Specific changes in skeletal muscle myosin heavy chain composition in cardiac failure: differences compared with disuse atrophy as assessed on microbiopsies by high resolution electrophoresis

Translational mobility medicine and ugo carraro: a life of significant scientific contributions reviewed in celebration

Prof. Ugo Carraro reached 80 years of age on 23 February 2023, and we wish to celebrate him and his work by reviewing his lifetime of scientific achievements in Translational Myology. Currently, he is a Senior Scholar with the University of Padova, Italy, where, as a tenured faculty member, he founded the Interdepartmental Research Center of Myology. Prof. Carraro, a pioneer in skeletal muscle research, is a world-class expert in structural and molecular investigations of skeletal muscle biology, physiology, pathology, and care. An authority in bidimensional gel electrophoresis for myosin light chains, he was the first to separate mammalian muscle myosin heavy chain isoforms by SDS-gel electrophoresis. He has demonstrated that long-term denervated muscle can survive denervation by myofiber regeneration, and shown that an athletic lifestyle has beneficial impacts on muscle reinnervation. He has utilized his expertise in translational myology to develop and validate rehabilitative treatments for denervated and ageing skeletal muscle. He has authored more than 160 PubMed listed papers and numerous scholarly books, including his recent autobiography. Prof. Carraro founded and serves as Editor-in-Chief of the European Journal of Translational Myology and Mobility Medicine. He has organized more than 40 Padua Muscle Days Meetings and continues this, encouraging students and young scientists to participate. As he dreams endlessly, he is currently validating non-invasive analyses on saliva, a promising approach that will allow increased frequency sampling to analyze systemic factors during the transient effects of training and rehabilitation by his proposed Full-Body in- Bed Gym for bed-ridden elderly.

Weight loss during follow-up in patients with acute heart failure: From the KCHF registry

BACKGROUNDS

The prognostic implication of weight loss after discharge from acute heart failure (AHF) remains unclear. We sought to investigate the association of weight loss between discharge and 6-month visit with subsequent clinical outcomes in patients with AHF.

METHODS

We analyzed 686 patients with AHF in the prospective longitudinal follow-up study derived from the Kyoto Congestive Heart Failure registry, and divided them into 2 groups based on the weight loss at 6-month index visit. We defined the weight loss as ≥ 5% decrease in body weight from discharge to 6-month index visit.

RESULTS

There were 90 patients (13.1%) with a weight loss at 6-month visit. Patients in the weight loss group compared with those in the no weight loss group had higher body weight at discharge and lower body weight at 6-mont visit. Patients in the weight loss group had a lower systolic blood pressure, higher brain-type natriuretic peptide, lower serum albumin, lower hemoglobin, higher prevalence of heart failure with reduced ejection fraction at 6-month visit, and a lower prescription rate of inhibitors of renin-angiotensin system than those in the no weight loss group. The cumulative 6-month incidence of all-cause death was significantly higher in the weight loss group than in the no weight loss group (14.2% and 4.3%, log-rank P<0.001). The excess adjusted risk of the weight loss group relative to the no weight loss group remained significant for all-cause death (HR 2.39, 95%CI 1.01-5.65, P = 0.048).

CONCLUSION

Body weight loss of ≥5% at 6-month visit after discharge was associated with subsequent all-cause death in patients with AHF.

Possibility for Visualizing the Muscle Microstructure by q-Space Imaging Technique

In the human body, skeletal muscle microstructures have been evaluated only by biopsy. Noninvasive examination of the microstructure of muscles would be useful for research and clinical practice in sports and musculoskeletal areas. The study is aimed at determining if q-space imaging (QSI) can reveal the microstructure of muscles in humans. Forty-three Japanese subjects (controls, distance runners, powerlifting athletes, and teenage runners) were included in this cross-sectional study. Magnetic resonance imaging of the lower leg was performed. On each leg muscle, full width at half maximum (FWHM) which indicated the muscle cell diameters and pennation angle (PA) were measured and compared. FWHM showed significant positive correlations with PA, which is related to muscle strength. In addition, FWHM was higher for powerlifting, control, distance running, and teenager, in that order, suggesting that it may be directing the diameter of each muscle cell. Type 1 and type 2 fibers are enlarged by growth, so the fact that the FWHM of the control group was larger than that of the teenagers in this study may indicate that the muscle fibers were enlarged by growth. Also, FWHM has the possibility to increase with increased muscle fibers caused by training. We showed that QSI had the possibility to depict noninvasively the microstructure like muscle fiber type and subtle changes caused by growth and sports characteristics, which previously could only be assessed by biopsy.

Microbiopsy Sampling for Examining Age-Related Differences in Skeletal Muscle Fiber Morphology and Composition

Introduction: The increasingly popular microbiopsy is an appealing alternative to the more invasive Bergström biopsy given the challenges associated with harvesting skeletal muscle in older populations. Parameters of muscle fiber morphology and composition derived from the microbiopsy have not been compared between young and older adults.

Purpose: The purpose of this study was to examine muscle fiber morphology and composition in young (YM) and older (OM) males using the microbiopsy sampling technique. A secondary aim was to determine if specific strength is associated with serum levels of C-terminal agrin fragment [CAF; an indicator of neuromuscular junction (NMJ) degradation].

Methods: Thirty healthy, YM (n = 15, age = 20.7 ± 2.2 years) and OM (n = 15, age = 71.6 ± 3.9 years) underwent ultrasound imaging to determine whole-muscle cross-sectional area (CSA) of the vastus lateralis and rectus femoris as well as isometric and isokinetic (60°⋅s^–1 and 180°⋅s^–1) peak torque testing of the knee extensors. Microbiopsy samples of the vastus lateralis were collected from 13 YM and 11 OM, and immunofluorescence was used to calculate CSA and proportion of type I and type II fibers.

Results: Peak torque was lower in OM at all velocities (p ≤ 0.001; d = 1.39–1.86) but only lower at 180°⋅s^–1 (p = 0.003; d = 1.23) when normalized to whole-muscle CSA. Whole-muscle CSA was smaller in OM (p = 0.001; d = 1.34), but atrophy was not present at the single fiber level (p > 0.05). Per individual, ∼900 fibers were analyzed, and type I fiber CSA was larger (p = 0.05; d = 0.94) in OM which resulted in a smaller type II/I fiber CSA ratio (p = 0.015; d = 0.95). CAF levels were not sensitive to age (p = 0.159; d = 0.53) nor associated with specific strength or whole-muscle CSA in OM.

Conclusion: The microbiopsy appears to be a viable alternative to the Bergström biopsy for histological analyses of skeletal muscle in older adults. NMJ integrity was not influential for age-related differences in specific strength in our healthy, non-sarcopenic older sample.

Low skeletal muscle mass is associated with low aerobic capacity and increased mortality risk in patients with coronary heart disease - a CARE CR study

BACKGROUND

In patients with chronic heart failure, there is a positive linear relationship between skeletal muscle mass (SMM) and peak oxygen consumption ( V ˙ O_2peak ); an independent predictor of all-cause mortality_. We investigated the association between SMM and V ˙ O_2peak in patients with coronary heart disease (CHD) without a diagnosis of heart failure.

