Muscle as a paracrine and endocrine organ

Vitamin D combined with whole-body vibration training for the treatment of osteo-sarcopenia: study protocol for a randomized controlled trial

BACKGROUND

Osteo-sarcopenia (OS) has become a global public health problem and a frontier research problem, as a combination of sarcopenia (SP) and osteoporosis (OP) diseases. The clinical performances include muscle weakness, systemic bone pain, standing difficulty, even falls and fractures, etc., which seriously affect the patient's life and work. The pathological mechanism of the OS may be the abnormal metabolism which disrupts the equilibrium stability of the musculoskeletal system. Therefore, this study combined vitamin D (Vit. D) and whole-body vibration training (WBVT) to intervene in subjects of OS, aiming to evaluate the effectiveness and safety of the diagnosis and treatment protocol and to explore the efficacy mechanism.

METHODS

We propose a multicenter, parallel-group clinical trial to evaluate the efficacy and safety of Vit. D combined with WBVT intervention in OS. Subjects who met the inclusion or exclusion criteria and signed the informed consent form would be randomly assigned to the WBVT group, Vit. D group, or WBVT+ Vit. D group. All subjects will be treated for 1 month and followed up after 3 and 6 months. The primary outcomes are lumbar bone mineral density (BMD) and appendicular skeletal muscle mass (ASM) measured by dual-energy X-ray absorptiometry (DXA) and handgrip strength measured by grip strength meter. Secondary outcomes include serum markers of myostatin (MSTN), irisin and bone turnover markers (BTM), SARC-CalF questionnaire, 1-min test question of osteoporosis risk, patient health status (evaluated by the SF-36 health survey), physical performance measurement that includes 5-time chair stand test, 6-m walk, and the short physical performance battery (SPPB).

DISCUSSION

If Vit. D combined with WBVT can well relieve OS symptoms without adverse effects, this protocol may be a new treatment strategy for OS. After therapeutic intervention, if the serum marker MSTN/irisin is significant, both have the potential to become sensitive indicators for screening OS effective drugs and treatments, which also indicates that WBVT combined with Vit. D plays a role in improving OS by regulating MSTN/irisin.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR2400082269 . Registered on March 26, 2024.

Influence of Body Composition Assessed by Computed Tomography on Mortality Risk in Young Women with Breast Cancer

Background/Objectives: Increasing evidence indicates that body composition can significantly influence prognosis in women with breast cancer. However, alterations in body composition, particularly among young women (<40 years), remain largely unknown and underexplored. This study aimed to investigate the relationship of computed tomography (CT)-derived body composition with mortality rates among young women recently diagnosed with breast cancer, identifying the best-correlated cutoff value. Methods: This is a bi-set cohort study with retrospective data collection. Women newly diagnosed with ductal invasive breast cancer, aged 20 to 40 years, treated in reference oncology units were included. Body composition was assessed using CT scans at the third lumbar vertebra (L3) level, including muscle and adipose compartments. The outcome of interest was the incidence of overall mortality. A maximally selected log-rank Cox-derived analysis was employed to assess the cutoffs associated with mortality. Results: A total of 192 women were included before any form of treatment (median age of 35 years, IQ range: 31-37). Overall mortality occurred in 12% of the females. Stages III-IV were the most frequent (69.5%). Patients who died had a significantly lower muscle area index. CT-derived muscle area was inversely associated with mortality. Each 1 cm2/m2 decrease in skeletal muscle index increased the mortality hazard by 9%. Higher values of adiposity compartments were independently associated with higher mortality. Conclusions: Our study highlights the predictive significance of skeletal muscle area and adipose tissue in predicting survival among young women recently diagnosed with breast cancer.

Subacute cadmium exposure changes different metabolic functions, leading to type 1 and 2 diabetes mellitus features in female rats

Cadmium (Cd) is a heavy metal that acts as endocrine disrupting chemical (EDC). Few studies have investigated the effects of Cd exposure on metabolic dysfunctions, such as type 1 and 2 diabetes mellitus (T1DM and T2DM). Thus, we assessed whether subacute Cd exposure at occupational levels causes abnormalities in white adipose tissue (WAT), liver, pancreas, and skeletal muscle. We administered cadmium chloride (CdCl2) (100 ppm in drinking water for 30 days) to female rats and evaluated Cd levels in serum and metabolic organs, morphophysiology, inflammation, oxidative stress, fibrosis, and gene expression. High Cd levels were found in serum, WAT, liver, pancreas, and skeletal muscle. Cd-exposed rats showed low adiposity, dyslipidemia, insulin resistance, systemic inflammation, and oxidative stress compared to controls. Cd exposure reduced adipocyte size, hyperleptinemia, increased cholesterol levels, inflammation, apoptosis and fibrosis in WAT. Cd-exposed rats had increased liver cholesterol levels, insulin receptor beta (IRβ) and peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC1α) expression, karyomegaly, inflammation, and fibrosis. Cd exposure reduced insulin levels and pancreatic islet size and increased inflammation and fibrosis. Cd exposure reduced skeletal muscle fiber diameter and increased IR expression and inflammation. Finally, strong positive correlations were observed between serum, tissue Cd levels, abnormal morphology, tissue inflammation and fibrosis. Thus, these data suggest that subacute Cd exposure impairs WAT, liver, pancreas and skeletal muscle function, leading to T1DM and T2DM features and other complications in female rats.

Effect of Single Session of Swedish Massage on Circulating Levels of Interleukin-6 and Insulin-like Growth Factor 1

Massage therapy increases muscle blood flow and heat, relieving pain, improving immune function, and increasing vagal activity. The mechanisms are unclear. Muscles release cytokines and other peptides called myokines. These myokines exert their effects on different tissues and organs in para-, auto-, and endocrine fashion. The aim of this intervention study was to investigate if massage therapy affects circulating myokine levels. A total of 46 healthy, normal-weight subjects (15 men) aged 18-35 were recruited. Forty-five minutes of massage Swedish therapy was applied to the back and hamstrings. Blood samples via cannula were taken at the baseline, during the massage (30 min), end of the massage (45 min), and 30 min and 1 h after the massage. Interleukin 6 (IL-6) and insulin-like growth factor 1 (IGF-1) were measured as surrogate markers by ELISAs. There was a significant increase in IL-6 from 1.09 pg/mL to 1.85 pg/mL over time (Wilks' Lambda Value 0.545, p < 0.000; repeated measures ANOVA). Pair-wise comparisons showed a significant increase after 1 h of massage. No significant increase was observed in IGF-1 levels. The change in myokine levels was not correlated with muscle mass (p = 0.16, 0.74). The increase in IL-6 suggests that there might be anti-inflammatory effects, affecting glucose and lipid metabolism pathways via IL-6 signaling to muscles, fat tissue, and the liver.

Harnessing immunomodulation to combat sarcopenia: current insights and possible approaches

Sarcopenia is a complex age-associated syndrome of progressive loss of muscle mass and strength. Although this condition is influenced by many factors, age-related changes in immune function including immune cell dynamics, and chronic inflammation contribute to its progression. The complex interplay between the immune system, gut-muscle axis, and autophagy further underscores their important roles in sarcopenia pathogenesis. Immunomodulation has emerged as a promising strategy to counteract sarcopenia. Traditional management approaches to treat sarcopenia including physical exercise and nutritional supplementation, and the emerging technologies of biophysical stimulation demonstrated the importance of immunomodulation and regulation of macrophages and T cells and reduction of chronic inflammation. Treatments to alleviate low-grade inflammation in older adults by modulating gut microbial composition and diversity further combat sarcopenia. Furthermore, some pharmacological interventions, nano-medicine, and cell therapies targeting muscle, gut microbiota, or autophagy present additional avenues for immunomodulation in sarcopenia. This narrative review explores the immunological underpinnings of sarcopenia, elucidating the relationship between the immune system and muscle during ageing. Additionally, the review discusses new areas such as the gut-muscle axis and autophagy, which bridge immune system function and muscle health. Insights into current and potential approaches for sarcopenia management through modulation of the immune system are provided, along with suggestions for future research directions and therapeutic strategies. We aim to guide further investigation into clinical immunological biomarkers and identify indicators for sarcopenia diagnosis and potential treatment targets to combat this condition. We also aim to draw attention to the importance of considering immunomodulation in the clinical management of sarcopenia.

