Standing-Long-Jump Test Application in Identifying Female Adolescents at Risk of Sarcopenic Obesity / Aplicación de la Prueba de Salto de Longitud de Pie para Identificar a Adolescentes con Riesgo de Obesidad Sarcopénica

SUMMARY: The identification of children and adolescents who are at risk of sarcopenic obesity development often requires specialized equipment and expensive test procedures. Therefore, the establishment of cheaper and faster methods would be greatly useful, especially if they could be applied in the field. The study's objective was to establish if identification of female adolescents who suffer the risk of developing sarcopenic obesity can be obtained through the standing-long-jump test application. To achieve the research objectives, various anthropometric and body composition measurements were performed and lower limb explosive strength was assessed using the standing long jump fitness test. The research was conducted on a sample of 535 female respondents randomly selected from 9 elementary schools in the Skopje region of the Republic of North Macedonia. The respondents were divided into quintiles according to BMI z-scores, and the arithmetic means and SD about muscle-to-fat ratio were calculated for each quintile. The cutoff was determined based on the mean and standard deviation of the muscle-to-fat ratio for the 3rd quintile of BMI and the percentage of respondents with sarcopenic obesity was examined. The optimal cut-off value of the long jump fitness test results for predicting sarcopenic obesity in an adolescent girl showed that the area under the ROC curve was 0.781 (95 % CI 0.743-0.815). The standing-long-jump test values, on grounds of odds ratio (OR 95 % CI) about the girls at risk of sarcopenic obesity development, which was identified on muscle-to-fat ratio base, were 8.76 (4.39 - 17.54, p 0.001). It can be used to predict sarcopenic obesity presence in female adolescents, which can be vital in case of health intervention.

La identificación de niños y adolescentes que corren riesgo de desarrollar obesidad sarcopénica a menudo requiere equipos especializados y procedimientos de pruebas costosos. Por lo tanto, el establecimiento de métodos más baratos y rápidos sería de gran utilidad, especialmente si pudieran aplicarse en el campo. El objetivo del estudio fue establecer si la identificación de mujeres adolescentes que sufren riesgo de desarrollar obesidad sarcopénica se puede obtener mediante la aplicación de la prueba de salto de longitud de pie. Para lograr los objetivos de la investigación, se realizaron diversas mediciones antropométricas y de composición corporal y se evaluó la fuerza explosiva de los miembros inferiores mediante la prueba de aptitud de salto de longitud de pie. La investigación se realizó con una muestra de 535 mujeres encuestadas seleccionadas al azar de 9 escuelas primarias de la región de Skopje, en la República de Macedonia del Norte. Los encuestados se dividieron en quintiles según las puntuaciones z del IMC, y se calcularon las medias aritméticas y la DE sobre la relación músculo-grasa para cada quintil. El límite se determinó en función de la media y la desviación estándar de la relación músculo-grasa para el tercer quintil del IMC y se examinó el porcentaje de encuestados con obesidad sarcopénica. El valor de corte óptimo de los resultados de la prueba de condición física de salto de longitud para predecir la obesidad sarcopénica en una adolescente mostró que el área bajo la curva ROC fue 0,781 (IC del 95 %: 0,743-0,815). Los valores de la prueba de salto de longitud de pie, sobre la base del odds ratio (OR IC del 95 %) sobre las niñas en riesgo de desarrollar obesidad sarcopénica, que se identificó sobre la base del ratio músculo-grasa, fueron 8,76 (4,39 - 17,54, p. 0,001). Puede utilizarse para predecir la presencia de obesidad sarcopénica en adolescentes, lo que puede ser vital en caso de intervención sanitaria.

Physical activity, protein consumption, and loss of muscle mass in older adult participants of the ELSA-Brazil study / Atividade física, consumo de proteínas e perda de massa muscular em idosos do ELSA-Brasil

Objetivo: Objetiva-se avaliar a relação entre consumo de proteínas (CP), atividade física (AF) e massa muscular (MM) em indivíduos com 60 anos ou mais de idade. Metodologia: Trata-se de um estudo prospectivo a partir da linha de base e segunda onda do estudo ELSA-Brasil. O CP foi avaliado por meio de um questionário de frequência alimentar semiquantitativo (QFA). A AF foi mensurada pelo International Physical Activity Questionnaire (IPAQ). A MM foi estimada por meio de equação de predição, e calculada a diferença de MM entre a 2a e a 1a onda. Análises bivariadas foram realizadas adotando o valor de p < 0,05. Para as análises multivariadas, utilizou-se a regressão de Poisson, com quatro modelos distintos, que incluíram as covariáveis com valor de p < 0,20. Utilizou-se o pacote estatístico SPSS versão 21. Resultados: A amostra foi constituída de 2216 idosos, sendo 55,10% de mulheres, com média de idade de 65,20 ± 4,15. Indivíduos com redução de MM entre as duas ondas estão situados no primeiro quartil de consumo de proteína. Além disso, a média de AF mostrou diferença significativa entre os grupos e a AF no lazer apenas para as mulheres (p < 0,05). Após ajuste por variáveis sociodemográficas, de saúde e hábitos de vida, indivíduos com menor consumo de proteínas apresentaram risco de 1,45 (1,29 ­ 1,63) de apresentar MM diminuída. Conclusões: O menor CP e AF forte estão associados à MM diminuída, e aqueles com menor CP no primeiro e segundo quartis apresentam maior risco de possuir MM diminuída. (AU)

Objective: The objective was to evaluate the relationship between protein consumption, physical activity, and muscle mass in individuals aged ≥ 60 years. Methods: This prospective study was based on the baseline and second wave of the ELSA Brazil study. Protein consumption was assessed using a semiquantitative food frequency questionnaire. Physical activity was measured using the International Physical Activity Questionnaire. Muscle mass was estimated using a prediction equation, and the difference in MM between the first and second waves was calculated. Bivariate analyses were performed, with p < 0.05 considered significant. Multivariate analysis consisted of 4 Poisson regression models including covariates with p < 0.20. The statistical analysis was performed in IBM SPSS Statistics 21. Results: The sample included 2216 older adults, 55.10% of whom were women, with a mean age of 65.20 (SD, 4.15). Participants whose muscle mass decreased between the waves were in the first quartile of protein consumption. Mean physical activity significantly differed between the groups, while leisure-time physical activity differed only for women (p < 0.05). After adjusting for sociodemographic, health, and lifestyle variables, participants with lower protein intake had a 1.45 (1.29­1.63) relative risk of muscle mass loss. Conclusions: Lower protein consumption and higher physical activity were associated with decreased muscle mass, and those with protein consumption in the first and second quartiles are at higher risk of muscle mass loss. (AU)

