Myosin Heavy Chain Content Research Articles

Effect of xanthan gum on the quality of low sodium salted beef and property of myofibril proteins

The effects of xanthan gum (0 % and 0.3 %) on the quality of low sodium (2.0 %, 2.4 %, 2.8 %, 3.2 %, 3.6 % and 4.0 %) salted beef and property of myofibril proteins (MP) extracted from salted beef were researched. Changes in the salting absorptivity, cooking loss, shear force, color and sensory analysis showed that xanthan gum had a positive effect on the quality of salted beef with low salinity (2.0 %, 2.4 % and 2.8 %). MP of salted beef treated with xanthan gum had higher solubility, lower hydrogen bond than that without it (P < 0.05). The decrease of surface hydrophobicity and intrinsic fluorescence intensity indicated that the chromophore of protein was brought into a hydrophobic environment in the presence of xanthan gum. The electrophoresis showed that xanthan gum could improve the concentration of myosin heavy chain, paramyosin and actin after tumble-salting. The data suggested that salted beef and its MP treated with xanthan gum and 2.8 % salt (XS3) had the best properties. Together, xanthan gum could be considered as a sodium salt substitute for the development of low sodium meat products.

Myosin heavy chain expression relationships to power-load and velocity-load curves

Velocity- and power-based training are popular methods of determining training session loads and volumes. One factor that may influence load-velocity and load-power properties of an individual is the myosin heavy chain (MHC) composition of the muscle. The aim of this study was to examine the relationship between MHC composition and both load-velocity and load-power properties of muscle performance. Forty-two men with a variety of training backgrounds took part in this study (mean±SD; age=22.4±3.5 yrs, hgt=1.78±0.07 m, BW=78.7±13.3 kg). After testing leg extension one repetition maximum (1 RM), subjects performed maximal effort leg extensions at loads from 30% to 90% 1 RM. Muscle biopsies from the vastus lateralis were analyzed via SDS-PAGE electrophoresis technique for MHC content (IIx=13.8±12.9%, IIa=49.4±10.3%, I=36.8±11.3%). Leg extension rotational velocity and power were plotted against relative loads for all subjects. Significant correlations (P<0.05) were observed for MHC IIa with all performance variables (i.e. slopes, intercepts, peaks and relative loads). Relationships indicated that greater %MHC IIa was associated with greater velocity intercepts, more negative load-velocity slopes, greater maximal power, and with maximal power occurring at a lower relative intensity (% 1 RM). These data indicate that muscle velocity and power characteristics appear to be partially influenced by MHC content in a manner consistent with single muscle fiber contractile properties.

Protein oxidation analysis based on comparative proteomic of Russian sturgeon (Acipenser gueldenstaedti) after sous-vide cooking

Russian sturgeon meat is a highly perishable food product due to the microbial spoilage. Sous-vide cooking (SVC) at 40 °C, 50 °C and 60 °C with short-term time was applied to sturgeon fillets for the extension of shelf-life and the effect was investigated during storage at 4 °C. Results showed that SVC at 60 °C could effectively inhibit the growth of Aeromonas and Pseudomonas in samples. However, lipid oxidation and protein oxidation and degradation were aggravated with the myosin light chain (MLC), myosin heavy chain (MHC) and sulfhydryl content reduced after the treatment. Proteomics indicated that differentially expressed proteins were mainly involved in cellular component (CC) and biological process (BP). In this experiment, SVC were useful to preserve meat products, and the problem of protein oxidation should be further explored.

Myosin Heavy Chain Composition, Creatine Analogues, and the Relationship of Muscle Creatine Content and Fast-Twitch Proportion to Wilks Coefficient in Powerlifters.

