Myostatin DNA vaccine increases skeletal muscle mass and endurance in mice

Enhanced Muscle Fibers of Epinephelus coioides by Myostatin Autologous Nucleic Acid Vaccine

Epinephelus coioides is a fish species with high economic value due to its delicious meat, high protein content, and rich fatty acid nutrition. It has become a high-economic fish in southern parts of China and some other Southeast Asian countries. In this study, the myostatin nucleic acid vaccine was constructed and used to immunize E. coioides. The results from body length and weight measurements indicated the myostatin nucleic acid vaccine promoted E. coioides growth performance by increasing muscle fiber size. The results from RT-qPCR analysis showed that myostatin nucleic acid vaccine upregulated the expression of myod, myog and p21 mRNA, downregulated the expression of smad3 and mrf4 mRNA. This preliminary study is the first report that explored the role of myostatin in E. coioides and showed positive effects of autologous nucleic acid vaccine on the muscle growth of E. coioides. Further experiments with increased numbers of animals and different doses are needed for its application to E. coiodes aquaculture production.

Myostatin (MSTN) Gene Indel Variation and Its Associations with Body Traits in Shaanbei White Cashmere Goat

Myostatin (MSTN) gene, also known as growth differentiation factor 8 (GDF8), is a member of the transforming growth factor-beta super-family and plays a negative role in muscle development. It acts as key points during pre- and post-natal life of amniotes that ultimately determine the overall muscle mass of animals. There are several studies that concentrate on the effect of a 5 bp insertion/deletion (indel) within the 5' untranslated region (5' UTR) of goat MSTN gene in goats. However, almost all sample sizes were below 150 individuals. Only in Boer goats, the sample sizes reached 482. Hence, whether the 5 bp indel was still associated with the growth traits of goats in large sample sizes which were more reliable is not clear. To find an effective and dependable DNA marker for goat rearing, we first enlarged the sample sizes (n = 1074, Shaanbei White Cashmere goat) which would enhance the robustness of the analysis and did the association analyses between the 5 bp indel and growth traits. Results uncovered that the 5 bp indel was significantly related to body height, height at hip cross, and chest width index (p < 0.05). In addition, individuals with DD genotype had a superior growing performance than those with the ID genotype. These findings suggested that the 5 bp indel in MSTN gene are significantly associated with growth traits and the specific genotype might be promising for maker-assisted selection (MAS) of goats.

Myostatin gene promoter: structure, conservation and importance as a target for muscle modulation

Myostatin (MSTN) is one of the key factors regulating myogenesis. Because of its role as a negative regulator of muscle mass deposition, much interest has been given to its protein and, in recent years, several studies have analysed MSTN gene regulation. This review discusses the MSTN gene promoter, focusing on its structure in several animal species, both vertebrate and invertebrate. We report the important binding sites considering their degree of phylogenetic conservation and roles they play in the promoter activity. Finally, we discuss recent studies focusing on MSTN gene regulation via promoter manipulation and the potential applications they have both in medicine and agriculture.

A prepared anti-MSTN polyclonal antibody reverses insulin resistance of diet-induced obese rats via regulation of PI3K/Akt/mTOR&FoxO1 signal pathways

Suppression of myostatin (MSTN) is associated with skeletal muscle atrophy and insulin resistance. However, the mechanisms by which MSTN regulates insulin resistance are not well known. We have explored the signaling pathways through which MSTN regulates insulin resistance in diet-induced obese rats using a polyclonal antibody for MSTN. The anti-MSTN polyclonal antibody significantly improved insulin resistance and whole-body insulin sensitivity, decreased MSTN protein expression in muscle samples by 39% in diet-induced obese rats. Furthermore, the anti-MSTN polyclonal antibody significantly enhanced PI3K activity (140%), Akt phosphorylation (86%), GLUT4 protein expression (23%), the phosphorylation of mTOR (21%), and inhibited the phosphorylation of FoxO1 (57%), but did not affect the phosphorylation of GSK-3β. Thus, suppression of MSTN by the anti-MSTN polyclonal antibody reverses insulin resistance of diet-induced obesity via MSTN/PI3K/Akt/mTOR and MSTN/PI3K/Akt/FoxO1 signaling pathways.

Why cellular stress suppresses adipogenesis in skeletal tissue, but is ineffective in adipose tissue: control of mesenchymal cell differentiation via integrin binding sites in extracellular matrices

This Perspective addresses one of the major puzzles of adipogenesis in adipose tissue, namely its resistance to cellular stress. It introduces a concept of "density" of integrin binding sites in extracellular matrix, proposes a cellular signaling explanation for the observed effects of matrix elasticity and of cell shape on mesenchymal stem cell differentiation, and discusses how specialized integrin binding sites in collagen IV-containing matrices guard two pivotal physiological and evolutionary processes: stress-resistant adipogenesis in adipose tissues and preservation of pluripotency of mesenchymal stem-like cells in their storage niches. Finally, it proposes strategies to suppress adipogenesis in adipose tissues.

