Low skeletal muscle mass and high visceral adiposity are associated with recurrence of acute cholecystitis after conservative management:A propensity score-matched cohort study

Background:Recurrent acute cholecystitis(RAC)can occur after non-surgical treatment for acute cholecystitis(AC),and can be more severe in comparison to the first episode of AC.Low skeletal muscle mass or adiposity have various effects in several diseases.We aimed to clarify the relationship between RAC and body parameters.Methods:Patients with AC who were treated at our hospital between January 2011 and March 2022 were enrolled.The psoas muscle mass and adipose tissue area at the third lumbar level were measured using computed tomography at the first episode of AC.The areas were divided by height to obtain the psoas muscle mass index(PMI)and subcutaneous/visceral adipose tissue index(SATI/VATI).According to median VATI,SATI and PMI values by sex,patients were divided into the high and low PMI groups.We performed propensity score matching to eliminate the baseline differences between the high PMI and low PMI groups and analyzed the cumulative incidence and predictors of RAC.Results:The entire cohort was divided into the high PMI(n=81)and low PMI(n=80)groups.In the propensity score-matched cohort there were 57 patients in each group.In Kaplan-Meier analysis,the low PMI group and the high VATI group had a significantly higher cumulative incidence of RAC than their counterparts(log-rank P=0.001 and 0.015,respectively).In a multivariate Cox regression analysis,the hazard ratios of low PMI and low VATI for RAC were 5.250(95%confidence interval 1.083-25.450,P=0.039)and 0.158(95%confidence interval:0.026-0.937,P=0.042),respectively.Conclusions:Low skeletal muscle mass and high visceral adiposity were independent risk factors for RAC.

SWIR FluorescenceImaging In Vivo Monitoring and Evaluating Implanted M2 Macrophages in Skeletal Muscle Regeneration

Skeletal muscle has a robust regeneration ability that is impaired by severe injury,disease,and aging.resulting in a decline in skeletal muscle function.Therefore,improving skeletal muscle regeneration is a key challenge in treating skeletal muscle-related disorders.Owing to their significant role in tissue regeneration,implantation of M2 macrophages(M2MФ)has great potential for improving skeletal muscle regeneration.Here,we present a short-wave infrared(SWIR)fluorescence imaging technique to obtain more in vivo information for an in-depth evaluation of the skeletal muscle regeneration effect after M2MФtransplantation.SWIR fluorescence imaging was employed to track implanted M2MФin the injured skeletal muscle of mouse models.It is found that the implanted M2MФaccumulated at the injury site for two weeks.Then,SWIR fluorescence imaging of blood vessels showed that M2MФimplantation could improve the relative perfusion ratio on day 5(1.09±0.09 vs 0.85±0.05;p=0.01)and day 9(1.38±0.16 vs 0.95±0.03;p=0.01)post-injury,as well as augment the degree of skeletal muscle regencration on day 13 post-injury.Finally,multiple linear regression analyses determined that post-injury time and relative perfusion ratio could be used as predictive indicators to evaluate skeletal muscle regeneration.These results provide more in vivo details about M2MФin skeletal muscle regeneration and confirm that M2MФcould promote angiogenesis and improve the degree of skeletal muscle repair,which will guide the research and development of M2MФimplantation to improve skeletal muscle regeneration.

Temporal and spatial regulation of biomimetic vascularization in 3D-printed skeletal muscles

In the intricate skeletal muscle tissue,the symbiotic relationship between myotubes and their supporting vasculature is pivotal in delivering essential oxygen and nutrients.This study explored the complex interplay between skeletal muscle and endothelial cells in the vascularization ofmuscle tissue.By harnessing the capabilities of three-dimensional(3D)bioprinting and modeling,we developed a novel approach involving the co-construction of endothelial and muscle cells,followed by their subsequent differentiation.Our findings highlight the importance of the interaction dynamics between these two cell types.Notably,introducing endothelial cells during the advanced phases of muscle differentiation enhanced myotube assembly.Moreover,it stimulated the development of the vascular network,paving the way for the early stages of vascularized skeletal muscle development.The methodology proposed in this study indicates the potential for constructing large-scale,physiologically aligned skeletal muscle.Additionally,it highlights the need for exploring the delicate equilibrium and mutual interactions between muscle and endothelial cells.Based on the multicell-type interaction model,we can predict promising pathways for constructing even more intricate tissues or organs.

Catalpa bignonioides extract improves exercise performance through regulation of growth and metabolism in skeletal muscles

Objective:To evaluate the effects of Catalpa bignonioides fruit extract on the promotion of muscle growth and muscular capacity in vitro and in vivo.Methods:Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.Cell proliferation was assessed using a 5-bromo-2’-deoxyuridine(BrdU)assay kit.Western blot analysis was performed to determine the protein expressions of related factors.The effects of Catalpa bignonioides extract were investigated in mice using the treadmill exhaustion test and whole-limb grip strength assay.Chemical composition analysis was performed using high-performance liquid chromatography(HPLC).Results:Catalpa bignonioides extract increased the proliferation of C2C12 mouse myoblasts by activating the Akt/mTOR signaling pathway.It also induced metabolic changes,increasing the number of mitochondria and glucose metabolism by phosphorylating adenosine monophosphate-activated protein kinase.In an in vivo study,the extract-treated mice showed improved motor abilities,such as muscular endurance and grip strength.Additionally,HPLC analysis showed that vanillic acid may be the main component of the Catalpa bignonioides extract that enhanced muscle strength.Conclusions:Catalpa bignonioides improves exercise performance through regulation of growth and metabolism in skeletal muscles,suggesting its potential as an effective natural agent for improving muscular strength.

Acupotomy ameliorates knee osteoarthritis-related collagen deposition and fibrosis in rabbit skeletal muscle through the TGF-β/Smad pathway

Objective:To investigate the effects of acupotomy on skeletal muscle fibrosis and collagen deposition in a rabbit knee osteoarthritis(KOA)model.Methods: Rabbits(n=18)were randomly divided into control,KOA,and KOA+acupotomy(Apo)groups(n=6).The rabbits in the KOA and Apo groups were modeled using the modified Videman's method for 6 weeks.After modeling,the Apo group was subjected to acupotomy once a week for 3 weeks on the vastus medialis,vastus lateralis,rectus femoris,biceps femoris,and anserine bursa tendons around the knee.The behavior of all animals was recorded,rectus femoris tissue was obtained,and histomorphological changes were observed using Masson staining and transmission electron microscopy.The expression of transforming growth factor-β1(TGF-β1),Smad 3,Smad 7,fibrillar collagen types I(Col-I)and III(Col-III)was detected using Western blot and real-time polymerase chain reaction(RT-PCR).Results: Histological analysis revealed that acupotomy improved the microstructure and reduced the collagen volume fraction of rectus femoris,compared with the KOA group(P=.034).Acupotomy inhibited abnormal collagen deposition by modulating the expression of fibrosis-related proteins and mRNA,thus preventing skeletal muscle fibrosis.Western blot and RT-PCR analysis revealed that in the Apo group,Col-I,and Col-III protein levels were significantly lower than those in the KOA group(both P<.01),same as Col-I and Col-III mRNA levels(P=.0031;P=.0046).Compared with the KOA group,the protein levels of TGF-β1 and Smad 3 were significantly reduced(both P<.01),as were the mRNA levels of TGF-β1 and Smad 3(P=.0007;P=.0011).Conversely,the levels of protein and mRNA of Smad 7 were significantly higher than that in the KOA group(P<.01;P=.0271).Conclusion: Acupotomy could alleviate skeletal muscle fibrosis and delay KOA progress by inhibiting collagen deposition through the TGF-β/Smad pathway in the skeletal muscle of KOA rabbits.

Mitochondrial dysfunction in type 2 diabetes:A neglected path to skeletal muscle atrophy

Over the course of several decades,robust research has firmly established the significance of mitochondrial pathology as a central contributor to the onset of skeletal muscle atrophy in individuals with diabetes.However,the specific intricacies governing this process remain elusive.Extensive evidence highlights that individuals with diabetes regularly confront the severe consequences of skeletal muscle degradation.Deciphering the sophisticated mechanisms at the core of this pathology requires a thorough and meticulous exploration into the nuanced factors intricately associated with mitochondrial dysfunction.