Effects of PM2.5 and heat/cold exposure on AKT/GLUT4 pathway in mouse skeletal muscle and white adipose tissue / 环境与职业医学

Background It is unclear if there is any combined effect of air pollutants and non-optimal temperature on metabolic syndrome, or any molecular mechanisms of related signaling pathways in the process, which requires urgent systematic research. Objective To observe the effects of combined exposure to PM2.5 and non-optimal temperature on metabolic damage at gene and protein levels in mice, and elucidate the role of related signaling pathway in crucial organs. Methods A total of 60 six-week-old male C57BL/6J mice were randomly divided into six groups: a normal temperature-filter air group (TN-FA), a normal temperature-concentrated PM2.5 group (TN-PM), a heat-filter air group (TH-FA), a heat-concentrated PM2.5 group (TH-PM), a cold-filter air group (TC-FA), and a cold-concentrated PM2.5 group (TC-PM). The Shanghai Meteorological and Environmental Animal Exposure System (Shanghai-METAS) was used to provide combined exposure settings of air types [concentrated PM2.5 and filter air (FA)] and temperatures [normal (22°C), cold (4°C), and heat (30°C)] for 4 weeks. Skeletal muscle and white adipose tissue (WAT) of the mice were sampled at the end of exposure, and transcriptomics and Western blot (WB) assay were adopted to observe selected gene and protein expression levels in the samples respectively. Results The transcriptomics results indicated that the PM2.5 exposure enhanced the number of differentially expressed genes. Specifically, 4820 genes were differentially expressed in the TN-PM mice compared to the TN-FA mice at normal temperature, and 1143 genes were differentially expressed in the Tc-PM mice compared to the Tc-FA mice in the cold environment. The phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway and the endoplasmic reticulum protein processing pathway were identified as the most significant pathways in metabolic injury resulting from combined exposure to PM2.5 and non-optimal temperature exposure. The WB results showed that exposure to PM2.5 in the normal temperature and the cold environments led to a significant increase in the expression of p-AKT in WAT (P<0.01, P<0.05) and a significant decrease in the expression of GLUT4 (P<0.05, P<0.01). In skeletal muscle, exposure to PM2.5 led to a significant decrease in GLUT4 (P<0.05) in all environments, with a consistent trend of change as observed in WAT. Conclusion Cold/heat exposure might promote PM2.5-induced metabolic disorder through suppression of the AKT/GLUT4 pathway, aggravating metabolic damage.

Treatment of Exercise-induced Fatigue with Buzhong Yiqitang Through Adipor1/AMPK/PGC-1α to Regualte Lipid Metabolism / 中国实验方剂学杂志

ObjectiveTo discuss the impact of Buzhong Yiqitang on lipid metabolism in skeletal muscle of exercise-induced fatigue （EIF） mice through adiponectin receptor 1 （Adipor1）/adenosine 5'-monophosphate（AMP）-activated protein kinase （AMPK）/peroxisome proliferator-activated receptor gamma coactivator-1α （PGC-1α）. MethodC57BL6J mice were randomly divided into the control group， model group， low， middle， and high dose groups of Buzhong Yiqitang， and vitamin C group. No intervention was given to the control group， while the other groups were subjected to exhaustive swimming training to establish the EIF model. One hour before exhaustion， 0.2 mL distilled water was given to the control group and the model group， while the mice in the low， middle， and high dose groups of Buzhong Yiqitang were given intragastrically Buzhong Yiqitang of 4.1， 8.2， and 16.4 g·kg-1， respectively， and the vitamin C group was given vitamin C of 0.04 g·kg-1 via gavage for a duration of six weeks. After six weeks of the experiment， the growth rate of body weight， organ index， and exhaustive swimming time were calculated. Enzyme colorimetry was utilized to detect the levels of blood urea nitrogen （BUN）， creatine kinase acid （CK）， lactate dehydrogenase acid （LDH）， and lactic acid （LD）. The pathological changes of skeletal muscle were observed using hematoxylin -eosin （HE） staining， while the ultrastructure of skeletal muscle was observed with transmission electron microscope （TEM）. The contents of free fatty acids （NEFA） and triglyceride acid （TG） in serum were also examined by microplate method. The protein expressions of Adipor1， p-AMPK/AMPK， PGC-1α， and HK2 in the skeletal muscle were measured by Western blot. ResultCompared with those of the control group， the growth rate of body weight and thymus index of the model group were decreased， and the serum levels of BUN， CK， LD， and LDH were increased （P<0.01）. The contents of NEFA and TG were decreased （P<0.01）， and the protein expression of Adipor1， p-AMPK/AMPK， PGC-1 α， and HK2 in the skeletal muscle decreased （P<0.05， P<0.01）. Compared with those in the model group， the growth rate of body weight， thymus index， and exhaustive swimming time were significantly increased （P<0.01）， and the levels of BUN， CK， LD， and LDH dropped in the high dose group of Buzhong Yiqitang （P<0.01）. The levels of NEFA and TG were greatly improved （P<0.01）. The protein expressions of Adipor1， p-AMPK/AMPK， PGC-1α， and HK2 in the skeletal muscle were significantly increased （P<0.05， P<0.01）. Compared with those in the model group， the thymus index and exhaustive swimming time were significantly increased in the vitamin C group， and the levels of BUN， CK， and LD dropped （P<0.05， P<0.01）. The levels of NEFA and TG were improved significantly （P<0.01）， and the protein expression of Adipor1 in skeletal muscle was increased greatly （P<0.01）. ConclusionBuzhong Yiqitang can delay the development of EIF， which may be connected with the regulation of the Adipor1/AMPK/PGC-1α signaling pathway and the improvement of the utilization rate of skeletal muscle to fat.

