Muscle Fiber Composition Research Articles

Reference gene selection and myosin heavy chain (MyHC) isoform expression in muscle tissues of domestic yak (Bos grunniens)

Domestic yak (Bos grunniens) is the most crucial livestock in the Qinghai-Tibetan Plateau, providing meat and other necessities for local people. The skeletal muscle of adult livestock is composed of muscle fibers, and fiber composition in muscle has influence on meat qualities, such as tenderness, pH, and color. Real-time quantitative polymerase chain reaction (RT-qPCR) is a powerful tool to evaluate the gene expression of muscle fiber, but the normalization of the data depends on the stability of expressed reference genes. Unfortunately, there is no consensus for an ideal reference gene for data normalization in muscle tissues of yak. In this study, we aimed to assess the stability of 14 commonly used candidate reference genes by using five algorithms (GeNorm, NormFinder, BestKeeper, Delat Ct and Refinder). Our results suggested UXT and PRL13A were the most stable reference genes, while the most commonly used reference gene, GAPDH, was most variably expressed across different muscle tissues. We also found that the extensor digitorum lateralis (EDL), trapezius pars thoracica (TPT), and psoas major (PM) muscle had the higher content of type I muscle fibers and the lowest content of type IIB muscle fibers, while gluteobiceps (GB) muscle had the highest content of type IIB muscle fibers. Our study provides the suitable reference genes for accurate analysis of yak muscle fiber composition.

Postnatal development of skeletal muscle in pigs with intrauterine growth restriction: morphofunctional phenotype and molecular mechanisms.

Intrauterine growth restriction (IUGR) is a serious condition which impairs the achievement of the fetus' full growth potential and occurs in a natural and severe manner in pigs as a result of placental insufficiency. Reduced skeletal muscle mass in the fetus with IUGR persists into adulthood and may contribute to increased metabolic disease risk. To investigate skeletal muscle postnatal development, histomorphometrical patterns of the semitendinosus muscle, myosin heavy chain (MyHC; embryonic I, IIA, IIB and IIX isoforms) fiber composition and the relative expression of genes related to myogenesis, adipogenesis and growth during three specific periods: postnatal myogenesis (newborn to 100days old), hypertrophy (100-150days old), and postnatal development (newborn to 150days old) were evaluated in female pigs with IUGR and normal birth weight (NW) female littermates. NW females presented higher body weights compared to their IUGR counterparts at all ages evaluated (P<0.05). Moreover, growth restriction in utero affected the semitendinosus muscle weight, muscle fiber diameter, and muscle cross-sectional area, which were smaller in IUGR pigs at birth (P<0.05). Notwithstanding the effects on muscle morphology, IUGR also affected muscle fiber composition, as the percentage of MyHC-I myofibers was higher at birth (P<0.05), and, in 150-day-old gilts, a lower percentage of MyHC-IIX isoform (P<0.05) and the presence of embryonic MyHC isoform were also observed. Regarding the pattern of gene expression in both the postnatal myogenesis and postnatal development periods, IUGR led to the downregulation of myogenic factors, which delayed skeletal muscle myogenesis (PAX7, MYOD, MYOG, MYF5 and DES). Altogether, growth restriction in utero affects muscle fiber number and size at birth and muscle fiber composition through the downregulation of myogenic factors, which determines the individual´s postnatal growth rate. This fact, associated with delayed myofiber development in growth-restricted animals, may affect meat quality characteristics in animal production. Hence, knowledge of the morphofunctional phenotype of the skeletal muscle throughout postnatal development in individuals with IUGR, and the mechanism that governs it, may provide a better understanding of the mechanisms that limit postnatal muscle growth, and help the establishment of potential strategies to improve muscle development and prevent the onset of later-life metabolic diseases.

Effects of inhaled fluticasone propionate on extrinsic tongue muscles in rats.

