Beneficial effects on skeletal muscle of the angiotensin II type 1 receptor blocker irbesartan in experimental heart failure

Histological changes in skeletal muscle induced by heart failure in human patients and animal models: A scoping review

OBJECTIVE

This scoping review aimed to characterize the histological changes in skeletal muscle after heart failure (HF) and to identify gaps in knowledge.

METHODS

On April 03, 2024, systematic searches were performed for papers in which histological analyses were conducted on skeletal muscle sampled from patients with HF or animal models of HF. Screening and data extraction were conducted by two independent authors.

RESULTS AND CONCLUSION

A total of 118 papers were selected, including 33 human and 85 animal studies. Despite some disagreements among studies, some trends were observed. These trends included a slow-to-fast transition, a decrease in muscle fiber size, capillary to muscle fiber ratio, and mitochondrial activity and content, and an increase in apoptosis. These changes may contribute to the fatigability and decrease in muscle strength observed after HF. Although there were some disagreements between the results of human and animal studies, the results were generally similar. Animal models of HF will therefore be useful in elucidating the histological changes in skeletal muscle that occur in human patients with HF. Because the muscles subjected to histological analysis were mostly thigh muscles in humans and mostly lower leg muscles in animals, it remains uncertain whether changes similar to those seen in lower limb (hindlimb) muscles after HF also occur in upper limb (forelimb) muscles. The results of this review will consolidate the current knowledge on HF-induced histological changes in skeletal muscle and consequently aid in the rehabilitation of patients with HF and future studies.

Angiotensin II type 1a receptor deficiency alleviates muscle atrophy after denervation

The study aim was to determine if suppressed activation of angiotensin II type 1 receptor (AT1) prevents severe muscle atrophy after denervation. The sciatic nerves in right and left inferior limbs were cut in AT1a knockout homo (AT1a^-/-) male mice and wild-type (AT1a^+/+) male mice. Muscle weight and cross-sectional areas of type IIb muscle fibers in gastrocnemius muscle decreased at 7 and 21 days postdenervation in both AT1a^-/- mice and AT1a^+/+ mice, and the reduction was significantly attenuated in the denervated muscles of AT1a^-/- mice compared to the AT1a^+/+ mice. Gene expressions in the protein degradation system [two E3 ubiquitin ligases (muscle RING-finger protein-1 and Atrogin-1)] upregulated at 7 days postdenervation in all denervated mice were significantly lower in AT1a^-/- mice than in AT1a^+/+ mice. Activations of nuclear factor κB and Forkhead box subgroup O1, and protein expression of monocyte chemoattractant protein-1 were significantly suppressed in the AT1a^-/- mice compared with those in the AT1a^+/+ mice. In addition, suppressed apoptosis, lower infiltration of M1 macrophages, and higher infiltration of M2 macrophages were significantly observed at 21 days postdenervation in the AT1a^-/- mice compared with those in the AT1a^+/+ mice. In conclusion, the AT1 receptor deficiency retarded muscle atrophy after denervation.

Angiotensin II Promotes Skeletal Muscle Angiogenesis Induced by Volume-Dependent Aerobic Exercise Training: Effects on miRNAs-27a/b and Oxidant-Antioxidant Balance

Aerobic exercise training (ET) produces beneficial adaptations in skeletal muscles, including angiogenesis. The renin-angiotensin system (RAS) is highly involved in angiogenesis stimuli. However, the molecular mechanisms underlying capillary growth in skeletal muscle induced by aerobic ET are not completely understood. This study aimed to investigate the effects of volume-dependent aerobic ET on skeletal muscle angiogenesis involving the expression of miRNAs-27a and 27b on RAS and oxidant-antioxidant balance. Eight-week-old female Wistar rats were divided into three groups: sedentary control (SC), trained protocol 1 (P1), and trained protocol 2 (P2). P1 consisted of 60 min/day of swimming, 5×/week, for 10 weeks. P2 consisted of the same protocol as P1 until the 8th week, but in the 9th week, rats trained 2×/day, and in the 10th week, trained 3×/day. Angiogenesis and molecular analyses were performed in soleus muscle samples. Furthermore, to establish ET-induced angiogenesis through RAS, animals were treated with an AT1 receptor blocker (losartan). Aerobic ET promoted higher VO2 peak and exercise tolerance values. In contrast, miRNA-27a and -27b levels were reduced in both trained groups, compared with the SC group. This was in parallel with an increase in the ACE1/Ang II/VEGF axis, which led to a higher capillary-to-fiber ratio. Moreover, aerobic ET induced an antioxidant profile increasing skeletal muscle SOD2 and catalase gene expression, which was accompanied by high nitrite levels and reduced nitrotyrosine concentrations in the circulation. Additionally, losartan treatment partially re-established the miRNAs expression and the capillary-to-fiber ratio in the trained groups. In summary, aerobic ET promoted angiogenesis through the miRNA-27a/b-ACE1/Ang II/VEGF axis and improved the redox balance. Losartan treatment demonstrates the participation of RAS in ET-induced vascular growth. miRNAs and RAS components are promising potential targets to modulate angiogenesis for combating vascular diseases, as well as potential biomarkers to monitor training interventions and physical performance.

Distinct determinants of muscle wasting in nonobese heart failure patients with and without type 2 diabetes mellitus

BACKGROUND

Muscle wasting, that is, reduction in muscle mass, is frequently observed in patients with chronic heart failure (CHF) and diabetes mellitus (DM).

METHODS

We retrospectively examined 185 patients with CHF (median age of 71 years [interquartile range, 61-78 years]; 64% male) who received a dual-energy X-ray absorptiometry scan for assessment of appendicular skeletal muscle mass index (ASMI).

RESULTS

Seventy patients with CHF (38%) had DM. Patients with DM had higher prevalences of ischemic heart disease and hypertension, lower levels of estimated glomerular filtration rate (eGFR) and ASMI, and higher levels of plasma renin activity (PRA) than did patients without DM. In simple regression analyses, ASMI was positively correlated with the Mini Nutritional Assessment Short Form (MNA-SF) score and levels of hemoglobin, eGFR, and fasting plasma insulin and was negatively correlated with levels of N-terminal pro B-type natriuretic peptide, PRA, and cortisol. In multiple linear regression analyses, age, MNA-SF score, DM, fasting plasma insulin level, and PRA were independently associated with ASMI. When multiple linear regression analyses were separately performed in a non-DM group and a DM group, MNA-SF score and fasting plasma insulin level were independent variables for ASMI in both groups. PRA was independently associated with ASMI in the DM group but not in the non-DM group, whereas cortisol concentration was independently associated with ASMI only in the non-DM group.

CONCLUSIONS

In addition to malnutrition and reduction in plasma insulin, renin-angiotensin system activation may be responsible for the development of muscle wasting in CHF patients with DM.

Cardiac Cachexia: A Well-Known but Challenging Complication of Heart Failure

Heart failure (HF) is a common complication of various cardiac diseases, and its incidence constantly increases. This is caused mainly by aging of populations and improvement in the treatment of coronary artery disease. As HF patients age, they tend to develop comorbidities, creating new problems for health-care professionals. Sarcopenia, defined as the loss of muscle mass and function, and cachexia, defined as weight loss due to an underlying illness, are muscle wasting disorders of particular relevance in the heart failure population, but they go mostly unrecognized. The coexistence of chronic HF and metabolic disorders facilitates the development of cachexia. Cachexia, in turn, significantly worsens a patient’s prognosis and quality of life. The mechanisms underlying cachexia have not been explained yet and require further research. Understanding its background is crucial in the development of treatment strategies to prevent and treat tissue wasting. There are currently no specific European guidelines or recommended therapy for cachexia treatment in HF (“cardiac cachexia”).