Accuracy evaluation of bioelectrical impedance analysis in assessment of appendicular skeletal muscle mass in adults aged 18-42 years / 实用医学杂志

Objective To evaluate the accuracy of bioelectrical impedance analysis(BIA)in measurement of appendicular skeletal muscle mass(ASM)of adults.Methods A total of 836 adults aged 18-42 years were recruited in Guangzhou using a convenient sampling method from April 2021 to September 2022.ASM was measured using BIA and Dual-energy X-ray absorptiometry(DXA).Using DXA as the standard method,the consistency between the BIA and DXA measurements was evaluated by intra-class correlation coefficients(ICCs)and Bland-Altman analysis in logarithmically transformed data,in order to evaluate the accuracy of BIA in ASM measurement.Receiver operating characteristic curve was plotted to evaluate the diagnostic value of BIA for screening low muscle mass.Results A total of 774 individuals were included for analysis finally.ICCs for ASM measured by BIA and DXA were 0.774 and 0.667 in males and females,respectively.Mean ratios(limits of Agreement)of ASM were 0.94(0.80-1.10)and 0.91(0.78-1.05)in males and females,respectively.Area under curve of BIA for screening low muscle mass were 0.91 and 0.94 in males and females,respectively.The optimal cut-off values of Z-score by BIA for males and females were-0.57 and-0.66,respectively.Sensitivity and specificity for males were 82.5%and 86.0%,while being 86.8%and 93.8%,for females.Conclusion BIA shows a moderate consistency with DXA for measuring ASM in adults.Furthermore,BIA yields a good diagnostic value in identifying low muscle mass in adults aged 18-42 years.

TGF-β's role in skeletal muscle injury repair:Mechanism and research advances / 实用医学杂志

Skeletal muscle injury is a common disease in clinical practice,and an in-depth understanding of its repair mechanisms is crucial for the development of effective therapeutic strategies.This paper focuses on the key role of TGF-β in skeletal muscle injury repair,introduces the diversity of its family members and signaling pathways,explores the expression and regulation part of TGF-β after skeletal muscle injury,analyzes its early expression dynamics and regulatory factors,and thoroughly investigates the effects of TGF-β on skeletal muscle repair,revealing its inflammatory regulation,cellular activation and proliferation as well as fibrosis.Key role.Special attention was paid to its mechanism of action in muscle regeneration and its regulatory mechanism at the cellular level.In addition,the potential clinical applications of TGF-β in the repair of skeletal muscle injury were discussed,and the development and application of it as a therapeutic target and modulator were explored.However,controversies and shortcomings still exist in the current study,such as the dual roles of TGF-β and the impact of individual differences on treatment.Future research directions should include digging deeper into the details of signaling pathways and biomarker discovery.By overcoming these challenges,the potential clinical application of TGF-β in skeletal muscle injury repair is expected to usher in new breakthroughs and provide patients with more individualized and effective treatment strategies.

A systematic review of mouse model construction for sarcopenia / 中国组织工程研究

BACKGROUND:Sarcopenia is a progressive,generalized skeletal muscle disease that is closely related to the occurrence of osteoarthritis,fractures,limb disability and death in the elderly.Establishing animal models of sarcopenia is essential to understand the pathophysiology of sarcopenia and to identify effective treatment strategies. OBJECTIVE:To review the evaluation criteria of mouse models of sarcopenia and the modeling methods of mouse models of sarcopenia,and to analyze and compare the advantages and disadvantages of various modeling methods,in order to provide reference for the research and diagnosis and treatment of sarcopenia. METHODS:"Sarcopenia,skeletal muscle aging,mouse model,animal model"in Chinese and English were used as Chinese and English search terms,respectively.The search formula was"(sarcopenia OR skeletal muscle aging)AND(mouse model OR animal model)."CNKI,WanFang and PubMed were searched for related articles published from January 2010 and October 2022.A total of 59 articles were finally included for analysis. RESULTS AND CONCLUSION:There is a faster modeling time in SAMP8 mice and the type of muscle atrophy is consistent with that of patients with sarcopenia.Therefore,it is an ideal model.Although the surgical method can successfully induce muscle atrophy,it requires precise surgical operation,which is difficult and time-consuming.Hindlimb suspension modeling in mice is similar to that of the elderly and can be regarded as an effective model of senile sarcopenia.Although reagent injection molding is simple to perform,both the dose and number of days of administration of reagents are not clear and need to be further investigated.Transgenic mouse models are less commonly used and their model stability needs further study.The search for a mouse model with low cost,short time consumption and high simulation of human sarcopenia is still a future research direction.

Atg-mediated autophagy,exercise and skeletal muscle aging / 中国组织工程研究

BACKGROUND:Exercise as a viable non-pharmacological treatment has the potential to reverse skeletal muscle aging that deteriorates with age.The role of autophagy in the skeletal muscle aging process is indispensable.During skeletal muscle aging,Atg genes involved in regulating autophagy regulate the autophagic process in either a facilitative or inhibitory manner to improve the physiological morphology of skeletal muscle.However the specific molecular mechanisms of autophagy in the exercise regulation of skeletal muscle aging remain puzzling. OBJECTIVE:To search for general patterns of the effects of autophagic mechanisms on skeletal muscle aging during exercise through a review of articles in this field. METHODS:(1)CNKI and Web of Science were searched,reviewed,and screened for relevant literature using the keywords of"Atg genes(proteins),autophagy,exercise,and skeletal muscle aging"to lay the theoretical foundation for the full-text analysis.(2)The comparative analysis method was used to compare the similarities and differences among the included documents to provide reasonable theoretical support for the arguments.By the further comparative analysis of the literature,the relationship between relevant indicators was clarified,to provide the ideas for the full-text analysis. RESULTS AND CONCLUSION:Atg family-mediated autophagy is indispensable for delaying skeletal muscle aging.Atg genes involved in regulating autophagy regulate the autophagic process in either a facilitative or inhibitory manner to improve the physiological morphology and function of skeletal muscle.Different exercise patterns,such as age,time,or intensity at initiation,may have heterogeneous effects on the expression of autophagy-related proteins,but long-term aerobic exercise regulates Atg-related proteins,induces skeletal muscle autophagy,and delays the loss of muscle mass.

