OBJECTIVES:The aims of the study are to investigate the effect of electrical stimulation on disuse muscular atrophy induced by immobilization (IM) and to explore the role of PERK signal and Parkin-dependent mitophagy in this process.DESIGN:In the first subexperiment, 24 rabbits were divided into four groups, which underwent different periods of IM. In the second subexperiment, 24 rabbits were divided into four groups on average in accordance with different kinds of interventions. To test the time-dependent changes of rectus femoris after IM, and to evaluate the effect of electrical stimulation, the wet weights, cross-sectional area and fat deposition of rectus femoris were assessed in this study, along with the protein levels of atrogin-1, p-PERK, Parkin, and COXIV.RESULTS:The wet weights and cross-sectional area decreased, and the fat deposition increased in rectus femoris after IM, along with the elevated protein levels of atrogin-1, p-PERK, Parkin, and decreased protein levels of COXIV. The above histomorphological and molecular changes can be partially ameliorated by electrical stimulation.CONCLUSIONS:Immobilization of unilateral lower limb could induce rectus femoris atrophy, which can be partially rectified by electrical stimulation. PERK signal and Parkin-mediated mitophagy may be the mechanisms by which electrical stimulation can play a significant role.

As an important exercise and energy metabolism organ of the human body, the normal maintenance of skeletal muscle mass is essential for the body to perform normal physiological functions. The autophagy-lysosome (AL) pathway is a physiological or pathological mechanism that is ubiquitous in normal and diseased cells. It plays a key role in the maintaining of protein balance, removing damaged organelles, and the stability of internal environment. The smooth progress of the autophagy process needs to go through multiple steps, which are completed under the coordinated action of multiple factors. Autophagy maintains the muscle homeostasis of a healthy body by removing cell components such as damaged myofibrils and isolated cytoplasmic proteins. Autophagy could also provide the initial energy required for cell proliferation, promote muscle regeneration and remodeling after injury. At the same time, autophagy disorder is also an important cause of age-related skeletal muscle atrophy. Autophagy could affect the response of skeletal muscle to exercise, and increasing the level of basic autophagy is beneficial to improve the adaptive response of skeletal muscle to exercise. This article summarizes the role and pathways of autophagy in the maintenance of skeletal muscle quality, in order to provide effective rehabilitation strategies for clinical prevention and treatment of muscle atrophy.

The study aimed to investigate the effect of low-frequency electrical stimulation (LFES) on disuse muscle atrophy and its mechanism in a rabbit model of knee extension contracture. This study involved two experiments. In the time-point experiment, 24 rabbits were randomly divided into 4 groups: Control 1 (Ctrl1 group), immobilization for 2 weeks (I-2 group), immobilization for 4 weeks (I-4 group), and immobilization for 6 weeks (I-6 group). In the intervention experiment, 24 rabbits were randomly divided into 4 groups: Control 2 (Ctrl2 group), electrical stimulation (ESG group), natural recovery (NRG group), and electrical stimulation treatment (ESTG group). All intervention effects were assessed by evaluating the knee joint range of motion (ROM), cross-sectional area (CSA) of the rectus femoris muscle, and expression of autophagy-related proteins. The time-point experiment showed that immobilization reduced the knee ROM, reduced the rectus femoris muscle CSA, and activated autophagy in skeletal muscle. The levels of five autophagy-related proteins [mammalian target of rapamycin (mTOR), phosphorylated mTOR (p-mTOR), autophagy-related protein 7 (Atg7), p62, and microtubule-associated protein light chain 3B-II (LC3B-II)] were significantly elevated in the skeletal muscle of the I-4 group. The intervention experiment further showed that LFES significantly improved the immobilization-induced reductions in ROM and CSA. Additionally, LFES resulted in a significant decrease in the protein expression of mTOR, p-mTOR, Atg7, p62, and LC3B-II in the rectus femoris muscle. LFES alleviates immobilization-evoked disuse muscle atrophy possibly by inhibiting autophagy in the skeletal muscle of rabbits.

Background: The aim of this study was to investigate the therapeutic effect of electrical stimulation on disuse muscular atrophy in a rabbit model of knee joint contracture and explore the role of endoplasmic reticulum stress-induced Parkin-dependent mitophagy in this process.Methods: Two sub-experiments were carried out successively in our study. In the first sub-experiment, 24 rabbits were divided into four groups on average based on the immobilization time: Ctrl 1, I-2, I-4, and I-6 groups. In the second sub-experiment, 24 rabbits were also divided into four groups on average in accordance with the process mode: Ctrl2, ES, NR, and EST groups. To test the time-dependent changes of the rectus femoris muscles after immobilization in rabbits, and to evaluate the effect of electrical stimulation on the atrophic rectus femoris muscles, the wet weights of rectus femoris muscles were assessed in this study, along with the protein levels of atrogin-1, p-PERK, Parkin and COXIV.Results: The wet weights of rectus femoris muscles, the protein levels of atrogin-1, p-PERK and Parkin increased after immobilization. It was also revealed that the protein levels of COXIV decreased after immobilization. Electrical stimulation was effective against muscle atrophy, the elevated expression of atrogin-1, p-PERK, Parkin, and the decreased expression of COXIV.Conclusions: Immobilization of unilateral lower limb could induce rectus femoris muscle atrophy, endoplasmic reticulum stress and Parkin mediated mitophagy. Endoplasmic reticulum stress-induced Parkin-dependent mitophagy may be one of the mechanisms by which electrical stimulation can play a significant role.