METHODS

Male patients with CHD underwent maximal cardiopulmonary exercise testing and dual X-ray absorptiometry assessment. V ˙ O_2peak, the ventilatory anaerobic threshold and peak oxygen pulse were calculated. SMM was expressed as appendicular lean mass (lean mass in both arms and legs) and reported as skeletal muscle index (SMI; kg m^-2 ), and as a proportion of total body mass (appendicular skeletal mass [ASM%]). Low SMM was defined as a SMI <7·26 kg m^-2 , or ASM% <25·72%. Five-year all-cause mortality risk was calculated using the Calibre 5-year all-cause mortality risk score.

RESULTS

Sixty patients were assessed. Thirteen (21·7%) had low SMM. SMI and ASM% correlated positively with V ˙ O_2peak (r = 0·431 and 0·473, respectively; P<0·001 for both). SMI and ASM% predicted 16·3% and 12·9% of the variance in V ˙ O_2peak , respectively. SMI correlated most closely with peak oxygen pulse (r = 0·58; P<0·001). SMI predicted 40·3% of peak V ˙ O₂ /HR variance. ASM% was inversely associated with 5-year all-cause mortality risk (r = -0·365; P = 0·006).

CONCLUSION

Skeletal muscle mass was positively correlated with V ˙ O_2peak in patients with CHD. Peak oxygen pulse had the strongest association with SMM. Low ASM% was associated with a higher risk of all-cause mortality. The effects of exercise and nutritional strategies aimed at improving SMM and function in CHD patients should be investigated.

Effects of aging and comorbidities on nutritional status and muscle dysfunction in patients with COPD

Chronic obstructive pulmonary disease (COPD) is a prevalent, complex and debilitating disease which imposes a formidable burden on patients and the healthcare system. The recognition that COPD is a multifaceted disease is not new, and increasing evidence have outlined the importance of its extra-pulmonary manifestations and its relation to other comorbid conditions in the clinical course of the disease and its societal cost. The relationship between aging, COPD and its comorbidities on skeletal muscle function and nutritional status is complex, multidirectional and incompletely understood. Despite this, the current body of knowledge allows the identification of various, seemingly partially independent factors related both to the normal aging process and to the independent deleterious effects of chronic diseases on muscle function and body composition. There is a dire need of studies evaluating the relative contribution of each of these factors, and their potential synergistic effects in patients with COPD and advanced age/comorbid conditions, in order to delineate the best course of therapeutic action in this increasingly prevalent population.

Lipid modulation of skeletal muscle mass and function

Loss of skeletal muscle mass is a characteristic feature of various pathologies including cancer, diabetes, and obesity, as well as being a general feature of ageing. However, the processes underlying its pathogenesis are not fully understood and may involve multiple factors. Importantly, there is growing evidence which supports a role for fatty acids and their derived lipid intermediates in the regulation of skeletal muscle mass and function. In this review, we discuss evidence pertaining to those pathways which are involved in the reduction, increase and/or preservation of skeletal muscle mass by such lipids under various pathological conditions, and highlight studies investigating how these processes may be influenced by dietary supplementation as well as genetic and/or pharmacological intervention.

Skeletal muscle inflammation and atrophy in heart failure

Heart failure represents a systemic disease with profound effects on multiple peripheral tissues including skeletal muscle. Within the context of heart failure, perturbations in skeletal muscle physiology, structure, and function strongly contribute to exercise intolerance and the morbidity of this devastating disease. There is growing evidence that chronic heart failure imparts specific pathological changes within skeletal muscle beds resulting in muscle dysfunction and tissue atrophy. Mechanistically, systemic and local inflammatory responses drive critical aspects of this pathology. In this review, we will discuss pathological mechanisms that drive skeletal muscle inflammation and highlight emerging roles for distinct innate immune subsets that reside within damage muscle tissue focusing on the recently described embryonic and monocyte-derived macrophage lineages. Within this context, we will discuss how immune mechanisms can be differentially targeted to stimulate skeletal muscle inflammation, catabolism, fiber atrophy, and regeneration.

Exertional dyspnoea in chronic heart failure: the role of the lung and respiratory mechanical factors

Exertional dyspnoea is among the dominant symptoms in patients with chronic heart failure and progresses relentlessly as the disease advances, leading to reduced ability to function and engage in activities of daily living. Effective management of this disabling symptom awaits a better understanding of its underlying physiology.

Cardiovascular factors are believed to play a major role in dyspnoea in heart failure patients. However, despite pharmacological interventions, such as vasodilators or inotropes that improve central haemodynamics, patients with heart failure still complain of exertional dyspnoea. Clearly, dyspnoea is not determined by cardiac factors alone, but likely depends on complex, integrated cardio-pulmonary interactions.

A growing body of evidence suggests that excessively increased ventilatory demand and abnormal “restrictive” constraints on tidal volume expansion with development of critical mechanical limitation of ventilation, contribute to exertional dyspnoea in heart failure. This article will offer new insights into the pathophysiological mechanisms of exertional dyspnoea in patients with chronic heart failure by exploring the potential role of the various constituents of the physiological response to exercise and particularly the role of abnormal ventilatory and respiratory mechanics responses to exercise in the perception of dyspnoea in patients with heart failure.

Skeletal Muscle Abnormalities in Heart Failure

Exercise capacity is lowered in patients with heart failure, which limits their daily activities and also reduces their quality of life. Furthermore, lowered exercise capacity has been well demonstrated to be closely related to the severity and prognosis of heart failure. Skeletal muscle abnormalities including abnormal energy metabolism, transition of myofibers from type I to type II, mitochondrial dysfunction, reduction in muscular strength, and muscle atrophy have been shown to play a central role in lowered exercise capacity. The skeletal muscle abnormalities can be classified into the following main types: 1) low endurance due to mitochondrial dysfunction; and 2) low muscle mass and muscle strength due to imbalance of protein synthesis and degradation. The molecular mechanisms of these skeletal muscle abnormalities have been studied mainly using animal models. The current review including our recent study will focus upon the skeletal muscle abnormalities in heart failure.

