Exercise training improves insulin-stimulated myocardial glucose uptake in patients with dilated cardiomyopathy

Insights from Exercise-induced Cardioprotection-from Clinical Application to Basic Research

Exercise has long been recognized as a beneficial living style for cardiovascular health. It has been applied to be a central component of cardiac rehabilitation for patients with chronic heart failure (CHF), coronary heart disease (CHD), post-acute coronary syndrome (ACS) or primary percutaneous coronary intervention (PCI), post cardiac surgery or transplantation. Although the effect of exercise is multifactorial, in this review, we focus on the specific contribution of regular exercise on the heart and vascular system. We will summarize the known result of clinical findings and possible mechanisms of chronic exercise on the cardiovascular system.

Exercise-based cardiac rehabilitation for patients with catheter ablation for persistent atrial fibrillation: A randomized controlled clinical trial

Aims

The efficacy and safety of cardiac rehabilitation for patients with persistent atrial fibrillation who restored sinus rhythm after catheter ablation remains unclear. The aim of the present study was to evaluate the effects of cardiac rehabilitation on exercise capacity, inflammatory status, cardiac function, and safety in patients with persistent atrial fibrillation who had catheter ablation.

Methods

In this randomized controlled study, 61 patients treated with catheter ablation for persistent atrial fibrillation (male, 80%; mean age, 66 ± 9 years) were analyzed. Thirty patients underwent cardiac rehabilitation (rehabilitation group), whereas the remaining 31 patients received usual care (usual care group). The rehabilitation group underwent endurance and resistance training with moderate intensity, at least three times per week for six months. Six-minute walk distance, muscle strength, serum high-sensitivity C-reactive protein, plasma pentraxin 3, left ventricular ejection fraction and atrial fibrillation recurrence were assessed at baseline and at six-month follow-up.

Results

In the rehabilitation group, significant increases in the six-minute walk distance, handgrip strength, leg strength and left ventricular ejection fraction and significant decreases in high-sensitivity C-reactive protein and plasma pentraxin 3 concentrations were observed at six-month follow-up compared with baseline (all p < 0.05). No significant changes were observed in the usual care group. During the six-month follow-up period, the number of patients with atrial fibrillation recurrence was six (21.4%) in the rehabilitation group and eight (25.8%) in the usual care group (risk ratio, 0.83; 95% confidence interval, 0.33 to 2.10).

Conclusions

Cardiac rehabilitation improved exercise capacity without increasing the risk for atrial fibrillation recurrence. It may also be effective in managing systemic inflammatory status and systolic left ventricular function in patients with persistent atrial fibrillation treated with catheter ablation.

Effects of exercise training on exercise capacity, cardiac function, BMI, and quality of life in patients with atrial fibrillation: a meta-analysis of randomized-controlled trials

Exercise training has become part of the standard care for patients with cardiovascular disease. We investigated the effects of exercise training on exercise capacity, cardiac function, BMI, and quality of life in patients with atrial fibrillation (AF). We searched for randomized-controlled trials of supervised exercise training versus care without exercise training (the control) in patients with permanent or nonpermanent AF published up to November 2016. Standard mean differences (SMD) or mean differences (MD), and 95% confidence intervals (CIs) were calculated using random-effect models. We identified 259 trials, and after an assessment of relevance, five trials with a combined total of 379 participants were analyzed. In AF patients, exercise training significantly improved exercise capacity and left ventricular ejection fraction compared with the control (SMD: 0.91, 95% CI: 0.70 to 1.12; MD: 4.8%, 95% CIs: 1.56 to 8.03, respectively). Compared with the control, exercise training also significantly reduced BMI (MD: -0.47 kg/m, 95% CIs: -0.89 to -0.06) and significantly improved scores in the 'general health' and 'vitality' sections of the 36-item Short Form Health Status Survey (SMD: 0.71, 95% CIs: 0.30 to 1.12; SMD: 0.81, 95% CIs: 0.40 to 1.23, respectively). Exercise training improved exercise capacity, left ventricular ejection fraction, and some the 36-item Short Form Health Status Survey scores, and reduced BMI in AF patients.

Cardiac rehabilitation improves coronary endothelial function in patients with heart failure due to dilated cardiomyopathy: A positron emission tomography study

BACKGROUND

Endothelial dysfunction is common in patients with heart failure and is associated with poor clinical outcome. Cardiac rehabilitation is able to enhance peripheral endothelial function but its impact on coronary vasomotion remains unknown. We aimed to evaluate the effect of cardiac rehabilitation on coronary vasomotion in patients with heart failure.