In vivo measurement of NADH fluorescence lifetime in skeletal muscle via -ber-coupled time-correlated single photon counting

Nicotinamide adenine dinucleotide(NADH)is a cofactor that serves to shuttle electrons during metabolic processes such as glycolysis,the tricarboxylic acid cycle,and oxidative phosphorylation(OXPHOS).NADH is autofluorescent,and itsfluorescence lifetime can be used to infer metabolic dynamics in living cells.Fiber-coupled time-correlated single photon counting(TCSPC)equipped with an implantable needle probe can be used to measure NADH lifetime in vivo,enabling investigation of changing metabolic demand during muscle contraction or tissue regeneration.This study illustrates a proof of concept for point-based,minimally-invasive NADHfluorescence lifetime measurement in vivo.Volumetric muscle loss(VML)injuries were created in the left tibialis anterior(TA)muscle of male Sprague Dawley rats.NADH lifetime measurements were collected before,during,and after a 30 s tetanic contraction in the injured and uninjured TA muscles,which was subsequently-t to a biexponential decay model to yield a metric of NADH utilization(cytoplasmic vs protein-bound NADH,the A11/A22 ratio).On average,this ratio was higher during and after contraction in uninjured muscle compared to muscle at rest,suggesting higher levels of free NADH in contracting and recovering muscle,indicating increased rates of glycolysis.In injured muscle,this ratio was higher than uninjured muscle overall but decreased over time,which is consistent with current knowledge of inflammatory response to injury,suggesting tissue regeneration has occurred.These data suggest that-ber-coupled TCSPC has the potential to measure changes in NADH binding in vivo in a minimally invasive manner that requires further investigation.

Crosstalk among canonical Wnt and Hippo pathway members in skeletal muscle and at the neuromuscular junction

Skeletal muscles are essential for locomotion,posture,and metabolic regulation.To understand physiological processes,exercise adaptation,and muscle-related disorders,it is critical to understand the molecular pathways that underlie skeletal muscle function.The process of muscle contra ction,orchestrated by a complex interplay of molecular events,is at the core of skeletal muscle function.Muscle contraction is initiated by an action potential and neuromuscular transmission requiring a neuromuscular junction.Within muscle fibers,calcium ions play a critical role in mediating the interaction between actin and myosin filaments that generate force.Regulation of calcium release from the sarcoplasmic reticulum plays a key role in excitation-contraction coupling.The development and growth of skeletal muscle are regulated by a network of molecular pathways collectively known as myogenesis.Myogenic regulators coordinate the diffe rentiation of myoblasts into mature muscle fibers.Signaling pathways regulate muscle protein synthesis and hypertrophy in response to mechanical stimuli and nutrient availability.Seve ral muscle-related diseases,including congenital myasthenic disorders,sarcopenia,muscular dystrophies,and metabolic myopathies,are underpinned by dys regulated molecular pathways in skeletal muscle.Therapeutic interventions aimed at preserving muscle mass and function,enhancing regeneration,and improving metabolic health hold promise by targeting specific molecular pathways.Other molecular signaling pathways in skeletal muscle include the canonical Wnt signaling pathway,a critical regulator of myogenesis,muscle regeneration,and metabolic function,and the Hippo signaling pathway.In recent years,more details have been uncovered about the role of these two pathways during myogenesis and in developing and adult skeletal muscle fibers,and at the neuromuscular junction.In fact,research in the last few years now suggests that these two signaling pathways are interconnected and that they jointly control physiological and pathophysiological processes in muscle fibers.In this review,we will summarize and discuss the data on these two pathways,focusing on their concerted action next to their contribution to skeletal muscle biology.However,an in-depth discussion of the noncanonical Wnt pathway,the fibro/a dipogenic precursors,or the mechanosensory aspects of these pathways is not the focus of this review.

Exploring the therapeutic effect of Xiaoyan d ecoction on lung cancer cachexia skeletal muscle atrophy based on L3-SMI

