Muscular Proteins Research Articles

Decellularized adipose-derived matrix from Superficial layers of abdominal adipose tissue exhibits superior capacity of adipogenesis compared to deep layers

The adipogenic property of decellularized adipose-derived matrix (DAM) varies widely across reports, making it difficult to make a horizontal comparison between reports and posing challenges for the stable clinical translation of DAM. It is possibly due to differences in donor characteristics, but the exact relationship remains unclear. Despite extensive research on the differences between superficial and deep layers of abdominal subcutaneous fat, a main donor of DAM, little is known about their extracellular matrix (ECM) which is promising in regenerative medicine. In this study, we first confirmed the distinct compositional profiles and adipogenic potential between superficial and deep DAM (S-DAM and D-DAM). Both in vitro and in vivo assays confirmed superior adipogenic induction potential in S-DAM over D-DAM. Total amounts of ECM proteins like collagen and laminin were similar, however, the predominant types differed, with collagen I dominating S-DAM and collagen XIV prevailing in D-DAM. S-DAM was enriched with mitochondrial and immunological proteins, whereas D-DAM featured more neuronal, vascular, muscular, and endocrine-related proteins. More proteins involved in mRNA processing were found in D-DAM, with Protein-Protein Interaction (PPI) analysis revealing HNRNPA2B1, HNRNPA1, and HNRNPC as the most tightly interacting members. These findings not only deepen our comprehension of the structural and functional heterogeneity of adipose tissues but also become one of the reason for the large variability between batches of DAM products, providing guidance for constructing more efficient and stable bio-scaffolds.

Engineered IscB-ωRNA system with expanded target range for base editing.

As the evolutionary ancestor of Cas9 nuclease, IscB proteins serve as compact RNA-guided DNA endonucleases and nickases, making them strong candidates for base editing. Nevertheless, the narrow targeting scope limits the application of IscB systems; thus, it is necessary to find more IscBs that recognize different target-adjacent motifs (TAMs). Here, we identified 10 of 19 uncharacterized IscB proteins from uncultured microbes with activity in mammalian cells. Through protein and ωRNA engineering, we further enhanced the activity of IscB ortholog IscB.m16 and expanded its TAM scope from MRNRAA to NNNGNA, resulting in a variant named IscB.m16*. By fusing the deaminase domains with IscB.m16* nickase, we generated IscB.m16*-derived base editors that exhibited robust base-editing efficiency in mammalian cells and effectively restored Duchenne muscular dystrophy proteins in diseased mice through single adeno-associated virus delivery. Thus, this study establishes a set of compact base-editing tools for basic research and therapeutic applications.

Lactobacillus gasseri BNR17 Ameliorates Dexamethasone-Induced Muscle Loss in BALB/c Mice and C2C12 Myotubes.

This study aimed to investigate the effects and mechanism of Lactobacillus gasseri BNR17, a probiotic strain isolated from human breast milk, on dexamethasone-induced muscle loss in mice and cultured myotubes. BALB/c mice were intraperitoneally injected with dexamethasone, and orally administered L. gasseri BNR17 for 21 days. L. gasseri BNR17 treatment ameliorated dexamethasone-induced decline in muscle function, as evidenced by an increase in forelimb grip strength, treadmill running time, and rotarod retention time in both female and male mice. In addition, L. gasseri BNR17 treatment significantly increased the mass of the gastrocnemius and quadriceps muscles. Dual-energy X-ray absorptiometry showed a significant increase in lean body mass and a decrease in fat mass in both whole body and hind limb after treatment with L. gasseri BNR17. It was found that L. gasseri BNR17 treatment downregulated serum myostatin level and the protein degradation pathway composed of muscle-specific ubiquitin E3 ligases, MuRF1 and MAFbx, and their transcription factor FoxO3. In contrast, L. gasseri BNR17 treatment upregulated serum insulin-like growth factor-1 level and Akt-mTOR-p70S6K signaling pathway involved in protein synthesis in muscle. As a result, L. gasseri BNR17 treatment significantly increased the levels of major muscular proteins such as myosin heavy chain and myoblast determination protein 1. Consistent with in vivo results, L. gasseri BNR17 culture supernatant significantly ameliorated dexamethasone-induced C2C12 myotube atrophy in vitro. In conclusion, L. gasseri BNR17 ameliorates muscle loss by downregulating the protein degradation pathway and upregulating the protein synthesis pathway.