METHOD

We prospectively enrolled 29 clinically stable heart failure patients from non-ischaemic dilated cardiomyopathy and without coronary risk factors. Myocardial blood flow was quantified using (15)-O water positron emission tomography at rest and during a cold pressor test, before and after 12 weeks of cardiac rehabilitation and optimization of medical therapy.

RESULTS

Rest myocardial blood flow was significantly improved after the completion of rehabilitation compared to baseline (1.31 ± 0.38 mL/min/g vs. 1.16 ± 0.41 mL/min/g, p = 0.04). The endothelium-related change in myocardial blood flow from rest to cold pressor test and the percentage of myocardial blood flow increase during the cold pressor test were both significantly improved after cardiac rehabilitation (respectively from -0.03 ± 0.22 mL/min/g to 0.19 ± 0.22 mL/min/g, p < 0.001 and from 101.5 ± 16.5% to 118.3 ± 24.4%, p < 0.001). Left ventricular ejection fraction, plasma levels of brain natriuretic peptide, maximal oxygen consumption and the Minnesota Living with Heart Failure Questionnaire score were also significantly improved. The improvement was not related to uptitration of medical therapy.

CONCLUSIONS

Coronary endothelial function is altered in patients with heart failure due to non-ischaemic dilated cardiomyopathy. In these patients, cardiac rehabilitation significantly improves coronary vasomotion.

Rescue of heart lipoprotein lipase-knockout mice confirms a role for triglyceride in optimal heart metabolism and function

Hearts utilize fatty acids as a primary source of energy. The sources of those lipids include free fatty acids and lipoprotein triglycerides. Deletion of the primary triglyceride-hydrolyzing enzyme lipoprotein lipase (LPL) leads to cardiac dysfunction. Whether heart LPL-knockout (hLPL0) mice are compromised due a deficiency in energetic substrates is unknown. To test whether alternative sources of energy will prevent cardiac dysfunction in hLPL0 mice, two different models were used to supply nonlipid energy. 1) hLPL0 mice were crossed with mice transgenically expressing GLUT1 in cardiomyocytes to increase glucose uptake into the heart; this cross-corrected cardiac dysfunction, reduced cardiac hypertrophy, and increased myocardial ATP. 2) Mice were randomly assigned to a sedentary or training group (swimming) at 3 mo of age, which leads to increased skeletal muscle production of lactate. hLPL0 mice had greater expression of the lactate transporter monocarboxylate transporter-1 (MCT-1) and increased cardiac lactate uptake. Compared with hearts from sedentary hLPL0 mice, hearts from trained hLPL0 mice had adaptive hypertrophy and improved cardiac function. We conclude that defective energy intake and not the reduced uptake of fat-soluble vitamins or cholesterol is responsible for cardiac dysfunction in hLPL0 mice. In addition, our studies suggest that adaptations in cardiac metabolism contribute to the beneficial effects of exercise on the myocardium of patients with heart failure.

Dipeptidyl-peptidase IV inhibition improves pathophysiology of heart failure and increases survival rate in pressure-overloaded mice

Incretin hormones, including glucagon-like peptide-1 (GLP-1), a target for diabetes mellitus (DM) treatment, are associated with cardioprotection. As dipeptidyl-peptidase IV (DPP-IV) inhibition increases plasma GLP-1 levels in vivo, we investigated the cardioprotective effects of the DPP-IV inhibitor vildagliptin in a murine heart failure (HF) model. We induced transverse aortic constriction (TAC) in C57BL/6J mice, simulating pressure-overloaded cardiac hypertrophy and HF. TAC or sham-operated mice were treated with or without vildagliptin. An intraperitoneal glucose tolerance test revealed that blood glucose levels were higher in the TAC than in sham-operated mice, and these levels improved with vildagliptin administration in both groups. Vildagliptin increased plasma GLP-1 levels in the TAC mice and ameliorated TAC-induced left ventricular enlargement and dysfunction. Vildagliptin palliated both myocardial apoptosis and fibrosis in TAC mice, demonstrated by histological, gene and protein expression analyses, and improved survival rate on day 28 (TAC with vildagliptin, 67.5%; TAC without vildagliptin, 41.5%; P < 0.05). Vildagliptin improved cardiac dysfunction and overall survival in the TAC mice, both by improving impaired glucose tolerance and by increasing GLP-1 levels. DPP-IV inhibitors represent a candidate treatment for HF patients with or without DM.