Obstructive sleep apnea (OSA) is more common in patients with asthma, and inhaled corticosteroids may contribute to OSA pathogenesis in these patients. This study tested the effects of orally inhaled fluticasone propionate (FP) on extrinsic tongue muscles. Unanesthetized rats were treated with FP or placebo for 28 days. On day 29, tongue retrusive and protrusive functions were tested via hypoglossal nerve stimulation under a state of anesthesia, followed by genioglossus (GG), styloglossus (SG) and hyoglossus (HG) muscle extraction, after euthanasia, for histology [myosin heavy chain (MHC) fibers and laminin content reflecting extracellular matrix (ECM)]. On protrusive testing, FP increased percent maximum tetanic force at 40 Hz (P = 0.03 vs. placebo) and endurance index (P = 0.029 vs. placebo). On retrusive testing, FP increased maximum twitch (P = 0.026 vs. placebo) and tetanic forces (P = 0.02 vs. placebo) with no effect on endurance index. On histology, FP increased GG cross-sectional area of MHC type IIa (P = 0.036 vs. placebo) and tended to increase type IIb (P = 0.057 vs. placebo) fibers and HG MHC IIx fibers (P = 0.065). The FP group had significantly increased laminin-stained areas, of greatest magnitude in the HG muscle. FP affects tongue protrusive and retrusive functions differently, concurrent with a shift in MHC fibers and increased ECM accumulation. These differential alterations may destabilize the tongue's "muscle hydrostat" during sleep and promote collapse.NEW & NOTEWORTHY The effects of inhaled corticosteroid on upper airway may contribute to OSA pathogenesis in asthma. In this study, we tested the effects of orally inhaled fluticasone propionate on tongue protrusive and retrusive functions and on tongue extrinsic muscle fiber composition and molecular properties. We found that fluticasone treatment: 1) increased protrusive endurance and retrusive maximum twitch and tetanic force; and 2) on histology, increased cross-sectional area of myosin heavy chain (MHC) type IIa fibers and tended to increase cross-sectional area of MHC type IIb fibers in the protrusive muscle and of MHC IIx fibers in the retrusors. It also increased laminin-stained areas, across extrinsic tongue muscles, of greatest magnitude in the retrusors; and 3) reduced protein degradation and activated pathways associated with increased protein synthesis in the protrusor. These differential effects on the protrusors and retrusors may destabilize the tongue's "muscle hydrostat" properties during sleep and promote collapse.

Heat-Killed Bifidobacterium breve B-3 Enhances Muscle Functions: Possible Involvement of Increases in Muscle Mass and Mitochondrial Biogenesis.

A previous clinical study on pre-obesity subjects revealed that Bifidobacterium breve B-3 shows anti-obesity effects and possibly increases muscle mass. Here, we investigated the effects of B-3 on muscle function, such as muscle strength and metabolism, and some signaling pathways in skeletal muscle. Male rodents were orally administered live B-3 (B-3L) or heat-killed B-3 (B-3HK) for 4 weeks. We found that administration of B-3 to rats tended to increase muscle mass and affect muscle metabolism, with stronger effects in the B-3HK group than in the B-3L group. B-3HK significantly increased muscle mass and activated Akt in the rat soleus. With regard to muscle metabolism, B-3HK significantly increased phosphorylated AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor gamma coactivator (PGC)-1α and cytochrome c oxidase (CCO) gene expression in the rat soleus, suggesting an effect on the AMPK-PGC1α-mitochondrial biogenesis pathway. Furthermore, B-3HK promoted oxidative muscle fiber composition in the gastrocnemius. We also observed a significantly higher level of murine grip strength in the B-3HK group than in the control group. These findings suggest the potential of heat-killed B-3 in promoting muscle hypertrophy and modifying metabolic functions, possibly through the Akt and AMPK pathways, respectively.

The distinct transcriptomes of fast-twitch and slow-twitch muscles in Mongolian horses

Skeletal muscle is the largest organ system in the mammalian body and plays a key role in locomotion of horses. Fast and slow muscle fibers have different abilities and functions to adapt to exercises. To investigate the RNA and miRNA expression profiles in the muscles with different muscle fiber compositions on Mongolian horses. We examined the muscle fiber type population and produced deep RNA sequencing for different parts of skeletal muscles. And chose two of them with the highest difference in fast and slow muscle fiber population (splenius and gluteus medius) for comparing the gene expression profile of slow and fast muscle fiber types. We identified a total of 275 differentially expressed genes (DEGs), and 11 differentially expressed miRNAs (DEmiRs). In addition, target gene prediction and alternative splicing analysis were also performed. Significant correlations were found between the differentially expressed gene, miRNAs, and alternative splicing events. The result indicated that differentially expressed muscle-specific genes and target genes of miRNAs might co-regulating the performance of slow and fast muscle fiber types in Mongolian horses.

Differences in Muscle Fiber Characteristics and Meat Quality by Muscle Type and Age of Korean Native Black Goat.

