Percentage Of Myosin Heavy Chain Research Articles

Effects of oxidation on the physicochemical properties and degradation of mutton myofibrillar proteins

Tenderness affects mutton quality and price, and the degradation of myofibrillar protein (MP) is critical to improve tenderness. We investigated the oxidative modification of mutton MP by hydroxyl radicals (OH) and the effects of this modification on the proteolysis of MP by µ-calpain. As the H2 O2 concentrations increased, the carbonyl and dityrosine contents and the surface hydrophobicity of MP all display an increasing trend, whereas the total sulfhydryl and intrinsic fluorescence intensity of MP declines significantly. SDS-PAGE electrophoresis indicates that disulfide bonds and other covalent bonds led to protein cross-linking and aggregation. After adding µ-calpain, with increasing oxidation, the degradation percentage of myosin heavy chain (MHC) increases considerably and actin degradation is promoted, while the proteolysis of troponin-T and desmin is inhibited. These data suggest that·OH can change MP physicochemical properties and its susceptibility to µ-calpain. Future investigations will focus on the effect of oxidation on the degradation of MP by other proteases, such as cathepsins and caspase and the effect of oxidation on these enzymes. PRACTICAL APPLICATION: The calpain system, particularly µ-calpain, plays a pivotal role in postmortem tenderization of meat. Protein oxidative modifications influence meat tenderness mainly by regulating proteolysis. An investigation of the effect of oxidation on the proteolytic susceptibility of MP to degradation by µ-calpain allows for the monitoring of the association between protein oxidation and meat tenderness.

Meat quality, post-mortem proteolytic enzymes, and myosin heavy chain isoforms of different Thai native cattle muscles.

ObjectiveThis study investigated the meat quality characteristics, endogenous proteolytic enzymes, collagen content, and myosin heavy chain (MyHC) isoforms of different muscles of Thai native cattle (TNC).MethodsInfraspinatus (IF), Longissimus thoracis (LT), and Supraspinatus (SS) muscles were obtained from two TNC breeds, Kho-Lan (KL, n = 7) and Kho-Isaan (KI, n = 7). The muscle and meat characteristics of TNC breeds and their relationship with MyHC expression were examined.ResultsThree MyHC isoforms namely MyHC I, MyHC IIa, and MyHC IIx were detected in the muscles. The KL had higher (p<0.05) MyHC IIx than the KI. The IF muscle had higher (p<0.05) MyHC I compared to other muscles. The LT muscle had the least MyHC I. The LT had higher (p<0.05) MyHC IIx than the IF and SS muscles. The IF presented the least MyHC IIx. The KL had higher (p<0.05) lightness and moisture content and lower crude protein, redness, cooking loss, shear force, and calpastatin than the KI. The glycogen, total collagen, soluble collagen, crude protein, ash contents, and troponin T degradation product of IF and SS were lower (p<0.05) than that of LT. Ether extract in LT was lower (p<0.05) than that of IF and SS. The percentage of MyHC I, MyHC IIa, and MyHC IIx were significantly correlated with muscle and meat characteristics of TNC.ConclusionThese results suggest that the differences in the MyHC isoforms may partly account for the variation in meat quality between breeds and among muscles of TNC.

Myosin heavy chain isoforms expression, calpain system and quality characteristics of different muscles in goats

Myosin heavy chain (MHC) isoforms in goat muscles and their possible relationships with meat quality have not been fully elucidated. This study characterized the MHC isoforms in different caprine muscles using sodium dodecyl sulphate glycerol gel electrophoresis (SDS-GGE). The relationships between MHC isoforms, calpain systems and meat quality characteristics of different muscles in goats were examined. Four muscles, namely infraspinatus (IF), longissimus dorsi (LD), psoas major (PM) and supraspinatus (SS) were obtained from ten Boer crossbred bucks (7–10 months old; 26.5 ± 3.5 kg, BW). The percentages of MHC I, MHC IIa and MHC IIx in SS, IF, PM and LD were 47.2, 38.3, 32.1, 11.9; 28.0, 42.1, 33.0, 36.4; and 24.8, 19.6, 34.9 and 51.7, respectively. IF and SS had higher levels of calpastatin, total collagen and insoluble collagen contents than did PM and LD. PM had longer sarcomere length than did other muscles. LD had higher collagen solubility, troponin-T degradation products and glycogen content than did other muscles. These results infer that variable fiber-type composition could account partially for the differences in the physicochemical properties of goat muscles.