Metabolic toxicity of the heart: insights from molecular imaging

There is convincing evidence that alterations in myocardial substrate use play an important role in the normal and diseased heart. In this review, insights gained by using quantitative molecular imaging by positron emission tomography and magnetic resonance spectroscopy in the study of human myocardial metabolism will be discussed, and attention will be paid to the effects of nutrition, gender, aging, obesity, diabetes, cardiac hypertrophy, ischemia, and heart failure. The heart is an omnivore organ, relying on metabolic flexibility, which is compromised by the occurrence of defects in coronary flow reserve, insulin-mediated glucose disposal, and metabolic-mechanical coupling. Obesity, diabetes, and ischemic cardiomyopathy appear as states of high uptake and oxidation of fatty acids, that compromise the ability to utilize glucose under stimulated conditions, and lead to misuse of energy and oxygen, disturbing mechanical efficiency. Idiopathic heart failure is a complex disease frequently coexisting with diabetes, insulin resistance and hypertension, in which the end stage of metabolic toxicity manifests as severe mitochondrial disturbance, inability to utilize fatty acids, and ATP depletion. The current literature provides evidence that the primary events in the metabolic cascade outlined may originate in extra-cardiac organs, since fatty acid, glucose levels, and insulin action are mostly controlled by adipose tissue, skeletal muscle and liver, and that a broader vision of organ cross-talk may further our understanding of the primary and the adaptive events involved in metabolic heart toxicity.

Effect of caloric restriction on myocardial fatty acid uptake, left ventricular mass, and cardiac work in obese adults

Obesity is associated with increased fatty acid uptake in the myocardium, and this may have deleterious effects on cardiac function. The aim of this study was to evaluate how weight loss influences myocardial metabolism and cardiac work in obese adults. Thirty-four obese (mean body mass index 33.7 +/- 0.7 kg/m(2)) but otherwise healthy subjects consumed a very low calorie diet for 6 weeks. Cardiac substrate metabolism and work were measured before and after the diet. Myocardial fatty acid uptake was measured in 18 subjects using fluorine-18-fluoro-6-thia-heptadecanoic acid and positron emission tomography, and myocardial glucose uptake was measured in 16 subjects using fluorine-18-2-fluoro-2-deoxyglucose. Myocardial structure and cardiac function were measured using magnetic resonance imaging. Consumption of the very low calorie diet decreased weight (-11.2 +/- 0.6 kg, p <0.0001). Myocardial fatty acid uptake decreased from 4.2 +/- 0.4 to 2.9 +/- 0.2 micromol/100 g/min (p <0.0001). Myocardial mass decreased by 7% (p <0.005), and cardiac work decreased by 26% (p <0.0001). Whole-body insulin sensitivity increased by 33% (p <0.01), but insulin-stimulated myocardial glucose uptake remained unchanged (p = 0.90). Myocardial triglyceride content decreased by 31% (n = 8, p = 0.076). In conclusion, weight reduction decreases myocardial fatty acid uptake in parallel with myocardial mass and cardiac work. These results show that the increased fatty acid uptake found in the hearts of obese patients can be reversed by weight loss.

Exercise training impacts the myocardial metabolism of older individuals in a gender-specific manner

Aging is associated with decreases in aerobic capacity, cardiac function, and insulin sensitivity as well as alterations in myocardial substrate metabolism. Endurance exercise training (EET) improves cardiac function in a gender-specific manner, and EET has been shown to improve whole body glucose tolerance, but its effects on myocardial metabolism are unclear. Accordingly, we studied the effect of EET on myocardial substrate metabolism in older men and women. Twelve healthy older individuals (age: 60-75 yr; 6 men and 6 women) underwent PET with [(15)O]water, [(11)C]acetate, [(11)C]glucose, and [(11)C]palmitate for the assessment of myocardial blood flow (MBF), myocardial O(2) consumption (MVo(2)), myocardial glucose utilization (MGU), and myocardial fatty acid utilization (MFAU), respectively, at rest and during dobutamine infusion (10 microg.kg(-1).min(-1)). Measurements were repeated after 11 mo of EET. Maximal O(2) uptake (Vo(2max)) increased (P = 0.005) after EET. MBF was unaffected by training, as was resting MVo(2); however, posttraining dobutamine MVo(2) was significantly higher (P = 0.05), as was MGU (P < 0.04). Although overall dobutamine MFAU was unchanged, posttraining dobutamine MFAU increased in women (P = 0.01) but decreased in men (P = 0.03). Thus, EET in older individuals improves the catecholamine response of myocardial glucose metabolism. Moreover, gender differences exist in the myocardial fatty acid metabolic response to training. These findings suggest a role for altered myocardial substrate metabolism in modulating the cardiovascular benefits of EET in older individuals.