Data on the stem cells paracrine effects on apoptosis and cytokine milieu in an experimental model of cardiorenal syndrome type II

The data reported in this article are related to the paper entitle “Stem cells transplantation positively modulates the heart-kidney cross talk in Cardiorenal Syndrome Type II” (Vescovo et al., 2019), which analyzed the impact of stem cells injection in cardiorenal syndrome type II. The dataset contains detailed information on apoptosis and cytokines milieu modification after injection of c-Kit–selected human amniotic fluid stem cells (hAFS) or rats vascular progenitor cells (rSVC-GFP group) in an experimental model of CRSII. The data can be useful for clarifying the paracrine effects exerted by the injected cells.

The Renin-Angiotensin System and Skeletal Muscle

The renin-angiotensin system (RAS) plays a key role in the control of blood pressure and fluid homeostasis. Emerging evidence also reveals that hyperactivity of the RAS contributes to skeletal muscle wasting. This review discusses the key role that the RAS plays in skeletal muscle wasting due to congestive heart failure, chronic kidney disease, and ventilator-induced diaphragmatic wasting.

Stem cells transplantation positively modulates the heart-kidney cross talk in cardiorenal syndrome type II

INTRODUCTION

We investigated the effects of human amniotic fluid stem cells (hAFS) and rat adipose tissue stromal vascular fraction GFP-positive cells (rSVC-GFP) in a model of cardio-renal syndrome type II (CRSII).

METHODS AND RESULTS

RHF was induced by monocrotaline (MCT) in 28 Sprague-Dawley rats. Three weeks later, four million hAFS or rSVC-GFP cells were injected via tail vein. BNP, sCreatinine, kidney and heart NGAL and MMP9, sCytokines, kidney and heart apoptosis and cells (Cs) engraftment were evaluated. Cell-treated rats showed a significant reduction of serum NGAL and Creatinine compared to CRSII. In both hAFS and rSVC-GFP group, kidney protein expression of NGAL was significantly lower than in CRSII (hAFS p = 0.036 and rSVC-GFP p < 0.0001) and similar to that of controls. In both hAFS and rSVC-GFP treated rats, we observed cell engraftment in the medulla and differentiation into tubular, endothelial and SMCs cells. Apoptosis was significantly decreased in cell-treated rats (hAFS 14.07 ± 1.38 and rSVC-GFP 12.67 ± 2.96 cells/mm²) and similar to controls (9.85 ± 2.1 cell/mm²). TUNEL-positive cells were mainly located in the kidney medulla. Pro-inflammatory cytokines were down regulated in cell-treated groups and similar to controls. In cell-treated rats, kidney and heart tissue NGAL was not complexed with MMP9 as in CRSII group, suggesting inhibition of MMPs activity.

CONCLUSION

Cell therapy produced improvement in kidney function in rats with CRSII. This was the result of interstitial, vessel and tubular cell engraftment leading to tubular and vessel regeneration, decreased tubular cells apoptosis and mitigated pro-inflammatory milieu. Reduction of NGLA-MMP9 complexes mainly due to decrease MMPs activity prevented further negative heart remodeling.

Renin-Angiotensin System Inhibitors to Mitigate Cancer Treatment-Related Adverse Events

Treatment-related side effects are a major clinical problem in cancer treatment. They lead to reduced compliance to therapy as well as increased morbidity and mortality. Well-known are the sequelae of chemotherapy on the heart, especially in childhood cancer survivors. Therefore, measures to mitigate the adverse events of cancer therapy may improve health and quality of life in patients with cancer, both in the short and long term. The renin-angiotensin system (RAS) affects all hallmarks of cancer, and blockage of the RAS is associated with an improved outcome in several cancer types. There is also increasing evidence that inhibition of the RAS might be able to alleviate or even prevent certain types of cancer treatment-related adverse effects. In this review, we summarize the potential of RAS inhibitors to mitigate cancer treatment-related adverse events, with a special emphasis on chemotherapy-induced cardiotoxicity, radiation injury, and arterial hypertension. Clin Cancer Res; 24(16); 3803-12. ©2018 AACR.

The ACE2/Angiotensin-(1-7)/MAS Axis of the Renin-Angiotensin System: Focus on Angiotensin-(1-7)

The renin-angiotensin system (RAS) is a key player in the control of the cardiovascular system and hydroelectrolyte balance, with an influence on organs and functions throughout the body. The classical view of this system saw it as a sequence of many enzymatic steps that culminate in the production of a single biologically active metabolite, the octapeptide angiotensin (ANG) II, by the angiotensin converting enzyme (ACE). The past two decades have revealed new functions for some of the intermediate products, beyond their roles as substrates along the classical route. They may be processed in alternative ways by enzymes such as the ACE homolog ACE2. One effect is to establish a second axis through ACE2/ANG-(1-7)/MAS, whose end point is the metabolite ANG-(1-7). ACE2 and other enzymes can form ANG-(1-7) directly or indirectly from either the decapeptide ANG I or from ANG II. In many cases, this second axis appears to counteract or modulate the effects of the classical axis. ANG-(1-7) itself acts on the receptor MAS to influence a range of mechanisms in the heart, kidney, brain, and other tissues. This review highlights the current knowledge about the roles of ANG-(1-7) in physiology and disease, with particular emphasis on the brain.

Angiotensin-II-induced Muscle Wasting is Mediated by 25-Hydroxycholesterol via GSK3β Signaling Pathway

While angiotensin II (ang II) has been implicated in the pathogenesis of cardiac cachexia (CC), the molecules that mediate ang II's wasting effect have not been identified. It is known TNF-α level is increased in patients with CC, and TNF-α release is triggered by ang II. We therefore hypothesized that ang II induced muscle wasting is mediated by TNF-α. Ang II infusion led to skeletal muscle wasting in wild type (WT) but not in TNF alpha type 1 receptor knockout (TNFR1KO) mice, suggesting that ang II induced muscle loss is mediated by TNF-α through its type 1 receptor. Microarray analysis identified cholesterol 25-hydroxylase (Ch25h) as the down stream target of TNF-α. Intraperitoneal injection of 25-hydroxycholesterol (25-OHC), the product of Ch25h, resulted in muscle loss in C57BL/6 mice, accompanied by increased expression of atrogin-1, MuRF1 and suppression of IGF-1/Akt signaling pathway. The identification of 25-OHC as an inducer of muscle wasting has implications for the development of specific treatment strategies in preventing muscle loss.

•

Ang II induced muscle wasting is mediated by TNF-α, which in turn up regulates Ch25h

•

Knockout of TNFR1 inhibits the production of 25-OHC and blocks ang II induced muscle loss in mice

•

25-OHC injection induces muscle wasting in mice by activating GSK3β

•

A GSK3β inhibitor blocks ang II induced muscle atrophy, which paves the way for targeted therapy to treat muscle wasting

Cardiac cachexia (CC), a condition characterized by weight loss and muscle wasting, is a serious complication that occurs in patients with chronic heart failure. This condition impairs patient's daily physical activity and their quality of life. Specific therapy for CC is currently unavailable because the pathogenesis remains unknown. Previous studies have identified angiotensin II (ang II) as an important mediator of CC. We now report a previously unrecognized role of 25-hydroxycholesterol (25-OHC) in mediating ang II induced muscle loss. The identification of 25-OHC as a muscle wasting inducer has implications for the development of therapeutic intervention in preserving muscle mass.

