Differential regulation of diacylglycerol kinase isoform in human failing hearts.

Evidence from several studies indicates the importance of Gαq protein-coupled receptor (GPCR) signaling pathway, which includes diacylglycerol (DAG), and protein kinase C, in the development of heart failure. DAG kinase (DGK) acts as an endogenous regulator of GPCR signaling pathway by catalyzing and regulating DAG. Expressions of DGK isoforms α, ε, and ζ in rodent hearts have been detected; however, the expression and alteration of DGK isoforms in a failing human heart has not yet been examined. In this study, we detected mRNA expressions of DGK isoforms γ, η, ε, and ζ in failing human heart samples obtained from patients undergoing cardiovascular surgery with cardiopulmonary bypass. Furthermore, we investigated modulation of DGK isoform expression in these hearts. We found that expressions of DGKη and DGKζ were increased and decreased, respectively, whereas those of DGKγ and DGKε remained unchanged. This is the first report that describes the differential regulation of DGK isoforms in normal and failing human hearts.

Serum YKL-40 predicts adverse clinical outcomes in patients with chronic heart failure.

BACKGROUND: Human cartilage glycoprotein-39 (YKL-40), a novel inflammatory marker, is secreted into circulation by macrophages, neutrophils, chondrocytes, vascular smooth muscle cells and cancer cells. Circulating levels of YKL-40 are related to the degree of inflammation, tissue remodeling, fibrosis, and cancer progression. METHODS AND RESULTS: We examined serum YKL-40 levels in 121 patients with chronic heart failure (CHF) and 39 control subjects. The patients were followed up to register cardiac events for a mean of 720 days. Serum YKL-40 levels were measured by sandwich enzyme-linked immunoassay. Serum YKL-40 was significantly higher in New York Heart Association (NYHA) Class III/IV patients than control subjects and NYHA Class I/II patients (P < .0001). Serum YKL-40 was also higher in patients with cardiac events than in event-free patients (P = .0023). Cutoff value of YKL-40 was determined by receiver operating characteristic curve analysis. Kaplan-Meier analysis demonstrated that high level of YKL-40 was associated with higher rates of cardiac events than low levels of YKL-40 (P = .003). The multivariate Cox hazard analysis demonstrated that serum YKL-40 level was an independent prognostic factor of cardiac events (hazard ratio 2.085, 95% confidence interval 1.233-3.499, P < .0048). CONCLUSIONS: Serum YKL-40, a new marker of inflammation, was increased in CHF, and YKL-40 detected high risk patients for adverse outcomes in CHF.

Risk stratification of chronic heart failure patients by multiple biomarkers: implications of BNP, H-FABP, and PTX3.

BACKGROUND: B-type natriuretic peptide (BNP), heart-type fatty acid-binding protein (H-FABP), and pentraxin 3 (PTX3) each predict adverse cardiac events in chronic heart failure (CHF) patients. For prognostic evaluation from different aspects, the utility of combined measurement of the 3 biomarkers in patients with CHF was examined in the present study. METHODS AND RESULTS: Levels of BNP (associated with left ventricular dysfunction, positive if >200 pg/ml), H-FABP (marker of myocardial damage, positive if >4.1 ng/ml), and PTX3 (marker of inflammation, positive if >4.0 ng/ml) were measured in 164 consecutive CHF patients, and patients were prospectively followed with endpoints of cardiac death or rehospitalization. When patients were categorized on the basis of the number of elevated biomarkers, patients with 1, 2, and 3 elevated biomarkers had a 5.4-fold (not significant), 11.2-old (p<0.05), and 34.6-fold increase (p<0.01), respectively, in the risk of adverse cardiac events compared with those without elevated biomarkers. Kaplan-Meier analysis revealed that patients with 3 elevated biomarkers had a significantly higher cardiac event rate than patients with a lower number of elevated biomarkers. CONCLUSION: The combination of these 3 biomarkers could reliably risk-stratify CHF patients for prediction of cardiac events.

Relation of serum heat shock protein 60 level to severity and prognosis in chronic heart failure secondary to ischemic or idiopathic dilated cardiomyopathy.

Heat shock protein (HSP) 60 is induced by a variety of stressors, including oxidative stress and inflammation, and it plays a protective role against stress-induced cardiomyocyte injury. Recently, it has been reported that HSP 60 exists in the circulation. Chronic heart failure (CHF) is characterized by systemic abnormalities, and the myocardium is exposed to various stressors. However, the clinical significance of serum HSP 60 has not been examined in CHF. Therefore, the purpose of this study was to examine whether HSP 60 is correlated with the severity of CHF and whether HSP 60 can predict clinical outcomes in patients with CHF. Serum HSP 60 levels were measured in 112 patients with CHF and 62 control subjects. Serum HSP 60 levels were higher in patients with CHF than in control subjects and increased with advancing New York Heart Association functional class. There were 37 cardiac events during a mean follow-up period of 569 +/- 476 days (range 17 to 1,986). Serum HSP 60 levels were higher in patients with cardiac events than in event-free patients. Patients were divided into 4 groups on the basis of HSP 60 level. Cox proportional-hazards regression analysis and Kaplan-Meier analysis revealed that the fourth quartile was associated with the greatest risk for cardiac events. In conclusion, serum HSP 60 level was related to the severity of CHF and associated with a high risk for adverse cardiac events in patients CHF.