Aging related obesity and type 2 diabetes mellitus suppress neuromuscular communication and aggravate skeletal muscle dysfunction in rhesus monkeys

Age-related functional deterioration in skeletal muscle raises the risk for falls, disability, and mortality in the elderly, particularly in obese people or those with type 2 diabetes mellitus (T2D). However, the response of the skeletal muscle to transitioning from obesity to diabetes remains poorly defined, despite that obesity is classified as a stage of pre-diabetes. We screened and selected spontaneously obese and diabetic rhesus monkeys and examined altered protein expression in skeletal muscle of healthy aging (CON), obesity aging (OB), and type 2 diabetes mellitus aging (T2D) rhesus monkeys using Tandem Mass Tags (TMT)-based quantitative proteomic analysis. In total, we identified 142 differentially expressed proteins. Muscle-nerve communication proteins were firstly suppressed at obese-stage. With the disintegration of skeletal muscle, mitochondrial complex I and other energy homeostasis relate proteins were significantly disordered at T2D stage. Indicating that aging related obesity suppressed muscle-nerve communication and contribute to T2D related functional deterioration of skeletal muscles in elderly rhesus monkeys. Some alterations of muscular functional regulator are detected in both obesity and T2D samples, suggesting some T2D related skeletal muscular hypofunctions are occurring at obesity or pre-obesity stage. Muscle-nerve communication proteins and muscular function related proteins could be potential therapy target or early diagnose marker of for skeletal muscular hypofunctions in aging obesity populations.

Genetic Polymorphisms and Their Impact on Body Composition and Performance of Brazilians in a 105 Km Mountain Ultramarathon.

Although the studied polymorphisms affect muscular proteins, aerobic adaptations, and recovery, their influence on the anthropometric variables and performance in ultramarathon runners is still poorly understood. This study aimed to determine the influence of ACTN3 R577X, ACE I/D, and CK MM A/G NcoI polymorphisms on the changes in the anthropometric variables and running time of 105 km mountain runners, in which 22 male Brazilian elite athletes (35.9 ± 6.5 years) were evaluated. Genotyping of the R577X (RR, RX, and XX), ACE I/D (DD, ID, and II), and CK MM A/G Ncol (AA, AG, and GG) polymorphisms was performed using the Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) technique with DNA extracted from saliva. Body composition was determined via bioimpedance. Pre- and post-race weight differences were observed on athletes with the AA genotype (77.1 ± 5.9 kg; 74.6 ± 5.6 kg) compared with those with the AG genotype (74.5 ± 8.0 kg; 68 ± 5.1 kg) (p = 0.02; p = 0.02). The RR genotype showed a correlation between BMI and running time (R = 0.97; p = 0.004). The genotype II showed a correlation with % fat and fat mass concerning running time (R = 0.91; p = 0.003; R = 0.99; p < 0.0001). The AA genotype was associated with post-race weight and lean mass loss, while the RR genotype correlated with BMI, and the genotype II correlated with % body fat and fat mass in relation to times in the 105 km mountain ultramarathon.

TMT-Based Quantitative Proteomics Analysis Reveals Differentially Expressed Proteins between Different Sources of hMSCs.

Mesenchymal stem cells (MSCs) are an attractive therapeutic tool for tissue engineering and regenerative medicine owing to their regenerative and trophic properties. The best-known and most widely used are bone marrow MSCs, which are currently being harvested and developed from a wide range of adult and perinatal tissues. MSCs from different sources are believed to have different secretion potentials and production, which may influence their therapeutic effects. To confirm this, we performed a quantitative proteomic analysis based on the TMT technique of MSCs from three different sources: Wharton's jelly (WJ), dental pulp (DP), and bone marrow (BM). Our analysis focused on MSC biological properties of interest for tissue engineering. We identified a total of 611 differentially expressed human proteins. WJ-MSCs showed the greatest variation compared with the other sources. WJ produced more extracellular matrix (ECM) proteins and ECM-affiliated proteins and proteins related to the inflammatory and immune response processes. BM-MSCs expressed more proteins involved in osteogenic, adipogenic, neuronal, or muscular differentiation and proteins involved in paracrine communication. Compared to the other sources, DP-MSCs overexpressed proteins involved in the exocytosis process. The results obtained confirm the existence of differences between WJ, DP, and BM-MSCs and the need to select the MSC origin according to the therapeutic objective sought.

MyoD-induced reprogramming of human fibroblasts and urinary stem cells in vitro: protocols and their applications.