Extracellular vesicles in sarcopenic obesity:roles and mechanisms / 中国组织工程研究

BACKGROUND:Extracellular vesicles can regulate insulin resistance and control inflammatory response by participating in intercellular communication,while repairing skeletal muscles and promoting skeletal muscle regeneration,which is expected to be a novel treatment modality for sarcopenic obesity. OBJECTIVE:To review the biogenesis of extracellular vesicles,their biological functions,their relationship with sarcopenic obesity,and recent advances in the pathogenesis,diagnosis,and treatment of sarcopenic obesity. METHODS:The first author performed a computer search of PubMed,Embase,CNKI and other databases for relevant studies involving extracellular vesicle in sarcopenic obesity.The search keywords were"extracellular vesicle,exosome,sarcopenic obesity,obese sarcopenia,skeletal muscle regeneration,skeletal muscle mass regulation"in English and Chinese,respectively.The search period was from June 2022 to November 2022.After screening,87 articles were included for further review. RESULTS AND CONCLUSION:Extracellular vesicles are important vectors of bidirectional cell communication and participate in the regulation of normal physiological and pathological processes through autocrine,paracrine and endocrine ways.Sarcopenic obesity is a complex multi-factor disease.Extracellular vesicles are involved in the occurrence and development of sarcopenic obesity mainly by regulating the inflammatory response of skeletal muscle and the homeostasis of muscle cells.Cytokines secreted by adipose tissue and skeletal muscle are released into the extracellular circulation through extracellular vesicle encapsulation and interact with each other to promote skeletal muscle insulin resistance and lipogenesis,which is the main pathophysiology of skeletal muscle atrophy in sarcopenic obesity.Extracellular vesicles not only promote the development of sarcopenic obesity by providing specific pathogenic markers,but also are a valuable diagnostic indicator of sarcopenic obesity.Release of extracellular vesicles from skeletal muscle during exercise enhances metabolic response and promotes skeletal muscle regeneration.Extracellular vesicles can not only be used as therapeutic targets for sarcopenic obesity but also be used to treat sarcopenic obesity by loading drugs to effectively improve drug bioavailability.

The role of BMAL1 and MyoD in exercise-induced skeletal muscle damage / 中国组织工程研究

BACKGROUND:A high-load exercise can trigger the degradation of titin,leading to skeletal muscle damage.MyoD participates in skeletal muscle generation and plays an important role in the repair of skeletal muscle damage. OBJECTIVE:To observe the expression changes of MyoD,BMAL1 and titin in skeletal muscles at different times during a high-load exercise,as to clarify the role of MyoD and BMAL1 in exercise-induced skeletal muscle damage. METHODS:Twenty-four 8-week-old Sprague-Dawley rats were randomly divided into a control group(n=4)and an exercise group(n=20).Rats in the exercise group were subjected to downhill running(90 minutes).Soleus muscle samples were collected at 0,12,24,48,and 72 hours after exercise.The mRNA expressions of BMAL1 and MyoD were measured by real-time fluorescence quantitative PCR.The ultrastructure of skeletal muscle fibers was observed by transmission electron microscope.Immunofluorescence was used to observe the co-localization of MyoD and BMAL1 as well as BMAL1 and titin. RESULTS AND CONCLUSION:After the single high-load centrifugal exercise,the sarcomere of the soleus muscle was widened and the Z-line was blurred and water wave-like,both of which were most serious at 12 hours after exercise and basically recovered at 72 hours.The results of real-time fluorescent quantitative PCR showed that BMAL1 mRNA expression in the exercise group increased first and then tended to normal,while the mRNA expression of MyoD decreased first and then increased.Immunofluorescence co-localization observation indicated that the co-localization of BMAL1 and MyoD was obviously observed at 12 and 24 hours after exercise,and the co-localization of BMAL1 and titin was observed at 0,12,and 24 hours.All the findings indicate that MyoD and BMAL1 are jointly involved in the repair of exercise-induced skeletal muscle damage probably via titin.

Ischemia-reperfusion injury in total knee arthroplasty / 中国组织工程研究

BACKGROUND:The mechanism,manifestation,prevention and treatment of ischemia-reperfusion injury have been reported in the past.However,there are few studies on the ischemia-reperfusion injury of lower limb skeletal muscle caused by total knee arthroplasty.This article focuses on the pathogenesis,clinical impact,prevention and treatment of the ischemia-reperfusion injury of lower limb caused by total knee arthroplasty. OBJECTIVE:To summarize the related literature of lower limb ischemia-reperfusion injury caused by total knee arthroplasty,analyze the mechanism and significance,and give hints for further research on skeletal muscle ischemia-reperfusion injury. METHODS:The relevant articles on PubMed,CNKI,WanFang and VIP databases published from January 1,2000 to April 30,2022 were searched by computer with the Chinese and English search terms of"ischemia-reperfusion injury,total knee arthroplasty,tourniquet,mechanism,pathophysiology,skeletal muscle,treatment".After excluding repetitive research and some basic articles with low correlation,68 articles were finally selected for review. RESULTS AND CONCLUSION:(1)The pathogenesis of ischemia-reperfusion injury is related to oxygen free radicals,intracellular calcium overload,neutrophil activation,as well as high concentration of nitric oxide,no reflow phenomenon,apoptosis and other mechanisms.More detailed mechanism research can provide basis for future prevention and treatment.(2)Ischemia-reperfusion injury of lower limbs will cause local skeletal muscle injury,which may be caused by the trauma of the operation itself or the role of ischemia-reperfusion injury.More targeted research is needed to distinguish the relationship between the two.(3)Ischemia-reperfusion injury of lower limbs may even affect the distal organs,causing kidney and lung damage.It also affects local and systemic circulation.(4)To clarify the effect of ischemia-reperfusion injury can point out the direction for future prevention and treatment.The current prevention and treatment measures mainly include ischemic preconditioning,anesthetic,antioxidant and other drug prevention.(5)The detailed review of ischemia-reperfusion injury of lower limb skeletal muscle caused by total knee arthroplasty can provide basis for future diagnosis and treatment decisions.

