Cytokine Signaling in Skeletal Muscle Wasting

Activation of the β-adrenergic receptor exacerbates lipopolysaccharide-induced wasting of skeletal muscle cells by increasing interleukin-6 production

The skeletal muscle mass has been shown to be affected by catecholamines, such as epinephrine (Epi), norepinephrine (NE), and isoproterenol (ISO). On the other hand, lipopolysaccharide (LPS), one of the causative substances of sepsis, induces muscle wasting via toll-like receptors expressed in skeletal muscle. Although catecholamines are frequently administered to critically ill patients, it is still incompletely understood how these drugs affect skeletal muscle during critical illness, including sepsis. Herein, we examined the direct effects of catecholamines on LPS-induced skeletal muscle wasting using the C2C12 myoblast cell line. Muscle wasting induced by catecholamines and/or LPS was analyzed by the use of the differentiated C2C12 myotubes, and its underlying mechanism was explored by immunoblotting analysis, quantitative reverse transcription polymerase chain reaction (qRT-PCR), enzyme-linked immunosorbent assay (ELISA), and the TransAM kit for p-65 NF-κB. Epi augmented myosin heavy chain (MHC) protein loss and reduction of the myotube diameter induced by LPS. LPS induced C/EBPδ protein, Atrogin-1 and inteleukin-6 (IL-6), and these responses were potentiated by Epi. An IL-6 inhibitor, LMT28, suppressed the potentiating effect of Epi on the LPS-induced responses. NF-κB activity was induced by LPS, but was not affected by Epi and recombinant IL-6, and the NF-κB inhibitor, Bay 11–7082, abolished Atrogin-1 mRNA expression induced by LPS with or without Epi. NE and ISO also potentiated LPS-induced IL-6 and Atroign-1 mRNA expression. Carvedilol, a nonselective β-adrenergic receptor antagonist, suppressed the facilitating effects of Epi on the Atrogin-1 mRNA induction by LPS, and abolished the effects of Epi on the MHC protein loss in the presence of LPS. It was concluded that Epi activates the β-adrenergic receptors in C2C12 myotubes and the IL-6-STAT3 pathway, leading to the augmentation of LPS-induced activation of the NF-κB- C/EBPδ-Atrogin-1 pathway and to the exacerbation of myotube wasting.

Phosphodiesterase 4 inhibition restrains muscle proteolysis in diabetic rats by activating PKA and EPAC/Akt effectors and inhibiting FoxO factors

AIM

There is growing evidence about the ability of cyclic adenosine monophosphate (cAMP) signaling and nonselective phosphodiesterase (PDE) inhibitors on mitigate muscle atrophy. PDE4 accounts for the major cAMP hydrolyzing activity in skeletal muscles, therefore advances are necessary about the consequences of treatment with PDE4 inhibitors on protein breakdown in atrophied muscles. We postulated that rolipram (selective PDE4 inhibitor) may activate cAMP downstream effectors, inhibiting proteolytic systems in skeletal muscles of diabetic rats.

MAIN METHODS

Streptozotocin-induced diabetic rats were treated with 2 mg/kg rolipram for 3 days. Changes in the levels of components belonging to the proteolytic machineries in soleus and extensor digitorum longus (EDL) muscles were investigated, as well as cAMP effectors.

KEY FINDINGS

Treatment of diabetic rats with rolipram decreased the levels of atrogin-1 and MuRF-1 in soleus and EDL, and reduced the activities of calpains and caspase-3; these findings partially explains the low ubiquitin conjugates levels and the decreased proteasome activity. The inhibition of muscle proteolysis may be occurring due to phosphorylation and inhibition of forkhead box O (FoxO) factors, probably as a consequence of the increased cAMP levels, followed by the activation of PKA and Akt effectors. Akt activation may be associated with the increased levels of exchange protein directly activated by cAMP (EPAC). As a result, rolipram treatment spared muscle mass in diabetic rats.

SIGNIFICANCE

The antiproteolytic responses associated with PDE4 inhibition may be helpful to motivate future investigations about the repositioning of PDE4 inhibitors for the treatment of muscle wasting conditions.

Emerging Treatment Options for Sarcopenia in Chronic Liver Disease

Sarcopenia is characterized by a skeletal muscle disorder with progressive and generalized loss of muscle mass and function, and it increases the risk of adverse outcomes with considerable prevalence in patients with chronic liver disease. Sarcopenia in chronic liver disease underlies complicated and multifactorial mechanisms for pathogenesis, including alterations in protein turnover, hyperammonemia, energy disposal, hormonal changes, and chronic inflammation. The key contribution to sarcopenia in patients with chronic liver diseases can be the hyperammonemia-induced upregulation of myostatin, which causes muscle atrophy via the expression of atrophy-related genes. Several clinical studies on emerging treatment options for sarcopenia have been reported, but only a few have focused on patients with chronic liver diseases, with mostly nutritional and behavioral interventions being carried out. The inhibition of the myostatin-activin receptor signaling pathway and hormonal therapy might be the most promising therapeutic options in combination with an ammonia-lowering approach in sarcopenic patients with chronic liver diseases. This review focuses on current and emerging treatment options for sarcopenia in chronic liver diseases with underlying mechanisms to counteract this condition.

Skeletal Muscle Wasting and Function Impairment in Intensive Care Patients With Severe COVID-19

Background: Intensive care patients commonly develop muscle wasting and functional impairment. However, the role of severe COVID-19 in the magnitude of muscle wasting and functionality in the acute critical disease is unknown.

Objective: To perform a prospective characterization to evaluate the skeletal muscle mass and functional performance in intensive care patients with severe COVID-19.

Methods: Thirty-two critically ill patients (93.8% male; age: 64.1 ± 12.6 years) with the diagnosis of the severe COVID-19 were prospectively recruited within 24 to 72 h following intensive care unit (ICU) admission, from April 2020 to October 2020, at Hospital Sírio-Libanês in Brazil. Patients were recruited if older than 18 years old, diagnosis of severe COVID-19 confirmed by RT-PCR, ICU stay and absence of limb amputation. Muscle wasting was determined through an ultrasound measurement of the rectus femoris cross-sectional area, the thickness of the anterior compartment of the quadriceps muscle (rectus femoris and vastus intermedius), and echogenicity. The peripheral muscle strength was assessed with a handgrip test. The functionality parameter was determined through the ICU mobility scale (IMS) and the International Classification of Functioning, Disability and Health (ICF). All evaluations were performed on days 1 and 10.

Results: There were significant reductions in the rectus femoris cross-section area (−30.1% [95% IC, −26.0% to −34.1%]; P < 0.05), thickness of the anterior compartment of the quadriceps muscle (−18.6% [95% IC, −14.6% to 22.5%]; P < 0.05) and handgrip strength (−22.3% [95% IC, 4.7% to 39.9%]; P < 0.05) from days 1 to 10. Patients showed increased mobility (0 [0–5] vs 4.5 [0–8]; P < 0.05), improvement in respiratory function (3 [3–3] vs 2 [1–3]; P < 0.05) and structure respiratory system (3 [3–3] vs 2 [1–3]; P < 0.05), but none of the patients returned to normal levels.

Conclusion: In intensive care patients with severe COVID-19, muscle wasting and decreased muscle strength occurred early and rapidly during 10 days of ICU stay with improved mobility and respiratory functions, although they remained below normal levels. These findings may provide insights into skeletal muscle wasting and function in patients with severe COVID-19.

A standardized herbal combination of Astragalus membranaceus and Paeonia japonica, protects against muscle atrophy in a C26 colon cancer cachexia mouse model

ETHNOPHARMACOLOGICAL RELEVANCE

Astragalus membranaceus (Fisch.) and Bunge and Paeonia japonica (Makino)Miyabe & H.Takeda have been traditionally used to improve the poor quality of life such as weakness, lack of appetite, fatigue, and malaise which is considered with cachexia condition.

AIM OF THE STUDY

We investigated anti-cachectic effects of a herbal formula composed of Astragalus membranaceus and Paeonia japonica (APX) and the molecular mechanisms of APX in C26 cancer-induced cachexia mice and TNF-a-treated C2C12 myotubes. Additionally synergistic anti-cachectic effects of APX were compared to those of individual herbal extracts and megestrol acetate.

METHODS AND MATERIALS

The forty-two BALB/c mice were randomly divided into 6 groups: normal (nontreatment), control (C26 injection), AM (C26 injection with Astragalus membranaceus), PJ (C26 injection with Paeonia japonica), APX (C26 injection with combination of Astragalus membranaceus and Paeonia japonica and MA (C26 injection with megestrol acetate). All mice were orally administered DW (normal and control groups) or 100 mg/kg AM, PJ, APX or MA for 10 days. In the animal model, several tissues were weighed, and muscle tissue and blood were used to measure pro-inflammatory cytokines. C2C12 myotubes were exposed to 100 ng/mL TNF- α with or without 10 μg/mL of AM, PJ, APX or MA for 48 h. The cells were used to immunofluorescence staining and western blot analyses.