To investigate the relationship between muscle fiber characteristics and meat quality traits by age of Korean native black goat (KNBG), four muscles (longissimus dorsi, LD; psoas major, PM; semimembranosus, SM; gluteus medius, GM) were obtained from five adult goat (AG; 18 months old) and five young goat (YG; 9 months old). PM muscle had the highest fiber number percentage (FNP) and fiber area percentage (FAP) of type I, followed by SM, GM, and LD muscles. FNP and FAP of type IIB were significantly (p<0.001) higher in AG than those in YG. YG had higher L* values but lower b* values than AG. The highest L* and b* values were observed in LD muscle (p<0.001). Age and muscle type had detrimental (p<0.001) effect on shear force and collagen content for all muscle in AG as compared to YG. YG had significantly (p<0.001) higher myofibrillar fragmentation index (MFI) than AG for all four muscles. These results suggest that muscle fiber compositions of different muscle types of KNBG depend on age, resulting in variations of meat color, MFI, collagen content, and shear force.

Effect of Slaughter Age on Muscle Fiber Composition, Intramuscular Connective Tissue, and Tenderness of Goat Meat during Post-Mortem Time.

This study evaluated the effects of slaughter age and post-mortem time on meat quality traits, tenderness, histochemical analyses, and perimysium thickness in the longissimus thoracis (LT) muscle of the Korean native black goat (KNBG) maintained at 4 °C for up to 21 days post mortem. Samples of LT muscle were obtained from the carcasses of 24 KNBGs, including old and young goats (AG, n = 12, 18 months of age; YG, n = 12, 9 months of age), to measure all analyses during 21 days of post-mortem time. AGs had a higher percentage of type I fiber but a lower percentage of type IIA fiber than YGs (p < 0.05). AGs had higher a* value, lower released water (RW) %, and higher Warner–Bratzler shear force (WBSF) value than YGs (p < 0.05). The perimysium thickness (PMT) of AGs was also higher than that of YGs (p < 0.05). Although the PMT did not change during post-mortem period, the WBSF value of AGs was higher than that of YGs after 21 days post mortem (p < 0.05). The results imply that AGs are tougher than YGs due to their muscle fiber characteristics and thicker perimysium.

Does intrauterine crowding affect the force generating capacity and muscle composition of the piglet front limb?

In the pig, intrauterine competition (IUC) greatly affects postnatal traits, such as birth weight, but also locomotor capacities. In a previous study, our group discovered a lower motor performance in piglets with a low birth weight and low vitality (L piglets), compared to piglets with a normal birth weight and normal vitality (N piglets). In order to explain the force deficit causing this reduced motor performance, in a subsequent study, we investigated whether this deficit in L piglets was caused by a lower force generating capacity (FGC) of the extensors of the hind limb and/or a lower number of type II (fast-twitch) fibers in m. vastus lateralis. L piglets had a lower absolute FGC, but surprisingly, a higher relative FGC (to birth weight) in the hind limb, compared to N piglets. In addition, we found no differences in fiber composition of m. vastus lateralis. In the present study, we assessed whether this higher relative FGC is a common feature for front and hind limb locomotor muscles of L piglets. To that end, the physiological cross-sectional area of the main extensor muscles of the front limb was calculated from their volume and fiber length, in order to calculate both the absolute and the relative FGC. By immunohistochemical staining of m. triceps brachii caput longum, the percentage of type II (fast-contracting) fibers could be determined. Similar to the results of the hind limb, we found a smaller absolute FGC, but a larger relative FGC in the front limb of L piglets, compared to N piglets. In addition, m. triceps brachii caput longum did not have a different muscle fiber composition in L and N piglets. As such, we can conclude that IUC affects the locomotor muscles in the front and hind limb in a similar way and that the observed force deficit in L piglets cannot be explained by a different force generating capacity or a lower percentage of type II muscle fibers.

Fiber Type Composition and Rate of Force Development in Endurance- and Resistance-Trained Individuals.