Exercise training in chronic heart failure: improving skeletal muscle O2 transport and utilization

Chronic heart failure (CHF) impairs critical structural and functional components of the O2 transport pathway resulting in exercise intolerance and, consequently, reduced quality of life. In contrast, exercise training is capable of combating many of the CHF-induced impairments and enhancing the matching between skeletal muscle O2 delivery and utilization (Q̇mO2 and V̇mO2 , respectively). The Q̇mO2 /V̇mO2 ratio determines the microvascular O2 partial pressure (PmvO2 ), which represents the ultimate force driving blood-myocyte O2 flux (see Fig. 1). Improvements in perfusive and diffusive O2 conductances are essential to support faster rates of oxidative phosphorylation (reflected as faster V̇mO2 kinetics during transitions in metabolic demand) and reduce the reliance on anaerobic glycolysis and utilization of finite energy sources (thus lowering the magnitude of the O2 deficit) in trained CHF muscle. These adaptations contribute to attenuated muscle metabolic perturbations (e.g., changes in [PCr], [Cr], [ADP], and pH) and improved physical capacity (i.e., elevated critical power and maximal V̇mO2 ). Preservation of such plasticity in response to exercise training is crucial considering the dominant role of skeletal muscle dysfunction in the pathophysiology and increased morbidity/mortality of the CHF patient. This brief review focuses on the mechanistic bases for improved Q̇mO2 /V̇mO2 matching (and enhanced PmvO2 ) with exercise training in CHF with both preserved and reduced ejection fraction (HFpEF and HFrEF, respectively). Specifically, O2 convection within the skeletal muscle microcirculation, O2 diffusion from the red blood cell to the mitochondria, and muscle metabolic control are particularly susceptive to exercise training adaptations in CHF. Alternatives to traditional whole body endurance exercise training programs such as small muscle mass and inspiratory muscle training, pharmacological treatment (e.g., sildenafil and pentoxifylline), and dietary nitrate supplementation are also presented in light of their therapeutic potential. Adaptations within the skeletal muscle O2 transport and utilization system underlie improvements in physical capacity and quality of life in CHF and thus take center stage in the therapeutic management of these patients.

Skeletal myopathy in patients with chronic heart failure: significance of anabolic-androgenic hormones

In heart failure, impairment of cardiac muscle function leads to numerous neurohormonal and metabolic disorders, including an imbalance between anabolic and catabolic processes, in favour of the latter. These disorders cause loss of muscle mass with structural and functional changes within the skeletal muscles, known as skeletal myopathy. This phenomenon constitutes an important mechanism that participates in the pathogenesis of chronic heart failure. both its clinical symptoms and the progression of the disease. Attempts to reverse the above-mentioned pathologic processes by exploiting the anabolic action of androgenic hormones could provide a potentially attractive treatment option. The current concepts of anabolic androgen deficiency and resultant skeletal myopathy in patients with heart failure are reviewed, and the potential role of anabolic-androgenic hormones as an emerging therapeutic option for targeting heart failure is discussed.

Skeletal muscle myofilament adaptations to aging, disease, and disuse and their effects on whole muscle performance in older adult humans

Skeletal muscle contractile function declines with aging, disease, and disuse. In vivo muscle contractile function depends on a variety of factors, but force, contractile velocity and power generating capacity ultimately derive from the summed contribution of single muscle fibers. The contractile performance of these fibers are, in turn, dependent upon the isoform and function of myofilament proteins they express, with myosin protein expression and its mechanical and kinetic characteristics playing a predominant role. Alterations in myofilament protein biology, therefore, may contribute to the development of functional limitations and disability in these conditions. Recent studies suggest that these conditions are associated with altered single fiber performance due to decreased expression of myofilament proteins and/or changes in myosin-actin cross-bridge interactions. Furthermore, cellular and myofilament-level adaptations are related to diminished whole muscle and whole body performance. Notably, the effect of these various conditions on myofilament and single fiber function tends to be larger in older women compared to older men, which may partially contribute to their higher rates of disability. To maintain functionality and provide the most appropriate and effective countermeasures to aging, disease, and disuse in both sexes, a more thorough understanding is needed of the contribution of myofilament adaptations to functional disability in older men and women and their contribution to tissue level function and mobility impairment.

Discerning primary and secondary factors responsible for clinical fatigue in multisystem diseases

Fatigue is a common symptom of numerous acute and chronic diseases, including myalgic encephalomyelitis/chronic fatigue syndrome, multiple sclerosis, heart failure, cancer, and many others. In these multi-system diseases the physiological determinants of enhanced fatigue encompass a combination of metabolic, neurological, and myofibrillar adaptations. Previous research studies have focused on adaptations specific to skeletal muscle and their role in fatigue. However, most have neglected the contribution of physical inactivity in assessing disease syndromes, which, through deconditioning, likely contributes to symptomatic fatigue. In this commentary, we briefly review disease-related muscle phenotypes in the context of whether they relate to the primary disease or whether they develop secondary to reduced physical activity. Knowledge of the etiology of the skeletal muscle adaptations in these conditions and their contribution to fatigue symptoms is important for understanding the utility of exercise rehabilitation as an intervention to alleviate the physiological precipitants of fatigue.

Clinical and symptomatological reflections: the fascial system

Every body structure is wrapped in connective tissue, or fascia, creating a structural continuity that gives form and function to every tissue and organ. Currently, there is still little information on the functions and interactions between the fascial continuum and the body system; unfortunately, in medical literature there are few texts explaining how fascial stasis or altered movement of the various connective layers can generate a clinical problem. Certainly, the fascia plays a significant role in conveying mechanical tension, in order to control an inflammatory environment. The fascial continuum is essential for transmitting muscle force, for correct motor coordination, and for preserving the organs in their site; the fascia is a vital instrument that enables the individual to communicate and live independently. This article considers what the literature offers on symptoms related to the fascial system, trying to connect the existing information on the continuity of the connective tissue and symptoms that are not always clearly defined. In our opinion, knowing and understanding this complex system of fascial layers is essential for the clinician and other health practitioners in finding the best treatment strategy for the patient.

Can proinflammatory cytokine gene expression explain multifidus muscle fiber changes after an intervertebral disc lesion?

STUDY DESIGN

Longitudinal case-controlled animal study.

OBJECTIVE

To investigate the effect of an intervertebral disc (IVD) lesion on the proportion of slow, fast, and intermediate muscle fiber types in the multifidus muscle in sheep, and whether muscle fiber changes were paralleled by local gene expression of the proinflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin 1-β.

SUMMARY OF BACKGROUND DATA

Structure and behavior of the multifidus muscle change in acute and chronic back pain, but the mechanisms are surprisingly poorly understood and the link between structure and behavior is tenuous. Although changes in muscle fiber types have the potential to unify the observations, the effect of injury on muscle fiber distribution has not been adequately tested, and understanding of possible mechanisms is limited.

METHODS

The L1-L2, L3-L4, and L5-L6 IVDs of 11 castrated male sheep received anterolateral lesions. Six control sheep underwent no surgical procedures. Multifidus muscle tissue was harvested at L4 for muscle fiber analysis using immunohistochemistry and L2 for cytokine analysis with polymerase chain reaction for local gene expression of TNF-α and interleukin-1β.

RESULTS

The proportion of slow muscle fibers in multifidus was significantly less in the lesioned animals both ipsilateral and contralateral to the IVD lesion. The greatest reduction in slow fibers was in the deep medial muscle region. A greater prevalence of intermediate fibers on the uninjured side implies a delayed fiber-type transformation on that side. TNF-α gene expression in multifidus was greater on both sides in the lesion animals than in the muscle of control animals. Interleukin-1β was increased only on the injured side.

