Exercise Training Alters Left Ventricular Geometry and Attenuates Heart Failure in Dahl Salt-Sensitive Hypertensive Rats

Quantification of cardiac capillarization in basement-membrane-immunostained myocardial slices using Segment Anything Model

Decreased myocardial capillary density has been reported as an important histopathological feature associated with various heart disorders. Quantitative assessment of cardiac capillarization typically involves double immunostaining of cardiomyocytes (CMs) and capillaries in myocardial slices. In contrast, single immunostaining of basement membrane protein is a straightforward approach to simultaneously label CMs and capillaries, presenting fewer challenges in background staining. However, subsequent image analysis always requires expertise and laborious manual work to identify and segment CMs/capillaries. Here, we developed an image analysis tool, AutoQC, for automatic identification and segmentation of CMs and capillaries in immunofluorescence images of basement membrane. Commonly used capillarization-related measurements can be derived from segmentation results. By leveraging the power of a pre-trained segmentation model (Segment Anything Model, SAM) via prompt engineering, the training of AutoQC required only a small dataset with bounding box annotations instead of pixel-wise annotations. AutoQC outperformed SAM (without prompt engineering) and YOLOv8-Seg, a state-of-the-art instance segmentation model, in both instance segmentation and capillarization assessment. Thus, AutoQC, featuring a weakly supervised algorithm, enables automatic segmentation and high-throughput, high-accuracy capillarization assessment in basement-membrane-immunostained myocardial slices. This approach reduces the training workload and eliminates the need for manual image analysis once AutoQC is trained.

Beneficial Effects of Exercise on Hypertension-Induced Cardiac Hypertrophy in Adolescents and Young Adults

PURPOSE OF REVIEW

Hypertension-induced cardiac hypertrophy is widely known as a major risk factor for increased cardiovascular morbidity and mortality. Although exercise is proven to exert overall beneficial effects on hypertension and hypertension-induced cardiac hypertrophy, there are some concerns among providers about potential adverse effects induced by intense exercise, especially in hypertensive athletes. We will overview the underlying mechanisms of physiological and pathological hypertrophy and delineate the beneficial effects of exercise in young people with hypertension and consequent hypertrophy.

RECENT FINDINGS

Multiple studies have demonstrated that exercise training, both endurance and resistance types, reduces blood pressure and ameliorates hypertrophy in hypertensives, but certain precautions are required for hypertensive athletes when allowing competitive sports: Elevated blood pressure should be controlled before allowing them to participate in high-intensity exercise. Non-vigorous and recreational exercise are always recommended to promote cardiovascular health. Exercise-induced cardiac adaptation is a benign and favorable response that reverses or attenuates pathological cardiovascular remodeling induced by persistent hypertension. Exercise is the most effective nonpharmacological treatment for hypertensive individuals. Distinction between recreational-level exercise and competitive sports should be recognized by medical providers when allowing sports participation for adolescents and young adults.

Changes in physical activity and the risk of heart failure in newly diagnosed patients with depression: A nationwide cohort study

BACKGROUND

Depression is known to increase the risk of heart failure (HF), and physical activity could be a potential mediator of their linkage. In this study, we examined the risk of incident HF according to changes in the level of physical activity before and after the diagnosis of depression.

METHODS

A South Korean National Health Insurance Sharing Service database was used. A total of 1,405,655 patients with newly diagnosed depression were included in the analyses. According to the changes in physical activity based on the recommended level of regular physical activity, participants were divided into four groups: never, beginning, maintenance, and discontinuation. The main outcome was the occurrence of HF.

RESULTS

During the average follow-up period of 5.28 years (SD, 2.00 years), 69,338 participants were diagnosed with HF, with an incidence rate of 9.34 per 1000 person-years. Compared to the never group, the beginning group showed a decreased risk of HF (aHR, 0.88; 95% CI, 0.86-0.90). Compared to the maintenance group, the discontinuation group showed an increased risk of HF (aHR, 1.16; 95% CI, 1.11-1.20).

CONCLUSIONS

In the patients with depression, beginning regular physical activity was associated with a decreased risk of HF, and discontinuing regular physical activity was associated with an increased risk.

Effects of Exercise Training on Mitochondrial Fatty Acid β-Oxidation in the Kidneys of Dahl Salt-Sensitive Rats

Exercise training (Ex) has anti-hypertensive and renal protective effects. In this study, we investigate the effects of Ex on mitochondrial fatty acid metabolism in the kidneys of Dahl salt-sensitive (Dahl-S) rats fed a high-salt (HS) diet. Eight-week-old, male Dahl-S rats were divided into three groups: (1) normal-salt diet, sedentary (NS-Sed), (2) HS diet, sedentary (HS-Sed), and (3) HS-Ex. The NS and HS groups were fed a diet containing 0.6% and 8% NaCl, respectively. The HS-Ex group performed treadmill running for 8 weeks (5 days/week; 60 min/day at 16-20 m/min, 0% gradient). Renal function and the expression of enzymes and regulators of β-oxidation and electron transport chain (ETC) complexes were assessed. HS increased systolic blood pressure and proteinuria, and Ex ameliorated these defects. HS also reduced creatinine clearance, and Ex ameliorated it. HS reduced the renal expression of enzymes of β-oxidation (carnitine palmitoyltransferase type I (CPTI) and acyl-CoA dehydrogenases (CADs)) and the related transcription factors peroxisome proliferator-activated receptor α (PPARα) and PPARγ-coactivator-1α (PGC-1α), and Ex restored this. HS also reduced the renal expression of enzymes in ETC complexes, and Ex restored this expression. Ex ameliorates HS-induced renal damage by upregulating enzymes involved in fatty acid β-oxidation and ETC complexes via increases in PPAR-α and PGC-1α expressions in the kidneys of Dahl-S rats. These results suggest that Ex may have beneficial effects on HS-induced mitochondrial dysfunction in the kidney.

Effects of early exercise on cardiac function and lipid metabolism pathway in heart failure

We employed an early training exercise program, immediately after recovery from surgery, and before severe cardiac hypertrophy, to study the underlying mechanism involved with the amelioration of cardiac dysfunction in aortic stenosis (AS) rats. As ET induces angiogenesis and oxygen support, we aimed to verify the effect of exercise on myocardial lipid metabolism disturbance. Wistar rats were divided into Sham, trained Sham (ShamT), AS and trained AS (AST). The exercise consisted of 5-week sessions of treadmill running for 16 weeks. Statistical analysis was conducted by anova or Kruskal-Wallis test and Goodman test. A global correlation between variables was also performed using a two-tailed Pearson's correlation test. AST rats displayed a higher functional capacity and a lower cardiac remodelling and dysfunction when compared to AS, as well as the myocardial capillary rarefaction was prevented. Regarding metabolic properties, immunoblotting and enzymatic assay raised beneficial effects of exercise on fatty acid transport and oxidation pathways. The correlation assessment indicated a positive correlation between variables of angiogenesis and FA utilisation, as well as between metabolism and echocardiographic parameters. In conclusion, early exercise improves exercise tolerance and attenuates cardiac structural and functional remodelling. In parallel, exercise attenuated myocardial capillary and lipid metabolism derangement in rats with aortic stenosis-induced heart failure.

Anti-apoptotic and anti-fibrotic efficacy of exercise training in hypertensive hearts: A systematic review

Background

This review aims to summarize the antiapoptotic, pro-survival, and antifibrotic effects of exercise training in hypertensive hearts.

Methods

Keyword searches were conducted in PubMed, Web of Science, and Scopus in May 2021. Research published in English on the effects of exercise training on the apoptosis, survival, and fibrosis pathways in hypertension was included. The CAMARADES checklist was used to determine the quality of the studies. Two reviewers independently implemented predesigned protocols for the search and selection of studies, the assessment of study quality, and the evaluation of the strength of evidence.

