Muscle atrophy in chronic obstructive pulmonary disease: molecular basis and potential therapeutic targets

Intensive care unit-acquired weakness - preventive, and therapeutic aspects; future directions and special focus on lung transplantation

In this editorial, comments are made on an interesting article in the recent issue of the World Journal of Clinical Cases by Wang and Long. The authors describe the use of neural network model to identify risk factors for the development of intensive care unit (ICU)-acquired weakness. This condition has now become common with an increasing number of patients treated in ICUs and continues to be a source of morbidity and mortality. Despite identification of certain risk factors and corrective measures thereof, lacunae still exist in our understanding of this clinical entity. Numerous possible pathogenetic mechanisms at a molecular level have been described and these continue to be increasing. The amount of retrievable data for analysis from the ICU patients for study can be huge and enormous. Machine learning techniques to identify patterns in vast amounts of data are well known and may well provide pointers to bridge the knowledge gap in this condition. This editorial discusses the current knowledge of the condition including pathogenesis, diagnosis, risk factors, preventive measures, and therapy. Furthermore, it looks specifically at ICU acquired weakness in recipients of lung transplantation, because - unlike other solid organ transplants- muscular strength plays a vital role in the preservation and survival of the transplanted lung. Lungs differ from other solid organ transplants in that the proper function of the allograft is dependent on muscle function. Muscular weakness especially diaphragmatic weakness may lead to prolonged ventilation which has deleterious effects on the transplanted lung - ranging from ventilator associated pneumonia to bronchial anastomotic complications due to prolonged positive pressure on the anastomosis.

Effects of whole-body vibration exercise on functional capacity, muscle strength, and quality of life in individuals with severe chronic obstructive pulmonary disease: a systematic review and meta-analysis

BACKGROUND

Whole body vibration (WBV) exercise is a therapy used for individuals with low tolerance to conventional exercises, such as patients with chronic obstructive pulmonary disease (COPD). This study aimed to assess the impact of WBV exercise on the functional capacity, muscle strength, and health-related quality of life (HRQoL) in severe COPD patients.

METHODS

Studies published until March 2024 were reviewed, encompassing randomized clinical trials (RCTs) without temporal or linguistic constraints, comparing WBV exercise with other interventions. The PubMed/MEDLINE, Scopus, Cochrane Airways Trials Register, and CINAHL databases were queried. The Revised Cochrane risk-of-bias tool for randomized trials 2.0A was employed for quality assessment.

RESULTS

Among 351 screened studies, 7 met the criteria, totaling 356 participants (WBV group, n = 182; control group, n = 174). Meta-analysis revealed a significant mean difference of 41.36 m [95%CI (13.28-69.44); p = .004] in the 6-minute walk test distance favoring the WBV group for functional capacity. Lower limb muscle strength improved in 57.14% of included studies. HRQoL meta-analysis demonstrated a 1.13-point difference [95%CI -1.24-3.51; p = .35] favoring WBV, although group differences were not significant. A mean difference of 2.31 points favored the control group in health condition [95%CI (-1.32-5.94); p = .021].

CONCLUSION

WBV exercise is recognized as a promising therapeutic modality for severe COPD patients, notably enhancing functional capacity. Although heterogeneous study protocols weaken the evidence for clinically relevant outcomes, improvements in lower limb muscle strength and HRQoL were also observed, differences between groups were not significant.

Pulmonary Rehabilitation: Mechanisms of Functional Loss and Benefits of Exercise

Exercise limitation is a characteristic feature of chronic respiratory diseases such as COPD and is associated with poor outcomes including decreased functional status and health-related quality of life and increased mortality. The mechanisms responsible for exercise limitation are complex and include ventilatory limitation, cardiovascular impairment, and skeletal muscle dysfunction. In addition, comorbidities such as cardiovascular disease are common in this population and can further impact exercise capacity. Exercise training, a core component of pulmonary rehabilitation, improves exercise capacity by addressing many of these mechanisms that, in turn, can potentially slow the decline of lung function, reduce the frequency of exacerbations, and decrease mortality. This article will discuss the mechanisms of exercise limitation in individuals with chronic respiratory disease, primarily focusing on COPD, and provide an overview of exercise training and its benefits in this patient population.

The short- and long-term effects of lower limb endurance training on outpatients with chronic obstructive pulmonary disease

OBJECTIVE

To explore the short- and long-term effects of lower-limb endurance training on chronic obstructive pulmonary disease outpatients.

DESIGN

Prospective quasi-experimental study.

SETTING

1383-bed teaching hospital in Taiwan.

PARTICIPANTS

Overall, 69 outpatients diagnosed with chronic obstructive pulmonary disease were enrolled. A total of 60 patients completed the study.

INTERVENTION

Training group: Lower-limb endurance training; control group: Education only.

MAIN MEASURES

The modified medical research council score, chronic obstructive pulmonary disease assessment test score, pulmonary function test, and number of acute exacerbation within a year.

RESULTS

The training group showed significant improvement in the chronic obstructive pulmonary disease assessment test total score, modified medical research council score (both P < 0.001) at third month sustaining to 12th month (P < 0.001) and presented less events of acute exacerbation (P = 0.011) at 12th month. The chronic obstructive pulmonary disease assessment test decreased by 8 points sustaining to 12th month. The training group presented significant post-training functional capacity improvements in 6-min walking distance, lowest oxygen saturation during 6-min walking test, peak workload, maximum inspiratory/ expiratory pressures, and calf circumference.

CONCLUSIONS

The lower-limb endurance training improved perceived dyspnea in daily activity and health status after completion of training and sustaining for a year. The lower-limb endurance training alleviated disease impacted on reduced acute exacerbations.

Oral corticosteroid use and sarcopenia-related traits in older people with chronic airway disease: a population-based study

Background

Sarcopenia is characterised by two major phenotypic components: low handgrip strength (HGS) and appendicular skeletal muscle index (ASMI). Oral corticosteroid (OCS) use is an important medication for acute respiratory exacerbations in patients with COPD and asthma. However, the association of OCS and sarcopenia components in older people is largely unexplored. The aim of this study was to examine the association between OCS use and HGS or ASMI in the general population and explore interactions with chronic airway diseases.

Methods

From the population-based Rotterdam Study, 5054 participants (age 69.0±8.8 years; 56% females) were included in the cross-sectional analysis and 1324 in the longitudinal analysis. Associations between OCS and muscle strength and mass were analysed using linear regression models adjusted for age, sex, fat %, height, kidney function, smoking and comorbidities.

Results

At baseline, ever-OCS users had lower handgrip strength (β= -0.48, 95% CI -0.84- -0.12) than never-OCS users, with cumulative frequency (≥10 OCS prescriptions)-dependent effects (β= -1.25, 95% CI -2.16- -0.33). COPD ever-OCS users, but not asthma, had lower handgrip strength (β= -0.98, 95% CI -1.91- -0.06) and lower lean mass (β= -0.14, 95% CI -0.27- -0.01) than never-OCS users. After 5.6 years of follow-up in those free of sarcopenia traits at baseline, COPD ever-OCS users developed lower handgrip strength (β= -1.64, 95% CI -2.87- -0.40) with frequency (β= -3.64, 95% CI -6.57- -0.72) and duration (β= -1.51, 95% CI -2.87- -0.15) association compared to never-OCS users.

Conclusions

OCS use is associated with a decline in handgrip strength in people with COPD in a cumulative frequency and duration-dependent manner. Routine muscle examination may be necessary for patients with COPD.

Characterization of a spontaneous mouse model of mild, accelerated aging via ECM degradation in emphysematous lungs

Emphysema limits airflow and causes irreversible progression of chronic obstructive pulmonary disease (COPD). Strain differences must be considered when selecting mouse models of COPD, owing to disease complexity. We previously reported that a novel C57BL/6JJcl substrain, the Mayumi-Emphysema (ME) mouse, exhibits spontaneous emphysema; however, the other characteristics remain unknown. We aimed to characterize the lungs of ME mice and determine their experimental availability as a model. ME mice had a lower body weight than the control C57BL/6JJcl mice, with a median survival time of ~80 weeks. ME mice developed diffused emphysema with respiratory dysfunction from 8 to 26 weeks of age, but did not develop bronchial wall thickening. Proteomic analyses revealed five extracellular matrix-related clusters in downregulated lung proteins in ME mice. Moreover, EFEMP2/fibulin-4, an essential extracellular matrix protein, was the most downregulated protein in the lungs of ME mice. Murine and human EFEMP2 were detected in the pulmonary artery. Furthermore, patients with mild COPD showed decreased EFEMP2 levels in the pulmonary artery when compared to those without COPD. The ME mouse is a model of mild, accelerated aging with low-inflammatory emphysema and respiratory dysfunction that progresses with age and pulmonary EFEMP2 decrease, similar to that observed in patients with mild COPD.

Efficacy of Traditional Chinese exercise (Baduanjin) on patients with stable COPD: A Systematic review and Meta-analysis

BACKGROUND

COPD is a prevalent and intractable chronic airway disease. At present, COPD is one of the diseases with the highest morbidity and mortality in the world; and causes a significant economic burden to patients and society. As a traditional exercise, the Baduanjin exercise has been inherited in China for hundreds of years. However, the treatment effects of Baduanjin exercise are controversial. This systematic review was designed to evaluate the efficacy of Baduanjin exercise in patients with stable chronic obstructive pulmonary disease.