Methenitis, S, Spengos, K, Zaras, N, Stasinaki, A-N, Papadimas, G, Karampatsos, G, Arnaoutis, G, and Terzis, G. Fiber type composition and rate of force development in endurance- and resistance-trained individuals. J Strength Cond Res 33(9): 2388-2397, 2019-The purpose of the study was to investigate the relationship between muscle fiber composition and the rate of force development (RFD) in well-trained individuals with different training background. Thirty-eight young men with different training background participated: 9 endurance runners, 10 power-trained individuals, 9 strength-trained individuals, and 10 sedentary individuals. They performed maximal isometric leg press for the measurement of RFD. Body composition (dual x-ray absorptiometry) and vastus lateralis fiber type composition were also evaluated. When all participants were examined as a group, moderate correlations were found between the percent of type II muscle fibers and RFD between 100 and 600 milliseconds (r = 0.321-0.497; p ≤ 0.05). The correlation coefficients were higher for the cross-sectional area (CSA) and the %CSA of type II and IIx muscle fibers (r = 0.599-0.847; p < 0.001). For the power group, RFD up to 250 milliseconds highly correlated with % type IIx muscle fibers and type IIx fiber CSA (r = 0.670-0.826; p ≤ 0.05), as well as with %CSA of type IIx fibers (r = 0.714-0.975; p ≤ 0.05). Significant correlations were found between the relative RFD (·kg lower extremities lean mass) and CSA-%CSA of type II and IIx fibers for the power group (r = 0.676-0.903; p ≤ 0.05). No significant correlations were found between muscle morphology and RFD for the other groups. In conclusion, the present data suggest that there is a strong link between the type IIx muscle fibers and early RFD and relative RFD in power-trained participants. Type II fibers seem to be moderately linked with RFD in non-power-trained individuals.

A Genome-Wide Association Study of Sprint Performance in Elite Youth Football Players

Pickering, C, Suraci, B, Semenova, EA, Boulygina, EA, Kostryukova, ES, Kulemin, NA, Borisov, OV, Khabibova, SA, Larin, AK, Pavlenko, AV, Lyubaeva, EV, Popov, DV, Lysenko, EA, Vepkhvadze, TF, Lednev, EM, Leońska-Duniec, A, Pająk, B, Chycki, J, Moska, W, Lulińska-Kuklik, E, Dornowski, M, Maszczyk, A, Bradley, B, Kana-ah, A, Cięszczyk, P, Generozov, EV, and Ahmetov, II. A genome-wide association study of sprint performance in elite youth football players. J Strength Cond Res 33(9): 2344-2351, 2019-Sprint speed is an important component of football performance, with teams often placing a high value on sprint and acceleration ability. The aim of this study was to undertake the first genome-wide association study to identify genetic variants associated with sprint test performance in elite youth football players and to further validate the obtained results in additional studies. Using micro-array data (600 K-1.14 M single nucleotide polymorphisms [SNPs]) of 1,206 subjects, we identified 12 SNPs with suggestive significance after passing replication criteria. The polymorphism rs55743914 located in the PTPRK gene was found as the most significant for 5-m sprint test (p = 7.7 × 10). Seven of the discovered SNPs were also associated with sprint test performance in a cohort of 126 Polish women, and 4 were associated with power athlete status in a cohort of 399 elite Russian athletes. Six SNPs were associated with muscle fiber type in a cohort of 96 Russian subjects. We also examined genotype distributions and possible associations for 16 SNPs previously linked with sprint performance. Four SNPs (AGT rs699, HSD17B14 rs7247312, IGF2 rs680, and IL6 rs1800795) were associated with sprint test performance in this cohort. In addition, the G alleles of 2 SNPs in ADRB2 (rs1042713 & rs1042714) were significantly over-represented in these players compared with British and European controls. These results suggest that there is a genetic influence on sprint test performance in footballers, and identifies some of the genetic variants that help explain this influence.

VGLL3 operates via TEAD1, TEAD3 and TEAD4 to influence myogenesis in skeletal muscle.

ABSTRACTVGLL proteins are transcriptional co-factors that bind TEAD family transcription factors to regulate events ranging from wing development in fly, to muscle fibre composition and immune function in mice. Here, we characterise Vgll3 in skeletal muscle. We found that mouse Vgll3 was expressed at low levels in healthy muscle but that its levels increased during hypertrophy or regeneration; in humans, VGLL3 was highly expressed in tissues from patients with various muscle diseases, such as in dystrophic muscle and alveolar rhabdomyosarcoma. Interaction proteomics revealed that VGLL3 bound TEAD1, TEAD3 and TEAD4 in myoblasts and/or myotubes. However, there was no interaction with proteins from major regulatory systems such as the Hippo kinase cascade, unlike what is found for the TEAD co-factors YAP (encoded by YAP1) and TAZ (encoded by WWTR1). Vgll3 overexpression reduced the activity of the Hippo negative-feedback loop, affecting expression of muscle-regulating genes including Myf5, Pitx2 and Pitx3, and genes encoding certain Wnts and IGFBPs. VGLL3 mainly repressed gene expression, regulating similar genes to those regulated by YAP and TAZ. siRNA-mediated Vgll3 knockdown suppressed myoblast proliferation, whereas Vgll3 overexpression strongly promoted myogenic differentiation. However, skeletal muscle was overtly normal in Vgll3-null mice, presumably due to feedback signalling and/or redundancy. This work identifies VGLL3 as a transcriptional co-factor operating with the Hippo signal transduction network to control myogenesis.