Results

Eleven studies were included after selection. The duration of the exercise training ranged from 5 to 27 weeks. Nine studies showed that exercise training improved cardiac survival rates by increasing IGF-1, IGF-1 receptor, p-PI3K, Bcl-2, HSP 72, and p-Akt. Furthermore, 10 studies showed that exercise training reduced apoptotic pathways by downregulating Bid, t-Bid, Bad, Bak, Bax, TNF, and FADD. Finally, two studies reported the modification and subsequent improvement of physiological characteristics of fibrosis and decreased MAPK p38 and PTEN levels by exercise training in the left ventricle of the heart.

Conclusions

The findings of the review showed that exercise training could improve cardiac survival rates and attenuate cardiac apoptotic and fibrotic pathways in hypertension, suggesting that exercise training could act as a therapeutic approach to prevent hypertension-induced cardiac apoptosis and fibrosis.

Systematic Review Registration

https://www.crd.york.ac.uk, identifier: CRD42021254118.

The effects of ambient fine particulate matter exposure and physical activity on heart failure: A risk-benefit analysis of a prospective cohort study

BACKGROUND

Evidence supporting the adverse effects of air pollution and the benefits of physical activity (PA) on heart failure (HF) has continued to grow. However, their joint effects remain largely unknown.

METHODS

Our investigation included a total of 321,672 participants free of HF at baseline from the UK Biobank. Participants were followed up till March 2021. Information on participants' PA levels and additional covariates was collected by questionnaire. The annual fine particulate matter (PM_2.5) concentration was estimated using a Land Use Regression (LUR) model. Cox proportional hazards models were used to assess the associations of PA and PM_2.5 exposure with incident HF, as well as their interaction on both additive and multiplicative scales.

RESULTS

During a median follow-up of 12.0 years, 8212 cases of HF were uncovered. Compared with participants with low PA, the hazard ratios (HRs) were 0.69 (95 % CI: 0.65, 0.73) and 0.61 (95 % CI: 0.58, 0.65) for those with moderate and high PA, respectively. PM_2.5 was associated with an elevated risk of incident HF with an HR of 1.11 (95 % CI: 1.08, 1.14) per interquartile range (IQR) increment. The synergistic additive interaction between low PA and high PM_2.5 exposure on HF was observed. Compared with participants with high PA and low PM_2.5 exposure, those with low PA and high PM_2.5 exposure had the highest risk of HF [HR (95 % CI): 1.90 (1.76, 2.06)].

CONCLUSIONS

Our findings indicate that PA might still be an appropriate strategy to prevent HF for those living in areas with relatively high air pollution. Individuals with low PA may pay more attention to air pollution.

The high-intensity interval training mitigates the cardiac remodeling in spontaneously hypertensive rats

AIM

To evaluate the influence of high-intensity interval training (HIIT) on cardiac structural and functional characteristics and myocardial mitogen-activated protein kinase (MAPK) signaling in hypertensive rats.

METHODS

Male rats (12 months old) were divided into three groups: Wistar Kyoto rats (WKY, n = 8); sedentary spontaneously hypertensive rats (SED-SHR, n = 10), and trained spontaneously hypertensive rats (HIIT-SHR, n = 10). Systolic blood pressure (SBP), functional capacity, echocardiography, isolated papillary muscle, and gene expression of MAPK gene-encoding proteins associated with Elk1, cJun, ATF2, MEF2 were analyzed.

KEY FINDINGS

HIIT decreased SBP and increased functional capacity, left ventricular diastolic diameter, posterior wall thickness-left ventricle, relative wall thickness-left ventricle, and resting tension of the papillary muscle. In hypertensive rats, we observed a decrease in the gene-encoding ATF2 protein; this decrease was reversed by HIIT.

SIGNIFICANCE

The influence of HIIT in the SHR model in the compensated hypertension phase generated an increase in cardiac hypertrophy, attenuated myocardial diastolic dysfunction, lowered blood pressure, improved functional capacity, and reversed the alteration in gene-encoding ATF2 protein.

Effects of Exercise Training on the Renin-Angiotensin System in the Kidneys of Dahl Salt-Sensitive Rats

PURPOSE

Exercise training (Ex) has antihypertensive and renal protective effects; however, the precise mechanisms remain unclear. The renal renin-angiotensin system (RAS) plays a vital role in renal function and pathology. Therefore, we investigated the effects of Ex on the renal RAS components in Dahl salt-sensitive (Dahl-S) rats.

METHODS

Male Dahl-S rats were divided into four groups: normal salt diet + sedentary, normal salt diet + Ex, high-salt diet (HS, 8% NaCl) + sedentary, and HS + Ex. Treadmill running was performed for 8 wk in the Ex groups.

RESULTS

Ex attenuated the HS-induced renal dysfunction and glomerular injury without causing blood pressure alterations. HS increased urinary excretion of both total and intact angiotensinogen. Ex decreased the HS-induced increased urinary excretion of total angiotensinogen. However, it did not change the HS-induced urinary excretion of intact angiotensinogen, indicating reduced intact angiotensinogen cleaving. Ex restored the HS-induced increased angiotensinogen and angiotensin II type 1 receptor expressions in the outer medulla and the HS-induced increased angiotensin-converting enzyme expression in the cortex. Ex restored the HS-induced decreased renin expression in the cortex and outer medulla, and the HS-induced decreased angiotensin-converting enzyme 2, angiotensin II type 2 receptor, and Mas receptor expressions in the outer medulla.

CONCLUSIONS

Ex attenuates HS-induced renal dysfunction, glomerular injury, and renal RAS dysregulation in Dahl-S rats.

Capillaries as a Therapeutic Target for Heart Failure

Prognosis of heart failure remains poor, and it is urgent to find new therapies for this critical condition. Oxygen and metabolites are delivered through capillaries; therefore, they have critical roles in the maintenance of cardiac function. With aging or age-related disorders, capillary density is reduced in the heart, and the mechanisms involved in these processes were reported to suppress capillarization in this organ. Studies with rodents showed capillary rarefaction has causal roles for promoting pathologies in failing hearts. Drugs used as first-line therapies for heart failure were also shown to enhance the capillary network in the heart. Recently, the approach with senolysis is attracting enthusiasm in aging research. Genetic or pharmacological approaches concluded that the specific depletion of senescent cells, senolysis, led to reverse aging phenotype. Reagents mediating senolysis are described to be senolytics, and these compounds were shown to ameliorate cardiac dysfunction together with enhancement of capillarization in heart failure models. Studies indicate maintenance of the capillary network as critical for inhibition of pathologies in heart failure.

Pharmacological inhibition of the lipid phosphatase PTEN ameliorates heart damage and adipose tissue inflammation in stressed rats with metabolic syndrome

Phosphatidylinositol 3-kinase (PI3K) signaling promotes the differentiation and proliferation of regulatory B (Breg) cells, and the lipid phosphatase phosphatase and tensin homolog deleted on chromosome 10 (PTEN) antagonizes the PI3K-Akt signaling pathway. We previously demonstrated that cardiac Akt activity is increased and that restraint stress exacerbates hypertension and both heart and adipose tissue (AT) inflammation in DS/obese rats, an animal model of metabolic syndrome (MetS). We here examined the effects of restraint stress and pharmacological inhibition of PTEN on heart and AT pathology in such rats. Nine-week-old animals were treated with the PTEN inhibitor bisperoxovanadium-pic [bpV(pic)] or vehicle in the absence or presence of restraint stress for 4 weeks. BpV(pic) treatment had no effect on body weight or fat mass but attenuated hypertension in DS/obese rats subjected to restraint stress. BpV(pic) ameliorated left ventricular (LV) inflammation, fibrosis, and diastolic dysfunction as well as AT inflammation in the stressed rats. Restraint stress reduced myocardial capillary density, and this effect was prevented by bpV(pic). In addition, bpV(pic) increased the proportions of Breg and B-1 cells as well as reduced those of CD8+ T and B-2 cells in AT of stressed rats. Our results indicate that inhibition of PTEN by bpV(pic) alleviated heart and AT inflammation in stressed rats with MetS. These positive effects of bpV(pic) are likely due, at least in part, to a reduction in blood pressure, an increase in myocardial capillary formation, and an altered distribution of immune cells in fat tissue that result from the activation of PI3K-Akt signaling.

