Diabetic Cardiomyopathies

Diabetes can lead to heart failure independently, but the underlying causes remain incompletely understood. The main aim of this study is to identify differential regulation of mitochondrial substrate utilization and complex activity in heart failure and type 2 diabetes mellitus (T2DM). For this, we will conduct a prospective, observational study to examine myocardial mitochondrial oxidative function and related metabolic parameters, gene expression, histological markers, and inflammation in cardiac tissue from patients with heart failure or patients after heart transplantation. We will further assess cardiac function using cardiac magnetic resonance imaging with and without stress protocols and magnetic resonance spectroscopy. Glycemic control/T2DM will be characterized by oral glucose tolerance tests. The results of this project will help to better understand the cellular mechanisms of the development of diabetic cardiomyopathy and contribute to the development of early diagnostic, as well as therapeutic approaches for the prevention and treatment of diabetic cardiomyopathy.

Heart failure with preserved ejection fraction (HFpEF) is associated with a high morbidity and mortality burden. There are limited pharmacological options available for the treatment of HFpEF. Exercise intolerance (EI) is the cardinal symptom of HFpEF, which manifests as dyspnea and fatigue. EI leads to functional deconditioning and reduced quality of life (QOL), both of which elevate risk of death and hospitalization in patients with HFpEF. Supervised exercised training is associated with improvements in exercise capacity and QOL in adults with HFpEF. However, supervised exercise has not been widely utilized for the treatment of HFpEF due to logistical and fiscal barriers. This study will investigate the effects of a remote exercise training intervention on exercise capacity and skeletal muscle composition in patients with HFpEF, or those at risk for it. In addition, it will compare four different lifestyle interventions for their effects on exercise capacity.

Diabetes mellitus is among the top 10 causes of death worldwide with an increasing incidence. Patients with diabetes are at risk of developing heart failure which is characterised by significant changes in the heart muscle including scarring and thickening. Contraction of the heart involves movement of calcium across the heart muscle and disruption of this process is an early change seen in heart failure. Recently, a drug therapy (SGLT2 inhibitor therapy) in patients with diabetes was shown to benefit patients with heart failure but the mechanisms of benefit are unknown. Our hypothesis is that calcium handling is altered in patients with either type 2 diabetes mellitus (T2DM) or heart failure and that SGLT2 inhibitors can improve this in heart failure irrespective of the presence of T2DM. Scanning the heart using magnetic resonance imaging (MRI) enables detailed assessment of its structure and function by using a new contrast 'dye' containing manganese that has shown advantages over traditional contrast. We plan to further test this new dye as it has the potential to track and quantify improvements in heart function over time and detect changes in calcium handling in the heart muscle, making it an ideal measure to identify the mechanisms of benefit from SGLT2 inhibitor therapy. The study population will comprise patients with heart failure with and without type 2 diabetes, patients with type 2 diabetes without heart failure and healthy volunteers. Baseline comparisons will be made between the four groups before progressing to the randomised controlled trial with heart failure patients only. Patients will have a clinical assessment and blood tests, electrocardiogram, echocardiogram and MRI of the heart at each visit. If successful, this study will give us significant insights into mechanisms of action of SGLT2 inhibitors in heart failure and will enable us to tailor specific treatments in heart failure patients.

Background: Heart failure is a major cause of morbidity and mortality in diabetes mellitus, but its pathophysiology is poorly understood. Aim: To determine the prevalence and determinants of subclinical cardiovascular dysfunction in adults with type 2 diabetes (T2D). Plan: 518 asymptomatic adults (aged 18-75 years) with T2D will undergo comprehensive evaluation of cardiac structure and function using cardiac MRI (CMR) and spectroscopy, echocardiography, CT coronary calcium scoring, exercise tolerance testing and blood sampling. 75 controls will undergo the same evaluation. Primary hypothesis: myocardial steatosis is an independent predictor of left ventricular global longitudinal strain. Secondary hypotheses: will assess whether CMR is more sensitive to detect early cardiac dysfunction than echocardiography and BNP, and whether cardiac dysfunction is related to peak oxygen consumption. Expected value of results: This study will reveal the prevalence and determinants of cardiac dysfunction in T2D, and could provide targets for novel therapies.