Decreased ATP production and myocardial contractile reserve in metabolic heart disease

Available online 01 February 2018Metabolic syndrome is a cluster of obesity-related metabolic abnormalities that lead to metabolic heart disease (MHD) with left ventricular pump dysfunction. Although MHD is thought to be associated with myocardial energetic deficiency, two key questions have not been answered. First, it is not known whether there is a sufficient energy deficit to contribute to pump dysfunction. Second, the basis for the energy deficit is not clear. To address these questions, mice were fed a high fat, high sucrose (HFHS) 'Western' diet to recapitulate the MHD phenotype. In isolated beating hearts, we used 31P NMR spectroscopy with magnetization transfer to determine a) the concentrations of high energy phosphates ([ATP], [ADP], [PCr]), b) the free energy of ATP hydrolysis (∆G~ATP), c) the rate of ATP production and d) flux through the creatine kinase (CK) reaction. At the lowest workload, the diastolic pressure-volume relationship was shifted upward in HFHS hearts, indicative of diastolic dysfunction, whereas systolic function was preserved. At this workload, the rate of ATP synthesis was decreased in HFHS hearts, and was associated with decreases in both [PCr] and ∆G~ATP. Higher work demands unmasked the inability of HFHS hearts to increase systolic function and led to a further decrease in ∆G~ATP to a level that is not sufficient to maintain normal function of sarcoplasmic Ca2+-ATPase (SERCA). While [ATP] was preserved at all work demands in HFHS hearts, the progressive increase in [ADP] led to a decrease in ∆G~ATP with increased work demands. Surprisingly, CK flux, CK activity and total creatine were normal in HFHS hearts. These findings differ from dilated cardiomyopathy, in which the energetic deficiency is associated with decreases in CK flux, CK activity and total creatine. Thus, in HFHS-fed mice with MHD there is a distinct metabolic phenotype of the heart characterized by a decrease in ATP production that leads to a functionally-important energetic deficiency and an elevation of [ADP], with preservation of CK flux.Ivan Luptak, Aaron L. Sverdlov, Marcello Panagia, Fuzhong Qin, David R. Pimentel, Dominique Croteau, Deborah A. Siwik, Joanne S. Ingwall, Markus M. Bachschmid, James A. Balschi, Wilson S. Colucc

Galectin-3 is associated with stage B metabolic heart disease and pulmonary hypertension in young obese patients

Background Obesity is a precursor to heart failure with preserved ejection fraction. Biomarkers that identify preclinical metabolic heart disease ( MHD ) in young obese patients would help identify high-risk individuals for heart failure prevention strategies. We assessed the predictive value of GAL3 (galectin-3), FSTL3 (follistatin-like 3 peptide), and NT-proBNP (N-terminal pro-B-type natriuretic peptide) to identify stage B MHD in young obese participants free of clinically evident cardiovascular disease. Methods and Results Asymptomatic obese patients (n=250) and non-obese controls (n=21) underwent echocardiographic cardiac phenotyping. Obese patients were classified as MHD positive ( MHD - POS ; n=94) if they had abnormal diastolic function or left ventricular hypertrophy and had estimated pulmonary artery systolic pressure ≥35 mm Hg. Obese patients without such abnormalities were classified as MHD negative (MHD-NEG; n=52). Serum biomarkers timed with echocardiography. MHD - POS and MHD-NEG individuals were similarly obese, but MHD - POS patients were older, with more diabetes mellitus and metabolic syndrome. Right ventricular coupling was worse in MHD - POS patients ( P<0.001). GAL 3 levels were higher in MHD - POS versus MHD -NEG patients (7.7±2.3 versus 6.3±1.9 ng/mL, respectively; P<0.001). Both GAL 3 and FSTL 3 levels correlated with diastolic dysfunction and increased pulmonary artery systolic pressure but not with left ventricular mass. In multivariate models including all 3 biomarkers, only GAL 3 remained associated with MHD (odds ratio: 1.30; 95% CI , 1.01-1.68; P=0.04). Conclusions In young obese individuals without known cardiovascular disease, GAL 3 is associated with the presence of preclinical MHD . GAL 3 may be useful in screening for preclinical MHD and identifying individuals with increased risk of progression to obesity-related heart failure with preserved ejection fraction.Deepa M. Gopal, Nir Ayalon, Yi, Chih Wang, Deborah Siwik, Aaron Sverdlov, Courtney Donohue ... et al

Expert consensus document: Mitochondrial function as a therapeutic target in heart failure

Heart failure is a pressing worldwide public-health problem with millions of patients having worsening heart failure. Despite all the available therapies, the condition carries a very poor prognosis. Existing therapies provide symptomatic and clinical benefit, but do not fully address molecular abnormalities that occur in cardiomyocytes. This shortcoming is particularly important given that most patients with heart failure have viable dysfunctional myocardium, in which an improvement or normalization of function might be possible. Although the pathophysiology of heart failure is complex, mitochondrial dysfunction seems to be an important target for therapy to improve cardiac function directly. Mitochondrial abnormalities include impaired mitochondrial electron transport chain activity, increased formation of reactive oxygen species, shifted metabolic substrate utilization, aberrant mitochondrial dynamics, and altered ion homeostasis. In this Consensus Statement, insights into the mechanisms of mitochondrial dysfunction in heart failure are presented, along with an overview of emerging treatments with the potential to improve the function of the failing heart by targeting mitochondria. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved