Skeletal Muscle Abnormalities Research Articles

Apoptotic Mediators are Upregulated in the Skeletal Muscle of Chronic/Progressive Mouse Model of Parkinson's Disease.

Apoptosis has been implicated in the pathogenesis of Parkinson disease (PD). Parkinson disease is characterized by skeletal muscle abnormalities. The aim of this study is to illustrate the impact of PD induction on the expression of apoptotic mediators. Twenty normal albino mice were randomly selected and equally divided in control and PD groups. Chronic Parkinsonism was induced in the PD group using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and probenecid (MPTP/p). After that, samples from gastrocnemius muscles were evaluated by immunohistochemistry to examine the expression of p53 and active caspase-3 in the two groups of animals. P53 and active caspase-3 expression was significantly higher in gastrocnemius skeletal muscle in PD mice compared with that in the control mice (P value <0.01). Furthermore, we show PD gastrocnemius muscle atrophy measured by significant reduction (P < 0.01) in the muscle fiber cross-sectional area. Thus, our present data suggest that PD induction increased the expression of the apoptotic mediators p53 and active caspase-3 in gastrocnemius muscle, indicating the induction of apoptosis, which was correlative with gastrocnemius muscle atrophy subsequent to the induction of PD.

HDAC4-myogenin axis as an important marker of HD-related skeletal muscle atrophy.

Skeletal muscle remodelling and contractile dysfunction occur through both acute and chronic disease processes. These include the accumulation of insoluble aggregates of misfolded amyloid proteins that is a pathological feature of Huntington’s disease (HD). While HD has been described primarily as a neurological disease, HD patients’ exhibit pronounced skeletal muscle atrophy. Given that huntingtin is a ubiquitously expressed protein, skeletal muscle fibres may be at risk of a cell autonomous HD-related dysfunction. However the mechanism leading to skeletal muscle abnormalities in the clinical and pre-clinical HD settings remains unknown. To unravel this mechanism, we employed the R6/2 transgenic and HdhQ150 knock-in mouse models of HD. We found that symptomatic animals developed a progressive impairment of the contractile characteristics of the hind limb muscles tibialis anterior (TA) and extensor digitorum longus (EDL), accompanied by a significant loss of motor units in the EDL. In symptomatic animals, these pronounced functional changes were accompanied by an aberrant deregulation of contractile protein transcripts and their up-stream transcriptional regulators. In addition, HD mouse models develop a significant reduction in muscle force, possibly as a result of a deterioration in energy metabolism and decreased oxidation that is accompanied by the re-expression of the HDAC4-DACH2-myogenin axis. These results show that muscle dysfunction is a key pathological feature of HD.

Mechanisms of exercise intolerance in heart failure with preserved ejection fraction: the role of abnormal peripheral oxygen extraction.

Exercise capacity as measured by peak oxygen uptake (Vo2) is similarly impaired in patients with heart failure with preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF). However, characterization of how each component of Vo2 changes in response to incremental exercise in HFpEF versus HFrEF has not been previously defined. We hypothesized that abnormally low peripheral o2 extraction (arterio-mixed venous o2 content difference, [C(a-v)o2]) during exercise significantly contributes to impaired exercise capacity in HFpEF. We performed maximum incremental cardiopulmonary exercise testing with invasive hemodynamic monitoring on 104 patients with symptomatic NYHA II to IV heart failure (HFpEF, n=48, peak Vo2=13.9±0.5 mL kg(-1) min(-1), mean±SEM, and HFrEF, n=56, peak Vo2=12.1±0.5 mL kg(-1) min(-1)) and 24 control subjects (peak Vo2 27.0±1.7 mL kg(-1) min(-1)). Peak exercise C(a-v)o2 was lower in HFpEF compared with HFrEF (11.5±0.27 versus 13.5±0.34 mL/dL, respectively, P<0.0001), despite no differences in age, hemoglobin level, peak respiratory exchange ratio, Cao2, or cardiac filling pressures. Peak C(a-v)o2 and peak heart rate emerged as the leading predictors of peak Vo2 in HFpEF. Impaired peripheral o2 extraction was the predominant limiting factor to exercise capacity in 40% of patients with HFpEF and was closely related to elevated systemic blood pressure during exercise (r=0.49, P=0.0005). In the first study to directly measure C(a-v)o2 throughout exercise in HFpEF, HFrEF, and normals, we found that peak C(a-v)o2 was a major determinant of exercise capacity in HFpEF. The important functional limitation imposed by impaired o2 extraction may reflect intrinsic abnormalities in skeletal muscle or peripheral microvascular function, and represents a potential target for therapeutic intervention.

