Degradation Of Myosin Heavy Chain Research Articles

Alteração nas frações das proteínas miofibrilares e maciez do músculo Longissimus de bovinos no período post mortem

Objetivou-se com o estudo identificar por eletroforese as mudanças nas frações das proteínas musculares durante período postmortem de bovinos de diferentes grupos genéticos e analisar a maciez da carne em amostras resfriadas por 24 horas (não maturadas) e maturadas por 7 dias. Foram utilizadas amostras do musculo Longissimus de quarenta e oito bovinos pertencentes a 4 grupos genéticos: 12 Nelore; 12 cruzados ½ Nelore ½ Aberdeen-Angus x Brahman; 12 Brangus; 12 cruzados ½ nelore ½ Aberdeen-Angus x Pardo, submetidos ao modelo biológico superprecoce. De cada uma delas foram retiradas duas fatias, uma não foi maturada e a outra maturada por 7 dias, a 2ºC. Na análise da força de cisalhamento, tanto as amostras não maturadas, quanto as submetidas a 7 dias de maturação não diferiram quanto à maciez da carne, mas todas apresentaram maciez aceitável, o que pode ser explicado pela baixa idade dos animais no momento do abate, o que foi proporcionado pelo sistema de engorda a que estes animais foram submetidos. Na análise das bandas de proteínas da carne, medida pela eletroforese, notou-se degradação da cadeia pesada da miosina e da Troponina -T e o aparecimento do fragmento de 30 kDa para todos os grupos genéticos após o período de 7 dias de maturação.Todos os grupos genéticos apresentaram boa maciez da carne, independentemente do tempo de maturação.

S2-4 - Involvement of E3 Ubiquitin ligases in Cigarette Smoke associated muscle catabolism

Epidemiological studies have identified tobacco smoking as a risk factor for sarcopenia, the age related loss of muscle mass and strength. Clinical, in vivo and in vitro studies have revealed that cigarette smoke (CS) induces skeletal muscle damage due to impaired muscle metabolism, increased inflammation and oxidative stress and activation of various intracellular signaling pathways. In order to investigate the cellular mechanisms by which CS leads to muscle catabolism, C2 myotubes were exposed to different levels of whole vapor phase CS. Myotube diameters, muscle proteins degradation and signaling pathways activation in response to CS exposure were examined by microscopy, Western blot and real time quantitative PCR. Exposure of C2 myotubes to CS caused a reduction in myotube diameters and degradation of the main contractile proteins: myosin heavy chain and actin proteins in a time- and dose-dependent manner. CS exposure to C2 myotubes also resulted in p38 MAPK phosphorylation, which led to up-regulation of the muscle specific E3 ubiquitin ligase enzymes: MAFbx/Atrogin-1 and MuRF1. Inhibition of p38 MAPK by SB203580 prevented both CS associated degradation of myosin heavy chain and up-regulation of the above E3 ubiquitin ligases. In addition, C2 exposure to CS resulted in IkBα degradation and NFkB activation which led to up-regulation of MuRF1 but not MAFbx/Atrogin-1. Our results demonstrate that vapor phase CS exposure to skeletal myotubes activates the p38 MAPK pathway leading to skeletal muscle cell damage and muscle protein breakdown mediated by muscle specific E3 ubiquitin ligases. However, MAFbx/Atrogin-1 is activated directly through p38 pathway while MuRF1 is also activated by p38 but through activation of NFkB leading to up-regulation of MuRF1. Our findings provide a possible molecular mechanism for the catabolic effects of CS in skeletal muscle.

Post-mortem timing of skeletal muscle biochemical and mechanical degradation

Fresh cadaveric human tissue is a valuable resource that is used to address important clinical questions. However, it is unknown how post-mortem time impacts skeletal muscle mechanical and biochemical properties. We simulated morgue conditions in rabbits and tested the passive mechanical properties of muscle bundles, and the degradation of myosin heavy chain, collagen, and titin at specific intervals up to 7 days post-mortem. While a great deal of inter-specimen variability was observed, it was independent of post-mortem time. Passive mechanics, myosin heavy chain, and collagen content were all unaffected while the titin protein degraded up to 80% over 7 days post-mortem. These data indicate that fresh cadaveric tissue may be used for passive mechanical testing and that certain biochemical properties are unchanged up to 7 days after death.

