Exercise improves cardiac function and attenuates insulin resistance in Dahl salt-sensitive rats

Moderate- and High-Intensity Endurance Training Alleviate Diabetes-Induced Cardiac Dysfunction in Rats

Exercise training is an encouraging approach to treat cardiac dysfunction in type 2 diabetes (T2DM), but the impact of its intensity is not understood. We aim to investigate whether and, if so, how moderate-intensity training (MIT) and high-intensity interval training (HIIT) alleviate adverse cardiac remodeling and dysfunction in rats with T2DM. Male rats received standard chow (n = 10) or Western diet (WD) to induce T2DM. Hereafter, WD rats were subjected to a 12-week sedentary lifestyle (n = 8), running MIT (n = 7) or HIIT (n = 7). Insulin resistance and glucose tolerance were assessed during the oral glucose tolerance test. Plasma advanced glycation end-products (AGEs) were evaluated. Echocardiography and hemodynamic measurements evaluated cardiac function. Underlying cardiac mechanisms were investigated by histology, western blot and colorimetry. We found that MIT and HIIT lowered insulin resistance and blood glucose levels compared to sedentary WD rats. MIT decreased harmful plasma AGE levels. In the heart, MIT and HIIT lowered end-diastolic pressure, left ventricular wall thickness and interstitial collagen deposition. Cardiac citrate synthase activity, mitochondrial oxidative capacity marker, raised after both exercise training modalities. We conclude that MIT and HIIT are effective in alleviating diastolic dysfunction and pathological cardiac remodeling in T2DM, by lowering fibrosis and optimizing mitochondrial capacity.

Physical exercise prevents age-related heart dysfunction induced by high-salt intake and heart salt-specific overexpression in Drosophila

A long-term high-salt intake (HSI) seems to accelerate cardiac aging and age-related diseases, but the molecular mechanism is still not entirely clear. Exercise is an effective way to delay cardiac aging. However, it remains unclear whether long-term exercise (LTE) can protect heart from aging induced by high-salt stress. In this study, heart CG2196(salt) specific overexpression (HSSO) and RNAi (HSSR) was constructed by using the UAS/hand-Gal4 system in Drosophila. Flies were given exercise and a high-salt diet intervention from 1 to 5 weeks of age. Results showed that HSSR and LTE remarkably prevented heart from accelerated age-related defects caused by HSI and HSSO, and these defects included a marked increase in heart period, arrhythmia index, malondialdehyde (MDA) level, salt expression, and dTOR expression, and a marked decrease in fractional shortening, SOD activity level, dFOXO expression, PGC-1α expression, and the number of mitochondria and myofibrils. The combination of HSSR and LTE could better protect the aging heart from the damage of HSI. Therefore, current evidences suggested that LTE resisted HSI-induced heart presenility via blocking CG2196(salt)/TOR/oxidative stress and activating dFOXO/PGC-1α. LTE also reversed heart presenility induced by cardiac-salt overexpression via activating dFOXO/PGC-1α and blocking TOR/oxidative stress.

Preclinical rodent models of cardiac fibrosis

Cardiac fibrosis (scarring), characterised by an increased deposition of extracellular matrix (ECM) proteins, is a hallmark of most types of cardiovascular disease and plays an essential role in heart failure progression. Inhibition of cardiac fibrosis could improve outcomes in patients with cardiovascular diseases and particularly heart failure. However, pharmacological treatment of the ECM build-up is still lacking. In this context, preclinical models of heart disease are important tools for understanding the complex pathogenesis involved in the development of cardiac fibrosis which in turn could identify new therapeutic targets and the facilitation of antifibrotic drug discovery. Many preclinical models have been used to study cardiac fibrosis and each model provides mechanistic insights into the many factors that contribute to cardiac fibrosis. This review discusses the most frequently used rodent models of cardiac fibrosis and also provides context for the use of particular models of heart failure.

High intensity training improves cardiac function in healthy rats

Exercise training is a low cost and safe approach for reducing the risk of cardiovascular disease development. Currently, moderate-intensity training (MIT) is the most preferred exercise type. However, high-intensity interval training (HIIT) is gaining interest especially among athletes and healthy individuals. In this study, we examined cardiac remodeling resulting from MIT and HIIT in healthy rats. Healthy male Sprague-Dawley rats were randomly assigned to MIT or HIIT for 13 weeks. Animals kept sedentary (SED) were used as control. Cardiac function was evaluated with echocardiography and hemodynamic measurements. Heart tissue was stained for capillary density and fibrosis. After 13 weeks of training, only HIIT induced beneficial cardiac hypertrophy. Overall global cardiac parameters (such as ejection fraction, cardiac output and volumes) were improved similarly between both training modalities. At tissue level, collagen content was significantly and similarly reduced in both exercise groups. Finally, only HIIT increased significantly capillary density. Our data indicate that even if very different in design, HIIT and MIT appear to be equally effective in improving cardiac function in healthy rats. Furthermore, HIIT provides additional benefits through improved capillary density and should therefore be considered as a preferred training modality for athletes and for patients.

