Clinical Research On Plasma Branched-chain Amino Acids Level In Patients With Chronic Congestive Heart Failure

Background:Chronic congestive heart failure (CHF) is a serious manifestation or a terminal phase of various cardiovascular diseases, characterized by increasing morbidity, difficulties in treatment and poor prognosis. CHF has been a serious threat to human life and health. In recent decades, the pathophysiologic concept of CHF has evolved from cardiac dysfunction to a systemic disease including metabolic disturbances and inflammation. Recent publications have revealed that the onset and deterioration of CHF is associated with an alteration of metabolism in cardiomyocytes. In physiological conditions fatty acid oxidation is the major source of energy in cardiomyocytes. When heart failure occurs, the shift from a fatty acid-dominant bioenergetic state into a more glycolytic state in stressed myocardium is viewed as a compensatory response with the purpose of enhancing oxygen/fuel utilization efficiency. However, impairments in glucose utilization and suppression of fatty acid oxidation in myocardium in the pathological state ultimately lead to a deficiency in energy supply, and form a vicious cycle, namely metabolic remodeling. Therefore, it’s of great importance to investigate the regulatory mechanism underlying the metabolic defects and to manipulate the fuel supply in failing hearts. Nevertheless, much of current investigations is focused on fatty acids and carbohydrates. In contrast, protein and amino acid metabolism is largely underexplored, and the relationship between amino acid metabolism and cardiovascular diseases remains poorly understood.Branched-chain amino acids (BCAAs) including leucine, isoleucine and valine belong to a subgroup of essential amino acids. They are collectively referred to BCAAs as they all share the structural features in side-chain. BCAAs have various physiologic functions including their role as key building blocks for peptide synthesis and significant sources for biosynthesis of sterole, keto bodies and glucose. The final catabolic products of BCAA are acetyl-CoA and succinyl-CoA, which are consumed in mitochondria through tri-carboxylic acid cycle for energy. What’s more, BCAAs, particularly leucine, have potent nutrient signaling activity in cells to promote protein synthesis, cellular metabolism, and cell growth in a mammalian target of rapamycin (mTOR)-dependent manner. Therefore, BCAAs are essential for normal growth and function at cellular and organism levels. However, an excess amount of free BCAAs or their catabolic products can be cytotoxic as well. A high BCAAs level in plasma is positively associated with dyslipidemia, insulin resistance and type 2 diabetic mellitus (T2DM). Unlike much of the other amino acid metabolic/catabolic activities that take place in liver, the first step of BCAAs catabolism occurs in non-hepatic tissues, mostly cardiac musle, neuron and kidney. Therefore, alteration of BCAAs metabolism is very likely to get involved in metabolic remodeling of CHF. Up to now, no data shows whether plasma level of BCAAs is associated with CHF or not.N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) is a biochemical index for monitoring CHF commonly used in clinical practice. Plasma NT-pro-BNP level is significantly increased in patients with ventricular dysfunction, and it is positively correlated with severity of cardiac dysfunction. Left ventricular ejection fraction (LVEF) is a commonly accepted index to evaluate left ventricular systolic function. Thereafter, this study was aimed to explore the change of plasma BCAAs level in patients with CHF, and its correlation with NT-pro-BNP and LVEF, in order to further explore mechanisms of CHF and to find novel therapeutic strategies.Objectives:1.To detect the change of BCAAs level in patients with CHF compared with normal control subjects;2.To determine the relationships of plasma BCAAs level with T-pro-BNP and LVEF in patients with CHF.Methods:1. A total of 168 hospitalized patients (123 males and 45 females) with chronic congestive heart failure diagnosed in Department of cardiology of Xijing Hospital from January 2012 to January 2013, were admitted as subjects of experimental group of the study. The age range is from 35 to 65 years old (mean:42±10 years old), and the