Background:Lung cancer cachexia has received widespread attention as one of the most common complications in patients with advanced lung cancer.As a multifactorial syndrome,lung cancer cachexia is characterized by a persistent decline in muscle mass that cannot be reversed by conventional nutrition Xiaoyan d ecoction can promote appetite and improve skeletal muscle mass in patients with lung cancer cachexia,while the third lumbar skeletal muscle index(L3-SMI)is able to determine whole-body skeletal muscle mass.To analyze the relationship between L3-SMI and hematological indexes and lung cancer cachexia,and to study the clinical efficacy of Xiaoyan decoction on skeletal muscle atrophy in lung cancer cachexia patients,with the aim of providing a reference basis for the early diagnosis and treatment of lung cancer cachexia patients and skeletal muscle atrophy.Methods:148 patients who were diagnosed with lung cancer in the Department of Oncology of the First Affiliated Hospital of Tianjin University of Traditional Chinese Medicine from January 2020 to December 2022 were included,and were divided into cachexia and non-cachexia groups according to the diagnostic criteria of cachexia,and analyzed the differences of hematological indexes and L3-SMI between cachexia patients and non-cachexia patients.And the patients with cachexia were divided into control group and treatment group,analyzed and compared the changes of body mass index(BMI),L 3-SMI,Karnofsky functional status score,albumin and other hematological indexes of the two groups before and after the treatment,and evaluated the safety of the Xiaoyan decoction in the treatment of cachexia.Results:A total of 148 lung cancer patients were included in this study,including 67 patients in the cachexia group and 81 patients in the non-cachexia group.According to the pre-treatment statistical analysis,the BMI of patients in the cachexia group was lower than that of patients in the non-cachexia group(P<0.05);among the biochemical function indexes,the proportions of creatinine(P<0.05),total protein(P<0.05),The levels of albumin in the cachexia group were significantly lower(P<0.05)compared to the non-cachexia group;in the cachexia group,both males and females had lower L3-SMIs than in the non-cachexia group(P<0.05).A total of 62 cases of lung cancer cachexia were studied,30 cases in the control group and 32 cases in the treatment group,according to statistical analysis,BMI was significantly different before and after treatment(P<0.05);L3-SMI was significantly different in the treatment group before and after treatment(P<0.05);Karnofsky significantly differed in the treatment group before and after treatment(P<0.05);and there was a significant difference in albumin before and after(P<0.05).Conclusion:Cachexia patients had significantly lower third lumbar skeletal muscle mass than non-cachexia patients,according to this study;Xiaoyan decoction was able to improve skeletal muscle mass,nutritional status as well as functional status of patients with cachexia in lung cancer,among others.

Pickering emulsion transport in skeletal muscle tissue:A dissipative particle dynamics simulation approach

Lymph node targeting is a commonly used strategy for particulate vaccines,particularly for Pickering emulsions.However,extensive research on the internal delivery mechanisms of these emulsions,especially the complex intercellular interactions of deformable Pickering emulsions,has been surprisingly sparse.This gap in knowledge holds significant potential for enhancing vaccine efficacy.This study aims to address this by summarizing the process of lymph-node-targeting transport and introducing a dissipative particle dynamics simulation method to evaluate the dynamic processes within cell tissue.The transport of Pickering emulsions in skeletal muscle tissue is specifically investigated as a case study.Various factors impacting the transport process are explored,including local cellular tissue environmental factors and the properties of the Pickering emulsion itself.The simulation results primarily demonstrate that an increase in radial repulsive interaction between emulsion particles can decrease the transport efficiency.Additionally,larger intercellular gaps also diminish the transport efficiency of emulsion droplet particles due to the increased motion complexity within the intricate transport space compared to a single channel.This study sheds light on the nuanced interplay between engineered and biological systems influencing the transport dynamics of Pickering emulsions.Such insights hold valuable potential for optimizing transport processes in practical biomedical applications such as drug delivery.Importantly,the desired transport efficiency varies depending on the specific application.For instance,while a more rapid transport might be crucial for lymph-node-targeted drug delivery,certain applications requiring a slower release of active components could benefit from the reduced transport efficiency observed with increased particle repulsion or larger intercellular gaps.

Clemastine in remyelination and protection of neurons and skeletal muscle after spinal cord injury

Spinal cord injuries affect nearly five to ten individuals per million every year. Spinal cord injury causes damage to the nerves, muscles, and the tissue surrounding the spinal cord. Depending on the severity, spinal injuries are linked to degeneration of axons and myelin, resulting in neuronal impairment and skeletal muscle weakness and atrophy. The protection of neurons and promotion of myelin regeneration during spinal cord injury is important for recovery of function following spinal cord injury. Current treatments have little to no effect on spinal cord injury and neurogenic muscle loss. Clemastine, an Food and Drug Administration-approved antihistamine drug, reduces inflammation, protects cells, promotes remyelination, and preserves myelin integrity. Recent clinical evidence suggests that clemastine can decrease the loss of axons after spinal cord injury, stimulating the differentiation of oligodendrocyte progenitor cells into mature oligodendrocytes that are capable of myelination. While clemastine can aid not only in the remyelination and preservation of myelin sheath integrity, it also protects neurons. However, its role in neurogenic muscle loss remains unclear. This review discusses the pathophysiology of spinal cord injury, and the role of clemastine in the protection of neurons, myelin, and axons as well as attenuation of skeletal muscle loss following spinal cord injury.

