The Roles Of Adropin In Chronic Heart Failure

Current heart failure therapeutic options are directed towards disease prevention via neurohormonal antagonism (β-blockers, angiotensin converting enzyme inhibitors and/or angiotensinreceptor blockers and aldosterone antagonists), symptomatic treatment with diuretics and digitalis and use of biventricular pacing and defibrillators in a special subset of patients. Despite these therapies and device interventions heart failure remains a progressive disease with high mortality and morbidity rates. The number of patients who survive to develop advanced heart failure is increasing. These patients require new therapeutic strategies.Normal cardiac function is dependent on a constant resynthesis of ATP by oxidative phosphorylation in the mitochondria. The healthy heart gets 60–90% of its energy for oxidative phosphorylation from fatty acid oxidation, with the balance from lactate and glucose. The failing heart has been shown to be metabolically abnormal, in both animal models and in patients, and chronic manipulation of myocardial substrate oxidation toward greater carbohydrate oxidation and less fatty acid oxidation may improve ventricular performance and slow the progression of left ventricular dysfunction in heart failure patients. Thus, regulation of cardiac energy metabolism is expected to be a new therapeutic strategy for heart failure.Adropin was initially discovered by Kumar et al. in 2008 during microarray analysis of liver gene expression in mouse models of obesity. Adropin is encoded by Energy Homeostasis Associated gene (Enho) that is expressed in the liver, brain, human umbilical vein and coronary artery endothelial cells. Liver Enho expression is regulated by energy status and dietary nutrient content, and is altered with obesity. Transgenic overexpression or systemic adropin treatment improves diet-induced obesity, insulin resistance, and glucose tolerance. Elevated BMI and obesity have been associated with the cardiovascular disease risk factors of hypertension, insulin resistance and dyslipidemia. Obesity has been linked to the development of HF. Thus, we hypothesized that adropin may also be related to the failing heart. In the present study, we are intent to investigate the relationship between adropin and HF, and to explore the effects of adropin on proliferation, apoptosis and energy metabolism in cardiocytes.PartⅠChanges of circulating adropin and its significance in CHF patients Objective: Adropin is a recently identified protein that has been implicated in the maintenance of energy homeostasis. we investigated plasma adropin levels in patients with CHF and evaluated the relationship between those and the severity of CHF.Methods: According to the present guidelinges for the diagnosis and management of chronic heart failure of the ACC/AHA, 56 patients with CHF and 20 healthy subjects were enrolled in this study. Plasma levels of adropin, TNF-α, IL-6 were measured using a commercial ELISA kit, and plasma BNP levels were measured with a commercial RIA kit. The plasma glucose levels were measured by an automated glucose oxidase method, serum levels of total TC, TG, HDL-C, LDL-C were measured by enzymatic methods using the autoanalyzer. The height and weight of subjects were measured to calculate the BMI. Ultrasonic was used to measure the heart function.Results: The LVEF gradually decreased and, inversely, plasma levels of BNP were exponentially elevated according to NYHA class in the CHF patients. Plasma BNP had a negative correlation with LVEF (r =-0.889, p<0.001,). Plasma levels of IL–6 and Cr were significantly higher in the classⅣpatients than those in the control group (p<0.05, p<0.05, respectively). Lipid analysis showed that plasma levels of TC and LDL-C were lower in the classⅣthan those in the control group (p<0.01, p<0.05, respectively). The plasma level of adropin increased with the deterioration of cardiac function ( control: 6.0±0.3 ng/mL; NYHAⅡ: 7.6±0.4 ng/mL; NYHAⅢ: 9.8±0.5 ng/mL; NYHAⅣ: 12.4±0.6 ng/mL, respectively, p<0.001). Plasma adropin level had a positive correlation with plasma BNP levels (r=0.723, p<0.001), plasma IL-6 levels (r=0.326, p<0.05),plasma Cr (r=0.238, p<0.05) and BMI (r=0.295, p<0.05). Plasma adropin levels negatively correlated with LVEF (r =-0.710, p<0.001,). In