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.

Physical activity and the risk of heart failure: a systematic review and dose-response meta-analysis of prospective studies

Although physical activity is an established protective factor for cardiovascular diseases such as ischemic heart disease and stroke, less is known with regard to the association between specific domains of physical activity and heart failure, as well as the association between cardiorespiratory fitness and heart failure. We conducted a systematic review and meta-analysis of prospective observational studies to clarify the relations of total physical activity, domains of physical activity and cardiorespiratory fitness to risk of heart failure. PubMed and Embase databases were searched up to January 14th, 2020. Summary relative risks (RRs) were calculated using random effects models. Twenty-nine prospective studies (36 publications) were included in the review. The summary RRs for high versus low levels were 0.77 (95% CI 0.70–0.85, I² = 49%, n = 7) for total physical activity, 0.74 (95% CI 0.68–0.81, I² = 88.1%, n = 16) for leisure-time activity, 0.66 (95% CI 0.59–0.74, I² = 0%, n = 2) for vigorous activity, 0.81 (95% CI 0.69–0.94, I² = 86%, n = 3) for walking and bicycling combined, 0.90 (95% CI 0.86–0.95, I² = 0%, n = 3) for occupational activity, and 0.31 (95% CI 0.19–0.49, I² = 96%, n = 6) for cardiorespiratory fitness. In dose–response analyses, the summary RRs were 0.89 (95% CI 0.83–0.95, I² = 67%, n = 4) per 20 MET-hours per day of total activity and 0.71 (95% CI 0.65–0.78, I² = 85%, n = 11) per 20 MET-hours per week of leisure-time activity. Nonlinear associations were observed in both analyses with a flattening of the dose–response curve at 15–20 MET-hours/week for leisure-time activity. These findings suggest that high levels of total physical activity, leisure-time activity, vigorous activity, occupational activity, walking and bicycling combined and cardiorespiratory fitness are associated with reduced risk of developing heart failure.

Alleviation of salt-induced exacerbation of cardiac, renal, and visceral fat pathology in rats with metabolic syndrome by surgical removal of subcutaneous fat

OBJECTIVES

Evidence suggests that visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) should be considered as distinct types of white fat. Although VAT plays a key role in metabolic syndrome (MetS), the role of subcutaneous adipose tissue (SAT) has been unclear. DahlS.Z-Lepr^fa/Lepr^fa (DS/obese) rats, an animal model of MetS, develop adipocyte hypertrophy and inflammation to similar extents in SAT and VAT. We have now investigated the effects of salt loading and SAT removal on cardiac, renal, and VAT pathology in DS/obese rats.

METHODS

DS/obese rats were subjected to surgical removal of inguinal SAT or sham surgery at 8 weeks of age. They were provided with a 0.3% NaCl solution as drinking water or water alone for 4 weeks from 9 weeks of age.

RESULTS

Salt loading exacerbated hypertension, insulin resistance, as well as left ventricular (LV) hypertrophy, inflammation, fibrosis, and diastolic dysfunction in DS/obese rats. It also reduced both SAT and VAT mass but aggravated inflammation only in VAT. Although SAT removal did not affect LV hypertrophy in salt-loaded DS/obese rats, it attenuated hypertension, insulin resistance, and LV injury as well as restored fat mass and alleviated inflammation and the downregulation of adiponectin gene expression in VAT. In addition, whereas salt loading worsened renal injury as well as upregulated the expression of renin-angiotensin-aldosterone system-related genes in the kidney, these effects were suppressed by removal of SAT.

CONCLUSIONS

SAT removal attenuated salt-induced exacerbation of MetS and LV and renal pathology in DS/obese rats. These beneficial effects of SAT removal are likely attributable, at least in part, to inhibition of both VAT and systemic inflammation.

Morphometric, Hemodynamic, and Multi-Omics Analyses in Heart Failure Rats with Preserved Ejection Fraction

(1) Background: There are no successive treatments for heart failure with preserved ejection fraction (HFpEF) because of complex interactions between environmental, histological, and genetic risk factors. The objective of the study is to investigate changes in cardiomyocytes and molecular networks associated with HFpEF. (2) Methods: Dahl salt-sensitive (DSS) rats developed HFpEF when fed with a high-salt (HS) diet for 7 weeks, which was confirmed by in vivo and ex vivo measurements. Shotgun proteomics, microarray, Western blot, and quantitative RT-PCR analyses were further carried out to investigate cellular and molecular mechanisms. (3) Results: Rats with HFpEF showed diastolic dysfunction, impaired systolic function, and prolonged repolarization of myocytes, owing to an increase in cell size and apoptosis of myocytes. Heatmap of multi-omics further showed significant differences between rats with HFpEF and controls. Gene Set Enrichment Analysis (GSEA) of multi-omics revealed genetic risk factors involved in cardiac muscle contraction, proteasome, B cell receptor signaling, and p53 signaling pathway. Gene Ontology (GO) analysis of multi-omics showed the inflammatory response and mitochondrial fission as top biological processes that may deteriorate myocyte stiffening. GO analysis of protein-to-protein network indicated cytoskeleton protein, cell fraction, enzyme binding, and ATP binding as the top enriched molecular functions. Western blot validated upregulated Mff and Itga9 and downregulated Map1lc3a in the HS group, which likely contributed to accumulation of aberrant mitochondria to increase ROS and elevation of myocyte stiffness, and subsequent contractile dysfunction and myocardial apoptosis. (4) Conclusions: Multi-omics analysis revealed multiple pathways associated with HFpEF. This study shows insight into molecular mechanisms for the development of HFpEF and may provide potential targets for the treatment of HFpEF.

Exercise training delays renal disorders with decreasing oxidative stress and increasing production of 20-hydroxyeicosatetraenoic acid in Dahl salt-sensitive rats

OBJECTIVE

Exercise training has antihypertensive and renoprotective effects in humans and rats. However, the effects of exercise training on renal disorders that occur with salt-sensitive hypertension remains unclear. The study aim was to investigate the effects and mechanisms of exercise training on renal function in a rat model of salt-sensitive hypertension.

METHODS

Six-week-old male Dahl salt-sensitive rats were divided into normal-salt (0.6% NaCl) diet, high-salt (8% NaCl) diet, and high-salt diet with exercise training groups. The high-salt diet with exercise training group underwent daily treadmill running for 8 weeks.

RESULTS

The high-salt diet induced severe hypertension and renal dysfunction. Exercise training significantly improved high-salt diet-induced urinary protein, albumin, and L-type fatty acid-binding protein excretion, and glomerulosclerosis but not renal interstitial fibrosis without changing blood pressure. Exercise training significantly attenuated high-salt diet-induced oxidative stress in the kidneys and decreased high-salt diet-stimulated xanthine oxidoreductase activity but not nicotinamide adenine dinucleotide phosphate oxidase activity. The high-salt diet did not change urinary excretion of 20-hydroxyeicosatetraenoic acid and decreased cytochrome P450 4A protein expression in the kidneys. Exercise training increased urinary 20-hydoroxyeicosatetraenoic acid excretion and renal cytochrome P450 4A protein expression.

CONCLUSION

Exercise training improved renal disorders without lowering blood pressure in Dahl salt-sensitive rats. Exercise training also decreased oxidative stress and increased 20-hydroxyeicosatetraenoic acid production in the kidneys. These results suggest that improvements in oxidative stress and 20-hydroxyeicosatetraenoic acid production may be potential mechanisms by which exercise training improved renal disorders in Dahl salt-sensitive rats.

Short-term exercise training improves cardiac function associated to a better antioxidant response and lower type 3 iodothyronine deiodinase activity after myocardial infarction

Aims

We assessed the effects of a short-term exercise training on cardiac function, oxidative stress markers, and type 3 iodothyronine deiodinase (D3) activity in cardiac tissue of spontaneously hypertensive rats (SHR) following experimental myocardial infarction (MI).