METHODS

Published articles were searched in nine English and Chinese databases from inception to December, 2022. Two investigators conducted study selection and data extraction independently. Review Manager software 5.4 were implemented for data synthesis and analysis. Quality assessment for each study was based on the modified PEDro scale.

RESULTS

This review included 41 studies with 3,835 participants with stable COPD. Compared with the control group, the pooled data of Baduanjin exercise group showed significant improvements in the following outcomes (mean difference, 95% confidence interval): FVC (0.29, 0.25-0.33), FEV1 (0.27, 0.22-0.33), FEV1% (5.38, 4.38-6.39), FEV1/FVC (5.16, 4.48-5.84), 6MWD (38.57, 35.63-41.51), CAT (-2.30, -2.89 to -1.70), mMRC (-0.57, -0.66 to -0.48), SGRQ (-8.80, -12.75 to -4.86), HAMA (-7.39, -8.77 to -6.01), HAMD (-7.80, -9.24 to -6.37), SF-36 (8.63, 6.31-10.95).

CONCLUSIONS

Baduanjin exercise may have the potential to enhance lung function, exercise capacity, health status, mental status, and quality of life for patients with stable COPD.

ETHIC AND DISSEMINATION

This study is a systematic review and it does not involve harming the rights of participants. Ethical approval will not be required for this study. The research results may be published in a peer-reviewed journal.

Effects of a Single Session of Systemic Vibratory Therapy on Flexibility, Perception of Exertion and Handgrip Strength in Chronic Obstructive Pulmonary Disease Individuals: A Quasi-Experimental Clinical Trial

BACKGROUND

Whole-body vibration exercises (WBVE), that are generated in systemic vibratory therapy (SVT), may benefit individuals with chronic obstructive pulmonary disease (COPD). This study evaluated acute effects of SVT on the flexibility, on the perception of exertion to perform the anterior trunk flexion (ATF), and on the handgrip strength (HG).

METHODS

Thirty-eight individuals, separated into two groups, performed a single session of SVT (five bouts, 25 Hz, 2.5 of amplitude) on a side-alternating vibrating platform (SAVP), in two postures: sitting (Sitting group-SitG, n = 21) or standing (Stand group-StandG, n = 17). In both positions, the feet were on the base of the SAVP. The HG and the AFT were performed before and after the session, and the perception of effort (RPE) was measured during the ATF.

RESULTS

The ATF in the SitG (p ≤ 0.05) and in the StandG (p ≤ 0.05) was significantly improved, but in the comparison between both groups, no significant reduction was found (p = 0.14). The RPE was not influenced by the session. A significant increase of the HG in StandG post session (33.49 ± 10.30 kgf) p = 0.03 was found, but not in the SitG (p = 0.12) or between the two groups (p = 0.55).

CONCLUSIONS

SVT, in a single acute session, would be capable of promoting some functional benefits for the COPD individuals without altering the perception of exertion to perform the ATF.

TRIAL REGISTRATION

49219115.3.0000.5259, RBR-72dqtm.

Total Hip Arthroplasty in Patients Who Have Respiratory Disease Who use Supplemental Home Oxygen

BACKGROUND

The purpose of this study is to investigate the association between supplemental home oxygen prior to surgery and both medical and surgical complications after primary elective total hip arthroplasty (THA) in patients who have respiratory disease (RD).

METHODS

The Mariner database was used to identify patients who have RD who received primary elective THA from 2010 to 2020. The THA patient cohorts consisted of 20,872 patients who had RD prescribed home oxygen and 69,520 patients who had RD without home oxygen. For patients who had a diagnosis of RD and were prescribed supplemental home oxygen (O2) and those who were not, the rates of postoperative medical and surgical complications, hospital readmissions, and emergency room visits were determined. Reimbursements and lengths of stay were also determined. Logistic regression analyses were utilized to compare both cohorts to matched cohorts without RD, as well as to each other directly.

RESULTS

In comparison to the matched control group, the RD with home oxygen group had a significantly higher rate of pneumonia (odds ratio [OR] 4.27, P < .0001), pulmonary embolism (OR 1.81, P < .0001), periprosthetic joint infection (OR 1.21, P < .0001), and periprosthetic fracture (OR 1.81, P = .001). The RD with home oxygen cohort also had a significantly higher incidence of pneumonia (OR 2.16, P < .0001), periprosthetic joint infection (OR 1.38, P < .0001), and periprosthetic fracture (OR 1.24, P = .009) compared to RD patients who did not have home oxygen.

CONCLUSION

Supplemental home oxygen use prior to surgery is associated with a significantly higher risk of postoperative medical and surgical complications after elective THA.

Serum transthyretin and aminotransferases are associated with lean mass in people with coronary heart disease: Further insights from the CARE-CR study

Background

Low muscle mass disproportionately affects people with coronary heart disease compared to healthy controls but is under-researched and insufficiently treated. Inflammation, poor nutrition, and neural decline might contribute to low muscle mass. This study aimed to assess circulatory biomarkers related to these mechanisms [albumin, transthyretin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and C-terminal agrin fragment] and their relationship with muscle mass in people with coronary heart disease. Our findings could be beneficial to indicate mechanisms of sarcopenia, detect sarcopenia, and evaluate treatment.

Methods

Serum blood samples from people with coronary heart disease were analysed for biomarker concentrations using enzyme-linked immunosorbent assays. Skeletal muscle mass was estimated using dual X-ray absorptiometry derived appendicular lean mass and reported as skeletal muscle index (SMI; kg m^-2), and as a proportion of total body mass [appendicular skeletal mass (ASM%)]. Low muscle mass was defined as a SMI <7.0 and <6.0 kg m^-2, or ASM% <25.72 and <19.43% for men and women, respectively. Associations between biomarkers and lean mass were adjusted for age and inflammation.

Results

Sixty-four people were assessed; 14 (21.9%) had low muscle mass. People with low muscle mass had lower transthyretin (effect size 0.34, p = 0.007), ALT (effect size 0.34, p = 0.008), and AST (effect size 0.26, p = 0.037) concentrations, compared to those with normal muscle mass. SMI was associated with inflammation-corrected ALT (r = 0.261, p = 0.039) and with inflammation- and age-adjusted AST/ALT ratio (r = -0.257, p = 0.044). Albumin and C-terminal agrin fragment were not associated with muscle mass indices.

Conclusion

Circulatory transthyretin, ALT and AST were associated with low muscle mass in people with coronary heart disease. Low concentrations of these biomarkers might indicate that low muscle mass is partially explained by poor nutrition and high inflammation in this cohort. Targeted treatments to address these factors could be considered for people with coronary heart disease.

The role of muscle-specific MicroRNAs in patients with chronic obstructive pulmonary disease and skeletal muscle dysfunction

Skeletal muscle dysfunction is a systematic manifestation of chronic obstructive pulmonary disease (COPD), which is manifested through the changes in the respiratory and peripheral muscle fiber types, reducing muscle strength and endurance, and muscle atrophy. Muscle dysfunction limits the daily mobility, negatively affects the quality of life, and may increase the patient’s risk of mortality. MicroRNAs (miRNAs) as the regulators of gene expression, plays an important role in modulating skeletal muscle dysfunction in COPD by regulating skeletal muscle development (proliferation, differentiation), protein synthesis and degradation, inflammatory response, and metabolism. In particular, muscle-specific miRNAs (myomiRs) may play an important role in this process, although the different expression levels of myomiRs in COPD and skeletal muscle dysfunction and the mechanisms underlying their role remain unclear. In this paper, we review the differential expression of the myomiRs in COPD to identify myomiRs that play a role in skeletal muscle dysfunction in COPD. We further explore their possible mechanisms and action in order to provide new ideas for the prevention and treatment of the skeletal muscle dysfunction in COPD.

Updated Perspectives on the Role of Biomechanics in COPD: Considerations for the Clinician

Patients with chronic obstructive pulmonary disease (COPD) demonstrate extra-pulmonary functional decline such as an increased prevalence of falls. Biomechanics offers insight into functional decline by examining mechanics of abnormal movement patterns. This review discusses biomechanics of functional outcomes, muscle mechanics, and breathing mechanics in patients with COPD as well as future directions and clinical perspectives. Patients with COPD demonstrate changes in their postural sway during quiet standing compared to controls, and these deficits are exacerbated when sensory information (eg, eyes closed) is manipulated. If standing balance is disrupted with a perturbation, patients with COPD are slower to return to baseline and their muscle activity is differential from controls. When walking, patients with COPD appear to adopt a gait pattern that may increase stability (eg, shorter and wider steps, decreased gait speed) in addition to altered gait variability. Biomechanical muscle mechanics (ie, tension, extensibility, elasticity, and irritability) alterations with COPD are not well documented, with relatively few articles investigating these properties. On the other hand, dyssynchronous motion of the abdomen and rib cage while breathing is well documented in patients with COPD. Newer biomechanical technologies have allowed for estimation of regional, compartmental, lung volumes during activity such as exercise, as well as respiratory muscle activation during breathing. Future directions of biomechanical analyses in COPD are trending toward wearable sensors, big data, and cloud computing. Each of these offers unique opportunities as well as challenges. Advanced analytics of sensor data can offer insight into the health of a system by quantifying complexity or fluctuations in patterns of movement, as healthy systems demonstrate flexibility and are thus adaptable to changing conditions. Biomechanics may offer clinical utility in prediction of 30-day readmissions, identifying disease severity, and patient monitoring. Biomechanics is complementary to other assessments, capturing what patients do, as well as their capability.