Physicochemical properties of natural actomyosin from threadfin bream (Nemipterus spp.) induced by high hydrostatic pressure

Changes of physicochemical properties in natural actomyosin (NAM) from threadfin bream (Nemipterus spp.) induced by high hydrostatic pressure (200, 400, 600MPa for 10, 30, 50min) were studied. The increase in turbidity of NAM was coincidental with the decrease in protein solubility with increasing pressure and time, suggesting the formation of protein aggregates. SDS–PAGE showed that polymerisation and degradation of myosin heavy chain were induced by high pressure. Ca2+-ATPase activity of NAM treated by high pressure was lost, suggesting the denaturation of myosin and the dissociation of actomyosin complex. Surface hydrophobicity of NAM increased when the pressure and pressurization time increased, indicating that the exposed hydrophobic residues increased upon application of high pressure. Decrease in total sulfhydryl content and increase in surface-reactive sulfhydryl content of NAM samples were observed with the extension of pressurizing time, indicating the formation of disulphide bonds through oxidation of SH groups or disulphide interchanges. The above changes of physicochemical properties suggested conformational changes of NAM from muscle of threadfin bream induced by high hydrostatic pressure.

Peroxynitrite induces degradation of myosin heavy chain via p38 MAPK and muscle-specific E3 ubiquitin ligases in C2 skeletal myotubes.

Oxidative stress and inflammation play an important role in the catabolism of skeletal muscles. Recently, cigarette smoke (CS) was shown to stimulate muscle catabolism by activation of p38 MAPK and up-regulation of the muscle-specific E3 ubiquitin ligases (E3s) atrogin-1 and MuRF1 which are over-expressed during muscle atrophy. Peroxynitrite (ONOO-), an oxidative ingredient of CS, also produced during oxidative stress and inflammation, was previously shown to induce ubiquitination and degradation of muscle proteins. To investigate the involvement of p38 MAPK and the muscle-specific E3s in ONOO--induced muscle catabolism, C2 myotubes, differentiated from a myoblast cell line, were exposed to ONOO- (25 μM) in a time-dependent manner. Following exposure, degradation of myosin heavy chain (MyHC) and actin, activation of p38 MAPK, and levels of atrogin-1 and MuRF1 were studied by Western blotting. Peak phosphorylation of p38 MAPK was observed at 1 h of ONOO- exposure. ONOO- caused a significant increase in the levels of atrogin-1 and MuRF1. In accordance, a significant decrease in MyHC levels was observed in a time-dependent manner. These findings support previous studies in which the catabolic effects of ONOO- were shown. In addition, ONOO- was demonstrated to induce degradation of muscle proteins by activation of p38 MAPK and up-regulation of the muscle-specific E3s atrogin-1 and MuRF1.

Distinct effects of methamphetamine on autophagy–lysosome and ubiquitin–proteasome systems in HL-1 cultured mouse atrial cardiomyocytes