Methods

Twenty-four SHR (aged 3 months) were allocated to 4 groups: sham+sedentary, sham+trained, MI+sedentary and MI+trained. MI was performed by permanent ligation of the coronary artery. Exercise training (treadmill) started 96 hours after MI and lasted for 4 weeks (~60% maximum effort, 4x/week and 40 min/day). Cardiac function (echocardiography), thioredoxin reductase (TRx), total carbonyl levels, among other oxidative stress markers and D3 activity were measured. A Generalized Estimating Equation was used, followed by Bonferroni’s test (p<0.05).

Results

MI resulted in an increase in left ventricular mass (p = 0.002) with decreased cardiac output (~22.0%, p = 0.047) and decreased ejection fraction (~41%, p = 0.008) as well as an increase in the carbonyl levels (p = 0.001) and D3 activity (~33%, p<0.001). Exercise training resulted in a decrease in left ventricular mass, restored cardiac output (~34%, p = 0.048) and ejection fraction (~20%, p = 0.040), increased TRx (~85%, p = 0.007) and reduced carbonyl levels (p<0.001) and D3 activity (p<0.001).

Conclusions

Our short-term exercise training helped reverse the effects of MI on cardiac function. These benefits seem to derive from a more efficient antioxidant response and lower D3 activity in cardiac tissue.

Exercise during transition from compensated left ventricular hypertrophy to heart failure in aortic stenosis rats

We evaluated the influence of aerobic exercise on cardiac remodelling during the transition from compensated left ventricular (LV) hypertrophy to clinical heart failure in aortic stenosis (AS) rats. Eighteen weeks after AS induction, rats were assigned into sedentary (AS) and exercised (AS-Ex) groups. Results were compared to Sham rats. Exercise was performed on treadmill for 8 weeks. Exercise improved functional capacity. Echocardiogram showed no differences between AS-Ex and AS groups. After exercise, fractional shortening and ejection fraction were lower in AS-Ex than Sham. Myocyte diameter and interstitial collagen fraction were higher in AS and AS-Ex than Sham; however, myocyte diameter was higher in AS-Ex than AS. Myocardial oxidative stress, evaluated by lipid hydroperoxide concentration, was higher in AS than Sham and was normalized by exercise. Gene expression of the NADPH oxidase subunits NOX2 and NOX4, which participate in ROS generation, did not differ between groups. Activity of the antioxidant enzyme superoxide dismutase was lower in AS and AS-Ex than Sham and glutathione peroxidase was lower in AS-Ex than Sham. Total and reduced myocardial glutathione, which is involved in cellular defence against oxidative stress, was lower in AS than Sham and total glutathione was higher in AS-Ex than AS. The MAPK JNK was higher in AS-Ex than Sham and AS groups. Phosphorylated P38 was lower in AS-Ex than AS. Despite improving functional capacity, aerobic exercise does not change LV function in AS rats. Exercise restores myocardial glutathione, reduces oxidative stress, impairs JNK signalling and further induces myocyte hypertrophy.

Molecular effects of exercise training in patients with cardiovascular disease: focus on skeletal muscle, endothelium, and myocardium

For decades, we have known that exercise training exerts beneficial effects on the human body, and clear evidence is available that a higher fitness level is associated with a lower incidence of suffering premature cardiovascular death. Despite this knowledge, it took some time to also incorporate physical exercise training into the treatment plan for patients with cardiovascular disease (CVD). In recent years, in addition to continuous exercise training, further training modalities such as high-intensity interval training and pyramid training have been introduced for coronary artery disease patients. The beneficial effect for patients with CVD is clearly documented, and during the last years, we have also started to understand the molecular mechanisms occurring in the skeletal muscle (limb muscle and diaphragm) and endothelium, two systems contributing to exercise intolerance in these patients. In the present review, we describe the effects of the different training modalities in CVD and summarize the molecular effects mainly in the skeletal muscle and cardiovascular system.

Highly purified eicosapentaenoic acid ameliorates cardiac injury and adipose tissue inflammation in a rat model of metabolic syndrome

INTRODUCTION

n-3 Polyunsaturated fatty acids such as eicosapentaenoic acid (EPA), which are abundant in fish oil, have been shown to delay the onset of cardiovascular events. We previously established DahlS.Z-Lepr^fa/Lepr^fa (DS/obese) rats, which are derived from a cross between Dahl salt-sensitive and Zucker rats, as a model of metabolic syndrome. This study has now explored the influence of highly purified EPA on cardiac and adipose tissue pathophysiology in this animal model.

MATERIALS AND METHODS

DS/obese rats were administered EPA (300 or 1,000 mg kg^-1 d^-1, per os) or vehicle from age 9 to 13 weeks. Homozygous lean (DahlS.Z-Lepr⁺/Lepr⁺, or DS/lean) littermates were studied as controls.

RESULTS

Whereas EPA had no effect on body weight, food intake or systolic blood pressure in DS/obese rats, it attenuated cardiac fibrosis, diastolic dysfunction, oxidative stress and inflammation in these animals. In addition, EPA did not affect insulin resistance but reduced adipocyte hypertrophy and inflammation in visceral fat of DS/obese rats. Moreover, EPA increased circulating levels of adiponectin as well as attenuated both the down-regulation of AMP-activated protein kinase phosphorylation and the up-regulation of phosphorylation of the p65 subunit of nuclear factor-kB in the heart of DS/obese rats.

CONCLUSIONS

Treatment of DS/obese rats with EPA did not affect hypertension but reduced cardiac fibrosis and diastolic dysfunction, with the latter effects being accompanied by AMP-activated protein kinase activation and inactivation of nuclear factor-kB signalling in the heart, possibly as a result of an increase in adiponectin secretion. EPA may be suitable for the treatment of cardiac injury associated with metabolic syndrome.

Preventing heart failure: the role of physical activity

PURPOSE OF REVIEW

Heart failure prevention is an important public health goal. Increased physical activity and exercise may help to prevent heart failure, as they are associated with reduced heart failure incidence and potentially act through a variety of mechanisms to slow disease progression.

RECENT FINDINGS

Increased physical activity, higher cardiorespiratory fitness, and lower sedentary time are associated with reduced heart failure incidence. These associations are consistent for occurrence of heart failure with both preserved and reduced ejection fraction, the common subphenotypes of the condition. Physiologic cardiac and vascular remodeling occurs across the normal range of physical activity in the community, and regular exercise (four to five sessions per week) is necessary to mitigate age-associated reductions in ventricular compliance and cardiac mass.

SUMMARY

Greater physical activity, less sedentary time, and improved cardiorespiratory fitness are associated with reductions in heart failure risk. Various mechanisms may explain these findings, including: reducing the prevalence of standard and novel cardiovascular risk factors, inhibiting pathologic cardiovascular remodeling, promoting physiologic remodeling, and improving cardiac, neurohormonal, skeletal muscle, pulmonary, renal, and vascular performance. Future research is needed to elucidate the optimal timing, duration, and modality of physical activity and exercise training necessary to prevent the development of heart failure.