RESULTS

C26 injection induced notable body and muscle weight loss while APX administration significantly attenuated these alterations and the decrease of muscle weights and strength. APX also significantly attenuated the abnormal elevations in the concentration of three muscle atrophy-inducible cytokines; serum and muscle TNF-α,muscle TWEAK and IL-6 in C26 tumor-bearing mice. In the TNF-α-treated C2C12 myotube model, TNF-α treatment notably decreased MyH but activated atrophic proteins (MuRF and Fbx32) along with p38 and NFκB while these molecular alterations were significantly ameliorated by APX treatment. These pharmacological actions of APX were supported by the results of immunofluorescence staining to MyH expression and the translocation of NFκB into the nucleus in C2C12 myotubes.

CONCLUSIONS

Our data indicate the potential of an herbal formula, APX as an anti-cachexia agent; the effect of APX was superior to that of megestrol acetate overall especially for muscle atrophy. The underlying mechanisms of this herbal formula may involve the modulation of muscle atrophy-promoting molecules including p38, NFκB, TNF-α and TWEAK.

Surface-directed engineering of tissue anisotropy in microphysiological models of musculoskeletal tissue

Here, we present an approach to model and adapt the mechanical regulation of morphogenesis that uses contractile cells as sculptors of engineered tissue anisotropy in vitro. Our method uses heterobifunctional cross-linkers to create mechanical boundary constraints that guide surface-directed sculpting of cell-laden extracellular matrix hydrogel constructs. Using this approach, we engineered linearly aligned tissues with structural and mechanical anisotropy. A multiscale in silico model of the sculpting process was developed to reveal that cell contractility increases as a function of principal stress polarization in anisotropic tissues. We also show that the anisotropic biophysical microenvironment of linearly aligned tissues potentiates soluble factor-mediated tenogenic and myogenic differentiation of mesenchymal stem cells. The application of our method is demonstrated by (i) skeletal muscle arrays to screen therapeutic modulators of acute oxidative injury and (ii) a 3D microphysiological model of lung cancer cachexia to study inflammatory and oxidative muscle injury induced by tumor-derived signals.

The phenotypic and transcriptomic effects of developmental exposure to nanomolar levels of estrone and bisphenol A in zebrafish

Estrone and BPA are two endocrine disrupting chemicals (EDCs) that are predicted to be less potent than estrogens such as 17β-estradiol and 17α-ethinylestradiol. Human exposure concentrations to estrone and BPA can be as low as nanomolar levels. However, very few toxicological studies have focused on the nanomolar-dose effects. Low level of EDCs can potentially cause non-monotonic responses. In addition, exposures at different developmental stages can lead to different health outcomes. To identify the nanomolar-dose effects of estrone and BPA, we used zebrafish modeling to study the phenotypic and transcriptomic responses after extended duration exposure from 0 to 5 days post-fertilization (dpf) and short-term exposure at days 4-5 post fertilization. We found that non-monotonic transcriptomic responses occurred after extended duration exposures at 1 nM of estrone or BPA. At this level, estrone also caused hypoactivity locomotive behavior in zebrafish. After both extended duration and short-term exposures, BPA led to more apparent phenotypic responses, i.e. skeletal abnormalities and locomotion changes, and more significant transcriptomic responses than estrone exposure. After short-term exposure, BPA at concentrations equal or above 100 nM affected locomotive behavior and changed the expression of both estrogenic and non-estrogenic genes that are linked to neurological diseases. These data provide gaps of mechanisms between neurological genes expression and associated phenotypic response due to estrone or BPA exposures. This study also provides insights for assessing the acceptable concentration of BPA and estrone in aquatic environments.

Increase in muscle mass associated with the prebiotic effects of 1-kestose in super-elderly patients with sarcopenia

Sarcopenia causes functional disorders and decreases the quality of life. Thus, it has attracted substantial attention in the aging modern world. Dysbiosis of the intestinal microbiota is associated with sarcopenia; however, it remains unclear whether prebiotics change the microbiota composition and result in the subsequent recovery of muscle atrophy in elderly patients with sarcopenia. This study aimed to assess the effects of prebiotics in super-elderly patients with sarcopenia. We analyzed the effects of 1-kestose on the changes in the intestinal microbiota and body composition using a next-generation sequencer and a multi-frequency bioimpedance analysis device. The Bifidobacterium longum population was significantly increased in the intestine after 1-kestose administration. In addition, in all six patients after 12 weeks of 1-kestose administration, the skeletal muscle mass index was greater, and the body fat percentage was lower. This is the first study to show that administration of a prebiotic increased the population of B. longum in the intestinal microbiota and caused recovery of muscle atrophy in super-elderly patients with sarcopenia.

Sleep Deprivation Interferes with JAK/STAT Signaling Pathway and Myogenesis in the Masseter Muscle of Rats

OBJECTIVES

The aim of the study was to study the Janus kinase/tyrosine kinase-activated transduction factor (JAK/STAT) signaling pathway and myogenesis on the masseter muscle after sleep deprivation and to investigate the role of stress in this scenario.

SUBJECTS AND METHODS

A total of 18 male Wistar rats were divided into the following groups: control (n = 6): animals were not submitted to any procedures, and paradoxical sleep deprivation and vehicle (PSD + V; n = 6): animals were subjected to PSD for 96 h and (PSD + MET; n = 6): animals were subjected to PSD for 96 h with administration of metyrapone. Paradoxical sleep deprivation was performed by the modified multiple platforms method. Histopathological analysis, histomorphometry, and immunohistochemistry were performed.

RESULTS

The results showed the presence of inflammatory infiltrate in the PSD + V and PSD + MET groups and atrophy. Histomorphometry showed that the cellular profile area decreased, while cellular density increased in both experimental groups. Expression of p-STAT 3, MyoD, and MyoG increased in the PSD + V group, while the PSD + MET group showed increased expression of IL-6 and p-STAT 3.

CONCLUSION

Our results suggest that sleep deprivation induces an inflammatory response and atrophy in the masseter muscle of rats.

Phytobiotics to improve health and production of broiler chickens: functions beyond the antioxidant activity

Phytobiotics, also known as phytochemicals or phytogenics, have a wide variety of biological activities and have recently emerged as alternatives to synthetic antibiotic growth promoters. Numerous studies have reported the growth-promoting effects of phytobiotics in chickens, but their precise mechanism of action is yet to be elucidated. Phytobiotics are traditionally known for their antioxidant activity. However, extensive investigations have shown that these compounds also have anti-inflammatory, antimicrobial, and transcription-modulating effects. Phytobiotics are non-nutritive constituents, and their bioavailability is low. Nonetheless, their beneficial effects have been observed in several tissues or organs. The health benefits of the ingestion of phytobiotics are attributed to their antioxidant activity. However, several studies have revealed that not all these benefits could be explained by the antioxidant effects alone. In this review, I focused on the bioavailability of phytobiotics and the possible mechanisms underlying their overall effects on intestinal barrier functions, inflammatory status, gut microbiota, systemic inflammation, and metabolism, rather than the specific effects of each compound. I also discuss the possible mechanisms by which phytobiotics contribute to growth promotion in chickens.

The Relevance of a Physical Active Lifestyle and Physical Fitness on Immune Defense: Mitigating Disease Burden, With Focus on COVID-19 Consequences

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a fast spreading virus leading to the development of Coronavirus Disease-2019 (COVID-19). Severe and critical cases are characterized by damage to the respiratory system, endothelial inflammation, and multiple organ failure triggered by an excessive production of proinflammatory cytokines, culminating in the high number of deaths all over the world. Sedentarism induces worse, continuous, and progressive consequences to health. On the other hand, physical activity provides benefits to health and improves low-grade systemic inflammation. The aim of this review is to elucidate the effects of physical activity in physical fitness, immune defense, and its contribution to mitigate the severe inflammatory response mediated by SARS-CoV-2. Physical exercise is an effective therapeutic strategy to mitigate the consequences of SARS-CoV-2 infection. In this sense, studies have shown that acute physical exercise induces the production of myokines that are secreted in tissues and into the bloodstream, supporting its systemic modulatory effect. Therefore, maintaining physical activity influence balance the immune system and increases immune vigilance, and also might promote potent effects against the consequences of infectious diseases and chronic diseases associated with the development of severe forms of COVID-19. Protocols to maintain exercise practice are suggested and have been strongly established, such as home-based exercise (HBE) and outdoor-based exercise (OBE). In this regard, HBE might help to reduce levels of physical inactivity, bed rest, and sitting time, impacting on adherence to physical activity, promoting all the benefits related to exercise, and attracting patients in different stages of treatment for COVID-19. In parallel, OBE must improve health, but also prevent and mitigate COVID-19 severe outcomes in all populations. In conclusion, HBE or OBE models can be a potent strategy to mitigate the progress of infection, and a coadjutant therapy for COVID-19 at all ages and different chronic conditions.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Skeletal muscle-specific over-expression of the nuclear sirtuin SIRT6 blocks cancer-associated cachexia by regulating multiple targets

BACKGROUND

During cancer cachexia, cytokines released from tumour cells can alter body's metabolism, which can lead to onset of this disease process. Biological basis of cachexia is multifactorial; hence, it is important to identify and modulate multiple targets to curtail the process of cachexia. Previously, we reported that the nuclear sirtuin, SIRT6, blocks expression of myostatin, a negative regulator of muscle growth, through modulation of the NF-κB signalling. This study was undertaken to test whether muscle-specific over-expression of SIRT6 can block the cancer-associated muscle wasting in vivo and to identify additional relevant targets of SIRT6, which can explain its ability to maintain muscle health.