Time course of ubiquitin-proteasome and macroautophagy-lysosome pathways in skeletal muscle in rats with heart failure

Patients with heart failure have limited exercise capacity due to not only the myocardial dysfunction but also skeletal muscle atrophy. However, the mechanisms and time course of protein degradation in skeletal muscle during heart failure remain unclear, and there is no established standard treatment. The purpose of the present study was to investigate the time course of major protein degradation pathways in skeletal muscle during heart failure. Four-week-old male Wistar rats were randomly assigned to heart failure induced by monocrotaline or control groups. At 14 and 21 days after monocrotaline injection, the lungs, heart, and gastrocnemius and soleus muscles were removed and analyzed. There was no significant difference in body weight between the groups at 14 days after monocrotaline injection. Although there were no morphological changes in the skeletal muscle of the monocrotaline group at this time point, ubiquitin-proteasome and macroautophagylysosome pathways were activated in the monocrotaline group. Additionally, the pathways were less strongly activated in the soleus muscle than in the gastrocnemius muscle. These results suggest that physical exercise that shifts to slow muscle characteristics should begin when there is no indication of skeletal muscle atrophy to prevent exercise intolerance with heart failure.

Aliskiren targets multiple systems to alleviate cancer cachexia

To examine the effects of aliskiren, a small-molecule renin inhibitor, on cancer cachexia and to explore the underlying mechanisms. A cancer cachexia model was established by subcutaneously injecting C26 mouse colon carcinoma cells into isogenic BALB/c mice. Aliskiren was administered intragastrically [10 mg/kg body weight (BW)] on day 5 (as a preventive strategy, AP group) or on day 12 (as a therapeutic strategy, AT group) after C26 injection. Mice that received no C26 injection (healthy controls, HC group) or only C26 injection but not aliskiren (cancer, CA group) were used as controls. BW, tumor growth, whole body functions, and survival were monitored daily in half of the mice in each group, whereas serum, tumors, and gastrocnemius muscles were harvested from the other mice after sacrifice on day 20 for further analysis. Aliskiren significantly alleviated multiple cachexia‑associated symptoms, including BW loss, tumor burden, muscle wasting, muscular dysfunction, and shortened survival. On the molecular level, aliskiren antagonized cachexia‑induced activation of the renin‑angiotensin system (RAS), systematic and muscular inflammation, oxidative stress, and autophagy‑lysosome as well as ubiquitin‑proteasome stimulation. In addition, early administration of aliskiren before cachexia development (AP group) resulted in more robust effects in alleviating cachexia or targeting underlying mechanisms than administration after cachexia development (AT group). Aliskiren exhibited potent anti‑cachexia activities. These activities were achieved through the targeting of at least four mechanisms underlying cachexia development: RAS activation, increase in systematic inflammation, upregulation of oxidative stress, and stimulation of autophagy-lysosome pathway (ALP) and ubiquitin-proteasome pathway (UPP).

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Drug target identification using network analysis: Taking active components in Sini decoction as an example

Identifying the molecular targets for the beneficial effects of active small-molecule compounds simultaneously is an important and currently unmet challenge. In this study, we firstly proposed network analysis by integrating data from network pharmacology and metabolomics to identify targets of active components in sini decoction (SND) simultaneously against heart failure. To begin with, 48 potential active components in SND against heart failure were predicted by serum pharmacochemistry, text mining and similarity match. Then, we employed network pharmacology including text mining and molecular docking to identify the potential targets of these components. The key enriched processes, pathways and related diseases of these target proteins were analyzed by STRING database. At last, network analysis was conducted to identify most possible targets of components in SND. Among the 25 targets predicted by network analysis, tumor necrosis factor α (TNF-α) was firstly experimentally validated in molecular and cellular level. Results indicated that hypaconitine, mesaconitine, higenamine and quercetin in SND can directly bind to TNF-α, reduce the TNF-α-mediated cytotoxicity on L929 cells and exert anti-myocardial cell apoptosis effects. We envisage that network analysis will also be useful in target identification of a bioactive compound.

Aerobic Exercise and Pharmacological Therapies for Skeletal Myopathy in Heart Failure: Similarities and Differences

Skeletal myopathy has been identified as a major comorbidity of heart failure (HF) affecting up to 20% of ambulatory patients leading to shortness of breath, early fatigue, and exercise intolerance. Neurohumoral blockade, through the inhibition of renin angiotensin aldosterone system (RAS) and β-adrenergic receptor blockade (β-blockers), is a mandatory pharmacological therapy of HF since it reduces symptoms, mortality, and sudden death. However, the effect of these drugs on skeletal myopathy needs to be clarified, since exercise intolerance remains in HF patients optimized with β-blockers and inhibitors of RAS. Aerobic exercise training (AET) is efficient in counteracting skeletal myopathy and in improving functional capacity and quality of life. Indeed, AET has beneficial effects on failing heart itself despite being of less magnitude compared with neurohumoral blockade. In this way, AET should be implemented in the care standards, together with pharmacological therapies. Since both neurohumoral inhibition and AET have a direct and/or indirect impact on skeletal muscle, this review aims to provide an overview of the isolated effects of these therapeutic approaches in counteracting skeletal myopathy in HF. The similarities and dissimilarities of neurohumoral inhibition and AET therapies are also discussed to identify potential advantageous effects of these combined therapies for treating HF.

The Role of Congestion in Cardiorenal Syndrome Type 2: New Pathophysiological Insights into an Experimental Model of Heart Failure

BACKGROUND

In cardiorenal syndrome type 2 (CRS2), the role of systemic congestion in heart failure (HF) is still obscure. We studied a model of CRS2 [monocrotaline (MCT)-treated rats] secondary to pulmonary hypertension and right ventricular (RV) failure in order to evaluate the contribution of prevalent congestion to the development of kidney injury.

METHODS

Ten animals were treated with MCT for 4 weeks until they developed HF. Eleven animals were taken as controls. Signs of hypertrophy and dilatation of the right ventricle demonstrated the occurrence of HF. Brain natriuretic peptide (BNP), serum creatinine (sCreatinine), both kidney and heart neutrophil gelatinase-associated lipocalin (NGAL), matrix metallopeptidase 9 (MMP9), serum cytokines as well as kidney and heart cell death, as assessed by TUNEL, were studied.

RESULTS

Rats with HF showed higher BNP levels [chronic HF (CHF) 4.8 ± 0.5 ng/ml; controls 1.5 ± 0.2 ng/ml; p < 0.0001], marked RV hypertrophy and dilatation (RV mass/RV volume: CHF 1.46 ± 0.31, controls 2.41 ± 0.81; p < 0.01) as well as pleural and peritoneal effusions. A significant increase in proinflammatory cytokines and sCreatinine was observed (CHF 3.06 ± 1.3 pg/ml vs. controls 0.54 ± 0.23 pg/ml; p = 0.04). Serum (CHF 562.7 ± 93.34 ng/ml vs. controls 245.3 ± 58.19 ng/ml; p = 0.02) as well as renal and heart tissue NGAL levels [CHF 70,680 ± 4,337 arbitrary units (AU) vs. controls 32,120 ± 4,961 AU; p = 0.001] rose significantly, and they were found to be complexed with MMP9 in CHF rats. A higher number of kidney TUNEL-positive tubular cells was also detected (CHF 114.01 ± 45.93 vs. controls 16.36 ± 11.60 cells/mm(2); p = 0.0004).

CONCLUSION

In this model of CHF with prevalent congestion, kidney injury is characterized by tubular damage and systemic inflammation. The upregulated NGAL complexed with MMP9 perpetuates the vicious circle of kidney/heart damage by enhancing the enzymatic activity of MMP9 with extracellular matrix degradation, worsening heart remodeling.

Pharmacological perspectives in sarcopenia: a potential role for renin-angiotensin system blockers?

Sarcopenia represents a major health problem highly prevalent in elderly and age-related chronic diseases. Current pharmacological strategies available to prevent and reverse sarcopenia are largely unsatisfactory thus raising the need to identify novel targets for pharmacological intervention and possibly more effective and safe drugs. This review highlights the current knowledge of the potential benefits of renin-angiotensin system blockade in sarcopenia and discuss the main mechanisms underlying the effects.