Restraint stress exacerbates cardiac and adipose tissue pathology via β-adrenergic signaling in rats with metabolic syndrome

Restraint stress stimulates sympathetic nerve activity and can affect adiposity and metabolism. However, the effects of restraint stress on cardiovascular and metabolic disorders in metabolic syndrome (MetS) have remained unclear. We investigated the effects of chronic restraint stress and β-adrenergic receptor (β-AR) blockade on cardiac and adipose tissue pathology and metabolic disorders in a rat model of MetS. DahlS.Z- Leprfa/ Leprfa (DS/obese) rats, derived from a cross between Dahl salt-sensitive and Zucker rats. Rats were exposed to restraint stress (restraint cage, 2 h/day) for 4 wk from 9 wk of age with or without daily subcutaneous administration of the β-AR blocker propranolol (2 mg/kg). Age-matched homozygous lean littermates of DS/obese rats (DahlS.Z- Lepr+ /Lepr+ rats) served as control animals. Chronic restraint stress exacerbated hypertension as well as left ventricular hypertrophy, fibrosis, diastolic dysfunction, and oxidative stress in a manner sensitive to propranolol treatment. Restraint stress attenuated body weight gain in DS/obese rats, and this effect tended to be reversed by propranolol ( P = 0.0682). Restraint stress or propranolol did not affect visceral or subcutaneous fat mass. However, restraint stress potentiated cardiac and visceral adipose tissue inflammation in DS/obese rats, and these effects were ameliorated by propranolol. Restraint stress also exacerbated glucose intolerance, insulin resistance, and abnormal lipid metabolism in a manner sensitive to propranolol. In addition, restraint stress increased urinary norepinephrine excretion, and propranolol attenuated this effect. Our results thus implicate β-ARs in the exacerbation of cardiac and adipose tissue pathology and abnormal glucose and lipid metabolism induced by restraint stress in this model of MetS.

High intensity interval and endurance training have opposing effects on markers of heart failure and cardiac remodeling in hypertensive rats

There has been re-emerging interest and significant work dedicated to investigating the metabolic effects of high intensity interval training (HIIT) in recent years. HIIT is considered to be a time efficient alternative to classic endurance training (ET) that elicits similar metabolic responses in skeletal muscle. However, there is a lack of information on the impact of HIIT on cardiac muscle in disease. Therefore, we determined the efficacy of ET and HIIT to alter cardiac muscle characteristics involved in the development of diastolic dysfunction, such as ventricular hypertrophy, fibrosis and angiogenesis, in a well-established rodent model of hypertension-induced heart failure before the development of overt heart failure. ET decreased left ventricle fibrosis by ~40% (P < 0.05), and promoted a 20% (P<0.05) increase in the left ventricular capillary/fibre ratio, an increase in endothelial nitric oxide synthase protein (P<0.05), and a decrease in hypoxia inducible factor 1 alpha protein content (P<0.05). In contrast, HIIT did not decrease existing fibrosis, and HIIT animals displayed a 20% increase in left ventricular mass (P<0.05) and a 20% decrease in cross sectional area (P<0.05). HIIT also increased brain natriuretic peptide by 50% (P<0.05), in the absence of concomitant angiogenesis, strongly suggesting pathological cardiac remodeling. The current data support the longstanding belief in the effectiveness of ET in hypertension. However, HIIT promoted a pathological adaptation in the left ventricle in the presence of hypertension, highlighting the need for further research on the widespread effects of HIIT in the presence of disease.

Autophagic signaling and proteolytic enzyme activity in cardiac and skeletal muscle of spontaneously hypertensive rats following chronic aerobic exercise

Hypertension is a cardiovascular disease associated with deleterious effects in skeletal and cardiac muscle. Autophagy is a degradative process essential to muscle health. Acute exercise can alter autophagic signaling. Therefore, we aimed to characterize the effects of chronic endurance exercise on autophagy in skeletal and cardiac muscle of normotensive and hypertensive rats. Male Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) were assigned to a sedentary condition or 6 weeks of treadmill running. White gastrocnemius (WG) of hypertensive rats had higher (p<0.05) caspase-3 and proteasome activity, as well as elevated calpain activity. In addition, skeletal muscle of hypertensive animals had elevated (p<0.05) ATG7 and LC3I protein, LAMP2 mRNA, and cathepsin activity, indicative of enhanced autophagic signaling. Interestingly, chronic exercise training increased (p<0.05) Beclin-1, LC3, and p62 mRNA as well as proteasome activity, but reduced (p<0.05) Beclin-1 and ATG7 protein, as well as decreased (p<0.05) caspase-3, calpain, and cathepsin activity. Left ventricle (LV) of hypertensive rats had reduced (p<0.05) AMPKα and LC3II protein, as well as elevated (p<0.05) p-AKT, p-p70S6K, LC3I and p62 protein, which collectively suggest reduced autophagic signaling. Exercise training had little effect on autophagy-related signaling factors in LV; however, exercise training increased (p<0.05) proteasome activity but reduced (p<0.05) caspase-3 and calpain activity. Our results suggest that autophagic signaling is altered in skeletal and cardiac muscle of hypertensive animals. Regular aerobic exercise can effectively alter the proteolytic environment in both cardiac and skeletal muscle, as well as influence several autophagy-related factors in skeletal muscle of normotensive and hypertensive rats.

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

BACKGROUND

The development of heart failure (HF) secondary to hypertension is a complex process related to a series of physiological and molecular factors including glucose dysregulation. The overall objective of this study was to investigate whether exercise training could improve cardiac function and insulin resistance in a rat model of hypertensive HF.

METHODS

Seven week old Dahl salt-sensitive rats received either 8% NaCl (n = 30) or 0.3% NaCl (n = 18) diet. After a 5-week diet, animals were randomly assigned to exercise training (treadmill running at 18 m/min, 5% inclination for 60 min, 5 days/week) or kept sedentary for 6 additional weeks. 2D echocardiography was used to calculate left ventricular (LV) dimensions, volumes and global functional parameters. LV global deformation parameters were measured with speckle tracking echocardiography. Insulin resistance was assessed using 1h oral glucose tolerance testing.

RESULTS

High salt diet led to cardiac hypertrophy and HF, characterized by increased wall thicknesses and LV volumes as well as reduced deformation parameters. In addition, high salt diet was associated with the development of insulin resistance. Exercise training improved cardiac function, reduced the extent of interstitial fibrosis and reduced insulin levels 60 min post-glucose administration.

CONCLUSIONS

Even if not fully reversed, exercise training in HF animals improved cardiac function and insulin resistance. Adjusted modalities of exercise training might offer new insights not only as a preventive strategy, but also as a treatment for HF patients.

Changes in mid-life fitness predicts heart failure risk at a later age independent of interval development of cardiac and noncardiac risk factors: the Cooper Center Longitudinal Study

AIMS

Low mid-life fitness is associated with higher risk for heart failure (HF). However, it is unclear to what extent this HF risk is modifiable and mediated by the burden of cardiac and noncardiac comorbidities. We studied the effect of cardiac and noncardiac comorbidities on the association of mid-life fitness and fitness change with HF risk.

METHODS

Linking individual subject data from the Cooper Center Longitudinal Study (CCLS) with Medicare claims files, we studied 19,485 subjects (21.2% women) who survived to receive Medicare coverage from 1999 to 2009. Fitness estimated by Balke treadmill time at mean age of 49 years was analyzed as a continuous variable (in metabolic equivalents [METs]) and according to age- and sex-specific quintiles. Associations of mid-life fitness and fitness change with HF hospitalization after age of 65 years were assessed by applying a proportional hazards recurrent events model to the failure time data with each comorbidity entered as time-dependent covariates.

RESULTS

After 127,110 person years of Medicare follow-up, we observed 1,038 HF hospitalizations. Higher mid-life fitness was associated with a lower risk for HF hospitalization (hazard ratio [HR] 0.82 [0.76-0.87] per MET) after adjustment for traditional risk factors. This remained unchanged after further adjustment for the burden of Medicare-identified cardiac and noncardiac comorbidities (HR 0.83 [0.78-0.89]). Each 1 MET improvement in mid-life fitness was associated with a 17% lower risk for HF hospitalization in later life (HR 0.83 [0.74-0.93] per MET).

CONCLUSIONS

Mid-life fitness is an independent and modifiable risk factor for HF hospitalization at a later age.

Dietary salt restriction improves cardiac and adipose tissue pathology independently of obesity in a rat model of metabolic syndrome

Background

Metabolic syndrome (MetS) enhances salt sensitivity of blood pressure and is an important risk factor for cardiovascular disease. The effects of dietary salt restriction on cardiac pathology associated with metabolic syndrome remain unclear.

