NLRP3炎症小体在ICU获得性衰弱大鼠呼吸肌和下肢肌中的表达

目的探讨重症监护室获得性衰弱(ICU-AW)大鼠吸肌和下肢肌组织中NOD样受体热蛋白结构域相关蛋白3(NLRP3)炎症小体的表达及作用。 方法将40只健康雄性SD大鼠完全随机分为对照组(sham组)和实验组(脓毒血症组),采用盲肠结扎穿孔术在实验组大鼠中构建ICU-AW模型,对照组仅行开腹暴露盲肠手术;造模96 h后收集大鼠腓肠肌和膈肌标本,采用HE染色观察病理学变化并计算肌纤维横截面积,采用qRT-PCR和western blot的方法检测大鼠腓肠肌和膈肌中Atrogin-1、MuRF1、NLRP3、Caspase-1、IL-1β和IL-18的表达。 结果盲肠结扎穿孔术96 h后,大鼠腓肠肌和膈肌纤维排列较对照组疏松,肌纤维横截面积较对照组明显减少(P<0.05),Atrogin-1、MuRF1基因和蛋白表达量较对照组明显升高(P<0.05);ICU-AW大鼠腓肠肌和膈肌中NLRP3、Caspase-1、IL-1β和IL-18基因和蛋白表达量较对照组明显升高(P<0.05)。 结论盲肠结扎穿孔术制备的脓毒血症模型中,吸肌和下肢肌溶解参与ICU-AW的发生,NLRP3炎症小体相关信号通路参与上述过程。     

肌肉特异性糖皮质激素受体基因敲除对慢性肾脏病骨骼肌消耗的影响

目的:内源性糖皮质激素水平异常升高可引起和加重慢性肾脏病(CKD)引起的骨骼肌消耗。本研究观察肌肉特异性糖皮质激素受体基因敲除(MGRKO)对CKD状态下小鼠骨骼肌消耗的影响。方法:采用5/6肾切除制作CKD小鼠模型,以假手术组(CTL组)为对照组。组织病理学检测胫骨前肌横截面积并计算肌纤维面积分布图;荧光定量PCR检测肌肉萎缩蛋白Fbox-1(Atrogin-1)和肌环指蛋白1(MuRF-1)mRNA水平;Western Blot检测其蛋白表达及Akt/FoxO1信号通路;ELISA方法检测血清皮质酮水平。结果:造模1月后,lox/lox-CKD和MGRKO-CKD小鼠的血尿素氮和皮质酮水平均明显升高;lox/lox-CKD的体重明显下降胫骨前肌湿重明显降低。而MGRKO-CTL和MGRKO-CKD两组间体重无明显差异,胫骨前肌湿重仅轻微降低。组织学观察到lox/lox-CKD胫骨前肌肌纤维明显萎缩,横截面积减少,肌纤维面积分布图明显左移。而MGRKO-CKD组的体重下降不明显,胫骨前肌仍较饱满,肌肉湿重略降低,横截面积略降低,与MGRKO-CTL组比较,肌纤维面积分布图仅轻度左移。荧光定量PCR和Western Blot结果显示lox/lox-CKD组的腓肠肌Atrogin-1和MuRF-1的mRNA和蛋白表达水平显著升高,同时其Akt磷酸化水平(pAkt/Akt)较lox/lox-CTL组显著降低3.1倍,FoxO1磷酸化水平(pFoxO1/FoxO1)较lox/lox-CTL组降低2.3倍;而MGRKO-CKD组的Atrogin-1表达仅轻微上调,MuRF-1则无明显变化;MGRKO-CKD组Atrogin-1蛋白表达水平仅比MGRKO-CTL组升高,同时pAkt/Akt、pFoxO1/FoxO1水平较对照组仅轻微降低。结论:内源性糖皮质激素水平升高在CKD肌肉消耗中发挥重要作用;MGRKO可减轻/阻止CKD状态下的体重下降和肌肉萎缩,下调肌萎缩关键基因Atrogin-1和MuRF-1表达水平;该效应与阻断糖皮质激素影响Akt/FoxO1信号途径有关,抑制糖皮质激素信号通路可能改善CKD肌肉消耗。     