Angiotensin type 2 receptor signaling in satellite cells potentiates skeletal muscle regeneration

Patients with advanced congestive heart failure (CHF) or chronic kidney disease (CKD) often have increased angiotensin II (Ang II) levels and cachexia. Ang II infusion in rodents causes sustained skeletal muscle wasting and decreases muscle regenerative potential through Ang II type 1 receptor (AT1R)-mediated signaling, likely contributing to the development of cachexia in CHF and CKD. However, the potential role of Ang II type 2 receptor (AT2R) signaling in skeletal muscle physiology is unknown. We found that AT2R expression was increased robustly in regenerating skeletal muscle after cardiotoxin (CTX)-induced muscle injury in vivo and differentiating myoblasts in vitro, suggesting that the increase in AT2R played an important role in regulating myoblast differentiation and muscle regeneration. To determine the potential role of AT2R in muscle regeneration, we infused C57BL/6 mice with the AT2R antagonist PD123319 during CTX-induced muscle regeneration. PD123319 reduced the size of regenerating myofibers and expression of the myoblast differentiation markers myogenin and embryonic myosin heavy chain. On the other hand, AT2R agonist CGP42112 infusion potentiated CTX injury-induced myogenin and embryonic myosin heavy chain expression and increased the size of regenerating myofibers. In cultured myoblasts, AT2R knockdown by siRNA suppressed myoblast differentiation marker expression and myoblast differentiation via up-regulation of phospho-ERK1/2, and ERK inhibitor treatment completely blocked the effect of AT2R knockdown. These data indicate that AT2R signaling positively regulates myoblast differentiation and potentiates skeletal muscle regenerative potential, providing a new therapeutic target in wasting disorders such as CHF and CKD.

Effects of exercise training on circulating and skeletal muscle renin-angiotensin system in chronic heart failure rats

BACKGROUND

Accumulated evidence shows that the ACE-AngII-AT1 axis of the renin-angiotensin system (RAS) is markedly activated in chronic heart failure (CHF). Recent studies provide information that Angiotensin (Ang)-(1-7), a metabolite of AngII, counteracts the effects of AngII. However, this balance between AngII and Ang-(1-7) is still little understood in CHF. We investigated the effects of exercise training on circulating and skeletal muscle RAS in the ischemic model of CHF.

METHODS/MAIN RESULTS

Male Wistar rats underwent left coronary artery ligation or a Sham operation. They were divided into four groups: 1) Sedentary Sham (Sham-S), 2) exercise-trained Sham (Sham-Ex), sedentary CHF (CHF-S), and exercise-trained CHF (CHF-Ex). Angiotensin concentrations and ACE and ACE2 activity in the circulation and skeletal muscle (soleus and plantaris) were quantified. Skeletal muscle ACE and ACE2 protein expression, and AT1, AT2, and Mas receptor gene expression were also evaluated. CHF reduced ACE2 serum activity. Exercise training restored ACE2 and reduced ACE activity in CHF. Exercise training reduced plasma AngII concentration in both Sham and CHF rats and increased the Ang-(1-7)/AngII ratio in CHF rats. CHF and exercise training did not change skeletal muscle ACE and ACE2 activity and protein expression. CHF increased AngII levels in both soleus and plantaris muscle, and exercise training normalized them. Exercise training increased Ang-(1-7) in the plantaris muscle of CHF rats. The AT1 receptor was only increased in the soleus muscle of CHF rats, and exercise training normalized it. Exercise training increased the expression of the Mas receptor in the soleus muscle of both exercise-trained groups, and normalized it in plantaris muscle.

CONCLUSIONS

Exercise training causes a shift in RAS towards the Ang-(1-7)-Mas axis in skeletal muscle, which can be influenced by skeletal muscle metabolic characteristics. The changes in RAS circulation do not necessarily reflect the changes occurring in the RAS of skeletal muscle.

Diaphragm dysfunction in heart failure is accompanied by increases in neutral sphingomyelinase activity and ceramide content

AIMS

Chronic heart failure (CHF) causes inspiratory (diaphragm) muscle weakness and fatigue that contributes to dyspnoea and limited physical capacity in patients. However, the mechanisms that lead to diaphragm dysfunction in CHF remain poorly understood. Cytokines and angiotensin II are elevated in CHF and stimulate the activity of the enzyme sphingomyelinase (SMase) and accumulation of its reaction product ceramide. In the diaphragm, SMase or ceramide exposure in vitro causes weakness and fatigue. Thus, elevated SMase activity and ceramide content have been proposed as mediators of diaphragm dysfunction in CHF. In the present study, we tested the hypotheses that diaphragm dysfunction was accompanied by increases in diaphragm SMase activity and ceramide content.

METHODS AND RESULTS

Myocardial infarction was used to induce CHF in rats. We measured diaphragm isometric force, SMase activity by high-performance liquid chromatography, and ceramide subspecies and total ceramide using mass spectrometry. Diaphragm force was depressed and fatigue accelerated by CHF. Diaphragm neutral SMase activity was increased by 20% in CHF, while acid SMase activity was unchanged. We also found that CHF increased the content of C18 -, C20 -, and C24 -ceramide subspecies and total ceramide. Downstream of ceramide degradation, diaphragm sphingosine was unchanged, and sphingosine-1-phosphate level was increased in CHF.

CONCLUSION

Our major novel finding was that diaphragm dysfunction in CHF rats was accompanied by higher diaphragm neutral SMase activity, which is expected to cause the observed increase in diaphragm ceramide content.

Molecular mechanisms and signaling pathways of angiotensin II-induced muscle wasting: potential therapeutic targets for cardiac cachexia

Cachexia is a serious complication of many chronic diseases, such as congestive heart failure (CHF) and chronic kidney disease (CKD). Many factors are involved in the development of cachexia, and there is increasing evidence that angiotensin II (Ang II), the main effector molecule of the renin-angiotensin system (RAS), plays an important role in this process. Patients with advanced CHF or CKD often have increased Ang II levels and cachexia, and angiotensin-converting enzyme (ACE) inhibitor treatment improves weight loss. In rodent models, an increase in systemic Ang II leads to weight loss through increased protein breakdown, reduced protein synthesis in skeletal muscle and decreased appetite. Ang II activates the ubiquitin-proteasome system via generation of reactive oxygen species and via inhibition of the insulin-like growth factor-1 signaling pathway. Furthermore, Ang II inhibits 5' AMP-activated protein kinase (AMPK) activity and disrupts normal energy balance. Ang II also increases cytokines and circulating hormones such as tumor necrosis factor-α, interleukin-6, serum amyloid-A, glucocorticoids and myostatin, which regulate muscle protein synthesis and degradation. Ang II acts on hypothalamic neurons to regulate orexigenic/anorexigenic neuropeptides, such as neuropeptide-Y, orexin and corticotropin-releasing hormone, leading to reduced appetite. Also, Ang II may regulate skeletal muscle regenerative processes. Several clinical studies have indicated that blockade of Ang II signaling via ACE inhibitors or Ang II type 1 receptor blockers prevents weight loss and improves muscle strength. Thus the RAS is a promising target for the treatment of muscle atrophy in patients with CHF and CKD. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.

The contribution of stem cell therapy to skeletal muscle remodeling in heart failure

BACKGROUND

The aim of our study was to investigate whether stem cell (SC) therapy with human amniotic fluid stem cells (hAFS, fetal stem cells) and rat adipose tissue stromal vascular fraction cells-GFP positive cells (rSVC-GFP) was able to produce favorable effects on skeletal muscle (SM) remodeling in a well-established rat model of right heart failure (RHF).

METHODS

RHF was induced by monocrotaline (MCT) in Sprague-Dawley rats. Three weeks later, four millions of hAFS or rSVC-GFP cells were injected via tail vein. SM remodeling was assessed by Soleus muscle fiber cross sectional area (CSA), myocyte apoptosis, myosin heavy chain (MHC) composition, satellite cells pattern, and SC immunohistochemistry.