Expression and secretion of SPARC, FGF-21 and DCN in bovine muscle cells: Effects of age and differentiation

Skeletal muscle growth is an economically important trait in the cattle industry. Secreted muscle-derived proteins, referred to as myokines, have important roles in regulating the growth, metabolism, and health of skeletal muscle in human and biomedical research models. Accumulating evidence supports the importance of myokines in skeletal muscle and whole-body health, though little is known about the potential presence and functional significance of these proteins in cattle. This study evaluates and confirms that secreted proteins acidic and rich in cysteine (SPARC), fibroblast growth factor 21 (FGF-21), myostatin (MSTN), and decorin (DCN) are expressed and SPARC, FGF-21, and DCN are secreted by primary bovine satellite cells from 3- (BSC3; n = 3) and 11- (BSC11; n = 3) month -old commercial angus steers. Cells were cultured and collected at zero, 12, 24, and 48 hours to characterize temporal expression and secretion from undifferentiated and differentiated cells. The expression of SPARC was higher in the undifferentiated (p = 0.04) and differentiated (p = 0.07) BSC11 than BSC3. The same was observed with protein secretion from undifferentiated (p <0.0001) BSC11 compared to BSC3. Protein secretion of FGF-21 was higher in undifferentiated BSC11 (p < 0.0001) vs. BSC3. DCN expression was higher in differentiated BSC11 (p = 0.006) vs. BSC3. Comparing undifferentiated vs. differentiated BSC, MSTN expression was higher in differentiated BSC3 (p ≤ 0.001) for 0, 12, and 24 hours and in BSC11 (p ≤ 0.03) for 0, 12, 24, and 48 hours. There is also a change over time for SPARC expression (p ≤ 0.03) in undifferentiated and differentiated BSC and protein secretion (p < 0.0001) in undifferentiated BSC, as well as FGF-21 expression (p = 0.007) in differentiated BSC. This study confirms SPARC, FGF-21, and DCN are secreted, and SPARC, FGF-21, MSTN, and DCN are expressed in primary bovine muscle cells with age and temporal differences.

Bioinformatics and system biology approach to identify potential common pathogenesis for COVID-19 infection and sarcopenia

Sarcopenia is a condition characterized by age-related loss of muscle mass and strength. Increasing evidence suggests that patients with sarcopenia have higher rates of coronavirus 2019 (COVID-19) infection and poorer post-infection outcomes. However, the exact mechanism and connections between the two is unknown. In this study, we used high-throughput data from the GEO database for sarcopenia (GSE111016) and COVID-19 (GSE171110) to identify common differentially expressed genes (DEGs). We conducted GO and KEGG pathway analyses, as well as PPI network analysis on these DEGs. Using seven algorithms from the Cytoscape plug-in cytoHubba, we identified 15 common hub genes. Further analyses included enrichment, PPI interaction, TF-gene and miRNA-gene regulatory networks, gene-disease associations, and drug prediction. Additionally, we evaluated immune cell infiltration with CIBERSORT and assessed the diagnostic accuracy of hub genes for sarcopenia and COVID-19 using ROC curves. In total, we identified 66 DEGs (34 up-regulated and 32 down-regulated) and 15 hub genes associated with sarcopenia and COVID-19. GO and KEGG analyses revealed functions and pathways between the two diseases. TF-genes and TF-miRNA regulatory network suggest that FOXOC1 and hsa-mir-155-5p may be identified as key regulators, while gene-disease analysis showed strong correlations with hub genes in schizophrenia and bipolar disorder. Immune infiltration showed a correlation between the degree of immune infiltration and the level of infiltration of different immune cell subpopulations of hub genes in different datasets. The ROC curves for ALDH1L2 and KLF5 genes demonstrated their potential as diagnostic markers for both sarcopenia and COVID-19. This study suggests that sarcopenia and COVID-19 may share pathogenic pathways, and these pathways and hub genes offer new targets and strategies for early diagnosis, effective treatment, and tailored therapies for sarcopenia patients with COVID-19.

Mustn1 in Skeletal Muscle: A Novel Regulator?

Skeletal muscle is a complex organ essential for locomotion, posture, and metabolic health. This review explores our current knowledge of Mustn1, particularly in the development and function of skeletal muscle. Mustn1 expression originates from Pax7-positive satellite cells in skeletal muscle, peaks during around the third postnatal month, and is crucial for muscle fiber differentiation, fusion, growth, and regeneration. Clinically, Mustn1 expression is potentially linked to muscle-wasting conditions such as muscular dystrophies. Studies have illustrated that Mustn1 responds dynamically to injury and exercise. Notably, ablation of Mustn1 in skeletal muscle affects a broad spectrum of physiological aspects, including glucose metabolism, grip strength, gait, peak contractile strength, and myofiber composition. This review summarizes our current knowledge of Mustn1's role in skeletal muscle and proposes future research directions, with a goal of elucidating the molecular function of this regulatory gene.

The impact of ageing mechanisms on musculoskeletal system diseases in the elderly

Ageing is an inevitable process that affects various tissues and organs of the human body, leading to a series of physiological and pathological changes. Mechanisms such as telomere depletion, stem cell depletion, macrophage dysfunction, and cellular senescence gradually manifest in the body, significantly increasing the incidence of diseases in elderly individuals. These mechanisms interact with each other, profoundly impacting the quality of life of older adults. As the ageing population continues to grow, the burden on the public health system is expected to intensify. Globally, the prevalence of musculoskeletal system diseases in elderly individuals is increasing, resulting in reduced limb mobility and prolonged suffering. This review aims to elucidate the mechanisms of ageing and their interplay while exploring their impact on diseases such as osteoarthritis, osteoporosis, and sarcopenia. By delving into the mechanisms of ageing, further research can be conducted to prevent and mitigate its effects, with the ultimate goal of alleviating the suffering of elderly patients in the future.

A metabolic-dysfunction associated steatotic liver acinus biomimetic induces pancreatic islet dysfunction in a coupled microphysiology system

Preclinical and clinical studies suggest that lipid-induced hepatic insulin resistance is a primary defect that predisposes to dysfunction in pancreatic islets, implicating a perturbed liver-pancreas axis underlying the comorbidity of T2DM and MASLD. To investigate this hypothesis, we developed a human biomimetic microphysiological system (MPS) coupling our vascularized liver acinus MPS (vLAMPS) with primary islets on a chip (PANIS) enabling MASLD progression and islet dysfunction to be quantitatively assessed. The modular design of this system (vLAMPS-PANIS) allows intra-organ and inter-organ dysregulation to be deconvoluted. When compared to normal fasting (NF) conditions, under early metabolic syndrome (EMS) conditions, the standalone vLAMPS exhibited characteristics of early stage MASLD, while no significant differences were observed in the standalone PANIS. In contrast, with EMS, the coupled vLAMPS-PANIS exhibited a perturbed islet-specific secretome and a significantly dysregulated glucose stimulated insulin secretion (GSIS) response implicating direct signaling from the dysregulated liver acinus to the islets. Correlations between several pairs of a vLAMPS-derived and a PANIS-derived secreted factors were significantly altered under EMS, as compared to NF conditions, mechanistically connecting MASLD and T2DM associated hepatic factors with islet-derived GLP-1 synthesis and regulation. Since vLAMPS-PANIS is compatible with patient-specific iPSCs, this platform represents an important step towards addressing patient heterogeneity, identifying complex disease mechanisms, and advancing precision medicine.

Exploring exercise-driven exerkines: unraveling the regulation of metabolism and inflammation

Exercise has many beneficial effects that provide health and metabolic benefits. Signaling molecules are released from organs and tissues in response to exercise stimuli and are widely termed exerkines, which exert influence on a multitude of intricate multi-tissue processes, such as muscle, adipose tissue, pancreas, liver, cardiovascular tissue, kidney, and bone. For the metabolic effect, exerkines regulate the metabolic homeostasis of organisms by increasing glucose uptake and improving fat synthesis. For the anti-inflammatory effect, exerkines positively influence various chronic inflammation-related diseases, such as type 2 diabetes and atherosclerosis. This review highlights the prospective contribution of exerkines in regulating metabolism, augmenting the anti-inflammatory effects, and providing additional advantages associated with exercise. Moreover, a comprehensive overview and analysis of recent advancements are provided in this review, in addition to predicting future applications used as a potential biomarker or therapeutic target to benefit patients with chronic diseases.

Murine Myoblasts Exposed to SYUIQ-5 Acquire Senescence Phenotype and Differentiate into Sarcopenic-Like Myotubes, an In Vitro Study

The musculoskeletal system is one of the most affected organs by aging that correlates well with an accumulation of senescent cells as for other multiple age-related pathologies. The molecular mechanisms underpinning muscle impairment because of senescent cells are still elusive. The availability of in vitro model of skeletal muscle senescence is limited and restricted to a small panel of phenotypic features of these senescent cells in vivo. Here, we developed a new in vitro model of senescent C2C12 mouse myoblasts that, when subjected to differentiation, the resulting myotubes showed sarcopenic features. To induce senescence, we used SYUIQ-5, a quindoline derivative molecule inhibitor of telomerase activity, leading to the expression of several senescent hallmarks in treated myoblasts. They had increased levels of p21 protein accordingly with the observed cell cycle arrest. Furthermore, they had enhanced SA-βgalactosidase enzyme activity and phosphorylation of p53 and histone H2AX. SYUIQ-5 senescent myoblasts had impaired differentiation potential and the resulting myotubes showed increased levels of ATROGIN-1 and MURF1, ubiquitin ligases components responsible for protein degradation, and decreased mitochondria content, typical features of sarcopenic muscles. Myotubes differentiated from senescent myoblasts cultures release increased levels of MYOSTATIN that could affect skeletal muscle cell growth. Overall, our data suggest that a greater burden of senescent muscle cells could contribute to sarcopenia. This study presents a well-defined in vitro model of muscle cell senescence useful for deeper investigation in the aging research field to discover new putative therapeutic targets and senescence biomarkers associated with the aged musculoskeletal system.

