Diabetic cardiomyopathy: insights into pathogenesis, diagnostic challenges, and therapeutic options

Diabetic cardiomyopathy is the presence of myocardial dysfunction in the absence of coronary artery disease and hypertension. Hyperglycemia seems to be central to the pathogenesis of diabetic cardiomyopathy and to trigger a series of maladaptive stimuli that result in myocardial fibrosis and collagen deposition. These processes are thought to be responsible for altered myocardial relaxation characteristics and manifest as diastolic dysfunction on imaging. Sophisticated imaging technologies also have permitted the detection of subtle systolic dysfunction in the diabetic myocardium. In the early stages, these changes appear reversible with tight metabolic control, but as the pathologic processes become organized, the changes are irreversible and contribute to an excess risk of heart failure among diabetic patients independently of common comorbidities, such as coronary artery disease and hypertension. Therapeutic agents specifically targeting processes that lead to these pathophysiologic changes are in the early stages of development. Although glycemic control and early administration of neurohormonal antagonists remain the cornerstones of therapeutic approaches, newer treatment targets are currently being explored.     

Diabetic cardiomyopathy: a hyperglycaemia- and insulin-resistance-induced heart disease

Diabetic cardiomyopathy is characterised in its early stages by diastolic relaxation abnormalities and later by clinical heart failure in the absence of dyslipidaemia, hypertension and coronary artery disease. Insulin resistance, hyperinsulinaemia and hyperglycaemia are each independent risk factors for the development of diabetic cardiomyopathy. The pathophysiological factors in diabetes that drive the development of cardiomyopathy include systemic metabolic disorders, inappropriate activation of the renin–angiotensin–aldosterone system, subcellular component abnormalities, oxidative stress, inflammation and dysfunctional immune modulation. These abnormalities collectively promote cardiac tissue interstitial fibrosis, cardiac stiffness/diastolic dysfunction and, later, systolic dysfunction, precipitating the syndrome of clinical heart failure. Recent evidence has revealed that dysregulation of coronary endothelial cells and exosomes also contributes to the pathology behind diabetic cardiomyopathy. Herein, we review the relationships among insulin resistance/hyperinsulinaemia, hyperglycaemia and the development of cardiac dysfunction. We summarise the current understanding of the pathophysiological mechanisms in diabetic cardiomyopathy and explore potential preventative and therapeutic strategies.     

Diabetic dyslipidemia and pathogenesis of ischemic heart disease

BACKGROUND: Type II diabetes is associated with high risk of ischemic heart disease (IHD), diabetes and IHD have similar risk factors, abdominal obesity as well as interrelated disturbances of lipid and carbohydrate metabolism play important roles in pathogenesis of both diseases. AIM: To elucidate characteristics of metabolism and transport of lipids and carbohydrates in patients with type II diabetes and IHD with normal and excessive body mass with abdominal type of fat distribution. MATERIAL AND METHODS: Parameters of carbohydrate metabolism, blood serum levels of free fatty acids, lipid and apoprotein (apo-) parameters of lipoprotein spectrum were evaluated in subjects without diabetes or IHD (group 1), patients with IHD and normal body mass (group 2), patients with IHD combined with diabetes with normal body mass (group 3), patients with IHD, diabetes and abdominal obesity (group 4). RESULTS: Patients with combination of diabetes and IHD compared with those of groups 1 and 2 in addition to higher blood glucose had lower growth hormone, higher triglycerides, lower high density lipoprotein cholesterol (CH) and apo-A1, higher low/high density lipoprotein CH and apo-B/apo-A1 ratios. These atherogenic changes were more pronounced in patients of group 4 who had highest levels of insulin, free fatty acids, low density lipoprotein CH and apo-B and lowest glucose/insulin ratio and level of apo-A1. CONCLUSION: Insulin resistance and hyperinsulinemia are most important features of disturbed carbohydrate and lipid metabolism. Insulin resistance and hyperinsulinemia are most pronounced in subjects with abdominal obesity in whom they create conditions for impaired glucose utilization, development of atherogenic dyslipidemia and eventually emergence of IHD.     

Diabetic cardiopathy: pathogenesis, diagnosis and therapy

Diabetes mellitus is one of the most widespread metabolic diseases in Western industrial countries with increasing prevalence due to a progressively aging population that is also characterized by increasing obesity and a sedentary life style. Cardiovascular conditions are the major prognostic complications of diabetes. Cardiologically, diabetic cardiopathy may become manifest on different structural and functional levels of the heart. Disorders may involve the micro- and macrocirculation (angiopathy), ventricular function (cardiomyopathy) and the intracardial nervous system (autonomous neuropathy). The following survey summarizes the cardiovascular risk with particular attention to the pathogenesis, diagnostics and therapy of diabetes mellitus related coronary disease and diabetic cardiomyopathy.     

Diabetic cardiomyopathy,causes and effects

Diabetes is associated with increased incidence of heart failure even after controlling for coronary artery disease and hypertension. Thus, as diabetic cardiomyopathy has become an increasingly recognized entity among clinicians, a better understanding of its pathophysiology is necessary for early diagnosis and the development of treatment strategies for diabetes-associated cardiovascular dysfunction. We will review recent basic and clinical research into the manifestations and the pathophysiological mechanisms of diabetic cardiomyopathy. The discussion will be focused on the structural, functional and metabolic changes that occur in the myocardium in diabetes and how these changes may contribute to the development of diabetic cardiomyopathy in affected humans and relevant animal models.     

Diabetic cardiomyopathy and diastolic heart failure - Difficulties with relaxation

Diabetic patients carry a four- to five-fold increased risk of heart failure. Hyperglycaemia plays a central role in the pathogenesis of diabetic cardiomyopathy. Diabetic cardiomyopathy represents a distinct structural and functional disorder of the myocardium characterized by cardiac hypertrophy and an increased myocardial stiffness. At an early stage, diabetic cardiomyopathy is manifested by diastolic heart failure with preserved ejection fraction. In some patients, diastolic dysfunction may progress to heart failure with reduced ejection fraction and result in overt systolic heart failure. Diastolic dysfunction can accurately be diagnosed by echocardiography and BNP measurement in daily clinical practice. Early treatment is prognostically important. Optimal control of blood glucose levels and blood pressure is beneficial. So far metformin is the only antidiabetic agent not associated with harm in diabetic patients with heart failure. Incretin-based therapies potentially provide cardiovascular benefits. ACE inhibitors, angiotensin-1 receptor antagonists and beta-blockers should be preferred in heart failure therapy.     

Diabetic cardiomyopathy: evidence, mechanisms, and therapeutic implications

The presence of a diabetic cardiomyopathy, independent of hypertension and coronary artery disease, is still controversial. This systematic review seeks to evaluate the evidence for the existence of this condition, to clarify the possible mechanisms responsible, and to consider possible therapeutic implications. The existence of a diabetic cardiomyopathy is supported by epidemiological findings showing the association of diabetes with heart failure; clinical studies confirming the association of diabetes with left ventricular dysfunction independent of hypertension, coronary artery disease, and other heart disease; and experimental evidence of myocardial structural and functional changes. The most important mechanisms of diabetic cardiomyopathy are metabolic disturbances (depletion of glucose transporter 4, increased free fatty acids, carnitine deficiency, changes in calcium homeostasis), myocardial fibrosis (association with increases in angiotensin II, IGF-I, and inflammatory cytokines), small vessel disease (microangiopathy, impaired coronary flow reserve, and endothelial dysfunction), cardiac autonomic neuropathy (denervation and alterations in myocardial catecholamine levels), and insulin resistance (hyperinsulinemia and reduced insulin sensitivity). This review presents evidence that diabetes is associated with a cardiomyopathy, independent of comorbid conditions, and that metabolic disturbances, myocardial fibrosis, small vessel disease, cardiac autonomic neuropathy, and insulin resistance may all contribute to the development of diabetic heart disease.     