METHODS

We generated a skeletal muscle-specific SIRT6 over-expressing transgenic mouse line (Sk.T6Tg) expressing SIRT6 at a moderate (two-fold to four-fold) level, compared with its control littermates. To generate a cancer-cachexia model, B16F10 mouse melanoma cells were injected subcutaneously in the flanks of mice. Gastrocnemius muscle tissues from non-tumour and tumour controls and Sk.T6Tg mice (n = 5-20) were analysed by histology, immunoblotting, and RT-qPCR. Plasma samples of mice were evaluated using cytokine arrays and ELISA in both non-tumour and tumour conditions.

RESULTS

Our results demonstrate dual benefits of muscle-specific moderate over-expression of SIRT6 in a mouse model of cancer-cachexia. In tumour-bearing mice, SIRT6 over-expression preserved muscle weight (P < 0.001) and fibre size (P < 0.005) as well as suppressed tumour growth (P < 0.05). SIRT6 over-expression significantly reduced myostatin expression and plasma free fatty acids levels but maintained plasma insulin levels in tumour-bearing mice. These positive effects of SIRT6 were associated with downregulation of the circulatory chemokine, CXCL10, and the myokine, WNT4. SIRT6 also upregulated expression of GLUT4, the major glucose transporter in the skeletal muscle. These results for the first time demonstrate that SIRT6 regulates multiple targets to limit tumour growth and cancer-associated muscle atrophy.

CONCLUSION

Given the multifactorial nature of cachexia, SIRT6, which concurrently controls multiple pathways, can be a valuable therapeutic target to overcome this debilitating syndrome.

A prospective controlled study on Ramadan fasting in the healthy young males in summer in Germany: effect on cytokines

SHORT COMMUNICATION

During the Ramadan fasting (RF) month, participants restrict some activities during day time, particularly consumption of food and beverages. In Germany, Muslims fast about 18-19 h a day when Ramadan falls in the summer. This longer period of restriction could lead to the changes of the body physiology, anthropometric parameters and biological mediators.

OBJECTIVES

This study aimed to determine the effect of Ramadan fasting on cytokines (Interleukin (IL)-1β. IL-6, IL-8, IL-10, IL-12, tumor necrosis factor (TNF)-α) during RF in Germany. Correlations of cytokines with anthropometric parameters were also determined.

METHODS

Fifty healthy adult males were recruited and divided into two equal groups: fasting group (FG) and non-fasting group (NFG). FG was evaluated at T1: one week before, T2: mid-, T3: last days of, and T4: one week after Ramadan. The NFG were evaluated only at T1 and T3.

RESULTS

In FG significant alterations of IL-1β was observed. Insignificant differences were found between the FG and NFG at T1 and T3 concerning the measured cytokines. Circulating IL-1β increased significantly from T2 to T4 and from T3 to T4. At T3, TNF-α was correlated significantly with anthropometric parameters such as the body weight, the skeletal muscle mass and the fat free mass, whilst IL-12 was correlated significantly with the skeletal muscle mass, the fat free mass and the body water mass at T4.

CONCLUSIONS

Significant Alterations of IL-1β during RF in FG were observed. Anthropometric parameters correlate with TNF-α and IL-12 levels during at T3 and T4, respectively.

Angiotensin II-induced muscle atrophy via PPARγ suppression is mediated by miR-29b

The activation of the renin-angiotensin system (RAS) induced by increased angiotensin II (AngII) levels has been implicated in muscle atrophy, which is involved in the pathogenesis of congestive heart failure. Although peroxisome proliferator-activated receptor gamma (PPARγ) activation can suppress RAS, the exact role of PPARγ in AngII-induced muscle atrophy is unclear. Here we identified PPARγ as a negative regulator of miR-29b, a microRNA that is able to promote multiple types of muscle atrophy. Suppression of miR-29b could prevent AngII-induced muscle atrophy both in vitro and in vivo. IGF1, PI3K(p85α), and Yin Yang 1 (YY1) were identified as target genes of miR-29b, and overexpression of these targets could rescue AngII-induced muscle atrophy. Importantly, inhibition of PPARγ was sufficient to induce muscle atrophy, while PPARγ overexpression could attenuate that. These data indicate that the PPARγ/miR-29b axis mediates AngII-induced muscle atrophy, and increasing PPARγ or inhibiting miR-29b represents a promising approach to counteract AngII-induced muscle atrophy.

RNA-sequencing reveals transcriptional signature of pathological remodeling in the diaphragm of rats after myocardial infarction

The diaphragm is the main inspiratory muscle, and the chronic phase post-myocardial infarction (MI) is characterized by diaphragm morphological, contractile, and metabolic abnormalities. However, the mechanisms of diaphragm weakness are not fully understood. In the current study, we aimed to identify the transcriptome changes associated with diaphragm abnormalities in the chronic stage MI. We ligated the left coronary artery to cause MI in rats and performed RNA-sequencing (RNA-Seq) in diaphragm samples 16 weeks post-surgery. The sham group underwent thoracotomy and pericardiotomy but no artery ligation. We identified 112 differentially expressed genes (DEGs) out of a total of 9664 genes. Myocardial infarction upregulated and downregulated 42 and 70 genes, respectively. Analysis of DEGs in the framework of skeletal muscle-specific biological networks suggest remodeling in the neuromuscular junction, extracellular matrix, sarcomere, cytoskeleton, and changes in metabolism and iron homeostasis. Overall, the data are consistent with pathological remodeling of the diaphragm and reveal potential biological targets to prevent diaphragm weakness in the chronic stage MI.

Gut microbiome - A potential mediator of pathogenesis in heart failure and its comorbidities: State-of-the-art review

Gut microbiome (GMB) has been increasingly recognized as a contributor to development and progression of heart failure (HF), immune-mediated subtypes of cardiomyopathy (myocarditis and anthracycline-induced cardiotoxicity), response to certain cardiovascular drugs, and HF-related comorbidities, such as chronic kidney disease, cardiorenal syndrome, insulin resistance, malnutrition, and cardiac cachexia. Gut microbiome is also responsible for the "gut hypothesis" of HF, which explains the adverse effects of gut barrier dysfunction and translocation of GMB on the progression of HF. Furthermore, accumulating evidence has suggested that gut microbial metabolites, including short chain fatty acids, trimethylamine N-oxide (TMAO), amino acid metabolites, and bile acids, are mechanistically linked to pathogenesis of HF, and could, therefore, serve as potential therapeutic targets for HF. Even though there are a variety of proposed therapeutic approaches, such as dietary modifications, prebiotics, probiotics, TMAO synthesis inhibitors, and fecal microbial transplant, targeting GMB in HF is still in its infancy and, indeed, requires further preclinical and clinical evidence. In this review, we aim to highlight the role gut microbiome plays in HF pathophysiology and its potential as a novel therapeutic target in HF.

Inhibition of lncRNA MAAT Controls Multiple Types of Muscle Atrophy by cis- and trans-Regulatory Actions

Muscle atrophy is associated with negative outcomes in a variety of diseases. Identification of a common therapeutic target would address a significant unmet clinical need. Here, we identify a long non-coding RNA (lncRNA) (muscle-atrophy-associated transcript, lncMAAT) as a common regulator of skeletal muscle atrophy. lncMAAT is downregulated in multiple types of muscle-atrophy models both in vivo (denervation, Angiotensin II [AngII], fasting, immobilization, and aging-induced muscle atrophy) and in vitro (AngII, H₂O₂, and tumor necrosis factor alpha [TNF-α]-induced muscle atrophy). Gain- and loss-of-function analysis both in vitro and in vivo reveals that downregulation of lncMAAT is sufficient to induce muscle atrophy, while overexpression of lncMAAT can ameliorate multiple types of muscle atrophy. Mechanistically, lncMAAT negatively regulates the transcription of miR-29b through SOX6 by a trans-regulatory module and increases the expression of the neighboring gene Mbnl1 by a cis-regulatory module. Therefore, overexpression of lncMAAT may represent a promising therapy for muscle atrophy induced by different stimuli.