Assessment of muscle endocrine function and inflammatory signalling in male school children following a physical activity programme

BACKGROUND & AIMS

Regular and planned physical activity can diminish the risk of numerous illnesses. However, school children and teenagers often exercise intermittently and for brief periods, restricting potential benefits. Furthermore, previous studies mainly focused on body composition, without providing molecular mechanisms elucidating the role of physical activity in muscle tissue and inflammatory signalling. The objective of this study was to determine the effect of a vigorous physical activity intervention on endocrine muscle function and cytokine output in children.

METHODS

103 boys were divided into two groups: control (n = 51, did not perform additional physical activity) and exercise (n = 52, performed vigorous physical activity). Body composition measurements, endocrine muscle function and inflammatory signalling biomarkers were assessed at enrolment and after 6 months of intervention.

RESULTS

No statistical significance was found for fractalkine, oncostatin, EGF, TNF-α and eotaxin. However, LIF, FBAP3, IL-6, FGF21 and IL-15 increased in the exercise group at the end of the protocol, though myostatin got decreased. In contrast, IFN-γ was increased in the exercise group at the beginning and end of the exercise protocol, IL-10 was also increased in this group, IL-1α decreased in the exercise group before and after the exercise protocol, and IP-10 and MCP-1 also decreased in the exercise group.

CONCLUSION

It can be affirmed that a physical activity programme for boys was shown to produce changes in body composition (decreased fat mass, increased lean mass) and in markers of endocrine muscle function and cytokine release. It is possible that these changes, if sustained, could reduce the risk of chronic disease.

Myokines Produced by Cultured Bovine Satellite Cells Harvested from 3- and 11-Month-Old Angus Steers

The myokines interleukin 6 (IL-6), interleukin 15 (IL-15), myonectin (CTRP15), fibronectin type III domain containing protein 5/irisin (FNDC5), and brain-derived neurotrophic factor (BDNF) are associated with skeletal muscle cell proliferation, differentiation, and muscle hypertrophy in biomedical model species. This study evaluated whether these myokines are produced by cultured bovine satellite cells (BSCs) harvested from 3- and 11-month-old commercial black Angus steers and if the expression and secretion of these targets change across 0, 12, 24, and 48 h in vitro. IL-6, IL-15, FNDC5, and BDNF expression were greater (p ≤ 0.05) in the differentiated vs. undifferentiated BSCs at 0, 12, 24, and 48 h. CTRP15 expression was greater (p ≤ 0.03) in the undifferentiated vs. differentiated BSCs at 24 and 48 h. IL-6 and CTRP15 protein from culture media were greater (p ≤ 0.04) in undifferentiated vs. differentiated BSCs at 0, 12, 24, and 48 h. BDNF protein was greater in the media of differentiated vs. undifferentiated BSCs at 0, 12, 24, and 48 h. IL-6, 1L-15, FNDC5, and BDNF are expressed in association with BSC differentiation, and CTRP15 appears to be expressed in association with BSC proliferation. This study also confirms IL-6, IL-15, CTRP15, and BDNF proteins present in media collected from primary cultures of BSCs.

Exercise-induced Musclin determines the fate of fibro-adipogenic progenitors to control muscle homeostasis

The effects of exercise on fibro-adipogenic progenitors (FAPs) are unclear, and the direct molecular link is still unknown. In this study, we reveal that exercise reduces the frequency of FAPs and attenuates collagen deposition and adipose formation in injured or disused muscles through Musclin. Mechanistically, Musclin inhibits FAP proliferation and promotes apoptosis in FAPs by upregulating FILIP1L. Chromatin immunoprecipitation (ChIP)-qPCR confirms that FoxO3a is the transcription factor of FILIP1L. In addition, the Musclin/FILIP1L pathway facilitates the phagocytosis of apoptotic FAPs by macrophages through downregulating the expression of CD47. Genetic ablation of FILIP1L in FAPs abolishes the effects of exercise or Musclin on FAPs and the benefits on the reduction of fibrosis and fatty infiltration. Overall, exercise forms a microenvironment of myokines in muscle and prevents the abnormal accumulation of FAPs in a Musclin/FILIP1L-dependent manner. The administration of exogenous Musclin exerts a therapeutic effect, demonstrating a potential therapeutic approach for muscle atrophy or acute muscle injury.

Sarcopenia using muscle mass prediction model and cognitive impairment: A longitudinal analysis from the English longitudinal study on ageing

BACKGROUND

Literature on the association between sarcopenia and cognitive impairment is largely unclear and mainly limited to non-European populations. Therefore, the aim of this study is to explore if the presence of sarcopenia at the baseline could increase the risk of cognitive impairment in a large cohort of older people participating to the English Longitudinal Study of Ageing (ELSA), over ten years of follow-up.

METHODS

Sarcopenia was diagnosed as having low handgrip strength and low skeletal muscle mass index at the baseline, using a muscle mass prediction model; cognitive function was evaluated in the ELSA through several tests. The results are reported in the whole sample adjusted for potential baseline confounders and after matching sarcopenic and non-sarcopenic participants with a propensity score.

RESULTS

2738 people (mean age: 68.7 years, 54.4% males) were included. During the ten years of follow-up, sarcopenia was associated with significantly lower scores in memory (p < 0.001), verbal fluency (p < 0.001), immediate word recall (p <0.001), delayed word recall (p = 0.018), and in recall summary score (p < 0.001). After adjusting for eight potential confounders, the presence of sarcopenia was significantly associated with poor verbal fluency (odds ratio, OR= 1.417, 95% confidence intervals, CI= 1.181-1.700) and in propensity-score matched analyses (OR=1.272, 95%CI= 1.071- 1.511).

CONCLUSIONS AND IMPLICATIONS

Sarcopenia was found to be associated with a significantly higher incidence of poor cognitive status in a large population of elderly people followed up for 10 years, suggesting it may be an important potential risk factor for dementia.

Interorgan communication networks in the kidney-lung axis

The homeostasis and health of an organism depend on the coordinated interaction of specialized organs, which is regulated by interorgan communication networks of circulating soluble molecules and neuronal connections. Many diseases that seemingly affect one primary organ are really multiorgan diseases, with substantial secondary remote organ complications that underlie a large part of their morbidity and mortality. Acute kidney injury (AKI) frequently occurs in critically ill patients with multiorgan failure and is associated with high mortality, particularly when it occurs together with respiratory failure. Inflammatory lung lesions in patients with kidney failure that could be distinguished from pulmonary oedema due to volume overload were first reported in the 1930s, but have been largely overlooked in clinical settings. A series of studies over the past two decades have elucidated acute and chronic kidney-lung and lung-kidney interorgan communication networks involving various circulating inflammatory cytokines and chemokines, metabolites, uraemic toxins, immune cells and neuro-immune pathways. Further investigations are warranted to understand these clinical entities of high morbidity and mortality, and to develop effective treatments.

Histological and biochemical changes in lymphatic vessels after skeletal muscle injury induced by lengthening contraction in male mice

Lymphatic vessels are actively involved in the recovery process of inflamed tissues. However, the changes in intramuscular lymphatic vessels during inflammation caused by skeletal muscle injury remain unclear. Therefore, the purpose of this study was to clarify the changes in lymphatic vessels after skeletal muscle injury. The left tibialis anterior muscles of male mice were subjected to lengthening contractions (LC) for inducing skeletal muscle injury, and samples were collected on Days 2, 4, and 7 for examining changes in both the skeletal muscles and intramuscular lymphatic vessels. With hematoxylin-eosin staining, the inflammatory response was observed in myofibers on Days 2 and 4 after LC, whereas regeneration of myofibers was found on Day 7 after LC. The number and area of intramuscular lymphatic vessels analyzed by immunohistochemical staining with an antibody against lymphatic vessel endothelial hyaluronan receptor 1 were significantly increased only on Day 4 after LC. Based on the abovementioned results, intramuscular lymphatic vessels undergo morphological changes such as increase under the state of muscle inflammation. This study demonstrated that the morphology of intramuscular lymphatic vessels undergoes significant changes during the initial recovery phase following skeletal muscle injury.

Relationship between skeletal muscle index at the third lumbar vertebra with infection risk and long-term prognosis in patients with acute-on-chronic liver failure

Objective

Infection is a major cause of increased mortality in patients with acute-on-chronic liver failure (ACLF). This study aims to examine the potential correlation of the skeletal muscle index at the third lumbar vertebra (L3-SMI) with infections among ACLF patients and to evaluate its impact on the long-term survival.

Methods

This retrospective study included 126 patients who underwent abdominal computed tomography (CT) and were diagnosed with ACLF at our center between December 2017 and December 2021. L3-SMI was calculated using CT, and the clinical and biochemical data as well as MELD scores were also collected, so as to analyze the relationship between L3-SMI and infections in ACLF patients and the impact on long-term prognosis.