Diabetic cardiomyopathy

Diabetic individuals are at significantly greater risk of developing heart failure (HF) independent from other risk factors such as coronary artery disease (CAD) and hypertension. Diabetic cardiomyopathy (DCP) is defined as ventricular dysfunction in the absence of hypertension, coronary artery and valvular heart disease, which increases the risk of HF. Due to better understanding of its pathophysiology and clinical importance, DCP is more frequently recognized in daily practice. The most important mechanisms of DCP are hyperglycemia, insulin resistance/hyperinsulinemia, abnormal fatty acid metabolism, increased apoptosis, cardiac autonomic neuropathy and local renin-angiotensin-aldosterone system (RAAS) overactivation. Echocardiography is the most frequently used diagnostic method for the detection of this pathology. Currently, although there is no specific treatment for DCP, strict glycemic and concomitant risk factor controls seems to be the most important target strategy for prevention of the progression and treatment of DCP. In this article, we aim to provide an extensive review on the pathophysiology, diagnosis, management of DCP.     

Diabetic cardiomyopathy

Although the pathogenesis of diabetic cardiomyopathy is poorly understood, recent evidence implicates perturbations in cardiac energy metabolism. Whereas mitochondrial fatty acid oxidation is the chief energy source for the normal postnatal mammalian heart, the relative contribution of glucose utilization pathways is significant, allowing the plasticity necessary for steady ATP production in the context of diverse physiologic and dietary conditions. Because of the importance of insulin in the regulation of myocardial metabolism, chronic insulin deficiency or resistance results in a marked reduction in cardiac glucose utilization such that the heart relies almost exclusively on fatty acids to generate energy. High rates of fatty acid utilization in the diabetic heart could lead to functional derangements related to accumulation of lipid intermediates, excessive oxygen consumption.... Chronic derangements in myocardial cell metabolism, as well as impairment of various intracellular signalling pathways, may therefore have maladaptive consequences, including functional abnormalities.     

Diabetic cardiomyopathy

Individuals with diabetes are at a significantly greater risk of developing cardioymyopathy and heart failure despite adjusting for concomitant risks such as coronary artery disease or hypertension. This has led to the increased recognition of a distinct disease process termed as "diabetic cardiomyopathy." In this article, we perform an extensive review of the pathogenesis and treatment of this disease. From a clinical perspective, physicians should be aware of this entity, and early screening should be considered because physical evidence of early diabetic cardiomyopathy could be difficult to detect. Early detection of the disease should prompt intensification of glycemic control, concomitant risk factors, use of pharmacologic agents such as β-blockers and renin-angiotensin-aldosterone system antagosists. From a research perspective, more studies on myocardial tissue from diabetic patients are needed. Clinical trials to evaluate the development of diabetic cardiomyopathy and fibrosis in early stages of the disease, as well as clinical trials of pharmacologic intervention in patients specifically with diabetic cardiomyopathy, need to be conducted.     

Diabetic cardiomyopathy

Diabetic cardiomyopathy is a myocardial disease caused by diabetes mellitus unrelated to vascular and valvular pathology or systemic arterial hypertension. Clinical and experimental studies have shown that diabetes mellitus causes myocardial hypertrophy, necrosis, and apoptosis, and increases interstitial tissue. The pathophysiology of diabetic cardiomyopathy is incompletely understood. It appears that metabolic perturbations such as hyperlipidemia, hyperinsulinemia, hyperglycemia, and changes in cardiac metabolism are involved in cellular consequences leading to increased oxidative stress, interstitial fibrosis, myocyte death, and altered intracellular ions transient and calcium homeostasis. Clinically, an early detection of asymptomatic diastolic dysfunction is possible. When patients develop signals and symptoms of heart failure, isolated diastolic dysfunction is usually detected. Systolic dysfunction is a late finding. Treatment of heart failure due to diabetic cardiomyopathy is not different from myocardiopathies of other etiologies and must follow the guidelines according to ventricular function, whether diastolic or diastolic and systolic impairment.     

