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.

The effect of immunosuppressive therapy on cardiac involvements in anti-mitochondrial antibody-positive myositis

AIMS

Anti-mitochondrial antibody (AMA)-positive myositis is frequently associated with various cardiac involvements, such as arrhythmia and left ventricular (LV) dysfunction. However, the efficacy of immunosuppressive therapy in these complications remains unknown. This study aimed to investigate the cardiac response to immunosuppressive therapy in patients with AMA-positive myositis.

METHODS AND RESULTS

The clinical data of 15 AMA-positive myositis patients with cardiac involvement were retrospectively collected at our centre. To evaluate the effects of immunosuppressive therapy, echocardiographic and laboratory data of patients who received glucocorticoid therapy with additional immunosuppressants (n = 6) and those who did not (n = 6) were compared. Also, the characteristics of patients with or without >5% LV ejection fraction (LVEF) decline during the follow-up period (n = 5 vs. n = 7) were compared. Thirteen patients (87%) had arrhythmias, and eight patients (53%) had LV wall motion abnormalities. Although arrhythmias decreased after treatment, reduced LVEF and LV wall motion abnormalities persisted. Further investigation revealed an increased LV end-systolic dimension and reduced LVEF in patients without additional immunosuppressive therapy, while those in patients with additional immunosuppressive therapy were maintained. Six of seven patients (86%) without LVEF decline received additional immunosuppressive therapy, whereas no patients with LVEF decline had additional immunosuppressive therapy.

CONCLUSIONS

Cardiac involvement in AMA-positive myositis may worsen even with glucocorticoid monotherapy, and there might be some associations between the change of LV function and additional immunosuppressive therapy.

CXCR7 in cardiomyocytes prevents cardiac dysfunction after myocardial infarction

Background

Beta blockers and angiotensin II receptor blockers take effect through G protein-coupled receptors (GPCRs) and their protective roles in heart failure are partially attributable to beta-arrestin biased agonism. CXCR7, a chemokine receptor, is beta-arrestin biased receptor and one of the most expressing GPCRs in the heart. CXCL12 is a common ligand of CXCR4 and CXCR7 and is known to ameliorate myocardial infarction (MI), reportedly through CXCR4 dependent mechanisms. However, the role of another receptor, CXCR7 and its downstream target including beta-arrestin is not fully elucidated in MI.

Purpose

The aim of this study is to uncover the role of CXCR7 in cardiomyocytes after MI.

Methods

First, we quantified CXCR7 mRNA expressions in neonate rat cardiomyocytes (NRCM) in a dish by qRT-PCR. NRCMs were treated with CXCR7 agonist: TC14012 and phosphorylation of extracellular signal regulated kinase (ERK) was measured as readout of the downstream of CXCR7, with immunoblotting. Second, MI was induced by left anterior descending artery (LAD) ligation in male 12-week-old mice. We explored spatial expressions of CXCR7 by qRT-PCR in infarct, peri-infarct and remote zones of wild-type MI mice. Finally, we developed cardiomyocyte-specific CXCR7 knockout mice (cKO) by the Cre/loxP system and analyzed CXCR7 expression in cKO by qRT-PCR. LAD ligation was also performed in cKO and littermate controls (Ctl). Heart weight (HW) was measured and systolic function was examined by echocardiography 4 weeks after ligation. Phosphorylated ERK was evaluated with immunoblotting one-day after ligation.

Results

First, we found that CXCR7 expression was significantly higher in NRCM than neonatal rat fibroblasts (NRFB) and ERK was phosphorylated by CXCR7 stimulation in NRCM. Second, CXCR7 expression was higher in infarct and peri-infarct zones than remote zones. Finally, cardiomyocyte-specific knockout of CXCR7 resulted in 78±21% reduction of CXCR7 expression in the whole heart. HW and left ventricular area was significantly greater (HW: Ctl 190.7±18.4, cKO 220.3±26.4 mg) and fractional area change of left ventricle was significantly lower in cKO than those in Ctl 4 weeks after MI (LV FAC: Ctl 20.6±4.9%, cKO 13.9±5.4%), indicating that loss of CXCR7 in cardiomyocytes caused left ventricle enlargement and systolic dysfunction. One day after MI of Ctl heart, ERK was more phosphorylated in peri-infarct zone than remote zone. However, this ERK phosphorylation in peri-infarct zone was reduced in cKO MI heart.

