The growth and development of skeletal muscle is an important factor affecting pork production and quality, which is elaborately regulated by many genetic and nutritional factors. MicroRNA (miRNA) is a non-coding RNA with a length of about 22 nt, which binds to the 3'UTR sequence of the mRNA of the target genes, and consequently regulates its post-transcriptional expression level. In recent years, a large number of studies have shown that miRNAs are involved in various life processes such as growth and development, reproduction, and diseases. The role of miRNAs in the regulation of porcine skeletal muscle development was reviewed, with the hope to provide a reference for the genetic improvement of pigs.
Swine ; Animals ; MicroRNAs/metabolism* ; Muscle, Skeletal/metabolism* ; Muscle Development/genetics*

The shivering and nonshivering thermogenesis in skeletal muscles is important for maintaining body temperature in a cold environment. In addition to nervous-humoral regulation, adipose tissue was demonstrated to directly respond to cold in a cell-autonomous manner to produce heat. However, whether skeletal muscle can directly respond to low temperature in an autoregulatory manner is unknown. Transient receptor potential (TRP) channels TRPM8 and TRPA1 are two important cold sensors. In the current study, we found TRPM8 was expressed in mouse skeletal muscle tissue and C2C12 myotubes by RT-PCR. After exposure to 33 °C for 6 h, the gene expression pattern of C2C12 myotubes was significantly changed which was evidenced by RNA-sequencing. KEGG-Pathway enrichment analysis of these differentially expressed genes showed that low temperature changed several important signaling pathways, such as IL-17, TNFα, MAPK, FoxO, Hedgehog, Hippo, Toll-like receptor, Notch, and Wnt signaling pathways. Protein-protein interaction network analysis revealed that IL-6 gene was a key gene which was directly affected by low temperature in skeletal muscle cells. In addition, both mRNA and protein levels of IL-6 were increased by 33 °C exposure in C2C12 myotubes. In conclusion, our findings demonstrated that skeletal muscle cells could directly respond to low temperature, characterized by upregulated expression of IL-6 in skeletal muscle cells.
Animals ; Cold Temperature ; Interleukin-6/metabolism* ; Mice ; Muscle Fibers, Skeletal/metabolism* ; Muscle, Skeletal/physiology* ; Temperature

Calpains are intracellular nonlysosomal Ca(2+-) regulated cysteine proteases, widely located in the tissues of most mammals. Skeletal muscle tissue mainly expresses m-calpain, µ-caplain, n-calpain, and their endogenous inhibitor calpastatin. They are closely related to the cell apoptosis, cytoskeleton formation, cell cycles, etc. Calpains are also considered to be participating in the protein degradation process. Severe burns are typically followed by hypermetabolic responses that are characterized by hyperdynamic circulatory responses with increased proteolysis and cell apoptosis. Recently, overloading of Ca(2+) in skeletal muscle cells, which activates the calpains is observed after a serious burn. This paper aims to review the current research of the relationship between calpains and post-burn skeletal muscle wasting from the perspectives of structure, function, and physiological activities.
Animals ; Burns ; metabolism ; pathology ; Calpain ; metabolism ; Muscle, Skeletal ; metabolism ; pathology

Most of the major advances in burn treatment were made within the last five decades. However, hypermetabolic response after severe burn remains a problem in the treatment of patients with massive burn. As skeletal muscle accounts for over 50% of body cell dry weight, its catabolism exerts profound effect on body metabolism as a whole. Main mechanisms underlying skeletal muscle wasting induced by severe burn include activation of ubiquitin-proteasome pathway, bringing about breakdown of muscle protein, and myonuclear apoptosis. Therapeutic strategies for skeletal muscle wasting after burn mainly include maintenance of room temperature at (31.5 +/- 0.7) degrees C, early active and passive exercise of skeletal muscles, administration of beta adrenergic receptor blocker such as Propranolol, recombinant growth hormone, androgen, and insulin, which has lately been proven to possess the effect of suppressing myonuclear apoptosis after burn. Combination of multiple therapeutic strategies is beneficial in reducing complications of burn patients, particularly wide ranged skeletal muscle atrophy, to achieve a better clinical outcome.
Apoptosis ; Burns ; drug therapy ; metabolism ; pathology ; Humans ; Muscle, Skeletal ; metabolism