RESULTS

hAFS and rSVC-GFP injection produced significant SC homing in Soleus (0.68 ± 1.0 and 0.67 ± 0.75% respectively), with a 50% differentiation toward smooth muscle and endothelial cells. Pro-inflammatory cytokines were down regulated to levels similar to those of controls. SC-treated (SCT) rats showed increased CSA (p<0.004 vs MCT) similarly to controls with a reshift toward the slow MHC1 isoform. Apoptosis was significantly decreased (11.12.± 8.8 cells/mm(3) hAFS and 13.1+7.6 rSVC-GFP) (p<0.001 vs MCT) and similar to controls (5.38 ± 3.0 cells/mm(3)). RHF rats showed a dramatic reduction of satellite cells(MCT 0.2 ± 0.06% Pax7 native vs controls 2.60 ± 2.46%, p<0.001), while SCT induced a repopulation of both native and SC derived satellite cells (p<0.005).

CONCLUSIONS

SC treatment led to SM remodeling with satellite cell repopulation, decreased atrophy and apoptosis. Modulation of the cytokine milieu might play a crucial pathophysiological role with a possible scenario for autologous transplantation of SC in pts with CHF myopathy.

Mitochondria-derived superoxide links to tourniquet-induced apoptosis in mouse skeletal muscle

Our previous study has reported that superoxide mediates ischemia-reperfusion (IR)-induced necrosis in mouse skeletal muscle. However, it remains poorly understood whether IR induces apoptosis and what factors are involved in IR-induced apoptosis in skeletal muscle. Using a murine model of tourniquet-induced hindlimb IR, we investigated the relationship between mitochondrial dysfunction and apoptosis in skeletal muscle. Hindlimbs of C57/BL6 mice were subjected to 3 h ischemia and 4 h reperfusion via placement and release of a rubber tourniquet at the greater trochanter. Compared to sham treatment, tourniquet-induced IR significantly elevated mitochondria-derived superoxide production, activated opening of mitochondrial permeability transition pore (mPTP), and caused apoptosis in the gastrocnemius muscles. Pretreatment with a superoxide dismutase mimetic (tempol, 50 mg/kg) or a mitochondrial antioxidant (co-enzyme Q₁₀, 50 mg/kg) not only decreased mitochondria-derived superoxide production, but also inhibited mPTP opening and apoptosis in the IR gastrocnemius muscles. Additionally, an inhibitor of mPTP (cyclosporine A, 50 mg/kg) also inhibited both mPTP opening and apoptosis in the IR gastrocnemius muscles. These results suggest that mitochondria-derived superoxide overproduction triggers the mPTP opening and subsequently causes apoptosis in tourniquet-induced hindlimb IR.

Stem-cell therapy in an experimental model of pulmonary hypertension and right heart failure: role of paracrine and neurohormonal milieu in the remodeling process

BACKGROUND

In this study we investigated the effect of human amniotic fluid stem (hAFS) cells and rat adipose tissue stromal vascular fraction GFP-positive cell (rSVC-GFP) therapy and the contribution of the paracrine and neurohormonal milieu to cardiac and pulmonary vascular remodeling in a rat model of pulmonary hypertension (PH) and right heart failure (RHF).

METHODS

Sprague-Dawley rats were injected with monocrotaline (MCT). Four million hAFS or rSVC-GFP cells were injected via the tail vein 3 weeks after MCT. RHF was confirmed by RV hypertrophy/dilation and by brain natriuretic peptide (BNP) level. Cytokine profile was assessed by Multiplex array. Stem cell (SC) differentiation was studied by immunofluorescence.

RESULTS

MCT rats showed eccentric RV hypertrophy with increased RV dilation (measured as right ventricular mass/right ventricular volume [RVM/RVV]: MCT, 1.46 ± 0.12; control, 2.33 ± 0.24; p = 0.01), and increased RV hypertrophy (measured as LVM/RVM: MCT, 1.58 ± 0.06; control, 2.83 ± 0.1; p < 0.00001), increased BNP (MCT, 5.2 ± 1.2; control, 1.5 ± 0.1; p < 0.001) and both pro- and anti-inflammatory cytokines. SC produced a fall of BNP (hAFS, 2.1 ± 0.7; rSVC-GFP, 1.98 ± 1.3; p < 0.001) and pro-inflammatory cytokines. Positive RV remodeling with decreased RV dilation (RVM/RVV: hAFS, 1.87 ± 0.44; rSVC-GFP, 2.12 ± 0.24; p < 0.03 and p < 0.05 vs MCT) and regression of RV hypertrophy (LVM/RVM: hAFS, 2.06 ± 0.08; rSVC-GFP, 2.16 ± 0.08; p < 0.00001 vs MCT) was seen together with a decrease in medial wall thickness of pulmonary arterioles (hAFS, 35.33 ± 2.78%; rSVC-GFP, 37.15 ± 2.92%; p = 0.0001 vs MCT).

CONCLUSIONS

SC engrafted in the lung, heart and skeletal muscle modulated the pro- and anti-inflammatory cytokine milieu, and produced a positive neurohormonal response. This was accompanied by positive cardiac and pulmonary vascular remodeling, with formation mainly of new vascular cells.

Treatment with a corticotrophin releasing factor 2 receptor agonist modulates skeletal muscle mass and force production in aged and chronically ill animals

Background

Muscle weakness is associated with a variety of chronic disorders such as emphysema (EMP) and congestive heart failure (CHF) as well as aging. Therapies to treat muscle weakness associated with chronic disease or aging are lacking. Corticotrophin releasing factor 2 receptor (CRF2R) agonists have been shown to maintain skeletal muscle mass and force production in a variety of acute conditions that lead to skeletal muscle wasting.

Hypothesis

We hypothesize that treating animals with a CRF2R agonist will maintain skeletal muscle mass and force production in animals with chronic disease and in aged animals.

Methods

We utilized animal models of aging, CHF and EMP to evaluate the potential of CRF2R agonist treatment to maintain skeletal muscle mass and force production in aged animals and animals with CHF and EMP.

Results

In aged rats, we demonstrate that treatment with a CRF2R agonist for up to 3 months results in greater extensor digitorum longus (EDL) force production, EDL mass, soleus mass and soleus force production compared to age matched untreated animals. In the hamster EMP model, we demonstrate that treatment with a CRF2R agonist for up to 5 months results in greater EDL force production in EMP hamsters when compared to vehicle treated EMP hamsters and greater EDL mass and force in normal hamsters when compared to vehicle treated normal hamsters. In the rat CHF model, we demonstrate that treatment with a CRF2R agonist for up to 3 months results in greater EDL and soleus muscle mass and force production in CHF rats and normal rats when compared to the corresponding vehicle treated animals.

Conclusions

These data demonstrate that the underlying physiological conditions associated with chronic diseases such as CHF and emphysema in addition to aging do not reduce the potential of CRF2R agonists to maintain skeletal muscle mass and force production.

Bone and muscle loss after spinal cord injury: organ interactions

Spinal cord injury (SCI) results in paralysis and marked loss of skeletal muscle and bone below the level of injury. Modest muscle activity prevents atrophy, whereas much larger--and as yet poorly defined--bone loading seems necessary to prevent bone loss. Once established, bone loss may be irreversible. SCI is associated with reductions in growth hormone, IGF-1, and testosterone, deficiencies likely to exacerbate further loss of muscle and bone. Reduced muscle mass and inactivity are assumed to be contributors to the high prevalence of insulin resistance and diabetes in this population. Alterations in muscle gene expression after SCI share common features with other muscle loss states, but even so, show distinct profiles, possibly reflecting influences of neuromuscular activity due to spasticity. Changes in bone cells and markers after SCI have similarities with other conditions of unloading, although after SCI these changes are much more dramatic, perhaps reflecting the much greater magnitude of unloading. Adiposity and marrow fat are increased after SCI with intriguing, though poorly understood, implications for the function of skeletal muscle and bone cells.