Diabetic cardiomyopathy

Diabetes mellitus is well recognized as a potent and prevalent risk factor for accelerated atherosclerosis and ischemic heart disease. However, there is also evidence of cardiac dysfunction in diabetes in the absence of coronary atherosclerosis, termed diabetic cardiomyopathy. Changes in ventricular structure and left ventricular systolic and diastolic dysfunction have all been noted even in patients with well-controlled diabetes and without overt macrovascular complications. Insulin resistance, hyperglycemia, and increased free fatty acid metabolism promote coronary microvascular disease, sympathetic nervous system dysfunction, and ventricular remodeling, and may contribute to the altered cardiac phenotype seen in diabetes. In addition to standard therapy (angiotensin-converting enzyme inhibitors and β-blockers), diabetic patients with left ventricular dysfunction are likely to benefit from targeted therapies to reduce insulin resistance and modulate substrate use.     

Diabetic cardiomyopathy

Opinion statement  Diabetes mellitus is a major risk factor for the development of congestive heart failure (CHF). Diabetic cardiomyopathy has been acknowledged as a distinct disease entity that is an additional risk for diabetic patients to develop CHF, especially when they are affected by hypertension or epicardial coronary artery disease. Moreover, diabetic cardiomyopathy has been documented to lead to CHF even in the absence of other risk factors. As the combination of hypertension and diabetes has shown to be particularly detrimental, aggressive blood pressure control with a goal of less than 130/85 mm Hg is of critical importance. The first choice for pharmacologic treatment is angiotensinconverting enzyme inhibitors. Double- or triple-drug therapy is frequently required for good control. The increased risk of epicardial coronary artery disease in patients with diabetes warrants stringent treatment of dyslipidemia. If dilated cardiomyopathy with low ejection fraction is present, therapy with angiotensin-converting enzyme inhibitors, digoxin, diuretics, beta-blockers, and spironolactone (for patients with New York Heart Association class III to IV functional status) is indicated. If cardiac dysfunction consists predominantly of impaired diastolic function, heart rate control with a beta-blocker or a calcium antagonist is of particular importance. Control of blood glucose should be achieved, with hemoglobin A1c levels of less than 7%. Hyperinsulinemia should be avoided when possible; therefore, insulin-sensitizing agents are preferred over insulin-secretion-enhancing agents. Symptoms of CHF and acutely decompensated CHF should be treated no differently than nondiabetic patients. Care for patients with diabetes always includes lifestyle changes consisting of smoking cessation, decreasing obesity, regular exercise, and a heart-healthy diabetic diet.     

Diabetic cardiomyopathy

Diabetes mellitus is associated with a specific cardiomyopathy. This is evident from the clinical-pathological work and the epidemiologic data from the Framingham study. Noninvasive studies of diabetics have shown alterations in systolic and diastolic function that may ultimately lead to clinical heart failure. The relationship of these cardiac changes to the type of diabetes, its duration, and its severity is not settled. However, a correlation between changes in heart function and other complications of diabetes has been demonstrated. Insufficient prospective data is available from noninvasive studies to establish the frequency of progression from subclinical cardiac dysfunction to overt congestive failure. The pathogenesis of this disorder is still uncertain. Pathological studies have shown changes in the intramural arteries, arterioles, and capillaries but their functional significance is uncertain. Experimental studies have shown interstitial changes leading to an apparently less compliant left ventricle in the diabetic dog and monkey. In the diabetic rat reversible changes were found in myocardial function, related to changes in contractile proteins and intracellular calcium metabolism. In both species, the response to anoxia or ischemia was altered in the presence of diabetes. However, irreversible depression of the contractile element was not found in most animal studies of isolated diabetes. In contrast, the combination of hypertension and diabetes leads to substantial cardiac damage and circulatory congestion, both in clinical and experimental investigations. Clearly much more work must be carried out to understand the pathogenesis, treatment, and ultimately the prevention of diabetic cardiomyopathy.     

