Exercise training in Tgαq*44 mice during the progression of chronic heart failure: cardiac vs. peripheral (soleus muscle) impairments to oxidative metabolism

Chronic heart failure induces early defenestration of liver sinusoidal endothelial cells (LSECs) in mice

AIM

Chronic heart failure (CHF) is often linked to liver malfunction and systemic endothelial dysfunction. However, whether cardio-hepatic interactions in heart failure involve dysfunction of liver sinusoidal endothelial cells (LSECs) is not known. Here we characterize LSECs phenotype in early and end stages of chronic heart failure in a murine model.

METHODS

Right ventricle (RV) function, features of congestive hepatopathy, and the phenotype of primary LSECs were characterized in Tgαq*44 mice, with cardiomyocyte-specific overexpression of the Gαq protein, at the age of 4- and 12-month representative for early and end-stage phases of CHF, respectively.

RESULTS

4- and 12-month-old Tgαq*44 mice displayed progressive impairment of RV function and alterations in hepatic blood flow velocity resulting in hepatic congestion with elevated GGT and bilirubin plasma levels and decreased albumin concentration without gross liver pathology. LSECs isolated from 4- and 12-month-old Tgαq*44 mice displayed significant loss of fenestrae with impaired functional response to cytochalasin B, significant changes in proteome related to cytoskeleton remodeling, and altered vasoprotective function. However, LSECs barrier function and bioenergetics were largely preserved. In 4- and 12-month-old Tgαq*44 mice, LSECs defenestration was associated with prolonged postprandial hypertriglyceridemia and in 12-month-old Tgαq*44 mice with proteomic changes of hepatocytes indicative of altered lipid metabolism.

CONCLUSION

Tgαq*44 mice displayed right-sided HF and altered hepatic blood flow leading to LSECs dysfunction involving defenestration, shift in eicosanoid profile, and proteomic changes. LSECs dysfunction appears as an early and persistent event in CHF, preceding congestive hepatopathy and contributing to alterations in lipoprotein transport and CHF pathophysiology.

The Association of Metabolomic Profiles of a Healthy Lifestyle with Heart Failure Risk in a Prospective Study

Lifestyle has been linked to the incidence of heart failure, but the underlying biological mechanisms remain unclear. Using the metabolomic, lifestyle, and heart failure data of the UK Biobank, we identified and validated healthy lifestyle-related metabolites in a matched case-control and cohort study, respectively. We then evaluated the association of healthy lifestyle-related metabolites with heart failure (HF) risk and the added predictivity of these healthy lifestyle-associated metabolites for HF. Of 161 metabolites, 8 were identified to be significantly related to healthy lifestyle. Notably, omega-3 fatty acids and docosahexaenoic acid (DHA) positively associated with a healthy lifestyle score (HLS) and exhibited a negative association with heart failure risk. Conversely, creatinine negatively associated with a HLS, but was positively correlated with the risk of HF. Adding these three metabolites to the classical risk factor prediction model, the prediction accuracy of heart failure incidence can be improved as assessed by the C-statistic (increasing from 0.806 [95% CI, 0.796-0.816] to 0.844 [95% CI, 0.834-0.854], p-value < 0.001). A healthy lifestyle is associated with significant metabolic alterations, among which metabolites related to healthy lifestyle may be critical for the relationship between healthy lifestyle and HF. Healthy lifestyle-related metabolites might enhance HF prediction, but additional validation studies are necessary.

Accelerated ageing and coronary microvascular dysfunction in chronic heart failure in Tgαq*44 mice

Age represents a major risk factor in heart failure (HF). However, the mechanisms linking ageing and HF are not clear. We aimed to identify the functional, morphological and transcriptomic changes that could be attributed to cardiac ageing in a model of slowly progressing HF in Tgαq*44 mice in reference to the cardiac ageing process in FVB mice. In FVB mice, ageing resulted in the impairment of diastolic cardiac function and in basal coronary flow (CF), perivascular and interstitial fibrosis without changes in the cardiac activity of angiotensin-converting enzyme (ACE) or aldosterone plasma concentration. In Tgαq*44 mice, HF progression was featured by the impairment of systolic and diastolic cardiac function and in basal CF that was associated with a distinct rearrangement of the capillary architecture, pronounced perivascular and interstitial fibrosis, progressive activation of cardiac ACE and systemic angiotensin-aldosterone-dependent pathways. Interestingly, cardiac ageing genes and processes were represented in Tgαq*44 mice not only in late but also in early phases of HF, as evidenced by cardiac transcriptome analysis. Thirty-four genes and 8 biological processes, identified as being ageing related, occurred early and persisted along HF progression in Tgαq*44 mice and were mostly associated with extracellular matrix remodelling and fibrosis compatible with perivascular fibrosis resulting in coronary microvascular dysfunction (CMD) in Tgαq*44 mice. In conclusion, accelerated and persistent cardiac ageing contributes to the pathophysiology of chronic HF in Tgαq*44 mice. In particular, prominent perivascular fibrosis of microcirculation resulting in CMD represents an accelerated cardiac ageing phenotype that requires targeted treatment in chronic HF.