目的 观察早期低频电刺激对兔伸直型膝关节挛缩的治疗作用,并探讨其可能的干预机制.方法 将24只新西兰白兔随机分成对照(C)组、单纯电刺激(E)组、自然恢复(NR)组和电刺激治疗(EST)组,每组6只.C组自由活动7周;E组先自由活动4周,随后对左后肢股四头肌给予3周的低频电刺激;NR组先将左膝关节伸直固定4周,随后解除固定自然恢复3周;EST组先将左膝关节伸直固定4周,随后对左后肢股四头肌给予3周的低频电刺激.每组干预结束后,分别测量兔左膝关节剔除肌肉前后的活动范围(ROM),对股直肌进行HE和Masson染色,Western blot检测股直肌和关节囊中转化生长因子-β1(TGF-β1)和α-平滑肌肌动蛋白(α-SMA)的蛋白表达量.结果 与NR组相比,EST组膝关节的总挛缩和肌源性挛缩减轻(P＜0.01),关节源性挛缩未见改善;股直肌HE染色显示EST组肌纤维的形状和肌膜完整性较NR组改善,Masson染色的定量分析显示EST组股直肌纤维化的改善程度高于NR组(P＜0.01).此外,EST组股直肌中TGF-β1和α-SMA的表达量较NR组减低(P＜0.05),EST组关节囊中TGF-β1和o-SMA的蛋白表达量较NR组关节囊相比差异无统计学意义.结论 早期低频电刺激可通过降低骨骼肌纤维化水平来改善兔膝关节伸直型挛缩;且对骨骼肌纤维化的抑制作用大于对关节囊纤维化的抑制作用.

目的 通过研究超短波干预对兔伸直型膝关节挛缩的关节功能、关节囊形态以及关节囊转化生长因子β1(TGF-β1)和结缔组织生长因子(CTGF)表达的影响,对膝关节挛缩过程中出现的关节囊纤维化改变,以及超短波疗法的作用机制进行初步探讨.方法 将新西兰兔随机分为4组并采取不同的干预手段处理:未予以任何处理的空白对照组(0组),固定8周后立即处死的单纯固定组(P组),固定8周后拆除石膏自由活动4周的自然恢复组(N组),固定8周后拆除石膏进行4周超短波治疗的超短波治疗组(M组).兔处死后立即使用关节活动度测量仪记录肌切开术后膝关节活动度.取材后方关节囊,采用Masson染色检测各组膝关节后方关节囊胶原表达程度,半定量RT-PCR法检测关节囊中TGF-β1、CTGF的mRNA表达量;Western blot法检测膝关节后方关节囊中TGF-β1和CTGF的蛋白表达量.结果 与0组相比,P组的肌切开术后膝关节活动度减少(P＜0.05),膝关节后方关节囊胶原百分比、TGF-β1与CTGF的蛋白与mRNA表达水平增高(P＜0.05);与P组相比,N组的肌切开术后膝关节活动度和CTGF的蛋白表达水平差异无统计学意义,CTGF mRNA表达水平升高(P＜0.05),膝关节后方关节囊胶原百分比、TGF-β1的蛋白和mRNA表达水平下降(P＜0.05);与P组相比,M组的肌切开术后膝关节活动度出现上升(P＜0.05),膝关节后方关节囊胶原百分比、TGF-β1与CTGF的蛋白、mRNA表达水平降低(P＜0.05);与N组相比,M组的肌切开术后膝关节活动度表现增大(P＜0.05),膝关节后方关节囊胶原百分比、TGF-β1与CTGF的蛋白、mRNA表达水平变低(P＜0.05).结论 超短波可能通过降低关节囊TGF-β1和CTGF表达,减轻膝关节后方关节囊纤维化,进而有效改善伸直型膝关节挛缩进展.

