXQY and Obese SHR + Valsartan groups, and treated with the indicated drugs for 8 weeks. Nine age-matched male SHRs were used as controls. Systolic blood pressure (SBP), body weight (BW), and the left ventricular mass index (LVMI) were measured weekly or at end point. Then, angiotensin II (Ang II), fasting glucose (FPG) and fasting insulin (FIN), total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C) and triglyceride (TG) levels were evaluated with commercial kits. Apoptotic cardiomyocytes were detected by the terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method. The expression levels of GRP78, ATF6, PERK/pPERK and CHOP were assessed by quantitative PCR and Western blot.

RESULTS

Treatment with HXQY decoction resulted in significantly reduced SBP, BW, LVMI, Ang II, TC and LDL-C levels, as well as the homeostasis model assessment of insulin resistance (HOMA-IR) score in obese SHRs. Apoptosis in heart tissues of obese SHRs was significantly attenuated after HXQY decoction administration, paralleling reduced expression of GRP78, ATF6, PERK/pPERK and CHOP at both mRNA and protein levels.

CONCLUSION

Cardiac remodeling in obese SHRs is ameliorated by intervention with HXQY decoction in association with inhibited ATF6-CHOP ER stress signaling pathway.

Modeling heart failure risk in diabetes and kidney disease: limitations and potential applications of transverse aortic constriction in high-fat-fed mice

There is an increased incidence of heart failure in individuals with diabetes mellitus (DM). The coexistence of kidney disease in DM exacerbates the cardiovascular prognosis. Researchers have attempted to combine the critical features of heart failure, using transverse aortic constriction, with DM in mice, but variable findings have been reported. Furthermore, kidney outcomes have not been assessed in this setting; thus its utility as a model of heart failure in DM and kidney disease is unknown. We generated a mouse model of obesity, hyperglycemia, and mild kidney pathology by feeding male C57BL/6J mice a high-fat diet (HFD). Cardiac pressure overload was surgically induced using transverse aortic constriction (TAC). Normal diet (ND) and sham controls were included. Heart failure risk factors were evident at 8-wk post-TAC, including increased left ventricular mass (+49% in ND and +35% in HFD), cardiomyocyte hypertrophy (+40% in ND and +28% in HFD), and interstitial and perivascular fibrosis (Masson's trichrome and picrosirius red positivity). High-fat feeding did not exacerbate the TAC-induced cardiac outcomes. At 11 wk post-TAC in a separate mouse cohort, echocardiography revealed reduced left ventricular size and increased left ventricular wall thickness, the latter being evident in ND mice only. Systolic function was preserved in the TAC mice and was similar between ND and HFD. Thus combined high-fat feeding and TAC in mice did not model the increased incidence of heart failure in DM patients. This model, however, may mimic the better cardiovascular prognosis seen in overweight and obese heart failure patients.

Astragaloside IV alleviates heart failure via activating PPARα to switch glycolysis to fatty acid β-oxidation

In heart failure (HF), energy metabolism pathway in cardiac muscle changes from fatty acid β-oxidation to glycolysis. However, the exact mechanism is unknown. Sarcoendoplasmic reticulum Ca²⁺α ATPase (SERCA) expression is downregulated and mitochondrial function is reduced in HF, perhaps partly due to a substantially reduced energy supply for excitation–contraction coupling resulting from a lower fatty acid β-oxidation rate. We investigated whether Astragaloside IV can activate peroxisome proliferator-activated receptor alpha (PPARα) to stimulate fatty acid β-oxidation and increase cardiac energy production, improving mitochondrial function and the efficiency of SERCA in HF. In pressure overload-induced HF mice and isolated hypertrophic myocardial cells, fatty acid β-oxidation and heart function were substantially strengthened following Astragaloside IV treatment, as demonstrated by the increased expression of PPARα and SERCA2a. In vitro, Astragaloside IV regulated energy metabolism by increasing ATP production and enhancing mitochondrial function, attributable to increased oxygen consumption and slightly increased mitochondrial Ca²⁺ uptake. In HF, Astragaloside IV switched glycolysis to fatty acid β-oxidation, as confirmed by reduced anaerobic glycolysis and an increased oxygen consumption ratio. These results suggest that Astragaloside IV can stimulate fatty acid β-oxidation and improve mitochondrial function, which may present a novel cardioprotective treatment that inhibits the progress of HF.

Complex Energy Metabolic Changes in Heart Failure With Preserved Ejection Fraction and Heart Failure With Reduced Ejection Fraction

Alterations in cardiac energy metabolism contribute to the severity of heart failure. However, the energy metabolic changes that occur in heart failure are complex, and are dependent not only on the severity and type of heart failure present, but also on the coexistence of common comorbidities such as obesity and type 2 diabetes. In this article we review the cardiac energy metabolic changes that occur in heart failure. An emphasis is made on distinguishing the differences in cardiac energy metabolism between heart failure with preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF) and in clarifying the common misconceptions surrounding the fate of fatty acids and glucose in the failing heart. The major key points from this article are: (1) mitochondrial oxidative capacity is reduced in HFpEF and HFrEF; (2) fatty acid oxidation is increased in HFpEF and reduced in HFrEF (however, oxidative metabolism of fatty acids in HFrEF still exceeds that of glucose); (3) glucose oxidation is decreased in HFpEF and HFrEF; (4) there is an uncoupling between glucose uptake and oxidation in HFpEF and HFrEF, resulting in an increased rate of glycolysis; (5) ketone body oxidation is increased in HFrEF, which might further reduce fatty acid and glucose oxidation; and finally, (6) branched chain amino acid oxidation is impaired in HFrEF. The understanding of these changes in cardiac energy metabolism in heart failure are essential to allow the development of metabolic modulators in the treatment of heart failure.

Mechanisms of Chinese Medicine Xinmailong's protection against heart failure in pressure-overloaded mice and cultured cardiomyocytes

Patients with heart failure (HF) have high mortality and mobility. Xinmailong (XML) injection, a Chinese Medicine, is clinically effective in treating HF. However, the mechanism of XML's effectiveness on HF was unclear, and thus, was the target of the present study. We created a mouse model of pressure-overload-induced HF with transverse aortic constriction (TAC) surgery and compared among 4 study groups: SHAM (n = 10), TAC (n = 12), MET (metoprolol, positive drug treatment, n = 7) and XML (XML treatment, n = 14). Dynamic changes in cardiac structure and function were evaluated with echocardiography in vivo. In addition, H9C2 rat cardiomyocytes were cultured in vitro and the phosphorylation of ERK1/2, AKT, GSK3β and protein expression of GATA4 in nucleus were detected with Western blot experiment. The results showed that XML reduced diastolic thickness of left ventricular posterior wall, increased ejection fraction and fraction shortening, so as to inhibit HF at 2 weeks after TAC. Moreover, XML inhibited the phosphorylation of ERK1/2, AKT and GSK3β, subsequently inhibiting protein expression of GATA4 in nucleus (P < 0.001). Together, our data demonstrated that XML inhibited the TAC-induced HF via inactivating the ERK1/2, AKT/GSK3β, and GATA4 signaling pathway.