Influence of COPD systemic environment on the myogenic function of muscle precursor cells in vitro

Background:

Loss of muscle mass and function are well-recognized systemic manifestations of chronic obstructive pulmonary disease (COPD). Acute exacerbations, in turn, significantly contribute to upgrade these systemic comorbidities. Involvement of myogenic precursors in muscle mass maintenance and recovery is poorly understood. The aim of the present study was to investigate the effects of the vascular systemic environment from stable and exacerbated COPD patients on the myogenic behavior of human muscle precursor cells (MPC) in vitro.

Methods:

Serum from healthy controls and from stable and exacerbated COPD patients (before and after Methylprednisolone treatment) was used to stimulate human MPC cultures. Proliferation analysis was assessed through BrdU incorporation assays. MPC differentiation was examined through real-time RT-PCR, western blot and immunofluorescence analysis.

Results:

Stimulation of MPCs with serum obtained from stable COPD patients did not affect myogenic precursor cell function. The vascular systemic environment during an acute exacerbation exerted a mitotic effect on MPCs without altering myogenic differentiation outcome. After Methylprednisolone treatment of acute exacerbated COPD patients, however, the mitotic effect was further amplified, but it was followed by a deficient differentiation capacity. Moreover, these effects were prevented when cells were co-treated with the glucocorticoid receptor antagonist Mifepristone.

Conclusion:

Our findings suggest that MPC capacity is inherently preserved in COPD patients, but is compromised after systemic administration of MP. This finding strengthens the concept that glucocorticoid treatment over the long term can negatively impact myogenic stem cell fate decisions and interfere with muscle mass recovery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02203-6.

Inflammation: Roles in Skeletal Muscle Atrophy

Various diseases can cause skeletal muscle atrophy, usually accompanied by inflammation, mitochondrial dysfunction, apoptosis, decreased protein synthesis, and enhanced proteolysis. The underlying mechanism of inflammation in skeletal muscle atrophy is extremely complex and has not been fully elucidated, thus hindering the development of effective therapeutic drugs and preventive measures for skeletal muscle atrophy. In this review, we elaborate on protein degradation pathways, including the ubiquitin-proteasome system (UPS), the autophagy-lysosome pathway (ALP), the calpain and caspase pathways, the insulin growth factor 1/Akt protein synthesis pathway, myostatin, and muscle satellite cells, in the process of muscle atrophy. Under an inflammatory environment, various pro-inflammatory cytokines directly act on nuclear factor-κB, p38MAPK, and JAK/STAT pathways through the corresponding receptors, and then are involved in muscle atrophy. Inflammation can also indirectly trigger skeletal muscle atrophy by changing the metabolic state of other tissues or cells. This paper explores the changes in the hypothalamic-pituitary-adrenal axis and fat metabolism under inflammatory conditions as well as their effects on skeletal muscle. Moreover, this paper also reviews various signaling pathways related to muscle atrophy under inflammatory conditions, such as cachexia, sepsis, type 2 diabetes mellitus, obesity, chronic obstructive pulmonary disease, chronic kidney disease, and nerve injury. Finally, this paper summarizes anti-amyotrophic drugs and their therapeutic targets for inflammation in recent years. Overall, inflammation is a key factor causing skeletal muscle atrophy, and anti-inflammation might be an effective strategy for the treatment of skeletal muscle atrophy. Various inflammatory factors and their downstream pathways are considered promising targets for the treatment and prevention of skeletal muscle atrophy.

Role of progression of training volume on intramuscular adaptations in patients with chronic obstructive pulmonary disease

Introduction: Quadriceps dysfunction is a common systemic manifestation of chronic obstructive pulmonary disease (COPD), for which treatment using resistance training is highly recommended. Even though training volume is suggested to be a key explanatory factor for intramuscular adaptation to resistance training in healthy older adults, knowledge is scarce on the role of progression of training volume for intramuscular adaptations in COPD.

Methods: This study was a sub-analysis of a parallel-group randomized controlled trial. Thirteen patients with severe to very severe COPD (median 66 yrs, forced expiratory volume in 1 s 44% predicted) performed 8 weeks of low-load resistance training. In a post hoc analysis, they were divided into two groups according to their training volume progression. Those in whom training volume continued to increase after the first 4 weeks of training outlined the continued progression group (n = 9), while those with limited increase (<5%) or even reduction in training volume after the initial 4 weeks composed the discontinued progression group (n = 4). Fiber-type distribution and oxidative muscle protein levels, i.e., citrate synthase (CS), hydroxyacyl-coenzyme A dehydrogenase (HADH), mitochondrial transcription factor A (TfAM) as well as quadriceps endurance measures (total work from elastic band and isokinetic knee extension tests), were assessed before and after the intervention period.

Results: The continued progression group sustained their training volume progression during weeks 5–8 compared to weeks 1–4 (median +25%), while the discontinued progression group did not (median -2%) (p = 0.007 between groups). Compared with baseline values, significant between-group differences in fiber type distribution and TfAM muscle protein levels (range ± 17–62%, p < 0.05) and in individual responses to change in Type I and Type IIa fiber type proportion, CS, HADH, and TfAM muscle protein levels outcomes (median 89 vs. 50%, p = 0.001) were seen in favor of the continued progression group. Moreover, only the continued progression group had a significant increase in HADH muscle protein levels (+24%, p = 0.004), elastic band (+56%, p = 0.004) and isokinetic (+7%, p = 0.004) quadriceps endurance, but the between-group differences did not reach statistical significance (range 14–29%, p = 0.330–1.000).

Discussion: The novel findings of the current study were that patients with COPD who had a continued progression of training volume across the 8-weeks intervention had an increased proportion of Type I fibers, and TfAM muscle protein levels and decreased proportion of Type II fibers compared to those that did not continue to progress their training volume after the initial weeks. Additionally, HADH muscle protein levels and quadriceps endurance measurements only improved in the continued progression group, although no significant between-group differences were seen. These findings highlight the importance of continued progression of training volume during resistive training to counteract quadriceps dysfunction within the COPD population. Still, considering the small sample size and the post hoc nature of our analyses, these results should be interpreted cautiously, and further research is necessary.

The Functional Role of Long Non-Coding RNA in Myogenesis and Skeletal Muscle Atrophy

Skeletal muscle is a pivotal organ in humans that maintains locomotion and homeostasis. Muscle atrophy caused by sarcopenia and cachexia, which results in reduced muscle mass and impaired skeletal muscle function, is a serious health condition that decreases life longevity in humans. Recent studies have revealed the molecular mechanisms by which long non-coding RNAs (lncRNAs) regulate skeletal muscle mass and function through transcriptional regulation, fiber-type switching, and skeletal muscle cell proliferation. In addition, lncRNAs function as natural inhibitors of microRNAs and induce muscle hypertrophy or atrophy. Intriguingly, muscle atrophy modifies the expression of thousands of lncRNAs. Therefore, although their exact functions have not yet been fully elucidated, various novel lncRNAs associated with muscle atrophy have been identified. Here, we comprehensively review recent knowledge on the regulatory roles of lncRNAs in skeletal muscle atrophy. In addition, we discuss the issues and possibilities of targeting lncRNAs as a treatment for skeletal muscle atrophy and muscle wasting disorders in humans.

The effect of rapamycin and its analogues on age-related musculoskeletal diseases: a systematic review

BACKGROUND

Preclinical studies have shown a therapeutic role of the mechanistic/mammalian target of rapamycin complex 1 (mTORC1) inhibition with rapamycin and its analogues (rapalogues) on several age-related musculoskeletal disorders (MSKD). However, the applicability to humans of these findings is unknown.

OBJECTIVE

To assess the efficacy of rapalogues on age-related MSKD in humans.

METHODS

We conducted a systematic review according to the PRISMA guidelines. MEDLINE, EMBase, EMCare, and Cochrane Central Registry of Controlled Trials were searched for original studies examining the effects of rapalogues on outcomes linked to the age-related MSKD in humans. This review is registered in the PROSPERO database (University of New York; registration number CRD42020208167).

RESULTS

Fourteen studies met the inclusion criteria and were analyzed. The effect of rapamycin and other rapalogues, including everolimus and temsirolimus, on bone, muscle and joints have been evaluated in humans; however, considerable variability concerning the subjects' age, inclusion criteria, and drug administration protocols was identified. In bone, the use of rapamycin is associated with a decrease in bone resorption markers dependent on osteoclastic activity. In muscle, rapamycin and rapalogues are associated with a reduction in muscle protein synthesis in response to exercise. In the context of rheumatoid arthritis, rapamycin and rapalogues have been associated with clinical improvement and a decrease in inflammatory activity.

CONCLUSION

Although there are studies that have evaluated the effect of rapamycin and rapalogues on MSKD in humans, the evidence supporting its use is still incipient, and the clinical implication of these results on the development of osteoporosis, sarcopenia, or osteosarcopenia has not been studied, opening an interesting field for future research.