AKT/FOXO1信号通路在心力衰竭小鼠骨骼肌萎缩中的作用

目的:探讨AKT/FOXO1信号通路在心力衰竭(HF)小鼠骨骼肌萎缩中的作用。方法:采用主动脉弓横向结扎8周,复制小鼠HF动物模型。采用实时定量-聚合酶链式反应和Western blot技术检测HF小鼠胫骨前肌内,E3连接酶的2个肌肉萎缩特异性指标Atrogin-1和MuRF1,对胫骨前肌中转录因子FOXO1和激酶AKT的磷酸化水平和总蛋白水平进行测定,并比较磷酸化蛋白和总蛋白的比率。结果:与对照组小鼠相比,TAC 8周诱导HF小鼠的胫骨前肌肌纤维变小,质量减轻。RT-PCR分析结果显示,HF小鼠胫骨前肌内的Atrogin-1和MuRF1的mRNA表达明显上调(P0.01)。Western blot分析结果显示,HF小鼠胫骨前肌组织中Atrogin-1和MuRF1的蛋白相对表达量HF组较对照组明显增加(P0.01)。HF组小鼠胫骨前肌中p-FOXO1的表达水平较对照组增加,FOXO1的总蛋白水平显著下降;p-AKT的蛋白表达较对照组增加(P0.05),AKT的总蛋白水平差异无统计学意义。p-FOXO1/FOXO1和p-AKT/AKT比率HF组明显高于对照组(P0.01)。结论:AKT/FOXOs信号通路参与HF后骨骼肌萎缩的过程并发挥重要作用。     

肌卫星细胞功能异常在慢性肾脏病骨骼肌消耗中的机制

目的:骨骼肌消耗是慢性肾脏病(CKD)的主要特征,肌卫星细胞(muscle satellite cells,MSC)是具有自我增殖和更新能力的成肌干细胞,MSC功能异常可引起肌肉萎缩.本研究探讨MSC在CKD小鼠骨骼肌消耗中的作用机制. 方法:采用5/6肾切除制作小鼠CKD模型,以假手术组为对照组.以免疫组化标记胫骨前肌层粘连蛋白(laminin),测量肌纤维横截面积,并计算面积百分位图;RT-PCR检测腓肠肌Pax-7、MyoD、Myf-5、Myogenin及myostatin mRNA表达水平;分离并原代培养骨骼肌MSC,原位免疫组化检测Pax-7和MyoD表达,检测分化后新形成的肌纤维胚胎型肌球货白重链(eMyHC). 结果:造模一个月后,CKD小鼠体重和骨骼肌重量明显下降,形态学表现为胫骨前肌明显变细,肌纤维横截面积减少,面积百分位图明显左移;肌肉组织的Pax-7、MyoD、Myf-5和Myogenin mRNA表达水平均有不同程度下降,myostatin mRNA表达则明显上调;原代培养的MSC中,CKD组的Pax-7和MyoD阳性细胞数目明显低于对照组,分化后新形成的eMyHC阳性肌纤维数目也明显降低. 结论:CKD可引起显著的骨骼肌萎缩,使MSC增殖和分化功能下降,myostatin水平升高可能是抑制肌卫星细胞功能的重要原因.     