March 2015 at a glance.

March 2015 at a glance.

Angiotensin II can directly induce mitochondrial dysfunction, decrease oxidative fibre number and induce atrophy in mouse hindlimb skeletal muscle.

What is the central question of this study? Does angiotensinII directly induce skeletal muscle abnormalities? What is the main finding and its importance? AngiotensinII induces skeletal muscle abnormalities and reduced exercise capacity. Mitochondrial dysfunction and a decreased number of oxidative fibres are manifest early, while muscle atrophy is seen later. Thus, angiotensinII may play an important role in the skeletal muscle abnormalities observed in a wide variety of diseases. Skeletal muscle abnormalities, such as mitochondrial dysfunction, a decreased percentage of oxidative fibres and atrophy, are the main cause of reduced exercise capacity observed in ageing and various diseases, including heart failure. The renin-angiotensin system, particularly angiotensinII (AngII), is activated in the skeletal muscle in these conditions. Here, we examined whether AngII could directly induce these skeletal muscle abnormalities and investigated their time course. AngiotensinII (1000ngkg(-1) min(-1) ) or vehicle was administered to male C57BL/6J mice (10-12weeks of age) via subcutaneously implanted osmotic minipumps for 1 or 4weeks. AngiotensinII significantly decreased body and hindlimb skeletal muscle weights compared with vehicle at 4weeks. In parallel, muscle cross-sectional area was also decreased in the skeletal muscle at 4weeks. Muscle RING finger-1 and atrogin-1 were significantly increased in the skeletal muscle from mice treated with AngII. In addition, cleaved caspase-3 and terminal deoxynucleotidyl trasferase-mediated dUTP nick-positive nuclei were significantly increased in mice treated with AngII at 1 and 4weeks, respectively. Mitochondrial oxidative enzymes, such as citrate synthase, complexI and complexIII activities were significantly decreased in the skeletal muscle from mice treated AngII at 1 and 4weeks. NAD(P)H oxidase-derived superoxide production was increased. NADH staining revealed that typeI fibres were decreased and typeIIb fibres increased in mice treated with AngII at 1week. The work and running distance evaluated by a treadmill test were significantly decreased in mice treated with AngII at 4weeks. Thus, AngII could directly induce the abnormalities in skeletal muscle function and structure.

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.

Influence of N-Acetylcysteine on Oxidative Stress in Slow-Twitch Soleus Muscle of Heart Failure Rats

Background: Chronic heart failure is characterized by decreased exercise capacity with early exacerbation of fatigue and dyspnea. Intrinsic skeletal muscle abnormalities can play a role in exercise intolerance. Causal or contributing factors responsible for muscle alterations have not been completely defined. This study evaluated skeletal muscle oxidative stress and NADPH oxidase activity in rats with myocardial infarction (MI) induced heart failure. Methods and Results: Four months after MI, rats were assigned to Sham, MI-C (without treatment), and MI-NAC (treated with N-acetylcysteine) groups. Two months later, echocardiogram showed left ventricular dysfunction in MI-C; NAC attenuated diastolic dysfunction. In soleus muscle, glutathione peroxidase and superoxide dismutase activity was decreased in MI-C and unchanged by NAC. 3-nitrotyrosine was similar in MI-C and Sham, and lower in MI-NAC than MI-C. Total reactive oxygen species (ROS) production was assessed by HPLC analysis of dihydroethidium (DHE) oxidation fluorescent products. The 2-hydroxyethidium (EOH)/DHE ratio did not differ between Sham and MI-C and was higher in MI-NAC. The ethidium/DHE ratio was higher in MI-C than Sham and unchanged by NAC. NADPH oxidase activity was similar in Sham and MI-C and lower in MI-NAC. Gene expression of p47^phox was lower in MI-C than Sham. NAC decreased NOX4 and p22^phox expression. Conclusions: We corroborate the case that oxidative stress is increased in skeletal muscle of heart failure rats and show for the first time that oxidative stress is not related to increased NADPH oxidase activity.