Machek, SB, Hwang, PS, Cardaci, TD, Wilburn, DT, Bagley, JR, Blake, DT, Galpin, AJ, and Willoughby, DS. Myosin heavy chain composition, creatine analogues, and the relationship of muscle creatine content and fast-twitch proportion to Wilks coefficient in powerlifters. J Strength Cond Res 34(11): 3022-3030, 2020-Little data exist on powerlifting-specific skeletal muscle adaptations, and none elucidate sex differences in powerlifters. Powerlifters tend to display higher fast-twitch fiber content and phosphagen system dependence. Nevertheless, it is unknown whether fast-twitch fiber or muscle creatine content are predictive of competitive powerlifting performance (via Wilks coefficient). Twelve actively competing powerlifters (PL; n = 6M/6F; age = 21.3 ± 1.0; 3.0 ± 1.8 year competing; 7.3 ± 6.6 meets attended) and 10 sedentary controls (CON; n = 5M/5F; age = 19.4 ± 2.0 year) underwent vastus lateralis muscle biopsies and venipuncture to compare the myosin heavy chain (MHC) fiber type and creatine analogue profiles between groups of both sexes, and determine whether MHC IIa and muscle total creatine (MTC) composition predict powerlifting performance. Samples were analyzed for specific MHC isoform (I, IIa, and IIx) content via mixed homogenate SDS-PAGE, and creatine analogues (MTC, muscle creatine transporter [SLC6A8], serum total creatine [STC], and serum creatinine [CRT]). Furthermore, MHC IIa and MTC content were compared with Wilks coefficient using Pearson correlation coefficients. Male PL MHC content was 50 ± 6% I, 45 ± 6% IIa, and 5 ± 11% IIx, versus 46 ± 6% I, 53 ± 6 IIa, and 0% IIx in female PL. Conversely, male CON MHC content was 33 ± 5% I, 38 ± 7% IIa, and 30 ± 8% IIx, vs. 35 ± 9% I, 44 ± 8% IIa, and 21 ± 17% IIx in female CON. Muscle total creatine, SLC6A8, STC, and CRT did not significantly differ between groups nor sexes. Finally, neither MHC IIa content (r = -0.288; p = 0.364) nor MTC (r = 0.488; p = 0.108) significantly predicted Wilks coefficient, suggesting these characteristics alone do not determine powerlifting skill variation.

MitoTEMPOL, a mitochondrial targeted antioxidant, prevents sepsis-induced diaphragm dysfunction

Clinical studies indicate that sepsis-induced diaphragm dysfunction is a major contributor to respiratory failure in mechanically ventilated patients. Currently there is no drug to treat this form of diaphragm weakness. Sepsis-induced muscle dysfunction is thought to be triggered by excessive mitochondrial free radical generation; we therefore hypothesized that therapies that target mitochondrial free radical production may prevent sepsis-induced diaphragm weakness. The present study determined whether MitoTEMPOL, a mitochondrially targeted free radical scavenger, could reduce sepsis-induced diaphragm dysfunction. Using an animal model of sepsis, we compared four groups of mice: 1) sham-operated controls, 2) animals with sepsis induced by cecal ligation puncture (CLP), 3) sham controls given MitoTEMPOL (10 mg·kg-1·day-1 ip), and 4) CLP animals given MitoTEMPOL. At 48 h after surgery, we measured diaphragm force generation, mitochondrial function, proteolytic enzyme activities, and myosin heavy chain (MHC) content. We also examined the effects of delayed administration of MitoTEMPOL (by 6 h) on CLP-induced diaphragm weakness. The effects of MitoTEMPOL on cytokine-mediated alterations on muscle cell superoxide generation and cell size in vitro were also assessed. Sepsis markedly reduced diaphragm force generation. Both immediate and delayed MitoTEMPOL administration prevented sepsis-induced diaphragm weakness. MitoTEMPOL reversed sepsis-mediated reductions in mitochondrial function, activation of proteolytic pathways, and decreases in MHC content. Cytokines increased muscle cell superoxide generation and decreased cell size, effects that were ablated by MitoTEMPOL. MitoTEMPOL and other compounds that target mitochondrial free radical generation may be useful therapies for sepsis-induced diaphragm weakness.

Cancer Cachexia Induces Preferential Skeletal Muscle Myosin Loss When Combined With Denervation.