极低碳水化合物饮食对肥胖症患者心血管危险因素的影响

 目的 观察极低碳水化合物饮食(VLCD)治疗对单纯性肥胖患者心血管危险因素的影响。 方法 观察35例肥胖患者经VLCD治疗8周后,体重、腰围及血压改善的同时,空腹血糖(FPG)、空腹胰岛素(FIns)、血脂谱、尿微量白蛋白/肌酐(UACR)、C反应蛋白(CRP)、TNFα、脂联素(adiponectin)等心血管危险因素的改变。另采集35例健康志愿者作为基线对照组。 结果 基线时肥胖组较正常对照组有更显著的心血管危险因素(P值均<0.05)。试验结束时肥胖患者的体重与腰围分别减少了(8.5±0.7)kg与(6.6±1.1)cm(P值均<0.01);收缩压、舒张压、FIns、TC、TG等指标均较前显著降低(P值均<0.05);FPG、LDL-C及HDL-C等的改变无统计学意义;UACR、CRP、TNFα分别减少了(1.86±0.86)μg/mg、(1.15±0.45)mg/L及(0.94±0.21)ng/L(P值均<0.05);脂联素水平增加了(2.12±0.59)mg/L(P<0.01)。结论 8周的VLCD治疗肥胖症可有效减重并显著改善多种心血管危险因素。     

北京部分社区2型糖尿病患者降糖用药情况分析

 目的 通过调查北京市部分社区2型糖尿病患者降糖用药情况,了解不同版本《国家基本药物目录》中降糖药物(简称国家基本降糖药物)的覆盖情况。方法 纳入北京市4个社区卫生服务中心的2型糖尿病患者900例,以糖化血红蛋白(HbA1c)<7%为目标控制血糖,随访1年后比较不同版本国家基本降糖药物使用覆盖率的变化。结果 (1)基线时:应用2012年版国家基本降糖药物的比例(91.4%)明显高于应用2009年版目录药物的比例(42.9%)(χ²=481.09,P<0.05)。7种国家基本降糖药物中,阿卡波糖(48.9%)、二甲双胍(40.7%)和重组人胰岛素(31.1%)的覆盖率较高(χ²=1519.65,P<0.05)。(2)1年后随访:总人群HbA1c达标率(53.6%)较基线时(32.3%)提高(χ²=77.26,P<0.05)。应用2012年版国家基本降糖药物的比例(85.5%)仍明显高于应用2009年版目录药物的比例(37.4%)(χ²=376.367,P<0.05)。阿卡波糖(49.7%)、二甲双胍(36.3%)和重组人胰岛素(30.4%)的覆盖率仍较高(χ²=1320.70,P<0.05)。结论 2012年版的国家基本降糖药物较2009年版可更好地满足北京社区2型糖尿病患者的需求。
        

小檗碱对糖尿病db/db小鼠骨骼肌蛋白质代谢的影响及机制研究

目的 探讨小檗碱对糖尿病/胰岛素抵抗模型db/db小鼠骨骼肌蛋白质代谢及肌萎缩蛋白Fbox-1(Atrogin-1)表达的影响.方法 db/db小鼠为研究对象,以野生型为对照组.予小檗碱(5 mg·kg-1·d-1)腹腔注射3周,观察体重和食量;3周末处死,分离胫骨前肌和腓肠肌.胫骨前肌冰冻切片行层黏连蛋白免疫组化染色,荧光显微镜下观察并拍照,测量肌纤维横截面积并计算肌纤维面积分布图;同位素[14C]-苯丙氨酸掺入法检测肌肉蛋白合成,[3H]-酪氨酸释放率分析检测肌肉分解代谢;Northern印迹检测腓肠肌Atrogin-1和肌环指蛋白1(MurF-1)转录水平,Western印迹检测蛋白翻译水平.结果 小檗碱能明显降低db/db小鼠血糖水平[(18.55---3.79对26.32±4.02)mmol/L,P＜0.01],降低脂肪重量[(2.75±0.30对3.77±0.52)g,P＜0.05],使胫骨前肌的肌重/胫骨长度比值及肌纤维横截面积下降,肌纤维面积分布图明显左移;小檗碱使野生型j、鼠和db/db小鼠的蛋白质合成率下降18％ ～ 22％;蛋白质分解率升高24％～ 26％,使肌肉特异性的Atrogin-1、MurF-1转录和翻译水平增高,同时使真核转录因子3调节亚基(eIF3-f)蛋白水平降低.结论 小檗碱具有降糖降脂作用,但可引起骨骼肌蛋白质合成下降,促进蛋白质分解代谢,加剧糖尿病的骨骼肌消耗,其机制与上调Atrogin-1和MurF-1表达,同时下调elF3-f有关.     