Effects of Birth Weight and Postnatal Nutritional Restriction on Skeletal Muscle Development, Myofiber Maturation, and Metabolic Status of Early-Weaned Piglets.

Simple SummaryLight weaning weight piglets have slow post-weaning growth performance and require longer days to reach slaughter weight. Birth weight and early postnatal nutrient intake are the main factors contributing to light weaning weight. Our results suggested that intrauterine growth-retarded (IUGR) piglets fed adequately during the suckling period do not catch up with the same muscle growth and development compared with normal birth weight piglets. Postnatal early nutritional restriction resulted in impaired skeletal muscle growth and delayed myofiber maturation of the piglets.Piglets with light weaning weight commonly have a slow post-weaning growth rate due to impaired skeletal muscle development. Therefore, the present study aimed to investigate the impact of birth weight and nutrient intake on skeletal muscle development, myofiber maturation, and metabolic status of early-weaned piglets. Twelve pairs of normal birth weight and intrauterine growth-retarded (IUGR) piglets (seven days old) were randomly assigned to receive adequate nutrient intake or restricted nutrient intake for 21 days. Serum and muscle samples were collected for further analysis. The results indicated that muscle weight, cross-sectional areas, and muscular glycogen were lower (p < 0.05) in both IUGR and restricted fed piglets. Nutrient restriction decreased the contents of RNA, the RNA to DNA ratio, and the percentages of myosin heavy chain (MyHC) IIx (p < 0.05), whereas increased the activity of β-hydroxy-acyl-CoA-dehydrogenase (HAD), the ratio of HAD to citrate synthase, as well as the percentages of MyHC I (p < 0.05). In addition, nutrient restriction significantly decreased muscular glycogen, mRNA levels of fatty acid transport protein 1, cationic amino acid transporter 1, and glucose transporter 4 in IUGR piglets compared with the other groups (p < 0.05). The results of the present study showed that IUGR impaired skeletal muscle growth and disturbed the hormone and mRNA expression of genes related to energy metabolism, which led to a more severe energy deficit when receiving postnatal nutritional restriction. Postnatal nutritional restriction resulted in delayed myofiber maturation of the piglets, which may be associated with the transformation of MyHC isoform and the change of metabolic status.

Nutritional effects pre-weaning on growth performance, carcass traits and meat quality of pigs

The objective of the present study was to investigate the effect of nutritional restriction during the suckling period on growth performance, carcass traits and meat quality of fattening pigs. A one-way experimental design was used. In total, 24 male pigs of normal birthweight (1.54 ± 0.05 kg) were randomly allocated at 7 days of age to three groups: control, fed ad libitum; 30% nutritional restriction (Re30%); and 60% nutritional restriction (Re60%). The Re30% and Re60% groups showed decreased average daily gain, average daily feed intake and feed conversion ratio from Day 7 to Day 28. After Day 28, differences in these parameters were observed only in the Re60% group relative to the control. With regard to hormone levels, the Re60% group showed decreased serum concentration of insulin-like growth factor-1 at Day 28 and increased serum concentration of growth hormone at Day 147. Furthermore, the Re60% group had decreased carcass weight, ham weight and dressing percentage, and increased carcass lean percentage relative to the control, as well as lower cross-sectional area and myofibre diameter of muscle. The Re60% group had lower levels of myosin heavy chain (MyHC) IIx and MyHC IIb mRNA and a higher percentage of MyHC I and MyHC IIa mRNA in longissimus dorsi muscle than the Re30% group. In conclusion, nutritional restriction during the suckling period decreased weaning weight, with post-weaning growth performance, carcass traits and myofibre type affected in the Re60% group rather than Re30% group.