Treatment of hypertension in metabolic syndrome subjects with amlodipine and olmesartan-effects on oxidized non-esterified free fatty acids and cytokine production

PURPOSE

Angiotensin II increases activation of oxidative signaling and vascular inflammatory gene expression, and interruption of the renin-angiotensin system has been considered more vasculoprotective than use of calcium channel antagonists and other anti-hypertensive therapies. Despite these putative mechanisms, amlodipine is equally efficacious as other therapies in reducing cardiovascular events.

METHODS

Double-blind, controlled trial, designed to investigate the effects of 2-months treatment with amlodipine and olmesartan on oxidized non-esterified fatty acids (ox-NEFA), and lipopolysaccharide-stimulated cytokine production in whole blood among 23 hypertensive subjects with the metabolic syndrome.

RESULTS

Treatment with olmesartan was no different than amlodipine in changing concentrations of total oxidized fatty acids (p = 0.37), total ox-NEFA (p = 0.43) and 9, 10, 11, 12, 13, 14, 15 and 16 ox-NEFA concentrations. In contrast, 8 ox-NEFA increased (median [interquartile ranges] by 45.2% [5.3 to 50.0] in olmesartan-treated subjects) compared with a decrease of 18.4% (-45.1-13.9) in amlodipine-treated subjects (p = 0.03). Lipopolysaccharide-stimulated cytokine production and levels of soluble cellular adhesion molecules did not change with either treatment.

CONCLUSION

Despite experimental data that demonstrates that angiotensin receptor antagonists reduce cellular oxidant stress and inflammation, olmesartan was not different than amlodipine in changing ox-NEFA and inflammatory markers in hypertensive subjects with the metabolic syndrome.

Reduced angiotensin II levels in the cerebrospinal fluid of patients with amyotrophic lateral sclerosis

BACKGROUND

Recent studies suggest that angiotensin II, a major substrate in the renin-angiotensin system, protects neurons through stimulation of its type 2 receptors. However, quite a few clinical studies of angiotensin II levels have shown their relation to disease severity in neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS).

AIMS OF THE STUDY

To clarify the significance of angiotensin II in ALS.

METHODS

We assayed angiotensin II concentrations in cerebrospinal fluid (CSF) samples from 23 patients with ALS, nine patients with spinocerebellar degeneration (SCD) and 24 control individuals. We evaluated the disability levels of patients with ALS using the Revised ALS Functional Rating Scale (ALSFRS-R) and calculated the disease progression rate (DPR).

RESULTS

CSF angiotensin II levels were significantly lower in the ALS group compared with that in the control group (P = 0.00864), and showed a significant positive correlation with scores on the ALSFRS-R, and a significant negative correlation with the DPR.

CONCLUSIONS

In the present study, we reveal for the first time that angiotensin II levels in the CSF from patients with ALS are significantly reduced and significantly associated with disease severity and progression rate. These findings suggest that reduced levels of intrathecal angiotensin II may play a role in ALS.

Effects of Astragaloside IV on heart failure in rats

Background

Astragaloside IV (ASI) in Radix Astragali is believed to be the active component in treating heart failure. The present study aims to examine the effects of ASI on cardiovascular parameters in long-term heart failure in rats.

Methods

Using echocardiographic and haemodynamic measurements, we studied the effects of ASI on congestive heart failure (CHF) induced by ligation of the left coronary artery in rats.

Results

ASI (0.1, 0.3 and 1.0 mg/kg/day) attenuated the decline of fractional shortening (FS). The peak derivatives of the left ventricle (LV) pressure (dp/dt) in ASI-treated groups significantly increased. Both LV internal diameters in diastole (LVIDd) and in systole (LVIDs) decreased significantly after ASI treatment (0.3 and 1.0 mg/kg/day). ASI (1.0 mg/kg/day) attenuated the decrease of LV systolic pressure (LVSP). ASI treatment inhibited compensatory hypertrophy of myocardial cells and lowered the number of apoptotic myocytes.

Conclusion

ASI improved cardiac functions as measured by cardiovascular parameters.

Anti-TNF treatment reduces rat skeletal muscle wasting in monocrotaline-induced cardiac cachexia

The aim was to explore efficacy of tumor necrosis factor (TNF) inhibitors in attenuating increases in anorexia and ubiquitin proteasome pathway transcripts in cardiac cachexia, a potentially lethal condition that responds poorly to current treatments. Cardiac cachexia was rapidly induced with monocrotaline in Sprague-Dawley rats. Either soluble TNF receptor-1 or the general inhibitor of TNF production, pentoxifylline, was given to diminish TNF action on the first indication of cachexia. Animals were anesthetized with a ketamine-xylazine-acepromazine cocktail, and then skeletal muscles were removed for subsequent measurements including ubiquitin proteasome pathway transcripts and Western blots. Both soluble TNF receptor-1 and pentoxifylline attenuated losses in both body and skeletal muscle masses and also reduced increases in selected ubiquitin proteasome pathway transcripts. The action of soluble TNF receptor-1 was partly through reversal of reduced food consumption, while the effects of pentoxifylline were independent of food intake. Here we demonstrate, for the first time, that attenuation of anorexia by soluble TNF receptor-1 treatment in monocrotaline-induced cardiac cachexia is responsible for attenuating increases in some ubiquitin proteasome pathway transcripts as well as preserving body mass and attenuating loss of skeletal muscle mass.

Down-regulation of MyoD gene expression in rat diaphragm muscle with heart failure

Diaphragm myopathy has been described in patients with heart failure (HF), with alterations in myosin heavy chains (MHC) expression. The pathways that regulate MHC expression during HF have not been described, and myogenic regulatory factors (MRFs) may be involved. The purpose of this investigation was to determine MRF mRNA expression levels in the diaphragm. Diaphragm muscle from both HF and control Wistar rats was studied when overt HF had developed, 22 days after monocrotaline administration. MyoD, myogenin and MRF4 gene expression were determined by RT-PCR and MHC isoforms by polyacrylamide gel electrophoresis. Heart failure animals presented decreased MHC IIa/IIx protein isoform and MyoD gene expression, without altering MHC I, IIb, myogenin and MRF4. Our results show that in HF, MyoD is selectively down-regulated, which might be associated with alterations in MHC IIa/IIx content. These changes are likely to contribute to the diaphragm myopathy caused by HF.

Reduction of angiotensin II in the cerebrospinal fluid of patients with multiple sclerosis

We previously demonstrated that angiotensin II acts as a crucial neuroprotective factor after neural injury through angiotensin II type-2 (AT2) receptor signaling. Although the pathway is known to play an important role in the development of experimental autoimmune encephalomyelitis, cerebrospinal fluid (CSF) angiotensin II levels in patients with multiple sclerosis (MS) have never been studied. To clarify the significance of angiotensin II in MS, we assayed angiotensin II concentrations using an established enzyme-linked immunoabsorbent assay in CSF samples from patients with MS ( n = 21), patients with inflammatory neuropathies (IN) ( n = 23) and control individuals who did not have either of the neurological diseases or any other disease that might affect the angiotensin II levels in the CSF (control) ( n = 24). Angiotensin II levels in the CSF were 3.79 ± 1.54 pg/ml in the MS group, 5.13 ± 2.27 pg/ml in the IN group and 6.71 ± 2.65 pg/ml in the control group. The angiotensin II levels in the CSF of the MS group were significantly lower than in the control group ( p = 0.00057). Angiotensin II concentration in the CSF tended to have a negative correlation with the Kurtzke’s Expanded Disability Status Scale scores during MS relapse ( p = 0.0847). These findings suggest that reduced levels of intrathecal angiotensin II may be related to the abnormal neural damage and repair processes in MS.

Skeletal muscle wastage in Crohn's disease: a pathway shared with heart failure?