The aim of this study is to investigate the molecular mechanism underling the cardiotoxicity of methamphetamine, a psychostimulant drug that is currently abused in the world. A mouse atrial cardiac cell line, HL-1, which retains phenotypes of cardiac cells and serves as a useful model for examining cardiac pathophysiology, was used for this purpose. During treatment with 1mM methamphetamine (MAP) for 3–48h, massive but transient cytoplasmic vacuolization (3–12h) followed by an intracellular accumulation of granules (24–48h) was observed under light microscopy. The vacuoles were surrounded by the lysosome membrane marker LAMP1, while the granules colocalized with the autophagy markers LC3 and p62 as well as ubiquitinated proteins. Western blot analysis showed that LC3 was activated during MAP administration, although p62 was not degraded but rather accumulated. Concordant with p62 accumulation, the nuclear translocation of an anti-oxidative transcription factor, Nrf2, and the subsequent induction of its target gene, HO-1, was observed, suggesting an impairment of autophagic protein degradation and the subsequent activation of the p62/Nrf2/HO-1 pathway. In addition, proteomic analysis revealed a reduction in myosin heavy chain (MHC) protein levels during MAP administration. The ubiquitination of MHC and the induction of the muscle sarcomere protein-specific E3 ubiquitin ligases MuRF1 and atrogin-1 were proved by immunoprecipitation and quantitative real-time PCR, respectively. Taken together, the vacuolization of lysosomes and the subsequent accumulation of autophagosomes indicate an impairment of autophagic protein degradation during MAP administration; on the other hand, the ubiquitination and subsequent degradation of MHC indicate the proper progression of proteasomal degradation.

The effects of acetaldehyde and acrolein on muscle catabolism in C2 myotubes

The toxic aldehydes acetaldehyde and acrolein were previously suggested to damage skeletal muscle. Several conditions in which exposure to acetaldehyde and acrolein is increased were associated with muscle wasting and dysfunction. These include alcoholic myopathy, renal failure, oxidative stress, and inflammation. A main exogenous source of both acetaldehyde and acrolein is cigarette smoking, which was previously associated with increased muscle catabolism. Recently, we have shown that exposure of skeletal myotubes to cigarette smoke stimulated muscle catabolism via increased oxidative stress, activation of p38 MAPK, and upregulation of muscle-specific E3 ubiquitin ligases. In this study, we aimed to investigate the effects of acetaldehyde and acrolein on catabolism of skeletal muscle. Skeletal myotubes differentiated from the C2 myoblast cell line were exposed to acetaldehyde or acrolein and their effects on signaling pathways related to muscle catabolism were studied. Exposure of myotubes to acetaldehyde did not promote muscle catabolism. However, exposure to acrolein caused increased generation of free radicals, activation of p38 MAPK, upregulation of the muscle-specific E3 ligases atrogin-1 and MuRF1, degradation of myosin heavy chain, and atrophy of myotubes. Inhibition of p38 MAPK by SB203580 abolished acrolein-induced muscle catabolism. Our findings demonstrate that acrolein but not acetaldehyde activates a signaling cascade resulting in muscle catabolism in skeletal myotubes. Although within the limitations of an in vitro study, these findings indicate that acrolein may promote muscle wasting in conditions of increased exposure to this aldehyde.

Thermal gelation properties of white croaker, walleye pollack and deepsea bonefish surimi after suwari treatment at various temperatures

The effects of setting (suwari) at around 40 °C on the breaking strength and breaking strain rate of thermal gels treated at 85 °C for 20 min during the following processing step were examined in association with the polymerization and degradation of myosin heavy chains (MHCs) for surimi prepared from white croaker, walleye pollack and deepsea bonefish. In the case of white croaker and walleye pollack, maximum values of breaking strength and breaking strain rate were obtained after suwari at 30–40 °C for both 30 and 60 min, at which temperature MHCs were polymerized. In comparison, these textual properties of the thermal gels decreased in surimi prepared from deepsea bonefish after suwari at around 38 °C for 30 min and at around 32 °C for 60 min, with concomitant degradation products of MHC. The textual properties of deepsea bonefish after suwari at temperatures >45 °C tended to be almost the same as those after suwari at temperatures of <30 °C, where neither polymerization nor degradation of MHC was observed.