Results

Of the 126 ACLF patients enrolled, 50 had infections. In the multivariate logistic regression analysis, both L3-SMI [odds ratio (OR) = 0.89, 95% confidence interval (CI) = 0.81 - 0.97, P = 0.011] and hepatic encephalopathy (OR = 8.20, 95% CI = 1.70 - 39.59, P = 0.009) were independently associated with the risk of infection development. The overall survival (OS) estimates were obtained using Kaplan-Meier curves, and it was found that patients in the lowest tertile of L3-SMI had significantly lower 3-month, 6-month, 1-year, and 2-year survival rates than those in the highest tertile (P = 0.014; log-rank test).

Conclusion

Low L3-SMI is an independent risk factor for the development of infections and significantly influences the long-term survival in ACLF patients.

Bta-miR-181d and Bta-miR-196a mediated proliferation, differentiation, and apoptosis in Bovine Myogenic Cells

Skeletal muscle is an important component of livestock and poultry organisms. The proliferation and differentiation of myoblasts are highly coordinated processes, which rely on the regulation of miRNA. MiRNAs are widely present in organisms and play roles in various biological processes, including cell proliferation, differentiation, and apoptosis. MiR-181d and miR-196a, identified as tumor suppressors, have been found to be involved in cell proliferation, apoptosis, directed differentiation, and cancer cell invasion. However, their role in beef cattle skeletal muscle metabolism remains unclear. In this study, we discovered that overexpression of bta-miR-181d and bta-miR-196a in Qinchuan cattle myoblasts inhibited proliferation and apoptosis while promoting myogenic differentiation through EDU staining, flow cytometry analysis, immunofluorescence staining, and Western blotting. RNA-seq analysis of differential gene expression revealed that after overexpression of bta-miR-181d and bta-miR-196a, the differentially expressed genes were mainly enriched in the PI3K-Akt and MAPK signaling pathways. Furthermore, the phosphorylation levels of key proteins p-AKT in the PI3K signaling pathway and p-MAPK in the MAPK signaling pathway were significantly decreased after overexpression of bta-miR-181d and bta-miR-196a. Overall, this study provides preliminary evidence that bta-miR-181d and bta-miR-196a may regulate proliferation, apoptosis, and differentiation processes in Qinchuan cattle myoblasts by affecting the phosphorylation status of key proteins in PI3K-Akt and MAPK-ERK signaling pathways.

Multiorgan locked-state model of chronic diseases and systems pharmacology opportunities

With increasing human life expectancy, the global medical burden of chronic diseases is growing. Hence, chronic diseases are a pressing health concern and will continue to be in decades to come. Chronic diseases often involve multiple malfunctioning organs in the body. An imminent question is how interorgan crosstalk contributes to the etiology of chronic diseases. We conceived the locked-state model (LoSM), which illustrates how interorgan communication can give rise to body-wide memory-like properties that 'lock' healthy or pathological conditions. Next, we propose cutting-edge systems biology and artificial intelligence strategies to decipher chronic multiorgan locked states. Finally, we discuss the clinical implications of the LoSM and assess the power of systems-based therapies to dismantle pathological multiorgan locked states while improving treatments for chronic diseases.

Regulation of Satellite Cells Functions during Skeletal Muscle Regeneration: A Critical Step in Physiological and Pathological Conditions

Skeletal muscle regeneration is a complex process involving the generation of new myofibers after trauma, competitive physical activity, or disease. In this context, adult skeletal muscle stem cells, also known as satellite cells (SCs), play a crucial role in regulating muscle tissue homeostasis and activating regeneration. Alterations in their number or function have been associated with various pathological conditions. The main factors involved in the dysregulation of SCs' activity are inflammation, oxidative stress, and fibrosis. This review critically summarizes the current knowledge on the role of SCs in skeletal muscle regeneration. It examines the changes in the activity of SCs in three of the most common and severe muscle disorders: sarcopenia, muscular dystrophy, and cancer cachexia. Understanding the molecular mechanisms involved in their dysregulations is essential for improving current treatments, such as exercise, and developing personalized approaches to reactivate SCs.

Rehabilitation Training after Spinal Cord Injury Affects Brain Structure and Function: From Mechanisms to Methods

Spinal cord injury (SCI) is a serious neurological insult that disrupts the ascending and descending neural pathways between the peripheral nerves and the brain, leading to not only functional deficits in the injured area and below the level of the lesion but also morphological, structural, and functional reorganization of the brain. These changes introduce new challenges and uncertainties into the treatment of SCI. Rehabilitation training, a clinical intervention designed to promote functional recovery after spinal cord and brain injuries, has been reported to promote activation and functional reorganization of the cerebral cortex through multiple physiological mechanisms. In this review, we evaluate the potential mechanisms of exercise that affect the brain structure and function, as well as the rehabilitation training process for the brain after SCI. Additionally, we compare and discuss the principles, effects, and future directions of several rehabilitation training methods that facilitate cerebral cortex activation and recovery after SCI. Understanding the regulatory role of rehabilitation training at the supraspinal center is of great significance for clinicians to develop SCI treatment strategies and optimize rehabilitation plans.

GRAF1 Regulates Brown and Beige Adipose Differentiation and Function

Adipose tissue, which is crucial for the regulation of energy within the body, contains both white and brown adipocytes. White adipose tissue (WAT) primarily stores energy, while brown adipose tissue (BAT) plays a critical role in energy dissipation as heat, offering potential for therapies aimed at enhancing metabolic health. Regulation of the RhoA/ROCK pathway is crucial for appropriate specification, differentiation and maturation of both white and brown adipocytes. However, our knowledge of how this pathway is controlled within specific adipose depots remains unclear, and to date a RhoA regulator that selectively controls adipocyte browning has not been identified. Our study shows that expression of GRAF1, a RhoGAP highly expressed in metabolically active tissues, closely correlates with brown adipocyte differentiation in culture and in vivo. Mice with either global or adipocyte-specific GRAF1 deficiency exhibit impaired BAT maturation, reduced capacity for WAT browning, and compromised cold-induced thermogenesis. Moreover, defects in differentiation of mouse or human GRAF1-deficient brown preadipocytes can be rescued by treatment with a Rho kinase inhibitor. Collectively, these studies indicate that GRAF1 can selectively induce brown and beige adipocyte differentiation and suggest that manipulating GRAF1 activity may hold promise for the future treatment of diseases related to metabolic dysfunction.

Mustn1 ablation in skeletal muscle results in functional alterations

Mustn1, a gene expressed exclusively in the musculoskeletal system, was shown in previous in vitro studies to be a key regulator of myogenic differentiation and myofusion. Other studies also showed Mustn1 expression associated with skeletal muscle development and hypertrophy. However, its specific role in skeletal muscle function remains unclear. This study sought to investigate the effects of Mustn1 in a conditional knockout (KO) mouse model in Pax7 positive skeletal muscle satellite cells. Specifically, we investigated the potential effects of Mustn1 on myogenic gene expression, grip strength, alterations in gait, ex vivo investigations of isolated skeletal muscle isometric contractions, and potential changes in the composition of muscle fiber types. Results indicate that Mustn1 KO mice did not present any substantial phenotypic changes or significant variations in genes related to myogenic differentiation and fusion. However, an approximately 10% decrease in overall grip strength was observed in the 2-month-old KO mice in comparison to the control wild type (WT), but this decrease was not significant when normalized by weight. KO mice also generated approximately 8% higher vertical force than WT at 4 months in the hindlimb. Ex vivo experiments revealed decreases in about 20 to 50% in skeletal muscle contractions and about 10%-20% fatigue in soleus of both 2- and 4-month-old KO mice, respectively. Lastly, immunofluorescent analyses showed a persistent increase of Type IIb fibers up to 15-fold in the KO mice while Type I fibers decreased about 20% and 30% at both 2 and 4 months, respectively. These findings suggest a potential adaptive or compensatory mechanism following Mustn1 loss, as well as hinting at an association between Mustn1 and muscle fiber typing. Collectively, Mustn1's complex roles in skeletal muscle physiology requires further research, particularly in terms of understanding the potential role of Mustn1 in muscle repair and regeneration, as well as with influence of exercise. Collectively, these will offer valuable insights into Mustn1's key biological functions and regulatory pathways.

Physical activity, physical frailty and depressive symptoms among Chinese male and female older adults: do different indicators make a difference?

Objectives

Older adults become more inactive and frailer with aging. Physical status is closely linked to mental health, but it is unclear which physical indicator is more strongly associated with depressive symptoms in older adults. The present study aimed to compare relationships between self-reported physical activity, physical frailty (muscle mass, muscle strength, and gait ability) and depressive symptoms in community male and female older adults.

Methods

A total of 1,180 adults aged 60 years and older were recruited to participate in this study from a Chinese community receiving annual check-up service from September 2018 to May 2019. Physical activity was assessed by the International Physical Activity Questionnaire (IPAQ). The Bio-electrical Impedance Analyzer was used to determine the muscle mass. As the indicators of muscle function, grip strength and gait ability were assessed by the dynamometer and Timed Up and Go Test (TUGT), respectively. The 15-item version of Geriatric Depression Scale (GDS-15) was used to examine depressive symptoms. Demographic variables, health status and sleep quality were collected using questionnaire.