Shema Oral Liquid Ameliorates the Severity of LPS-Induced COPD via Regulating DNMT1

Background: Chronic obstructive pulmonary disease (COPD) is the most common respiratory disease with high morbidity and mortality. Shema oral liquid (Shema) is a traditional Chinese medicine (TCM) approved for the treatment of respiratory diseases. Clinical applications have shown that Shema has antitussive, expectorant, and anti-asthmatic effects, but its definite efficacy to COPD is still unclear. This study aimed to explore the therapeutic capacity and potential mechanism of Shema in treatment of COPD.

Methods: Network pharmacology was used to investigated the possible pharmacological mechanism of Shema against COPD. A rat model of lipopolysaccharide (LPS)-induced COPD was established to determine pulmonary ventilatory function, serum inflammatory cytokines, and pulmonary pathological change. Subsequently, tandem mass tag (TMT)-based quantitative proteomics was used to further reveal the therapeutic targets related with Shema against COPD. Western blot was finally performed to validate the expression of targeted proteins screened by proteomics research.

Results: Network pharmacology analysis indicated that Shema against COPD mainly inhibited the inflammation and affected the immune system. The animal experiment demonstrated that Shema treatment protected the lung tissue from LPS induced injury, inhibited the levels of serum inflammatory cytokines such as interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor (TNF)-α, and improved the respiratory ventilatory function by upregulating forced expiratory volume in 0.1 s (FEV0.1), FEV0.3, forced vital capacity (FVC), and the ratios of FEV0.1 (0.3)/FVC. Proteomic analysis and western blot both proved that Shema inhibited the expression of DNA methyltransferase 1 (DNMT1) in the lung tissue.

Conclusion: The therapeutic mechanism of Shema in treatment of COPD may involve inhibiting inflammatory response, improving pulmonary ventilatory function, and alleviating LPS-induced lung injury through regulating the expression of DNMT1. This study also shed light on the development of therapeutic strategies in treating COPD by intervening DNMT-related pathways.

Role of Short-Chain Fatty Acids Produced by Gut Microbiota in Innate Lung Immunity and Pathogenesis of the Heterogeneous Course of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a widespread socially significant disease. The development of COPD involves the innate immune system. Interestingly, the regulation of the innate lung immune system is related to the gut microbiota. This connection is due to the production by gut microorganisms of short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate. Nutritional disturbances and changes in the structure of the intestinal microbiota lead to a decrease in SCFAs production and their effect on pulmonary immunity. The presence of a metabolic and immune axis linking the lungs and gut plays an important role in the pathogenesis of COPD. In addition, the nature of nutrition and SCFAs may participate in the development of the clinically heterogeneous course of COPD.

The effectiveness of short-term pulmonary rehabilitation program in patients with comorbid asthma, chronic obstructive pulmonary disease and obesity

The effectiveness of pulmonary rehabilitation (PR) has not yet been established in patients with asthma – chronic obstructive pulmonary disease overlap (ACO) depending on their nutritional status. We aimed to evaluate the effectiveness of a short-term PR program in patients with comorbid asthma, chronic obstructive pulmonary disease (COPD), and obesity. We included 40 ACO patients and divided them into 3 groups according to body mass index (BMI) and then subdivided them into PR (n=21) and control (n=19) groups. The COPD Assessment Test (CAT), the Asthma Control Test (ACT), and the modified Medical Research Council dyspnea scale (mMRS) were used to evaluate symptoms levels. BODE index (body mass index, forced expiratory volume in one second, dyspnoea, and 6-min walk distance) was used to evaluate the effectiveness of pulmonary rehabilitation. In addition, spirometry and bioimpedansometry were performed. All measurements were done before and after a 6-month PR program. A significantly lower decline in the BODE index was observed in overweight patients (decreased by 43.6% compared to baseline and lower by 40.7% compared to the control group). The six-minute walking test (6MWT) significantly increased in all groups (p<0.001). There was a decrease in total CAT score by 25.4% and by 31.2% in the overweight group (p<0.001). The BMI decreased more in the obese group (by 9.4% compared to baseline). Our study result showed that early use of PR program significantly improves functional capacity and BODE index, leads to dyspnea and CAT scores reduction and improvement in pulmonary function, cause a decrease in BMI, body fat percentage, and visceral fat level, and an increase in muscle mass in overweight and obese patients with ACO.

Prevalence of low muscle mass and associated factors in community-dwelling older adults in Singapore

The population is rapidly aging worldwide, and there is an age-related decline in muscle mass. Therefore, it is important to examine the prevalence and associated factors of low appendicular skeletal muscle mass index (ASMI) in older adults. The objectives of this cross-sectional study were (i) to determine the prevalence of low ASMI (ASM/height²) and (ii) to identify factors associated with low ASMI. This study included 1211 community-dwelling adults aged ≥ 65 years. Low ASMI was defined as < 7.0 kg/m² in males and < 5.7 kg/m² in females (bioelectrical impedance analysis). Gender-specific cut-off values of calf circumference for low ASMI were determined. The prevalence of low ASMI in the overall cohort was 59.9%, i.e., 57.0% among males and 61.8% among females, with no significant difference between genders (P = 0.1068). The prevalence of low ASMI was 81.3% in individuals at risk of malnutrition compared to 20.6% in their counterparts with normal nutritional status (P < 0.0001). Participants with low ASMI were older, had lower physical activity scores, and greater likelihood of hospitalization in prior 6 months compared with normal ASMI (all P < 0.0001). Low ASMI was associated with risk of malnutrition (odds ratio: 3.58 for medium risk, odds ratio: 12.50 for high risk), older age, smoking, drinking, smaller calf circumference, and lower bone mass (all P ≤ 0.0328). Cut-off values of calf circumference for low ASMI for males was 33.4 cm and for females was 32.2 cm. In conclusion, we found that low ASMI was highly prevalent among community-dwelling older adults at risk of malnutrition. Other significant factors associated with low ASMI were age, smoking, drinking, calf circumference, and bone mass. Screening community-dwelling older adults for risk of malnutrition can prevent or delay onset of low ASMI.

Overcoming Therapeutic Inertia to Reduce the Risk of COPD Exacerbations: Four Action Points for Healthcare Professionals

Background

Therapeutic inertia, defined as failure to escalate or initiate adequate therapy when treatment goals are not met, contributes to poor management of COPD exacerbations.

Methods

A multidisciplinary panel of five expert clinicians actively managing COPD and representative of UK practice developed action points to reduce exacerbation risk, based on evidence, clinical expertise, and experience. The action points are applicable despite changing circumstances (eg, virtual clinics). The panel agreed areas where further evidence is needed.

Results

The four action points were (1) an experienced HCP, such as a GP or member of the multi-professional COPD team should review patients within one month of every exacerbation that requires oral steroids, antibiotics, or hospitalization to address modifiable risk factors, optimize non-pharmacological measures, and evaluate pharmacological therapy. (2) Presenting to hospital with an exacerbation defines an important window of opportunity to reduce the risk of further exacerbations. Follow-up by a GP, or member of the multi-professional specialist COPD team within one month of discharge with a full management review and appropriate escalation of pharmacological treatment is essential. (3) Healthcare professionals (HCPs) in all healthcare settings should be able to recognize COPD exacerbations, refer as appropriate and document the episode accurately in medical records across service boundaries. HCPs should support patients to recognize and report exacerbations. (4) HCPs should intervene proactively based on risk assessments, disease activity and any treatable traits at or as soon as possible after diagnosis and annually thereafter. Delivering these action points needs coordinated action with policymakers, funders, and service providers.

Conclusion

These action points should be a fundamental part of clinical practice to determine if a change in management is necessary to reduce the risk of exacerbations. Policymakers should use these action points to develop systems and initiatives that reduce the risk of further exacerbations.

Does branched-chain amino acid supplementation improve pulmonary rehabilitation effect in COPD?

BACKGROUND

Muscle wasting is frequent in chronic obstructive lung disease (COPD) and associated with low branched-chain amino acids (BCAA). We hypothesized that BCAA supplementation could potentiate the effect of a pulmonary rehabilitation program (PRP) by inducing muscular change.

MATERIALS AND METHODS

Sixty COPD patients (GOLD 2-3) were involved in an ambulatory 4-week PRP either with BCAA oral daily supplementation or placebo daily supplementation in a randomized double-blind design. Maximal exercise test including quadriceps oxygenation measurements, functional exercise test, muscle strength, lung function tests, body composition, dyspnea and quality of life were assessed before and after PRP.

RESULTS

Fifty-four patients (64.9 ± 8.3 years) completed the protocol. In both groups, maximal exercise capacity, functional and muscle performances, quality of life and dyspnea were improved after 4-week PRP (p ≤ 0.01). Changes in muscle oxygenation during the maximal exercise and recovery period were not modified after 4-week PRP in BCAA group. Contrarily, in the placebo group the muscle oxygenation kinetic of recovery was slowed down after PRP.

CONCLUSION

This study demonstrated that a 4-week PRP with BCAA supplementation is not more beneficial than PRP alone for patients. A longer duration of supplementation or a more precise targeting of patients would need to be investigated to validate an effect on muscle recovery and to demonstrate other beneficial effects.