Clinicopathological features of nonpolypoid colorectal tumors as viewed from the patients' background

Background This study was performed to characterize the clinicopathological features of colorectal tumors with flat-, depressed-, or protruded-type morphology (hereafter referred to simply as flat, depressed, or protruded lesions). Methods There are two major types of colorectal tumor: polypoid (protruded) and nonpolypoid (flat and depressed). A total of 130 lesions from 130 patients with colorectal submucosal invasive cancer were classified into three groups according to their macromorphology seen during endoscopy: flat (laterally spreading) and depressed nonpolypoid tumors and protruded polypoid tumors. The following factors in the patients' background were evaluated: indication for colonoscopy, age, and family history of colorectal cancer in first-degree relatives (i.e., parents, siblings, children). We also compared the following characteristics of the tumors: size, location, depth of submucosal invasion, vascular invasion, and frequency of synchronous and metachronous tumor lesions. Results The incidence of abnormal findings on follow-up studies after polypectomy as an indication for colonoscopy was significantly higher among patients with flat lesions (4/24, 16.7%) and depressed lesions (3/22, 13.6%) than among those with protruded lesions (1/84, 1.2%) (P < 0.01, P < 0.01). Patients with flat lesions (65.8 ± 7.6 years old) were significantly older than those with protruded lesions (P < 0.05). The patients with flat tumors had a significantly higher rate of a family history of colorectal cancer (6/24, 25.0%) than patients with protruded or depressed lesions (P < 0.01, P < 0.05). The protruded lesions were significantly larger than the depressed lesions (size 13.3 ± 6.7 mm) (P < 0.05), and the flat lesions (24.1 ± 10.1 mm) were significantly larger than either the protruded or depressed lesions (P < 0.01, P < 0.01). Seventy-five percent (18/24) of the flat lesions were located in the right colon, and this proportion was significantly higher than that among the protruded or depressed lesions (P < 0.01, P < 0.01). The mean ± SD depth of submucosal invasion was 1218 ± 1034 μm in the flat lesions, 2392 ± 1869 μm in the depressed lesions, and 2761 ± 1929 μm in the protruded lesions, representing a significant difference (P < 0.05, P < 0.0001). Of the 24 patients with flat lesions, 9 (37.5%) showed vascular invasion; this proportion was significantly lower than that among patients with the depressed or protruded lesions (P < 0.01, P < 0.01). Patients with depressed lesions tended to have higher incidence of synchronous and metachronous malignant polyps than those with protruded or flat lesions. Conclusion It is important to examine the morphology of colorectal tumors when diagnosing them and planning the treatment strategy, including follow-up, after resection of nonpolypoid tumors. It is useful to know the patient's family history so nonpolypoid tumors can be accurately diagnosed.     