Results

11.8% men and 11.9% women reported depressive symptoms. Logistic regression showed that depressive symptoms was associated with low grip strength (OR = 2.42, 95% CI: 1.04-5.63), slow gait ability (OR = 3.60, 95% CI: 1.28-10.13) in older males, and associated with low level of self-reported physical activity (OR = 3.85, 95% CI: 2.00-7.42) in older females. No significant association was found between muscle mass and depressive symptoms.

Conclusion

There were gender differences in the relationship between physical activity, physical frailty, and depressive symptoms. Grip strength and gait ability may be a better indicator of frailty for predicting depressive symptoms in older men while physical activity may be useful in predicting depressive symptoms in older women.

Postnatal skeletal muscle myogenesis governed by signal transduction networks: MAPKs and PI3K-Akt control multiple steps

Skeletal muscle myogenesis represents one of the most intensively and extensively examined systems of cell differentiation, tissue formation, and regeneration. Muscle regeneration provides an in vivo model system of postnatal myogenesis. It comprises multiple steps including muscle stem cell (or satellite cell) quiescence, activation, migration, myogenic determination, myoblast proliferation, myocyte differentiation, myofiber maturation, and hypertrophy. A variety of extracellular signaling and subsequent intracellular signal transduction pathways or networks govern the individual steps of postnatal myogenesis. Among them, MAPK pathways (the ERK, JNK, p38 MAPK, and ERK5 pathways) and PI3K-Akt signaling regulate multiple steps of myogenesis. Ca2+, cytokine, and Wnt signaling also participate in several myogenesis steps. These signaling pathways often control cell cycle regulatory proteins or the muscle-specific MyoD family and the MEF2 family of transcription factors. This article comprehensively reviews molecular mechanisms of the individual steps of postnatal skeletal muscle myogenesis by focusing on signal transduction pathways or networks. Nevertheless, no or only a partial signaling molecules or pathways have been identified in some responses during myogenesis. The elucidation of these unidentified signaling molecules and pathways leads to an extensive understanding of the molecular mechanisms of myogenesis.

Understanding the Consequences of Fatty Bone and Fatty Muscle: How the Osteosarcopenic Adiposity Phenotype Uncovers the Deterioration of Body Composition

Adiposity is central to aging and several chronic diseases. Adiposity encompasses not just the excess adipose tissue but also body fat redistribution, fat infiltration, hypertrophy of adipocytes, and the shifting of mesenchymal stem cell commitment to adipogenesis. Bone marrow adipose tissue expansion, inflammatory adipokines, and adipocyte-derived extracellular vesicles are central to the development of osteopenic adiposity. Adipose tissue infiltration and local adipogenesis within the muscle are critical in developing sarcopenic adiposity and subsequent poorer functional outcomes. Ultimately, osteosarcopenic adiposity syndrome is the result of all the processes noted above: fat infiltration and adipocyte expansion and redistribution within the bone, muscle, and adipose tissues, resulting in bone loss, muscle mass/strength loss, deteriorated adipose tissue, and subsequent functional decline. Increased fat tissue, typically referred to as obesity and expressed by body mass index (the latter often used inadequately), is now occurring in younger age groups, suggesting people will live longer with the negative effects of adiposity. This review discusses the role of adiposity in the deterioration of bone and muscle, as well as adipose tissue itself. It reveals how considering and including adiposity in the definition and diagnosis of osteopenic adiposity, sarcopenic adiposity, and osteosarcopenic adiposity will help in better understanding the pathophysiology of each and accelerate possible therapies and prevention approaches for both relatively healthy individuals or those with chronic disease.

Exercise-induced modulation of Interferon-signature: a therapeutic route toward management of Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is a multisystemic autoimmune disorder characterized by flares-ups/remissions with a complex clinical picture related to disease severity and organ/tissue injury, which, if left untreated, may result in permanent damage. Enhanced fatigue and pain perception, worsened quality of life (QoL) and outcome are constant, albeit symptoms may differ. An aberrant SLE immunoprofiling, note as "interferon (IFN)α-signature", is acknowledged to break immunotolerance. Recently, a deregulated "IFNγ-signature" is suggested to silently precede/trigger IFNα profile before clinical manifestations. IFNα- and IFNγ-over-signaling merge in cytokine/chemokine overexpression exacerbating autoimmunity. Remission achievement and QoL improvement are the main goals. The current therapy (i.e., corticosteroids, immunosuppressants) aims to downregulate immune over-response. Exercise could be a safe treatment due to its ever-emerging ability to shape and re-balance immune system without harmful side-effects; in addition, it improves cardiorespiratory capacity and musculoskeletal strength/power, usually impaired in SLE. Nevertheless, exercise is not yet included in SLE care plans. Furthermore, due to the fear to worsening pain/fatigue, SLE subjects experience kinesiophobia and sedentary lifestyle, worsening physical health. Training SLE patients to exercise is mandatory to fight inactive behavior and ameliorate health. This review aims to focus the attention on the role of exercise as a non-pharmacological therapy in SLE, considering its ability to mitigate IFN-signature and rebalance (auto)immune response. To this purpose, the significance of IFNα- and IFNγ-signaling in SLE etiopathogenesis will be addressed first and discussed thereafter as biotarget of exercise. Comments are addressed on the need to make aware all SLE care professional figures to promote exercise for health patients.

Arsenic disrupts extracellular vesicle-mediated signaling in regenerating myofibers

Chronic exposure to environmental arsenic is a public health crisis affecting hundreds of millions of individuals worldwide. Though arsenic is known to contribute to many pathologies and diseases, including cancers, cardiovascular and pulmonary diseases, and neurological impairment, the mechanisms for arsenic-promoted disease remain unresolved. This is especially true for arsenic impacts on skeletal muscle function and metabolism, despite the crucial role that skeletal muscle health plays in maintaining cardiovascular health, systemic homeostasis, and cognition. A barrier to researching this area is the challenge of interrogating muscle cell-specific effects in biologically relevant models. Ex vivo studies investigating mechanisms for muscle-specific responses to arsenic or other environmental contaminants primarily utilize traditional 2-dimensional culture models that cannot elucidate effects on muscle physiology or function. Therefore, we developed a contractile 3-dimensional muscle construct model-composed of primary mouse muscle progenitor cells differentiated in a hydrogel matrix-to study arsenic exposure impacts on skeletal muscle regeneration. Muscle constructs exposed to low-dose (50 nM) arsenic exhibited reduced strength and myofiber diameter following recovery from muscle injury. These effects were attributable to dysfunctional paracrine signaling mediated by extracellular vesicles (EVs) released from muscle cells. Specifically, we found that EVs collected from arsenic-exposed muscle constructs recapitulated the inhibitory effects of direct arsenic exposure on myofiber regeneration. In addition, muscle constructs treated with EVs isolated from muscles of arsenic-exposed mice displayed significantly decreased strength. Our findings highlight a novel model for muscle toxicity research and uncover a mechanism of arsenic-induced muscle dysfunction by the disruption of EV-mediated intercellular communication.

Causal relationship between sarcopenia and osteoarthritis: a bi-directional two-sample mendelian randomized study

BACKGROUND

Previous studies have shown that osteoarthritis (OA) and sarcopenia (SP) are closely related to each other, but the causal relationships between them have not been established. The aim of this study was to investigate the causal associations between OA and SP via a bi-directional Mendelian randomization (MR) approach.

METHODS

A bi-directional two-sample MR was adopted to research the causal relationship between SP and OA. The instrumental variables for SP and four types of OA: KOA, HOA, total knee replacement (TKR) and total hip replacement (THR) were derived from published large genome-wide association studies (GWAS). The inverse variance weighted (IVW), MR-Egger and weighted median estimator (WME) methods were used to estimate bi-directional causal effects.

RESULTS

Low grip strength (GS) did not have a causal effect on four types of OA (KOA: OR = 1.205, 95% CI 0.837-1.734, p = 0.316; HOA: OR = 1.090, 95% CI 0.924-1.609, p = 0.307; TKR: OR = 1.190, 95% CI 1.084-1.307, p = 0.058; THR: OR = 1.035, 95% CI 0.792-1.353, p = 0.798), while appendicular lean mass (ALM) had a causal effect on four types of OA (KOA: OR = 1.104, 95% CI 1.041-1.171, p = 0.001; HOA: OR = 1.151, 95% CI 1.071-1.237, p < 0.001; TKR: OR = 1.114, 95% CI 1.007-1.232, p < 0.001; THR: OR = 1.203, 95% CI 1.099-1.316, p < 0.001). In the reverse direction, KOA or HOA did not have a significant causal effect on both GS and ALM (KOA-GS: OR = 1.077, 95% CI 0.886-1.309, p = 0.458; KOA-ALM: Beta = 0.004, p = 0.892; HOA-GS: OR = 1.038, 95% CI 0.981-1.099, p = 0.209; HOA-ALM: Beta = - 0.017, p = 0.196; TKR-GS: OR = 0.999, 95% CI 0.739-1.351, p = 0.997; TKR-ALM: Beta = 0.018, p = 0.501; THR-GS: OR = 1.037, 95% CI 0.978-1.101, p = 0.222; THR-ALM: Beta = - 0.023, p = 0.081).