Flavonoids: nutraceutical potential for counteracting muscle atrophy

Skeletal muscle plays a vital role in the conversion of chemical energy into physical force. Muscle atrophy, characterized by a reduction in muscle mass, is a symptom of chronic disease (cachexia), aging (sarcopenia), and muscle disuse (inactivity). To date, several trials have been conducted to prevent and inhibit muscle atrophy development; however, few interventions are currently available for muscle atrophy. Recently, food ingredients, plant extracts, and phytochemicals have received attention as treatment sources to prevent muscle wasting. Flavonoids are bioactive polyphenol compounds found in foods and plants. They possess diverse biological activities, including anti-obesity, anti-diabetes, anti-cancer, anti-oxidation, and anti-inflammation. The effects of flavonoids on muscle atrophy have been investigated by monitoring molecular mechanisms involved in protein turnover, mitochondrial activity, and myogenesis. This review summarizes the reported effects of flavonoids on sarcopenia, cachexia, and disuse muscle atrophy, thus, providing an insight into the understanding of the associated molecular mechanisms.

COVID-19-Associated Acute Kidney Injury and Quantified Protein Catabolic Rate: A Likely Effect of Cytokine Storm on Muscle Protein Breakdown

Rationale & Objectives

Previously we reported a cohort of patients with coronavirus disease 2019 (COVID-19)–associated acute kidney injury (AKI) with striking biochemical evidence of tissue breakdown in the absence of apparent rhabdomyolysis. We sought to quantify the extent of tissue catabolism in similar patients.

Study Design

During acute peritoneal dialysis (PD) in patients with COVID-19–associated AKI, we measured urea Kt/V adequacy and calculated the daily urea nitrogen generation rate while quantifying daily protein intake.

Setting & Population

We did calculations in 8 patients with COVID-9–associated AKI undergoing acute PD at Mount Sinai Hospital in New York City. As a comparator, we obtained urea kinetic parameters from our database of ambulatory patients receiving maintenance PD.

Exposure or Predictors

8 patients with COVID-19–associated AKI undergoing acute PD.

Outcomes

Urea nitrogen generation rate in relation to daily protein intake.

Analytical Approach

Urea nitrogen generation rate from urea kinetics was related to measured daily dietary protein intake in these patients and we compared it with this relationship in ambulatory maintenance PD patients for whom both parameters were calculated from urea kinetics.

Results

Urea nitrogen generation rate in patients with AKI was 10.2 ± 5 g/d, which is more than 2-fold higher than for stable outpatients receiving maintenance PD (4.7 ± 3 g/d) despite similar dietary protein intake (74.8 ± 11 vs 67.2 ± 29 g/d, respectively). This strongly suggests endogenous protein breakdown, probably from muscle. Urea nitrogen generation rate in these patients with AKI corresponds to 315 g/d of ongoing muscle breakdown and cumulative 2.5 kg of muscle breakdown during the early course of AKI.

Limitations

Small number of participants and assumptions in comparing urea nitrogen generation rate with protein intake.

Conclusions

In highly catabolic patients, an endogenous source of urea generation such as muscle protein breakdown seems to be the most likely explainable cause for our findings. This is the first study that we are aware of to quantify the degree of endogenous protein breakdown induced by COVID-19–related cytokine storm.

Effects of plant-derived isoquinoline alkaloids on growth performance and intestinal function of broiler chickens under heat stress

Broiler chickens reared under heat stress (HS) conditions have decreased growth performance and show metabolic and immunologic alterations. This study aimed to evaluate the effect of supplementation with a standardized blend of plant-derived isoquinoline alkaloids (IQ) on the growth performance, protein catabolism, intestinal barrier function, and inflammatory status of HS-treated chickens. Three hundred sixty 0-day-old Ross 308 male broiler chickens were randomly distributed into 2 treatment groups: control diet (no additives) or diet supplemented with 100 ppm IQ. At day 14, the chicks in each diet group were further divided into 2 groups, each of which was reared under thermoneutral (TN) (22.4°C) or constant HS (33.0°C) conditions until day 42. Each group consisted of 6 replicates with 15 birds per replicate, and chickens were provided ad libitum access to water and feed. During days 15–21, the body weight gain (BWG) and feed intake (FI) were significantly lower in the HS treatment group than in the TN group, and feed conversion ratio was higher (P < 0.05); these factors were not alleviated by IQ supplementation. During days 22–42, the final BW, BWG, and FI of the HS birds were better among those administered IQ than those that were not (P < 0.05). HS treatment increased plasma lipid peroxide, corticosterone, and uric acid concentrations as well as serum fluorescein isothiocyanate–dextran, a marker of intestinal barrier function, and decreased plasma total protein content (P < 0.05). These changes were not observed in the IQ group, suggesting that IQ supplementation improved oxidative damage, protein catabolism, and intestinal barrier function of chickens under HS. Isoquinoline alkaloid supplementation inhibited the expression of intestinal inflammatory factors, IL-6, tumor necrosis factor–like factor 1A, and inducible nitric oxide synthase under HS treatment (P < 0.05). These results suggest that IQ supplementation can improve the growth performance of broiler chickens under HS conditions, which may be associated with amelioration of oxidative damage, protein catabolism, intestinal barrier function, and inflammation.

Taurine Attenuates Catabolic Processes Related to the Onset of Sarcopenia

Sarcopenia that occurs with advancing age is characterized by a gradual loss of muscle protein component due to the activation of catabolic pathways, increased level of inflammation, and mitochondrial dysfunction. Experimental evidence demonstrates that several physio-pathological processes involved in the onset of sarcopenia may be counteracted by the intake of specific amino acids or antioxidant molecules, suggesting that diet may represent an effective strategy for improving the anabolic response of muscle during aging. The non-essential amino acid taurine is highly expressed in several mammalian tissues, including skeletal muscle where it is involved in the ion channel regulation, in the modulation of intracellular calcium concentration, and where it plays an important role as an antioxidant and anti-inflammatory factor. Here, with the purpose to reproduce the chronic low-grade inflammation characteristics of senescent muscle in an in vitro system, we exploited the role of Tumor Necrosis Factor α (TNF) and we analyzed the effect of taurine in the modulation of different signaling pathways known to be dysregulated in sarcopenia. We demonstrated that the administration of high levels of taurine in myogenic L6 cells stimulates the differentiation process by downregulating the expression of molecules involved in inflammatory pathways and modulating processes such as autophagy and apoptosis. Although further studies are currently ongoing in our laboratory to better elucidate the molecular mechanisms responsible for the positive effect of taurine on myogenic differentiation, this study suggests that taurine supplementation may represent a strategy to delay the loss of mass and functionality characteristic of senescent muscles.

Targeting the JAK2/STAT3 Pathway-Can We Compare It to the Two Faces of the God Janus?

Muscle cachexia is one of the most critical unmet medical needs. Identifying the molecular background of cancer-induced muscle loss revealed a promising possibility of new therapeutic targets and new drug development. In this review, we will define the signal transducer and activator of transcription 3 (STAT3) protein's role in the tumor formation process and summarize the role of STAT3 in skeletal muscle cachexia. Finally, we will discuss a vast therapeutic potential for the STAT3-inhibiting single-agent treatment innovation that, as the desired outcome, could block tumor growth and generally prevent muscle cachexia.

Diphlorethohydroxycarmalol (DPHC) Isolated from the Brown Alga Ishige okamurae Acts on Inflammatory Myopathy as an Inhibitory Agent of TNF-α

Inflammation affects various organs of the human body, including skeletal muscle. Phlorotannins are natural biologically active substances found in marine brown algae and exhibit anti-inflammatory activities. In this study, we focused on the effects of phlorotannins on anti-inflammatory activity and skeletal muscle cell proliferation activity to identify the protective effects on the inflammatory myopathy. First, the five species of marine brown algal extracts dramatically inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW 264.7 cells without toxicity at all the concentrations tested. Moreover, the extracts collected from Ishige okamurae (I. okamurae) significantly increased cell proliferation of C2C12 myoblasts compared to the non-treated cells with non-toxicity. In addition, as a result of finding a potential tumor necrosis factor (TNF)-α inhibitor that regulates the signaling pathway of muscle degradation in I. okamurae-derived natural bioactive compounds, Diphlorethohydroxycarmalol (DPHC) is favorably docked to the TNF-α with the lowest binding energy and docking interaction energy value. Moreover, DPHC down-regulated the mRNA expression level of pro-inflammatory cytokines and suppressed the muscle RING-finger protein (MuRF)-1 and Muscle Atrophy F-box (MAFbx)/Atrgoin-1, which are the key protein muscle atrophy via nuclear factor-κB (NF-κB), and mitogen-activated protein kinase (MAPKs) signaling pathways in TNF-α-stimulated C2C12 myotubes. Therefore, it is expected that DPHC isolated from IO would be developed as a TNF-α inhibitor against inflammatory myopathy.