Skeletal muscle is one of the most important organs in animal, and the regulatory mechanism of skeletal muscle development is of great importance for the diagnosis of muscle-related diseases and the improvement of meat quality of livestock. The regulation of skeletal muscle development is a complex process, which is regulated by a large number of muscle secretory factors and signaling pathways. In addition, in order to maintain steady-state and maximum use of energy metabolism in the body, the body coordinates multiple tissues and organs to form the complex and sophisticated metabolic regulation network, which plays an important role for the regulation of skeletal muscle development. With the development of omics technologies, the underlying mechanism of tissue and organ communication has been deeply studied. This paper reviews the effects of crosstalk among adipose tissue, nerve tissue and intestinal tissue on skeletal muscle development, with the aim to provide a theoretical basis for targeted regulation of skeletal muscle development.
Animals ; Muscle, Skeletal/metabolism* ; Adipose Tissue/metabolism* ; Signal Transduction

Titin, the largest known protein in the body expressed in three isoforms (N2A, N2BA and N2B), is essential for muscle structure, force generation, conduction and regulation. Since the 1950s, muscle contraction mechanisms have been explained by the sliding filament theory involving thin and thick muscle filaments, while the contribution of cytoskeleton in force generation and conduction was ignored. With the discovery of insoluble protein residues and large molecular weight proteins in muscle fibers, the third myofilament, titin, has been identified and attracted a lot of interests. The development of single molecule mechanics and gene sequencing technology further contributed to the extensive studies on the arrangement, structure, elastic properties and components of titin in sarcomere. Therefore, this paper reviews the structure, isforms classification, elastic function and regulatory factors of titin, to provide better understanding of titin.
Connectin/genetics* ; Muscle Proteins/metabolism* ; Protein Isoforms/genetics* ; Sarcomeres/metabolism* ; Muscle Fibers, Skeletal/metabolism*

Skeletal muscle plays a paramount role in physical activity, metabolism, and energy balance, while its homeostasis is being challenged by multiple unfavorable factors such as injury, aging, or obesity. Exosomes, a subset of extracellular vesicles, are now recognized as essential mediators of intercellular communication, holding great clinical potential in the treatment of skeletal muscle diseases. Herein, we outline the recent research progress in exosomal isolation, characterization, and mechanism of action, and emphatically discuss current advances in exosomes derived from multiple organs and tissues, and engineered exosomes regarding the regulation of physiological and pathological development of skeletal muscle. These remarkable advances expand our understanding of myogenesis and muscle diseases. Meanwhile, the engineered exosome, as an endogenous nanocarrier combined with advanced design methodologies of biomolecules, will help to open up innovative therapeutic perspectives for the treatment of muscle diseases.
Exosomes/physiology* ; Muscle, Skeletal/metabolism* ; Cell Communication ; Homeostasis

Cancer cachexia is a multi-organ syndrome and closely related to changes in signal communication between organs, which is mediated by cancer cachexia factors. Cancer cachexia factors, being the general name of inflammatory factors, circulating proteins, metabolites, and microRNA secreted by tumor or host cells, play a role in secretory or other organs and mediate complex signal communication between organs during cancer cachexia. Cancer cachexia factors are also a potential target for the diagnosis and treatment. The pathogenesis of cachexia is unclear and no clear effective treatment is available. Thus, the treatment of cancer cachexia from the perspective of the tumor ecosystem rather than from the perspective of a single molecule and a single organ is urgently needed. From the point of signal communication between organs mediated by cancer cachexia factors, finding a deeper understanding of the pathogenesis, diagnosis, and treatment of cancer cachexia is of great significance to improve the level of diagnosis and treatment. This review begins with cancer cachexia factors released during the interaction between tumor and host cells, and provides a comprehensive summary of the pathogenesis, diagnosis, and treatment for cancer cachexia, along with a particular sight on multi-organ signal communication mediated by cancer cachexia factors. This summary aims to deepen medical community's understanding of cancer cachexia and may conduce to the discovery of new diagnostic and therapeutic targets for cancer cachexia.
Humans ; Cachexia/pathology* ; Ecosystem ; Neoplasms/metabolism* ; Syndrome ; Muscle, Skeletal/pathology*

