Identification of irisin immunoreactivity in porcupine (Hystrix cristata) adrenal glands and kidneys

Irisin, a novel peptide, was initially been shown to be expressed explicitly in the muscle tissues. We studied the presence of irisin immunoreactivity in porcupine adrenal glands and kidneys. Immunocytochemistry showed that irisin was localised both in the adrenal cortex and adrenal medulla. In organs, irisin immunoreactivity was found in the tubular and collecting system of the nephron. The functional role of irisin in the adrenal gland and kidney has not been precisely yet. However, irisin might have a paracrine and autocrine function as do other locally produced peptides.     

鸢尾素-前体基因:分子结构、表达调控和生物学功能及其与骨骼肌纤维类型转化

鸢尾素(irisin)是新近发现的可分泌型肌源细胞因子,来源于Ⅲ型纤连蛋白组件包含蛋白5水解形成的多肽片段。目前证明鸢尾素及其前体基因在糖脂代谢疾病发生与运动治疗中发挥作用,可能与骨骼肌纤维类型转化存在关联。本文通过总结鸢尾素及其前体基因分子结构特点、表达调控和生物学功能最新研究进展,结合骨骼肌纤维类型转化机制,探讨分析鸢尾素-前体基因途径与骨骼肌纤维类型转化潜在分子关联,以期为畜禽肉质改良提供新思路。     

Ex vivo bupivacaine treatment results in increased adipogenesis of skeletal muscle cells in the rat

Intramuscular adipose tissue (IMAT) is observed in some skeletal muscle pathologies. IMAT is implicated not only in the disorders of muscle contraction, but also of metabolism and insulin sensitivity due to its nature as a secretary organ. Several studies indicate the presence of cells with adipogenic potential in skeletal muscle. However, the mechanism of fate specification that triggers these cells to enter an adipogenic program in vivo remains to be solved. In the present study, we examined whether activation of the adipogenic program of muscle‐resident cells precedes their proliferation upon muscle injury. For this purpose, muscle injury was induced by injecting bupivacaine (BPVC) to excised skeletal muscle ex vivo. Cells isolated from ex vivo BPVC‐treated muscle exhibited higher adipogenic potential than those from saline‐treated muscle. Pre‐plating exposure of skeletal muscle cells to basic fibroblast growth factor (bFGF) mimicked the effect of ex vivo BPVC‐treatment, suggesting that bFGF released from extracellular matrix in response to muscle injury activates their adipogenic program. Interestingly, the number of myotubes were significantly reduced in the culture from BPVC‐treated muscle, suggesting that adipocytes negatively regulate myogenesis.     

In vivo gene transfer into skeletal muscle of neonatal chicks by electroporation

Chicks (Gallus gallus domesticus) show considerable growth of skeletal muscle during the neonatal period. The in vivo gene transfer method is useful for studying gene function and can be employed to elucidate the molecular mechanisms of skeletal muscle growth in chicks. We evaluated the following conditions for gene transfer to the skeletal muscle of neonatal chicks by electroporation: (i) voltage; (ii) age of the chick; (iii) plasmid DNA injected amount; and (iv) duration of gene expression. The results obtained from this study indicate that the most efficient gene transfer condition was as follows: 75 µg of plasmid DNA encoding β‐galactosidase was injected into the gastrocnemius muscle of chicks at 4 days of age electroporated at 50 V/cm. In addition, peak transferred gene expression was observed from 3 days to 5 days after electroporation. Our results provide optimal electroporation conditions for elucidating the gene function related to skeletal muscle growth and development in neonatal chicks.     

Foetal development of skeletal muscle in bovines as a function of maternal nutrition,foetal sex and gestational age

To determine the effects of maternal nutrition on modifications of foetal development of the skeletal muscle and possible increase in the potential of skeletal muscle growth in cattle, gestating cows were either fed 190% NRC recommendations (overnourished; ON) or 100% NRC recommendation (control; CO). Interaction between maternal nutrition (MN) and the foetal sex (FS) was also investigated. Foetuses were necropsied at four different time points throughout gestation (139, 199, 241 and 268 days of gestation) to assess the mRNA expression of myogenic, adipogenic and fibrogenic markers in skeletal muscle. Phenotypic indicators of the development of skeletal muscle fibres, intramuscular lipogenesis and collagen development were also evaluated. Modifications in mRNA expression of skeletal muscle of foetuses were observed in function of MN and FS despite the lack of effect of MN and FS on foetal weight at necropsy. Maternal ON increased the mRNA expression of the myogenic marker Cadherin‐associated protein, beta 1 (CTNNB1) and adipogenic markers Peroxissome proliferator‐activated receptor gamma (PPARG) and Zinc finger protein 423 (ZNF423) at midgestation. However, no differences on foetal skeletal muscle development were observed between treatments at late gestation indicating that a compensatory development may have occurred on CO foetuses making the effect of MN on skeletal muscle development not significant at late gestation. Moreover, our data have shown an evidence of sexual dimorphism during foetal stage with a greater skeletal muscle development in male than in female foetuses. In conclusion, providing a higher nutritional level to pregnant cows changes the trajectory of the development of skeletal muscle during midgestation, but apparently does not change the potential of post‐natal growth of muscle mass of the offspring, as no differences in skeletal muscle development were observed in late gestation.     