Genes contributing to genetic variation of muscling in sheep

Selective breeding programs aiming to increase the productivity and profitability of the sheep meat industry use elite, progeny tested sires. The broad genetic traits of primary interest in the progeny of these sires include skeletal muscle yield, fat content, eating quality, and reproductive efficiency. Natural mutations in sheep that enhance muscling have been identified, while a number of genome scans have identified and confirmed quantitative trait loci (QTL) for skeletal muscle traits. The detailed phenotypic characteristics of sheep carrying these mutations or QTL affecting skeletal muscle show a number of common biological themes, particularly changes in developmental growth trajectories, alterations of whole animal morphology, and a shift toward fast twitch glycolytic fibers. The genetic, developmental, and biochemical mechanisms underpinning the actions of some of these genetic variants are described. This review critically assesses this research area, identifies gaps in knowledge, and highlights mechanistic linkages between genetic polymorphisms and skeletal muscle phenotypic changes. This knowledge may aid the discovery of new causal genetic variants and in some cases lead to the development of biochemical and immunological strategies aimed at enhancing skeletal muscle.

Assessment of tools for marker-assisted selection in a marine commercial species: significant association between MSTN-1 gene polymorphism and growth traits

Growth is a priority trait from the point of view of genetic improvement. Molecular markers linked to quantitative trait loci (QTL) have been regarded as useful for marker-assisted selection in complex traits as growth. Polymorphisms have been studied in five candidate genes influencing growth in gilthead seabream (Sparus aurata): the growth hormone (GH), insulin-like growth factor-1 (IGF-1), myostatin (MSTN-1), prolactin (PRL), and somatolactin (SL) genes. Specimens evaluated were from a commercial broodstock comprising 131 breeders (from which 36 males and 44 females contributed to the progeny). In all samples eleven gene fragments, covering more than 13,000 bp, generated by PCR-RFLP, were analyzed; tests were made for significant associations between these markers and growth traits. ANOVA results showed a significant association between MSTN-1 gene polymorphism and growth traits. Pairwise tests revealed several RFLPs in the MSTN-1 gene with significant heterogeneity of genotypes among size groups. PRL and MSTN-1 genes presented linkage disequilibrium. The MSTN-1 gene was mapped in the centromeric region of a medium-size acrocentric chromosome pair.

Myostatin in the pathophysiology of skeletal muscle

Myostatin is an endogenous, negative regulator of muscle growth determining both muscle fiber number and size. The myostatin pathway is conserved across diverse species ranging from zebrafish to humans. Experimental models of muscle growth and regeneration have implicated myostatin as an important mediator of catabolic pathways in muscle cells. Inhibition of this pathway has emerged as a promising therapy for muscle wasting. Here we discuss the recent developments and the controversies in myostatin research, focusing on the molecular and cellular mechanisms underlying the actions of myostatin on skeletal muscle and the potential therapeutic role of myostatin on muscle-related disorders.

Polymorphisms of myostatin gene (MSTN) in four goat breeds and their effects on Boer goat growth performance

Polymorphisms of myostatin (MSTN) gene were investigated as a candidate marker for goat growth in 687 individuals by gene sequencing and polymerase chain reaction restriction fragment length polymorphism methods. Three potential genotypes (AA, AB and BB) of 5 bp indel (1,256 TTTTA/-) in 5'UTR were detected in four breeds. The polymorphism (CC, CD and DD) of substitution (1,388 T/A) in exon 1 was only segregating in Boer. Genotype AB resulted in significant increases in body weights at birth (BW0), 90 (BW90) and 300 (BW300) days of age, and birth body length compared to BB (P < 0.05). Whilst genotype CD contributed to heavier BW0 and BW90, and larger birth body height (BH) compared to CC (P < 0.05). Individuals either with AB or CD genotype also had greater values in other body sizes, although no significant differences appeared (P > 0.05). When in combination, the combined genotype ABCD displayed positive impacts on better growth traits in BW0, BW90, BW300, BH and BCG (P < 0.05). These results indicate that these markers in myostatin (MSTN) are associated with Boer growth and may be useful for marker assisted selection.

METABOLIC FUNCTIONS OF MYOSTATIN AND GDF11

Myostatin is a member of the transforming growth factor β superfamily of secreted growth factors that negatively regulates skeletal muscle size. Mice null for the myostatin gene have a dramatically increased mass of individual muscles, reduced adiposity, increased insulin sensitivity, and resistance to obesity. Myostatin inhibition in adult mice also increases muscle mass which raises the possibility that anti-myostatin therapy could be a useful approach for treating diseases such as obesity or diabetes in addition to muscle wasting diseases. In this review I will describe the present state of our understanding of the role of myostatin and the closely related growth factor growth/differentiation factor 11 on metabolism.