history of disease is from 0.5 to 6 years. Patients with left ventricular ejection fraction less than 45% were chosen (systolic heart failure).41 healthy people (29 males and 12 females) undergone routine physiological examination in Xijing Hospital were selected as normal control group. The mean age is 44±7 years old from 33 to 69 years old. Information of subjects including blood pressure, body mass index were collected.2. The experimental group was divided into several subgroups. In accordance with New York Heart Association (NYHA) functional classification, the experimental group was divided into three subgroups:NYHA Ⅱ group (n=36), NYHA Ⅲ group (n=80), and NYHA IV group (n=52). According to initial causes of CHF, the experimental group was divided into ischemic heart disease (n=114) group, dilated cardiomyopathy (n=46) group and other types of cardiovascular diseases (n=8) group. What’s more, the experimental group were divided into four groups including obese (n=4), overweight (n=36), normal weight (n=108) and underweight (n=20).3.5ml of fasting venous blood was drawn into tubes containing EDTA in resting state, and promptly placed in Centrifuge at 3000 r/m to separate plasma. Then the separated plasma was stored in EP tubes and frozen at-80℃ until assay. Plasma BCAAs level and NT-pro-BNP level were measured using Elisa method.4. Echocardiography was applied to detect the ventricular septal thickness (IVS), left ventricular posterior wall thickness (LVPW), left ventricualr end diastolic diameter (LVDd), and left ventricular end systolic diameter (LVSd). And left ventricular ejection fraction (LVEF) was calculated with a modified Simpson method.5. Statistical analysis was performed with SPSS 18.0 statistics software. Measurement data were presented as x± s, and comparisons between two groups were performed by t test; comparisons among more than two groups were performed by one way ANOVA, and Kruskal Wallis test was performed when heterogeneity of variance existed. The χ2 test was used to analysis categorical data. Correlation analysis was performed with pearson assay and stepwise regression analysis. P< 0.05 was considered statistically significant.Results:1. There was no significant difference of baseline information including gender, age, systolic blood pressure (SBP), diastolic blood pressure (DBP) and BMI in CHF patients compared with control group (all P> 0.05). However, the level of plasma BCAAs was significantly decreased in patients with CHF compared with control group. Besides, plasma NT-pro-BNP level was increased and LVEF was decreased significantly in CHF patients compared to control group (all P< 0.05).2. CHF patients were divided into subgroups according to NYHA functional classification. There was no significant difference of plasma BCAAs levels among grade Ⅱ,Ⅲ or Ⅳ (P< 0.05). Nevertheless, from grade Ⅱ to grade Ⅳ, the levels of NT-pro-BNP were increased and LVEF values were decreased with the deterioration of cardiac dysfunction (all P<0.01).3.CHF patients were divided into ischemic heart disease (IHD), dilated cardiomyopathy (DCM) and valvular heart disease (VHD) according to the initial causes of CHF. The BCAAs level of IHD was lower than that from DCM and VHD subgroups (P < 0.05).4. According to BMI, CHF patients were divided into four subgroups including obese, overweight, normal weight and underweight. There was no significant difference in plasma BCAAs in CHF patients with different BMI.5. Pearson-related analysis revealed that plasma BCAAs level was positively correlated with NT-pro-BNP and BMI. Besides, stepwise regression analysis revealed that NT-pro-BNP and BMI were independent indicators of BCAAs in CHF group.Conclusions1. The level of plasma BCAAs was significantly decreased in patients with CHF compared with control group, indicating that enhanced BCAAs catabolism might be compensatory for providing energy in failing heart. But plasma BCAAs level was not associated with severity of cardiac dysfunction. Besides, CHF patients with IHD revealed the lowest plasma BCAAs level, suggesting strong compensatory metabolism of BCAAs in ischemic myocardium.2. Plasma BCAAs level was positively correlated with NT-pro-BNP and BMI in patients with CHF. Besides, NT-pro-BNP and BMI were independent relevant factors to affect the level of plasma BCAAs in CHF patients.