Detection of Mycobacterium avium subsp. paratuberculosis in skeletal muscle and blood of ewes from a sheep farm in New Zealand

Abstract

AIM: To determine whether viable Mycobacterium avium subsp. paratuberculosis (Map) is present in skeletal muscle and blood in ewes with and without Johne's disease confirmed histologically.

METHODS: A total of 51 mixed-aged ewes in poor body condition from a farm with a history of clinical Johne's disease were culled and examined at necropsy. BACTEC radiometric culture was performed on samples of skeletal muscle from the biceps femoris, mononuclear cells in peripheral blood (hereafter referred to as blood), and ileum. Histological sections and Ziehl-Neelsen (ZN)-stained impression smears of terminal ileum and mesenteric lymph nodes were examined. Ewes were defined as having confirmed Johne's disease if there was histopathological evidence typical of the disease within the ileum and adjacent lymph nodes.

RESULTS: Eighteen of 21 (86%) ewes with confirmed clinical Johne's disease were culture-positive for Map from sites peripheral to the alimentary tract, comprising 15 from skeletal muscle and 13 from blood. Five of 30 (17%) ewes that did not have Johne's disease were culture-positive, with four from skeletal muscle and one from blood. The likelihood that ewes with confirmed Johne's disease had systemic Map infection compared with ewes without was determined as OR=30 (95% CI=6.3–142.0; p<0.001).

CONCLUSION: The prevalence of Map infection of skeletal muscle and blood in ewes with confirmed Johne's disease was 71% and 62% respectively, and in unaffected ewes was 13% for muscle and 3% for blood.

CLINICAL RELEVANCE: Skeletal muscle and blood are potential sources of exposure of humans to Map, and the risk appears higher from sheep with Johne's disease.     

Levels of mRNA for three selenoproteins in skeletal muscle of fetal and newborn pigs

Selenoproteins have wide-ranging functions throughout the body, including important roles in protection against oxidative stress, as well as muscle development and integrity. In this study, prepubertal gilts were randomly assigned to either a Se-sufficient or deficient diet (n = 12/treatment). Levels of mRNA coding for the selenoproteins glutathione peroxidase-1 (GPx-1), selenoprotein W (SelW) and selenoprotein N (SelN) and the concentration of Se in fetal and neonatal swine skeletal muscle (gluteus maximus) were measured at time intervals throughout gestation and immediately after birth. Total RNA was isolated from skeletal muscle, and cDNA was synthesized for real-time RT-PCR analysis of the selected selenoproteins. Selenium concentration in skeletal muscle of fetal and newborn pigs decreased throughout gestation (P < 0.0001) and was lower (P < 0.05) when dams were fed the low Se diet. Levels of GPx-1 mRNA in fetal skeletal muscle were unaffected by maternal Se intake nor did GPx-1 mRNA levels change during late gestation. Selenoprotein W mRNA levels increased (P = 0.01) in fetal skeletal muscle during late gestation but were reduced (P = 0.05) by low maternal intake of Se. Levels of SelN mRNA showed a gestational time by treatment interaction (P < 0.05). The increased levels of SelW mRNA in skeletal muscle during late gestation, despite a decrease in Se concentration, indicate that SelW may be an important antioxidant protein to the late term fetus and the newborn.     

Ankyloglossia in Dogs: A Morphological and Immunohistochemical Study

Ankyloglossia is a congenital anomaly of the tongue that is usually characterized by a short and thick lingual frenulum. The genetic mutations such as in TBox genes and other foetal mechanism have still been under investigation as possible causes of ankyloglossia. This study describes morphology of anklyoglossia phenotype found in members of two closely bred Kangal dog families. Morphology of ankyloglossia and immunohistochemical localization of αB-crystallin, an anti-apoptotic protein, in the frenulum tissue collected during frenectomy was described. Grossly, the lingual frenulum was observed as it extended up to the tip or near the tip of the tongue. The tip of the tongue was often notched and appeared in 'W' shape. No other craniofacial anomalies were associated with ankyloglossia. Histologically, the frenulum tissue was covered by stratified squamous epithelia of variable thickness. Skeletal muscle fibres were often scattered in the vicinity of collagen fibres of the lamina propria. αB-crystallin was immunolocalized exclusively in skeletal muscle fibres. In conclusion, ankyloglossia in the dog generally occurs as a sole anomaly. The presence of αB-crystallin immunoreactivity exclusively in skeletal muscle fibres suggests that there may be a connection between occurrences of ankyloglossia in the dog and a delay or interference with apoptosis of the skeletal fibres in the frenulum tissue.     