Patients with cancer cachexia (CCX) suffer from muscle wasting, which is often but not always accompanied by selective loss of myosin. Here we examined the effects of CCX on muscle mass and myosin heavy chain (MyHC) expression in denervated (DEN) muscles, especially focusing on the protein synthesis and degradation pathways. Male CD2F1 mice were randomly divided into control (CNT) and CCX groups and their left sciatic nerve was transected. CCX was induced by an intraperitoneal injection of colon 26 cells. After 14 days, the serum concentration of IL-6 and corticosteroid was higher in CCX mice than in CNT mice. The combination of CCX with DEN (CCX + DEN) resulted in a marked reduction of the gastrocnemius muscle weight (−69%) that was significantly lower than DEN (−53%) or CCX (−36%) alone. CCX had no effect on MyHC content, but it elicited a preferential MyHC loss when combined with DEN. The expression levels of autophagy markers cathepsin D and LC3BII/I ratio were markedly higher in the CCX + DEN group than in the CNT + DEN and the CCX groups. Paradoxically, there was an increase in protein synthesis rate and phosphorylation levels of p70S6K and rpS6, markers of mTORC1 signaling, in the CNT + DEN group, and these molecular alterations were inhibited in the CCX + DEN group. Our data indicate that CCX aggravates muscle atrophy in DEN muscles by inducing seletive loss of myosin, which involves inactivity dependent mechanisms that is likely to be a consequence of increased autophagy-mediated protein breakdown coupled with impaired protein synthesis.

Mechanisms Underlying TNFα‐Induced Hyperreactivity in Airway Smooth Muscle

Inflammation and pro‐inflammatory cytokines (e.g., TNFα, IL‐13) induce airway smooth muscle (ASM) hyper‐reactivity and remodeling characteristic of asthma. We hypothesized that exposure to TNFα (and IL‐13) increases isometric force generation in porcine ASM via several underlying mechanisms: 1) increasing sensitivity to ACh stimulation; 2) enhancing the cytosolic Ca2+ ([Ca2+]cyt) response to ACh; 3) increasing the Ca2+ sensitivity of force generation; 4) enhancing the Ca2+‐dependent phosphorylation of myosin regulator light chain (rMLC); 5) promoting expression of non‐muscle rMLC; 6) increasing actin and myosin heavy chain (MyHC) content (i.e., the number of contractile units); and/or 7) promoting cytoskeletal remodeling (actin polymerization). Studies were performed on intact ASM strips (~1 mm wide × ~5 mm long) dissected from porcine tracheas obtained from a local abattoir. The ASM strips were placed in PSS with and without TNFα (100 ng/ml) for 24 h. The ACh concentration dependence of force generation ASM was determined (ACh range from 10 nM to 1mM), and the EC50 (i.e., the ACh concentration that produces 50% of maximal ASM force) was determined. In control, untreated ASM, the EC50 for ACh was 2.6 μM compared to 1.3 μM following TNFα treatment. We found that across all ACh concentrations, ASM force increased after TNFα treatment with an ~50% increase in maximum ASM force. The [Ca2+]cyt response induced by the EC50 [ACh] was similar in control and TNFα treated ASM. Thus, with an increase in force and no effect on [Ca2+]cyt, there was an apparent increase in Ca2+ sensitivity of force after TNFα treatment. However, in both control and TNFα treated ASM, the extent of rMLC phosphorylation induced by ACh stimulation was not affected by TNFα treatment. Importantly, the extent of rMLC phosphorylation at the ACh EC50 was comparable between control and TNFα treatment indicating no change in Ca2+ sensitivity. The expression of non‐muscle rMLC (determined by 2D gel electrophoresis) was also unaffected by TNFα treatment. Total actin and MyHC concentrations increased by ~45% following TNFα treatment; thus, the number of contractile units contributing to force increased. This was reflected by a marked increase in the Ca2+ activation of ATP consumption (cross‐bridge cycling) of ASM following TNFα treatment. Cytoskeletal remodeling was evaluated by ACh‐induced actin polymerization (F‐/G‐actin ratio) but was found to be unaffected by TNFa treatment. Together, our results show that two primary mechanisms underlie the marked increase in ASM force generation induced by 24‐h TNFα exposure: 1) an increase in ACh sensitivity, and 2) an increase in actin and MyHC concentrations (number of contractile units).Support or Funding InformationSupported by NIH grant HL126451 (GCS) and HL150890 (GCS)

SS31, a mitochondrially targeted antioxidant, prevents sepsis-induced reductions in diaphragm strength and endurance.