BACKGROUND

Lean body mass wastage in active Crohn's disease is not only related to malnutrition, but also to local and systemic inflammation. Altered bowel permeability can represent a source of pro-inflammatory cytokines, that have been shown to produce muscle wastage by several mechanisms such as apoptosis. In our study we have evaluated the body composition and the pathological changes of skeletal muscle in patients with Crohn's disease to see whether a relationships between altered gut permeability, proinflammatory cytokines production and muscle wastage existed.

METHODS

Thirteen consecutive steroid-free patients with active Crohn's disease underwent evaluation of body composition, sugar test for intestinal permeability, determination of serum levels of TNF-alpha, sphingosine, bacterial lipopolysaccaride, and biopsy of gastrocnemius. In bioptic samples we determined fibres cross sectional area, distribution of myosin heavy chains and apoptosis. Twenty healthy subjects formed the control group.

RESULTS

In patients lean body mass was reduced and intestinal permeability increased (p<0.01 for both). TNFalpha, sphingosine and lipopolysaccaride were increased (p<0.01). Fibres size was reduced (p<0.01), with shift of Myosin Heavy Chains from the slow to the fast type. Apoptosis was found in 5 patients' biopsies, never in controls.

CONCLUSIONS

Crohn's patients have a myopathy characterized by myocyte apoptosis, modifications of myosin and muscle atrophy. TNF-alpha and sphingosine, that are increased because of the enhanced lipopolysaccaride concentration due to altered gut permeability, may play a pathophysiological role in the development of this myopathy.

Expression of interferon-gamma and interleukin-4 production in CD4+ T cells in patients with chronic heart failure

The prevalence of inflammation is high among patients with chronic heart failure (CHF). Reduced ejection fraction was associated with frequency of CD4(+) T cells of leukocytes. Therefore, we investigated inflammatory cytokines of expression markers in CD4(+) T cells in patients with CHF. Blood samples were obtained from 103 patients with CHF, from 83 patients with stable angina (SA), and from 57 controls. Interferon-gamma (IFN-gamma)-positive CD4(+) T cells and interleukin-4 (IL-4)-positive CD4(+) T cells were analyzed using 3-color flow cytometry. The frequency (%) of IFN-gamma-positive CD4(+) T cells increased in patients with CHF compared with those with SA and controls (CHF: 28.3 +/- 13.8, SA: 23.50 +/- 10.38, controls: 19.00 +/- 7.45, P < 0.001). There was no significant difference in the frequency of IL-4-positive CD4(+) T cells among the three groups. The frequencies of CD4(+) T cells that stained for IFN-gamma decreased from 32.37% +/- 16.40% on admission to 26.91% +/- 12.53% after 2 weeks in 26 patients with CHF. B-type natriuretic peptide (pg/ml) and high-sensitivity C-reactive protein (mg/dl) levels decreased from 251.7 +/- 150.4 and 0.64 +/- 0.78 on admission to 208.2 +/- 166.4 and 0.36 +/- 0.34 after 2 weeks in the 26 patients with CHF. We have demonstrated expression of IFN-gamma production of CD4(+) T cells during CHF. Prevention of unwanted T cell activation could represent a new target in the treatment of CHF.

Oxidative phenotype protects myofibers from pathological insults induced by chronic heart failure in mice

The fiber specificity of skeletal muscle abnormalities in chronic heart failure (CHF) has not been defined. We show here that transgenic mice (8 weeks old) with cardiac-specific overexpression of calsequestrin developed CHF (50.9% decrease in fractional shortening and 56.4% increase in lung weight, P<0.001), cachexia (37.8% decrease in body weight, P<0.001), and exercise intolerance (69.3% decrease in running distance to exhaustion, P<0.001) without a significant change in muscle fiber-type composition. Slow oxidative soleus muscle maintained muscle mass, whereas fast glycolytic tibialis anterior and plantaris muscles underwent atrophy (11.6 and 13.3%, respectively; P<0.05). In plantaris muscle, glycolytic type IId/x and IIb, but not oxidative type I and IIa, fibers displayed significant decreases in cross-sectional area (20.3%, P<0.05). Fast glycolytic white vastus lateralis muscle showed sarcomere degeneration and decreased cytochrome c oxidase IV (39.5%, P<0.01) and peroxisome proliferator-activated receptor gamma co-activator 1alpha protein expression (30.3%, P<0.01) along with a dramatic induction of the MAFbx/Atrogin-1 mRNA. These findings suggest that exercise intolerance can occur in CHF without fiber type switching in skeletal muscle and that oxidative phenotype renders myofibers resistant to pathological insults induced by CHF.

Skeletal muscle apoptosis in experimental heart failure: the only link between inflammation and skeletal muscle wastage?

PURPOSE OF REVIEW

The purpose of this review is to enlighten the mechanisms of muscle wastage in experimental heart failure with attention to skeletal muscle apoptosis and the role of proinflammatory cytokines that trigger apoptosis.

RECENT FINDINGS

Mechanisms leading to muscle wastage in chronic heart failure include cytokine-triggered skeletal muscle apoptosis, but also ubiquitin/proteasome and non-ubiquitin-dependent pathways. The regulation of fibre type involves the growth hormone/insulin-like growth factor 1/calcineurin/transcriptional coactivator PGC1 cascade.

SUMMARY

Several mechanisms can lead to muscle wastage in heart failure. The imbalance between protein synthesis and degradation plays an important role. Protein degradation can occur through ubiquitin-dependent and non-ubiquitin-dependent pathways. Systems controlling ubiquitin/proteasome activation have been described. These are triggered by tumour necrosis factor alpha and growth hormone/insulin-like growth factor 1. However, an important role is played by apoptosis. In humans and experimental models of heart failure programmed cell death has been found in skeletal muscle and interstitial cells. Apoptosis is triggered by tumour necrosis factor alpha and in-vitro experiments have shown that it can be induced by its second messenger sphingosine. Apoptosis correlates with the severity of the heart failure syndrome. It involves activation of caspases 3 and 9 and mitochondrial cytochrome c release.

Role of chymase-dependent angiotensin II formation in monocrotaline-induced pulmonary hypertensive rats

Angiotensin II-forming chymase is expressed in the pulmonary arteries of the monocrotaline-induced pulmonary hypertensive rats, but its actual role is unclear. We studied chymase-dependent angiotensin II formation in the pulmonary arteries of the monocrotaline-induced pulmonary hypertensive rats and observed the effects of an angiotensin II receptor blocker on vascular remodeling. Four weeks after the administration of monocrotaline (60 mg/kg, s.q.), echocardiographic, hemodynamic, morphometric and biochemical analyses were performed. Age-matched rats were used as controls. To evaluate the effects of an angiotensin II receptor blocker, 2 wk after beginning of monocrotaline treatment, the rats were given candesartan (10 mg/kg per day) or placebo for 2 wk. In the monocrotaline-induced pulmonary hypertensive rats, the elevated systolic pulmonary arterial pressure and right ventricular hypertrophy were observed. Medial hypertrophy of lung arterioles was also observed. Chymase activity and angiotensin II concentration, but not angiotensin-converting enzyme activity, were significantly increased in the lung. In the angiotensin II receptor blocker-treated group, both systolic pulmonary arterial pressure and right ventricular hypertrophy were significantly reduced, and arteriolar hypertrophy was also prevented. Thus, angiotensin II-forming chymase may play a role in the proliferation of the medial layer in the lung arterioles of monocrotaline-induced pulmonary hypertensive rats.

Effect of heart failure on skeletal muscle myofibrillar protein content, isoform expression and calcium sensitivity

BACKGROUND

Alterations in skeletal muscle with heart failure contribute to exercise intolerance and physical disability. The majority of studies to date have examined abnormalities in skeletal muscle oxidative capacity and mitochondrial function. In contrast, less information is available regarding the effect of heart failure on myofibrillar protein metabolism and function. To address this issue, we examined the effect of heart failure on skeletal muscle myofibrillar protein content, isoform distribution and Ca2+ sensitivity.