CONCLUSION

These data provide evidence of muscle fiber changes after induction of an IVD lesion and a parallel increase in TNF-α expression. Proinflammatory cytokine changes provide a novel mechanism to explain behavioral and structural changes in multifidus.

LEVEL OF EVIDENCE

N/A.

CIR-Myo News: Proceedings of the 2014 Spring Padua Muscle Days: Terme Euganee and Padova (Italy), April 3-5, 2014

Not available.

Home-Based Functional Electrical Stimulation for Long-Term Denervated Human Muscle: History, Basics, Results and Perspectives of the Vienna Rehabilitation Strategy

We will here discuss the following points related to Home-based Functional Electrical Stimulation (h-b FES) as treatment for patients with permanently denervated muscles in their legs: 1. Upper (UMN) and lower motor neuron (LMN) damage to the lower spinal cord; 2. Muscle atrophy/hypertrophy versus processes of degeneration, regeneration, and recovery; 3. Recovery of twitch- and tetanic-contractility by h-b FES; 4. Clinical effects of h-b FES using the protocol of the "Vienna School"; 5. Limitations and perspectives. Arguments in favor of using the Vienna protocol include: 1. Increased muscle size in both legs; 2. Improved tetanic force production after 3-5 months of percutaneous stimulation using long stimulus pulses (> 100 msec) of high amplitude (> 80 mAmp), tolerated only in patients with no pain sensibility; 3. Histological and electron microscopic evidence that two years of h-b FES return muscle fibers to a state typical of two weeks denervated muscles with respect to atrophy, disrupted myofibrillar structure, and disorganized Excitation-Contraction Coupling (E-CC) structures; 4. The excitability never recovers to that typical of normal or reinnervated muscles where pulses less than 1 msec in duration and 25 mAmp in intensity excite axons and thereby muscle fibres. It is important to motivate these patients for chronic stimulation throughout life, preferably standing up against the load of the body weight rather than sitting. Only younger and low weight patients can expect to be able to stand-up and do some steps more or less independently. Some patients like to maintain the h-b FES training for decades. Limitations of the procedure are obvious, in part related to the use of multiple, large surface electrodes and the amount of time patients are willing to use for such muscle training.

Skeletal muscle abnormalities and exercise intolerance in older patients with heart failure and preserved ejection fraction

Heart failure (HF) with preserved ejection fraction (HFPEF) is the most common form of HF in older persons. The primary chronic symptom in HFPEF is severe exercise intolerance, and its pathophysiology is poorly understood. To determine whether skeletal muscle abnormalities contribute to their severely reduced peak exercise O2 consumption (Vo2), we examined 22 older HFPEF patients (70 ± 7 yr) compared with 43 age-matched healthy control (HC) subjects using needle biopsy of the vastus lateralis muscle and cardiopulmonary exercise testing to assess muscle fiber type distribution and capillarity and peak Vo2. In HFPEF versus HC patients, peak Vo2 (14.7 ± 2.1 vs. 22.9 ± 6.6 ml·kg(-1)·min(-1), P < 0.001) and 6-min walk distance (454 ± 72 vs. 573 ± 71 m, P < 0.001) were reduced. In HFPEF versus HC patients, the percentage of type I fibers (39.0 ± 11.4% vs. 53.7 ± 12.4%, P < 0.001), type I-to-type II fiber ratio (0.72 ± 0.39 vs. 1.36 ± 0.85, P = 0.001), and capillary-to-fiber ratio (1.35 ± 0.32 vs. 2.53 ± 1.37, P = 0.006) were reduced, whereas the percentage of type II fibers was greater (61 ± 11.4% vs. 46.3 ± 12.4%, P < 0.001). In univariate analyses, the percentage of type I fibers (r = 0.39, P = 0.003), type I-to-type II fiber ratio (r = 0.33, P = 0.02), and capillary-to-fiber ratio (r = 0.59, P < 0.0001) were positively related to peak Vo2. In multivariate analyses, type I fibers and the capillary-to-fiber ratio remained significantly related to peak Vo2. We conclude that older HFPEF patients have significant abnormalities in skeletal muscle, characterized by a shift in muscle fiber type distribution with reduced type I oxidative muscle fibers and a reduced capillary-to-fiber ratio, and these may contribute to their severe exercise intolerance. This suggests potential new therapeutic targets in this difficult to treat disorder.

Exercise intolerance in chronic heart failure: the role of cortisol and the catabolic state

Chronic heart failure (CHF) is a complex clinical syndrome leading to exercise intolerance due to muscular fatigue and dyspnea. Hemodynamics fail to explain the reduced exercise capacity, while a significant skeletal muscular pathology seems to constitute the main underlying mechanism for exercise intolerance in CHF patients. There have been proposed several metabolic, neurohormonal and immune system abnormalities leading to an anabolic/catabolic imbalance that plays a central role in the pathogenesis of the wasting process of skeletal muscle myopathy. The impairment of the anabolic axes is associated with the severity of symptoms and the poor outcome in CHF, whereas increased cortisol levels are predictive of exercise intolerance, ventilatory inefficiency and chronotropic incompetence, suggesting a significant contributing mechanism to the limited functional status. Exercise training and device therapy could have beneficial effects in preventing and treating muscle wasting in CHF. However, specific anabolic treatment needs more investigation to prove possible beneficial effects.

Myofibrillar protein overdegradation in overweight patients with chronic heart failure: the relationship to serum potassium levels

OBJECTIVES

Muscle release of the amino acid 3-methyl-histidine (3MH) is a sensitive index of myofibrillar protein overdegradation (MPO). We hypothesized that patients with chronic heart failure (CHF) could have increased muscle release of 3MH, which in turn reflects MPO, and that serum electrolyte sodium (Na(+)) and potassium (K(+)) levels may be associated with this 3MH muscle release.

METHODS

Thirty-one overweight outpatients (body mass index, 27 ± 4.4 kg/m(2); 22 men and 9 women; age, 56 ± 8.7 y) with clinically stable CHF were studied. After a 24-hour meat-free diet and overnight fasting, patients underwent blood sampling from a cannulated arm vein (V) and concomitantly from the arterial artery (A) to determine plasma 3MH levels and to calculate the A-V difference. Serum levels of Na(+) and K(+) in the venous blood were determined, and the Na(+)/K(+) ratio was calculated. Ten healthy subjects who were matched for gender, age, and body mass index served as controls and underwent the same protocol as the patients with CHF.

RESULTS

The patient group had higher arterial (P = 0.02) and venous (P = 0.005) 3MH levels but a similar A-V 3MH difference (P = 0.28) as compared with the controls. Within the CHF group, 67.7% of patients released 3MH, which resulted in a negative A-V value (P < 0.02 as compared with controls). In patients with CHF, the A-V 3MH difference correlated positively with the serum K(+) level (r = 0.62; P = 0.0002) and negatively with Na(+)/K(+) ratio (r = -0.55; P = 0.002). No association was found between the A-V 3MH difference and the Na(+) level.