The conversion of fibroblasts into myogenic cells is a powerful tool to both develop and test therapeutic strategies and to perform in-depth investigations of neuromuscular disorders, avoiding the need for muscle biopsies. We developed an easy, reproducible, and high-efficiency lentivirus-mediated transdifferentiation protocol, that can be used to convert healthy donor fibroblasts and a promising new cellular model, urinary stem cells (USCs), into myoblasts, that can be further differentiated into multinucleated myotubes in vitro. Transcriptome and proteome profiling of specific muscle markers (desmin, myosin, dystrophin) was performed to characterize both the myoblasts and myotubes derived from each cell type and to test the transdifferentiation-inducing capacity of MYOD1 in fibroblasts and USCs. Specifically, the Duchenne muscular dystrophy (DMD) transcripts and proteins, including both the full-length Dp427 and the short Dp71 isoform, were evaluated. The protocol was firstly developed in healthy donor fibroblasts and USCs and then used to convert DMD patients' fibroblasts, with the aim of testing the efficacy of an antisense drug in vitro. Technical issues, limitations, and problems are explained and discussed. We demonstrate that MyoD-induced-fibroblasts and USCs are a useful in vitro model of myogenic cells to investigate possible therapies for neuromuscular diseases.

The Effect of Resistance Training With Electrical Muscle Stimulation on Atrogin-1 and Muscle Ring Finger-1 in Elite Male Athletes After Anterior Cruciate Ligament Surgery

Background and Aims The cellular mechanisms preventing muscle atrophy after Anterior Cruciate Ligament (ACL) regeneration are not well understood. The aim of the present study was to evaluate the effect of resistance training combined with electrical muscle stimulation on serum levels of atrogin-1 and muscle RING finger-1 (MuRF1) in elite athletes following ACL surgery. Methods Among the elite athletes of Razavi Khorasan Province, 20 athletes voluntarily participated in the study and were divided into two groups (ten cases each), including 1) resistance training- electrical muscle stimulation (RT-EMS), and 2) resistance training (RT). The subjects in both groups performed 2-4 sets of resistance exercises (knee extension machine, squat, and knee flexion machines) at an intensity of 30-70% of ten repetitions for 12 weeks. The subjects in the RT-EMS group performed the exercises in combination with electrical stimulation at 35-70 Hz. Blood samples were collected from all subjects before and 48 hours after the last training session to measure atrogin-1 and MuRF1 levels. Analysis of covariance (ANCOVA) and paired t-test were used to compare between- and within-group changes, respectively, and a P&lt;0.05 was considered significant. Results The results showed that 12 weeks of resistance training- electrical muscle stimulation significantly decreased serum levels of atrogin 1 (P=0.013) and MuRF1 (P=0.008) in the post-test compared to the pre-test. In addition, the between-groups comparison showed a significant difference in atrogin 1 levels between the RT-EMS and RT groups (P=0.047). Conclusion It can be suggested that resistance training in combination with electrical muscle stimulation is associated with lower levels of muscular atrophy proteins, such as atrogin-1 and MuRF1, and therefore, can be more effective than resistance training alone.

Dynamic changes in molecular composition of black soldier fly prepupae and derived biomasses with microbial fermentation.

Black soldier fly (BSF) is being increasingly used for agro-food by-products valorisation. Adult flies, puparia, and excess of prepupae are the by-products of this process, which could be further valorised. Lactic fermentation of BSF biomasses with two different strains (L. rhamnosus and L. plantarum) has been used for this purpose. Deep changes in the molecular composition were observed, without significant differences related to the different strains used. The lipid and protein fractions were the most impacted. Fermentation enriched the biomass in monounsaturated and polyunsaturated fatty acids and essential amino acids, significantly improving the nutritional properties of the substrates. Although not particularly marked, a proteolytic activity of lactobacilli was observed on the BSF muscular and cuticular proteins, especially in the samples of adult flies and puparia, where fermentation resulted more effective. Conversely, there was no evidence of chitinolytic activity.

Decabromodiphenyl Ethane Mainly Affected the Muscle Contraction and Reproductive Endocrine System in Female Adult Zebrafish.