Sepsis-induced diaphragm dysfunction contributes to respiratory failure and mortality in critical illness. There are no treatments for this form of diaphragm weakness. Studies show that sepsis-induced muscle dysfunction is triggered by enhanced mitochondrial free radical generation. We tested the hypothesis that SS31, a mitochondrially targeted antioxidant, would attenuate sepsis-induced diaphragm dysfunction. Four groups of mice were studied: 1) sham-operated controls, 2) sham-operated+SS31 (10 mg·kg-1·day-1), 3) cecal ligation puncture (CLP), and 4) CLP+SS31. Forty-eight hours postoperatively, diaphragm strips with attached phrenic nerves were isolated, and the following were assessed: muscle-field-stimulated force-frequency curves, nerve-stimulated force-frequency curves, and muscle fatigue. We also measured calpain activity, 20S proteasomal activity, myosin heavy chain (MHC) levels, mitochondrial function, and aconitase activity, an index of mitochondrial superoxide generation. Sepsis markedly reduced diaphragm force generation; SS31 prevented these decrements. Diaphragm-specific force generation averaged 30.2 ± 1.4, 9.4 ± 1.8, 25.5 ± 2.3, and 27.9 ± 0.6 N/cm2 for sham, CLP, sham+SS31, and CLP+SS31 groups (P < 0.001). Similarly, with phrenic nerve stimulation, CLP depressed diaphragm force generation, effects prevented by SS31. During endurance trials, force was significantly reduced with CLP, and SS31 prevented these reductions (P < 0.001). Sepsis also increased diaphragm calpain activity, increased 20S proteasomal activity, decreased MHC levels, reduced mitochondrial function (state 3 rates and ATP generation), and reduced aconitase activity; SS31 prevented each of these sepsis-induced alterations (P ≤ 0.017 for all indices). SS31 prevents sepsis-induced diaphragm dysfunction, preserving force generation, endurance, and mitochondrial function. Compounds with similar mechanisms of action may be useful therapeutically to preserve diaphragm function in patients who are septic and critically ill.NEW & NOTEWORTHY Sepsis-induced diaphragm dysfunction is a major contributor to mortality and morbidity in patients with critical illness in intensive care units. Currently, there is no proven pharmacological treatment for this problem. This study provides the novel finding that administration of SS31, a mitochondrially targeted antioxidant, preserves diaphragm myosin heavy chain content and mitochondrial function, thereby preventing diaphragm weakness and fatigue in sepsis.

Magnetic Hyperthermia Using Self-Controlled Heating Elements Consisting of Fe-Al Milling Alloy Induces Cancer Cell Apoptosis while Preserving Skeletal Muscle

Necrosis-inducing anticancer drugs enhance high-mobility group box 1 (HMGB1) release during cell necrosis, and HMGB1-induced autophagy in skeletal muscle induces muscle atrophy. We evaluated the efficacy of magnetic hyperthermia therapy (MHT) using a low-energy magnetic field and self-controlled heating elements in tumor treatment. MHT-induced apoptosis by heating mouse subcutaneous tumors at 43°C using a heat-controlling iron-aluminum (Fe-Al) milling alloy. In contrast, MHT using Fe line-induced necrosis by heating to approximately 100°C. Furthermore, MHT with Fe-Al milling alloy reduced stemness. In hyperthermia using age line or Fe-Al milling alloy, both of them provided histological degeneration in skeletal muscle; however, qualitative differences were observed. MHT using Fe-line induced pronounced autophagy, decrease of myosin heavy chain content, and increase in serum HMGB1. In contrast, MHT using Fe-Al milling alloy induced heat shock protein 90 but no autophagy and decreased serum HMGB1. Therefore, MHT using Fe-Al milling alloy might be a good method for local treatment of tumors to reduce skeletal muscle atrophy.