CONCLUSIONS

The study demonstrated the existence of MPO in resting overweight patients with CHF, thereby suggesting that low serum levels of K(+) may contribute to MPO.

Association of adiponectin with peripheral muscle status in elderly patients with heart failure

BACKGROUND

Reduced peripheral muscle mass was demonstrated in patients with chronic heart failure (HF). Adipokines may have potent metabolic effects on skeletal muscle. The associations between adipokines, peripheral muscle mass, and muscle function have been poorly investigated in patients with HF.

METHODS

We measured markers of fat and bone metabolism (adiponectin, leptin, 25-hydroxy vitamin D, parathyroid hormone, osteoprotegerin, RANKL), N-terminal pro B-type natriuretic peptide (NT-pro-BNP) in 73 non-cachectic, non-diabetic, male patients with chronic HF (age: 68 ± 7 years, New York Heart Association class II/III: 76/26%, left ventricular ejection fraction 29 ± 8%) and 20 healthy controls of similar age. Lean mass as a measure of skeletal muscle mass was measured by dual energy X-ray absorptiometry (DEXA), while muscle strength was assessed by hand grip strength measured by Jamar dynamometer.

RESULTS

Serum levels of adiponectin, parathyroid hormone, osteoprotegerin, RANKL, and NT-pro-BNP were elevated in patients with chronic HF compared to healthy controls (all p<0.0001), while no difference in serum levels of leptin, testosterone or SHBG was noted. Levels of 25-hydroxy vitamin D were reduced (p=0.002) in HF group. Peripheral lean mass and hand grip strength were reduced in patients with HF compared to healthy subjects (p=0.006 and p<0.0001, respectively). Using backward selection multivariable regression, serum levels of increased adiponectin remained significantly associated with reduced arm lean mass and muscle strength.

CONCLUSIONS

Our findings may indicate a cross-sectional metabolic association of increased serum adiponectin with reduced peripheral muscle mass and muscle strength in non-cachectic, non-diabetic, elderly HF patients.

Intact skeletal muscle mitochondrial enzyme activity but diminished exercise capacity in advanced heart failure patients on optimal medical and device therapy

BACKGROUND

A skeletal myopathy, perhaps attributable to neuro-endocrine excitation or disuse, has been described in heart failure (HF) patients, and is thought to contribute to their exercise limitation. Our purpose was to assess biochemical and morphometric characteristics of skeletal muscles of HF patients on optimal HF therapy. A secondary purpose was to explore the effects of clonidine, which interrupts the neuro-endocrine excitation, on these same muscle characteristics.

METHODS AND RESULTS

Eleven HF patients (50.8 ± 3.4 years, peak VO2 11.6 ± 2.5 ml/kg/min) underwent two vastus lateralis biopsies (pre/post clonidine). Baseline values were compared to biopsies in 11 age-matched, healthy controls. Scatter plots of individual values for each mitochondrial enzyme revealed almost complete overlap between HF and control groups; mean values, although tending to be greater in controls versus HF patients, were not significantly different. The proportion of type 1 fibers was diminished in 10 of 11 patients. There was no difference in any of the variables after 3 months clonidine versus placebo.

CONCLUSION

In HF patients treated with optimal medical and device therapy, characteristic abnormalities of mitochondrial enzyme activity are not found, but muscle fiber type shifts are present. The remaining severe impairment in exercise capacity cannot be attributed to mitochondrial abnormalities.

Intrinsic skeletal muscle alterations in chronic heart failure patients: a disease-specific myopathy or a result of deconditioning?

Chronic heart failure (CHF) patients frequently experience impaired exercise tolerance due to skeletal muscle fatigue. Studies suggest that this in part is due to intrinsic alterations in skeletal muscle of CHF patients, often interpreted as a disease-specific myopathy. Knowledge about the mechanisms underlying these skeletal muscle alterations is of importance for the pathophysiological understanding of CHF, therapeutic approach and rehabilitation strategies. We here critically review the evidence for skeletal muscle alterations in CHF, the underlying mechanisms of such alterations and how skeletal muscle responds to training in this patient group. Skeletal muscle characteristics in CHF patients are very similar to what is reported in response to chronic obstructive pulmonary disease (COPD), detraining and deconditioning. Furthermore, skeletal muscle alterations observed in CHF patients are reversible by training, and skeletal muscle of CHF patients seems to be at least as trainable as that of matched controls. We argue that deconditioning is a major contributor to the skeletal muscle dysfunction in CHF patients and that further research is needed to determine whether, and to what extent, the intrinsic skeletal muscle alterations in CHF represent an integral part of the pathophysiology in this disease.

Abnormalities of calcium handling proteins in skeletal muscle mirror those of the heart in humans with heart failure: a shared mechanism?

BACKGROUND

In the failing human heart, abnormalities of Ca(2+) cycling have been described, but there is scant knowledge about Ca(2+) handling in the skeletal muscle of humans with heart failure (HF). We tested the hypothesis that in humans with HF, Ca(2+) cycling proteins in skeletal muscle are abnormal.

METHODS AND RESULTS

Ten advanced HF patients (50.4 ± 3.7 years), and 9 age-matched controls underwent vastus lateralis biopsy. Western blot analysis showed that sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA)2a, which is responsible for Ca(2+) sequestration into the sarcoplasmic reticulum(SR), was lower in HF versus controls (4.8 ± 0.5 vs 7.5 ± 0.8 AU, P = .01). Although phospholamban (PLN), which inhibits SERCA2a, was not different in HF versus controls, phosphorylation (SER16 site) of PLN, which relieves this inhibition, was reduced (0.8 ± 0.1 vs 3.9 ± 0.9 AU, P = .004). Dihydropyridine receptors were reduced in HF, (2.1 ± 0.4 vs 3.6 ± 0.5 AU, P = .04). We tested the hypothesis that these abnormalities of Ca(2+) handling protein content and regulation were due to increased oxidative stress, but oxygen radical scavenger proteins were not elevated in the skeletal muscle of HF patients.

CONCLUSION

In chronic HF, marked abnormalities of Ca(2+) handling proteins are present in skeletal muscle, which mirror those in failing heart tissue. This suggests a common mechanism, such as chronic augmentation of sympathetic activity and autophosphorylation of Ca(2+)-calmodulin-dependent-protein kinase II.

Skeletal muscle molecular alterations precede whole-muscle dysfunction in NYHA Class II heart failure patients

Background

Heart failure (HF), a debilitating disease in a growing number of adults, exerts structural and neurohormonal changes in both cardiac and skeletal muscles. However, these alterations and their affected molecular pathways remain uncharacterized. Disease progression is known to transform skeletal muscle fiber composition by unknown mechanisms. In addition, perturbation of specific hormonal pathways, including those involving skeletal muscle insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-binding protein-5 (IGFB-5) appears to occur, likely affecting muscle metabolism and regeneration. We hypothesized that changes in IGF-1 and IGFB-5 mRNA levels correlate with the transformation of single–skeletal muscle fiber myosin heavy chain isoforms early in disease progression, making these molecules valuable markers of skeletal muscle changes in heart failure.