Methods and Results

We investigated whether dietary salt restriction might ameliorate cardiac injury in DahlS.Z‐Lepr^fa/Lepr^fa (DS/obese) rats, which are derived from a cross between Dahl salt‐sensitive and Zucker rats and represent a model of metabolic syndrome. DS/obese rats were fed a normal‐salt (0.36% NaCl in chow) or low‐salt (0.0466% NaCl in chow) diet from 9 weeks of age and were compared with similarly treated homozygous lean littermates (DahlS.Z‐Lepr⁺/Lepr⁺, or DS/lean rats). DS/obese rats fed the normal‐salt diet progressively developed hypertension and showed left ventricular hypertrophy, fibrosis, and diastolic dysfunction at 15 weeks. Dietary salt restriction attenuated all of these changes in DS/obese rats. The levels of cardiac oxidative stress and inflammation and the expression of cardiac renin–angiotensin–aldosterone system genes were increased in DS/obese rats fed the normal‐salt diet, and dietary salt restriction downregulated these parameters in both DS/obese and DS/lean rats. In addition, dietary salt restriction attenuated the increase in visceral adipose tissue inflammation and the decrease in insulin signaling apparent in DS/obese rats without reducing body weight or visceral adipocyte size. Dietary salt restriction did not alter fasting serum glucose levels but it markedly decreased the fasting serum insulin concentration in DS/obese rats.

Conclusions

Dietary salt restriction not only prevents hypertension and cardiac injury but also ameliorates insulin resistance, without reducing obesity, in this model of metabolic syndrome.

Effects of pioglitazone on cardiac and adipose tissue pathology in rats with metabolic syndrome

BACKGROUND

Pioglitazone is a thiazolidinedione drug that acts as an insulin sensitizer. We recently characterized DahlS.Z-Lepr(fa)/Lepr(fa) (DS/obese) rats, derived from a cross between Dahl salt-sensitive and Zucker rats, as a new animal model of metabolic syndrome. We have now investigated the effects of pioglitazone on cardiac and adipose tissue pathology in this model.

METHODS AND RESULTS

DS/obese rats were treated with pioglitazone (2.5 mg/kg per day, per os) from 9 to 13 weeks of age. Age-matched homozygous lean (DahlS.Z-Lepr(+)/Lepr(+), or DS/lean) littermates served as controls. Pioglitazone increased body weight and food intake in DS/obese rats. It also ameliorated left ventricular (LV) hypertrophy, fibrosis, and diastolic dysfunction as well as attenuated cardiac oxidative stress and inflammation, without lowering blood pressure, in DS/obese rats, but it had no effect on these parameters in DS/lean rats. In addition, pioglitazone increased visceral and subcutaneous fat mass but alleviated adipocyte hypertrophy and inflammation in visceral adipose tissue in DS/obese rats. Furthermore, pioglitazone increased the serum concentration of adiponectin, induced activation of AMP-activated protein kinase (AMPK) in the heart, as well as ameliorated glucose intolerance and insulin resistance in DS/obese rats.

CONCLUSIONS

Treatment of DS/obese rats with pioglitazone exacerbated obesity but attenuated LV hypertrophy, fibrosis, and diastolic dysfunction, with these latter effects being associated with the activation of cardiac AMPK signaling likely as a result of the stimulation of adiponectin secretion.

Association of cardiorespiratory fitness with left ventricular remodeling and diastolic function: the Cooper Center Longitudinal Study

OBJECTIVES

This study sought to compare the cross-sectional associations between fitness and echocardiographic measures of cardiac structure and function.

BACKGROUND

Cardiorespiratory fitness is inversely associated with heart failure risk. However, the mechanism through which fitness lowers heart failure risk is not fully understood.

METHODS

We included 1,678 men and 1,247 women from the Cooper Center Longitudinal Study who received an echocardiogram from 1999 to 2011. Fitness was estimated by Balke protocol (in metabolic equivalents) and also categorized into age-specific quartiles, with quartile 1 representing low fitness. Cross-sectional associations between fitness (in metabolic equivalents) and relative wall thickness, left ventricular end-diastolic diameter indexed to body surface area, left atrial volume indexed to body surface area, left ventricular systolic function, and E/e' ratio were determined using multivariable linear regression analysis.

RESULTS

Higher levels of mid-life fitness (metabolic equivalents) were associated with larger indexed left atrial volume (men: beta = 0.769, p < 0.0001; women: beta = 0.879, p value ≤0.0001) and indexed left ventricular end-diastolic diameter (men: beta = 0.231, p < 0.001; women: beta = 0.264, p < 0.0001). Similarly, a higher level of fitness was associated with a smaller relative wall thickness (men: beta = -0.002, p = 0.04; women: beta = -0.005, p < 0.0001) and E/e' ratio (men: beta = -0.11, p = 0.003; women: beta = -0.13, p = 0.01). However, there was no association between low fitness and left ventricular systolic function (p = NS).

CONCLUSIONS

Low fitness is associated with a higher prevalence of concentric remodeling and diastolic dysfunction, suggesting that exercise may lower heart failure risk through its effect on favorable cardiac remodeling and improved diastolic function.

Angiogenesis and cardiac hypertrophy: maintenance of cardiac function and causative roles in heart failure

Cardiac hypertrophy is an adaptive response to physiological and pathological overload. In response to the overload, individual cardiac myocytes become mechanically stretched and activate intracellular hypertrophic signaling pathways to re-use embryonic transcription factors and to increase the synthesis of various proteins, such as structural and contractile proteins. These hypertrophic responses increase oxygen demand and promote myocardial angiogenesis to dissolve the hypoxic situation and to maintain cardiac contractile function; thus, these responses suggest crosstalk between cardiac myocytes and microvasculature. However, sustained pathological overload induces maladaptation and cardiac remodeling, resulting in heart failure. In recent years, specific understanding has increased with regard to the molecular processes and cell-cell interactions that coordinate myocardial growth and angiogenesis. In this review, we summarize recent advances in understanding the regulatory mechanisms of coordinated myocardial growth and angiogenesis in the pathophysiology of cardiac hypertrophy and heart failure.

Treatment with nebivolol combined with physical training promotes improvements in the cardiovascular responses of hypertensive rats

The aim of this study was to determine whether exercise training combined with beta-blocker treatment promotes additional cardiovascular benefits compared with either intervention on its own. For this we used 76 Wistar rats distributed among different groups: normotensive sedentary (NS), normotensive trained (NT), normotensive sedentary treated with beta-blocker (NS_BB), normotensive trained treated with beta-blocker (NT_BB), hypertensive sedentary (HS), hypertensive trained (HT), hypertensive sedentary treated with a beta-blocker (HS_BB), and hypertensive trained rats treated with beta-blocker (HT_BB). Exercise training consisted of 4 weeks of swimming for 60 min a day, 5 days a week. Hypertension was induced with l-NAME (4 weeks), whereas the control rats received saline, and both the control and test rats received nebivolol. The animals underwent surgery to directly record their blood pressure. The HS group showed higher mean arterial pressure (MAP) (P = 0.000), systolic arterial pressure (P = 0.000), and diastolic arterial pressure (P = 0.000) compared with NS. MAP was higher in the HS compared with the HT (P = 0.002), HS_BB (P = 0.018), and HT_BB (P = 0.015) groups. Hearts from the HS group had a higher percentage of collagen compared with the NS and HS_BB groups. The HT_BB and HT groups only had a higher percentage of cardiac collagen by comparison with the HS_BB group. The HT_BB group showed higher levels of macrophages and neutrophils by comparison with the HT and HS_BB groups. Thus, treatment with a beta-blocker combined with physical training was associated with increased cardiovascular benefits over either intervention alone.