High-mobility group box 1 restores cardiac function after myocardial infarction in transgenic mice.

AIMS: High-mobility group box 1 (HMGB1) is a nuclear DNA-binding protein and is released from necrotic cells, inducing inflammatory responses and promoting tissue repair and angiogenesis. To test the hypothesis that HMGB1 enhances angiogenesis and restores cardiac function after myocardial infarction (MI), we generated transgenic mice with cardiac-specific overexpression of HMGB1 (HMGB1-Tg) using alpha-myosin heavy chain promoter. METHODS AND RESULTS: The left anterior descending coronary artery was ligated in HMGB1-Tg and wild-type littermate (Wt) mice. After coronary artery ligation, HMGB1 was released into circulation from the necrotic cardiomyocytes of HMGB1-overexpressing hearts. The size of MI was smaller in HMGB1-Tg than in Wt mice. Echocardiography and cardiac catheterization demonstrated that cardiac remodelling and dysfunction after MI were prevented in HMGB1-Tg mice compared with Wt mice. Furthermore, the survival rate after MI of HMGB1-Tg mice was higher than that of Wt mice. Immunohistochemical staining revealed that capillary and arteriole formation after MI was enhanced in HMGB1-Tg mice. CONCLUSION: We report the first in vivo evidence that HMGB1 enhances angiogenesis, restores cardiac function, and improves survival after MI. These results may provide a novel therapeutic approach for left ventricular dysfunction after MI.

Diacylglycerol kinase-epsilon restores cardiac dysfunction under chronic pressure overload: a new specific regulator of Galpha(q) signaling cascade.

Galpha(q) protein-coupled receptor (GPCR) signaling pathway, which includes diacylglycerol (DAG) and protein kinase C (PKC), plays a critical role in cardiac hypertrophy. DAG kinase (DGK) catalyzes DAG phosphorylation and controls cellular DAG levels, thus acting as a regulator of GPCR signaling. It has been reported that DGKepsilon acts specifically on DAG produced by inositol cycling. In this study, we examined whether DGKepsilon prevents cardiac hypertrophy and progression to heart failure under chronic pressure overload. We generated transgenic mice with cardiac-specific overexpression of DGKepsilon (DGKepsilon-TG) using an alpha-myosin heavy chain promoter. There were no differences in cardiac morphology and function between wild-type (WT) and DGKepsilon-TG mice at the basal condition. Either continuous phenylephrine infusion or thoracic transverse aortic constriction (TAC) was performed in WT and DGKepsilon-TG mice. Increases in heart weight after phenylephrine infusion and TAC were abolished in DGKepsilon-TG mice compared with WT mice. Cardiac dysfunction after TAC was prevented in DGKepsilon-TG mice, and the survival rate after TAC was higher in DGKepsilon-TG mice than in WT mice. Phenylephrine- and TAC-induced DAG accumulation, the translocation of PKC isoforms, and the induction of fetal genes were blocked in DGKepsilon-TG mouse hearts. The upregulation of transient receptor potential channel (TRPC)-6 expression after TAC was attenuated in DGKepsilon-TG mice. In conclusion, these results demonstrate the first evidence that DGKepsilon restores cardiac dysfunction and improves survival under chronic pressure overload by controlling cellular DAG levels and TRPC-6 expression. DGKepsilon may be a novel therapeutic target to prevent cardiac hypertrophy and progression to heart failure.

Diacylglycerol kinase zeta inhibits myocardial atrophy and restores cardiac dysfunction in streptozotocin-induced diabetes mellitus.

BACKGROUND: Activation of the diacylglycerol (DAG)-protein kinase C (PKC) pathway has been implicated in the pathogenesis of a number of diabetic complications. Diacylglycerol kinase (DGK) converts DAG to phosphatidic acid and acts as an endogenous regulator of PKC activity. Akt/PKB is associated with a downstream insulin signaling, and PKCbeta attenuates insulin-stimulated Akt phosphorylation. METHODS AND RESULTS: We examined transgenic mice with cardiac-specific overexpression of DGKzeta (DGKzeta-TG) compared to wild type (WT) mice in streptozotocin-induced (STZ, 150 mg/kg) diabetic and nondiabetic conditions. After 8 weeks, decreases in heart weight and heart weight/body weight ratio in diabetic WT mice were inhibited in DGKzeta-TG mice. Echocardiography at 8 weeks after STZ-injection demonstrated that decreases in left ventricular end-diastolic diameter and fractional shortening observed in WT mice were attenuated in DGKzeta-TG mice. Thinning of the interventricular septum and the posterior wall in diabetic WT hearts were blocked in DGKzeta-TG mice. Reduction of transverse diameter of cardiomyocytes isolated from the left ventricle in diabetic WT mice was attenuated in DGKzeta-TG mice. Cardiac fibrosis was much less in diabetic DGKzeta-TG than in diabetic WT mice. Western blots showed translocation of PKCbeta and delta isoforms to membrane fraction and decreased Akt/PKB phosphorylation in diabetic WT mouse hearts. However in diabetic DGKzeta-TG mice, neither translocation of PKC nor changes Akt/PKB phosphorylation was observed. CONCLUSION: DGKzeta modulates intracellular signaling and improves the course of diabetic cardiomyopathy. These data may suggest that DGKzeta is a new therapeutic target to prevent or reverse diabetic cardiomyopathy.