Endurance exercise training in myostatin null mice

The growth factor myostatin (Mstn) is a negative regulator of skeletal muscle mass. Mstn(-/-) muscles are hypertrophied, stronger, and more glycolytic than Mstn(+/+) muscles, suggesting that they might not perform endurance exercise as well as Mstn(+/+) mice. Indeed, it has previously been shown that treadmill exercise training reduces triceps weight in Mstn(-/-) mice. To analyze the response of Mstn(-/-) muscle to endurance exercise in detail, we carried out endurance training over 4 weeks to examine muscle mass, histology, and oxidative enzyme activity. We found that muscle mass was reduced with training in several muscles from both genotypes, with no evidence of muscle damage. Citrate synthase activity was increased with training in control and mutant mice. Non-trained Mstn(-/-) mice did, however, have lower maximal exercise capacity compared with Mstn(+/+) mice. These results show that Mstn(-/-) muscle retains the metabolic plasticity necessary to adapt normally to endurance training.

SNPs in the myostatin gene of the mollusk Chlamys farreri: association with growth traits

Myostatin (MSTN) is a member of the transforming growth factor-beta superfamily which negatively regulates growth of muscle tissue. In this study, 103 cultivated Chlamys farreri individuals were screened for polymorphisms in the MSTN gene using PCR-single strand conformation polymorphism (PCR-SSCP) and DNA sequencing methods. Two mutations were found: A/G at position 327 in exon 2, which caused an amino acid change from Thr to Ala (Thr305Ala), and C/T at position 289 in exon 3, which caused an amino acid change from Cys to Arg (Cys422Arg). One way ANOVA of the SNPs and growth traits showed that genotype GG of primer M5 had significantly higher body mass, soft-tissue mass, adductor muscle mass, shell length, shell height, absolute growth rate of shell height and body mass than those of genotype AG and AA (P<0.05). Genotype frequencies of genotype AA, AG and GG were 68.94%, 27.18% and 3.88%, respectively. The results present evidence that the C. farreri MSTN gene may be selected as a candidate gene for these growth traits.

Relation between extent of myostatin depletion and muscle growth in mature mice

Myostatin is a negative regulator of muscle growth and fiber size. Changes in myostatin expression might contribute to changes in muscle mass associated with various conditions, and reducing the amount of active myostatin is a potential strategy for preventing or reversing muscle atrophy. The present study was done to determine the extent to which myostatin levels must decline to induce growth of mature muscles. Myostatin expression was reduced by activating Cre recombinase in adult mice with floxed myostatin genes. The duration of Cre activation varied from 1 to 6 wk, and the residual myostatin mRNA expression after Cre activation varied from 3 to 63% of the normal level. Promyostatin levels declined in parallel with myostatin mRNA. There was no increase in muscle mass over the 3 mo following Cre activation if residual myostatin expression was >or=40% of normal. In mice with <40% of normal myostatin expression, muscle mass increased in proportion to the extent of myostatin depletion. In mice with <or=10% of normal myostatin expression, muscle mass increased approximately 25%. Myostatin depletion increased myonuclear domain volumes and the ratio of RNA to myonuclei probably by enhancing DNA transcription rather than by inhibiting RNA decay. There was no evidence that maintenance of the hypertrophy during chronic myostatin deficiency requires altered activity of Akt/mTOR or p38 MAPK signaling pathways. These data suggest that anabolic therapies based on reducing the concentration of active myostatin will be effective only if a very large proportion of the myostatin is removed or inactivated.

Stimulation of skeletal muscle myofibrillar protein synthesis, p70 S6 kinase phosphorylation, and ribosomal protein S6 phosphorylation by inhibition of myostatin in mature mice

Knocking out myostatin activity during development increases the rate of muscle protein synthesis. The present study was done to determine whether postdevelopmental loss of myostatin activity stimulates myofibrillar protein synthesis and the phosphorylation of some of the proteins involved in regulation of protein synthesis rate. Myostatin activity was inhibited for 4 days, in 4- to 5-mo-old male mice, with injections of an anti-myostatin antibody (JA16). The mean myofibrillar synthesis rate increased 19% (P < 0.01) relative to the mean rate in saline-treated mice, as determined by incorporation of deuterium-labeled phenylalanine. JA16 increased phosphorylation of p70 S6 kinase (S6K) and ribosomal protein S6 (rpS6) 1.9-fold (P < 0.05). It did not affect phosphorylation of eukaryotic initiation factor 4E-binding protein-1 or Akt. Microarrays and real-time PCR analyses indicated that JA16 administration did not selectively enrich levels of mRNAs encoding myofibrillar proteins, ribosomal proteins, or translation initiation and elongation factors. Rapamycin treatment did not affect the rate of myofibrillar protein synthesis whether or not the mice received JA16 injections, although it eliminated the phosphorylation of S6K and rpS6. We conclude that the normal level of myostatin activity in mature muscle is sufficient to inhibit myofibrillar synthesis rate and phosphorylation of S6K and rpS6. Reversal of the inhibition of myofibrillar synthesis with an anti-myostatin antibody is not dependent on mTOR activation.