目的 探讨在兔伸直型膝关节挛缩模型中肌源性挛缩的病理特征及其可能机制.方法 选取新西兰白兔30只,根据固定时间,随机分为以下5组(n = 6):对照组(I-0,不进行任何处理)、固定1周组(I-1,左膝关节伸直位固定1周)、固定2周组(I-2,左膝关节伸直位固定2周)、固定4周组(I-4,左膝关节伸直位固定4周)和固定8周组(I-8,左膝关节伸直位固定8周).然后通过检测固定后膝关节挛缩角度、股直肌Masson染色、低氧诱导因子(HIF)-1α和转化生长因子(TGF)-β1的蛋白表达水平,分析各组结果差异.结果 在固定8周内,固定组的肌源性挛缩角度在4周内随着固定时间的延长而增加,但4周后I-4组和I-8组相比差异无统计学意义.Masson染色结果提示,股直肌横截面积在固定4周内不断降低,而胶原纤维沉积占比在固定4周内不断升高,但固定4周后I-8组与I-4组相比,股直肌横截面积的降低和胶原纤维沉积占比的增加差异均无统计学意义.股直肌HIF-1α蛋白表达水平在固定4周内不断升高,但4周后I-4组和I-8组相比差异无统计学意义;2周内TGF-β1蛋白表达增加差异有统计学意义,2周后每个固定组相比差异无统计学意义.结论 在兔伸直型膝关节挛缩模型中肌源性挛缩的病理特征主要为肌纤维化和萎缩的时间依赖性改变,并且其机制可能与HIF-1α和TGF-β1高表达有关.

The purpose of this study was to determine the preventive effect of ultrashort wave diathermy on immobilization-induced myogenic contracture and to explore its underlying mechanisms. Forty-two rabbits were randomly assigned into control (Group C), immobilization (Group I, which was further divided into one week, Group I-1; two weeks, Group I-2; and four weeks, Group I-4, subgroups by the length of immobilization) and ultrashort wave prevention (Group U, which was further divided into one week, Group U-1; two weeks, Group U-2; and four weeks, Group U-4, by time of treatment) groups. Intervention effects were assessed by evaluating rectus femoris cross-sectional area (CSA), knee range of motion, and the protein levels for myogenic differentiation (MyoD) and muscle atrophy F-box (MAFbx-1) in the rectus femoris. Compared with those of Group C, in Groups I and U, total contracture, myogenic contracture, MyoD and MAFbx-1 levels were significantly elevated, and CSA was significantly smaller (p < 0.05). Compared with those of Group I at each time point, MyoD levels were significantly elevated, MAFbx-1 levels were significantly lower, CSA was significantly larger, and myogenic contracture was significantly alleviated in Group U (p < 0.05). In the early stages of contracture, ultrashort wave diathermy reduces muscle atrophy and delays the process of myogenic contracture during joint immobilization; the mechanism of this may be explained as increased expression of MyoD triggered by suppression of the MAFbx-1-mediated ubiquitin-proteasome pathway.

Cadmium (Cd), a noxious heavy metal, is widespread in the living environment. Gestational exposure to Cd at environmental dose has been shown to cause fetal growth restriction (FGR). However, the long-term effects and the mechanisms underlying environmental Cd exposure on glucose metabolism in offspring remain unclear. Here, we established a murine model to study the impacts of gestational exposure to environmental Cd on glucose metabolism at different life stages of offspring. Results demonstrated that the offspring mice developed hyperglycemia in puberty and impaired glucose tolerance in adulthood following maternal Cd exposure during gestation. Further mechanistic investigation showed that Cd exposure upregulated the expression of key proteins in hepatic gluconeogenesis, including p-CREB, PGC-1α and G6PC, in pubertal and adult offspring. In addition, we demonstrated that Cd exposure during pregnancy markedly elevated the level of oxidative stress-related proteins, including NOX2, NOX4 and HO-1, in the fetal liver. The effects of gestational exposure to N-acetylcysteine (NAC), a free-radical scavenging antioxidant, presented that NAC supplementation alleviated hepatic oxidative stress in fetuses, and thereby reversed hyperglycemia and glucose intolerance in mouse offspring. Collectively, our data suggested that gestational exposure to environmental Cd caused diabetes-like phenotypes via enhancing hepatic gluconeogenesis, which is associated with oxidative stress in fetal livers. This work provides new insights into the protective effects of antioxidants on fetal-originated diabetes triggered by environmental toxicants.

OBJECTIVE:The purpose of this study was to examine the intervention effect of radial extracorporeal shock wave combined with ultrashort wave diathermy on immobilization-induced fibrosis and contracture of muscle.DESIGN:The groups included male rabbits for the group (control group). To cause joint contracture, rabbits underwent plaster fixation of a left knee joint at full extension. After immobilization for 4 wks, all rabbits were randomly divided into five groups: model group, natural recovery group, radial extracorporeal shock wave treatment group, ultrashort wave diathermy group, and radial extracorporeal shock wave combined with ultrashort wave diathermy group. All intervention effects were assessed by evaluating the cross-sectional area and the collagen deposition of muscle, the knee joint range of motion and the protein levels for transforming growth factor β1 and hypoxia-inducible factor 1α.RESULTS:The combined treatment group got the best recovery of the knee joint function. The combined treatment was more effective than radial extracorporeal shock wave or ultrashort wave diathermy alone against the fibrosis and contracture of muscle, as well as the overexpression of transforming growth factor β1 and hypoxia-inducible factor 1α.CONCLUSIONS:Radial extracorporeal shock wave combined with ultrashort wave diathermy was effective in alleviating immobilization-induced contracture and fibrosis of muscle, as well as reducing the molecular manifestations of muscle fibrosis.