Treatment of tumor‐induced cardiovascular dysfunction with losartan, an angiotensin II receptor antagonist

Tumor burden elicits a multitude of pathological responses from multiple organ systems. Part of this pathological response is cachexia; generalized as host tissue wasting. Angiotensin II(Ang II) has been implicated in the activation of the proteasome. Losartan is a well‐known selective and competitive Ang II receptor antagonist, which is hypothesized to lessen the pathological burden. Raised levels of mRNA of biomarkers for ubiquitin pathway such as MuRF and Bnip3 are present in tumor bearing mice, implicating the role of the ubiqutin pathway. Degradation of myosin heavy chain (MHC) also occurs in the ventricles of the heart. The heart has been observed using echocardiography, which shows a decrease in left ventricle function. Ex vivo cardiomyocyte isolations of tumor burdened mice show deficits in function. Losartan treatment ameliorates the pathology state; it decreases ubiquitin markers coupled with reductions of Bnip3, MuRF, and IL‐6 lessening the effect of cardiac degradation and preserving function. In cardiomyocyte isolations losartan normalized the contractions from tumor bearing mice, this mechanism will need to be explored further. Losartan successfully showed an improvement in cardiac function and normalization of single cardiomyocyte, more experiments are planned in the future to further elucidate the mechanisms of cachexia and the action of losartan on them.

Cigarette smoke and muscle catabolism in C2 myotubes

Previous studies have revealed evidence of muscular damage and up-regulation of genes associated with impaired muscle maintenance in smokers. Cigarette smoking has also been associated with sarcopenia, the age-related loss of muscle mass and strength. In order to investigate the cellular mechanisms by which cigarette smoke (CS) promotes muscle catabolism, C2 myotubes from an in vitro skeletal muscle cell line, were exposed to different levels of whole vapor phase CS using a controlled CS exposure apparatus. Exposure of C2 myotubes to CS caused a reduction in diameter of myotubes and a time- and dose-dependent degradation of myosin heavy chain. Also, CS exposure resulted in increased intracellular oxidative stress and p38 MAPK phosphorylation, which led to up-regulation of the muscle specific E3 ubiquitin ligases: MAFbx/atrogin-1 and MuRF1. Pretreatment with the antioxidant N-acetylcysteine and inhibition of p38 MAPK by SB203580 prevented CS induced catabolism. In conclusion, our results demonstrate that exposure of skeletal myotubes to CS leads to increased oxidative stress and activation of the p38 MAPK pathway resulting in muscle cell atrophy and breakdown of muscle protein mediated by muscle specific E3 ubiquitin ligases. Our findings provide a possible molecular mechanism for the catabolic effects of CS in skeletal muscle.

Abstract 18430: Human Molecular Genetic and Functional Studies Identify TRIM63, Encoding Muscle RING Finger Protein 1, as a Novel Gene for Human Hypertrophic Cardiomyopathy

Rationale: A delicate balance between protein synthesis and degradation maintains cardiac size and function. TRIM63 encoding Muscle RING Finger 1 (MuRF1) maintains muscle protein homeostasis by tagging the sarcomere proteins with ubiquitin for subsequent degradation by the Ubiquitin-Proteasome System (UPS). Objectives: To determine the pathogenic role of TRIM63 in human hypertrophic cardiomyopathy (HCM). Methods and Results: Sequencing of TRIM63 gene in 302 HCM probands (250 Caucasians) and 339 controls (262 Caucasians) led to identification of two missense (p.A48V and p.I130M) and a deletion (p.Q247X) variants exclusively in the HCM probands. These three variants were absent in 751 additional controls screened by TaqMan assays. Likewise, rare variants were enriched in the Caucasian HCM population (11/250, 4.4% vs. 3/262, 1.1%, respectively, p=0.024). Expression of the mutant TRIM63 was associated with mislocalization of TRIM63 to sarcomere Z disks, impaired auto-ubiquitination, reduced ubiquitinylation and UPS-mediated degradation of myosin heavy chain 6, cardiac myosin binding protein C, calcineurin (PPP3CB), and p-mTOR in adult cardiac myocytes. Induced expression of the mutant TRIM63 in the mouse heart was associated with cardiac hypertrophy, activation of the mTOR-S6K and calcineurin pathways and expression of the hypertrophic markers, which were normalized upon turning off expression of the mutant protein. Conclusions: TRIM63 mutations, identified in patients with HCM, impart loss-of-function effects on E3 ligase activity and are likely causal mutations in HCM. The findings implicate impaired protein degradation in the pathogenesis of HCM.