Sarcopenia in pulmonary diseases is associated with elevated sarcoplasmic reticulum stress and myonuclear disorganization

Chronic obstructive pulmonary disease (COPD) is frequently associated with age-related muscle loss or sarcopenia. However, the exact molecular mechanism of muscle loss in COPD remains elusive. We investigated the association of chronic dysregulation of sarcoplasmic reticulum (SR) protein homeostasis (a condition called SR stress) and myonuclear disorganization with sarcopenia in patients with COPD. Markers of SR stress and their downstream consequences, including apoptosis and inflammation, were upregulated in patients with COPD. The maximal SR Ca²⁺ ATPase (SERCA) activity was significantly reduced in advanced COPD as compared to healthy controls. Single muscle fiber diameter and cytoplasmic domain per myonucleus were significantly smaller in patients with advanced COPD than in healthy controls. Increased disruption of myonuclear organization was found in the COPD patients as compared to healthy controls. These changes in SR dysfunction were accompanied by elevated global levels of oxidative stress, including lipid peroxidation and mitochondrial reactive oxygen species (ROS) production. Altogether, our data suggest that muscle weakness in advanced COPD is in part associated with the disruption of SR protein and calcium homeostasis and their pathological consequences.

Do Redox Balance and Inflammatory Events Take Place in Mild Bronchiectasis? A Hint to Clinical Implications

We hypothesized that in mild bronchiectasis patients, increased systemic inflammation and redox imbalance may take place and correlate with clinical parameters. In plasma samples from patients with very mild bronchiectasis, inflammatory cells and molecules and redox balance parameters were analyzed. In the patients, lung function and exercise capacity, nutritional status, bacterial colonization, and radiological extension were assessed. Correlations between biological and clinical variables were determined. Compared to healthy controls, levels of acute phase reactants, neutrophils, IgG, IgA, myeloperoxidase, protein oxidation, and GSH increased and lung function and exercise capacity were mildly reduced. GSH levels were even greater in ex-smoker and Pseudomona-colonized patients. Furthermore, radiological extension inversely correlated with airway obstruction and, disease severity, and positively correlated with neutrophil numbers in mild bronchiectasis patients with no nutritional abnormalities. In stable patients with mild bronchiectasis, several important inflammatory and oxidative stress events take place in plasma. These findings suggest that the extension of bronchiectasis probably plays a role in the development of redox imbalance and systemic inflammation in patients with mild bronchiectasis. These results have therapeutic implications in the management of bronchiectasis patients.

Pulmonary Rehabilitation in the Management of Chronic Obstructive Pulmonary Disease among Asian Indians- Current Status and Moving Forward

Chronic Obstructive Pulmonary Disease (COPD) is a significant public health concern in India with high prevalence and associated disability, morbidity, mortality. The progression of COPD is not confined to the lungs but includes extrapulmonary involvement that reduces the functional capacity and quality of life. Pulmonary Rehabilitation (PR) is an evidence-based intervention, targeting multiple domains of pulmonary and extrapulmonary manifestations, and therefore, is recommended as an integral part of COPD management. The practical implementation of PR in India is poor. In this review, we have summarized the latest pieces of evidence in support of PR and highlight the challenges and potential solutions for PR implementation in India.

Identification of Macrophage Polarization-Related Genes as Biomarkers of Chronic Obstructive Pulmonary Disease Based on Bioinformatics Analyses

Objectives

Chronic obstructive pulmonary disease (COPD) is characterized by lung inflammation and remodeling. Macrophage polarization is associated with inflammation and tissue remodeling, as well as immunity. Therefore, this study attempts to investigate the diagnostic value and regulatory mechanism of macrophage polarization-related genes for COPD by bioinformatics analysis and to provide a new theoretical basis for experimental research.

Methods

The raw gene expression profile dataset (GSE124180) was collected from the Gene Expression Omnibus (GEO) database. Next, a weighted gene coexpression network analysis (WGCNA) was conducted to screen macrophage polarization-related genes. The differentially expressed genes (DEGs) between the COPD and normal samples were generated using DESeq2 v3.11 and overlapped with the macrophage polarization-related genes. Moreover, functional annotations of overlapped genes were conducted by Database for Annotation, Visualization and Integrated Discovery (DAVID) Bioinformatics Resource. The immune-related genes were selected, and their correlation with the differential immune cells was analyzed by Pearson. Finally, receiver operating characteristic (ROC) curves were used to verify the diagnostic value of genes.

Results

A total of 4922 coexpressed genes related to macrophage polarization were overlapped with the 203 DEGs between the COPD and normal samples, obtaining 25 genes related to COPD and macrophage polarization. GEM, S100B, and GZMA of them participated in the immune response, which were considered the candidate biomarkers. GEM and S100B were significantly correlated with marker genes of B cells which had a significant difference between the COPD and normal samples. Moreover, GEM was highly associated with the genes in the PI3K/Akt/GSK3β signaling pathway, regulation of actin cytoskeleton, and calcium signaling pathway based on a Pearson correlation analysis of the candidate genes and the genes in the B cell receptor signaling pathway. PPI network analysis also indicated that GEM might participate in the regulation of the PI3K/Akt/GSK3β signaling pathway. The ROC curve showed that GEM possessed an excellent accuracy in distinguishing COPD from normal samples.

Conclusions

The data provide a transcriptome-based evidence that GEM is related to COPD and macrophage polarization likely contributes to COPD diagnosis. At the same time, it is hoped that in-depth functional mining can provide new ideas for exploring the COPD pathogenesis.

Muscle and serum myostatin expression in type 1 diabetes

Type 1 diabetes (T1D) has been reported to negatively affect the health of skeletal muscle, though the underlying mechanisms are unknown. Myostatin, a myokine whose increased expression is associated with muscle‐wasting diseases, has not been reported in humans with T1D but has been demonstrated to be elevated in preclinical diabetes models. Thus, the purpose of this study was to determine if there is an elevated expression of myostatin in the serum and skeletal muscle of persons with T1D compared to controls. Secondarily, we aimed to explore relationships between myostatin expression and clinically important metrics (e.g., HbA_1c, strength, lean mass) in women and men with (N = 31)/without T1D (N = 24) between 18 and 72 years old. Body composition, baseline strength, blood sample and vastus lateralis muscle biopsy were evaluated. Serum, but not muscle, myostatin expression was significantly elevated in those with T1D versus controls, and to a greater degree in T1D women than T1D men. Serum myostatin levels were not significantly associated with HbA_1c nor disease duration. A significant correlation between serum myostatin expression and maximal voluntary contraction (MVC) and body fat mass was demonstrated in control subjects, but these correlations did not reach significance in those with T1D (MVC: R = 0.64 controls vs. R = 0.37 T1D; Body fat: R = −0.52 controls/R = −0.02 T1D). Collectively, serum myostatin was correlated with lean mass (R = 0.45), and while this trend was noted in both groups separately, neither reached statistical significance (R = 0.47 controls/R = 0.33 T1D). Overall, while those with T1D exhibited elevated serum myostatin levels (particularly females) myostatin expression was not correlated with clinically relevant metrics despite some of these relationships existing in controls (e.g., lean/fat mass). Future studies will be needed to fully understand the mechanisms underlying increased myostatin in T1D, with relationships to insulin dosing being particularly important to elucidate.

Risk factors for surgery-related muscle quantity and muscle quality loss and their impact on outcome

Background

Surgery-related loss of muscle quantity negatively affects postoperative outcomes. However, changes of muscle quality have not been fully investigated. A perioperative intervention targeting identified risk factors could improve postoperative outcome. This study investigated risk factors for surgery-related loss of muscle quantity and quality and outcomes after liver resection for colorectal liver metastasis (CRLM).

Methods

Data of patients diagnosed with CRLM who underwent liver resection between 2006 and 2016 were analysed. Muscle quantity (psoas muscle index [PMI]), and muscle quality, (average muscle radiation attenuation [AMA] of the psoas), were measured using computed tomography. Changes in PMI and AMA of psoas after surgery were assessed.

Results

A total of 128 patients were analysed; 67 (52%) had surgery-related loss of muscle quantity and 83 (65%) muscle quality loss. Chronic obstructive pulmonary disease (COPD) (P = 0.045) and diabetes (P = 0.003) were risk factors for surgery-related loss of muscle quantity. A higher age (P = 0.002), open resection (P = 0.003) and longer operation time (P = 0.033) were associated with muscle quality loss. Overall survival was lower in patients with both muscle quantity and quality loss compared to other categories (P = 0.049). The rate of postoperative complications was significantly higher in the group with surgery-related loss of muscle quality.

Conclusions

Risk factors for surgery-related muscle loss were identified. Overall survival was lowest in patients with both muscle quantity and quality loss. Complication rate was higher in patients with surgery-related loss of muscle quality.