The effect of different intensity exercise on skeletal muscle fiber MHC subtype transformation and CaN/NFATc1 signaling pathways

To study the effect of different intensity exercise on skeletal muscle fiber myosin heavy chain(MHC) subtype transformation and CaN/NFATc1 signaling pathways. Twenty-four Male SD rats (2-month old) were randomly divided into normal control group (NC), moderate intensity exercise group (ME, grade 5°, speed 18 m/min), heavy intensity exercise group (HE, grade 10°, 26.8 m/min). The rats in exercise groups were treated with treadmill training for eight weeks. The type I and type Ⅱ muscle fibers were determined by ATPase staining method. MHC subtype was separated by SDS-PAGE. The activity of CaN was determined by colorimetric method. The content of NFATc1 protein in skeletal muscle was detected by immune imprinting technology. ①Skeletal muscle fiber density changes:the type I and Ⅱ fiber number density of quadriceps in ME group were increased significantly (P<0.05), but in HE group, only the type Ⅱ fiber surface density was increased significantly (P<0.05). The type I fiber number density of soleus in ME and HE group was increased significantly (P<0.05). ②The changes of fibers MHC subtype percentage in skeletal muscle:the percentages of MHC I and type Ⅱa of quadriceps in ME group were increased (P<0.05), while the percentage of MHC Ⅱb was decrease (P<0.05). The percentage of MHC I in soleus was increased, while the percentages of MHCⅡa and Ⅱb were decreased. ③The activity of CaN and the content of NFATc1 protein in ME group were increased significantly (P<0.05). The heavy and moderate intensity exercise may induce skeletal muscle MHC type transforming from fast to slow. At the same time, the activity of CaN and the expression of NFATc1 protein are increased accompanying the changes of skeletal muscle fibers subtype.

HIF-1alpha Deficiency Attenuates the Cardiomyogenesis of Mouse Embryonic Stem Cells.

Cardiac cell formation, cardiomyogenesis, is critically dependent on oxygen availability. It is known that hypoxia, a reduced oxygen level, modulates the in vitro differentiation of pluripotent cells into cardiomyocytes via hypoxia inducible factor-1alpha (HIF-1α)-dependent mechanisms. However, the direct impact of HIF-1α deficiency on the formation and maturation of cardiac-like cells derived from mouse embryonic stem cells (mESC) in vitro remains to be elucidated. In the present study, we demonstrated that HIF-1α deficiency significantly altered the quality and quantity of mESC-derived cardiomyocytes. It was accompanied with lower mRNA and protein levels of cardiac cell specific markers (myosin heavy chains 6 and 7) and with a decreasing percentage of myosin heavy chain α and β, and cardiac troponin T-positive cells. As to structural aspects of the differentiated cardiomyocytes, the localization of contractile proteins (cardiac troponin T, myosin heavy chain α and β) and the organization of myofibrils were also different. Simultaneously, HIF-1α deficiency was associated with a lower percentage of beating embryoid bodies. Interestingly, an observed alteration in the in vitro differentiation scheme of HIF-1α deficient cells was accompanied with significantly lower expression of the endodermal marker (hepatic nuclear factor 4 alpha). These findings thus suggest that HIF-1α deficiency attenuates spontaneous cardiomyogenesis through the negative regulation of endoderm development in mESC differentiating in vitro.

Effects of aging on mitochondrial function in skeletal muscle of American American Quarter Horses.