Interferon-γ Causes Cardiac Myocyte Atrophy via Selective Degradation of Myosin Heavy Chain in a Model of Chronic Myocarditis

Interferon-γ (IFN-γ), a proinflammatory cytokine, has been implicated in the pathogenesis of a number of forms of heart disease including myocarditis and congestive heart failure. In fact, overexpression of IFN-γ in mice causes dilated cardiomyopathy. However, the direct effects of IFN-γ on cardiac myocytes and the mechanism by which it causes cardiac dysfunction have not been described. Here, we present the molecular pathology of IFN-γ exposure and its effect on myofibrillar proteins in isolated neonatal rat ventricular myocytes. Treatment with IFN-γ caused cardiac myocyte atrophy attributable to a specific decrease in myosin heavy chain protein. This selective degradation of myosin heavy chain was not accompanied by a decrease in total protein synthesis or by an increase in total protein degradation. IFN-γ increased both proteasome and immunoproteasome activity in cardiac myocytes and their inhibition blocked myosin heavy chain loss and myocyte atrophy, whereas inhibition of the lysosome or autophagosome did not. Collectively, these results provide a mechanism by which IFN-γ causes cardiac pathology in the setting of chronic inflammatory diseases.

Proteomic evaluation of myofibrillar carbonylation in chilled fish mince and its inhibition by catechin

The present study investigates the susceptibility of individual myofibrillar proteins from mackerel (Scomber scombrus) mince to undergo carbonylation reactions during chilled storage, and the antioxidant capacity of (+)-catechin to prevent oxidative processes of proteins. The carbonylation of each particular protein was quantified by combining the labelling of protein carbonyls by fluorescein-5-thiosemicarbazide (FTSC) with 1-D or 2-D gel electrophoresis. Alpha skeletal actin, glycogen phosphorylase, unnamed protein product (UNP) similar to enolase, pyruvate kinase, isoforms of creatine kinase, aldolase A and an isoform of glyceraldehyde 3-phosphate dehydrogenase (G3PDH) showed elevated oxidation in chilled non-supplemented mince. Myosin heavy chain (MHC) was not carbonylated in chilled muscle, but an extensive MHC degradation was observed in those samples. The supplementation of catechin reduced protein oxidation and lipid oxidation in a concentration-dependent manner: control>25>100≈200ppm. Therefore, the highest catechin concentrations (100 and 200ppm) exhibited the strongest antioxidant activity. Catechin (200ppm) reduced significantly carbonylation of protein spots identified as glycogen phosphorylase, pyruvate kinase muscle isozyme, isoforms of creatine kinase. Conversely, catechin was ineffective to inhibit the oxidation of actin and UNP similar to enolase. These results draw attention to the inefficiency of catechin to prevent actin oxidation, in contrast to the extremely high efficiency of catechin in inhibiting oxidation of lipids and other proteins.

Human Molecular Genetic and Functional Studies Identify TRIM63 , Encoding Muscle RING Finger Protein 1, as a Novel Gene for Human Hypertrophic Cardiomyopathy