Elevated CO2 Levels Delay Skeletal Muscle Repair by Increasing Fatty Acid Oxidation

Muscle dysfunction often occurs in patients with chronic obstructive pulmonary diseases (COPD) and affects ventilatory and non-ventilatory skeletal muscles. We have previously reported that hypercapnia (elevated CO₂ levels) causes muscle atrophy through the activation of the AMPKα2-FoxO3a-MuRF1 pathway. In the present study, we investigated the effect of normoxic hypercapnia on skeletal muscle regeneration. We found that mouse C2C12 myoblasts exposed to elevated CO₂ levels had decreased fusion index compared to myoblasts exposed to normal CO₂. Metabolic analyses of C2C12 myoblasts exposed to high CO₂ showed increased oxidative phosphorylation due to increased fatty acid oxidation. We utilized the cardiotoxin-induced muscle injury model in mice exposed to normoxia and 10% CO₂ for 21 days and observed that muscle regeneration was delayed. High CO₂-delayed differentiation in both mouse C2C12 myoblasts and skeletal muscle after injury and was restored to control levels when cells or mice were treated with a carnitine palmitoyltransfearse-1 (CPT1) inhibitor. Taken together, our data suggest that hypercapnia leads to changes in the metabolic activity of skeletal muscle cells, which results in impaired muscle regeneration and recovery after injury.

Characteristics of effective home-based resistance training in patients with noncommunicable chronic diseases: a systematic scoping review of randomised controlled trials

Skeletal muscle atrophy, dysfunction, and weakness are consequences of noncommunicable diseases which result in exercise and functional limitations which contribute to poor quality of life and increased mortality. Home-based resistance training may promote skeletal muscle health. Electronic-based systematic searches were performed identifying randomised controlled trials utilising home-based resistance training in patients with noncommunicable diseases defined as cancer, cardiovascular disease, diabetes mellitus (type 1 and 2), chronic kidney disease (including dialysis), and chronic respiratory disease (asthma, chronic obstructive pulmonary disease, pulmonary hypertension). A comparator group was defined as one containing "non-exercise" or "usual care". Of the 239 studies identified (published between 1996 and 2020), 22 met the inclusion criteria. Sixteen studies contained an adjunct aerobic training component. Study designs and outcome measures showed large variation. Reporting of the principles of training applied within interventions was poor. Heterogeneity in study characteristics, and poor reporting of training characteristics, prevents formal recommendations for optimising home-based resistance training. However, home-based interventions are less resource-intensive than supervised programmes and appear to have the ability to improve or preserve pertinent outcomes such as strength, functional ability, and quality of life; potentially reducing the risk of mortality in patients with chronic disease.

Differential effects of right and left heart failure on skeletal muscle in rats

BACKGROUND

Exercise intolerance is a cardinal symptom in right (RV) and left ventricular (LV) failure. The underlying skeletal muscle contributes to increased morbidity in patients. Here, we compared skeletal muscle sarcopenia in a novel two-stage model of RV failure to an established model of LV failure.

METHODS

Pulmonary artery banding (PAB) or aortic banding (AOB) was performed in weanling rats, inducing a transition from compensated cardiac hypertrophy (after 7 weeks) to heart failure (after 22-26 weeks). Cardiac function was characterized by echocardiography. Skeletal muscle catabolic/anabolic balance and energy metabolism were analysed by histological and biochemical methods, real-time PCR, and western blot.

RESULTS

Two clearly distinguishable stages of left or right heart disease with a comparable severity were reached. However, skeletal muscle impairment was significantly more pronounced in LV failure. While the compensatory stage resulted only in minor changes, soleus and gastrocnemius muscle of AOB rats at the decompensated stage demonstrated reduced weight and fibre diameter, higher proteasome activity and expression of the muscle-specific ubiquitin E3 ligases muscle-specific RING finger 1 and atrogin-1, increased expression of the atrophy marker myostatin, increased autophagy activation, and impaired mitochondrial function and respiratory chain gene expression. Soleus and gastrocnemius muscle of PAB rats did not show significant changes in muscle weight and proteasome or autophagy activation, but mitochondrial function was mildly impaired as well. The diaphragm did not demonstrate differences in any model or disease stage except for myostatin expression, which was altered at the decompensated stage in both models. Plasma interleukin (IL)-6 and angiotensin II were strongly increased at the decompensated stage (AOB > > PAB). Soleus and gastrocnemius muscle itself demonstrated an increase in IL-6 expression independent from blood-derived cytokines only in AOB animals. In vitro experiments in rat skeletal muscle cells suggested a direct impact of IL-6 and angiotensin II on distinctive atrophic changes.

CONCLUSIONS

Manifold skeletal muscle alterations are more pronounced in LV failure compared with RV failure despite a similar ventricular impairment. Most of the catabolic changes were observed in soleus or gastrocnemius muscle rather than in the constantly active diaphragm. Mitochondrial dysfunction and up-regulation of myostatin were identified as the earliest signs of skeletal muscle impairment.

Mechanisms of IGF-1-Mediated Regulation of Skeletal Muscle Hypertrophy and Atrophy

Insulin-like growth factor-1 (IGF-1) is a key growth factor that regulates both anabolic and catabolic pathways in skeletal muscle. IGF-1 increases skeletal muscle protein synthesis via PI3K/Akt/mTOR and PI3K/Akt/GSK3β pathways. PI3K/Akt can also inhibit FoxOs and suppress transcription of E3 ubiquitin ligases that regulate ubiquitin proteasome system (UPS)-mediated protein degradation. Autophagy is likely inhibited by IGF-1 via mTOR and FoxO signaling, although the contribution of autophagy regulation in IGF-1-mediated inhibition of skeletal muscle atrophy remains to be determined. Evidence has suggested that IGF-1/Akt can inhibit muscle atrophy-inducing cytokine and myostatin signaling via inhibition of the NF-κΒ and Smad pathways, respectively. Several miRNAs have been found to regulate IGF-1 signaling in skeletal muscle, and these miRs are likely regulated in different pathological conditions and contribute to the development of muscle atrophy. IGF-1 also potentiates skeletal muscle regeneration via activation of skeletal muscle stem (satellite) cells, which may contribute to muscle hypertrophy and/or inhibit atrophy. Importantly, IGF-1 levels and IGF-1R downstream signaling are suppressed in many chronic disease conditions and likely result in muscle atrophy via the combined effects of altered protein synthesis, UPS activity, autophagy, and muscle regeneration.

Fortified whey beverage for improving muscle mass in chronic obstructive pulmonary disease: a single-blind, randomized clinical trial

Background

The development of effective nutritional supports for patients with chronic obstructive pulmonary diseases (COPD) is still challenging. This study was conducted to investigate the efficacy of daily consumption of fortified whey on inflammation, muscle mass, functionality, and quality of life in patients with moderate-to-severe COPD.

Methods

A single-blind, randomized trial study was performed on patients with COPD (n = 46). Participants in the intervention group (n = 23) daily received 250 ml of whey beverage fortified with magnesium and vitamin C for 8 weeks. Any changes in inflammatory cytokines (including interleukin- 6 (IL-6) and tumor necrosis factor (TNFα)) were the primary outcomes and the secondary outcomes were fat-free mass, handgrip strength, malnutrition, glutathione and malondialdehyde serum concentrations, and health-related quality of life (HRQoL). Body composition and muscle strength were measured by Bioelectrical Impedance Analysis (BIA) and hydraulic hand dynamometer, respectively. Fat-free mass index (FFMI) was also calculated.

Results

At the end of the study, 44 patients were analyzed. There were significant decreases in IL-6 concentrations in the intervention group compared to the control group. Also, FFMI, body protein, and handgrip strength increased significantly in the intervention group with significant changes between two groups. Moreover, improvement in health-related quality of life was observed in the intervention group compared to the control group. There were no significant changes in other study variables.

Conclusions

This novel nutritional intervention decreased inflammatory cytokines levels, improved indices of skeletal muscle mass and muscle strength, and ultimately, increased HRQoL in patients with moderate-to-severe COPD. Thus, it is suggested to do further studies to assess the effects of nutrition intervention on COPD progression.

Trial registration

IR.SUMS.REC.1396.85 (https://www.irct.ir/).

Early detection of skeletal muscle bioenergetic deficit by magnetic resonance spectroscopy in cigarette smoke-exposed mice

Skeletal muscle dysfunction is a common complication and an important prognostic factor in patients with chronic obstructive pulmonary disease (COPD). It is associated with intrinsic muscular abnormalities of the lower extremities, but it is not known whether there is an easy way to predict its presence. Using a mouse model of chronic cigarette smoke exposure, we tested the hypothesis that magnetic resonance spectroscopy allows us to detect muscle bioenergetic deficit in early stages of lung disease. We employed this technique to evaluate the synthesis rate of adenosine triphosphate (ATP) and characterize concomitant mitochondrial dynamics patterns in the gastrocnemius muscle of emphysematous mice. The fibers type composition and citrate synthase (CtS) and cytochrome c oxidase subunit IV (COX4) enzymatic activities were evaluated. We found that the rate of ATP synthesis was reduced in the distal skeletal muscle of mice exposed to cigarette smoke. Emphysematous mice showed a significant reduction in body weight gain, in the cross-sectional area of the total fiber and in the COX4 to CtS activity ratio, due to a significant increase in CtS activity of the gastrocnemius muscle. Taken together, these data support the hypothesis that in the early stage of lung disease, we can detect a decrease in ATP synthesis in skeletal muscle, partly caused by high oxidative mitochondrial enzyme activity. These findings may be relevant to predict the presence of skeletal bioenergetic deficit in the early stage of lung disease besides placing the mitochondria as a potential therapeutic target for the treatment of COPD comorbidities.