The sustained expression of Cas9 targeting toxic RNAs reverses disease phenotypes in mouse models of myotonic dystrophy type 1

Myotonic dystrophy type I (DM1) is a multisystemic autosomal-dominant inherited human disorder that is caused by CTG microsatellite repeat expansions (MREs) in the 3' untranslated region of DMPK. Toxic RNAs expressed from such repetitive sequences can be eliminated using CRISPR-mediated RNA targeting, yet evidence of its in vivo efficacy and durability is lacking. Here, using adult and neonatal mouse models of DM1, we show that intramuscular or systemic injections of adeno-associated virus (AAV) vectors encoding nuclease-dead Cas9 and a single-guide RNA targeting CUG repeats results in the expression of the RNA-targeting Cas9 for up to three months, redistribution of the RNA-splicing protein muscleblind-like splicing regulator 1, elimination of foci of toxic RNA, reversal of splicing biomarkers and amelioration of myotonia. The sustained reversal of DM1 phenotypes provides further support that RNA-targeting Cas9 is a viable strategy for treating DM1 and other MRE-associated diseases.

Myokines mediate the cross talk between skeletal muscle and other organs

Myokines are muscle-derived cytokines and chemokines that act extensively on organs and exert beneficial metabolic functions in the whole-body through specific signal networks. Myokines as mediators provide the conceptual basis for a whole new paradigm useful for understanding how skeletal muscle communicates with other organs. In this review, we summarize and discuss classes of myokines and their physiological functions in mediating the regulatory roles of skeletal muscle on other organs and the regulation of the whole-body energy metabolism. We review the mechanisms involved in the interaction between skeletal muscle and nonmuscle organs through myokines. Moreover, we clarify the connection between exercise, myokines and disease development, which may contribute to the understanding of a potential mechanism by which physical inactivity affects the process of metabolic diseases via myokines. Based on the current findings, myokines are important factors that mediate the effect of skeletal muscle on other organ functions and whole-body metabolism.

TNF Receptor-Associated Factor 6 Mediates TNFα-Induced Skeletal Muscle Atrophy in Mice During Aging

During aging, muscle mass decreases, leading to sarcopenia, associated with low-level chronic inflammation (inflammaging), which induces sarcopenia by promoting proteolysis of muscle fibers and inhibiting their regeneration. Patients with a variety of pathologic conditions associated with sarcopenia, including rheumatoid arthritis (RA), have systemically elevated TNFα serum levels, and transgenic mice with TNFα overexpression (TNF-Tg mice, a model of RA) develop sarcopenia between adolescence and adulthood before they age. However, if and how TNFα contributes to the pathogenesis of sarcopenia during the normal aging process and in RA remains largely unknown. We report that TNFα levels are increased in skeletal muscles of aged WT mice, associated with muscle atrophy and decreased numbers of satellite cells and Type IIA myofibers, a phenotype that we also observed in adult TNF-Tg mice. Aged WT mice also have increased numbers of myeloid lineage cells in their skeletal muscles, including macrophages and granulocytes. These cells have increased TNFα expression, which impairs myogenic cell differentiation. Expression levels of TNF receptor-associated factor 6 (TRAF6), an E3 ubiquitin ligase, which mediates signaling by some TNF receptor (TNFR) family members, are elevated in skeletal muscles of both aged WT mice and adult TNF-Tg mice. TRAF6 binds to TNFR2 in C2C12 myoblasts and mediates TNFα-induced muscle atrophy through NF-κB-induced transcription of the muscle-specific E3 ligases, Atrogen1 and Murf1, which promote myosin heavy-chain degradation. Haplo-deficiency of TRAF6 prevents muscle atrophy and the decrease in numbers of satellite cells, Type IIA myofibers, and myogenic regeneration in TRAF6^+/- ;TNF-Tg mice. Our findings suggest that pharmacologic inhibition of TRAF6 signaling in skeletal muscles during aging could treat/prevent age- and RA-related sarcopenia by preventing TNFα-induced proteolysis and inhibition of muscle fiber regeneration. © 2020 American Society for Bone and Mineral Research.

Impact of Protein Intake in Older Adults with Sarcopenia and Obesity: A Gut Microbiota Perspective

The continuous population increase of older adults with metabolic diseases may contribute to increased prevalence of sarcopenia and obesity and requires advocacy of optimal nutrition treatments to combat their deleterious outcomes. Sarcopenic obesity, characterized by age-induced skeletal-muscle atrophy and increased adiposity, may accelerate functional decline and increase the risk of disability and mortality. In this review, we explore the influence of dietary protein on the gut microbiome and its impact on sarcopenia and obesity. Given the associations between red meat proteins and altered gut microbiota, a combination of plant and animal-based proteins are deemed favorable for gut microbiota eubiosis and muscle-protein synthesis. Additionally, high-protein diets with elevated essential amino-acid concentrations, alongside increased dietary fiber intake, may promote gut microbiota eubiosis, given the metabolic effects derived from short-chain fatty-acid and branched-chain fatty-acid production. In conclusion, a greater abundance of specific gut bacteria associated with increased satiation, protein synthesis, and overall metabolic health may be driven by protein and fiber consumption. This could counteract the development of sarcopenia and obesity and, therefore, represent a novel approach for dietary recommendations based on the gut microbiota profile. However, more human trials utilizing advanced metabolomic techniques to investigate the microbiome and its relationship with macronutrient intake, especially protein, are warranted.

Preclinical Evaluation of a Food-Derived Functional Ingredient to Address Skeletal Muscle Atrophy

Skeletal muscle is the metabolic powerhouse of the body, however, dysregulation of the mechanisms involved in skeletal muscle mass maintenance can have devastating effects leading to many metabolic and physiological diseases. The lack of effective solutions makes finding a validated nutritional intervention an urgent unmet medical need. In vitro testing in murine skeletal muscle cells and human macrophages was carried out to determine the effect of a hydrolysate derived from vicia faba (PeptiStrong: NPN_1) against phosphorylated S6, atrophy gene expression, and tumour necrosis factor alpha (TNF-α) secretion, respectively. Finally, the efficacy of NPN_1 on attenuating muscle waste in vivo was assessed in an atrophy murine model. Treatment of NPN_1 significantly increased the phosphorylation of S6, downregulated muscle atrophy related genes, and reduced lipopolysaccharide-induced TNF-α release in vitro. In a disuse atrophy murine model, following 18 days of NPN_1 treatment, mice exhibited a significant attenuation of muscle loss in the soleus muscle and increased the integrated expression of Type I and Type IIa fibres. At the RNA level, a significant upregulation of protein synthesis-related genes was observed in the soleus muscle following NPN_1 treatment. In vitro and preclinical results suggest that NPN_1 is an effective bioactive ingredient with great potential to prolong muscle health.

Role of Age-Related Mitochondrial Dysfunction in Sarcopenia

Skeletal muscle aging is associated with a significant loss of skeletal muscle strength and power (i.e., dynapenia), muscle mass and quality of life, a phenomenon known as sarcopenia. This condition affects nearly one-third of the older population and is one of the main factors leading to negative health outcomes in geriatric patients. Notwithstanding the exact mechanisms responsible for sarcopenia are not fully understood, mitochondria have emerged as one of the central regulators of sarcopenia. In fact, there is a wide consensus on the assumption that the loss of mitochondrial integrity in myocytes is the main factor leading to muscle degeneration. Mitochondria are also key players in senescence. It has been largely proven that the modulation of mitochondrial functions can induce the death of senescent cells and that removal of senescent cells improves musculoskeletal health, quality, and function. In this review, the crosstalk among mitochondria, cellular senescence, and sarcopenia will be discussed with the aim to elucidate the role that the musculoskeletal cellular senescence may play in the onset of sarcopenia through the mediation of mitochondria.