The novel brominated flame retardant decabromodiphenyl ethane (DBDPE) has become a widespread environmental pollutant. However, the target tissue and toxicity of DBDPE are still not clear. In the current study, female zebrafish were exposed to 1 and 100 nM DBDPE for 28 days. Chemical analysis revealed that DBDPE tended to accumulate in the brain other than the liver and gonad. Subsequently, tandem mass tag-based quantitative proteomics and parallel reaction monitoring verification were performed to screen the differentially expressed proteins in the brain. Bioinformatics analysis revealed that DBDPE mainly affected the biological process related to muscle contraction and estrogenic response. Therefore, the neurotoxicity and reproductive disruptions were validated via multilevel toxicological endpoints. Specifically, locomotor behavioral changes proved the potency of neurotoxicity, which may be caused by disturbance of muscular proteins and calcium homeostasis; decreases of sex hormone levels and transcriptional changes of genes related to the hypothalamic-pituitary-gonad-liver axis confirmed reproductive disruptions upon DBDPE exposure. In summary, our results suggested that DBDPE primarily accumulated in the brain and evoked neurotoxicity and reproductive disruptions in female zebrafish. These findings can provide important clues for a further mechanism study and risk assessment of DBDPE.

AchR myasthenia gravis (MG) atypical presentation in human immunodeficiency virus (HIV) positive patient

MG is an autoimmune disease characterized by muscle weakness and fatigability and it is associated with autoantibodies direct to specific muscular proteins like acetylcholine receptor (AchR). The co-occurrence of HIV infection and immune-mediated disorders is known but HIV-MG association is rare.

Out of Control: The Role of the Ubiquitin Proteasome System in Skeletal Muscle during Inflammation.

The majority of critically ill intensive care unit (ICU) patients with severe sepsis develop ICU-acquired weakness (ICUAW) characterized by loss of muscle mass, reduction in myofiber size and decreased muscle strength leading to persisting physical impairment. This phenotype results from a dysregulated protein homeostasis with increased protein degradation and decreased protein synthesis, eventually causing a decrease in muscle structural proteins. The ubiquitin proteasome system (UPS) is the predominant protein-degrading system in muscle that is activated during diverse muscle atrophy conditions, e.g., inflammation. The specificity of UPS-mediated protein degradation is assured by E3 ubiquitin ligases, such as atrogin-1 and MuRF1, which target structural and contractile proteins, proteins involved in energy metabolism and transcription factors for UPS-dependent degradation. Although the regulation of activity and function of E3 ubiquitin ligases in inflammation-induced muscle atrophy is well perceived, the contribution of the proteasome to muscle atrophy during inflammation is still elusive. During inflammation, a shift from standard- to immunoproteasome was described; however, to which extent this contributes to muscle wasting and whether this changes targeting of specific muscular proteins is not well described. This review summarizes the function of the main proinflammatory cytokines and acute phase response proteins and their signaling pathways in inflammation-induced muscle atrophy with a focus on UPS-mediated protein degradation in muscle during sepsis. The regulation and target-specificity of the main E3 ubiquitin ligases in muscle atrophy and their mode of action on myofibrillar proteins will be reported. The function of the standard- and immunoproteasome in inflammation-induced muscle atrophy will be described and the effects of proteasome-inhibitors as treatment strategies will be discussed.

Identification and Quantification of Glutathionylated Cysteines under Ischemic Stress

Ischemia reperfusion injury contributes to adverse cardiovascular diseases in part by producing a burst of reactive oxygen species that induce oxidations of many muscular proteins. Glutathionylation is one of the major protein cysteine oxidations that often serve as molecular mechanisms behind the pathophysiology associated with ischemic stress. Despite the biological significance of glutathionylation in ischemia reperfusion, identification of specific glutathionylated cysteines under ischemic stress has been limited. In this report, we have analyzed glutathionylation under oxygen-glucose deprivation (OGD) or repletion of nutrients after OGD (OGD/R) by using a clickable glutathione approach that specifically detects glutathionylated proteins. Our data find that palmitate availability induces a global level of glutathionylation and decreases cell viability during OGD/R. We have then applied a clickable glutathione-based proteomic quantification strategy, which enabled the identification and quantification of 249 glutathionylated cysteines in response to palmitate during OGD/R in the HL-1 cardiomyocyte cell line. The subsequent bioinformatic analysis found 18 glutathionylated cysteines whose genetic variants are associated with muscular disorders. Overall, our data report glutathionylated cysteines under ischemic stress that may contribute to adverse outcomes or muscular disorders.

Role of Immunoglobulins in Muscular Dystrophies and Inflammatory Myopathies.