Cellular and molecular features of neurogenic skeletal muscle atrophy

Neurogenic atrophy refers to the loss of muscle mass and function that results directly from injury or disease of the peripheral nervous system. Individuals with neurogenic atrophy may experience reduced functional status and quality of life and, in some circumstances, reduced survival. Distinct pathological findings on muscle histology can aid in diagnosis of a neurogenic cause for muscle dysfunction, and provide indicators for the chronicity of denervation. Denervation induces pleiotypic responses in skeletal muscle, and the molecular mechanisms underlying neurogenic muscle atrophy appear to share common features with other causes of muscle atrophy, including activation of FOXO transcription factors and corresponding induction of ubiquitin-proteasomal and lysosomal degradation. In this review, we provide an overview of histologic features of neurogenic atrophy and a summary of current understanding of underlying mechanisms.

Is inflammatory signaling involved in disease-related muscle wasting? Evidence from osteoarthritis, chronic obstructive pulmonary disease and type II diabetes

Muscle loss is an important feature that occurs in multiple pathologies including osteoarthritis (OA), chronic obstructive pulmonary disease (COPD) and type II diabetes (T2D). Despite differences in pathogenesis and disease-related complications, there are reasons to believe that some fundamental underlying mechanisms are inherent to the muscle wasting process, irrespective of the pathology. Recent evidence shows that inflammation, either local or systemic, contributes to the modulation of muscle mass and/or muscle strength, via an altered molecular profile in muscle tissue. However, it remains ambiguous to which extent and via which mechanisms inflammatory signaling affects muscle mass in disease. Therefore, the objective of the present review is to discuss the role of inflammation on skeletal muscle anabolism, catabolism and functionality in three pathologies that are characterized by an eventual loss in muscle mass (and muscle strength), i.e. OA, COPD and T2D. In OA and COPD, most rodent models confirmed that systemic (COPD) or muscle (OA) inflammation directly induces muscle loss or muscle dysfunctionality. However, in a patient population, the association between inflammation and muscular maladaptations are more ambiguous. For example, in T2D patients, systemic inflammation is associated with muscle loss whereas in OA patients this link has not consistently been established. T2D rodent models revealed that increased levels of advanced glycation end-products (AGEs) and a decreased mTORC1 activation play a key role in muscle atrophy, but it remains to be elucidated whether AGEs and mTORC1 are interconnected and contribute to muscle loss in T2D patients. Generally, if any, associations between inflammation and muscle are mainly based on observational and cross-sectional data. There is definitely a need for longitudinal evidence through well-powered randomized control trials that take into account confounders such as age, disease-phenotypes, comorbidities, physical (in) activity etc. This will allow to improve our understanding of the complex interaction between inflammatory signaling and muscle mass loss and hence contribute to the development of therapeutic strategies to combat muscle wasting in these diseases.

An update on nutrient modulation in the management of disease-induced muscle wasting: evidence from human studies

PURPOSE OF REVIEW

Skeletal muscle has many essential roles in maintaining human health, not only being crucial for locomotion, but further as a metabolically important organ. Muscle wasting in disease (cachexia) is highly prevalent, associated with poor clinical outcomes and is not fully reversible with nutritional interventions. Understanding proteostasis in diseased states is of great importance to design novel, effective nutritional/nutraceutical strategies aimed at alleviating muscle wasting. In this review, we will provide an update on muscle kinetics in disease and the effects of nutritional interventions.

RECENT FINDINGS

Whole body and skeletal muscle kinetics are commonly shown to be imbalanced in disease, promoting overall catabolism that underlies the development of cachexia. However, recent advancements in defining the effectiveness of nutritional interventions on muscle anabolism are clouded by heterogenous patient populations and a lack of direct incorporation stable isotope techniques. Current recommendations are focused on combating malnutrition, with increased protein intake (high in EAA) demonstrating promise.

SUMMARY

Recent progress in understanding catabolic states in cachexia across disease is minimal. Further, studies investigating muscle-specific protein turnover along with nutritional interventions are scarce. As such, there is a significant requirement for strong RCT's investigating both acute and chronic nutritional interventions and their impact on skeletal muscle in individual disease states.

[Evaluation of the relationship between the parameters of peripheral skeletal and respiratory muscles in patients with chronic obstructive pulmonary disease]

Chronic obstructive pulmonary disease (COPD) is a group of diseases with high levels of comorbidity. Pathological changes of peripheral skeletal and respiratory muscles in COPD patients, which are often underestimated, occupy a special place.

AIM

To study the relationship between functional and quantitative parameters of the peripheral (limb muscle) and respiratory muscles in COPD patients.

MATERIALS AND METHODS

127 patients (98 men/29 women, mean age 67.68.2 years) were under observation without acute COPD. All COPD patients were classified according to GOLD (2019) into groups A, B, C, D. The algorithm of the European Working Group on Sarcopenia in Older People (EWGSOP2) was used to diagnose sarcopenia. The muscle mass was measured using dual energy X-ray absorptiometry (DXA) and the appendicular lean mass index (ASM) was estimated. Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) were measured by body plethysmograph MasterScreen Body. Quantitative assessment of thoracic muscle cross-sectional areas were performed using the CT scan using Vidar Dicom Viewer software.

RESULTS

Sarcopenia was diagnosed in 43.3% of COPD patients. Respiratory muscle dysfunction was determined in 66.1% of patients with COPD, its probability increased in groups C and D in comparison with groups A and B [chance ratio 6.6 (95% confidence interval 2.915.0); p0.0001]. Correlations between the functional parameters of sarcopenia and respiratory muscle strength as well as between the mass of peripheral skeletal muscles and respiratory muscle area have been established according to the data of computerized tomography (р0.01). Sarcopenia as well as respiratory muscle dysfunction was observed more frequently in persons with severe and extremely severe airway obstruction and in patients with predominantly emphysematic COPD phenotype (p0.01).

CONCLUSION

Sarcopenia is a frequent comorbidity in COPD and its development is connected with the severity of the course of the main disease. Correlation between parameters of peripheral (limb muscle) and respiratory muscles in patients with COPD has been determined.

Redox modulation of muscle mass and function

Muscle mass and strength are very important for exercise performance. Training-induced musculoskeletal injuries usually require periods of complete immobilization to prevent any muscle contraction of the affected muscle groups. Disuse muscle wasting will likely affect every sport practitioner in his or her lifetime. Even short periods of disuse results in significant declines in muscle size, fiber cross sectional area, and strength. To understand the molecular signaling pathways involved in disuse muscle atrophy is of the utmost importance to develop more effective countermeasures in sport science research.

We have divided our review in four different sections. In the first one we discuss the molecular mechanisms involved in muscle atrophy including the main protein synthesis and protein breakdown signaling pathways. In the second section of the review we deal with the main cellular, animal, and human atrophy models. The sources of reactive oxygen species in disuse muscle atrophy and the mechanism through which they regulate protein synthesis and proteolysis are reviewed in the third section of this review. The last section is devoted to the potential interventions to prevent muscle disuse atrophy with especial consideration to studies on which the levels of endogenous antioxidants enzymes or dietary antioxidants have been tested.

Identifying Protein-metabolite Networks Associated with COPD Phenotypes

Chronic obstructive pulmonary disease (COPD) is a disease in which airflow obstruction in the lung makes it difficult for patients to breathe. Although COPD occurs predominantly in smokers, there are still deficits in our understanding of the additional risk factors in smokers. To gain a deeper understanding of the COPD molecular signatures, we used Sparse Multiple Canonical Correlation Network (SmCCNet), a recently developed tool that uses sparse multiple canonical correlation analysis, to integrate proteomic and metabolomic data from the blood of 1008 participants of the COPDGene study to identify novel protein-metabolite networks associated with lung function and emphysema. Our aim was to integrate -omic data through SmCCNet to build interpretable networks that could assist in the discovery of novel biomarkers that may have been overlooked in alternative biomarker discovery methods. We found a protein-metabolite network consisting of 13 proteins and 7 metabolites which had a -0.34 correlation (p-value = 2.5 × 10^-28) to lung function. We also found a network of 13 proteins and 10 metabolites that had a -0.27 correlation (p-value = 2.6 × 10^-17) to percent emphysema. Protein-metabolite networks can provide additional information on the progression of COPD that complements single biomarker or single -omic analyses.

Expression Levels of Long Non-Coding RNAs Change in Models of Altered Muscle Activity and Muscle Mass

Skeletal muscle is a highly plastic organ that is necessary for homeostasis and health of the human body. The size of skeletal muscle changes in response to intrinsic and extrinsic stimuli. Although protein-coding RNAs including myostatin, NF-κβ, and insulin-like growth factor-1 (IGF-1), have pivotal roles in determining the skeletal muscle mass, the role of long non-coding RNAs (lncRNAs) in the regulation of skeletal muscle mass remains to be elucidated. Here, we performed expression profiling of nine skeletal muscle differentiation-related lncRNAs (DRR, DUM1, linc-MD1, linc-YY1, LncMyod, Neat1, Myoparr, Malat1, and SRA) and three genomic imprinting-related lncRNAs (Gtl2, H19, and IG-DMR) in mouse skeletal muscle. The expression levels of these lncRNAs were examined by quantitative RT-PCR in six skeletal muscle atrophy models (denervation, casting, tail suspension, dexamethasone-administration, cancer cachexia, and fasting) and two skeletal muscle hypertrophy models (mechanical overload and deficiency of the myostatin gene). Cluster analyses of these lncRNA expression levels were successfully used to categorize the muscle atrophy models into two sub-groups. In addition, the expression of Gtl2, IG-DMR, and DUM1 was altered along with changes in the skeletal muscle size. The overview of the expression levels of lncRNAs in multiple muscle atrophy and hypertrophy models provides a novel insight into the role of lncRNAs in determining the skeletal muscle mass.