CONCLUSIONS

The present study suggests that SP may have a causal effect on OA through changes in muscle composition rather than muscle strength, while little evidence was provided for the causal effect of OA on SP.

Inflammation o'clock: interactions of circadian rhythms with inflammation-induced skeletal muscle atrophy

Circadian rhythms are ∼24 h cycles evident in behaviour, physiology and metabolism. The molecular mechanism directing circadian rhythms is the circadian clock, which is composed of an interactive network of transcription-translation feedback loops. The core clock genes include Bmal1, Clock, Rev-erbα/β, Per and Cry. In addition to keeping time, the core clock regulates a daily programme of gene expression that is important for overall cell homeostasis. The circadian clock mechanism is present in all cells, including skeletal muscle fibres, and disruption of the muscle clock is associated with changes in muscle phenotype and function. Skeletal muscle atrophy is largely associated with a lower quality of life, frailty and reduced lifespan. Physiological and genetic modification of the core clock mechanism yields immune dysfunction, alters inflammatory factor expression and secretion and is associated with skeletal muscle atrophy in multiple conditions, such as ageing and cancer cachexia. Here, we summarize the possible interplay between the circadian clock modulation of immune cells, systemic inflammatory status and skeletal muscle atrophy in chronic inflammatory conditions. Although there is a clear disruption of circadian clocks in various models of atrophy, the mechanism behind such alterations remains unknown. Understanding the modulatory potential of muscle and immune circadian clocks in inflammation and skeletal muscle health is essential for the development of therapeutic strategies to protect skeletal muscle mass and function of patients with chronic inflammation.

Use of Chinese Herbal Medicine Was Related to Lower Risk of Osteoporotic Fracture in Sarcopenia Patients: Evidence from Population-Based Health Claims

Introduction

With population aging, sarcopenia and its accompanying risk of osteoporotic fracture has drawn increased attention. Nowadays, while Chinese herbal medicine (CHM) is often used as complementary therapy for many medical conditions, its effect against likelihood of osteoporotic fracture among sarcopenia subjects was not fully elucidated yet. We therefore conducted a population-level study to compare osteoporotic fracture risk for sarcopenia persons with or without CHM use.

Methods

Using the patient record from a nationwide insurance database, we recruited persons with newly diagnosed sarcopenia and simultaneously free of osteoporotic fracture between 2000 and 2010. Propensity score matching was then applied to randomly select sets of CHM users and non-CHM users. All of them were tracked until end of 2013 to measure the incidence and adjusted hazard ratios (HRs) for new new-onset fracture in multivariable Cox proportional hazards model.

Results

Compared to non-CHM users, the CHM users indeed had a lower incidence of osteoporotic fracture (121.22 vs 156.61 per 1000 person-years). Use of CHM correlated significantly with a lower fracture likelihood after adjusting for potential covariates, and those receiving CHM treatment for more than two years experienced a remarkably lower risk by 73%. Uses of several herbal formulae were correlated to reduced risk of osteoporotic fracture, such as Caulis Spatholobi, Xuduan, Duzhong, Danshen, Shu-Jing-Huo-Xue-Tang, Du-Huo-Ji-Sheng-Tang, Shao-Yao-Gan-Cao-Tang, and Shen-Tong-Zhu-Yu -Tang.

Conclusion

Our study depicted that cumulative CHM exposure was inversely associated with osteoporotic fracture risk in a duration-dependent manner, implying that CHM treatment may be embraced as routine care in preventing incident osteoporotic fracture.

Low Muscle and High Fat Percentages Are Associated with Low Natural Killer Cell Activity: A Cross-Sectional Study

This study aimed to investigate whether body fat and muscle percentages are associated with natural killer cell activity (NKA). This was a cross-sectional study, conducted on 8058 subjects in a medical center in Korea. The association between the muscle and fat percentage tertiles and a low NKA, defined as an interferon-gamma level lower than 500 pg/mL, was assessed. In both men and women, the muscle mass and muscle percentage were significantly low in participants with a low NKA, whereas the fat percentage, white blood cell count, and C-reactive protein (CRP) level were significantly high in those with a low NKA. Compared with the lowest muscle percentage tertile as a reference, the fully adjusted odd ratios (ORs) (95% confidence intervals (CIs)) for a low NKA were significantly lower in T2 (OR: 0.69; 95% CI: 0.55-0.86) and T3 (OR: 0.74; 95% CI: 0.57-0.95) of men, and T3 (OR: 0.76; 95% CI: 0.59-0.99) of women. Compared with the lowest fat percentage tertile as a reference, the fully adjusted OR was significantly higher in T3 of men (OR: 1.31; 95% CI: 1.01-1.69). A high muscle percentage was significantly inversely associated with a low NKA in men and women, whereas a high fat percentage was significantly associated with a low NKA in men.

The muscle-enriched myokine Musclin impairs beige fat thermogenesis and systemic energy homeostasis via Tfr1/PKA signaling in male mice

Skeletal muscle and thermogenic adipose tissue are both critical for the maintenance of body temperature in mammals. However, whether these two tissues are interconnected to modulate thermogenesis and metabolic homeostasis in response to thermal stress remains inconclusive. Here, we report that human and mouse obesity is associated with elevated Musclin levels in both muscle and circulation. Intriguingly, muscle expression of Musclin is markedly increased or decreased when the male mice are housed in thermoneutral or chronic cool conditions, respectively. Beige fat is then identified as the primary site of Musclin action. Muscle-transgenic or AAV-mediated overexpression of Musclin attenuates beige fat thermogenesis, thereby exacerbating diet-induced obesity and metabolic disorders in male mice. Conversely, Musclin inactivation by muscle-specific ablation or neutralizing antibody treatment promotes beige fat thermogenesis and improves metabolic homeostasis in male mice. Mechanistically, Musclin binds to transferrin receptor 1 (Tfr1) and antagonizes Tfr1-mediated cAMP/PKA-dependent thermogenic induction in beige adipocytes. This work defines the temperature-sensitive myokine Musclin as a negative regulator of adipose thermogenesis that exacerbates the deterioration of metabolic health in obese male mice and thus provides a framework for the therapeutic targeting of this endocrine pathway.

CRISPRa-based activation of Fgf21 and Fndc5 ameliorates obesity by promoting adipocytes browning

BACKGROUND

Skeletal muscle-secreted myokines widely participate in lipids metabolism through autocrine, paracrine and endocrine actions. The myokines represented by FGF21 and Irisin can promote the browning of adipocytes and serve as promising targets for treating obesity. Although recombinant myokines replacement therapy and AAV (adeno-associated virus)-based myokines overexpression have shown a definite effect in ameliorating obesity, novel myokine activation strategies with higher efficacy and safety are still in pressing need. This study aimed to evaluate the therapeutic potential of a novel CRISPR-based myokines activation strategy in obesity treatments.

METHODS

In this study, we used lentivirus and a single AAV vector containing dCas9-VP64 with a single-guide RNA to selectively activate Fgf21 and Fndc5 expression in skeletal muscles both in vitro and in vivo. The activation efficacy of the CRISPRa system was determined by qRT-PCR, Western blotting and ELISA. The treatment effect of CRISPR-based myokines activation was tested in 3T3-L1-derived adipocytes and diet-induced obese (DIO) mice (male C57BL/6 mice, induced at 6-week-old for 10 weeks).

RESULTS

The virus upregulates myokines expression in both mRNA and protein levels of muscle cells in vitro and in vivo. Myokines secreted by muscle cells promoted browning of 3T3-L1-derived adipocytes. In vivo activation of myokines by AAVs can reduce body weight and fat mass, increase the adipocytes browning and improve glucose tolerance and insulin sensitivity in DIO mice.

CONCLUSIONS

Our study provides a novel CRISPR-based myokines activation strategy that can ameliorate obesity by promoting adipocytes browning.

[Paracrine and endocrine functions of muscles]

BACKGROUND

Myokines discharged from working muscles are intensively researched in view of rising importance of preventive and secondary preventive effects of the autocrine, paracrine and endocrine functions.

OBJECTIVES

Recording of the current state of knowledge on the paracrine and endocrine effects of myokines and evaluation of training measures to optimize myokine concentration.

METHOD

A selective database-driven literature search was carried out on myostatin, interleukin-6 (IL-6), interleukin-15 (IL-15), irisin, cathepsin B, brain-derived neurotrophic factor (BDNF), meteorin-like and kynurenine for the period 2011 until June 2021. The paracrine and endocrine effects of the myokines are analyzed. Their release after acute physical stress and training is described.

RESULTS

IL-6 and IL-15 act in lipid metabolism and carbohydrate metabolism, IL-6 also in the brain and immune system. Irisin produces a conversion of white to brown adipose tissue ("browning"), so does meteorin-like. Cathepsin B has a central effect. Kynurenine acts indirectly via kynurenic acid in the brain. The secretion of myokines depends on the intensity of physical stress and is modified by training. Prevention of vascular and neurologic diseases, cognitive enhancement and increased immunological function can be reached by setting free myokines during physical activity. Therapeutical use by technologically modified myokines is proposed in metabolic and neurological diseases, immobilization and sarcopenia.