Skeletal Muscle Fiber Type and Morphology in a Middle-Aged Elite Male Powerlifter Using Anabolic Steroids

Powerlifting regularly exposes athletes to extreme stimuli such as chronic heavy resistance training (HRT), and many powerlifters choose to augment their performance with anabolic–androgenic steroids (AAS). However, little is known about the myocellular adaptations that occur from long-term HRT and AAS use, especially into middle age. We were presented with the unique opportunity to study muscle cells from an elite-level powerlifter (EPL; age 40 years) with ≥ 30 years of HRT experience and ≥ 15 years of AAS use. The purpose of this case study was to identify myocellular characteristics [myosin heavy chain (MHC) fiber type, fiber size, and myonuclear content] in EPL, as well as compare these data to existing literature. The participant underwent a resting vastus lateralis muscle biopsy and single fibers were analyzed for MHC content via SDS-PAGE. A subset of fibers underwent MHC-specific imaging analysis via confocal microscopy to identify cell size (cross-sectional area, CSA) and myonuclear domain (MND) size. MHC fiber type distribution was 9% I, 12% I/IIa, 79% IIa, and 0% other isoforms. This pure MHC IIa (fast-twitch) fiber content was amongst the highest reported in the literature. Imaging analysis of MHC IIa fibers revealed a mean CSA of 4218 ± 933 μm2 and MND of 12,548 ± 3181 μm3. While the fast-twitch fiber CSA was comparable to values in previous literature, mean MND was smaller than has been reported in untrained men, implying greater capacity for growth and repair. These findings showcase the unique muscle cell structure of an elite powerlifter, extending the known physiological limits of human muscle size and strength.

Myofibrillar function differs markedly between denervated and dexamethasone-treated rat skeletal muscles: Role of mechanical load.

Although there is good evidence to indicate a major role of intrinsic impairment of the contractile apparatus in muscle weakness seen in several pathophysiological conditions, the factors responsible for control of myofibrillar function are not fully understood. To investigate the role of mechanical load in myofibrillar function, we compared the skinned fiber force between denervated (DEN) and dexamethasone-treated (DEX) rat skeletal muscles with or without neuromuscular electrical stimulation (ES) training. DEN and DEX were induced by cutting the sciatic nerve and daily injection of dexamethasone (5 mg/kg/day) for 7 days, respectively. For ES training, plantarflexor muscles were electrically stimulated to produce four sets of five isometric contractions each day. In situ maximum torque was markedly depressed in the DEN muscles compared to the DEX muscles (-74% vs. -10%), whereas there was not much difference in the degree of atrophy in gastrocnemius muscles between DEN and DEX groups (-24% vs. -17%). Similar results were obtained in the skinned fiber preparation, with a greater reduction in maximum Ca2+-activated force in the DEN than in the DEX group (-53% vs. -16%). Moreover, there was a parallel decline in myosin heavy chain (MyHC) and actin content per muscle volume in DEN muscles, but not in DEX muscles, which was associated with upregulation of NADPH oxidase (NOX) 2, neuronal nitric oxide synthase (nNOS), and endothelial NOS expression, translocation of nNOS from the membrane to the cytosol, and augmentation of mRNA levels of muscle RING finger protein 1 (MuRF-1) and atrogin-1. Importantly, mechanical load evoked by ES protects against DEN- and DEX-induced myofibrillar dysfunction and these molecular alterations. Our findings provide novel insights regarding the difference in intrinsic contractile properties between DEN and DEX and suggest an important role of mechanical load in preserving myofibrillar function in skeletal muscle.

Increased physical activity does not improve obesity-induced decreases in muscle quality in zebrafish (Danio rerio).