Materials and methods

To investigate these molecules during “early” events in HF patients, we obtained skeletal muscle biopsies from New York Heart Association (NYHA) Class II HF patients and controls for molecular analyses of single fibers, and we also quantified isometric strength and muscle size.

Results

There were more (P < 0.05) single muscle fibers coexpressing two or more myosin heavy chains in the HF patients (30% ± 7%) compared to the control subjects (13% ± 2%). IGF-1 and IGFBP-5 expression was fivefold and 15-fold lower in patients with in HF compared to control subjects (P < 0.05), respectively. Strikingly, there was a correlation in IGF-1 expression and muscle cross-sectional area (P < 0.05) resulting in a decrease in whole-muscle quality (P < 0.05) in the HF patients, despite no significant decrease in isometric strength or whole-muscle size.

Conclusion

These data indicate that molecular alterations in myosin heavy chain isoforms, IGF-1, and IGFB-5 levels precede the gross morphological and functional deficits that have previously been associated with HF, and may be used as a predictor of functional outcome in patients.

Mechanisms underlying skeletal muscle weakness in human heart failure: alterations in single fiber myosin protein content and function

BACKGROUND

Patients with chronic heart failure (HF) frequently experience skeletal muscle weakness that limits physical function. The mechanisms underlying muscle weakness, however, have not been clearly defined.

METHODS AND RESULTS

This study examined the hypothesis that HF promotes a loss of myosin protein from single skeletal muscle fibers, which in turn reduces contractile performance. Ten patients with chronic HF and 10 controls were studied. Muscle atrophy was not evident in patients, and groups displayed similar physical activity levels, suggesting that observed differences reflect the effects of HF and not muscle atrophy or disuse. In single muscle fibers, patients with HF showed reduced myosin heavy chain protein content (P<0.05) that manifested as a reduction in functional myosin-actin cross-bridges (P<0.05). No evidence was found for a generalized loss of myofilament protein, suggesting a selective loss of myosin. Accordingly, single muscle fiber maximal Ca(2+)-activated tension was reduced in myosin heavy chain I fibers in patients (P<0.05). However, tension was maintained in myosin heavy chain IIA fibers in patients because a greater proportion of available myosin heads were bound to actin during Ca(2+) activation (P<0.01).

CONCLUSIONS

Collectively, our results show that HF alters the quantity and functionality of the myosin molecule in skeletal muscle, leading to reduced tension in myosin heavy chain I fibers. Loss of single fiber myosin protein content represents a potential molecular mechanism underlying muscle weakness and exercise limitation in patients with HF.

Reduced knee extensor function in heart failure is not explained by inactivity

BACKGROUND

The goal of this study was to determine if heart failure alters knee extensor muscle torque, power production or contractile velocity.

METHODS

Heart failure patients (n=11; 70.4±4.3 yrs) and controls (n=11; 70.3±3.4 yrs) matched for age and sex were evaluated for knee extensor contractile performance under isometric and isokinetic conditions and body composition by dual energy X-ray absorptiometry. Additionally, we recruited sedentary to minimally active elderly controls to match heart failure patients for habitual physical activity and assessed activity levels using accelerometry.

RESULTS

Groups did not differ for total or regional body composition or average daily physical activity level. Despite similar muscle size and use, heart failure patients exhibited 21-29% lower (P<0.05 to P<0.01) isometric knee extensor torque throughout a range of knee angles, 15-33% lower (P=0.05 to P<0.01) peak concentric torque measured at various isokinetic speeds and corresponding reductions (P=0.05 to P<0.01) in peak power output. Expression of peak isokinetic torque data relative to isometric torque eliminated group differences, suggesting that impaired contractile function under dynamic conditions is explained by deficits in the force generating capacity of muscle. No group differences were found in the time required to reach target velocity during isokinetic contractions, an index of contractile velocity.

CONCLUSION

Because group differences in muscle torque were independent of age, sex, physical activity level and muscle size, our results suggest that muscle contractile dysfunction in these patients is likely attributable to the heart failure syndrome.

Implications of chronic heart failure on peripheral vasculature and skeletal muscle before and after exercise training

The pathophysiology of chronic heart failure (CHF) is typically conceptualized in terms of cardiac dysfunction. However, alterations in peripheral blood flow and intrinsic skeletal muscle properties are also now recognized as mechanisms for exercise intolerance that can be modified by therapeutic exercise. This overview focuses on blood delivery, oxygen extraction and utilization that result from heart failure. Related features of inflammation, changes in skeletal muscle signaling pathways, and vulnerability to skeletal muscle atrophy are discussed. Specific focus is given to the ways in which perfusion and skeletal muscle properties affect exercise intolerance and how peripheral improvements following exercise training increase aerobic capacity. We also identify gaps in the literature that may constitute priorities for further investigation.

Skeletal muscle contractile protein function is preserved in human heart failure

Skeletal muscle weakness is a common finding in patients with chronic heart failure (CHF). This functional deficit cannot be accounted for by muscle atrophy alone, suggesting that the syndrome of heart failure induces a myopathy in the skeletal musculature. To determine whether decrements in muscle performance are related to alterations in contractile protein function, biopsies were obtained from the vastus lateralis muscle of four CHF patients and four control patients. CHF patients exhibited reduced peak aerobic capacity and knee extensor muscle strength. Decrements in whole muscle strength persisted after statistical control for muscle size. Thin filaments and myosin were isolated from biopsies and mechanically assessed using the in vitro motility assay. Isolated skeletal muscle thin-filament function, however, did not differ between CHF patients and controls with respect to unloaded shortening velocity, calcium sensitivity, or maximal force. Similarly, no difference in maximal force or unloaded shortening velocity of isolated myosin was observed between CHF patients and controls. From these results, we conclude that skeletal contractile protein function is unaltered in CHF patients. Other factors, such as a decrease in total muscle myosin content, are likely contributors to the skeletal muscle strength deficit of heart failure.

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.

Inflammation and perturbation of thel-carnitine system in heart failure

BACKGROUND

Heart failure (HF) is accompanied by elevated levels of pro-inflammatory cytokines. Skeletal muscle myopathy with atrophy of fibres, decreased oxidative metabolism and preferential synthesis of fast myosin heavy chains (MHCs) occurs, which contributes to the worsening of symptoms. l-Carnitine has been shown to be protective against the apoptosis-induced atrophy of fibres and fast MHCs shift.

AIMS

To investigate the interrelationship between TNFalpha and sphingosine (SPH), which induce muscle wastage, and plasma levels of l-carnitine.

METHODS

We studied 18 heart failure patients and correlated NYHA class and ventricular function with the plasma concentration of these molecules.

RESULTS

TNFalpha and SPH levels were raised and correlated with the severity of HF. l-Carnitine levels were increased in HF patients, but decreased according to the severity of cardiac decompensation.