尿石素B对地塞米松诱导小鼠肌萎缩的改善作用及机制

目的探讨尿石素B对地塞米松诱导的小鼠肌萎缩的改善作用及机制。方法将32只昆明鼠随机分为:正常组,正常给药组,模型组,模型给药组。每周1次采集相关数据,包括小鼠体成分、抓力;用HE染色法对小鼠腓肠肌肌纤维的石蜡切片进行染色,并计算横截面面积;用RT-PCR分析与肌蛋白密切相关的泛素蛋白酶通路中的基因Myogenin、MyoD、MuRF-1及Atrogin-1mRNA表达水平的变化。结果与正常组比较,正常给药组小鼠体重、瘦体重、抓力及肌纤维横截面积稍下降,但差异无统计学意义(P0.05),模型组体重、瘦体重含量、抓力及肌纤维横截面面积均显著降低,差异有统计学意义(P0.05),而模型给药组各指标均较模型组有所提升,但差异无统计学意义(P0.05),但仍明显低于正常组,差异有统计学意义(P0.05);模型组Myogenin、MyoD mRNA表达水平分别是正常组的0.24、0.35倍,模型给药组则是正常组的0.87、0.60倍,各组间差异有统计学意义(P0.05);MuRF-1、Atrogin mRNA表达水平在模型组与模型给药组较正常组均显著升高,差异有统计学意义(P0.05),模型组表达水平是正常组的17.66、11.01倍,模型给药组分别是4.23、4.05倍,较模型组有所下降,但仍高于正常组,差异有统计学意义(P0.05)。结论尿石素B能够有效改善地塞米松诱导的肌萎缩,对肌少症有潜在的治疗意义。     

Mizoribine therapy for patients with lupus nephritis: the association between peak mizoribine concentration and clinical efficacy

The clinical efficacy of mizoribine (MZR; 4-carbamoyl-1-b-d-ribofuranosylimidazolium) in patients with lupus nephritis was investigated. Thirteen Japanese patients with biopsy-proved lupus nephritis were enrolled in this study. A change in global assessments score, total protein (TP) of serum, serum creatinine, creatinine clearance (Ccr), proteinuria, titers of serum anti-ds DNA antibody, C3, C4, and hemolytic complement activity (CH50) were examined. Following MZR treatment, the level of urinary protein decreased (P < 0.05), whereas the level of Ccr increased (P < 0.05). Moreover, the level of TP significantly increased from 5.5 g/dl to 6.3 g/dl (P < 0.01) and the level of C3 increased significantly (P < 0.01). However, there was no change in the levels of both C4 and CH50. The titer of anti-ds DNA antibody significantly decreased (P < 0.05). The dosage of prednisolone could be tapered from 24.8 mg to 14.9 mg daily during the period. The clinical effects associated with MZR concentration in the blood revealed that there was a significant correlation between the peak MZR blood concentration of more than 0.66 μg/ml and clinical improvement (P = 0.021). Our results suggest that an optimal MZR blood concentration was important for the treatment of lupus nephritis. The first two authors contributed equally to this work.     

Muscle-specific RING finger 1 is a bona fide ubiquitin ligase that degrades cardiac troponin I

Muscle-specific RING finger protein 1 (MuRF1) is a sarcomere-associated protein that is restricted to cardiac and skeletal muscle. In skeletal muscle, MuRF1 is up-regulated by conditions that provoke atrophy, but its function in the heart is not known. The presence of a RING finger in MuRF1 raises the possibility that it is a component of the ubiquitin-proteasome system of protein degradation. We performed a yeast two-hybrid screen to search for interaction partners of MuRF1 in the heart that might be targets of its putative ubiquitin ligase activity. This screen identified troponin I as a MuRF1 partner protein. MuRF1 and troponin I were found to associate both in vitro and in vivo in cultured cardiomyocytes. MuRF1 reduced steady-state troponin I levels when coexpressed in COS-7 cells and increased degradation of endogenous troponin I protein in cardiomyocytes. The degradation of troponin I in cardiomyocytes was associated with the accumulation of ubiquitylated intermediates of troponin I and was proteasome-dependent. In vitro, MuRF1 functioned as a ubiquitin ligase to catalyze ubiquitylation of troponin I through a RING finger-dependent mechanism. In isolated cardiomyocytes, MuRF1 reduced indices of contractility. In cardiomyocytes, these processes may determine the balance between hypertrophic and antihypertrophic signals and the regulation of myocyte contractile responses in the setting of heart failure.     