Muscular dystrophies and inflammatory myopathies are heterogeneous muscular disorders characterized by progressive muscle weakness and mass loss. Despite the high variability of etiology, inflammation and involvement of both innate and adaptive immune response are shared features. The best understood immune mechanisms involved in these pathologies include complement cascade activation, auto-antibodies directed against muscular proteins or de-novo expressed antigens in myofibers, MHC-I overexpression in myofibers, and lymphocytes-mediated cytotoxicity. Intravenous immunoglobulins (IVIGs) administration could represent a suitable immunomodulator with this respect. Here we focus on mechanisms of action of immunoglobulins in muscular dystrophies and inflammatory myopathies highlighting results of IVIGs from pre-clinical and case reports evidences.

Albumin Infusion in Critically Ill COVID-19 Patients: Hemodilution and Anticoagulation.

Hypercoagulation is one of the major risk factors for ICU treatment, mechanical ventilation, and death in critically ill patients infected with SARS-CoV-2. At the same time, hypoalbuminemia is one risk factor in such patients, independent of age and comorbidities. Especially in patients with severe SARS-CoV-2-infection, albumin infusion may be essential to improve hemodynamics and to reduce the plasma level of the main marker of thromboembolism, namely, the D-dimer plasma level, as suggested by a recent report. Albumin is responsible for 80% of the oncotic pressure in the vessels. This is necessary to keep enough water within the systemic circulatory system and for the maintenance of sufficient blood pressure, as well as for sufficient blood supply for vital organs like the brain, lungs, heart, and kidney. The liver reacts to a decrease in oncotic pressure with an increase in albumin synthesis. This is normally possible through the use of amino acids from the proteins introduced with the nutrients reaching the portal blood. If these are not sufficiently provided with the diet, amino acids are delivered to the liver from muscular proteins by systemic circulation. The liver is also the source of coagulation proteins, such as fibrinogen, fibronectin, and most of the v WF VIII, which are physiological components of the extracellular matrix of the vessel wall. While albumin is the main negative acute-phase protein, fibrinogen, fibronectin, and v WF VIII are positive acute-phase proteins. Acute illnesses cause the activation of defense mechanisms (acute-phase reaction) that may lead to an increase of fibrinolysis and an increase of plasma level of fibrinogen breakdown products, mainly fibrin and D-dimer. The measurement of the plasma level of the D-dimer has been used as a marker for venous thromboembolism, where a fourfold increase of the D-dimer plasma level was used as a negative prognostic marker in critically ill SARS-CoV-2 hospitalized patients. Increased fibrinolysis can take place in ischemic peripheral sites, where the mentioned coagulation proteins can become part of the provisional clot (e.g., in the lungs). Although critically ill SARS-CoV-2-infected patients are considered septic shock patients, albumin infusions have not been considered for hemodynamic resuscitation and as anticoagulants. The role of coagulation factors as provisional components of the extracellular matrix in case of generalized peripheral ischemia due to hypoalbuminemia and hypovolemia is discussed in this review.

Effect of electroacupuncture at "Weizhong" (BL40) on expression of muscular PDGF-CC, PDGFR-α and MMP-1 in rats with lumbar multifidus muscle injury

To observe the effect of electroacupuncture (EA) of "Weizhong" (BL40) on the expression of platelet-derived growth factor (PDGF)-CC, PDGF receptor (PDGFR)α and matrix metalloproteinase-1 (MMP-1) in rats with lumbar multifidus muscle injury (LMMI) so as to study its mechanisms underlying improvement of skeletal muscle injury. Fifty-four male SD rats were randomly divided into normal group (n=6), model group (n=24) and EA group (n=24), and the latter two groups were further divided into four subgroups (1, 3, 5 and 7 days), with 6 rats in each group. The LMMI model was established by injection of 0.5% bupivacaine (BPVC, 100 μL×4) into the multifidus along the L4 and L5 spinous process. EA (2 Hz/50 Hz, 1 mA) was applied to bilateral "Weizhong"(BL40) for 20 min, once daily for 1, 3, 5 and 7 days respectively, from the first day on after modeling. Histopathological changes of the left multifidus muscle were observed after H.E. staining, and the expression of PDGF-CC, PDGFR-α and MMP-1 proteins in the right multifidus was observed by Western blot. Compared with the normal group, the expression levels of PDGF-CC protein in the model subgroup 1 d, 3 d and 7 d were significantly decreased (P<0.05), and those of PDGFR-α and MMP-1 proteins in the model subgroup 5 d and 7 d, and PDGF-CC protein in the model subgroup 5 d significantly increased (P<0.05). In comparison with the model subgroups, the expression levels of PDGF-CC in the EA subgroup 3 d, 5 d and 7 d, PDGFR-α in the EA subgroup 5 d, and MMP-1 in the EA group 3 d and 5 d were significantly increased or significantly further increased (P<0.05). H.E. staining showed different shapes and uneven sizes, with large area of damage, enlarged muscle space and inflammatory cell infiltration in the model group, which was relatively milder in the EA subgroups particularly in subgroup 5 d and 7 d. EA stimulation of BL40 for about 5 days has a positive effect in promoting the repair of the injured multifidus muscle in LMMI rats, which may be related to its function in up-regulating the expression of muscular PDGF-CC, PDGFR-α and MMP-1 proteins.