CONCLUSIONS

The increased levels of l-carnitine are likely due to release from the damaged muscle, reduced urinary excretion, decreased dietary intake and liver synthesis (malnutrition). It is possible that the cytokine-induced muscle wastage is not counterbalanced by the beneficial metabolic effects of l-carnitine, the metabolism of which is profoundly perturbed in CHF. l-Carnitine supplementation may produce positive effects on the skeletal muscle, as has been shown in animal models of HF.

Central haemodynamics and peripheral muscle function during exercise in patients with chronic heart failure

In this narrative review of the current literature, we examine the central and peripheral mechanisms responsible for the exercise intolerance of chronic heart failure and highlight briefly the benefits of exercise training in the treatment of this debilitating disorder. Specifically, we identify the common finding of reduced cardiac output reserve during exercise conditions leading to decreased exercise tolerance. We also reveal that the stroke volume response to exercise varies depending on the individual patient, the presence of mitral regurgitation, and the aetiology of heart failure. Chronic heart failure patients with left ventricular systolic dysfunction appear able to use the Frank-Starling mechanism to compensate (in part) for their decreased contractile reserve. Patients with left ventricular diastolic dysfunction have normal contractile function; however, they are unable to make use of the Frank-Starling mechanism during exercise conditions. We also reveal that pericardial constraint may limit diastolic filling and exercise capacity in patients with chronic heart failure. It appears that interventions that reduce pericardial constraint and mitral regurgitation enhance diastolic filling and increase exercise tolerance. A series of peripheral muscle changes also occur, including changes in muscle mass, cellular structure, energy metabolism, and blood flow. Each of these factors is associated with decreased exercise capacity and the symptoms of chronic heart failure. Exercise training has been shown to improve both central haemodynamics and peripheral muscle function leading to improvements in exercise capacity, functional status, and overall quality of life in patients with chronic heart failure.

Why does chronic heart failure cause breathlessness and fatigue?

Traditional explanations for the symptoms of fatigue and breathlessness experienced by patients with chronic heart failure (CHF) focus on how reduced cardiac output on exercise leads to impaired skeletal muscle blood supply, thus causing fatigue, and on how the requirement for a raised left ventricular filling pressure to maintain cardiac output results in reduced pulmonary diffusion owing to interstitial edema, thus causing breathlessness. However, indices of left ventricular function relate poorly to exercise capacity and symptoms, suggesting that the origin of symptoms may lie elsewhere. There is a specific heart failure myopathy that is present early in the condition which may contribute largely to the sensation of fatigue. Receptors present in skeletal muscle sensitive to work (ergoreceptors) are overactive in patients with CHF, presumably as a consequence of the myopathy, and their activity is related both to the ventilatory response to exercise and breathlessness, and to the sympathetic overactivity of CHF. In the present paper, we review the systemic consequences of left ventricular dysfunction to understand how they relate to the symptoms of heart failure.

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 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.

The effect of moderate exercise training on skeletal muscle myosin heavy chain distribution in chronic heart failure

BACKGROUND

The myosin heavy chain (MHC) is altered in chronic heart failure (CHF), but the effect of exercise on MHC expression in CHF patients is not understood. The aim of the present study was to show the effect of aerobic exercise on MHC distribution in patients with CHF.

METHODS

Patients (n=17) with stable NYHA class I-III CHF were randomised into training and control groups. For a period of three months, the training group cycled on an ergometric cycle 3 times a week for 30 min, the control group continued as they did previously. Both a baseline and a final 3 month graded maximal exercise test and exercise endurance test with constant submaximal work load were performed. Muscle samples, obtained from vastus lateralis muscle at baseline and after 3 months from the 8 patients in the training group and the 9 in the control group, were analysed for MHC distribution using SDS-polyacrylamide gel electrophoresis.

RESULTS

Baseline MHC distributions were similar in both groups and training did not alter the MHC distribution. Exercise duration, at constant submaximal work load, improved from 14.9+/-7.1 to 26.9+/-9.6 min (p<0.01 for the change between the groups). Training did not improve peak oxygen consumption.

CONCLUSION

No correlation between the change in exercise capacity and MHC distribution appeared despite the significant improvement of exercise duration.

How Does Cardiac Resynchronization Therapy Improve Exercise Capacity in Chronic Heart Failure?

BACKGROUND

Studies have shown that neither ejection fraction nor hemodynamic abnormalities during exercise in chronic heart failure (HF) correlate with symptoms of fatigue and exhaustion. The concept that exercise limitation in patients with chronic HF is due to abnormal hemodynamics during exercise has been revised to acknowledge that the skeletal myopathy of chronic HF contributes significantly to exercise dysfunction in heart failure. Why then does cardiac resynchronization therapy (CRT), a therapy that improves abnormalities of cardiac function, such as cardiac output and ejection fraction, produce a consistent, measurable, irrefutable increase in exercise capacity?

METHODS AND RESULTS

In this review I will (1) review the mechanisms of exercise dysfunction in chronic HF, with special attention to the concept of "coordinated adaptation"; (2) analyze the effects of CRT on autonomic dysfunction in HF; and (3) propose a unifying hypothesis to understand how a therapy that improves cardiac function can improve exercise dysfunction attributable to a skeletal myopathy. Specifically, I will review evidence that CRT improves exercise capacity by attenuating the chronic sympathetic activation of HF.

CONCLUSION

The decrease in sympathetic activation, and perhaps inflammation, during CRT likely reverses many features of the skeletal myopathy, leading to improved exercise capacity.

Skeletal muscle myofibrillar mRNA expression in heart failure: relationship to local and circulating hormones

Chronic heart failure is characterized by changes in skeletal muscle that contribute to exercise intolerance and muscle weakness. To determine whether changes in the quantity and isoform distribution of key myofibrillar proteins are related to altered gene expression, we measured skeletal muscle myofibrillar mRNA abundance in nine heart failure patients (mean +/- SE; 63 +/- 3 yr) and nine controls (70 +/- 3 yr). In addition, we assessed the relationship of circulating levels of anabolic and catabolic hormones, as well as local expression of insulin-like growth factor (IGF)-I, to myofibrillar mRNA abundance. Heart failure patients were characterized by lower abundance of mRNA encoding the myosin heavy chain (MHC) I isoform (P < 0.01), whereas MHC IIa and MHC IIx mRNA did not differ between groups. Actin mRNA was also lower in heart failure patients compared with controls (P < 0.001). The expression of each MHC isoform transcript correlated with its respective protein product (MHC I: r = 0.656, P < 0.01; MHC IIa: r = 0.489, P < 0.05; MHC IIx: r = 0.505, P < 0.05; n = 18 for all). In addition to changes in myofibrillar transcripts, we found lower (P < 0.01) skeletal muscle IGF-1Ea mRNA content in heart failure patients. Myofibrillar mRNA levels were positively associated with skeletal muscle IGF-1Ea transcript levels (range of r values: 0.663-0.765; P values: <0.01 to <0.001) and modestly associated with circulating markers of immune activation (range of r values: -0.487 to -0.555; P values: <0.05 to <0.03). Our findings suggest that alterations in skeletal muscle MHC content and isoform distribution in heart failure may derive, in part, from changes in MHC gene expression. The relationships of myofibrillar mRNA content to both local and circulating hormones further suggest that alterations in the balance between anabolic and catabolic hormones in heart failure patients may influence skeletal muscle myofibrillar protein phenotype by altering gene expression.