A delicate balance between protein synthesis and degradation maintains cardiac size and function. TRIM63 encoding Muscle RING Finger 1 (MuRF1) maintains muscle protein homeostasis by tagging the sarcomere proteins with ubiquitin for subsequent degradation by the ubiquitin-proteasome system (UPS). To determine the pathogenic role of TRIM63 in human hypertrophic cardiomyopathy (HCM). Sequencing of TRIM63 gene in 302 HCM probands (250 white individuals) and 339 control subjects (262 white individuals) led to identification of 2 missense (p.A48V and p.I130M) and a deletion (p.Q247*) variants exclusively in the HCM probands. These 3 variants were absent in 751 additional control subjects screened by TaqMan assays. Likewise, rare variants were enriched in the white HCM population (11/250, 4.4% versus 3/262, 1.1%, respectively, P=0.024). Expression of the mutant TRIM63 was associated with mislocalization of TRIM63 to sarcomere Z disks, impaired auto-ubiquitination, reduced ubiquitination and UPS-mediated degradation of myosin heavy chain 6, cardiac myosin binding protein C, calcineurin (PPP3CB), and p-MTOR in adult cardiac myocytes. Induced expression of the mutant TRIM63 in the mouse heart was associated with cardiac hypertrophy, activation of the MTOR-S6K and calcineurin pathways, and expression of the hypertrophic markers, which were normalized on turning off expression of the mutant protein. TRIM63 mutations, identified in patients with HCM, impart loss-of-function effects on E3 ligase activity and are probably causal mutations in HCM. The findings implicate impaired protein degradation in the pathogenesis of HCM.

The Effect of Different Types of Fibers on Protein Quality of Crab Leg Analog Paste and Gel Made from Alaska Pollock (Theragra chalcogramma)

The aim of this investigation was to evaluate the effect of wheat, citrus, and carrot fiber on protein oxidation and denaturation of crab leg analog pastes and gels produced from Alaska pollock surimi. There were no significant differences between protein carbonyl contents of the crab leg analog pastes with and without dietary fibers (DF; p > 0.05). The extractability of salt soluble protein in crab leg analog pastes significantly decreased by the addition of DF (p < 0.05), whereas it did not change in the crab leg analog gels (p > 0.05). The electrophoretic patterns in the pastes and gels showed that the addition of carrot fiber followed by wheat fiber and citrus fiber protected the degradation of myosin heavy chains in paste.

EFFECTS OF BAMBARA GROUNDNUT PROTEIN ISOLATE ON PROTEIN DEGRADATION AND GEL PROPERTIES OF SURIMI FROM SARDINE (SARDINELLA ALBELLA)

ABSTRACT Effects of protein isolate from bambara groundnut (BGPI) at different levels (0–1.5%) on autolysis and gel property of surimi from sardine (Sardinella albella) were investigated. Higher inhibitory activity against autolysis for kamaboko (40/90C) and modori (65/90C) gels was observed when BGPI level increased up to 1%. BGPI effectively prevented the degradation of myosin heavy chain in a concentration-dependent manner in both gels. This was associated with the increased breaking force and deformation of gels added with BGPI (P < 0.05). Water-holding capacity of gels was improved with increasing level of BGPI incorporated (P < 0.05). However, whiteness of kamaboko and modori gels slightly decreased with increasing BGPI levels (P < 0.05). Microstructure of kamaboko and modori gels added with 1% BGPI had the denser and more ordered fibrillar structure, indicating a preventive effect of BGPI on hydrolysis of myofibrillar proteins. PRACTICAL APPLICATIONS Surimi from dark-fleshed fish is generally prone to protein degradation caused by heat-activated proteases. Proteolytic disintegration of myofibrillar proteins leads to gel weakening of surimi. Gel-forming ability of myofibrillar proteins is the most important functional requirement to provide the superior quality of surimi-based products. Protein isolate from bambara groundnut (BGPI) containing protease inhibitors could be used to lower autolysis of sardine surimi caused by endogenous proteases. In addition, BGPI might serve as a co-gelling agent or binder in surimi gels. Thus, BGPI could be used as the promising protein additive for surimi industry.