Diabetic cardiomyopathy

Summary Diabetic cardiomyopathy as a distinct entity was first recognized by Rubler et al. in diabetics with congestive heart failure (CHF), who had no evidence of coronary atherosclerosis. The Framingham study showed a 2.4-fold increased incidence of CHF in diabetic men and a 5.1-fold increase in diabetic women over 18 years. Pathological studies show left ventricular hypertrophy and fibrosis with varying degrees of small vessel disease, the functional significance of which is uncertain. Hypertension was recognized as an important cofactor in the development of fatal congestive heart failure in diabetics. On cardiac catheterization, in patients symptomatic of heart failure, either congestive or restrictive patterns have been observed. In contrast, asymptomatic diabetics had decreased left ventricular compliance but normal systolic function on hemodynamic study. Noninvasive studies show alterations in systolic and especially diastolic function, particularly in diabetics with microvascular complications and/or coexistent hypertension. Using load-independent measures of contractility, however, systolic function was generally found to be normal in asymptomatic normotensive diabetics. Experimental studies have focused on the mildly diabetic dog and the severely diabetic rat. Decreased left ventricular compliance and increased interstitial connective tissue were observed in chronically diabetic dogs. In contrast, ventricular myocardium from diabetic rats exhibits a reversible decrease in the speed of contraction, prolongation of contraction, and a delay in relaxation. These mechanical changes are associated with a decreased myosin ATPase, a shift in myosin isoenzyme distribution, alterations in a variety of Ca²⁺ fluxes, and changes in responses to alpha- and beta-adrenergic and cholinergic stimulation. These biochemical changes may be secondary to alterations in carbohydrate, lipid, and adenine nucleotide metabolism in the diabetic heart. When drug induced diabetes was combined with hypertension, a lethal cardiomyopathy with increased left ventricular hypertrophy and fibrosis, increased microvascular pathology and pulmonary congestion were observed. Compared to animals with isolated diabetes or hypertension, greater changes in papillary muscle function, isolated perfused heart performance, cellular electrophysiology, and contractile protein biochemistry were observed. Several studies suggest a protective effect of calcium channel blockers (verapamil and diltiazem) in experimental diabetic cardiomyopathy. Currently the clinical approach to this disorder emphasizes control of hyperglycemia and coexistent hypertension.     

Obesity cardiomyopathy: pathogenesis and pathophysiology

Obesity is becoming a worldwide phenomenon. Myocardial changes associated with the obese state are increasingly recognized, independent of hypertension, obstructive sleep apnea and coronary artery disease. The existence of a cardiomyopathy of obesity is supported by a range of evidence: epidemiologic study findings, which have shown an association between obesity and heart failure; clinical studies that have confirmed the association of adiposity with left ventricular dysfunction, independent of hypertension, coronary artery disease and other heart disease; and experimental evidence of structural and functional changes in the myocardium in response to increased adiposity. The most important mechanisms in the development of obesity cardiomyopathy are metabolic disturbances (insulin resistance, increased free fatty acid levels, and also increased levels of adipokines), activation of the renin-angiotensin-aldosterone and sympathetic nervous systems, myocardial remodeling, and small-vessel disease (both microangiopathy and endothelial dysfunction). In the first part of this two-part Review, we seek to evaluate the emerging evidence for the existence of a cardiomyopathy of obesity and clarify the responsible mechanisms.     

beta(1)-Adrenergic receptor function, autoimmunity, and pathogenesis of dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a heart disease characterized by progressive depression of cardiac function and left ventricular dilatation of unknown etiology in the absence of coronary artery disease. Genetic causes and cardiotoxic substances account for about one third of the DCM cases, but the etiology of the remaining 60% to 70% is still unclear. Over the past two decades, evidence has accumulated continuously that functionally active antibodies or autoantibodies targeting cardiac beta(1)-adrenergic receptors (anti-beta(1)-AR antibodies) may play an important role in the initiation and/or clinical course of DCM. Recent experiments in rats indicate that such antibodies can actually cause DCM. This article reviews current knowledge and recent experimental and clinical findings focusing on the role of the beta(1)-adrenergic receptor as a self-antigen in the pathogenesis of DCM.