CONCLUSIONS

The current research situation on myokines gives reason to recommend regular muscular activity in addition to the previously evidence-based benefits of sport in order to achieve preventive and therapeutic effects.

IntiCom-DB: A Manually Curated Database of Inter-Tissue Communication Molecules and Their Communication Routes

Inter-tissue communication (ITC) is critical for maintaining the physiological functions of multiple tissues and is closely related to the onset and development of various complex diseases. Nevertheless, there is no well-organized data resource for known ITC molecules with explicit ITC routes from source tissues to target tissues. To address this issue, in this work, we manually reviewed nearly 190,000 publications and identified 1408 experimentally supported ITC entries in which the ITC molecules, their communication routes, and their functional annotations were included. To facilitate our work, these curated ITC entries were incorporated into a user-friendly database named IntiCom-DB. This database also enables visualization of the expression abundances of ITC proteins and their interaction partners. Finally, bioinformatics analyses on these data revealed common biological characteristics of the ITC molecules. For example, tissue specificity scores of ITC molecules at the protein level are often higher than those at the mRNA level in the target tissues. Moreover, the ITC molecules and their interaction partners are more abundant in both the source tissues and the target tissues. IntiCom-DB is freely available as an online database. As the first comprehensive database of ITC molecules with explicit ITC routes to the best of our knowledge, we hope that IntiCom-DB will benefit future ITC-related studies.

SGLT2 inhibitor empagliflozin promotes revascularization in diabetic mouse hindlimb ischemia by inhibiting ferroptosis

Gliflozins are known as SGLT2 inhibitors, which are used to treat diabetic patients by inhibiting glucose reabsorption in kidney proximal tubules. Recent studies show that gliflozins may exert other effects independent of SGLT2 pathways. In this study we investigated their effects on skeletal muscle cell viability and paracrine function, which were crucial for promoting revascularization in diabetic hindlimb ischemia (HLI). We showed that treatment with empagliflozin (0.1-40 μM) dose-dependently increased high glucose (25 mM)-impaired viability of skeletal muscle C2C12 cells. Canagliflozin, dapagliflozin, ertugliflozin, ipragliflozin and tofogliflozin exerted similar protective effects on skeletal muscle cells cultured under the hyperglycemic condition. Transcriptomic analysis revealed an enrichment of pathways related to ferroptosis in empagliflozin-treated C2C12 cells. We further demonstrated that empagliflozin and other gliflozins (10 μM) restored GPX4 expression in high glucose-treated C2C12 cells, thereby suppressing ferroptosis and promoting cell viability. Empagliflozin (10 μM) also markedly enhanced the proliferation and migration of blood vessel-forming cells by promoting paracrine function of skeletal muscle C2C12 cells. In diabetic HLI mice, injection of empagliflozin into the gastrocnemius muscle of the left hindlimb (10 mg/kg, every 3 days for 21 days) significantly enhanced revascularization and blood perfusion recovery. Collectively, these results reveal a novel effect of empagliflozin, a clinical hypoglycemic gliflozin drug, in inhibiting ferroptosis and enhancing skeletal muscle cell survival and paracrine function under hyperglycemic condition via restoring the expression of GPX4. This study highlights the potential of intramuscular injection of empagliflozin for treating diabetic HLI.

[Relationship between skeletal muscle mass index and metabolic phenotypes of obesity in adolescents]

OBJECTIVES

To study the relationship between skeletal muscle mass index (SMI) and metabolic phenotypes of obesity in adolescents, and to provide a basis for the prevention and control of adolescent obesity and related metabolic diseases.

METHODS

A total of 1 352 adolescents aged 12 to 18 years were randomly selected by stratified cluster sampling in Yinchuan City from October 2017 to September 2020, and they were surveyed using questionnaires, physical measurements, body composition measurements, and laboratory tests. According to the diagnostic criteria for metabolic abnormalities and the definition of obesity based on the body mass index, the subjects were divided into four metabolic phenotypes: metabolically healthy normal weight, metabolically healthy obesity, metabolically unhealthy normal weight, and metabolically unhealthy obesity. The association between SMI and the metabolic phenotypes was analyzed using multivariate logistic regression.

RESULTS

The SMI level in the metabolically unhealthy normal weight, metabolically healthy obesity, and metabolically unhealthy obesity groups was lower than that in the metabolically healthy normal weight group (P<0.001). Multivariate logistic regression analysis showed that after adjusting for gender and age, a higher SMI level was a protective factors for adolescents to develop metabolic unhealthy normal weight, metabolically healthy obesity, and metabolically unhealthy obesity phenotypes (OR=0.74, 0.60, and 0.54, respectively; P<0.001).

CONCLUSIONS

Increasing SMI can reduce the risk of the development of metabolic unhealthy/obesity.

Mustn1 ablation in skeletal muscle results in increased glucose tolerance concomitant with upregulated GLUT expression in male mice

Glucose homeostasis is closely regulated to maintain energy requirements of vital organs and skeletal muscle plays a crucial role in this process. Mustn1 is expressed during embryonic and postnatal skeletal muscle development and its function has been implicated in myogenic differentiation and myofusion. Whether Mustn1 plays a role in glucose homeostasis in anyway remains largely unknown. As such, we deleted Mustn1 in skeletal muscle using a conditional knockout (KO) mouse approach. KO mice did not reveal any specific gross phenotypic alterations in skeletal muscle. However, intraperitoneal glucose tolerance testing (IPGTT) revealed that 2-month-old male KO mice had significantly lower glycemia than their littermate wild type (WT) controls. These findings coincided with mRNA changes in genes known to be involved in glucose metabolism, tolerance, and insulin sensitivity; 2-month-old male KO mice had significantly higher expression of GLUT1 and GLUT10 transporters, MUP-1 while OSTN expression was lower. These differences in glycemia and gene expression were statistically insignificant after 4 months. Identical experiments in female KO and WT control mice did not indicate any differences at any age. Our results suggest a link between Mustn1 expression and glucose homeostasis during a restricted period of skeletal muscle development/maturation. While this is an observational study, Mustn1's relationship to glucose homeostasis appears to be more complex with a possible connection to other key proteins such as GLUTs, MUP-1, and OSTN. Additionally, our data indicate temporal and sex differences. Lastly, our findings strengthen the notion that Mustn1 plays a role in the metabolic capacity of skeletal muscle.

Rheumatoid sarcopenia: loss of skeletal muscle strength and mass in rheumatoid arthritis

Sarcopenia, a disorder that involves the generalized loss of skeletal muscle strength and mass, was formally recognized as a disease by its inclusion in the International Classification of Diseases in 2016. Sarcopenia typically affects older people, but younger individuals with chronic disease are also at risk. The risk of sarcopenia is high (with a prevalence of ≥25%) in individuals with rheumatoid arthritis (RA), and this rheumatoid sarcopenia is associated with increased likelihood of falls, fractures and physical disability, in addition to the burden of joint inflammation and damage. Chronic inflammation mediated by cytokines such as TNF, IL-6 and IFNγ contributes to aberrant muscle homeostasis (for instance, by exacerbating muscle protein breakdown), and results from transcriptomic studies have identified dysfunction of muscle stem cells and metabolism in RA. Progressive resistance exercise is an effective therapy for rheumatoid sarcopenia but it can be challenging or unsuitable for some individuals. The unmet need for anti-sarcopenia pharmacotherapies is great, both for people with RA and for otherwise healthy older adults.

Myokines: Crosstalk and Consequences on Liver Physiopathology

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease mainly characterized by the hepatic accumulation of lipid inducing a deregulation of β-oxidation. Its advanced form is non-alcoholic steatohepatitis (NASH), which, in addition to lipid accumulation, induces hepatocellular damage, oxidative stress and fibrosis that can progress to cirrhosis and to its final stage: hepatocellular carcinoma (HCC). To date, no specific therapeutic treatment exists. The implications of organ crosstalk have been highlighted in many metabolic disorders, such as diabetes, metabolic-associated liver diseases and obesity. Skeletal muscle, in addition to its role as a reservoir and consumer of energy and carbohydrate metabolism, is involved in this inter-organs’ communication through different secreted products: myokines, exosomes and enzymes, for example. Interestingly, resistance exercise has been shown to have a beneficial impact on different metabolic pathways, such as lipid oxidation in different organs through their secreted products. In this review, we will mainly focus on myokines and their effects on non-alcoholic fatty liver disease, and their complication: non-alcoholic steatohepatitis and HCC.