Cellular Aspects of Muscle Specialization Demonstrate Genotype - Phenotype Interaction Effects in Athletes.

IntroductionGene polymorphisms are associated with athletic phenotypes relying on maximal or continued power production and affect the specialization of skeletal muscle composition with endurance or strength training of untrained subjects. We tested whether prominent polymorphisms in genes for angiotensin converting enzyme (ACE), tenascin-C (TNC), and actinin-3 (ACTN3) are associated with the differentiation of cellular hallmarks of muscle metabolism and contraction in high level athletes.MethodsMuscle biopsies were collected from m. vastus lateralis of three distinct phenotypes; endurance athletes (n = 29), power athletes (n = 17), and untrained non-athletes (n = 63). Metabolism-, and contraction-related cellular parameters (such as capillary-to-fiber ratio, capillary length density, volume densities of mitochondria and intramyocellular lipid, fiber mean cross sectional area (MCSA) and volume densities of myofibrils) and the volume densities of sarcoplasma were analyzed by quantitative electron microscopy of the biopsies. Gene polymorphisms of ACE (I/D (insertion/deletion), rs1799752), TNC (A/T, rs2104772), and ACTN3 (C/T, rs1815739) were determined using high-resolution melting polymerase chain reaction (HRM-PCR). Genotype distribution was assessed using Chi2 tests. Genotype and phenotype effects were analyzed by univariate or multivariate analysis of variance and post hoc test of Fisher. P-values below 0.05 were considered statistically significant.ResultsThe athletes demonstrated the specialization of metabolism- and contraction-related cellular parameters. Differences in cellular parameters could be identified for genotypes rs1799752 and rs2104772, and localized post hoc when taking the interaction with the phenotype into account. Between endurance and power athletes these concerned effects on capillary length density for rs1799752 and rs2104772, fiber type distribution and volume densities of myofibrils (rs1799752), and MSCA (rs2104772). Endurance athletes carrying the I-allele of rs1799752 demonstrated 50%-higher volume densities of mitochondria and sarcoplasma, when power athletes that carried only the D-allele showed the highest fiber MCSAs and a lower percentage of slow type muscle fibers.DiscussionACE and tenascin-C gene polymorphisms are associated with differences in cellular aspects of muscle metabolism and contraction in specifically-trained high level athletes. Quantitative differences in muscle fiber type distribution and composition, and capillarization in knee extensor muscle explain, in part, identified associations of the insertion/deletion genotypes of ACE (rs1799752) with endurance- and power-type Sports.

Effect of Concurrent Power Training and High-Intensity Interval Cycling on Muscle Morphology and Performance.

Spiliopoulou, P, Zaras, N, Methenitis, S, Papadimas, G, Papadopoulos, C, Bogdanis, GC, and Terzis, G. Effect of concurrent power training and high-intensity interval cycling on muscle morphology and performance. J Strength Cond Res 35(9): 2464-2471, 2021-The aim of the study was to examine the effect of performing high-intensity interval cycling on muscle morphology and performance immediately after power training (PT). Twenty healthy female physical education students were assigned into 2 training groups. One group performed PT, and the other group performed the same PT followed by high-intensity interval aerobic training on a cycle ergometer (PTC). Training was performed 3 days per week for 6 weeks. Countermovement jump (CMJ) height and CMJ power, half-squat maximal strength (1 repetition maximum), maximum aerobic power, vastus lateralis muscle fiber composition, and cross-sectional area (CSA) were evaluated before and after the intervention. Countermovement jump height increased after PT (10.1 ± 6.6%, p = 0.002) but not after PTC (-5.1 ± 10.5%, p = 0.099), with significant difference between groups (p = 0.001). Countermovement jump power increased after PT (4.5 ± 4.9%, p = 0.021) but not after PTC (-2.4 ± 6.4, p = 0.278), with significant difference between groups (p = 0.017). One repetition maximum increased similarly in both groups. Muscle fiber composition was not altered after either PT or PTC. Vastus lateralis muscle fiber CSA increased significantly and similarly after both PT (I: 16.9 ± 16.2%, p = 0.035, ΙΙΑ: 12.7 ± 10.9%, p = 0.008,ΙΙΧ: 15.5 ± 17.1%, p = 0.021) and PTC (Ι: 18.0 ± 23.7%, p = 0.033,ΙΙΑ: 18.2 ± 11.4%, p = 0.001,ΙΙΧ: 25.5 ± 19.6%, p = 0.003). These results suggest that the addition of high-intensity interval cycling to PT inhibits the anticipated increase in jumping performance induced by PT per se. This inhibition is not explained by changes in muscle fiber type composition or vastus lateralis muscle fiber CSA adaptations.