Aerobic training attenuates nicotinic acethylcholine receptor changes in the diaphragm muscle during heart failure.

Heart failure (HF) is a progressive myopathy, with clinical signs of fatigue and limb weakness that can damage the nerve-muscle interaction, altering synaptic transmission and nicotinic acetylcholine receptors (nAChR) in neuromuscular junctions (NMJs). The diaphragm is composed of a mixed proportion of muscle fibres, and during HF, this muscle becomes slower and can alter its function. As exercise training is an accepted practice to minimise abnormalities of skeletal muscle during HF, in this study, we evaluated the hypothesis that aerobic training attenuates alterations in the expression of nAChR subunits in NMJs diaphragm during heart failure. The aim of this study was to evaluate the distribution and expression of nAChR subunits in the diaphragm muscle fibres of rats subjected to an aerobic training programme during HF. Control (Sham), control training (ShamTR), aortic stenosis (AS) and aortic stenosis training (ASTR) groups were evaluated. The expression of nAChR subunits (γ, α1, ε, β1 and δ) was determined by qRT-PCR, and NMJs were analysed using confocal microscopy. We observed increased expression of the γ, α1 and β1 subunits in the AS group compared with the ASTR group. The distribution of NMJs was modulated in these groups. HF alters the mRNA expression of nAChR subunits and the structural characteristics of diaphragm NMJs. In addition, aerobic training did not alter NMJs morphology but attenuated the alterations in heart structure and function and in nAChR subunit mRNA expression. Our findings demonstrate the beneficial effects of aerobic exercise training in maintaining the integrity of the neuromuscular system in the diaphragm muscle during HF and may be critical for non-pharmacological therapy to improve the quality of life for patients with this syndrome.

Skeletal muscle abnormalities in pulmonary arterial hypertension.

BackgroundPulmonary arterial hypertension is a progressive disease that is characterized by dyspnea and exercise intolerance. Impairment in skeletal muscle has recently been described in PAH, although the degree to which this impairment is solely determined by the hemodynamic profile remains uncertain. The aim of this study was to verify the association of structural and functional skeletal muscle characteristics with maximum exercise in PAH.MethodsThe exercise capacity, body composition, CT area of limb muscle, quality of life, quadriceps biopsy and hemodynamics of 16 PAH patients were compared with those of 10 controls.ResultsPAH patients had a significantly poorer quality of life, reduced percentage of lean body mass, reduced respiratory muscle strength, reduced resistance and strength of quadriceps and increased functional limitation at 6MWT and CPET. VO2 max was correlated with muscular variables and cardiac output. Bivariate linear regression models showed that the association between muscular structural and functional variables remained significant even after correcting for cardiac output.ConclusionOur study showed the coexistence of ventilatory and quadriceps weakness in face of exercise intolerance in the same group of PAH patients. More interestingly, it is the first time that the independent association between muscular pattern and maximum exercise capacity is evidenced in PAH, independently of cardiac index highlighting the importance of considering rehabilitation in the treatment strategy for PAH.

Abstract 16555: Angiotensin II Directly Induces Mitochondrial Dysfunction and Atrophy in the Skeletal Muscle