Suppression of atrogin-1 and MuRF1 prevents dexamethasone-induced atrophy of cultured myotubes

Objective

The mechanistic role of the ubiquitin ligases atrogin-1 and MuRF1 in glucocorticoid-induced muscle wasting is not fully understood. Here, we tested the hypothesis that glucocorticoid-induced muscle atrophy is at least in part linked to atrogin-1 and MuRF1 expression and that the ubiquitin ligases are regulated by compensatory mechanisms.

Methods

The expression of atrogin-1 and MuRF1 was suppressed individually or in combination in cultured L6 myotubes by using siRNA technique. Myotubes were treated with dexamethasone followed by determination of mRNA and protein levels for atrogin-1 and MuRF1, protein synthesis and degradation rates, and myotube morphology.

Results

Suppression of atrogin-1 resulted in increased expression of MuRF1 and vice versa, suggesting that the ubiquitin ligases are regulated by compensatory mechanisms. Simultaneous suppression of atrogin-1 and MuRF1 resulted in myotube hypertrophy, mainly reflecting stimulated protein synthesis, and prevented dexamethasone-induced myotube atrophy, mainly reflecting inhibited protein degradation.

Conclusions

The results provide evidence for a link between upregulated atrogin-1 and MuRF1 expression and glucocorticoid-induced muscle atrophy. The study also suggests that atrogin-1 and MuRF1 levels are regulated by compensatory mechanisms and that inhibition of both ubiquitin ligases may be needed to prevent glucocorticoid-induced muscle proteolysis and atrophy.     

Absence of insulin signalling in skeletal muscle is associated with reduced muscle mass and function: evidence for decreased protein synthesis and not increased degradation

Loss of skeletal muscle mass and function is observed in many insulin-resistant disease states such as diabetes, cancer cachexia, renal failure and ageing although the mechanisms for this remain unclear. We hypothesised that impaired insulin signalling results in reduced muscle mass and function and that this decrease in muscle mass and function is due to both increased production of atrogenes and aberrant reactive oxygen species (ROS) generation. Maximum tetanic force of the extensor digitorum longus of muscle insulin receptor knockout (MIRKO) and lox/lox control mice was measured in situ. Muscles were removed for the measurement of mass, histological examination and ROS production. Activation of insulin signalling pathways, markers of muscle atrophy and indices of protein synthesis were determined in a separate group of MIRKO and lox/lox mice 15 min following treatment with insulin. Muscles from MIRKO mice had 36% lower maximum tetanic force generation compared with muscles of lox/lox mice. Muscle fibres of MIRKO mice were significantly smaller than those of lox/lox mice with no apparent structural abnormalities. Muscles from MIRKO mice demonstrated absent phosphorylation of AKT in response to exogenous insulin along with a failure to phosphorylate ribosomal S6 compared with lox/lox mice. Atrogin-1 and MuRF1 relative mRNA expression in muscles from MIRKO mice were decreased compared with muscles from lox/lox mice following insulin treatment. There were no differences in markers of reactive oxygen species damage between muscles from MIRKO mice and lox/lox mice. These data support the hypothesis that the absence of insulin signalling contributes to reduced muscle mass and function though decreased protein synthesis rather than proteasomal atrophic pathways.     