Mechanism of satellite cell regulation and its role in ecological niche signaling during skeletal muscle regeneration / 中国组织工程研究

BACKGROUND:Satellite cells are a specific population of adult stem cells contained in skeletal muscle that promote the regenerative reconstruction of injured skeletal muscle,but their specific mechanisms are not well established. OBJECTIVE:To review the regulatory role of satellite cells during skeletal muscle regeneration and the mechanism of interaction between satellite cells and their ecological niche signals,aiming to provide new research ideas and perspectives based on the summary of existing knowledge. METHODS:Web of Science,PubMed,CNKI,WanFang,and VIP databases were searched for literature published between January 2002 and June 2022.English search terms were"muscle,skeletal muscle,muscle injury,stem cells,satellite cells,muscle repair".Chinese search terms were"skeletal muscle,skeletal muscle regeneration,skeletal muscle reconstruction,satellite cells,ecological niche".The 66 included papers were organized and analyzed. RESULTS AND CONCLUSION:(1)Satellite cells exist in skeletal muscle and contribute to both the formation of new muscle fibers after injury and the effective growth of existing adult muscle fibers.(2)After the activation of quiescent satellite cells in satellite cells,the steps of satellite cell proliferation,differentiation and fusion to form muscle fibers during skeletal muscle regeneration are influenced by their intrinsic regulatory effects of different mechanisms.(3)Satellite cells can interact with myofibers,extracellular matrix,skeletal muscle junctions,fibroblast progenitor cells,immune cells and endothelial cells in the ecological niche signal to promote satellite cell activation,proliferation and differentiation to achieve effective skeletal muscle regeneration.(4)Possible breakthroughs in future research include:the division pattern of satellite cells in the body;the mechanisms regulating satellite cell transfer;the specific timing of satellite cell differentiation or self-renewal in vivo;and the interaction mechanisms between satellite cells and skeletal muscle junctions.(5)This review may provide some theoretical reference values for the field of injury reconstruction of skeletal muscle and its innovation.

Effect of aerobic exercise on glycolipid metabolism,skeletal muscle inflammation and autophagy in type 2 diabetic rats / 中国组织工程研究

BACKGROUND:Obesity and its relevant chronic inflammation are important risk factors for inducing type 2 diabetes.This inflammatory response will further involve skeletal muscle,leading to an increase in catabolic and autophagic fluxes in skeletal muscle.Aerobic exercise is the mainstream mode of exercise in the prevention and treatment of type 2 diabetes,and may also has a certain protective effect on skeletal muscle. OBJECTIVE:To explore the effects and regulatory mechanisms of aerobic exercise on glucolipid metabolism,skeletal muscle inflammation and autophagy in type 2 diabetic rats. METHODS:Animal models of type 2 diabetes were established in rats by 8-week high-fat feeding combined with streptozotocin injection,and the experimental rats were then divided into normal control group,normal exercise group,diabetic control group and diabetic exercise group.The exercise group performed 4 weeks of aerobic exercise(16 m/min,60 min/d,5 d/wk).The levels of blood glucose,high-density lipoprotein,low-density lipoprotein and triglyceride in serum were measured by an automated biochemical analyzer.Serum insulin level was determined using enzyme-linked immunosorbent assay and the insulin resistance index and area under the glucose metabolism curve were calculated.The levels of interleukin 6 and tumor necrosis factor α in skeletal muscle were measured by enzyme-linked immunosorbent assay after 4 weeks of aerobic exercise,and the expression levels of forkhead box protein O3(FoxO3),LC3 and p62 in skeletal muscle were measured by western blot assay. RESULTS AND CONCLUSION:The area under the glucose tolerance curve and insulin resistance index both increased significantly in type 2 diabetic rats(P<0.001,P=0.025),and aerobic exercise significantly reduced the area under the glucose tolerance curve and insulin resistance index in the normal exercise group(P<0.001,P=0.038)and diabetic exercise group(P<0.001,P=0.004).Serum high-density lipoprotein significantly decreased(P=0.030),and low-density lipoprotein and triglyceride(P=0.027,P=0.014)levels significantly increased in the diabetic control group compared with the normal control group.Aerobic exercise significantly reduced triglyceride and low-density lipoprotein levels in the normal exercise group(P=0.019,P=0.008)as well as triglyceride levels in the diabetic exercise group(P=0.022).Both interleukin-6 and tumor necrosis factor α levels were significantly increased in the skeletal muscle of type 2 diabetic rats compared with the normal control group(P<0.001,P=0.007),and aerobic exercise significantly reduced tumor necrosis factor α levels in the diabetic exercise group(P=0.017).The LC3-Ⅱ/LC3-I was significantly increased in the skeletal muscle of type 2 diabetic rats compared with the normal control group.Aerobic exercise significantly increased the LC3-Ⅱ/LC3-I in the normal exercise group(P<0.001)and decreased the LC3-Ⅱ/LC3-I,FoxO3 and p62 protein expression levels in the diabetic exercise group(P=0.026,P=0.050,P=0.048).To conclusion,type 2 diabetes model established by high-fat feeding combined with streptozotocin injection has obvious glycolipid metabolism disorder,and leads to inflammatory response and excessive activation of autophagy in skeletal muscle.Aerobic exercise can improve glycolipid metabolism,reduce local inflammation in skeletal muscle and inhibit autophagy,and finally play a protective role in skeletal muscle.