Obesity has a negative effect on muscle contractile function, and the effects of obesity are not reversed by weight loss. It is therefore important to determine how muscle function can be restored, and exercise is the most promising approach. We tested the hypothesis (in zebrafish, Danio rerio) that moderate aerobic exercise (forced swimming for 30 min/day, raising metabolic rates to at least twice resting levels) will alleviate the negative effects of obesity on muscle function. We allocated zebrafish randomly to experimental treatments in a fully factorial design with diet treatment [three levels: lean control, diet-induced obese, obese followed by weight loss (obese-lean)], and exercise (exercise and sedentary control) as independent factors. Treatments were conducted for 10 wk, and we measured locomotor performance, isolated muscle mechanics, and myosin heavy chain composition. Obesity led to decreased muscle force production per unit area (P = 0.01), and slowed muscle contraction (P = 0.004) and relaxation rates (P = 0.02). These effects were not reversible by weight loss or exercise. However, at the level implemented in our experimental animals, neither diet nor exercise affected swimming performance or myosin heavy chain concentrations. The moderate levels of exercise we implemented therefore are not sufficient to reverse the effects of obesity on muscle function, and higher intensity or a combination of modes of exercise may be necessary to improve muscle quality during obesity and following weight loss.NEW & NOTEWORTHY Obesity can have a negative effect on muscle function and thereby compromise mobility. Even though aerobic exercise has many physiological benefits in obese and normal-weight individuals, we show that in zebrafish aerobic exercise does not improve obesity-induced reductions in muscle contractile function. A combination between different modes of exercise may be more effective than aerobic exercise alone.

Mechanisms underlying TNFα-induced enhancement of force generation in airway smooth muscle.

Airway diseases such as asthma are triggered by inflammation and mediated by proinflammatory cytokines such as tumor necrosis factor alpha (TNFα). Our goal was to systematically examine the potential mechanisms underlying the effect of TNFα on airway smooth muscle (ASM) contractility. Porcine ASM strips were incubated for 24 h with and without TNFα. Exposure to TNFα increased maximum ASM force in response to acetylcholine (Ach), with an increase in ACh sensitivity (hyperreactivity), as reflected by a leftward shift in the dose–response curve (EC50). At the EC50, the [Ca2+]cyt response to ACh was similar between TNFα and control ASM, while force increased; thus, Ca2+ sensitivity appeared to increase. Exposure to TNFα increased the basal level of regulatory myosin light chain (rMLC) phosphorylation in ASM; however, the ACh‐dependent increase in rMLC phosphorylation was blunted by TNFα with no difference in the extent of rMLC phosphorylation at the EC50 ACh concentration. In TNFα‐treated ASM, total actin and myosin heavy chain concentrations increased. TNFα exposure also enhanced the ACh‐dependent polymerization of G‐ to F‐actin. The results of this study confirm TNFα‐induced hyperreactivity to ACh in porcine ASM. We conclude that the TNFα‐induced increase in ASM force, cannot be attributed to an enhanced [Ca2+]cyt response or to an increase in rMLC phosphorylation. Instead, TNFα increases Ca2+ sensitivity of ASM force generation due to increased contractile protein content (greater number of contractile units) and enhanced cytoskeletal remodeling (actin polymerization) resulting in increased tethering of contractile elements to the cortical cytoskeleton and force translation to the extracellular matrix.

Chronic Alcohol Consumption, but not Acute Intoxication, Decreases In Vitro Skeletal Muscle Contractile Function.

Skeletal muscle myopathy accompanying chronic alcohol misuse results in part from a decrease in protein synthesis typically observed in type II-rich muscles that leads to muscle weakness. However, there is a paucity of studies investigating whether the alcohol-induced weakness is intrinsic to the muscle or results primarily from the loss of muscle mass. The present study determines whether acute alcohol (ethanol) intoxication or chronic alcohol consumption decreases the intrinsic contractile function of muscle. Adult male mice were randomly assigned to the chronic alcohol group or given a binge dose of alcohol, and contractile characteristics of the extensor digitorum longus (EDL) were determined in vitro. The weight and physiological cross-sectional area (PCSA) of the EDL were decreased in alcohol-fed mice. Maximum twitch and tetanic tension were also reduced, and there was a downward shift of the absolute force-frequency curve in alcohol-fed mice. However, no alcohol-induced changes were noted when these contractile parameters were normalized for the lower PCSA. Alcohol-fed mice demonstrated greater fatigability, and alcohol-induced decreases in postfatigue specific twitch and tetanic force were independent of a decreased PCSA. Furthermore, postfatigue recovery of muscle force over time was reduced. While alcohol did not alter the content of high-energy phosphates or oxidative phosphorylation complexes I-V, it did reduce myosin heavy chain and troponin-T content. In contrast, contractile properties were not altered when examined 2hours after binge alcohol. These data demonstrate chronic alcohol consumption decreases isometric and tetanic tension development due to a reduction in muscle CSA, whereas the increased fatigability observed was independent of muscle mass. As none of the functional changes were produced by acute alcohol, which produced higher blood alcohol levels than chronic ingestion, our data suggest defects in intrinsic muscle contractility require sustained intake and appear independent of defects in basal energy production.