Conclusion

We revealed that CXCR7 is expressed in cardiomyocytes and deletion of this chemokine receptor in cardiomyocytes resulted in ventricle enlargement and systolic dysfunction possibly through ERK phosphorylation in peri-infarct zone. Therefore, CXCR7 in cardiomyocytes could prevent cardiac dysfunction after myocardial infarction, which may be another pathway of CXCL12 dependent-protective effect.

Figure 1

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): JSPS KAKENHI

Omega-3 fatty acid prevents the development of heart failure by changing fatty acid composition in the heart

Some clinical trials showed that omega-3 fatty acid (FA) reduced cardiovascular events, but it remains unknown whether omega-3 FA supplementation changes the composition of FAs and their metabolites in the heart and how the changes, if any, exert beneficial effects on cardiac structure and function. To clarify these issues, we supplied omega-3 FA to mice exposed to pressure overload, and examined cardiac structure and function by echocardiography and a proportion of FAs and their metabolites by gas chromatography and liquid chromatography-tandem mass spectrometry, respectively. Pressure overload induced cardiac hypertrophy and dysfunction, and reduced concentration of all FAs’ components and increased free form arachidonic acid and its metabolites, precursors of pro-inflammatory mediators in the heart. Omega-3 FA supplementation increased both total and free form of eicosapentaenoic acid, a precursor of pro-resolution mediators and reduced free form arachidonic acid in the heart. Omega-3 FA supplementation suppressed expressions of pro-inflammatory cytokines and the infiltration of inflammatory cells into the heart and ameliorated cardiac dysfunction and fibrosis. These results suggest that omega-3 FA-induced changes of FAs composition in the heart have beneficial effects on cardiac function via regulating inflammation.

Abstract 498: The Effects of Low-carbohydrate High-fat Diet on Vascular Remodeling

Background: Low carbohydrate diet (LCD) has been reported to reduce body weight and cardiovascular risk factors, including diabetic mellitus and dyslipidemia. Therefore, LCD was once expected to prevent cardiovascular events. However, recent meta-analysis reported that LCD was related to an increase in cardiovascular events. Moreover, other cohort studies reported that higher all-cause and cardiovascular mortality were observed only in LCD with animal derived-fat (LCD-A), not in LCD with plant derived-fat (LCD-P). Precise mechanisms of these effects have not been clarified, so we explored the potential roles of LCD-A and LCD-P in blood vessel remodeling by using two types of vascular disease model mice, atherosclerotic model and vascular injury model.

Method: We generated two types of LCDs, beef tallow-based LCD (LCD-A) and cacao butter-based LCD (LCD-P). Six-week-old male ApoE Knockout (ApoE KO) mice (atherosclerosis model mice) and wild-type mice were subjected to LCD-A, LCD-P or normal chow for 14 weeks, and %plaque area of aortic root and serum lipid profile were measured. For vascular injury model, mice were inserted with a wire in a femoral artery of male 10-week-old wild-type mice and subjected to the three-types chow. After 4 weeks, femoral arteries were excised and embedded in paraffin and assessed with the extent of vascular injury severity. The femoral artery without injury on the other side was served as control.

Results: In ApoE KO mice, serum levels of total cholesterol (TC) and triglyceride (TG) were decreased in LCD group (TC: p<0.01, TG: p<0.05 vs normal chow), but there was no significant difference between LCD-A to LCD-P. In wild-type mice, serum TC level was increased in LCD-A group (p<0.0001 vs normal chow). LCD had no effect on %plaque area of aortic root in ApoE KO mice. In vascular injury model mice, there was no significant difference in the extent of neointimal hyperplasia induced by wire-injury among groups.

Conclusion: Our preliminary data showed that LCD had no effect on vascular remodeling despite the presence of significant alteration in lipid profiles. Additional experiments are needed to confirm the results and clarify the precise mechanisms.