Background: Skeletal muscle abnormalities such as mitochondrial dysfunction, fiber type transition, and atrophy are the main cause of reduced exercise capacity observed in various diseases such as diabetes mellitus and heart failure. Renin-angiotensin system (RAS) was activated in the skeletal muscle in these conditions. We thus hypothesized that angiotensin II (Ang II) could directly induce skeletal muscle abnormalities. Methods and Results: Ang II (1000ng/kg/min, n=8) or vehicle (saline, n=8) was administrated into male C57BL/6J mice (10-12 week of age) via subcutaneously implanted osmotic minipumps for 4 weeks. Ang II significantly decreased body weight (26.6±0.3 vs. 27.6±0.3 g, p&lt;0.05) and hind limb skeletal muscle weight compared with vehicle at 4 weeks (159±2 vs. 166±2 mg, p&lt;0.05). It also decreased myocyte cross-sectional area in the skeletal muscle at 4 weeks (1869±29 vs. 2233±46 μm2, p&lt;0.05). Muscle RING finger-1 and atrogin-1, the markers of protein degradation, were significantly increased in the skeletal muscle tissue from Ang II at 4 weeks by 133% and 102%, respectively (p&lt;0.05). In addition, cleaved caspase-3 and TUNEL positive cells were significantly increased in Ang II at 4 weeks by 2.5 and 1.4-folds, respectively (p&lt;0.05). Citrate synthase (1 week, 121±4 vs. 162±9; 4 weeks, 117±7 vs. 152±4 nmol/min/mg protein), complex I (1 week, 264±27 vs. 396±30; 4 weeks, 281±21 vs. 400±30 nmol/min/mg protein) and complex III (1 week, 321±33 vs. 508±49; 4 weeks, 347±30 vs. 503±43 nmol/min/mg protein) activities were significantly decreased in mitochondria isolated from skeletal muscle from Ang II at 1 and 4 weeks (all p&lt;0.05). NADH staining revealed that type I fiber decreased by 31% and type IIb fiber increased by 38% in Ang II at 1 week. The work (16±1 vs. 27±3 J, p&lt;0.05) and run distance (359±18 vs. 589±59 m, p&lt;0.05) evaluated by treadmill test significantly decreased in Ang II at 4 weeks. An administration of Ang II for 1 week also induced mitochondrial dysfunction, fiber type shift, and protein degradation, but did not skeletal muscle atrophy. Conclusion: Ang II could directly induce the reduction of exercise tolerance in association with the abnormalities in skeletal muscle function and structure.

Angiotensin II Could Directly Induced Mitochondrial Dysfunction and Atrophy in the Skeletal Muscle

Skeletal muscle (SKM) abnormalities including mitochondrial dysfunction, transition of oxidative fiber to glycolytic fiber, apoptosis and atrophy are observed in various cardiovascular diseases such as heart failure. However, the stimulating factor for these abnormalities has not been identified. We hypothesized that angiotensin II (Ang II) could directly induce them.

Pompe disease: from pathophysiology to therapy and back again.

Pompe disease is a lysosomal storage disorder in which acid alpha-glucosidase (GAA) is deficient or absent. Deficiency of this lysosomal enzyme results in progressive expansion of glycogen-filled lysosomes in multiple tissues, with cardiac and skeletal muscle being the most severely affected. The clinical spectrum ranges from fatal hypertrophic cardiomyopathy and skeletal muscle myopathy in infants to relatively attenuated forms, which manifest as a progressive myopathy without cardiac involvement. The currently available enzyme replacement therapy (ERT) proved to be successful in reversing cardiac but not skeletal muscle abnormalities. Although the overall understanding of the disease has progressed, the pathophysiology of muscle damage remains poorly understood. Lysosomal enlargement/rupture has long been considered a mechanism of relentless muscle damage in Pompe disease. In past years, it became clear that this simple view of the pathology is inadequate; the pathological cascade involves dysfunctional autophagy, a major lysosome-dependent intracellular degradative pathway. The autophagic process in Pompe skeletal muscle is affected at the termination stage—impaired autophagosomal-lysosomal fusion. Yet another abnormality in the diseased muscle is the accelerated production of large, unrelated to ageing, lipofuscin deposits—a marker of cellular oxidative damage and a sign of mitochondrial dysfunction. The massive autophagic buildup and lipofuscin inclusions appear to cause a greater effect on muscle architecture than the enlarged lysosomes outside the autophagic regions. Furthermore, the dysfunctional autophagy affects the trafficking of the replacement enzyme and interferes with its delivery to the lysosomes. Several new therapeutic approaches have been tested in Pompe mouse models: substrate reduction therapy, lysosomal exocytosis following the overexpression of transcription factor EB and a closely related but distinct factor E3, and genetic manipulation of autophagy.