Mechanism by which static exercise improves insulin resistance in skeletal muscle of type 2 diabetes / 中国组织工程研究

BACKGROUND:Skeletal muscle insulin resistance is the key pathological link of type 2 diabetes.Static exercise can effectively improve skeletal muscle insulin resistance,but the mechanism remains unclear. OBJECTIVE:To explore the mechanism of static exercise on insulin resistance in the skeletal muscle of type 2 diabetic mice based on the phosphatidyl inositol 3-kinase(PI3K)/protein kinase B(AKT)/glucose transporter(GLUT4)signaling pathway. METHODS:After 1 week of adaptive feeding,7 out of 40 C57BL/6 mice were randomly selected as blank group and fed common diet,while the other mice were fed high-fat diet and taken to prepare type 2 diabetes models through the low-dose streptozotocin intraperitoneal injection.Twenty-four mice were successfully modeled and they were randomly divided into model group(n=8),metformin group(n=8)and static exercise group(n=8),which continued to be fed high-fat diet.The metformin group was given 200 mg/kg metformin dissolved in normal saline(2 ml/kg)by gavage,once a day,for 6 weeks.The static exercise group was given normal saline daily by gavage and carried out static exercise,30 minutes a day,6 days per week.The model group was given the same dose of normal saline daily by gavage without exercise intervention.After the intervention,the fasting blood glucose of each group was detected,the intraperitoneal glucose tolerance test was performed,and the area under the glycemic curve was calculated.Glycosylated hemoglobin,serum insulin,insulin resistance index were detected by ELISA.Total cholesterol,triglyceride,high-density lipoprotein,low-density lipoprotein were detected using biochemical methods.The mRNA expression levels of PI3K,AKT and GLUT4 in the gastrocnemius of mice were detected by real-time quantitative PCR.Morphological changes of the gastrocnemius were observed by hematoxylin-eosin staining,and the cross-sectional area of muscle fibers was calculated. RESULTS AND CONCLUSION:Compared with the blank group,fasting blood glucose,glycosylated hemoglobin,area under the glycemic curve,insulin resistance index,total cholesterol,triglyceride and low-density lipoprotein levels were significantly increased in the model group(P<0.01,P<0.05).Whereas,these indicators were significantly lower in the static exercise and metformin group than the model group(P<0.01,P<0.05).Compared with the blank group,serum insulin and high-density lipoprotein levels were significantly declined in the model group(P<0.01)and the mRNA expression of PI3K,AKT and GLUT4 in the gastrocnemius of mice were also significantly reduced(P<0.01).These indicators were significantly elevated in the metformin group and static exercise group compared with the blank group(P<0.01).Compared with the blank group,the muscle fibers in the model group were disordered,and the muscle cells atrophied and the muscle fiber gap widened.The cross-sectional area of muscle fibers was significantly decreased in the model group compared with the blank group(P<0.01).Compared with the model group,atrophy of the gastrocnemius fibers and muscle fiber space were improved in the static exercise group and the metformin group,and the cross-sectional area of muscle fiber was significantly increased in both groups(P<0.01).These findings indicate that static resistance training may promote glucose uptake and utilization by up-regulating the expression of PI3K,AKT and GLUT4 mRNA in skeletal muscle tissue,thereby improving the morphology and function of skeletal muscle tissue,alleviating insulin resistance and regulating glucose homeostasis.

Delayed onset muscle soreness and exercise-induced skeletal muscle memory / 中国组织工程研究

BACKGROUND:Unaccustomed exercise triggers skeletal muscle damage,but produces a specific training effect that reduces muscle re-injury to reduce pain-muscle memory. OBJECTIVE:Based on the etiology of delayed onset muscle soreness,to review the existence and possible mechanism of skeletal muscle memory in delayed onset muscle soreness and to present new insights into the prevention and treatment of delayed onset muscle soreness. METHODS:The first author searched in PubMed,Embase,Web of Science,CNKI and WanFang databases for relevant literature published from January 1990 to December 2022.The keywords were"DOMS,skeletal muscle memory,exercise skeletal muscle adaptation,repeat turn effect,exercise and autophagy,autophagy and inflammation"in English and Chinese,respectively.A total of 102 articles were finally included for review. RESULTS AND CONCLUSION:The etiology of delayed onset muscle soreness is currently believed to be an acute inflammatory response due to metabolic disorders,mechanical injury and oxidative stress,while exercise-induced skeletal muscle memory can reduce delayed onset muscle soreness and exercise re-injury.When the duration,frequency and intensity of centrifugal training are gradually increased,symptoms of the injury can be minimized or even avoided.Therefore,based on the mechanism of exercise-induced skeletal muscle memory,it is the future research direction to find more effective ways to prevent and alleviate exercise-induced muscle injury.This review aims to(1)clarify the existence of exercise-induced skeletal muscle memory;(2)explore the possible mechanisms of exercise-induced skeletal muscle memory and propose the relationship between this memory and skeletal muscle autophagy;and(3)provide new strategies for the prevention and treatment of delayed onset muscle soreness by improving the level of skeletal muscle autophagy.

A cross-sectional survey on the prevalence and risk factors of sarcopenia in the elderly in some areas of the Yunnan-Guizhou Plateau / 中国组织工程研究

BACKGROUND:Epidemiological research data on sarcopenia in China are concentrated in some provincial capitals and developed areas,while research on sarcopenia in the elderly in the Yunnan-Guizhou Plateau is at the initial stage,and there is still a lack of understanding of the development mechanism,influencing factors and prevention methods of sarcopenia. OBJECTIVE:Based on the 2019 Asian Sarcopenia Working Group Standard(AWGS2019),to assess sarcopenia in the elderly in the Yunnan-Guizhou Plateau,while analyzing the prevalence and risk factors of sarcopenia in the elderly. METHODS:A total of 1 327 elderly study subjects(650 males and 677 females)were recruited and their socio-demographic characteristics,clinical data and physical activity levels were collected.The prevalence of sarcopenia was screened using the AWGS2019 criteria.The possible influencing factors for sarcopenia were screened by univariate analysis,including χ2 test for comparing count data and t-test for comparing measurement data,and the indicators through univariate screening were included in the binary logistic regression model to assess the risk factors for sarcopenia,and then the odds ratio(OR)and 95%confidence interval(CI)were calculated. RESULTS AND CONCLUSION:The prevalence of sarcopenia in the elderly in the Yunnan-Guizhou Plateau was 14.62%(12.73%male and 16.49%female).Aging(OR=1.158,95%CI:1.133-1.185),female(OR=2.416,95%CI:1.629-3.586),fasting blood glucose≥7.0 mmol/L(OR=1.653,95%CI:1.071-2.551),smoking(OR=1.595,95%CI:1.043-2.438)and a low physical activity level(OR=1.778,95%CI:1.154-2.737)were all independent risk factors for sarcopenia,while body mass index was a protective factor for sarcopenia(OR=0.708,95%CI:0.583-0.859).These findings indicate that aging,female,fasting glucose≥7.0 mmol/L,smoking and low physical activity levels all increase the risk of sarcopenia,while increased body mass index can decrease the risk of sarcopenia.To conclude,the elderly(especially women)should maintain a healthy lifestyle and slightly higher body mass index levels during the aging process,thus reducing the risk of sarcopenia.