Inflammation and metabolism: the role of adiposity in sarcopenic obesity

Sarcopenic obesity is characterised by the double burden of diminished skeletal muscle mass and the presence of excess adiposity. From a mechanistic perspective, both obesity and sarcopenia are associated with sub-acute, chronic pro-inflammatory states that impede metabolic processes, disrupting adipose and skeletal functionality, which may potentiate disease. Recent evidence suggests that there is an important cross-talk between metabolism and inflammation, which has shifted focus upon metabolic-inflammation as a key emerging biological interaction. Dietary intake, physical activity and nutritional status are important environmental factors that may modulate metabolic-inflammation. This paradigm will be discussed within the context of sarcopenic obesity risk. There is a paucity of data in relation to the nature and the extent to which nutritional status affects metabolic-inflammation in sarcopenic obesity. Research suggests that there may be scope for the modulation of sarcopenic obesity with alterations in diet. The potential impact of increasing protein consumption and reconfiguration of dietary fat composition in human dietary interventions are evaluated. This review will explore emerging data with respect to if and how different dietary components may modulate metabolic-inflammation, particularly with respect to adiposity, within the context of sarcopenic obesity.

Effects of leucine-enriched essential amino acid supplementation on muscular fatigue and inflammatory cytokines in wheelchair basketball players

PURPOSE

This study aimed to investigate the effects of leucine-enriched essential amino acid (LEAA) supplementation on muscle fatigue and the level of inflammatory cytokines in wheelchair basketball players after a basketball game and interval training.

METHODS

Of the ten recruited wheelchair basketball players (aged 34.5±8.9 years; lean body mass of 34.3±10.0 kg) who had spinal cord injury (SCI) and had undergone amputation, nine participated in the final test. These nine athletes received LEAA supplements (3 times 4.0 g/day) or placebo treatment in a double-blind, randomized, crossover study. We measured variables related to muscular fatigue and inflammatory response before the intense exercise and 4 days after recovery.

RESULTS

The significant effect of LEAA supplementation was inhibition of circulating IL-6 levels in the LEAA-treated group compared with the placebo group (P < .05). However, no changes were observed in the TNF-α and creatinine kinase levels. Moreover, analysis of variance analysis showed no significant difference in the relative values of muscle soreness. However, the effect size analysis with Cohen's d reported a significant improvement in the relative values of whole body and back muscle soreness.

CONCLUSION

Our results revealed that LEAA supplementation before and after intense exercise could help reduce muscle soreness and IL-6 levels in wheelchair basketball players.

An open-label, single-center pilot study to test the effects of an amino acid mixture in older patients admitted to internal medicine wards

OBJECTIVE

Older patients are frequently subjected to prolonged hospitalization and extended bed rest, with a negative effect on physical activity and caloric intake. This results in a consistent loss of muscle mass and function, which is associated with functional decline and high mortality. The aim of this study was to investigate the effect of 1 wk of oral amino acid (AA) supplementation in older patients subjected to low mobility during hospitalization.

METHODS

Hospitalized older patients (69-87) were included in the control group (n = 50) or were administered 25 g of AA mixture (n = 44) twice daily throughout 7 d of low mobility. We collected data related to length of stay as primary outcome measure. In-hospital mortality, 90-d postdischarge mortality, 90-d postdischarge rehospitalization, and falls also were considered. Moreover, variations of anthropometric measures, body composition and muscle architecture/strength, circulating interleukins, and oxidative stress markers between the beginning and the end of the supplementation period were analyzed as secondary outcomes.

RESULTS

Similar values were reported between the two groups regarding age (76.6 ± 6.8 versus 79 ± 7.2 y old), body weight (61.5 ± 14.3 versus 62.1 ± 16.1 kg), and body mass index (28.7 ± 4.15 versus 28.1 ± 3.62 kg/m²). Although no difference in terms of in-hospital, 90-d postdischarge, or overall mortality rate was observed between the two groups, a reduction in length of stay, 90-d postdischarge hospitalization, and falls was observed in the AA supplementation group rather than in controls. Furthermore, the AA mixture limited muscle architecture/strength impairment and circulating oxidative stress, which occurred during hospitalization-related bed rest. The latter data was associated with increased circulating levels of anti-inflammatory cytokines interleukin-4 and -10.

CONCLUSIONS

These results suggest that the AA mixture limits several alterations associated with low mobility in older hospitalized patients, such as length of stay, 90-d postdischarge hospitalization, and falls, preventing the loss of muscle function, as well as the increase of circulating interleukins and oxidative stress markers.

Association between skeletal muscle attenuation and gastroesophageal reflux disease: A health check-up cohort study

Sarcopenia is defined as skeletal muscle attenuation and has an association with metabolic syndrome. Metabolic syndrome, which includes obesity, is one of known predictive factors for gastroesophageal reflux disease (GERD). This study aimed to elucidate the association between sarcopenia and GERD. We retrospectively reviewed electronic medical records of 8,218 patients who were performed an upper gastrointestinal endoscopy at check-up center of the Gangnam Severance Hospital. GERD was diagnosed by endoscopic findings. Erosive reflux disease (ERD) included Barrett's esophagus and reflux esophagitis, with the exception of minimal change esophagitis. Sarcopenia was defined by appendicular skeletal muscle (skeletal muscle in the upper and lower limbs). Sarcopenic obesity was defined as the presence of both sarcopenia and obesity. Associations between sarcopenia and GERD, as well as between sarcopenic obesity and ERD, were analyzed. A total of 3,414 patients were diagnosed with GERD, and 574 (16.8%) had sarcopenia. Sarcopenia was independent predictive factor for GERD (odds ratio [OR] = 1.170, 95% confidence interval [CI]: 1.016-1.346, P = 0.029). In addition, male sex, smoking, alcohol, and diet, including sweets and fatty food, had a significant association with GERD. A total of 1,423 (17.3%) of 8,218 patients were diagnosed with ERD, and 302 (21.2%) had sarcopenia. Male sex, smoking, and fatty food consumption had a significant association with ERD. Moreover, sarcopenia (OR = 1.215, 95% CI: 1.019-1.449, P = 0.030), obesity (OR = 1.343, 95% CI: 1.163-1.552, P < 0.001), and sarcopenic obesity (OR = 1.406, 95% CI: 1.195-1.654, P < 0.001) were independent predictive factors for ERD. Sarcopenia is associated with GERD, and sarcopenic obesity may be predictive factor for ERD.

miR-7 Restores Phenotypes in Myotonic Dystrophy Muscle Cells by Repressing Hyperactivated Autophagy

Unstable CTG expansions in the 3’ UTR of the DMPK gene are responsible for myotonic dystrophy type 1 (DM1) condition. Muscle dysfunction is one of the main contributors to DM1 mortality and morbidity. Pathways by which mutant DMPK trigger muscle defects, however, are not fully understood. We previously reported that miR-7 was downregulated in a DM1 Drosophila model and in biopsies from patients. Here, using DM1 and normal muscle cells, we investigated whether miR-7 contributes to the muscle phenotype by studying the consequences of replenishing or blocking miR-7, respectively. Restoration of miR-7 with agomiR-7 was sufficient to rescue DM1 myoblast fusion defects and myotube growth. Conversely, oligonucleotide-mediated blocking of miR-7 in normal myoblasts led to fusion and myotube growth defects. miR-7 was found to regulate autophagy and the ubiquitin-proteasome system in human muscle cells. Thus, low levels of miR-7 promoted both processes, and high levels of miR-7 repressed them. Furthermore, we uncovered that the mechanism by which miR-7 improves atrophy-related phenotypes is independent of MBNL1, thus suggesting that miR-7 acts downstream or in parallel to MBNL1. Collectively, these results highlight an unknown function for miR-7 in muscle dysfunction through autophagy- and atrophy-related pathways and support that restoration of miR-7 levels is a candidate therapeutic target for counteracting muscle dysfunction in DM1.

Hyperbaric Normoxia Improved Glucose Metabolism and Decreased Inflammation in Obese Diabetic Rat

Hyperbaric treatment improves hyperglycemia and hyperinsulinemia in type 2 diabetes associated with obesity. However, its mode of action is unknown. The purpose of the present study was to investigate the influences of regular hyperbaric treatment with normal air at 1.3 atmospheres absolute (ATA) on glucose tolerance in type 2 diabetes with obesity. The focus was directed on inflammatory cytokines in the adipose tissue and skeletal muscle. Otsuka Long-Evans Tokushima Fatty (OLETF) rats were used as models of type 2 diabetes with obesity and Long-Evans Tokushima Otsuka (LETO) rats served as healthy controls. The rats were randomly assigned to untreated or hyperbaric treatment groups exposed to 1.3 ATA for 8 h d-1 and 5 d wk-1 for 16 wks. Glucose levels were significantly higher in the diabetic than in the healthy control rats. Nevertheless, glucose levels at 30 and 60 min after glucose administration were significantly lower in the diabetic rats treated with 1.3 ATA than in the untreated diabetic rats. Insulin levels at fasting and 120 min after glucose administration were significantly lower in the diabetic rats treated with 1.3 ATA than in the untreated diabetic rats. Hyperbaric treatment also increased interleukin-10 (IL-10) expression in the skeletal muscle and decreased tumor necrosis factor α (TNFα) expression in adipose tissue. These results suggested that TNFα downregulation and IL-10 upregulation in diabetic rats subjected to hyperbaric treatment participate in the crosstalk between the adipose and skeletal muscle tissues and improve glucose intolerance.