Selenoproteins synergistically protect porcine skeletal muscle from oxidative damage via relieving mitochondrial dysfunction and endoplasmic reticulum stress

Background The skeletal muscle of pigs is vulnerable to oxidative damage,resulting in growth retardation.Selenoproteins are important components of antioxidant systems for animals,which are generally regulated by dietary selenium(Se)level.Here,we developed the dietary oxidative stress(DOS)-inducing pig model to investigate the protective effects of selenoproteins on DOS-induced skeletal muscle growth retardation.Results Dietary oxidative stress caused porcine skeletal muscle oxidative damage and growth retardation,which is accompanied by mitochondrial dysfunction,endoplasmic reticulum(ER)stress,and protein and lipid metabolism disorders.Supplementation with Se(0.3,0.6 or 0.9 mg Se/kg)in form of hydroxy selenomethionine(OH-SeMet)linearly increased muscular Se deposition and exhibited protective effects via regulating the expression of selenotranscriptome and key selenoproteins,which was mainly reflected in lower ROS levels and higher antioxidant capacity in skeletal muscle,and the mitigation of mitochondrial dysfunction and ER stress.What’s more,selenoproteins inhibited DOS induced protein and lipid degradation and improved protein and lipid biosynthesis via regulating AKT/mTOR/S6K1 and AMPK/SREBP-1 signalling pathways in skeletal muscle.However,several parameters such as the activity of GSH-Px and T-SOD,the protein abundance of JNK2,CLPP,SELENOS and SELENOF did not show dose-dependent changes.Notably,several key selenoproteins such as MSRB1,SELENOW,SELENOM,SELENON and SELENOS play the unique roles during this protection.Conclusions Increased expression of selenoproteins by dietary OH-SeMet could synergistically alleviate mitochondrial dysfunction and ER stress,recover protein and lipid biosynthesis,thus alleviate skeletal muscle growth retardation.Our study provides preventive measure for OS-dependent skeletal muscle retardation in livestock husbandry.

A 1.1 Mb duplication CNV on chromosome 17 contributes to skeletal muscle development in Boer goats

The Boer goat is one of the top meat breeds in modern animal husbandry and has attracted widespread attention for its unique growth performance.However,the genetic basis of muscle development in the Boer goat remains obscure.In this study,we identified specific structural variants in the Boer goat based on genome-wide selection signals and analyzed the basis of the molecular heredity of related candidate genes in muscle development.A total of9 959 autosomal copy number variations(CNVs) were identified through selection signal analysis in 127 goat genomes.Specifically,we confirmed that the highest signal CNV(HSV) was a chromosomal arrangement containing an approximately 1.11 Mb(CHIR17:60062304-61171840 bp) duplicated fragment inserted in reverse orientation and a 5 362 bp deleted region(CHIR17:60145940-60151302 bp) with overlapping genes(e.g.,ARHGAP10,NR3C2,EDNRA,PRMT9,and TMEM184C).The homozygous duplicated HSV genotype(+/+) was found in 96% of Boer goats but was not detected in Eurasian goats and was only detected in 4% of indigenous African goats.The expression network of three candidate genes(ARHGAP10,NR3C2,and EDNRA)regulating dose transcription was constructed by RNA sequencing.Results indicated that these genes were involved in the proliferation and differentiation of skeletal muscle satellite cells(SMSCs) and their overexpression significantly increased the expression of SAA3.The HSV of the Boer goat contributed to superior skeletal muscle growth via the dose effects of overlapping genes.

The role of 5′-adenosine monophosphate-activated protein kinase(AMPK)in skeletal muscle atrophy

As a key coordinator of metabolism,AMP-activated protein kinase(AMPK)is vitally involved in skeletal muscle maintenance.AMPK exerts its cellular effects through its function as a serine/threonine protein kinase by regulating many downstream targets and plays important roles in the development and growth of skeletal muscle.AMPK is activated by phosphorylation and exerts its function as a kinase in many processes,including synthesis and degradation of proteins,mitochondrial biogenesis,glucose uptake,and fatty acid and cholesterol metabolism.Skeletal muscle atrophy is a result of various diseases or disorders and is characterized by a decrease in muscle mass.The pathogenesis and therapeutic strategies of skeletal muscle atrophy are still under investigation.In this review,we discuss the role of AMPK in skeletal muscle metabolism and atrophy.We also discuss targeting AMPK for skeletal muscle treatment,including exercise,AMPK activators including 5-amino-4-imidazolecarboxamide ribonucleoside and metformin,and low-level lasers.These studies show the important roles of AMPK in regulating muscle metabolism and function;thus,the treatment of skeletal muscle atrophy needs to take into account the roles of AMPK.