Effects of prostate cancer and exercise training on left ventricular function and cardiac and skeletal muscle mass

Prostate cancer was found to reduce cardiac and left ventricle (LV) masses in association with diminished exercise capacity in rats. We tested the hypothesis that exercise training will mitigate prostate cancer-induced cardiac and skeletal muscle atrophy and improve LV function versus sedentary tumor-bearing counterparts. Copenhagen rats ( n = 39; ~5 mo old) were randomized into four groups: exercise-trained tumor-bearing (EXTB) or control (EXCON) and sedentary tumor-bearing (SEDTB) or control (SEDCON). Dunning R-3327 prostate cancer cells were injected orthotopically in 19 of the 39 animals. Treadmill exercise training was performed for 60 min/day for ~30 days. Animals underwent echocardiography to examine ventricle dimensions "Pre-" cancer injection or exercise (PRE) and 15 (Post 1) and 32-35 (Post 2) days after cancer cell injection with tissues collected after Post 2. LV TNF-α and IL-6 concentrations were measured post mortem. Cardiac and LV mass of SEDTB animals were lower than all groups ( P < 0.05). Tumor mass was negatively correlated with LV mass in EXTB (-0.75, P < 0.02) and SEDTB animals (-0.72, P < 0.02). EXCON group had higher stroke volume Post 2 assessment compared with both sedentary groups ( P < 0.05) but not EXTB animals. No difference in LV [IL-6] or [TNF-α] was found between the cancer groups. The current investigation demonstrates prostate cancer, independent of anticancer treatment, significantly reduces cardiac mass and LV mass as well as locomotor muscle masses. However, moderate-intensity exercise training can mitigate cardiac and skeletal muscle atrophy with prostate cancer and preserve the cardiac phenotype (i.e., mass and function) to that of the healthy sedentary group. NEW & NOTEWORTHY This study demonstrates the atrophic effects of prostate cancer on cardiac and skeletal muscle mass independent of anticancer treatment(s) that can be mitigated with moderate-intensity exercise. These findings have important implications for potentially improving the quality of life as well as therapeutic outcomes for patients with prostate cancer.

Western diet given to healthy rats mimics the human phenotype of diabetic cardiomyopathy

Diabetes mellitus (DM) is a major problem worldwide. Within this patient group, cardiovascular diseases are the biggest cause of morbidity and mortality. Diabetic cardiomyopathy (DCM) is defined as diabetes-associated structural and functional changes in the myocardium, not directly attributable to other confounding factors such as coronary artery disease or hypertension. Pathophysiology of DCM remains unclear due to a lack of adequate animal models reflecting the current pandemic of diabetes, associated with a high increased sugar intake and the 'Western' lifestyle. The aim of this study was to develop an animal model mimicking this 'Western' lifestyle causing a human-like phenotype of DCM. Twenty-four Sprague-Dawley rats were randomly assigned into a normal or a 'Western' diet group for 18 weeks. Glucose and insulin levels were measured with an OGTT. Heart function was assessed by echocardiography and hemodynamic measurements in vivo. Cardiac fibrosis and inflammation were investigated in vitro. 'Western' diet given to healthy rats for 18 weeks induced hyperglycemia together with increased AGEs levels, insulin levels and hypertriglyceridemia. Heart function was altered with increased end-diastolic pressure, left ventricle hypertrophy. Changes in vivo were associated with increased collagen deposition and increased PAI-1 levels in the heart. High-sugar diet or 'Western' diet causes T2DM and the hallmarks of DCM in rats, reflecting the phenotype of the disease seen in patients. Using this new model of T2DM with DCM might open new insight in understanding the pathophysiology of DCM and on a long term, test targeted therapies for T2DM with DCM patients.

The lysyl oxidase inhibitor (β-aminopropionitrile) reduces leptin profibrotic effects and ameliorates cardiovascular remodeling in diet-induced obesity in rats

Lysyl oxidase (LOX) is an extracellular matrix (ECM)-modifying enzyme that has been involved in cardiovascular remodeling. We explore the impact of LOX inhibition in ECM alterations induced by obesity in the cardiovascular system. LOX is overexpressed in the heart and aorta from rats fed a high-fat diet (HFD). β-Aminopropionitrile (BAPN), an inhibitor of LOX activity, significantly attenuated the increase in body weight and cardiac hypertrophy observed in HFD rats. No significant differences were found in cardiac function or blood pressure among any group. However, HFD rats showed cardiac and vascular fibrosis and enhanced levels of superoxide anion (O2(-)), collagen I and transforming growth factor β (TGF-β) in heart and aorta and connective tissue growth factor (CTGF) in aorta, effects that were attenuated by LOX inhibition. Interestingly, BAPN also prevented the increase in circulating leptin levels detected in HFD fed animals. Leptin increased protein levels of collagen I, TGF-β and CTGF, Akt phosphorylation and O2(-) production in both cardiac myofibroblasts and vascular smooth muscle cells in culture, while LOX inhibition ameliorated these alterations. LOX knockdown also attenuated leptin-induced collagen I production in cardiovascular cells. Our findings indicate that LOX inhibition attenuates the fibrosis and the oxidative stress induced by a HFD on the cardiovascular system. The reduction of leptin levels by BAPN in vivo and the ability of this compound to inhibit leptin-induced profibrotic mediators and ROS production in cardiac and vascular cells suggest that interactions between leptin and LOX regulate downstream events responsible for myocardial and vascular fibrosis in obesity.