Abstract 489: CC Chemokine Receptor 5 Protects the Heart from Inflammation in Pressure Overload-induced Cardiac Dysfunction

Objective: Sustained inflammation is a key pathological process in the development of heart failure and thus suppression of inflammation possibly leads to improvement of cardiac dysfunction. It has been suggested that CC chemokine receptor 5 (CCR5) scavenges pro-inflammatory mediators and resolves inflammation. The aim of this study is to uncover the role of CCR5 in the pathogenesis of heart failure.

Methods: Pressure overload heart failure was induced by transverse aortic constriction (TAC). Sham or TAC operation was performed in male 10-week-old CCR5 knockout (KO) mice and wild-type (WT) controls. Cardiac function and morphology were examined by echocardiography 1 week and 4 weeks after TAC surgery. After euthanization, the heart was extracted and embedded in paraffin for the measurements of cardiac fibrosis and cardiomyocyte hypertrophy with EVG stain and immunohistochemistry using WGA, respectively. The extent of inflammation was evaluated by the immunostaining against CD45 and F4/80 antigens, and by qRT-PCR for inflammatory cytokines and chemokines.

Results: We found that heart weight was significantly larger and fractional shortening was significantly lower in CCR5 KO mice than those in WT 4 weeks after TAC, indicating CCR5-induced protective effects on heart failure development. Whilst there was no difference observed in the extent of fibrosis, the size of cardiomyocytes from CCR5 KO heart tended to be increased compared to WT. The number of CD45-positive inflammatory cells and F4/80-positive macrophage infiltration was increased 1 week after TAC in KO mice. The RNA expression levels of monocyte chemotactic protein-1, transforming growth factor-β and tumor necrosis factor-α were significantly higher and NFκB p65 was more phosphorylated in KO mice.

Conclusions: We revealed that the inflammation in pressure overload-induced heart failure was exacerbated by the deletion of CCR5 and, therefore, CCR5 could contribute to resolution of inflammation and be a potential therapeutic target for the heart failure treatment.

Abstract 272: Cardioprotective Effects of Plant-derived Fat in Low Carbohydrate Diet on the Progression of Heart Failure

Background: The association between low carbohydrate diet (LCD) and cardiovascular disease and mortality remains unknown. Results from meta-analyses have reported that cardiovascular mortality increased when the carbohydrate in LCD was replaced for animal-derived fat, whereas mortality decreased when the substitution was plant-derived fat. However, the molecular mechanism is yet to be elucidated. We aimed to assess the effects of the LCD under two conditions, LCD with animal-derived fat (LCD-A) and LCD with plant-derived fat (LCD-P), on mouse cardiac function.

Methods: Using 10-week old male C57B/6J mice, we performed transverse aortic constriction surgery to generate a pressure overload model of heart failure and subjected them to either normal diet, LCD-A or LCD-P for 4 weeks. Cardiac function was measured by echocardiography at 4 weeks after surgery, and the extent of inflammation was assessed by immunohistological analysis. Expression levels of genes were assessed with RNA sequence.

Results: LCD-A accelerated left ventricular dilatation and systolic dysfunction (P<0.01 vs. normal diet), whereas LCD-P ameliorated cardiac hypertrophy (P<0.01 vs. normal diet) as revealed by echocardiograpy. Immunohistological analysis demonstrated that LCD-A resulted in a significant increase in the infiltration of F4/80-positive macrophages, reflecting exacerbated inflammation (P<0.01 vs. LCD-P, P<0.01 vs. normal diet). Consistent with histological findings, inflammation-related and cell cycle-related gene expressions were upregulated only in LCD-A. On the other hand, mitochondrial fatty acid oxidation gene expression including PPARα targets such as Cpt1a, Slc25a20, Acadvl, Hadha and Acaa2 were upregulated only in LCD-P (P<0.05, vs. normal diet), which may indicate the preserved energy metabolism during the pathogenic process of heart failure.

Conclusions: These results suggest that the effects of the LCD on cardiac function vary between the sources of fat alternatives to carbohydrate intake. LCD-P induces PPARα activation, an important regulator of mitochondrial lipid metabolism, that may be therapeutically relevant for heart failure treatment. Further studies are required to unveil the precise molecular mechanism.