METHODS

We measured skeletal muscle myosin heavy chain (MHC) and actin protein content and MHC isoform distribution in soleus (SOL), extensor digitorum longus (EDL), plantaris (PL) and diaphragm (DIA) muscles and myofibrillar Ca2+ sensitivity in EDL muscles from Dahl salt-sensitive rats with (high-salt fed: HS; n=10) or without heart failure (low-salt fed: LS; n=8) and assessed the relationship of these variables to markers of disease severity.

RESULTS

No differences in muscle mass were found. Similarly, no differences in MHC (mean+/-SE; SOL: 1353+/-29 vs. 1247+/-52; EDL: 1471+/-31 vs. 1441+/-31; PL: 1207+/-66 vs. 1286+/-36; DIA: 1166+/-42 vs. 1239+/-26 AU/microg protein) or actin (EDL: 348+/-13 vs. 358+/-19; PL: 245+/-20 vs. 242+/-9; DIA: 383+/-9 vs. 376+/-17 AU/microg protein) protein content or the actin-to-MHC ratio were observed, with the exception of lower (P<0.01) actin content in the soleus of LS rats (352+/-7 vs. 310+/-8 AU/microg protein). MHC isoform expression (I, IIa, IIx, IIb) did not differ between groups in SOL (I: 89+/-1% vs. 85+/-2%; IIa: 11+/-1% vs. 15+/-2%), EDL (IIx: 43+/-10% vs. 38+/-10%; IIb: 57+/-10% vs. 62+/-10%), PL (I: 6+/-4% vs. 3+/-3%; IIa: 1+/-1% vs. 1+/-1%; IIx: 31+/-3% vs. 26+/-4%; IIb: 62+/-5% vs. 71+/-6%) or DIA (I: 43+/-6% vs. 36+/-6 %; IIa: 9+/-1% vs. 7+/-1%; IIx: 47+/-6% vs. 56+/-7%; IIb: 2+/-1% vs. 1+/-0.5%) muscles. Moreover, heart failure did not affect the Ca2+ sensitivity (i.e., pCa50) of extensor digitorum longus myofilaments (5.68+/-0.11 vs. 5.65+/-0.09). Finally, MHC and actin content, MHC isoform distribution and myofibrillar Ca2+ sensitivity were not related to markers of disease severity.

CONCLUSIONS

Our results show that this animal model of heart failure is not characterized by alterations in the quantity or isoform distribution of key skeletal muscle myofibrillar proteins or the Ca2+ sensitivity of isometric force production. These findings suggest that alterations in skeletal muscle myofibrillar protein metabolism do not develop in parallel with myocardial failure in the Dahl salt-sensitive rat.

Skeletal muscle fibres synthesis in heart failure: role of PGC-1alpha, calcineurin and GH

BACKGROUND

Patients with congestive heart failure (CHF) have decreased exercise capacity because of muscle fatigability. Symptoms are due to a specific myopathy with increased expression of fast type II fibres, fast MHCs and muscle atrophy. PGC-1alpha, a potent transcriptional coactivator for nuclear receptors, induces mitochondrial myogenesis and the preferential synthesis of slow fibres. IGF1-Calcineurin stimulation can lead to increased expression of PGC-1alpha.

METHODS

We investigated the levels of PGC-1alpha during progression and regression of skeletal myopathy in the soleus muscle of rats with right heart failure secondary to monocrotaline-induced pulmonary hypertension. We used GH to stimulate the IGF1-calcineurin-PGC-1alpha axis.

RESULTS

The slow MHC1 decreased from 90.6+/-0.5 to 71.7+/-2.2 in the CHF rats (p<0.00001) and increased to 82.1+/-1.8 after GH (p<0.00002). Western blot analysis showed that PGC-1alpha is significantly decreased in CHF, while it came back to control values after GH. Cytochrome c was decreased in CHF and returned to control values with GH. Troponin I was expressed solely as slow isoform in the control soleus, while the fast isoform appeared in CHF. Its expression returned to control values after GH.

CONCLUSIONS

We conclude that PGC-1alpha plays an important role in regulating slow fibres expression. PGC1-1alpha is in turn regulated by the IGF1-calcineurin axis. GH by increasing the circulating levels of IGF1, enhanced the expression of slow MHC1, TnI and the synthesis of mitochondria.

Angiotensin II induces apoptosisin vivoin skeletal, as well as cardiac, muscle of the rat

Our previous work has established that angiotensin II is cardiotoxic. Here we sought to investigate whether skeletal muscle is similarly susceptible to damage. Male Wistar rats were either given a single subcutaneous injection of angiotensin II (range 1 microg kg-1 to 10 mg kg-1) or only the vehicle and killed 7 h later, or implanted with preconditioned osmotic pumps dispensing 1 mg kg-1 day-1 angiotensin II and killed 9 or 18 h later. Apoptotic (caspase 3 positive) myocytes were counted on cryosections of the heart, soleus, tibialis anterior and diaphragm muscle. Single injections of 100 microg kg-1 to 10 mg kg-1 angiotensin II induced significant (P<0.05) myocyte apoptosis (per 10(4) viable myocytes) in the heart and this was heterogeneously distributed, peaking (5.7+/-0.6; P<0.05) at a point 6 mm from the apex, i.e. approximately three-quarters of the way towards the base. The slow-twitch soleus muscle was also damaged significantly (peak=2.6+/-0.4; P<0.05), while only the administration of 1 mg kg-1 induced significant (P<0.05) apoptosis in the fast-twitch tibialis anterior muscle (peak=1.2+/-0.3). Infusion of 1 mg kg-1 day-1 angiotensin II induced more myocyte apoptosis than a single bolus administration of the same dose, and in general there was a higher incidence of apoptosis in muscles harvested after 18 than after 9 h. Infusion of 1 mg kg-1 day-1 angiotensin II over 18 h induced significant (P<0.05) myocyte apoptosis in the heart (3.3+/-0.4), soleus (3.9+/-1), tibialis anterior (5.9+/-0.4) and diaphragm (19.8+/-5.6) muscle. Depending on the muscle type, angiotensin II induces myocyte apoptosis in skeletal muscle to a similar or greater extent as in cardiac muscle, supporting the hypothesis that angiotensin II is generally toxic to all striated muscles.

Pathophysiology of peripheral muscle wasting in cardiac cachexia

PURPOSE OF REVIEW

Many different mechanisms have been proposed to explain muscle wasting in patients with heart failure; however, the pathogenesis remains largely obscure. This manuscript looks at current developments concerning the pathophysiology of skeletal muscle wasting in cardiac cachexia.

RECENT FINDINGS

Many studies have shown that malnutrition, malabsorption, metabolic dysfunction, anabolic/catabolic imbalance, inflammatory and neurohormonal activation, and cell death play an important role in the pathogenesis of wasting in cardiac cachexia. However, the aetiology of the muscle changes is not entirely clear. In biopsies of skeletal muscles from animals with cardiac cachexia increased rates of protein degradation have been observed, with increased activity of the ubiquitin-proteasome proteolytic pathway. Skeletal muscle apoptosis may also play a role in muscle atrophy and wasting and can be partly prevented by neurohormonal inhibition, but it has recently been reported that in cachectic patients with chronic heart failure apoptosis is not the main pathway of cell death and muscle loss.

SUMMARY

Many hypotheses have been used to explain the pathogenesis of muscle wasting in cardiac cachexia. Cardiac cachexia is a multifactorial disorder, and the targeting of different pathways will be necessary for effective treatment. The immune and neurohormonal abnormalities present in chronic heart failure may play a significant role in the pathogenesis of the wasting process. It has been suggested that common pathogenetic mechanisms underlie the loss of muscle mass in different cachectic states. More studies are needed to show whether there is a common pathway in cardiac cachexia and the other cachectic states.