MON-LB038 Reduced Exercise Endurance And Skeletal Muscle Alterations In A Prenatally Androgenized Rat Model For Polycystic Ovary Syndrome

BACKGROUND: Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in women, impacting female reproductive, cardiometabolic, and psychological health. Studies of metabolic dysfunction in women with PCOS have primarily focused on adipose tissue and obesity-related changes. Some studies have reported changes in lean body mass and muscle function in women with PCOS. OBJECTIVE: To determine if prenatally androgenized (PNA) female rats exhibit altered exercise endurance or differences in skeletal muscle mass or morphology compared to control rats. METHODS: Sprague-Dawley rats were prenatally exposed to 5 mg testosterone or vehicle alone from gestational days 16-19. At 15 weeks of age, females were subjected to rotarod time trials as a measure of exercise endurance. At 16 weeks of age, hindlimb skeletal muscle mass, fiber cross-sectional area (CSA), and fiber composition were determined. Expression of ATP synthase was also investigated. RESULTS: Compared with controls, PNA female rats demonstrated greater total body and hindlimb muscle weights, and trends toward diminished time on the rotarod, as well as greater type II muscle fiber composition and levels of ATP synthase in the gastrocnemius. No changes were observed in gastrocnemius or soleus muscle fiber CSA, or in soleus fiber type composition or ATP synthase expression. CONCLUSIONS: PNA female rats exhibit changes in gastrocnemius muscle that are consistent with a change in muscle fiber composition, which may affect exercise endurance. Findings in this rat model for PCOS are consistent with findings in women with the disorder. Sources of Research Support: LECOM institutional funding to DS. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

Effects of neuromuscular electrical stimulation on muscle atrophy and muscle fiber composition in quadriceps muscles of chronic obstructive pulmonary disease rats

Objective To investigate the effect of neuromuscular electrical stimulation(NMES)on muscle atrophy and muscle fiber type conversion in quadriceps muscles of rats with chronic obstructive pulmonary disease(COPD). Methods Forty-eight male SPF Wistar rats were randomly divided into three groups: the healthy control group, COPD model group and NMES treatment group, with sixteen rats in each group.Rats in the NMES treatment group were given alternating electrical stimulation at 100 Hz and 2 Hz, with each stimulation time of 30 min, 7 days per week, for 4 weeks.The control group and the COPD model group were only treated with electrode sheets.After the intervention, the endurance running distance measurement, the pathological changes of rat quadriceps muscle detected by HE staining, the mRNA and protein content of MSTN, MyHC(Myosin Heavy Chain)-Ⅰ, MyHC-Ⅱa and MyHC-Ⅱx in quadriceps muscles determined by Realtime PCR and Western Blot were performed. Results Compared with the healthy control group, the cross-sectional area, endurance running distance and MyHC-Ⅰ mRNA and protein expressions in the quadriceps muscles were decreased[(654.7±53.7) μm2vs.(1079.8±117.2) μm2, (396.7±42.4) m vs.(607.4±56.3) m, 0.407±0.054 vs.0.997±0.069, 0.884±0.102 vs.1.723±0.156, t=4.642, 3.785, 24.723 and 18.640, P=0.008, 0.033, 0.000 and 0.000, respectively], while MSTN, MyHC-Ⅱa and MyHC-Ⅱx mRNA and protein expressions were increased in the COPD model group(all P<0.01). Compared with COPD model, the cross-sectional area(997.5±92.4 μm2), endurance running distance(597.2±65.8 m)and the expression levels of MyHC-ⅠmRNA(0.884±0.097)and protein(1.534±0.182)in the quadriceps muscles were increased(t=3.734, 3.602, 19.988 and 13.666, P=0.035, 0.043, 0.000, 0.000), and the mRNA and protein expression levels of MSTN, MyHC-Ⅱa and MyHC-Ⅱx were decreased in the NMES treatment group(all P<0.01). Further correlation analysis found that the protein expression of MSTN in the quadriceps muscles was negatively correlated with muscle cross-sectional area, MyHC-Ⅰprotein levels and endurance running distance(r=-0.724, -0.426 and -0.536, P=0.002, 0.036 and 0.007, respectively), and positively correlated with the protein expressions of MyHC-Ⅱa and MyHC-Ⅱx(r=0.408 and 0.392, P=0.042 and 0.048). Conclusions The expression of MSTN is increased in quadriceps muscle of COPD rats, and NMES can inhibit the expression of MSTN in quadriceps muscles.MSTN is associated with muscle atrophy and muscle fiber conversion in COPD.Inhibition of MSTN expression can improve muscle atrophy and reverse muscle fiber transformation. Key words: Pulmonary disease, chronic obstructive; Electric stimulation therapy; Muscular disorders, atrophic