Skeletal muscle function, aerobic capacity, and mitochondrial (Mt) function have been found to decline with age in humans and rodents. However, not much is known about age-related changes in Mt function in equine skeletal muscle. Here, we compared fiber-type composition and Mt function in gluteus medius and triceps brachii muscle between young (age 1.8 ± 0.1 yr, n = 24) and aged (age 17-25 yr, n = 10) American Quarter Horses. The percentage of myosin heavy chain (MHC) IIX was lower in aged compared with young muscles (gluteus, P = 0.092; triceps, P = 0.012), while the percentages of MHC I (gluteus; P < 0.001) and MHC IIA (triceps; P = 0.023) were increased. Mass-specific Mt density, indicated by citrate synthase activity, was unaffected by age in gluteus, but decreased in aged triceps (P = 0.023). Cytochrome-c oxidase (COX) activity per milligram tissue and per Mt unit decreased with age in gluteus (P < 0.001 for both) and triceps (P < 0.001 and P = 0.003, respectively). Activity of 3-hydroxyacyl-CoA dehydrogenase per milligram tissue was unaffected by age, but increased per Mt unit in aged gluteus and triceps (P = 0.023 and P < 0.001, respectively). Mt respiration of permeabilized muscle fibers per milligram tissue was unaffected by age in both muscles. Main effects of age appeared when respiration was normalized to Mt content, with increases in LEAK, oxidative phosphorylation capacity, and electron transport system capacity (P = 0.038, P = 0.045, and P = 0.007, respectively), independent of muscle. In conclusion, equine skeletal muscle aging was accompanied by a shift in fiber-type composition, decrease in Mt density and COX activity, but preserved Mt respiratory function.

Myosin heavy chain changes in heart failure‐rat diaphragm muscle are not related to myogenic regulatory factors expression

ObjectiveIn this study we tested the hypothesis that diaphragm myosin heavy chain (MyHC) isoform changes are related to alterations of myogenic regulatory factors (MRF) expression in chronic heart failure.MethodsWe studied Sham (n=10) and infarcted rats with heart failure (MI/HF, n=10). Cardiac structures and ventricular function were assessed by echocardiogram. MyHC isoforms were analyzed by electrophoresis. MRF myogenin, MyoD, and MRF4 gene expression was evaluated by real time RT‐PCR and protein expression was analyzed by Western‐blot. Statistical analysis was performed by Student's t test and Pearson correlation.ResultsAll MI/HF rats had pulmonary congestion and right ventricular hypertrophy. In echocardiographic evaluation, MI/HF presented left cardiac chambers dilation and left ventricular systolic and diastolic dysfunction. The percentage of MyHC I isoform was higher and IIb isoform was lower in MI/HF. Left atrial diameter‐to‐body weight ratio positively correlated with MyHC I and negatively correlated with MyHC IIb isoform percentage. No differences were observed in MRF gene and protein expressions between groups.ConclusionMRF expression does not modulate diaphragm MyHC isoforms changes in rats with chronic heart failure. Diaphragm MyHC changes are related to ventricular dysfunction severity. Financial support: Fapesp.

Divergent effects of GLP-1 analogs exendin-4 and exendin-9 on the expression of myosin heavy chain isoforms in C2C12 myotubes

Exendin 1-39 amide (Ex-4) and its truncated form exendin 9-39 amide (Ex-9) are peptides of non-mammalian nature, which act as an agonist and antagonist, respectively, of the glucagon-like peptide-1 (GLP-1) receptor in mammals. GLP-1 is an intestinal peptide that plays an important role in the regulation of glucose metabolism and glucose uptake in skeletal muscle; however, the effects of its two analogs (Ex-4 and Ex-9) on myofiber properties are still unclear. Here, we report the effects of Ex-4 and Ex-9 alone or in combination on the myosin heavy chain (MyHC) type composition and the glucose uptake capacity in differentiated C2C12 myotubes. Neither Ex-4 nor Ex-9 altered basal glucose uptake, whereas Ex-9 significantly increased insulin-stimulated glucose uptake, suggesting enhanced insulin sensitivity. The mRNA expression of MyHC I and 2A as well as the percentage of MyHC I protein was remarkably increased in Ex-9-treated myotubes. In contrast, Ex-4, alone or in combination with Ex-9, caused a significant reduction in MyHC 2A mRNA expression and the percentage of MyHC I protein. Consistent with the MyHC type switching peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α expression in myotubes was remarkably increased by Ex-9 yet was significantly inhibited by Ex-4. In addition, intracellular concentrations of free Ca 2+ were increased in all treatment groups, but only Ex-9-treated myotubes showed higher calcineurin A protein content. Taken together, our data suggest that Ex-9 promotes oxidative differentiation in myotubes to improve cell insulin sensitivity, probably through calcineurin and PGC-1α mediated pathways.