ZBTB42 mutation defines a novel lethal congenital contracture syndrome (LCCS6).

Lethal congenital contracture syndrome (LCCS) is a lethal autosomal recessive form of arthrogryposis multiplex congenita (AMC). LCCS is genetically heterogeneous with mutations in five genes identified to date, all with a role in the innervation or contractile apparatus of skeletal muscles. In a consanguineous Saudi family with multiple stillbirths presenting with LCCS, we excluded linkage to all known LCCS loci and combined autozygome analysis and whole-exome sequencing to identify a novel homozygous variant in ZBTB42, which had been shown to be enriched in skeletal muscles, especially at the neuromuscular junction. Knockdown experiments of zbtb42 in zebrafish consistently resulted in grossly abnormal skeletal muscle development and myofibrillar disorganization at the microscopic level. This severe muscular phenotype is successfully rescued with overexpression of the human wild-type ZBTB42 gene, but not with the mutant form of ZBTB42 that models the human missense change. Our data assign a novel muscular developmental phenotype to ZBTB42 in vertebrates and establish a new LCCS6 type caused by ZBTB42 mutation.

Skeletal muscle proteomic signature in pulmonary arterial hypertension (1158.8)

Introduction: Pulmonary arterial hypertension (PAH) is characterized by a progressive increase in pulmonary vascular resistance leading to right ventricular (RV) hypertrophy and ultimately failure. Numerous observations suggest that exercise limitation in pulmonary arterial hypertension (PAH) is not solely due to cardio‐pulmonary impairment, but that other determinants such as skeletal muscle abnormalities are involved. To better understand the exercise limitation origins in PAH, we studied the proteomic signature of skeletal muscle impairment in idiopathic PAH (iPAH) patients.Methods and results: Muscle proteins from 4 iPAH patients and 4 sex and age matched controls were extracted following quadriceps muscle biopsy. Fractioned peptides were then tagged using isobaric Tags for Relative and Absolute Quantitation (iTRAQ, ABsciex) specific for each patient. Tagged peptides were then mixed, fractioned, identified and quantified using mass spectrometry quantitative method. Over 900 proteins were identified, among them, 9 were under‐expressed and 7 were over‐expressed in all iPAH patient quadriceps. More than 75% of the under‐expressed proteins are involved in oxidative metabolism and most other highlighted proteins play a role in myogenesis. These findings were structurally associated with decreased mitochondrial density (citrate synthase assay) and impaired mitochondrial structure measured by electronic microscopy, while muscle fibers distribution was unchanged. Functionally, all these abnormalities resulted in decreases in oxidative metabolism (pyruvate dehydrogenases assay).Conclusions: For the first time in humans, we provide evidences that, as in lungs and the right ventricle, the impaired mitochondrial metabolism is also present in skeletal muscle suggesting that PAH might be considered as a global mitochondrial/metabolic disease.

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.

The H19 long noncoding RNA gives rise to microRNAs miR-675-3p and miR-675-5p to promote skeletal muscle differentiation and regeneration

Regulated expression of the H19 long noncoding RNA gene has been well characterized as a paradigm for genomic imprinting, but the H19 RNA's biological function remains largely unclear. H19 is abundantly expressed maternally in embryonic tissues but is strongly repressed after birth, and significant transcription persists only in skeletal muscle. Thus, we examined the role of the H19 RNA in skeletal muscle differentiation and regeneration. Knockdown of H19 RNA in myoblast cells and H19 knockout mouse satellite cells decreases differentiation. H19 exon1 encodes two conserved microRNAs, miR-675-3p and miR-675-5p, both of which are induced during skeletal muscle differentiation. The inhibition of myogenesis by H19 depletion during myoblast differentiation is rescued by exogenous expression of miR-675-3p and miR-675-5p. H19-deficient mice display abnormal skeletal muscle regeneration after injury, which is rectified by reintroduction of miR-675-3p and miR-675-5p. miR-675-3p and miR-675-5p function by directly targeting and down-regulating the anti-differentiation Smad transcription factors critical for the bone morphogenetic protein (BMP) pathway and the DNA replication initiation factor Cdc6. Therefore, the H19 long noncoding RNA has a critical trans-regulatory function in skeletal muscle differentiation and regeneration that is mediated by the microRNAs encoded within H19.