Tomoh Masaki

Tomoh Masaki

Effects of Freshness and Heating Temperature on the Discoloration of Squid Meat Products

ABSTRACT Squid processed products such as dried-seasoned squid turn brown during storage, causing a change in quality. The main cause of this browning is melanoidin produced by the Maillard reaction. In this study, four types of squid were processed at different heating temperatures between 50 and 90°C and examined for suppression of the production of D-ribose, the main component of melanoidin. Furthermore, the color change of the squid meat with each heat treatment during storage of 32 days at 30°C was investigated. Bigfin reef squid and cuttlefish with a relatively high freshness decreased D-ribose generation as the heating temperature increased, and the browning during storage also decreased accordingly. In contrast, Humboldt squid with a low freshness did not generate new D-ribose at any heating temperature during storage. Nevertheless, the browning was reduced as the heating temperature increased. It is thought that the Maillard reaction was also reduced by the heat denaturation of muscular proteins. These results suggest that browning due to the Maillard reaction of squid meat is greatly affected by initial freshness and heating temperature.

Prediction of the Secretome and the Surfaceome: A Strategy to Decipher the Crosstalk between Adipose Tissue and Muscle during Fetal Growth.

Crosstalk between adipose and muscular tissues is hypothesized to regulate the number of muscular and adipose cells during fetal growth, with post-natal consequences on lean and fat masses. Such crosstalk largely remains, however, to be described. We hypothesized that a characterization of the proteomes of adipose and muscular tissues from bovine fetuses may enhance the understanding of the crosstalk between these tissues through the prediction of their secretomes and surfaceomes. Proteomic experiments have identified 751 and 514 proteins in fetal adipose tissue and muscle. These are mainly involved in the regulation of cell proliferation or differentiation, but also in pathways such as apoptosis, Wnt signalling, or cytokine-mediated signalling. Of the identified proteins, 51 adipokines, 11 myokines, and 37 adipomyokines were predicted, together with 26 adipose and 13 muscular cell surface proteins. Analysis of protein–protein interactions suggested 13 links between secreted and cell surface proteins that may contribute to the adipose–muscular crosstalk. Of these, an interaction between the adipokine plasminogen and the muscular cell surface alpha-enolase may regulate the fetal myogenesis. The in silico secretome and surfaceome analyzed herein exemplify a powerful strategy to enhance the elucidation of the crosstalk between cell types or tissues.

Quantitative iTRAQ LC-MS/MS reveals muscular proteome profiles of deep pressure ulcers.

Pressure ulcers (PUs) are a common clinical issue lacking effective treatment and validated pharmacological therapy in hospital settings. Ischemia–reperfusion injury of deep tissue, especially muscle, plays a vital role in the formation and development of the overwhelming majority of PUs. However, muscular protein expression study in PUs has not been reported. Herein, we aimed to investigate the muscular proteins profiles in PUs and to explore the pathological mechanism of PUs. The iTRAQ LC-MS/MS was conducted to detect the protein profiles in clinical muscle samples of PUs. The GO and KEGG pathways analyses were performed for annotation of differentially expressed proteins. Protein–protein interaction (PPI) network was constructed by STRING online database, and hub proteins were validated by the immunoblotting. Based on proteomics results, we found a number of proteins that were differentially expressed in PU muscle samples compared with the normal and identified unique proteins expression patterns between these two groups, suggesting that they might involve in pathological process of the disease. Importantly, cathepsin B and D, as well as other autophagy–lysosome and apoptosis associated proteins were identified. Further experiments characterize the expression of these proteins and their regulation in the process of apoptosis and autophagy. These findings may provide novel insights into the mechanisms of lysosome-associated pathways involved in the initiation of PUs. This is the first study linking proteomics to PUs muscle tissues, which indicated cathepsin B and D might be key drug target for PUs.