Inhibitory Effects of N-[2-(4-acetyl-1-piperazinyl) phenyl]-2-(2-chlorophenoxy) acetamide on Osteoclast Differentiation In Vitro via the Downregulation of TRAF6

Osteoclasts are poly-nuclear cells that resorb mineral components from old or damaged bone tissue. Primary mononuclear cells are activated by receptor activator of nuclear factor kappa-Β ligand (RANKL) and differentiate into large multinucleated cells. Dysregulation of osteoclast differentiation can lead to pathological bone loss and destruction. Many studies have focused on the development of new molecules to regulate RANKL-mediated signaling. In this study, N-[2-(4-acetyl-1-piperazinyl)phenyl]-2-(2-chlorophenoxy) acetamide (PPOA-N-Ac-2-Cl) led to a significant decrease in the formation of multinucleated tartrate-resistant acid phosphatase (TRAP)-positive cells in a dose-dependent manner, without inducing significant cytotoxicity. PPOA-N-Ac-2-Cl affected the expression of osteoclast-specific marker genes, such as TRAF6, c-fos, DC-STAMP, NFATc1, MMP9, CtsK, and TRAP (Acp5), during RANKL-mediated osteoclastogenesis. Moreover, PPOA-N-Ac-2-Cl significantly attenuated the protein levels of CtsK, a critical protease involved in bone resorption. Accordingly, bone resorption activity and F-actin ring formation decreased in the presence of PPOA-N-Ac-2-Cl. In conclusion, this study shows that PPOA-N-Ac-2-Cl acts as an inhibitor of osteoclast differentiation and may serve as a potential candidate agent for the treatment of osteoclast-related bone diseases by virtue of attenuating bone resorption.

Red Bean Extract Inhibits Immobilization-Induced Muscle Atrophy in C57BL/6N Mice

Muscle atrophy, which is characterized by a decrease in muscle mass, function, and protein content, can be caused by aging, disease, and physical inactivity. Red bean or Adzuki bean (Vigna angularis) has been consumed as an edible legume. Red bean possesses various functional properties, such as antidiabetes, antiaging, anti-inflammatory, anticancer, and hepatoprotective activities. However, little is known about its potential inhibitory effect on muscle atrophy. In this study, we investigated the inhibitory effect of red bean extract (RBE) on muscle atrophy in an immobilized hindlimb muscle of C57BL/6J mice. RBE dose-dependently increased grip strength, exercise endurance, muscle weight, and myofiber area. At the molecular level, RBE significantly reduced the mRNA expression of proteolysis-related genes, such as muscle ring finger and muscle atrophy F-box by preventing the translocation of Forkhead box 3. RBE also activated the phosphatidylinositol 3 kinase/Akt pathway, subsequently stimulating the mammalian target of rapamycin/70-kDa ribosomal protein S6 kinase/eukaryotic initiation factor 4E binding protein 1 pathway involved in protein synthesis. Overall, red bean could be used as a functional food ingredient or therapeutic agent to inhibit muscle atrophy.

The Role of Genetic Profile in Functional Performance Adaptations to Exercise Training or Physical Activity: A Systematic Review of the Literature

Background: Variations in genotype may contribute to heterogeneity in functional adaptations to exercise. Methods: A systematic search of eight databases was conducted, and 9,696 citations were screened. Results: Eight citations from seven studies measuring 10 single-nucleotide polymorphisms and nine different functional performance test outcomes were included in the review. There was one observational study of physical activity and six experimental studies of aerobic or resistance training. The ACE (D) allele, ACTN3 (RR) genotype, UCP2 (GG) genotype, IL-6-174 (GG) genotype, TNF-α-308 (GG) genotype, and IL-10-1082 (GG) genotype all predicted significantly superior adaptations in at least one functional outcome in older men and women after prescribed exercise or in those with higher levels of physical activity. Conclusion: There is a small amount of evidence that older adults may have better functional outcomes after exercise/physical activity if they have specific alleles related to musculoskeletal function or inflammation. However, more robust trials are needed.

Systems biology and network pharmacology of frailty reveal novel epigenetic targets and mechanisms

Frailty is an age-associated condition, characterized by an inappropriate response to stress that results in a higher frequency of adverse outcomes (e.g., mortality, institutionalization and disability). Some light has been shed over its genetic background, but this is still a matter of debate. In the present study, we used network biology to analyze the interactome of frailty-related genes at different levels to relate them with pathways, clinical deficits and drugs with potential therapeutic implications. Significant pathways involved in frailty: apoptosis, proteolysis, muscle proliferation, and inflammation; genes as FN1, APP, CREBBP, EGFR playing a role as hubs and bottlenecks in the interactome network and epigenetic factors as HIST1H3 cluster and miR200 family were also involved. When connecting clinical deficits and genes, we identified five clusters that give insights into the biology of frailty: cancer, glucocorticoid receptor, TNF-α, myostatin, angiotensin converter enzyme, ApoE, interleukine-12 and −18. Finally, when performing network pharmacology analysis of the target nodes, some compounds were identified as potentially therapeutic (e.g., epigallocatechin gallate and antirheumatic agents); while some other substances appeared to be toxicants that may be involved in the development of this condition.

Circulating factors associated with sarcopenia during ageing and after intensive lifestyle intervention

BACKGROUND

Ageing, chronic diseases, prolonged inactivity, and inadequate nutrition pose a severe threat to skeletal muscle health and function. To date, experimental evidence suggests that ageing-related subclinical inflammation could be an important causative factor in sarcopenia. Although inflammatory signalling has been implicated in the pathogenesis of experimental animal models of sarcopenia, few studies have surveyed the clinical association between circulating factors and muscle mass in patients before and after lifestyle interventions. In this study, we evaluated whether proinflammatory cytokines are associated with the onset of sarcopenia, which circulating factors are associated with the severity of sarcopenia, and how these factors change after lifestyle interventions in sarcopenic elderly persons.

METHODS

A total of 56 elderly subjects (age ≥ 60 years) with sarcopenia and 56 elderly non-sarcopenic subjects, who met entry criteria and had given informed consent, were selected from the Peking Union Medical College Hospital multicentre prospective longitudinal sarcopenia study for testing relevant circulating factors. Thirty-two elderly subjects from the sarcopenic cohort completed a 12 week intensive lifestyle intervention programme with whey supplements (30 g/day) and a personalized resistance training regimen. The levels of proinflammatory cytokines and metabolic hormones, pre-intensive and post-intensive lifestyle interventions, were measured.

RESULTS

The sarcopenic group was significantly older (72.05 ± 6.54 years; P < 0.001), more likely to be inactive and female (57.1% of all sarcopenic patients), and had a higher prevalence of type 2 diabetes (16% higher risk). Compared with non-sarcopenic subjects, serum interleukin (IL)-6, IL-18, tumour necrosis factor-α (TNF-α), TNF-like weak inducer of apoptosis (TWEAK), and leptin were significantly higher, while insulin growth factor 1, insulin, and adiponectin were significantly lower in sarcopenic patients (all P < 0.05). Logistic regression analyses revealed that high levels of TNF-α (>11.15 pg/mL) and TWEAK (>1276.48 pg/mL) were associated with a 7.6-fold and 14.3-fold increased risk of sarcopenia, respectively. After adjustment for confounding variables, high levels of TWEAK were still associated with a 13.4-fold increased risk of sarcopenia. Intensive lifestyle interventions led to significant improvements in sarcopenic patients' muscle mass and serum profiles of TWEAK, TNF-α, IL-18, insulin, and adiponectin (all P < 0.05).

CONCLUSIONS

High levels of the inflammatory cytokines TWEAK and TNF-α are associated with an increased risk of sarcopenia, while the metabolic hormones insulin growth factor 1, insulin, and adiponectin are associated with a decreased risk of sarcopenia in our Chinese patient cohort. Intensive lifestyle interventions could significantly improve muscle mass, reduce inflammation, and restore metabolic hormone levels in sarcopenic patients. This trial was registered at clinicaltrials.gov as NCT02873676.