Neuromedin U regulates food intake of Siberian sturgeon through the modulation of central and peripheral appetite factors

Neuromedin U (NMU) has a critical function on the regulation of food intake in mammals, while the information is little in teleost. To investigate the function of NMU on appetite regulation of Siberian sturgeon (Acipenser baerii), this study first cloned nmu cDNA sequence that encoded 154 amino acids including NMU-25 peptide. Besides, the results showed that nmu mRNA was widely distributed in various tissues especially in the hypothalamus and telencephalon. The results of nutritional status (pre-feeding and post-feeding, fasting and re-feeding) experiments showed that nmu mRNA expression was significantly decreased at 1 and 3 h after feeding in different brain regions. Similarly, after feeding, the expression of nmu significantly decreased in peripheral tissues. Moreover, nmu expression in the hypothalamus was significantly increased after fasting 1 d, but decreased after fasting 17 d, which was significantly reversed after re-feeding. However, other brain regions like telencephalon and peripheral tissues like oesophagus, intestinum valvula and liver have different change patterns. Further study showed that acute i.c.v. and i.p. injection of NMU and chronic i.p. injection of NMU significantly reduced the food intake in a dose-dependent mode. In addition, the expressions of several critical appetite factors (nmu, aplein, cart, cck, ghrelin, npy, nucb2, pyy and ucn3) were significantly affected by acute NMU-25 administration in the hypothalamus, intestinum valvula and liver. These results indicate that NMU-25 has the anorexigenic function on food intake by affecting different appetite factors in Siberian sturgeon, which provides a foundation for further exploring the appetite regulation networks in fish.

Salidroside facilitates therapeutic angiogenesis in diabetic hindlimb ischemia by inhibiting ferroptosis

Hindlimb ischemia (HLI), in which blood perfusion to the hindlimb is obstructed, is one of the major complications of diabetes. Skeletal muscle cells are crucial for revascularization as they can secrete various angiogenic factors; however, hyperglycemia impairs their viability and subsequently their angiogenic potential. Salidroside can promote skeletal muscle cell viability under hyperglycemia; however, the molecular mechanism is still poorly understood. Here we revealed that salidroside could suppress hyperglycemia-induced ferroptosis in skeletal muscle cells by promoting GPX4 expression, thereby restoring their viability and paracrine functions. These in turn promoted the proliferation and migration potentials of blood vessel-forming cells. Furthermore, we showed that salidroside/GPX4-mediated ferroptosis inhibition is crucial for promoting angiogenesis and blood perfusion recovery in diabetic HLI mice. Together, we reveal a novel molecular mechanism of salidroside in enhancing skeletal muscle cells-mediated revascularization and blood perfusion recovery in diabetic HLI mice, further highlighting it as a potential compound for treating diabetic HLI.

Sarcopenia-a geriatric pandemic : A narrative review

With growing life expectancy, the prevalence of frailty and sarcopenia will continuously increase during the next decades. Geographical differences have been described, and depending on the population studied, sarcopenia is evident in 10% of community-dwelling people, increasing up to 40 to 50% among those living in nursing homes. Sarcopenia is a complex age-related process of multifactorial pathogenesis, influenced by lifestyle, nutrition, biological processes during aging, and also immunological and endocrine mechanisms. For diagnostic criteria, physical parameters (muscle mass measurement) and functional aspects (muscle strength, gait speed, physical performance) are required. In routine clinical care, screening patients using the SARC‑F questionnaire is recommended by recent guidelines of the European Workgroup for Sarcopenia.

Effects of Probiotics Supplementation on the Intestinal Metabolites, Muscle Fiber Properties, and Meat Quality of Sunit Lamb

The development of animal husbandry is closely related to the meat quality of small ruminants. Intestinal metabolites and the muscle fiber types of lambs are important factors that affect their meat quality, but few studies have examined the regulation of the "intestinal muscle axis" by probiotics. In this study, 12 Sunit lambs were divided into a control group (C) and a probiotics group (P). The gene expressions of the myosin heavy chain, metabolic enzyme activity, and short-chain fatty acids in the intestines were analyzed using gas chromatography-mass spectrometry (GC-MS) and quantitative real-time PCR. The results showed that levels of propionic acid and butyric acid in the intestines of group P were significantly higher than in group C (p < 0.05). In addition, probiotics increased the number and area ratio of type I muscle fibers. They also increased the mRNA expression of MyHC IIA and the activity of malate dehydrogenase (MDH) and succinate dehydrogenase (SDH). Propionic acid was negatively correlated with the number ratio of type IIB muscle fibers. Butyric acid was found to be significantly positively correlated with the number ratio of type IIA muscle fibers. Cooking loss, pH_24h, and shear force decreased significantly in group P. In conclusion, intestinal metabolites (SCFAs) altered the activity of oxidative-myofibril-metabolizing enzymes and the expression of myosin heavy-chain type IIA, reduced the meat shear values, and improved meat tenderness. This study provides a new basis for improving the production and meat quality of small ruminants.

Porcine IGF-1R synonymous mutations in the extracellular domain affect proliferation and differentiation of skeletal muscle cells

OBJECTIVE

Miniature pigs are considered ideal organ donors for xenotransplantation in humans, but the mechanism underlying their dwarfism remains to be elucidated. IGF-1R is a crucial factor in body size formation in mammals, including skeletal muscle formation and development. The extracellular domain (ECD) binds to the ligand, a phenomenon that results in the activation of downstream pathways.

METHODS

In this study, the coding sequences of two IGF-1R ECD haplotypes of the large Landrace (LP) pig and the small Bama Xiang (BM) pig were cloned into pcDNA3.1 vectors to generate pcDNA3.1-LP and pcDNA3.1-BM. The two recombinant vectors were then transfected into skeletal muscle cells.

RESULTS

IGF-1R transcript was found to be expressed at higher levels in the pcDNA3.1-LP group than in the pcDNA3.1-BM group. The IGF-1R ECD from LP promoted cell proliferation and CyclinD1 expression, and promoted the phosphorylation of protein kinase B (to yield p-AKT). Moreover, the IGF-1R ECD from LP increased cell differentiation and the expression of myogenic determination factor (MyoD).

CONCLUSION

Our data indicated that the IGF-1R ECD haplotypes between pig breeds with different body sizes affect IGF-1R expression, in turn affecting the proliferation and differentiation of skeletal muscle cells by activating downstream signalling pathways.

The prognostic value of sarcopenia in oesophageal cancer: A systematic review and meta-analysis

The loss of skeletal muscle mass and function is defined as sarcopenia, which might develop in elderly patients with cancers. It has been indicated as a potential negative factor in the survival of patients with malignant tumours. The aim of this systematic review and meta-analysis was to evaluate the associations between sarcopenia and survival outcomes or postoperative complications in patients with oesophageal cancer (EC). Web of Science, Embase, Medline, and Cochrane Library databases were searched until 10 May 2022, using keywords: sarcopenia, oesophageal cancer, and prognosis. Studies investigating the prognostic value of sarcopenia on EC survival were included. Forest plots and summary effect models were used to show the result of this meta-analysis. The quality of included studies was evaluated with the Newcastle-Ottawa Scale (NOS). A total of 1436 studies were identified from the initial search of four databases, and 41 studies were included for the final quantitative analysis. This meta-analysis revealed a significant association between sarcopenia and overall survival (OS) [hazard ratios (HR):1.68, 95% confidence interval (CI):1.54-1.83, P = 0.004, I²  = 41.7%] or disease-free survival (DFS) 1.97 (HR: 1.97, 95% CI: 1.44-2.69, P = 0.007, I²  = 61.9%) of EC patients. Subgroup analysis showed that sarcopenia remained a consistent negative predictor of survival when stratified by different treatment methods, populations, or sarcopenia measurements. Sarcopenia was also a risk factor for postoperative complications with a pooled odds ratio of 1.47 (95% CI: 1.21-1.77, P = 0.094, I²  = 32.7%). The NOS scores of all included studies were ≥6, and the quality of the evidence was relatively high. The results from the study suggested that sarcopenia was significantly associated with both survival outcomes and postoperative complications in EC patients. Sarcopenia should be appropriately diagnosed and treated for improving short-term and long-term outcomes of patients with EC.

Sarcopenia and COVID-19 Outcomes

Coronavirus disease 2019 (COVID-19) spread rapidly and became a severe global public health threat. Older adults have a high risk of COVID-19 and its associated mortality. Sarcopenia has emerged as a predictor of poor outcomes in COVID-19 patients, including lengthy hospital stays, mortality, intensive care unit admission, need for invasive mechanical ventilation, and poor rehabilitation outcomes. Chronic inflammation, immune dysfunction, respiratory muscle dysfunction, and swallowing dysfunction may underlie the association between sarcopenia and the poor outcomes of COVID-19 patients. Interleukin 6 receptor blockers (tocilizumab or sarilumab) are recommended for treating patients with severe COVID-19, and their therapeutic effects on sarcopenia are of great interest. This review aimed to analyze the current reports on the association between sarcopenia and COVID-19 and provide an update on the contribution of sarcopenia to the severity and adverse outcomes of COVID-19 and its underlying mechanisms. We also aimed to explore the different screening tools for sarcopenia concurrent with COVID-19, and advocate for early diagnosis and treatment of sarcopenia. Given that the fight against the COVID-19 pandemic may be long-term, further research into understanding the effects of sarcopenia in patients infected with the Omicron variant is necessary.