Effects of recombinant human collagen supplementation on extracellular matrix remodeling in mouse skeletal muscle after eccentric exercise / 中国组织工程研究

BACKGROUND:Collagen is the most abundant extracellular matrix component,which is closely related to the structure and function of the extracellular matrix of skeletal muscle,but the effect and mechanism of recombinant human collagen(rhC)produced by bioengineering technology on the extracellular matrix of skeletal muscle are unclear. OBJECTIVE:To investigate the effect of rhC supplementation on the remodeling of skeletal muscle extracellular matrix after eccentric exercise,thereby revealing the possible mechanism by which rhC improves the injury of skeletal muscle extracellular matrix and promote the recovery after exercise. METHODS:A total of 104 healthy male C57 mice aged 8 weeks old were randomly divided into control group(normal saline),low-dose rhC group(0.2 g/kg),medium-dose rhC group(1.0 g/kg),and high-dose rhC group(2.0 g/kg).Two mice in each group were selected after continuous 7 days of intragastric intervention,and organs were dissected for hematoxylin-eosin staining to determine inflammatory infiltrates.On the 8th day,the remaining mice were subjected to eccentric exercise.The structural changes of the skeletal muscle extracellular matrix were observed under scanning electron microscopy immediately(0),24,48,and 96 hours after eccentric exercise.Meanwhile,grip strength,creatine kinase activity,and protein levels of matrix metalloproteinases 2,9,14 and tissue inhibitor of metalloproteinase-2 in skeletal muscle were detected by western blot assay. RESULTS AND CONCLUSION:Hematoxylin-eosin staining results indicated that short-term rhC supplementation showed no significant effects on the morphology of the heart,liver,spleen and kidney.After one-time eccentric exercise,the recovery rate of grip strength in the medium-and high-dose rhC groups was significantly increased(P＜0.01).The trend of creatine kinase changes was consistent in all groups and there was no significant difference between groups.The recovery process of the extracellular matrix in the low-dose rhC group was faster than that in the control group,and the muscle tract membrane in the medium-and high-dose rhC groups was more complete.The protein level of matrix metalloproteinase 9 in the high-dose rhC group was significantly decreased(P＜0.05).The protein levels of matrix metalloproteinase 14 in the medium-and high-dose rhC groups were significantly decreased(P＜0.05).The protein levels of matrix metalloproteinase 2 in the medium-and high-dose rhC groups were significantly decreased(P＜0.05).Tissue inhibitor of metalloproteinase-2 protein levels in the medium-and high-dose rhC groups were significantly increased(P＜0.05).The ratio of matrix metalloproteinase 2 to tissue inhibitor of metalloproteinase-2 in each rhC group was significantly decreased(P＜0.05).To conclude,pre-supplementation of 1.0 and 2.0 g/kg rhC for 7 days can inhibit extracellular matrix degradation in skeletal muscle after exercise by modulating matrix metalloproteinases and matrix metalloproteinase inhibitors,thereby promoting recovery of skeletal muscle strength in mice.

Protective effect and mechanism of 3-nitro-N-methyl salicylamide on the skeletal muscle of rats with limb ischemia-reperfusion injury / 中国组织工程研究

BACKGROUND:Mitochondrial reactive oxygen bursts have been shown to play a key role in skeletal muscle ischemia-reperfusion injury.3-Nitro-N-methylsalicylamide(3-NNMS)can effectively reduce the electron transport rate and has a potential protective effect on limb ischemia-reperfusion injury,but there is no clear research and clinical application. OBJECTIVE:To investigate the protective effect of 3-NNMS on the skeletal muscle after limb ischemia-reperfusion injury in rats and its mechanism. METHODS:Forty healthy 8-week-old Sprague-Dawley rats were randomly divided into control group,0,25 and 125 μg/mL 3-NNMS groups,with 10 rats in each group.Animal models of limb ischemia-reperfusion injury were prepared in the latter three groups.3-NNMS was injected into the injury site 30 minutes before reperfusion.The animals were sacrificed 2 hours after reperfusion.Blood from the apical part of the heart,and the tissue of the rectus femoris muscle of the right lower limb were taken for testing.The pathological morphology of the rectus femoris muscle was detected by hematoxylin-eosin staining.Serum levels of creatine kinase found in the skeletal muscle(CK-MM),lactate dehydrogenase,and myeloperoxidase were detected using ELISA;the levels of nuclear factor κB,tumor necrosis factor α,interleukin 1β,cyclooxygenase 2,malondialdehyde,reactive oxygen species,superoxide dismutase,catalase and glutathione peroxidase in the rectus femoris muscle were measured;and adenosine triphosphate(ATP)level,ATPase activity,and mitochondrial respiratory control rate were tested. RESULTS AND CONCLUSION:Compared with the control group,the model rats with ischemia-reperfusion injury had increased serum levels of CK-MM,lactate dehydrogenase,and myeloperoxidase,increased levels of nuclear factor κB,tumor necrosis factor α,interleukin 1β,cyclooxygenase 2,malondialdehyde and reactive oxygen species in the rectus femoris muscle,decreased levels of catalase and glutathione peroxidase in the rectus femoris muscle,and reduced ATPase activity and mitochondrial respiratory control rate.Moreover,cell morphology was irregular,inflammatory cell infiltration was obvious,and the cells were swollen in rats after ischemia-reperfusion injury.Compared with the 0 μg/mL group,the serum CK-MM and lactate dehydrogenase levels decreased,the levels of nuclear factor κB and cyclooxygenase 2 in the rectus femoris muscle decreased,reactive oxygen species level decreased,and superoxide dismutase activity increased in the 25 μg/mL group;cell morphology was more regular,inflammatory cell infiltration was lighter,and cell swelling was alleviated.Compared with the 0 μg/mL group,the 125 μg/mL group had a reduction in the serum levels of CK-MM,lactate dehydrogenase,and myeloperoxidase and the levels of nuclear factor κB,tumor necrosis factor α,cyclooxygenase 2,malondialdehyde and reactive oxygen species in the rectus femoris muscle,as well as an increase in the levels of superoxide dismutase and glutathione peroxidase in the rectus femoris muscle,and mitochondrial respiratory control rate.Moreover,the cells were arranged neatly,the outline was clear and complete,and the inflammatory cell infiltration was light.To conclude,3-NNMS can alleviate the functional impairment of the skeletal muscle caused by limb ischemia-reperfusion,and its mechanism of action may be through improving mitochondrial function,reducing reactive oxygen species production,decreasing oxidative stress and inflammatory response,and thus reducing tissue damage and repairing skeletal muscle function.