Correlation of average muscle fiber conduction velocity measured during cycling exercise with myosin heavy chain composition, lactate threshold, and VO 2max

The aim of the study was to investigate the correlation between myosin heavy chain (MHC) composition, lactate threshold (LT), maximal oxygen uptake VO 2max, and average muscle fiber conduction velocity (MFCV) measured from surface electromyographic (EMG) signals during cycling exercise. Ten healthy male subjects participated in the study. MHC isoforms were identified from a sample of the vastus lateralis muscle and characterized as type I, IIA, and IIX. At least three days after a measure of LT and VO 2max, the subjects performed a 2-min cycling exercise at 90 revolutions per minute and power output corresponding to LT, during which surface EMG signals were recorded from the vastus lateralis muscle with an adhesive electrode array. MFCV and instantaneous mean power spectral frequency of the surface EMG were estimated at the maximal instantaneous knee angular speed. Output power corresponding to LT and VO 2max were correlated with percentage of MHC I ( R 2 = 0.77; and 0.42, respectively; P < 0.05). MFCV was positively correlated with percentage of MHC I, power corresponding to LT and to VO 2max ( R 2 = 0.84; 0.74; 0.53, respectively; P < 0.05). Instantaneous mean power spectral frequency was not correlated with any of these variables or with MFCV, thus questioning the use of surface EMG spectral analysis for indirect estimation of MFCV in dynamic contractions.

Myosin Heavy Chain Isoform Expression and In Vivo Isometric Performance: A Regression Model

This investigation estimated the amount of variance in voluntary in vivo muscle performance that can be explained by relative myosin heavy chain (MHC) isoform expression. The role of the relative expression of these proteins in relation to in vitro force and velocity performance is well understood, but the in vivo model is less clear. Twenty-two men and women (mean +/- SD age, 27 +/- 6 years) performed isometric knee extensor actions in which peak force and rate of force development (RFD) were measured. The results of regression analysis showed that the inclusion of MHC IIb explained a significant (19.9%, p < 0.05) amount of variance in relative peak force (adjusted for muscle mass) and 14.1% of the variance in the first half of the rise phase of the force-time curve (RFD(0-50%)) (p < 0.1). The addition of MHC I into this model explained a significant (p < 0.05) amount of variance above that accounted for by MHC IIb in RFD (45.4%), RFD(0-50%) (50.8%), and RFD(50-100%) (second half of the rise phase of the force-time curve) (37.4%). Since the percentage of MHC IIb is reduced rather quickly with training, these data suggest that peak force may also be affected quickly by training. The percentage of MHC I has a longer course for change with training; therefore, it may be inferred that the greatest changes in RFD variables will likely occur during a longer course.