Effect of chicken breast on the physicochemical properties of unwashed sturgeon surimi gels

This research investigated the effect of chicken breast (CB) at various concentrations (10–50%) on the physicochemical properties of unwashed sturgeon surimi gels. When rinsed surimi gel was used as a control, adding 40% CB produced the maximum breaking force and gel strength, with increases of 60% and 58%, respectively, while there was no marked difference in whiteness among all samples. CB addition could increase the binding water in gel network because of the higher water holding capacity and water proportion of T21 and T22 in low-field nuclear magnetic resonance as well as a more uniform and denser network as shown by SEC. The increase in surface hydrophobicity indicated that hydrophobic interactions are important for the formation of surimi gel. The incorporation of CB significantly increased the content of myosin heavy chains and actin as indicated by the SDS-PAGE results. Furthermore, the values of hardness, springiness and chewiness significantly increased by 84.54%, 76.71%, 67.90% and 107.99% with the addition of 40% CB, and significantly higher scores for sensory evaluation items were observed. Therefore, CB addition has the potential to strengthen the gel properties of unwashed sturgeon surimi and simplify the surimi processing procedure.

Histone deacetylase activity mediates thermal plasticity in zebrafish (Danio rerio)

Regulatory mechanisms underlying thermal plasticity determine its evolution and potential to confer resilience to climate change. Here we show that class I and II histone deacetylases (HDAC) mediated thermal plasticity globally by shifting metabolomic profiles of cold acclimated zebrafish (Danio rerio) away from warm acclimated animals. HDAC activity promoted swimming performance, but reduced slow and fast myosin heavy chain content in cardiac and skeletal muscle. HDAC increased sarco-endoplasmic reticulum ATPase activity in cold-acclimated fish but not in warm-acclimated animals, and it promoted cardiac function (heart rate and relative stroke volume) in cold but not in warm-acclimated animals. HDAC are an evolutionarily ancient group of proteins, and our data show that they mediate the capacity for thermal plasticity, although the actual manifestation of plasticity is likely to be determined by interactions with other regulators such as AMP-activated protein kinase and thyroid hormone.

Effect of soluble soybean polysaccharides on freeze-denaturation and structure of myofibrillar protein of bighead carp surimi with liquid nitrogen freezing

This paper investigated the synergistic effect of 3% soluble soybean polysaccharides (SSPS) and liquid nitrogen freezing (−80 °C) on the freezing process and protein denaturation of bighead carp surimi. Freezing curve showed that liquid nitrogen freezing could significantly minimize the elapsed time of maximum-ice-crystal formation zone. Both liquid nitrogen freezing and SSPS were useful in preventing protein denaturation of surimi during 12-week frozen storage. Protein denaturation results indicated that SSPS-LNfreezing surimi11SSPS-added surimi frozen by liquid nitrogen freezing had the highest protein solubility, Ca2+-ATPase activity and total sulfhydryl content. SDS-PAGE indicated that SSPS and liquid nitrogen freezing could effectively inhibit the decrease of myosin heavy chain concentration after 12 weeks of frozen storage. Raman spectra showed that tryptophan and tyrosine were exposed to polar microenvironment, the ɑ-helix and β-sheet turned into random coil and β-turn, and the conformation of disulfide bond changed from trans-gauche-trans (t-g-t) to gauche-gauche-trans (g-g-t). Either SSPS or liquid nitrogen freezing could mitigate these changes during frozen storage and a synergistic effect emerged on preventing myofibrillar protein denaturation and protein structure change. The combination of SSPS with liquid nitrogen freezing could be applied to freeze bighead carp surimi.