Extracellular Superoxide Dismutase Ameliorates Skeletal Muscle Abnormalities, Cachexia, and Exercise Intolerance in Mice with Congestive Heart Failure

Congestive heart failure (CHF) is a leading cause of morbidity and mortality, and oxidative stress has been implicated in the pathogenesis of cachexia (muscle wasting) and the hallmark symptom, exercise intolerance. We have previously shown that a nitric oxide-dependent antioxidant defense renders oxidative skeletal muscle resistant to catabolic wasting. Here, we aimed to identify and determine the functional role of nitric oxide-inducible antioxidant enzyme(s) in protection against cardiac cachexia and exercise intolerance in CHF. We demonstrated that systemic administration of endogenous nitric oxide donor S-nitrosoglutathione in mice blocked the reduction of extracellular superoxide dismutase (EcSOD) protein expression, as well as the induction of MAFbx/Atrogin-1 mRNA expression and muscle atrophy induced by glucocorticoid. We further showed that endogenous EcSOD, expressed primarily by type IId/x and IIa myofibers and enriched at endothelial cells, is induced by exercise training. Muscle-specific overexpression of EcSOD by somatic gene transfer or transgenesis (muscle creatine kinase [MCK]-EcSOD) in mice significantly attenuated muscle atrophy. Importantly, when crossbred into a mouse genetic model of CHF (α-myosin heavy chain-calsequestrin), MCK-EcSOD transgenic mice had significant attenuation of cachexia with preserved whole body muscle strength and endurance capacity in the absence of reduced HF. Enhanced EcSOD expression significantly ameliorated CHF-induced oxidative stress, MAFbx/Atrogin-1 mRNA expression, loss of mitochondria, and vascular rarefaction in skeletal muscle. EcSOD plays an important antioxidant defense function in skeletal muscle against cardiac cachexia and exercise intolerance in CHF.

Dynamic expression of molecules that control limb muscle development including Fhl1 in hind limbs of different gestational age

Muscle abnormality could be a key reason for congenital clubfoot (CCF) deformity, which manifests itself during fetal development. FHL1 down-regulated expression is involved in the formation of skeletal muscle abnormalities in CCF and FHL1 gene mutations contribute to the development of some kinds of myopathies. Therefore, detecting dynamic expression of Fhl1 and other molecules (Hgf, MyoD1, Myogenin, and Myh4) that control limb muscle development in hind limbs of different gestational age will provide a foundation for further research on the molecular mechanism involves in the myopathies or CCF. The dynamic gene expression levels of Fhl1, Hgf, MyoD1, Myogenin, and Myh4 in the lower limbs of E16, E17, E19, and E20 rat embryos were examined by real-time RT-PCR. Immunofluorescence was used to detect formation of specific muscle fibers (fast or slow fibers) in distal E17 hind limbs. The expression levels of Fhl1, Hgf, MyoD1, Myogenin, and Myh4 were varying in hind limbs of different gestational age. Real-time PCR results showed that all the genes that control skeletal muscle development except for Fhl1 exhibited a peak in E17 lower limbs. Immunofluorescence results showed obviously positive fast-myosin in the distal E17 lower limbs and meanwhile slow-myosin had no apparently signals. E17 was a critical time point for terminal skeletal muscle differentiation in the lower limbs of rat embryos.

Nicotine in Combination With a High-Fat Diet Causes Intramyocellular Mitochondrial Abnormalities in Male Mice