Muscle Phenotype, Proteolysis, and Atrophy Signaling During Reloading in Mice: Effects of Curcumin on the Gastrocnemius

We hypothesized that curcumin may mitigate muscle protein degradation and loss through attenuation of proteolytic activity in limb muscles of mice exposed to reloading (7dR) following immobilization (7dI). In gastrocnemius of mice (female C57BL/6J, 10 weeks) exposed to recovery following a seven-day period of hindlimb immobilization with/without curcumin treatment, markers of muscle proteolysis (systemic troponin-I), atrophy signaling pathways and histone deacetylases, protein synthesis, and muscle phenotypic characteristics and function were analyzed. In gastrocnemius of reloading mice compared to unloaded, muscle function, structure, sirtuin-1, and protein synthesis improved, while proteolytic and signaling markers (FoxO1/3) declined. In gastrocnemius of unloaded and reloaded mice treated with curcumin, proteolytic and signaling markers (NF-kB p50) decreased and sirtuin-1 activity and hybrid fibers size increased (reloaded muscle), while no significant improvement was seen in muscle function. Treatment with curcumin elicited a rise in sirtuin-1 activity, while attenuating proteolysis in gastrocnemius of mice during reloading following a period of unloading. Curcumin attenuated muscle proteolysis probably via activation of histone deacetylase sirtuin-1, which also led to decreased levels of atrophy signaling pathways. These findings offer an avenue of research in the design of therapeutic strategies in clinical settings of patients exposed to periods of disuse muscle atrophy.

Locomotor Muscles in COPD: The Rationale for Rehabilitative Exercise Training

Exercise training as part of pulmonary rehabilitation is arguably the most effective intervention to improve tolerance to physical exertion in patients with chronic obstructive pulmonary disease (COPD). Owing to the fact that exercise training has modest effects on exertional ventilation, operating lung volumes and respiratory muscle performance, improving locomotor muscle structure and function are key targets for pulmonary rehabilitation in COPD. In the current concise review, we initially discuss whether patients’ muscles are exposed to deleterious factors. After presenting corroboratory evidence on this regard (e.g., oxidative stress, inflammation, hypoxemia, inactivity, and medications), we outline their effects on muscle macro- and micro-structure and related functional properties. We then finalize by addressing the potential beneficial consequences of different training strategies on these muscle-centered outcomes. This review provides, therefore, an up-to-date outline of the rationale for rehabilitative exercise training approaches focusing on the locomotor muscles in this patient population.

Exercise and Chronic Obstructive Pulmonary Disease (COPD)

Systemic effects of COPD lead to cardiovascular co-morbidities, muscle wasting and osteoporosis that, in turn, lead to inactivity and physical deconditioning. This evolution has a direct influence on the health-related quality of life (HRQoL) of patients suffering from this respiratory disease. Pharmacological therapy leads to improvement in shortness of breath, but it has a limited effect on the physical deconditioning. Pulmonary rehabilitation relieves dyspnoea and fatigue, improves emotional function and enhances the sense of control that individuals have over their condition. These improvements are moderately substantial and clinically significant. Rehabilitation serves as an essential component of the management of COPD and is beneficial in improving health-related quality of life and exercise capacity.

Muscle atrophy and regeneration associated with behavioural loss and recovery of function after sciatic nerve crush

AIM

To resolve timing and coordination of denervation atrophy and the re-innervation recovery process to discern correlations indicative of common programs governing these processes.

METHODS

Female Sprague-Dawley (SD) rats had a unilateral sciatic nerve crush. Based on longitudinal behavioural observations, the triceps surae muscle was analysed at different time points post-lesion.

RESULTS

Crush results in a loss of muscle function and mass (-30%) followed by a recovery to almost pre-lesion status at 30 days post-crush (dpc). There was no loss of fibres nor any significant change in the number of nuclei per fibre but a shift in fibres expressing myosins I and II that reverted back to control levels at 30 dpc. A residual was the persistence of hybrid fibres. Early on a CHNR -ε to -γ switch and a re-expression of embryonic MyHC showed as signs of denervation. Foxo1, Smad3, Fbxo32 and Trim63 transcripts were upregulated but not Myostatin, InhibinA and ActivinR2B. Combined this suggests that the mechanism instigating atrophy provides a selectivity of pathway(s) activated. The myogenic differentiation factors (MDFs: Myog, Myod1 and Myf6) were upregulated early on suggesting a role also in the initial atrophy. The regulation of these transcripts returned towards baseline at 30 dpc. The examined genes showed a strong baseline covariance in transcript levels which dissolved in the response to crush driven mainly by the MDFs. At 30 dpc the naïve expression pattern was re-established.

CONCLUSION

Peripheral nerve crush offers an excellent model to assess and interfere with muscle adaptions to denervation and re-innervation.

Computed tomography-derived area and density of pectoralis muscle associated disease severity and longitudinal changes in chronic obstructive pulmonary disease: a case control study

BACKGROUND

Muscle wasting is associated with prognosis in patients with chronic obstructive pulmonary disease (COPD). The cross-sectional area of skeletal muscles on computed tomography (CT) could serve as a method to evaluate body composition. The present study aimed to determine the ability of CT-derived pectoralis muscle area (PMA) and pectoralis muscle density (PMD) to determine the severity of COPD and change in longitudinal pulmonary function in patients with COPD.

METHODS

A total of 293 participants were enrolled in this study, a whom 222 had undergone at least two spirometry measurements within 3 years after baseline data acquisition. PMA and PMD were measured from a single axial slice of chest CT above the aortic arch at baseline. The emphysema index and bronchial wall thickness were quantitatively assessed in all scans. The generalized linear model was used to determine the correlation between PMA and PMD measurements and pulmonary function.

RESULTS

PMA and PMD were significantly associated with baseline lung function and the severity of emphysema (P < 0.05). Patients with the lowest PMA and PMD exhibited significantly more severe airflow obstruction (β = - 0.06; 95% confidence interval: - 0.09 to - 0.03]. PMA was statistically associated with COPD assessment test (CAT) score (P = 0.033). However, PMD did not exhibit statistically significant correlation with either CAT scores or modified Medical Research Council scores (P > 0.05). Furthermore, neither PMA nor PMD were associated with changes in forced expiratory volume in 1 s over a 3-year periods.

CONCLUSIONS

CT-derived features of the pectoralis muscle may be helpful in predicting disease severity in patients with COPD, but are not necessarily associated with longitudinal changes in lung function.

Mitochondrial Dysfunction in Skeletal Muscle Pathologies

Several molecular mechanisms are involved in the regulation of skeletal muscle function. Among them, mitochondrial activity can be identified. The mitochondria is an important and essential organelle in the skeletal muscle that is involved in metabolic regulation and ATP production, which are two key elements of muscle contractibility and plasticity. Thus, in this review, we present the critical and recent antecedents regarding the mechanisms through which mitochondrial dysfunction can be involved in the generation and development of skeletal muscle pathologies, its contribution to detrimental functioning in skeletal muscle and its crosstalk with other typical signaling pathways related to muscle diseases. In addition, an update on the development of new strategies with therapeutic potential to inhibit the deleterious impact of mitochondrial dysfunction in skeletal muscle is discussed.

Arrdc2 and Arrdc3 elicit divergent changes in gene expression in skeletal muscle following anabolic and catabolic stimuli

Skeletal muscle is a highly plastic organ regulating various processes in the body. As such, loss of skeletal muscle underlies the increased morbidity and mortality risk that is associated with numerous conditions. However, no therapies are available to combat the loss of muscle mass during atrophic conditions, which is due in part to the incomplete understanding of the molecular networks altered by anabolic and catabolic stimuli. Thus, the current objective was to identify novel gene networks modulated by such stimuli. For this, total RNA from the tibialis anterior muscle of mice that were fasted overnight or fasted overnight and refed the next morning was subjected to microarray analysis. The refeeding stimulus altered the expression of genes associated with signal transduction. Specifically, expression of alpha arrestin domain containing 2 (Arrdc2) and alpha arrestin domain containing 3 (Arrdc3) was significantly lowered 70–85% by refeeding. Subsequent analysis showed that expression of these genes was also lowered 50–75% by mechanical overload, with the combination of nutrients and mechanical overload acting synergistically to lower Arrdc2 and Arrdc3 expression. On the converse, stimuli that suppress growth such as testosterone depletion or acute aerobic exercise increased Arrdc2 and Arrdc3 expression in skeletal muscle. While Arrdc2 and Arrdc3 exhibited divergent changes in expression following anabolic or catabolic stimuli, no other member of the Arrdc family of genes exhibited the consistent change in expression across the analyzed conditions. Thus, Arrdc2 and Arrdc3 are a novel set of genes that may be implicated in the regulation of skeletal muscle mass.