Exercise training in adverse cardiac remodeling

Cardiac remodeling in response to a myocardial infarction or chronic pressure-overload is an independent risk factor for the development of heart failure. In contrast, cardiac remodeling produced by regular physical exercise is associated with a decreased risk for heart failure. There is evidence that exercise training has a beneficial effect on disease progression and survival in patients with cardiac remodeling and dysfunction, but concern has also been expressed that exercise training may aggravate pathological remodeling and dysfunction. Here we present studies from our laboratory into the effects of exercise training on pathological cardiac remodeling and dysfunction in mice. The results indicate that even in the presence of a large infarct, exercise training exerts beneficial effects on the heart. These effects were mimicked in part by endothelial nitric oxide synthase (eNOS) overexpression and abrogated by eNOS deficiency, demonstrating the importance of nitric oxide signaling in mediating the cardiac effects of exercise. Exercise prior to a myocardial infarction was also cardioprotective. In contrast, exercise tended to aggravate pathological cardiac remodeling and dysfunction in the setting of pressure-overload produced by an aortic stenosis. These observations emphasize the critical importance of the underlying pathological stimulus for cardiac hypertrophy and remodeling, in determining the effects of exercise training. Future studies are needed to define the influence of exercise type, intensity and duration in different models and severities of pathological cardiac remodeling. Together such studies will aid in optimizing the therapy of exercise training in the setting of cardiovascular disease.

Effect of genetic polymorphisms of vascular endothelial growth factor on left ventricular hypertrophy in patients with systemic hypertension

Vascular endothelial growth factor (VEGF) is a cytokine involved in angiogenesis and upregulated during adaptive heart hypertrophy. Downregulation of VEGF seems to trigger the transition from adaptive to dilated cardiac hypertrophy. We investigated for the first time whether 3 clinically relevant polymorphisms in the VEGFA gene are associated with altered echocardiographic parameters in hypertensive patients. We determined genotypes for 3 polymorphisms in VEGFA promoter in 179 hypertensive patients and 169 healthy controls: g.-2578C>A (rs699947), g.-1154G>A (rs1570360), and g.-634G>C (rs2010963). Although the variant genotypes of the g.-634G>C (GC + CC) were associated with reduced left ventricular mass index (p = 0.030), the variant genotypes for the g.-1154G>A (GA + AA) were associated with reduced ejection fraction (p = 0.008). In addition, we found that VEGFA haplotypes were associated with altered ejection fraction (p = 0.024). The AAG haplotype was associated with reduced ejection fraction (p = 0.006), whereas the AGG haplotype was associated with increased ejection fraction (p = 0.010). Our results suggest that VEGF polymorphisms affect cardiac remodeling. Genotypes for VEGFA polymorphisms can be useful to help to identify hypertensive patients at greater intrinsic risk for heart failure.

Effects of salt status and blockade of mineralocorticoid receptors on aldosterone-induced cardiac injury

The mineralocorticoid aldosterone regulates sodium and water homeostasis in the human body. The combination of excess aldosterone and salt loading induces hypertension and cardiac damage. However, little is known of the effects of aldosterone on blood pressure and cardiac pathophysiology in the absence of salt loading. We have now investigated the effects of salt status and blockade of mineralocorticoid receptors (MRs) on cardiac pathophysiology in uninephrectomized Sprague-Dawley rats implanted with an osmotic minipump to maintain hyperaldosteronism. The rats were fed a low-salt (0.0466% NaCl in chow) or high-salt (0.36% NaCl in chow plus 1% NaCl in drinking water) diet in the absence or presence of treatment with a subdepressor dose of the MR antagonist spironolactone (SPL). Aldosterone excess in the setting of low salt intake induced substantial cardiac remodeling and diastolic dysfunction without increasing blood pressure. These effects were accompanied by increased levels of oxidative stress and inflammation as well as increased expression of genes related to the renin-angiotensin and endothelin systems in the heart. All of these cardiac changes were completely blocked by the administration of SPL. On the other hand, aldosterone excess in the setting of high salt intake induced hypertension and a greater extent of cardiac injury, with the cardiac changes being only partially attenuated by SPL in a manner independent of its antihypertensive effect. The combination of dietary salt restriction and MR antagonism is thus a promising therapeutic option for the management of hypertensive patients with hyperaldosteronism or relative aldosterone excess.

Calorie restriction attenuates cardiac remodeling and diastolic dysfunction in a rat model of metabolic syndrome

Calorie restriction (CR) can modulate the features of obesity-related metabolic and cardiovascular diseases. We have recently characterized DahlS.Z-Lepr(fa)/Lepr(fa) (DS/obese) rats, derived from a cross between Dahl salt-sensitive and Zucker rats, as a new animal model of metabolic syndrome. DS/obese rats develop hypertension and manifest left ventricular remodeling and diastolic dysfunction, as well as increased cardiac oxidative stress and inflammation. We have now investigated the effects of CR on cardiac pathophysiology in DS/obese rats. DS/obese rats were fed either normal laboratory chow ad libitum or a calorie-restricted diet (65% of the average food intake for ad libitum) from 9 to 13 weeks. Age-matched homozygous lean (DahlS.Z-Lepr(+)/Lepr(+) or DS/lean) littermates served as controls. CR reduced body weight in both DS/obese and DS/lean rats, as well as attenuated the development of hypertension in DS/obese rats without affecting blood pressure in DS/lean rats. CR also reduced body fat content, ameliorated left ventricular hypertrophy, fibrosis, and diastolic dysfunction, and attenuated cardiac oxidative stress and inflammation in DS/obese rats. In addition, it increased serum adiponectin concentration, as well as downregulated the expression of angiotensin-converting enzyme and angiotensin II type 1A receptor genes in the heart of DS/obese rats. Our results thus show that CR attenuated obesity and hypertension, as well as left ventricular remodeling and diastolic dysfunction in DS/obese rats, with these latter effects being associated with reduced cardiac oxidative stress and inflammation.

Impact of exercise training on redox signaling in cardiovascular diseases

Reactive oxygen and nitrogen species regulate a wide array of signaling pathways that governs cardiovascular physiology. However, oxidant stress resulting from disrupted redox signaling has an adverse impact on the pathogenesis and progression of cardiovascular diseases. In this review, we address how redox signaling and oxidant stress affect the pathophysiology of cardiovascular diseases such as ischemia-reperfusion injury, hypertension and heart failure. We also summarize the benefits of exercise training in tackling the hyperactivation of cellular oxidases and mitochondrial dysfunction seen in cardiovascular diseases.

Heart failure with preserved ejection fraction: chronic low-intensity interval exercise training preserves myocardial O2 balance and diastolic function

We have previously reported chronic low-intensity interval exercise training attenuates fibrosis, impaired cardiac mitochondrial function, and coronary vascular dysfunction in miniature swine with left ventricular (LV) hypertrophy (Emter CA, Baines CP. Am J Physiol Heart Circ Physiol 299: H1348-H1356, 2010; Emter CA, et al. Am J Physiol Heart Circ Physiol 301: H1687-H1694, 2011). The purpose of this study was to test two hypotheses: 1) chronic low-intensity interval training preserves normal myocardial oxygen supply/demand balance; and 2) training-dependent attenuation of LV fibrotic remodeling improves diastolic function in aortic-banded sedentary, exercise-trained (HF-TR), and control sedentary male Yucatan miniature swine displaying symptoms of heart failure with preserved ejection fraction. Pressure-volume loops, coronary blood flow, and two-dimensional speckle tracking ultrasound were utilized in vivo under conditions of increasing peripheral mean arterial pressure and β-adrenergic stimulation 6 mo postsurgery to evaluate cardiac function. Normal diastolic function in HF-TR animals was characterized by prevention of increased time constant of isovolumic relaxation, normal LV untwisting rate, and enhanced apical circumferential and radial strain rate. Reduced fibrosis, normal matrix metalloproteinase-2 and tissue inhibitors of metalloproteinase-4 mRNA expression, and increased collagen III isoform mRNA levels (P < 0.05) accompanied improved diastolic function following chronic training. Exercise-dependent improvements in coronary blood flow for a given myocardial oxygen consumption (P < 0.05) and cardiac efficiency (stroke work to myocardial oxygen consumption, P < 0.05) were associated with preserved contractile reserve. LV hypertrophy in HF-TR animals was associated with increased activation of Akt and preservation of activated JNK/SAPK. In conclusion, chronic low-intensity interval exercise training attenuates diastolic impairment by promoting compliant extracellular matrix fibrotic components and preserving extracellular matrix regulatory mechanisms, preserves myocardial oxygen balance, and promotes a physiological molecular hypertrophic signaling phenotype in a large animal model resembling heart failure with preserved ejection fraction.