the multiple regression analysis, plasma BNP and BMI had independent impact on plasma adropin level in patients with CHF.Conclusion: Plasma adropin levels were significantly increased according to the severity of CHF. Multiple regression analysis showed BNP and BMI had independent impact on plasma adropin level. These findings suggest that the augmented release of adropin may be involved in the pathogenesis of CHF, but further study is necessary to explain the exact role of adropin in CHF.PartⅡEffect of synthetic adropin on cardiac function of HF rat Objective: To investigate the changes of circulating adropin levels in ischemic heart failure model of rats and the effects of treatment with adropin for 2 weeks on cardiac function.Methods: The SD rats were divided into experimental group (n = 40) and sham operation group (n=10), and model of heart failure induced by myocardial infarction was set up by ligating left descending anterior branch. The 40 rat models of heart failure were divided into early intervention group and late intervention group, each group was further divided into saline treatment group (n=6) and adropin treatment group (n=6). In adropin treatment group, rats were treated with 100ug/kg/d of adropin by intraperitoneal injection, and in saline treatment group, rats were treated with same doses of physiological saline. In early intervention saline treatment group and sham operation group, adropin was measured in five points of time, such as preoperative, postoperative 24h, 3d, 2wks, 4wks. In early intervention group, the histopathology of rat heart was observed by Gonori chromotropic acid staining and TUNEL kit after 2 weeks of treatment. In late intervention group, echocardiography was examined after 2 weeks of treatment.Results: Compared with sham operation group, adropin levels of rat in early intervention group were drop significantly in postoperative 24 hour (3.22±0.24ng/mL vs 5.60±0.16ng/mL, p<0.01), and began to increase in postoperative 3 days, but there was not statistically significant. The adropin levels were significantly increased in postoperative 4 weeks compared with sham operation group (8.06±0.15ng/mL vs 5.96±0.15ng/mL, p<0.01). In early intervention group, the degeneration and necrosis of rat myocardium in saline treatment group were much more serious than that in adropin treatment group. In early intervention group, TUNEL positive cells rate of rats in saline treatment group was significantly higher than that in adropin treatment group (39.8±8.2% vs 4.67±2.2%, p<0.01). In the late intervention group, LVEF of rat heart in adropin treatment group was significantly higher than that in saline treatment group (48.72±6.58% vs 35.52±2.05, p<0.01).Conclusion: After myocardial infarction, adropin levels of rat were transiently drop and then continued to rise. Treatment with adropin attenuated myocardial necrosis and apoptosis, and improved heart function of heart failure rat.PartⅢEffects of adropin on proliferation and apoptosis of cardiomyocyteObjective: Obeserve effects of adropin on AMPK pathways activating, and apoptosis induced by hypoxia in rat neonatal cardiomyocytes.Methods: MTT method was used to detect cell livability; Bradford method was used to measure cell protein level and synthetic speed of protein; Westernblot was used to detect cell p-AMPK levels; Annexin V-FITC was used to detect cell apoptosis in rat neonatal cardiomyocytes.Results: Compared with the control group, adropin significantly increased cell livability in hypoxic conditions (p<0.01), and reduced the total protein and the protein synthesis speed with a dose-response trend (p<0.01). Compared with serum-free group, there was no significant changes in cell apoptosis rate in adropin group cell (p=0.12), but apoptosis rate of adropin+hypoxia group cell was significantly reduced compared with hypoxia group (p < 0.01),this effect can be reversed by compound c,which is an inhibitor of p-AMPK. Treating with adropin (10^-6 mol/L), the p-AMPK level in adropin+hypoxia group transiently increased in 15min to 30min compared with hypoxia group (p < 0.01).Conclusion: Adropin increased livability of cell, inhibited cell hypertrophy, elevated p-AMPK level in rat neonatal cardiomyocytes, and it had anti-apoptotic effects through AMPK activities under the condition of hypoxia.