Physical Activity and Inhibition of ACE Additively Modulate ACE/ACE-2 Balance in Heart Failure in Mice

Angiotensin-converting enzyme inhibition (ACE-I) and physical activity favorably modulate the ACE/ACE-2 balance. However, it is not clear whether physical activity and ACE-I could synergistically modulate ACE/ACE-2 balance in the course of heart failure (HF). Here, we studied the effects of combined spontaneous physical activity and ACE-I–based treatment on angiotensin (Ang) pattern and cardiac function in a mouse model of HF (Tgαq*44). Tgαq*44 mice with advanced HF (at the age of 12 months) were running spontaneously in a running wheel (exercise training group, ExT) and/or were treated with ACE inhibitor (ACE-I, perindopril, 10 mg/kg) for 2 months. Angiotensin profile was characterized by an LC-MS/MS-based method. The cardiac performance was assessed in vivo by MRI. Ang-(1–7)/Ang II ratio in both plasma and the aorta was significantly higher in the combined treatment group than the ACE-I group or ExT alone, suggesting the additive favorable effects on ACE-2/Ang-(1–7) and ACE/Ang II axes’ balance induced by a combination of ACE-I with ExT. The basal cardiac performance did not differ among the experimental groups of Tgαq*44 mice. We demonstrated additive changes in ACE/ACE-2 balance in both plasma and the aorta by spontaneous physical activity and ACE-I treatment in Tgαq*44 mice. However, these changes did not result in an improvement of failing heart function most likely because the disease was at the end-stage. Ang-(1–7)/Ang II balance represents a valuable biochemical end point for monitoring therapeutic intervention outcome in heart failure.

Current Studies and Future Directions of Exercise Therapy for Muscle Atrophy Induced by Heart Failure

Muscle atrophy is a common complication of heart failure. At present, there is no specific treatment to reverse the course of muscle atrophy. Exercise training, due to the safety and easy operation, is a recommended therapy for muscle atrophy induced by heart failure. However, the patients with muscle atrophy are weak in mobility and may not be able to train for a long time. Therefore, it is necessary to explore novel targets of exercise protection for muscle atrophy, so as to improve the quality of life and survival rate of patients with muscular atrophy induced by heart failure. This article aims to review latest studies, summarize the evidence and limitations, and provide a glimpse into the future of exercise for the treatment of muscle atrophy induced by heart failure. We wish to highlight some important findings about the essential roles of exercise sensors in muscle atrophy induced by heart failure, which might be helpful for searching potential therapeutic targets for muscle wasting induced by heart failure.

Voluntary physical activity counteracts Chronic Heart Failure progression affecting both cardiac function and skeletal muscle in the transgenic Tgαq*44 mouse model

Physical activity is emerging as an alternative nonpharmaceutical strategy to prevent and treat a variety of cardiovascular diseases due to its cardiac and skeletal muscle beneficial effects. Oxidative stress occurs in skeletal muscle of chronic heart failure (CHF) patients with possible impact on muscle function decline. We determined the effect of voluntary‐free wheel running (VFWR) in preventing protein damage in Tgαq*44 transgenic mice (Tg) characterized by a delayed CHF progression. In the early (6 months) and transition (12 months) phase of CHF, VFWR increased the daily mean distance covered by Tg mice eliminating the difference between Tg and WT present before exercise at 12 months of age (WT Pre‐EX 3.62 ± 1.66 vs. Tg Pre‐EX 1.51 ± 1.09 km, P < 0.005; WT Post‐EX 5.72 ± 3.42 vs. Tg Post‐EX 4.17 ± 1.8 km, P > 0.005). This effect was concomitant with an improvement of in vivo cardiac performance [(Cardiac Index (mL/min/cm²): 6 months, untrained‐Tg 0.167 ± 0.005 vs. trained‐Tg 0.21 ± 0.003, P < 0.005; 12 months, untrained‐Tg 0.1 ± 0.009 vs. trained‐Tg 0.133 ± 0.005, P < 0.005]. Such effects were associated with a skeletal muscle antioxidant response effective in preventing oxidative damage induced by CHF at the transition phase (untrained‐Tg 0.438 ± 0.25 vs. trained‐Tg 0.114 ± 0.010, P < 0.05) and with an increased expression of protein control markers (MuRF‐1, untrained‐Tg 1.12 ± 0.29 vs. trained‐Tg 14.14 ± 3.04, P < 0.0001; Atrogin‐1, untrained‐Tg 0.9 ± 0.38 vs. trained‐Tg 7.79 ± 2.03, P < 0.01; Cathepsin L, untrained‐Tg 0.91 ± 0.27 vs. trained‐Tg 2.14 ± 0.55, P < 0.01). At the end‐stage of CHF (14 months), trained‐Tg mice showed a worsening of physical performance (decrease in daily activity and weekly distance and time of activity) compared to trained age‐matched WT in association with oxidative protein damage of a similar level to that of untrained‐Tg mice (untrained‐Tg 0.62 ± 0.24 vs. trained‐Tg 0.64 ± 0.13, P > 0.05). Prolonged voluntary physical activity performed before the onset of CHF end‐stage, appears to be a useful tool to increase cardiac function and to reduce skeletal muscle oxidative damage counteracting physical activity decline.