Blood flow restriction training interventions for sarcopenia in older adults:biological mechanisms and proposed application protocols / 中国组织工程研究

BACKGROUND:Sarcopenia is a chronic condition that leads to strength loss and functional decline,increasing the risk of frailty,disability,falls,and death in older adults.Blood flow restriction training can be effective in the treatment of sarcopenia,but a comprehensive review of its advantages,disadvantages,biological mechanisms,and application options is lacking. OBJECTIVE:To review the advantages,limitations,and biological mechanisms of blood flow restriction training interventions for sarcopenia and to give recommendations for application protocols based on current published evidence. METHODS:A search of major databases was conducted for literature published in the time frame up to February 2023.The search terms were"blood flow restriction training,KAATSU,elderly,sarcopenia,muscle"in English and Chinese.Finally,82 included papers were compiled and analyzed. RESULTS AND CONCLUSION:Blood flow restriction training as an intervention for sarcopenia has been effective in peripheral muscle groups,but there are limitations in its application.Blood flow restriction training is highly operational and safe.This training can improve muscle strength and physical performance,but there are potential risks,including adverse events on skeletal muscle,cardiovascular and endothelial cells.Therefore,blood flow restriction training needs to be performed under scientific guidance and further studies are needed to verify its efficacy in patients with sarcopenia.The biological mechanisms of blood flow restriction training intervention in sarcopenia may include:increasing muscle hypertrophy due to reactive muscle congestion,improving muscle protein synthesis capacity,inducing metabolic stress adaptation,promoting skeletal muscle growth and repair,activating vascular endothelial growth factor signaling pathway to promote angiogenesis,and promoting satellite cell proliferation.However,these specific roles and combined effects of these mechanisms need to be determined by more in-depth studies.Blood flow restriction training interventions for sarcopenia are mainly influenced by training and cuffs.To avoid adverse events,it is recommended that 20%to 50%1RM,20 to 75 repetitions,2 to 3 times per week,30-60 seconds interval between sessions,smaller size cuffs with a pressurization value≤140 mmHg for upper limb training,and larger size cuffs with a pressurization value≤180 mmHg for lower limb training,usually 50%to 80%of the pressure value in the completely occluded artery.However,more research is needed on the training frequency and interval between sessions in older adults,and further research is needed on the optimal choice of cuff pressurization values.

Cell-of-origin for heterotopic ossification induced by bone morphogenetic protein 4 in skeletal muscle / 中国组织工程研究

BACKGROUND:Heterotopic ossification of skeletal muscle is a clinically serious complication.For heterotopic ossification of skeletal muscles,the cells involved in the process of heterotopic ossification remain unclear. OBJECTIVE:To investigate the involvement of myocytes,fascia cells,and endothelial cells in the process of heterotopic ossification in skeletal muscle and to observe the cell origin of heterotopic ossification in skeletal muscle induced by bone morphogenetic protein 4. METHODS:Both C2C12 cells and the myotubes formed by the C2C12 cells in the induction medium were cultured,and 500 ng/mL bone morphogenetic protein 4 was added to the medium respectively,and whether the C2C12 cells and myotubes continued to proliferate within 10 days under the treatment were observed under a microscope.Myogenic cells(L6,derived from rats)and fibroblast-derived cells(derived from human)were co-cultured.After treatment with 500 ng/mL bone morphogenetic protein 4 and 10 ng/mL transforming growth factor-β,osteogenic and chondrogenic differentiation potential within 21 days were observed using Safranine O staining and Alcian blue staining.Using transgenic animal FVB/N-TgN(TIE2-LacZ)182Sato mice,15 μL of adeno-associated virus-bone morphogenetic protein 4(5×1010 PFU/mL)were implanted in the thigh muscle space of genetic mice for 10 and 14 days.X-gal staining was used to observe the formation of new blood vessel endothelium in the differentiated bone. RESULTS AND CONCLUSION:(1)Bone morphogenetic protein 4 caused myotube breakdown and increased C2C12 cell proliferation.Compared with other groups,the pure fibroblast-derived cell group had a higher area of positive alcian blue and safarin O staining(P<0.05)and a lower area of alkaline phosphatase staining(P<0.05),while the pure L6 group had a bigger area of alkaline phosphatase staining(P<0.05)but a smaller area of positive alcian blue and safarin O staining(P<0.05).(2)Transplantation of adeno-associated virus-bone morphogenetic protein 4-adsorbed gelatin sponge into FVB/N-TgN(TIE2-LacZ)182Sato mice resulted in heterotopic ossification.(3)X-gal staining results demonstrated that there was no obvious staining in chondrocytes and differentiated bones and Tie2+ endothelial cells did not participate in the formation of the alienated bone.(4)These findings verify that fibroblasts are the primary source of osteoblasts during the adeno-associated virus-bone morphogenetic protein 4-induced ectopic endochondral ossification in skeletal muscle,but myogenic cells are the main source of osteoblasts.Tie2+ endothelial cells might not be the cell source for cartilage and bone.