SCSMRD: A database for single-cell skeletal muscle regeneration

Skeletal muscle regeneration is a complex process where various cell types and cytokines are involved.Single-cell RNA-sequencing (scRNA-seq) provides the opportunity to deconvolute heterogeneous tissue into individual cells based on their transcriptomic profiles.Recent scRNA-seq studies on mouse muscle regeneration have provided insights to understand the transcriptional dynamics that underpin muscle regeneration.However,a database to investigate gene expression profiling during skeletal muscle regeneration at the single-cell level is lacking.Here,we collected over 105 000 cells at 7 key regenerative time-points and non-injured muscles and developed a database,the Singlecell Skeletal Muscle Regeneration Database (SCSMRD).SCSMRD allows users to search the dynamic expression profiles of genes of interest across different cell types during the skeletal muscle regeneration process.It also provides a network to show the activity of regulons in different cell types at different time points.Pesudotime analysis showed the state changes trajectory of muscle stem cells (MuSCs) during skeletal muscle regeneration.This database is freely available at https://scsmrd.fengs-lab.com.

Kaempferol improves glucose uptake in skeletal muscle via an AMPK-dependent mechanism

Insulin resistance is a hallmark of type-2 diabetes(T2D)pathogenesis.Because skeletal muscle(SkM)is the major tissue for insulin-mediated glucose disposal,insulin resistance in SkM is considered a major risk factor for developing T2D.Thus,the identifi cation of compounds that enhance the ability of SkM to take up glucose is a promising strategy for preventing T2D.Our previous work showed that kaempferol,a fl avonol present in many foods,improves insulin sensitivity in obese mice,however,the mechanism underlying this beneficial action remains unclear.Here,we show that kaempferol directly stimulates glucose uptake and prevents lipotoxicity-impaired glucose uptake in primary human SkM.Kaempferol stimulates Akt phosphorylation in a time-dependent manner in human SkM cells.The effect of kaempferol on glucose uptake was blunted by inhibition of glucose transporter 4,phosphoinositide 3-kinase(PI3K),or AMPK.In addition,kaempferol induced AMPK phosphorylation,and inhibition of AMPK prevented kaempferol-stimulated Akt phosphorylation.In vivo,kaempferol administration induced rapid glucose disposal accompanied with increased Akt and AMPK phosphorylation in SkM tissue of the mice.Taken together,these fi ndings suggest that kaempferol stimulates glucose uptake in SkM via an AMPK/Akt dependent mechanism,and it may be a viable therapeutic agent for insulin resistance.

Micro RNA transcriptome of skeletal muscle during yak development reveals that miR-652 regulates myoblasts differentiation and survival by targeting ISL1

The growth and development of skeletal muscle also determine the meat production of yak, ultimately affecting the economic benefits. Hence, improving growth performance is a top priority in the yak industry. Skeletal muscle development is a complex process involving the regulation of several genes, including microRNAs(miRNAs). However,the transcription of miRNAs in yak skeletal muscle during prenatal to postnatal stages is unknown. We used small RNA sequencing(small RNA-Seq) to determine the global miRNAs of longissimus dorsi muscle from yak(the samples were collected from three fetuses and three adults). Totally 264 differently expressed miRNAs(|log2(fold change)|>1and P-value≤0.05) were detected between the two groups. Gene Ontology(GO) and Kyoto Encyclopedia of Genes and Genomes(KEGG) analysis showed that differently expressed miRNAs-targeted genes participated in pathways associated with muscle development, such as MAPK, PI3K-Akt, and Hippo signaling pathways, etc. MiR-652, which was up-regulated in the fetal group, was transfected into C2C12 myoblasts to examine its role. miR-652 promoted(P≤0.05)proliferation and differentiation, but inhibited(P≤0.001) apoptosis at early period. Furthermore, miR-652 reduced(P≤0.001) the proportion of C2C12 myoblasts in the G1 phase while increasing(P≤0.01) the proportion of cells in the S and G2 phases. Dual-luciferase reporter assays indicated that ISL1 served as a target of miR-652. In general, these findings expand our understanding of yak skeletal muscle miRNAs, and suggested that miR-652 probably regulated myogenesis by regulating ISL1.