A pilot study to elucidate effects of artificial selection by size on the zebrafish (Danio rerio) fast skeletal muscle transcriptome

Fish size is a complex trait determined by the interaction of environmental and genetic factors. While evidence exists that fish final length and size are partially determined by muscle fibre structure. However, the molecular basis behind final body size and muscle fibre composition remains yet to be fully understood. Here we use the fish model zebrafish (Danio rerio) to explore the molecular mechanisms involved in muscle fibre number, muscle growth and their role on animal size determination. In order to do so, we used two lines of zebrafish artificially selected by Amaral and Johnston 2012 for body length to obtain large (L) and small (S) genetic lineages. After selection animals from the L-lineage were significantly larger than individuals from the S-lineage (+6.6%, +6.7% and + 5.5% for standard, total and fork lengths) and had larger and higher number of muscle fibres (+15% and + 24% on average fibre area and fibre number respectively) while individuals from S-lineage showed a higher fibre density (+17%). RNAseq analysis on fast skeletal muscle revealed differences in gene expression, splice variants (SV) abundance and single nucleotide polymorphism (SNPs) retention between lineages, indicating the complexity of the molecular processes involved in the determination of the trait. We found that animals from the L-lineage showed an enrichment in genes related to the dystroglycan complex (GO:0016011) while genes related to the proteasome (GO:0022624), sarcomere (GO:0030017), muscle homeostasis (GO:0046716) and response to stress (GO:0006950) were enriched on the S-lineage. At individual gene level we also found differences in expression, SV or/and SNPs retention for some key genes involved in muscle development such as mef2ca, mef2cb, stac3, map14a and components of the circadian network (per1a, per1b, per3 and cry2b). These preliminary results provide an initial insight of the molecular changes induced by artificial selection for size, that could aid future studies related to determination of fish growth.

Modulation of exercise training related adaptation of body composition and regulatory pathways by anabolic steroids

Anabolic steroids have a long history of abuse in amateur and professional athletics. However, their interaction with training and the resulting effects on body composition and tissue adaptation, relying on a concert of factors and pathways, remain under investigation. This study aims at investigating the changes of body composition and the expression of selected genes and pathways essential for this adaptation process. Therefore, male wistar rats were treated with the anabolic steroid metandienone in two groups (n = 16; metandienone, metandienone + exercise) alongside with control groups (n = 16; control, exercise). Following a 6-week steep-angle treadmill training protocol, weight of organs, visceral fat and muscles was determined. M. gastrocnemius was histologically assessed by ATPase staining, mRNA and protein levels of factors of regeneration, hypertrophy and myogenesis and selected master regulators and markers were determined. Results show additive effects of anabolic steroids and exercise on body, tibia and reproductive organs weight. Mm. gastrocnemius and soleus weight was increased by training but not anabolic steroids. Muscle fiber diameter and composition remained unchanged. Visceral fat mass and fat cell size was affected by training and anabolic steroids but no additive effects could be observed. Exercise and anabolic steroids result in a complex regulation of the expression of genes in M. Gastrocnemius involved in skeletal muscle metabolism, hypertrophy, inflammation and regeneration. In summary, our data suggests distinct molecular mechanisms involved in the adaptation of the skeletal muscle to anabolic androgenic steroids and exercise. Metandienone treatment neither results in skeletal muscle hypertrophy nor liver-toxic effects but in an induction of skeletal muscle regeneration and an activation of endocrine negative feedback. Moreover our study demonstrates that visceral fat and bone responds with higher sensitivity to ASS and exercise than the skeletal muscle. This apparent plasticity of adipose and bone tissue rather than skeletal muscle could indicate a potentially superior future role of fat rather than muscle related parameters to detect and AAS abuse in a biologic passport strategy in professional athletes.