Influence of oxidation on myofibrillar proteins degradation from bovine via μ-calpain

Abstract The objective of this study was to investigate the effect of oxidation on proteolysis of myofibrillar proteins via μ-calpain. Myofibrillar proteins prepared from bovine muscle were exposed to in vitro oxidation to produce varying levels of protein modification by use of H 2 O 2 and Fe 2+ . The protein oxidation level was measured by the carbonyl content. Modified proteins were then incubated with active μ-calpain and the rates of protein degradation were analyzed via SDS–PAGE and western blotting. The results revealed that increased protein oxidation enhanced the degradation of myosin heavy chain (MHC) and α-actinin, reduced the degradation of 38 kDa troponin-T, but had little influence on the 30 kDa degradation fragment derived from troponin-T and the degradation of actin. These findings demonstrated that the oxidative modification of myofibrillar proteins changed their susceptibility to μ-calpain and provided a mechanistic link connecting oxidation with myofibrillar proteolysis.

Degradation of myofibrils in cultured yellowtail Seriola quinqueradiata burnt meat: effects of a myofibril-bound EDTA-sensitive protease

“Burnt meat” is a term used to describe the white (pale, grainy, exudative) muscle of yellowtail or tuna. It (with lightness parameter, L* ≥ 55) was observed after 2 h storage in the suffocate in air (SA) 29°C group and after 4 h storage in the spinal cord destruction (SCD) 29°C group. In the SA 17°C group, burnt meat was also observed after 4 h storage. In contrast, the meat in the SCD 17°C group was normal until after 12 h storage. The myosin heavy chain (MHC) was more degraded than the other myofibrillar proteins, and some protein bands increased in the burnt meat. The protease that leads to the degradation of MHC was investigated using myofibrils from the meat. EDTA completely suppressed the degradation, indicating that a myofibril-bound EDTA-sensitive protease (MBESP) may exist in yellowtail muscle and this caused the degradation of MHC. The optimum pH and temperature of MBESP in yellowtail were 5.0 and 50–60°C, respectively.

Cryoprotective Effect of Sericin Enzymatic Peptides on the Freeze-Induced Denaturation of Grass Carp Surimi

In this study, cryoprotective effects of sericin enzymatic peptides (SEP) on the freeze-induced denaturation of grass carp surimi were evaluated on the basis of sulfhydryl content and surface hydrophobicity of actomyosin, as well as the SDS-PAGE pattern of myosin heavy chain (MHC) of myofibrillar proteins. Results show that SEP, containing a high polar amino acid content and abundant in amino acids with hydroxyl-containing side chain (Ser and Thr), was effective in preventing the decrease of SH content, slowing down the exposure of buried hydrophobic residues on the protein surface, and retarding the degradation of MHC in a non-linear dosage-dependent way. These findings suggest that SEP obtained in our study appear to be a promising cryoprotectant applied in the frozon storage of surimi.

Exercise training has beneficial anti-atrophy effects by inhibiting oxidative stress-induced MuRF1 upregulation in rats with diabetes

AimsMuRF1 E3 ubiquitin ligase has been identified as a mediator of skeletal muscle wasting in various skeletal muscle atrophy models, and its expression is upregulated by oxidative stress. Exercise training could decrease oxidative stress and restore the atrophied skeletal muscle. Here, our aim was to investigate whether exercise training has any effect on MuRF1 expression in rats with diabetes. Main methodsRats with streptozotocin-induced diabetes were subjected to exercise training, after which oxidative stress was determined, and MuRF1 expression was analyzed by immunohistochemistry, real-time RT-PCR and Western blot analysis. In addition, we analyzed C2C12 myotubes in an in vitro model to examine the effects of oxidative stress on the protein levels of MuRF1 and myosin heavy chain (MHC). Key findingsWhile oxidative stress and MuRF1 expression were increased in rats with diabetes, exercise training diminished the skeletal muscle wasting in diabetic rats by decreasing oxidative stress and inhibiting MuRF1 expression at both the mRNA and protein levels. In addition, oxidative stress-induced MuRF1 upregulation promoted proteasome dependent degradation of the myosin heavy chain (MHC) in C2C12 myotubes. SignificanceOur study provides the first evidence that the beneficial anti-atrophy effects of exercise training on diabetes might be mediated by inhibiting oxidative stress-induced MuRF1 upregulation and preventing MuRF1-mediated degradation of MHC.