Age-dependent Changes in Skeletal Muscle Mass and Visceral Fat Area in a Chinese Population

Objective:The present study was conducted to demonstrate the age-dependent changes in skeletal muscle mass and visceral fat area in a population of Chinese adults aged 30-92 years old.Methods:A total of 6669 healthy Chinese men and 4494 healthy Chinese women aged 30-92 years old were assessed for their skeletal muscle mass and visceral fat area.Results:The results showed age-dependent decreases in the total skeletal muscle mass indexes in both men and women aged 40-92 years old as well as age-dependent increases in the visceral fat area in men aged 30-92 years old and in women aged 30-80 years old.Multivariate regression models showed that the total skeletal muscle mass index was positively associated with the body mass index and negatively associated with the age and visceral fat area in both sexes.Conclusion:The loss of skeletal muscle mass becomes obvious at approximately 50 years of age,and the visceral fat area commences to increase at approximately 40 years of age in this Chinese population.

Effects of Astragalus membranaceus on Energy Metabolism and Expression of CNTF Protein in Skeletal Muscle of Exercise-induced Fatigue Rats

[Objectives]This study was conducted to investigate the effects of Astragalus membranaceus in different groups on energy metabolism and CNTF protein expression in skeletal muscle of exercise-induced fatigue rats.[Methods]Thirty-five clean male SD rats were randomly divided into a normal group,and low-,meddle-and high-dose groups of A.membranaceus aqueous solution,with 7 rats in each group.The low-dose,medium-dose and high-dose groups were given by gavage at 0.65,1.3 and 2.6 g/kg,respectively,while the normal group and the model group were given normal food and water.The weight of rats was observed.The contents of serum urea,lactate,muscle glycogen,liver glycogen and CNTF expression were detected.[Results]After modeling,compared with the normal group,the serum lactate and urea contents of rats in the model group significantly increased(P<0.01),while the muscle glycogen content(P<0.01)and liver glycogen content(P<0.05)of the skeletal muscle significantly decreased.Compared with the model group,the low-,meddle-and high-dose groups of A.membranaceus significantly reduced the levels of lactate and urea in serum(P<0.01),while the levels of muscle glycogen and liver glycogen in the skeletal muscle significantly increased(P<0.01,P<0.05).[Conclusions]This study provides a good research foundation for the treatment of exercise-induced fatigue using traditional Chinese herb A.membranaceus in modern clinical practice.

Analysis and Identification of miRNA Expression in the Skeletal Muscle of Sichuan White Rabbits

[Objectives]miRNAs play an important role in the proliferation and differentiation of different myoblasts.This study was conducted to elucidate the complex genetic mechanisms that affect the meat production performance of Sichuan white rabbits and reveal the regulatory role of miRNAs in their muscle growth and meat quality formation.[Methods]Three constructed skeletal muscle libraries of Sichuan white rabbits aged six months were sequenced by the solexa technology to identify known miRNAs,predict new miRNAs and construct an expression profile of muscle miRNAs.[Results]A total of 511 known miRNAs and 42 miRNAs were detected in 34089472 pure sequences,and the proportion of miRNAs with a length of 22 nt was the highest.The number of known miRNA sequences accounted for 71.38%of pure sequences,which was much higher than the proportion of other types of RNAs.The proportion of sequences from exons was 0.38%,indicating a low degree of mRNA degradation in the samples.Base U had the highest proportion at the first position,and the bases with the highest proportions at positions 8 and 10 were U and A,respectively.Muscle-specific miRNAs(miR-1,miR-133,and miR-206)ranked in the top 10 in terms of expression level.The number and expression levels of new miRNAs were lower than those of known miRNAs.The length distribution,base bias at different positions and expression profile characteristics of miRNAs might be related to the biological function of miRNAs in regulating muscle proliferation and differentiation and the action mechanisms with target genes.[Conclusions]The identification and expression of miRNAs in muscle tissues of Sichuan white rabbits will help to understand the complex molecular mechanisms of meat production performance and provide a theoretical basis for the functional research of miRNAs in meat rabbits.