Smoking is a major risk factor for diabetes, cardiovascular disease, and nonalcoholic fatty liver disease. The health risk associated with smoking can be exaggerated by obesity. We hypothesize that nicotine when combined with a high-fat diet (HFD) can also cause ectopic lipid accumulation in skeletal muscle, similar to recently observed hepatic steatosis. Adult C57BL6 male mice were fed a normal chow diet or HFD and received twice-daily ip injections of nicotine (0.75 mg/kg body weight) or saline for 10 weeks. Transmission electron microscopy of the gastrocnemius muscle revealed substantial intramyocellular lipid accumulation in close association with intramyofibrillar mitochondria along with intramyofibrillar mitochondrial swelling and vacuolization in nicotine-treated mice on an HFD compared with mice on an HFD treated with saline. These abnormalities were reversed by acipimox, an inhibitor of lipolysis. Mechanistically, the detrimental effect of nicotine plus HFD on skeletal muscle was associated with significantly increased oxidative stress, plasma free fatty acid, and muscle triglyceride levels coupled with inactivation of AMP-activated protein kinase and activation of its downstream target, acetyl-coenzyme A-carboxylase. We conclude that 1) greater oxidative stress together with inactivation of AMP-activated protein kinase mediates the effect of nicotine on skeletal muscle abnormalities in diet-induced obesity and 2) adipose tissue lipolysis is an important contributor of muscle steatosis and mitochondrial abnormalities.

Prevalence and correlates of osteoporosis in chronic obstructive pulmonary disease patients in India.

Background:Chronic obstructive pulmonary disease (COPD) is a syndrome of progressive airflow limitation caused by the abnormal inflammatory reaction of the airway and lung parenchyma. Osteoporosis is one of the major extrapulmonary manifestations of COPD. The, prevalence of osteoporosis in COPD patients in Indian population is unknown.Objectives:To study the prevalence of osteoporosis in COPD and to define various risk factors associated with reduced bone mineral density (BMD) in COPD.Materials and Methods:The study was done in the department of Pulmonary Medicine of a tertiary care hospital. All the diagnosed cases of COPD according to the Global Initiative for Obstructive Lung Disease (GOLD) guidelines were included in this study. The present study was a prospective study in for a period of 1 year. A brief history of the patients was taken, especially regarding duration of illness, number of exacerbations in the past 3 years, smoking in pack years, and history of steroid use (both systemic and inhaled steroids) after which cumulative dose of steroids was calculated. Spirometry was done in all these patients to stage the severity of COPD according to GOLD criteria. DEXA scan of the lumbar spine was done using bone densitometer to determine osteoporosis. A world Health Organization (WHO) criterion for definition of osteoporosis was applied and patients with T-score of > –2.5 standard deviation (SD) were diagnosed to have osteoporosis, –1 SD to –2.5 SD were diagnosed to have osteopenia and < –1 SD as normal. Statistical analysis for association of COPD with osteoporosis was done using chi-square test. Risk factors for osteoporosis were identified by univariate and multivariate logistic regression analysis.Results:A total of 102 COPD patients were included in the study. Among these, 68 patients (66.6%) had osteoporosis and 20 patients (19.6%) had osteopenia. Majority (64.7%) of the patients who had osteoporosis had stage III and stage IV COPD disease. It was observed that as the severity grade of COPD increased, the risk of osteoporosis also increased. The bone mineral density (BMD) showed a significant difference among different stages of COPD. As the severity of the stage of COPD increased, BMD decreased. It was also observed that patients with lower body mass index (BMI) had higher prevalence of osteoporosis (37.3%) as compared to overweight patients. On univariate analysis, it was observed that risk factors for osteoporosis were female sex, higher number of exacerbations, BMI, and severity of COPD. After using multivariate logistic regression analysis, stage IV COPD (odds ratio (OR): 34.48, 95% confidence interval (CI): 1.59–1,000, P < 0.02), number of acute exacerbations >3 (OR: 30.3, 95% CI: 4.74–200, P < 0.01), and steroid cumulative dose >1,000 mg (OR: 7.35, 95% CI: 0.92–58.5, P < 0.04) were observed to be significant risk factors for osteoporosis in COPD patients.Conclusions:In the present study, the prevalence of osteoporosis was 66.6% and another 19.6% had osteopenia. As the severity of COPD increased, the risk of osteoporosis increased. GOLD stage III and stage IV patient had significantly lower BMD as compared to stage I and stage II of COPD disease. Stage IV COPD disease, use of oral or parenteral glucocorticoids, and repeated number of exacerbations were found to be independent risk factors for osteoporosis in COPD patients. Thus, high clinical suspicion and early diagnosis and treatment is required in the evaluation of osteoporosis in COPD patients so that the quality of life can be improved in these patients.