Impact of long-lasting spontaneous physical activity on bone morphogenetic protein 4 in the heart and tibia in murine model of heart failure

Bone morphogenetic protein 4 (BMP4) plays an important role in bone remodeling and in heart failure pathogenesis. The aim of this study was to evaluate the effect of spontaneous physical activity on the expression of BMP4 in the heart and tibia of the transgenic (Tgαq*44) mice, representing a model of chronic heart failure. Tgαq*44 and wild-type FVB mice (WT) were randomly assigned either to sedentary or to trained groups undergoing 8 weeks of spontaneous wheel running. The BMP4 protein expression in heart and tibiae was evaluated using Western immunoblotting and the phosphorus and calcium in the tibiae was assessed using the X-ray microanalysis. BMP4 content in the hearts of the Tgαq*44-sedentary mice was by ~490% higher than in the WT-sedentary mice, whereas in tibiae the BMP4 content of the Tgαq*44-sedentary mice was similar to that in the WT-sedentary animals. Tgαq*44 mice revealed by ~28% poorer spontaneous physical activity than the WT mice. No effect of performed physical activity on the BMP4 content in the hearts of either in the Tgαq*44 or WT mice was observed. However, 8-week spontaneous wheel running resulted in a decrease in the BMP4 expression in tibiae (by ~43%) in the group of Tgαq*44 mice only, with no changes in their bone phosphorus and calcium contents. We have concluded that prolonged period of spontaneous physical exercise does not increase the risk of the progression of the BMP4-mediated pathological cardiac hypertrophy and does not affect bone mineral status in the chronic heart failure mice.

An α2-adrenoceptor agonist: Dexmedetomidine induces protective cardiomyocyte hypertrophy through mitochondrial-AMPK pathway

Aims: Dexmedetomidine (Dex) as a highly selective α₂-adrenoceptor agonist, was widely used anesthetic in perioperative settings, whether Dex induces cardiac hypertrophy during perioperative administration is unknown. Methods: The effects of Dex on cardiac hypertrophy were explored using the transverse aortic constriction model and neonatal rat cardiomyocytes. Results: We reported that Dex induces cardiomyocyte hypertrophy with activated ERK, AKT, PKC and inactivated AMPK in both wild-type mice and primary cultured rat cardiomyocytes. Additionally, pre-administration of Dex protects against transverse aortic constriction induced-heart failure in mice. We found that Dex up-regulates the activation of ERK, AKT, and PKC via suppression of AMPK activation in rat cardiomyocytes. However, suppression of mitochondrial coupling efficiency and membrane potential by FCCP blocks Dex induced AMPK inactivation as well as ERK, AKT, and PKC activation. All of these effects are blocked by the α₂-adrenoceptor antagonist atipamezole. Conclusion: The present study demonstrates Dex preconditioning induces cardiac hypertrophy that protects against heart failure through mitochondria-AMPK pathway in perioperative settings.

A systematic comparison of exercise training protocols on animal models of cardiovascular capacity

Cardiovascular disease (CVD) is a major global cause of mortality, which has prompted numerous studies seeking to reduce the risk of heart failure and sudden cardiac death. While regular physical activity is known to improve CVD associated morbidity and mortality, the optimal duration, frequency, and intensity of exercise remains unclear. To address this uncertainty, various animal models have been used to study the cardioprotective effects of exercise and related molecular mechanism such as the mice training models significantly decrease size of myocardial infarct by affecting Kir6.1, VSMC sarc-K_ATP channels, and pulmonary eNOS. Although these findings cement the importance of animal models in studying exercise induced cardioprotection, the vast assortment of exercise protocols makes comparison across studies difficult. To address this issue, we review and break down the existent exercise models into categories based on exercise modality, intensity, frequency, and duration. The timing of sample collection is also compared and sorted into four distinct phases: pre-exercise (Phase I), mid-exercise (Phase II), exercise recovery (Phase III), and post-exercise (Phase IV). Finally, because the life-span of animals so are limited, small changes in animal exercise duration can corresponded to untenable amounts of human exercise. To address this limitation, we introduce the Life-Span Relative Exercise Time (RET_{life span}) as a method of accurately defining short-term, medium-term and long-term exercise relative to the animal's life expectancy. Systematic organization of existent protocols and this new system of defining exercise duration will allow for a more solid framework from which researchers can extrapolate animal model data to clinical application.