Effect of muscular hypertrophy on physico-chemical, biochemical and texture traits of meat from yearling bulls

The effect of the presence of the double-muscling gene either homozygous ( mh/mh) or heterozygous ( mh/+) on the physico-chemical, biochemical and texture traits of Longissimus thoracis muscle of yearling bulls of the Asturiana de los Valles (AV) breed was studied. Meat of mh/mh bulls had lower amount of intramuscular fat ( p<0.001) and also lower total ( p<0.01) and insoluble collagen ( p<0.05), although the double-muscling genotype did not affect collagen solubility. Homozygous animals had lower pigment content ( p<0.05) and a lighter meat, showing lower water holding capacity, estimated as expressible juice under pressure ( p<0.001). Genotype affected significantly the metabolic traits of muscle, with mh/mh animals having higher muscle glycolytic metabolism, assessed by a higher ( p<0.001) lactate dehydrogenase (LDH) activity and lower ( p<0.001) oxidative activity of the isocitrate dehydrogenase (ICDH). The percentage of myosin heavy chain I in muscle was lower, although not significantly, for mh/mh bulls compared to mh/+ bulls. Texture measurements performed on raw material showed that meat of mh/mh bulls had lower resistance to total and 80% compression, which means lower background or collagen toughness. However, there were no differences between genotypes on shear force of cooked meat. Therefore, the physico-chemical, biochemical and texture traits of meat from mh/mh and mh/+ bull are in general significantly different, which could affect the sensorial quality of meat and hence the consumer acceptance.

Effect of frozen storage of hake, sardine and mixed minces on natural actomyosin extracted in salt solutions

AbstractNatural actomyosin extracted in salt solutions from mixtures of hake and sardine minces (3:1; 1:1 and 1:3 w/w) stored frozen for up to 1 year differed in the amount extracted and in the characteristics of the extracts. In the mixed minces the amount of natural actomyosin extracted decreased during frozen storage at a higher rate than that theoretically corresponding to the amount of hake in the mixes. With increasing storage time and proportion of sardine a lower percentage of myosin heavy chain and actin was observed by electrophoresis. An increased size of aggregates was also observed by electrophoresis and transmission electron microscopy. The stability of emulsions was enhanced when aggregates appeared in the extracts. The decrease in the amount of natural actomyosin extracted does not explain the changes observed in the texture of the minces during frozen storage. This may indicate that the size of the aggregates unextractable in salt solutions, independently of the type of bonds that bind the proteins in the aggregates, plays an important role in the textural changes observed. Copyright © 2003 Society of Chemical Industry

Changes in Myofibrillar Protein Composition of Human Diaphragm Elicited by Congestive Heart Failure

We describe the changes in proportions of myofibrillar proteins elicited by chronic congestive heart failure in the costal diaphragm (DIA) of humans using one and two-dimensional electrophoretic techniques. Three myosin heavy chain (MHC) isoforms were found in the DIA from control subjects: slow MHC I (43± S.E.2%), fast MHC IIa (41±2%) and fast MHC IIb (17±1%). In heart failure DIA, the percentage of MHC I was increased to 57±2%, while that of MHC IIb was decreased to 8±2 ( P<0.001 for both cases). Similarly, this DIA had higher molar ratios (%) of the slow myosin light chain isoforms (i.e. 1sa, 1sb, and 2s), and lower molar ratios of the fast isoforms (i.e. 1f, 2f, and 3f ) than control DIA. Heart failure DIA also contained lower proportions of both α-tropomyosin and fast isoforms of troponin-T, I and C than control DIA. These results indicate that heart failure elicits fast-to-slow transformations of both myosin and regulatory proteins of human costal DIA. These changes can be viewed as an increase in slow-twitch characteristics of the DIA and differ from the adaptations elicited by heart failure in limb muscles.

Myosin heavy chain isoform changes in rat diaphragm are induced by endurance training.

After rats were chronically exercised by endurance swimming, an augmentation of succinic dehydrogenase (SDH) activity in the diaphragm and the EDL muscle was observed. In addition, endurance training induced a decrease in the percentage of myosin heavy chain (MHC) IIb in the diaphragm, and a decrease in the percentage of HCIIb concomitant with an increase in the percentage of HCIId in the EDL muscle. These results indicate that endurance training induced not only an increase of the oxidative capacity but also an alteration in the expression of an MHC phenotype in the diaphragm and skeletal muscle.