Current pharmacotherapies for sarcopenia

Introduction: Sarcopenia, the age-related loss of skeletal muscle mass and function, is a global health problem that contributes to the development of physical disability, morbidity and mortality in the ageing population. Sarcopenia is now recognised in many countries as a muscle disease with an ICD-10-CM Diagnosis Code for billing care related to this condition, despite no FDA-approved treatments being currently available. Areas covered: This review highlights the current state of knowledge regarding the biological mechanisms contributing to the age-related loss of muscle mass and function and provides a summary of existing and emerging pharmacotherapies in clinical trials for sarcopenia. Expert opinion: While understanding of the pathophysiology of sarcopenia has progressed, rigorous preclinical studies that better inform clinical trials are needed to accelerate drug discovery and identify safe and effective treatments. Few drugs have been developed specifically for sarcopenia and many have failed to meet clinically relevant outcomes related to strength and physical performance. The multifactorial complexity of sarcopenia means that tailored, personalised treatments are more likely to be required than just a single intervention.

Mitochondria-Derived Damage-Associated Molecular Patterns in Sepsis: From Bench to Bedside

Sepsis is one of the most serious health hazards. Current research suggests that the pathogenesis of sepsis is mediated by both pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). Mitochondria are among the most important organelles in cells and determine their life and death. A variety of mitochondria-derived DAMPs (mtDAMPs) are similar to bacteria because mitochondria are derived from bacteria according to the mitochondrial endosymbiotic theory. Their activated signaling pathways extensively affect organ functions, the immune system, and metabolic functions in sepsis. In this review, we describe the essential roles of mtDAMPs in sepsis and discuss their research prospects and clinical importance.

Effects of dietary glutamine supplementation on immune cell polarization and muscle regeneration in diabetic mice with limb ischemia

PURPOSE

Diabetes is a chronic inflammatory disorder resulting in endothelial dysfunction which contributes to peripheral arterial disease and limb ischemia. Leukocytes play critical roles in vascular and tissue remodelling after ischemia. This study investigated the effects of dietary glutamine (GLN) supplementation on immune cell polarization in diabetic mice subjected to limb ischemia.

METHODS

Diabetes was induced by an intraperitoneal injection of streptozotocin for 5 consecutive days in C57BL/6J mice. Diabetic mice were fed the AIN-93 diet or an AIN-93 diet in which a part of the casein was replaced by GLN. After 3 weeks of the dietary intervention, mice were subjected to unilateral femoral artery ligation to induce limb ischemia.

RESULTS

GLN supplementation enhanced the proportion of anti-inflammatory monocytes and regulatory T cells in the blood. Expression of C-C motif chemokine receptor 5 by activated CD4⁺ T cells was promoted and prolonged in the GLN-supplemented group. GLN downregulated the percentage of M1 macrophages in muscle tissues which was correlated with lower levels of C-C motif chemokine ligand 2 in plasma. The muscle M1/M2 ratio was also reduced in the GLN group. Gene expression of interleukin-6 was suppressed by GLN supplementation, while expression levels of the peroxisome proliferator-activated receptor γ and myogenic differentiation 1 genes were elevated in post-ischemic muscles. Histological findings also indicated that muscle regeneration was accelerated in the GLN group.

CONCLUSIONS

GLN supplementation in diabetic mice may exert more-balanced polarization of CD4⁺ T cells, monocytes, and macrophages, thus attenuating inflammatory responses and contributing to muscle regeneration after limb ischemia.

Low muscle mass and strength in pediatrics patients: Why should we care?

Skeletal muscle plays major roles in metabolism and overall health across the lifecycle. Emerging evidence indicates that prenatal (maternal diet during pregnancy and genetic defects) and postnatal factors (physical activity, hormones, dietary protein, and obesity) influence muscle mass acquisition and strength early in life. As a consequence, low muscle mass and strength contributes to several adverse health outcomes during childhood. Specifically, studies demonstrated inverse associations of muscle mass and strength to single and clustered metabolic risk factors. The literature also consistently reports that low muscle mass and strength are associated with reduced bone parameters during growth, increasing the risk of osteoporosis in old age. Furthermore, muscle mass gains are associated with improved neurodevelopment in the first years of life. Given these negative implications of low muscle mass and strength on health, it is crucial to track muscle mass and strength development from childhood to adolescence. Several body composition techniques are currently available for estimation of muscle mass, all with unique advantages and disadvantages. The value of ultrasound as a technique to measure muscle mass is emerging in pediatric research with potential for translating the research findings to clinical settings. For the assessment of muscle strength, the handgrip strength test has been widely employed but without a standardized protocol. Although further research is needed to define normative data and cut points for the low muscle mass and strength phenotype, the use of such non-invasive medical monitoring is a promising strategy to identify early abnormalities and prevent low muscle mass in adulthood.

Effects of prostate cancer and exercise training on left ventricular function and cardiac and skeletal muscle mass

Prostate cancer was found to reduce cardiac and left ventricle (LV) masses in association with diminished exercise capacity in rats. We tested the hypothesis that exercise training will mitigate prostate cancer-induced cardiac and skeletal muscle atrophy and improve LV function versus sedentary tumor-bearing counterparts. Copenhagen rats ( n = 39; ~5 mo old) were randomized into four groups: exercise-trained tumor-bearing (EXTB) or control (EXCON) and sedentary tumor-bearing (SEDTB) or control (SEDCON). Dunning R-3327 prostate cancer cells were injected orthotopically in 19 of the 39 animals. Treadmill exercise training was performed for 60 min/day for ~30 days. Animals underwent echocardiography to examine ventricle dimensions "Pre-" cancer injection or exercise (PRE) and 15 (Post 1) and 32-35 (Post 2) days after cancer cell injection with tissues collected after Post 2. LV TNF-α and IL-6 concentrations were measured post mortem. Cardiac and LV mass of SEDTB animals were lower than all groups ( P < 0.05). Tumor mass was negatively correlated with LV mass in EXTB (-0.75, P < 0.02) and SEDTB animals (-0.72, P < 0.02). EXCON group had higher stroke volume Post 2 assessment compared with both sedentary groups ( P < 0.05) but not EXTB animals. No difference in LV [IL-6] or [TNF-α] was found between the cancer groups. The current investigation demonstrates prostate cancer, independent of anticancer treatment, significantly reduces cardiac mass and LV mass as well as locomotor muscle masses. However, moderate-intensity exercise training can mitigate cardiac and skeletal muscle atrophy with prostate cancer and preserve the cardiac phenotype (i.e., mass and function) to that of the healthy sedentary group. NEW & NOTEWORTHY This study demonstrates the atrophic effects of prostate cancer on cardiac and skeletal muscle mass independent of anticancer treatment(s) that can be mitigated with moderate-intensity exercise. These findings have important implications for potentially improving the quality of life as well as therapeutic outcomes for patients with prostate cancer.

The regulation of skeletal muscle fatigability and mitochondrial function by chronically elevated interleukin-6

NEW FINDINGS

What is the central question of this study? Interleukin-6 has been associated with muscle mass and metabolism in both physiological and pathological conditions. A causal role for interleukin-6 in the induction of fatigue and disruption of mitochondrial function has not been determined. What is the main finding and its importance? We demonstrate that chronically elevated interleukin-6 increased skeletal muscle fatigability and disrupted mitochondrial content and function independent of changes in fibre type and mass.

ABSTRACT

Interleukin-6 (IL-6) can initiate intracellular signalling in skeletal muscle by binding to the IL-6-receptor and interacting with the transmembrane gp130 protein. Circulating IL-6 has established effects on skeletal muscle mass and metabolism in both physiological and pathological conditions. However, the effects of circulating IL-6 on skeletal muscle function are not well understood. The purpose of this study was to determine whether chronically elevated systemic IL-6 was sufficient to disrupt skeletal muscle force, fatigue and mitochondrial function. Additionally, we examined the role of muscle gp130 signalling during overexpression of IL-6. Systemic IL-6 overexpression for 2 weeks was achieved by electroporation of an IL-6 overexpression plasmid or empty vector into the quadriceps of either C57BL/6 (WT) or skeletal muscle gp130 knockout (KO) male mice. Tibialis anterior muscle in situ functional properties and mitochondrial respiration were determined. Interleukin-6 accelerated in situ skeletal muscle fatigue in the WT, with a 18.5% reduction in force within 90 s of repeated submaximal contractions and a 7% reduction in maximal tetanic force after 5 min. There was no difference between fatigue in the KO and KO+IL-6. Interleukin-6 reduced WT muscle mitochondrial respiratory control ratio by 36% and cytochrome c oxidase activity by 42%. Interleukin-6 had no effect on either KO respiratory control ratio or cytochrome c oxidase activity. Interleukin-6 also had no effect on body weight, muscle mass or tetanic force in either genotype. These results provide evidence that 2 weeks of elevated systemic IL-6 is sufficient to increase skeletal muscle fatigability and decrease muscle mitochondrial content and function, and these effects require muscle gp130 signalling.