BACKGROUND: Neostigmine, a cholinesterase inhibitor, is known to reverse the neuromuscular blocking action induced by nondepolarizing muscle relaxants at the end of general anesthesia. Some authors, however, reported that neostigmine has the properties of a neuromuscular block in skeletal muscles while others reported that neostigmine caused the smooth muscles such as the diaphragm to relax rather than to contract. The purpose of this study was to evaluate the effect of neostigmine at different doses on the tracheal smooth muscle in rabbits. METHODS: Isolated tracheal ring preparation in rabbits was used. Groups were divided into 7 groups; acetylcholine group (acetylcholine cumulative administered at doses of 10 8, 10 7, 10 6, 10 5, 10 4 and 10 3 M), neostigmine group (neostigmine cumulative administered at doses of 10 8, 10 7, 10 6, 10 5, 10 4 and 10 3 M), acetylcholine 10 6 M + neostigmine group (acetylcholine 10 6 M prior to neostigmine administered at doses of 10 8, 10 7, 10 6, 10 5, 10 4 and 10 3 M), acetylcholine 10 4 M + neostigmine group (acetylcholine 10 4 M prior to neostigmine administered at doses of 10 8, 10 7, 10 6, 10 5, 10 4 and 10 3 M), neostigmine 10 5, 10 4 and 10 3 M groups (neostigmine administered at doses of 10 5, 10 4 and 10 3 M). Smooth muscle contraction was evaluated in isometric tension per gram of tissue. RESULTS: In the acetylcholine group, the contractions increased as the dosage increased (10 8 10 3 M). In the neostigmine group, the contractions increased as the dosage increased (10 8 10 4 M), but at 10 3 M of neostigmine, contractions suddenly decreased. In addition when acetylcholine 10 6 M was given as a pretreatment, there was a sudden decrease in muscle contractions induced by neostigmine at 10 3 M. Also the contractions induced by 10 3 M neostigmine were less than that of 10 4 and 10 5 M. CONCLUSIONS: We concluded that neostigmine caused smooth muscle contraction at low concentrations by blocking acetylcholine metabolism, but at high concentrations, smooth muscle contractions were decreased and this might be due to direct action at the acetylcholine receptor.
Acetylcholine ; Anesthesia, General ; Cholinesterases ; Diaphragm ; Metabolism ; Muscle Contraction ; Muscle, Skeletal ; Muscle, Smooth* ; Neostigmine* ; Neuromuscular Blockade ; Rabbits*

Age-dependent loss of skeletal muscle mass and function is a feature of sarcopenia, and increases the risk of many aging-related metabolic diseases. Here, we report phenotypic and single-nucleus transcriptomic analyses of non-human primate skeletal muscle aging. A higher transcriptional fluctuation was observed in myonuclei relative to other interstitial cell types, indicating a higher susceptibility of skeletal muscle fiber to aging. We found a downregulation of FOXO3 in aged primate skeletal muscle, and identified FOXO3 as a hub transcription factor maintaining skeletal muscle homeostasis. Through the establishment of a complementary experimental pipeline based on a human pluripotent stem cell-derived myotube model, we revealed that silence of FOXO3 accelerates human myotube senescence, whereas genetic activation of endogenous FOXO3 alleviates human myotube aging. Altogether, based on a combination of monkey skeletal muscle and human myotube aging research models, we unraveled the pivotal role of the FOXO3 in safeguarding primate skeletal muscle from aging, providing a comprehensive resource for the development of clinical diagnosis and targeted therapeutic interventions against human skeletal muscle aging and the onset of sarcopenia along with aging-related disorders.
Animals ; Humans ; Sarcopenia/metabolism* ; Forkhead Box Protein O3/metabolism* ; Muscle, Skeletal/metabolism* ; Aging/metabolism* ; Primates/metabolism*