尿pH值与慢性肾脏疾病患者对比剂肾病的关系

目的 探讨尿pH值与慢性肾脏疾病（chronic kidney disease,CKD）患者经皮冠状动脉介入（percutaneous coronary intervention,PCI）治疗或冠状动脉造影术（coronary angiography,CAG）后对比剂肾病（contrast-induced nephropathy,CIN）的相关性.方法 回顾性分析2009年9月至2012年8月在广东省人民医院行择期PCI治疗或CAG的CKD患者453例的临床资料.按术前尿pH值水平将患者分为2组：尿pH值≥6组（n=254例）,尿pH值＜6组（n=199例）.比较两组之间的基线资料、CIN发病率、院内病死率及血液透析率.采用单因素Logistic 回归分析筛选CIN的危险因素,采用多因素Logistic回归分析尿pH值＜6与CIN的关系.结果 共52例患者（11.5％）发生CIN;尿pH值≥6组,尿pH值＜6组CIN的发病率分别5.5％ （14/254）、19.1％（38/199）,两组比较差异有统计学意义（P＜0.001）;院内病死率分别为0和1.5％ （3/199）,两组比较差异无统计学意义（P=0.050）;血液透析率分别为0.4％（1/254）和1.5％（3/199）,两组比较差异无统计学意义（P=0.209）.单因素Logistic回归分析显示,尿pH值＜6与CIN的发病率相关（OR =4.406,95％CI：2.124-7.708,P＜0.001）;多因素Logistic回归分析提示,尿pH值＜6是CIN的独立危险因素（OR =3.267,95％CI：1.674-6.374,P=0.001）.结论 CKD患者术前尿pH值＜6与择期PCI或CAG术后CIN相关,尿pH值＜6增加发生CIN的风险.     

不同频率神经肌肉电刺激对ARDS相关性ICU-AW小鼠肌肉萎缩防治及临床意义

目的 不同频率下神经肌肉电刺激(neuromuscular electrical stimulation,NMES)在ARDS相关性ICU获得性衰弱(ICU-acquired weakness,ICU-AW)中的作用及机制。方法 健康雄性C57BL/6小鼠88只随机分为11组,每组8只。分为:空白对照组(C1)、气管内注入无菌水组(C2)、ICU-AW模型组(ICU-AW)、ICU-AW+AMPK激动剂A-769662组(ICU-AW-A)、ICU-AW+A-769662溶剂对照组(ICU-AWV)、NMES 20 Hz组(ICU-AW-20)、NMES 40 Hz组(ICU-AW-40)、NMES 60 Hz组(ICU-AW-60)、NMES80 Hz组(ICU-AW-80)、ICU-AW-40+AMPK抑制剂Compound C组(ICU-AW-40-C)、ICU-AW-40+Compound C溶剂对照组(ICU-AW-40-V)。检测小鼠四肢抓力和存活状态,7 d后收集小鼠肺组织和腓肠肌标本,采用HE染色观察肺和肌肉病理学变化,采用western blot以及qRT-PCR的方...     

Regulation of nicotinic acetylcholine receptor turnover by MuRF1 connects muscle activity to endo/lysosomal and atrophy pathways

Muscle atrophy is a process of muscle wasting induced under a series of catabolic stress conditions, such as denervation, disuse, cancer cachexia, heart and renal failure, AIDS, and aging. Neuromuscular junctions (NMJs), the synapses between motor neurons and muscle fibers undergo major changes in atrophying muscles, ranging from mild morphological alterations to complete disintegration. In this study, we hypothesized that remodeling of NMJs and muscle atrophy could be linked together. To test this, we examined if a major atrophy-promoting E3 ubiquitin ligase, MuRF1, is involved in the maintenance of NMJs. Immunofluorescence revealed that MuRF1 is highly enriched close to the NMJ. Affinity precipitation and in vivo imaging showed that MuRF1 interacts in endocytic structures with both, acetylcholine receptor, the primary postsynaptic protein of the NMJ, as well as with Bif-1, an autophagy- and endocytosis-regulating factor. In vivo imaging, radio labeling, and weighing approaches demonstrated that metabolic destabilization of acetylcholine receptors and muscle atrophy induced by denervation were significantly rescued in MuRF1-KO animals. Notably, interaction with Bif-1, and the rescue of AChR lifetime and muscle atrophy were specific to MuRF1 but not MuRF2. Our data demonstrate an involvement of MuRF1 in membrane protein-turnover, including the degradation of AChRs at the NMJ under atrophying conditions where MuRF1 also interacts and associates with Bif-1.