Resveratrol prevents sarcopenic obesity by reversing mitochondrial dysfunction and oxidative stress via the PKA/LKB1/AMPK pathway

Background: The concept of sarcopenic obesity refers to low muscle mass coupled with high adiposity in older adults. Sarcopenic obesity is a new medical challenge that imposes tremendous financial burdens on healthcare authorities worldwide. This study investigated the effects of resveratrol on high-fat diet-induced sarcopenic obesity in aged rats and palmitate acid-induced muscle atrophy in L6 myotubes and explored the underlying mechanisms.Results: In vivo, resveratrol prevented muscle loss and myofiber size decrease, improved grip strength and abolished excessive fat accumulation. In vitro, resveratrol inhibited the palmitate acid-mediated reductions in myosin heavy chain content and myotube diameter. Moreover, resveratrol ameliorated mitochondrial dysfunction and oxidative stress, leading to an improvement in protein metabolism and contributing to the prevention of muscle atrophy. Furthermore, the protective effects of resveratrol on mitochondrial function, oxidative stress and muscle atrophy were abolished by PKA siRNA, LKB1 siRNA and AMPK siRNA transfection in vitro.Conclusions: Resveratrol prevented high-fat diet-induced muscle atrophy in aged rats by reversing mitochondrial dysfunction and oxidative stress, which was partially mediated by the PKA/LKB1/AMPK pathway. These findings indicate that resveratrol might have potential uses for the prevention and treatment of sarcopenic obesity.

Localization of trypsin-like protease in postmortem tissue of white shrimp (Litopenaeus vannamei) and its effect in muscle softening

Fluorescein-isothiocyanate (FITC) labeled trypsin-like protease was prepared and injected into the hepatopancreas of white shrimp. Different segments of the injected shrimp were analyzed with a fluorescence microscope during storage. FITC-trypsin-like protease can be detected in the first segment of shrimp muscle at day 4, while it cannot be observed in the second segment until day 6. The results showed that trypsin-like protease can migrate from hepatopancreas to the tail portion. Texture profile analysis showed that soybean trypsin inhibitor retarded the softening of the shrimp muscle. The rheological results revealed that the content of myosin heavy chain (MHC) in shrimp muscle was decreased with the extended storage time. Proteomics analysis displayed that trypsin-like protease accelerated the metabolism of postmortem muscle. It can be concluded that trypsin-like protease migrated from the hepatopancreas to the muscle tissue, degraded myofibrillar protein, deteriorated the muscle texture, and eventually leaded to the softening of white shrimp.

Extraordinary fast-twitch fiber abundance in elite weightlifters.

Human skeletal muscle fibers exist across a continuum of slow → fast-twitch. The amount of each fiber type (FT) influences muscle performance but remains largely unexplored in elite athletes, particularly from strength/power sports. To address this nescience, vastus lateralis (VL) biopsies were performed on World/Olympic (female, n = 6, “WCF”) and National-caliber (female, n = 9, “NCF”; and male, n = 6, “NCM”) American weightlifters. Participant accolades included 3 Olympic Games, 19 World Championships, 25 National records, and >170 National/International medals. Samples were analyzed for myosin heavy chain (MHC) content via SDS-PAGE using two distinct techniques: single fiber (SF) distribution (%) and homogenate (HG) composition. The main finding was that these athletes displayed the highest pure MHC IIa concentrations ever reported in healthy VL (23±9% I, 5±3% I/IIa, 67±13% IIa, and 6±10% IIa/IIx), with WCF expressing a notable 71±17% (NCF = 67±8%, NCM = 63±16%). No pure MHC IIx were found with SF. Secondary analysis revealed the heavyweights accounted for 91% of the MHC IIa/IIx fibers, which caused a correlation between this FT and body mass. Additionally, when compared to SF, HG overestimated MHC I (23±9 vs. 31±9%) and IIx (0±0 vs. 3±6%) by misclassifying I/IIa fibers as I and IIa/IIx fibers as IIx, highlighting the limitation of HG as a measure of isoform distribution. These results collectively suggest that athlete caliber (World vs. National) and/or years competing in the sport determine FT% more than sex, particularly for MHC IIa. The extreme fast-twitch myofiber abundance likely explains how elite weightlifters generate high forces in rapid time-frames.