Metabolic Mechanisms in Heart Failure

Although neurohumoral antagonism has successfully reduced heart failure morbidity and mortality, the residual disability and death rate remains unacceptably high. Though abnormalities of myocardial metabolism are associated with heart failure, recent data suggest that heart failure may itself promote metabolic changes such as insulin resistance, in part through neurohumoral activation. A detrimental self-perpetuating cycle (heart failure --> altered metabolism --> heart failure) that promotes the progression of heart failure may thus be postulated. Accordingly, we review the cellular mechanisms and pathophysiology of altered metabolism and insulin resistance in heart failure. It is hypothesized that the ensuing detrimental myocardial energetic perturbations result from neurohumoral activation, increased adverse free fatty acid metabolism, decreased protective glucose metabolism, and in some cases insulin resistance. The result is depletion of myocardial ATP, phosphocreatine, and creatine kinase with decreased efficiency of mechanical work. On the basis of the mechanisms outlined, appropriate therapies to mitigate aberrant metabolism include intense neurohumoral antagonism, limitation of diuretics, correction of hypokalemia, exercise, and diet. We also discuss more novel mechanistic-based therapies to ameliorate metabolism and insulin resistance in heart failure. For example, metabolic modulators may optimize myocardial substrate utilization to improve cardiac function and exercise performance beyond standard care. The ultimate success of metabolic-based therapy will be manifest by its capacity further to lessen the residual mortality in heart failure.

Safety and Efficacy of Resistance Training in Patients With Chronic Heart Failure: Research‐Based Evidence

Although a rich body of research exists regarding the safety and efficacy of resistance training, health care providers continue to caution patients with heart failure not to engage in this type of exercise. Research studies utilizing resistance training demonstrate improvements in muscular strength and endurance, New York Heart Association functional class, and quality of life. Despite the hemodynamic changes which occur during resistance exercise, no negative outcomes have been reported. The purpose of this paper is to review the most current research regarding the use of resistance training with heart failure patients to provide assistance to clinicians and enable them to provide education and appropriate recommendations to their patients.

Rosiglitazone improves myocardial glucose uptake in patients with type 2 diabetes and coronary artery disease: a 16-week randomized, double-blind, placebo-controlled study

Rosiglitazone therapy improves insulin sensitivity and glucose uptake in patients with uncomplicated type 2 diabetes. In coronary artery disease (CAD), glucose is an important source of energy and preserved myocardial glucose uptake is essential for the viability of jeopardized myocardium. The aim was to test whether rosiglitazone changes myocardial metabolism in type 2 diabetic patients with CAD. We studied 54 patients (38 men and 16 women) with type 2 diabetes (HbA(1c) 7.2 + 0.9%) and CAD. Myocardial glucose uptake was measured with [(18)F]fluoro-2-deoxy-d-glucose positron emission tomography in ischemic (evaluated by single-photon emission tomography and coronary angiography) and nonischemic regions during euglycemic-hyperinsulinemic clamp before and after a 16-week intervention period with rosiglitazone (n = 27) or placebo (n = 27). Rosiglitazone significantly improved glycemic control (P < 0.0001) and whole-body insulin sensitivity (P < 0.0001). Rosiglitazone increased myocardial glucose uptake from 20.6 +/- 11.8 to 25.5 +/- 12.4 micromol . 100 g(-1) . min(-1) (P = 0.038 vs. baseline, P = 0.023 vs. placebo) in ischemic regions and from 21.7 +/- 12.1 to 28.0 +/- 12.7 micromol . 100 g(-1) . min(-1) (P = 0.014 vs. baseline, P = 0.003 vs. placebo) in nonischemic regions. The increase in myocardial glucose uptake was partly explained by the suppression of free fatty acid levels during clamp. Rosiglitazone therapy significantly increased insulin sensitivity and improved myocardial glucose uptake in type 2 diabetic patients with CAD. These results suggest that rosiglitazone therapy may facilitate myocardial glucose storage and utilization in these patients.