Skeletal muscle myofibrillar protein metabolism in heart failure: relationship to immune activation and functional capacity

Chronic heart failure is characterized by changes in skeletal muscle that contribute to physical disability. Most studies to date have investigated defects in skeletal muscle oxidative capacity. In contrast, less is known about how heart failure affects myofibrillar protein metabolism. Thus we examined the effect of heart failure on skeletal muscle myofibrillar protein metabolism, with a specific emphasis on changes in myosin heavy chain (MHC) protein content, synthesis, and isoform distribution in 10 patients with heart failure (63 +/- 3 yr) and 11 controls (70 +/- 3 yr). In addition, we examined the relationship of MHC protein metabolism to inflammatory markers and physical function. Although MHC and actin protein content did not differ between groups, MHC protein content decreased with increasing disease severity in heart failure patients (r = -0.748, P < 0.02), whereas actin protein content was not related to disease severity. No difference in MHC protein synthesis was found between groups, and MHC protein synthesis rates were not related to disease severity. There were, however, relationships between C-reactive protein and both MHC protein synthesis (r = -0.442, P = 0.05) and the ratio of MHC to mixed muscle protein synthesis (r = -0.493, P < 0.03). Heart failure patients showed reduced relative amounts of MHC I (P < 0.05) and a trend toward increased MHC IIx (P = 0.06). In regression analyses, decreased MHC protein content was related to decreased exercise capacity and muscle strength in heart failure patients. Our results demonstrate that heart failure affects both the quantity and isoform distribution of skeletal muscle MHC protein. The fact that MHC protein content was related to both exercise capacity and muscle strength further suggests that quantitative alterations in MHC protein may have functional significance.

Detection of calf muscle alterations in patients with chronic heart failure by P magnetic resonance spectroscopy: Impaired adaptation to continuous exercise

Previous studies suggested that alteration of systemic skeletal muscle metabolism is a major determinant of exercise tolerance in patients with chronic heart failure (CHF). The authors examined calf muscle metabolism during continuous exercise of the foot in patients with CHF compared with normal subjects using (31)P magnetic resonance spectroscopy. The subjects were patients with New York Heart Association class II CHF who had previously suffered New York Heart Association class IV heart failure. Plantarflexion of the foot was repeated for 8 min 40 s at a rate of one contraction per second against a 2 kg load inside the magnet. At rest, during exercise (divided into the first one-half [EX1] and the latter one-half [EX2]) and at recovery, (31)P magnetic resonance spectroscopy data sets were acquired every 4 min 20 s. At rest, the phosphocreatine to hexamethylphosphoric triamide (PCr:HMPT) and the inorganic phosphate (Pi) to PCr ratios in the CHF group were not different from those in the normal group. During EX1 in the normal group, PCr levels decreased and Pi levels increased. Although exercise continued, these changes improved during EX2, suggesting there was an adaptation to exercise. The degree of change in the PCr:HMPT ratio during EX1 in the CHF group was not significantly different from that during EX1 in the normal group; however, the improvement during EX2 in the CHF group was impaired. The Pi:PCr ratio of EX1 to EX2 in the CHF group was significantly greater than that in the normal group (0.74+/-0.22 versus 0.19+/-0.05, respectively, P<0.005). Thus, in CHF, adaptation to continuous exercise may be impaired by alteration of skeletal muscle metabolism and this alteration may worsen exercise capacity.

Nutritional strategy in the management of heart failure in adults

The incidence of congestive heart failure (CHF) is increasing in Westernized countries, and patients with CHF experience poor quality of life (functional impairment, high hospitalization rate and high mortality). Malnutrition occurring during the course of CHF is referred to as cardiac cachexia and is associated with higher mortality independent of the severity of CHF. Cardiac cachexia involving a loss of more than 10% of lean body mass can clinically be defined as a bodyweight loss of 7.5% of previous dry bodyweight in a period longer than 6 months. The energy requirements of patients with CHF, whether cachectic or not, are not noticeably modified since the increase in resting energy expenditure is compensated by a decrease in physical activity energy expenditure. Malnutrition in CHF has been ascribed to neurohormonal alterations, i.e. anabolic/catabolic imbalance and increased cytokine release. Anorexia may occur, particularly during acute decompensation of CHF. Function is impaired in CHF, because of exertional dyspnea and changes in skeletal muscle. Decreased exercise endurance seems to be related to decreased mitochondrial oxidative capacities and atrophy of type 1 fibers, which are attributed to alteration in muscle perfusion and are partially reversible by training. Malnutrition could also impair muscle function, because of decreased muscle mass and strength associated with decreased glycolytic capacities and atrophy of type 2a and 2b fibres. With respect to the putative mechanisms of cardiac cachexia, anabolic therapy (hormones or nutrients) and anticytokine therapy have been proposed, but trials are scarce and often inconclusive. In surgical patients with CHF, perioperative (pre- and postoperative) nutritional support has been shown to be effective in reducing the mortality rate. Long term nutritional supplementation trials in patients with CHF and cachexia are thus required to establish recommendations for the nutritional management of patients with CHF.

Differential gene expression in skeletal muscle after induction of heart failure: impact of cytokines on protein phosphatase 2A expression

Different intrinsic alterations of skeletal muscle metabolism and gene expression have been described in chronic heart failure (CHF). As proposed skeletal muscle alterations in CHF may contribute to exercise intolerance and early muscular fatigue. However the exact molecular changes occurring in the skeletal muscle are still unclear. The aim of this study was to characterize the pattern of differential gene expression in an animal model of CHF and to study the regulation of one selected gene. Rats were subjected to LAD ligation or sham operation. mRNA was isolated from musculus quadriceps of both groups and differential gene expression was determined by subtractive hybridization. Quantitative RT-PCR and cell culture experiments were performed to further characterize the changed expression of protein phosphatase 2A (PP2A) in human skeletal muscle biopsies as well as the cytokine dependent regulation of PP2A expression. Out of 800 picked clones differential expression of 24 distinct genes could be identified by sequencing and reverse Northern blotting. PP2A expression demonstrated a significant upregulation in skeletal muscle biopsies from patients with CHF as compared to healthy controls (9.7 +/- 1.9 vs. 4.2 +/- 0.7 arbitrary units; p<0.05). Incubation of rat skeletal muscle myoblasts with a combination of TNF-alpha, IL-1beta, and gamma-IFN caused a 3-fold upregulation of PP2A expression vs. untreated cells. These results suggest that CHF is accompanied by changes in expression of genes involved in energy metabolism, contractility, and apoptosis in the skeletal muscle. The upregulation of PP2A, an important regulator in intracellular signaling and apoptosis, may be due to an increase of inflammatory cytokines.