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.

Immuno-Spin Trapping-Based Detection of Oxidative Modifications in Cardiomyocytes and Coronary Endothelium in the Progression of Heart Failure in Tgαq*44 Mice

Recent studies suggest both beneficial and detrimental role of increased reactive oxygen species and oxidative stress in heart failure (HF). However, it is not clear at which stage oxidative stress and oxidative modifications occur in the endothelium in relation to cardiomyocytes in non-ischemic HF. Furthermore, most methods used to date to study oxidative stress are either non-specific or require tissue homogenization. In this study, we used immuno-spin trapping (IST) technique with fluorescent microscopy-based detection of DMPO nitrone adducts to localize and quantify oxidative modifications of the hearts from Tgαq*44 mice; a murine model of HF driven by cardiomyocyte-specific overexpression of Gαq* protein. Tgαq*44 mice and age-matched FVB controls at early, transition, and late stages of HF progression were injected with DMPO in vivo and analyzed ex vivo for DMPO nitrone adducts signals. Progressive oxidative modifications in cardiomyocytes, as evidenced by the elevation of DMPO nitrone adducts, were detected in hearts from 10- to 16-month-old, but not in 8-month-old Tgαq*44 mice, as compared with age-matched FVB mice. The DMPO nitrone adducts were detected in left and right ventricle, septum, and papillary muscle. Surprisingly, significant elevation of DMPO nitrone adducts was also present in the coronary endothelium both in large arteries and in microcirculation simultaneously, as in cardiomyocytes, starting from 10-month-old Tgαq*44 mice. On the other hand, superoxide production in heart homogenates was elevated already in 6-month-old Tgαq*44 mice and progressively increased to high levels in 14-month-old Tgαq*44 mice, while the enzymatic activity of catalase, glutathione reductase, and glutathione peroxidase was all elevated as early as in 4-month-old Tgαq*44 mice and stayed at a similar level in 14-month-old Tgαq*44. In summary, this study demonstrates that IST represents a unique method that allows to quantify oxidative modifications in cardiomyocytes and coronary endothelium in the heart. In Tgαq*44 mice with slowly developing HF, driven by cardiomyocyte-specific overexpression of Gαq* protein, an increase in superoxide production, despite compensatory activation of antioxidative mechanisms, results in the development of oxidative modifications not only in cardiomyocytes but also in coronary endothelium, at the transition phase of HF, before the end-stage disease.

Vascular Cognitive Impairment Linked to Brain Endothelium Inflammation in Early Stages of Heart Failure in Mice

BACKGROUND

Although advanced heart failure (HF) is a clinically documented risk factor for vascular cognitive impairment, the occurrence and pathomechanisms of vascular cognitive impairment in early stages of HF are equivocal. Here, we characterize vascular cognitive impairment in the early stages of HF development and assess whether cerebral hypoperfusion or prothrombotic conditions are involved.

METHODS AND RESULTS

Tgαq*44 mice with slowly developing isolated HF triggered by cardiomyocyte-specific overexpression of G-αq*44 protein were studied before the end-stage HF, at the ages of 3, 6, and 10 months: before left ventricle dysfunction; at the stage of early left ventricle diastolic dysfunction (with preserved ejection fraction); and left ventricle diastolic/systolic dysfunction, respectively. In 6- to 10-month-old but not in 3-month-old Tgαq*44 mice, behavioral and cognitive impairment was identified with compromised blood-brain barrier permeability, most significantly in brain cortex, that was associated with myelin sheet loss and changes in astrocytes and microglia. Brain endothelial cells displayed increased E-selectin immunoreactivity, which was accompanied by increased amyloid-β1-42 accumulation in piriform cortex and increased cortical oxidative stress (8-OHdG immunoreactivity). Resting cerebral blood flow measured by magnetic resonance imaging in vivo was preserved, but ex vivo NO-dependent cortical arteriole flow regulation was impaired. Platelet hyperreactivity was present in 3- to 10-month-old Tgαq*44 mice, but it was not associated with increased platelet-dependent thrombogenicity.

CONCLUSIONS

We report for the first time that vascular cognitive impairment is already present in the early stage of HF development, even before left ventricle systolic dysfunction. The underlying pathomechanism, independent of brain hypoperfusion, involves preceding platelet hyperreactivity and brain endothelium inflammatory activation.