Effects of estrogen on cardiovascular injury in ovariectomized female DahlS.Z-Lepr(fa)/Lepr(fa) rats as a new animal model of metabolic syndrome

Although recent clinical trials have found an increased incidence of cardiovascular disease in women on estrogen replacement therapy, the underlying mechanism remains unclear. We have recently characterized DahlS.Z-Lepr(fa)/Lepr(fa) (DS/obese) rats, derived from a cross between Dahl salt-sensitive and Zucker rats, as a new animal model of metabolic syndrome. We have now examined the effects of estrogen replacement on cardiac pathophysiology in ovariectomized female DS/obese (Ovx-DS/obese) rats. Animals subjected to ovariectomy at 7 weeks of age were implanted subcutaneously with a 60-day release pellet containing 0.5 mg of 17β-estradiol (E(2)) or placebo at 8 weeks. Age-matched female homozygous lean littermates (DahlS.Z-Lepr(+)/Lepr(+) or DS/lean rats) of DS/obese rats served as controls. Animals were maintained on a normal diet and were subjected to echocardiography followed by various pathological analyses at 13 weeks of age. Ovx-DS/obese rats manifested hypertension at 7 weeks of age and thereafter and showed left ventricular (LV) fibrosis and diastolic dysfunction at 13 weeks. Treatment with E(2) attenuated hypertension in Ovx-DS/obese rats but had no effect on blood pressure in ovariectomized female DS/lean (Ovx-DS/lean) rats. E(2) treatment exacerbated LV fibrosis and diastolic dysfunction, as well as further increased cardiac oxidative stress and inflammation in Ovx-DS/obese rats, and it elicited similar effects in Ovx-DS/lean rats. E(2) reduced food intake, body weight, and visceral fat content in both Ovx-DS/obese and Ovx-DS/lean rats. E(2) treatment attenuated hypertension and obesity but exacerbated LV fibrosis and diastolic dysfunction in Ovx-DS/obese rats, with these latter effects being associated with increased cardiac oxidative stress and inflammation.

Cardiac remodeling and diastolic dysfunction in DahlS.Z-Lepr(fa)/Lepr(fa) rats: a new animal model of metabolic syndrome

We recently characterized male DahlS.Z-Lepr(fa)/Lepr(fa) (Dahl salt-sensitive (DS)/obese) rats, which were established from a cross between Dahl salt-sensitive and Zucker rats, as a new animal model of metabolic syndrome (MetS). We have now investigated cardiac pathophysiology and metabolic changes in female DS/obese rats in comparison with homozygous lean female littermates (DahlS.Z-Lepr(+)/Lepr(+), or DS/lean, rats). Animals were maintained on a normal diet and were subjected to echocardiography followed by various pathological analyses at 15 weeks of age. Systolic blood pressure was significantly higher in female DS/obese rats than in DS/lean females at 12 weeks of age and thereafter. The survival rate of DS/obese rats was significantly lower than that of DS/lean rats at 15 weeks. Body weight, as well as visceral and subcutaneous fat mass were significantly increased in DS/obese rats, which also manifested left ventricular (LV) diastolic dysfunction and marked LV hypertrophy and fibrosis. In addition, myocardial oxidative stress and inflammation were increased in DS/obese rats compared with DS/lean rats. Serum insulin and triglyceride levels as well as the ratio of low-density lipoprotein- to high-density lipoprotein-cholesterol levels were markedly elevated in DS/obese rats, whereas fasting serum glucose concentrations were similar in the two rat strains. The phenotype of female DS/obese rats is similar to that of MetS in humans. These animals also develop salt-sensitive hypertension and LV diastolic dysfunction as well as LV hypertrophy and fibrosis, and these changes are associated with increased cardiac oxidative stress and inflammation.

AKT signalling in the failing heart

AKT is a serine/threonine protein kinase, also known as protein kinase B, which regulates cardiac growth, myocardial angiogenesis, glucose metabolism, and cell death in cardiac myocytes. AKT is activated by its phosphorylation at Thr 308 and ser 473 by PDK1 and mTORC2, respectively, in response to trophic stimuli such as insulin and insulin growth factor. c-Jun N-Terminal Kinases (JNKs) phosphorylate AKT at Thr 450 and potentiate its interaction with its downstream effectors. The short-term activation of AKT promotes physiological hypertrophy and protection from myocardial injury; whereas, its long-term activation causes pathological hypertrophy and heart failure. In this review we will discuss the role of AKT in regulating signalling pathways in the heart with special emphasis on the role of AKT in modulating stress induced autophagic cell death in cardiomyocytes in vitro.

Merits of non-invasive rat models of left ventricular heart failure

Heart failure (HF) is characterized as a limitation to cardiac output that prevents the heart from supplying tissues with adequate oxygen and predisposes individuals to pulmonary edema. Impaired cardiac function is secondary to either decreased contractility reducing ejection (systolic failure), diminished ventricular compliance preventing filling (diastolic failure), or both. To study HF etiology, many different techniques have been developed to elicit this condition in experimental animals, with varying degrees of success. Among rats, surgically induced HF models are the most prevalent, but they bear several shortcomings, including high mortality rates and limited recapitulation of the pathophysiology, etiology, and progression of human HF. Alternatively, a number of non-invasive HF induction methods avoid many of these pitfalls, and their merits in technical simplicity, reliability, survivability, and comparability to the pathophysiologic and pathogenic characteristics of HF are reviewed herein. In particular, this review focuses on the primary pathogenic mechanisms common to genetic strains (spontaneously hypertensive and spontaneously hypertensive heart failure), pharmacological models of toxic cardiomyopathy (doxorubicin and isoproterenol), and dietary salt models, all of which have been shown to induce left ventricular HF in the rat. Additional non-invasive techniques that may potentially enable the development of new HF models are also discussed.

Taurine prevents hypertension and increases exercise capacity in rats with fructose-induced hypertension

BACKGROUND

Fructose-induced hypertension was used to test the hypothesis that taurine supplementation and/or exercise can prevent hypertension and increase exercise capacity.

METHODS

Five groups of 15 Sprague-Dawley rats were allocated and designated as control, high fructose-fed (fructose), high fructose-fed plus exercise (FE), high fructose-fed plus 2% taurine supplement (FT) and high fructose-fed plus 2% taurine supplement and exercise (FET) groups. Noninvasive systolic blood pressure (SBP) was recorded weekly and invasive arterial blood pressure (ABP) was recorded at the end of the 4-week trial. Three consecutive swimming tests were performed in the selected rats from each group and the plasma biomarkers were measured in the remaining rats.

RESULTS

Noninvasive SBP differed significantly (P < 0.001) from week 3, both noninvasive and invasive ABP increased significantly (P < 0.001), and exercise capacity significantly decreased (P < 0.001) in the fructose group compared with the control group. The individual effects of swimming and taurine supplementation were incapable of preventing the development of hypertension and SBP significantly (P < 0.001) increased in the FE and FT groups; exercise capacity in those groups remained similar to control. The combined effects of exercise and taurine alleviated hypertension and significantly increased exercise capacity in the FET group. Insulin resistance increased significantly and plasma nitric oxide (NO) decreased significantly in the F, FE, and FT groups. Both parameters remained similar to control values in the FET group with an increasing antioxidant activity.

CONCLUSION

Taurine supplementation in combination with exercise prevents hypertension and increases exercise capacity by possibly antioxidation and maintaining NO concentrations.