Study of the Chronology of Expression of Ten Extracellular Matrix Molecules during the Myogenesis in Cattle to Better Understand Sensory Properties of Meat.

The sensory properties of beef are known to depend on muscle fiber and intramuscular connective tissue composition (IMCT). IMCT is composed of collagens, proteoglycans and glycoproteins. The differentiation of muscle fibers has been extensively studied but there is scarcity in the data concerning IMCT differentiation. In order to be able to control muscle differentiation to improve beef quality, it is essential to understand the ontogenesis of IMCT molecules. Therefore, in this study, we investigated the chronology of appearance of 10 IMCT molecules in bovine Semitendinosus muscle using immunohistology technique at five key stages of myogenesis. Since 60 days post-conception (dpc), the whole molecules were present, but did not have their final location. It seems that they reach it at around 210 dpc. Then, the findings emphasized that since 210 dpc, the stage at which the differentiation of muscle fibers is almost complete, the differentiation of IMCT is almost completed. These data suggested that for the best controlling of the muscular differentiation to improve beef sensory quality, it would be necessary to intervene very early (before the IMCT constituents have acquired their definitive localization and the muscle fibers have finished differentiating), i.e., at the beginning of the first third of gestation.

Development of a Non-invasive Methodology for the Assessment of Muscle Fibre Composition.

The percentage area of fast twitch fibres of a muscle is a major determinant of muscle mechanical power and, thus, an important biomarker for the evaluation of training processes. However, the invasive character of the assessment (muscle biopsy) limits the wide application of the biomarker in the training praxis. Our purpose was to develop a non-invasive method for the assessment of fast twitch fibre content in human soleus muscle. From a theoretical point of view, the maximum muscle mechanical power depends on the fibre composition, the muscle volume and muscle specific tension. Therefore, we hypothesised that the percentage area of type II fibres would show a correlation with the maximum muscle mechanical power normalised to muscle volume and specific muscle contractile strength (i.e., plantar flexion moment divided by muscle cross-sectional area). In 20 male adults, the percentage area of type II fibres, volume and maximum cross-sectional area of the soleus muscle as well as the maximum plantar flexion moment and the maximum mechanical power were measured using muscle biopsies, magnetic resonance imaging and dynamometry. The maximum mechanical power normalised to muscle volume and specific muscle contractile strength provided a significant relationship (r = 0.654, p = 0.002) with the percentage area of type II fibres. Although the proposed assessment parameter cannot fully replace histological measurements, the predictive power of 43% can provide a relevant contribution to performance diagnostics in the training praxis.

The Variability of DNA Structure and Muscle-Fiber Composition

Abstract—Competitive success in sports, as well as a predisposition to some chronic pathologies, depends to a certain degree on the composition of muscle fibers. The proportional variability in muscle fibers (slow fibers ranging from 5 to 90%) among people depends on their genotypes and environmental factors. The contribution of hereditary factors to the development of muscle fibers ranges from 40 to 50%. This review describes contemporary approaches to the associations between DNA polymorphisms and the muscle fiber composition. Seven DNA polymorphisms associated with the proportional variability in skeletal muscle fiber types that were also shown to have an association with a predisposition to athletic activities and some diseases, such as obesity, type II diabetes, and hypertension, have been detected thus far. These seven markers are localized in the genes that are responsible for the contractile characteristics of skeletal muscles, lipid and carbohydrate metabolism, vascular tonus, and adaptation to hypoxia. Studies based on the whole-genome and epigenomic technologies are now underway to solve the problem of genetic determination of muscle fibers. The results of the study will permit the development of noninvasive methods for determining the composition of human muscle fibers and improving the efficiency of athletic training.