Long non‐coding RNA analysis of muscular responses to testosterone deficiency in Huainan male pigs

Long non‐coding RNAs (lncRNAs) participated in growth and development of skeletal muscle; however, little is known about their response to testosterone deficiency in porcine skeletal muscle. We compared lean mass related carcass traits and lncRNAs expression files in Longissimus dorsi (LD) muscle between intact and castrated Huainan male pigs. The results showed that castration significantly reduced eye muscle area and lean meat percentage (P < 0.05), but increased the fat mass weight (P < 0.05). Meanwhile, 8946 lncRNAs, including 6743 intergenic lncRNAs (lincRNAs), 498 anti‐sense lncRNAs, and 1705 intronic lncRNAs, were identified in porcine LD, among which, 385 lncRNAs were considered as the differentially expressed candidates between intact groups and castrated groups (q‐value < 0.05). Functional analysis indicated that these differently expressed lncRNAs and their target genes were involved in the estrogen receptor signaling pathway and skeletal and muscular system development and function. We first detect porcine muscular lncRNA response to castration, and the results suggested that lncRNAs and their target genes participated in the regulation of testosterone deficiency‐related skeletal muscle growth.     

Postmortem proteolysis is reduced in transgenic mice overexpressing calpastatin

Using both in vitro and in vivo approaches, numerous studies have provided evidence that mu-calpain is responsible for postmortem proteolysis. This paper reports the effect of overexpression of calpastatin on postmortem proteolysis in transgenic mice. Transgenic mice (n = 8) with a human calpastatin gene, whose expression was driven by the human skeletal muscle actin promoter, were killed along with control nontransgenic littermates (n = 5). Hind limbs were removed and stored at 4 degrees C, and muscle samples were dissected at 0, 1, 3, and 7 d postmortem and analyzed individually. At time 0, active human calpastatin was expressed in transgenic murine skeletal muscle at a level 370-fold greater (P < 0.001) than calpastatin in control mice. Although the native isoform of this protein was degraded with storage, at 7 d postmortem, approximately 78% of at-death activity remained, indicating that degraded calpastatin retains activity. Calpain (mu- and m-) expression was unaffected (P > 0.05) by the transgene as assessed by immunoreactivity at d 0. Over 7 d, 33% of at-death 80-kDa isoform immunoreactivity of mu-calpain was lost in transgenics compared to an 87% loss in controls, indicating that autolysis of mu-calpain was slowed in transgenic mice. Desmin degradation was also inhibited (P < 0.05) in transgenics when compared to controls. Control mice lost 6, 78, and 91% of at-death native desmin at 1, 3, and 7 d postmortem, respectively; conversely, transgenic mice lost only 1, 3, and 17% at the same times. A similar trend was observed when examining the degradation of troponin-T. Interestingly, m-calpain seemed to undergo autolysis in control mice, which in postmortem tissue is indicative of proteolysis. Further investigation revealed that both mu- and m-calpain are active postmortem in normal murine skeletal muscle. In conclusion, a high level of expression of active calpastatin was achieved, which, by virtue of its inhibitory specificity, was determined to be directly responsible for a decrease in postmortem proteolysis.     

Establishment of bipotent progenitor cell clone from rat skeletal muscle

The present study describes the isolation, cloning and characterization of adipogenic progenitor cells from rat skeletal muscle. Among the obtained 10 clones, the most highly adipogenic progenitor, 2G11 cells, were further characterized. In addition to their adipogenicity, 2G11 cells retain myogenic potential as revealed by formation of multinucleated myotubes when co‐cultured with myoblasts. 2G11 cells were resistant to an inhibitory effect of basic fibroblast growth factor on adipogenesis, while adipogenesis of widely used preadipogenic cell line, 3T3‐L1 cells, was suppressed almost completely by the same treatment. In vivo transplantation experiments revealed that 2G11 cells are able to possess both adipogenicity and myogenicity in vivo. These results indicate the presence of bipotent progenitor cells in rat skeletal muscle, and suggest that such cells may contribute to ectopic fat formation in skeletal muscle.     

Fbxw7β, E3 ubiquitin ligase,negative regulation of primary myoblast differentiation,proliferation and migration

Satellite cells attached to skeletal muscle fibers play a crucial role in skeletal muscle regeneration. During regeneration, the satellite cells proliferate, migrate to the damaged region, and fuse to each other. Although it is important to determine the cellular mechanisms controlling myoblast behavior, their regulators are not well understood. In this study, we evaluated the roles of Fbxw7 in primary myoblasts and determined its potential as a therapeutic target for muscle disease. We originally found that Fbxw7β, one of the E3 ubiquitin ligase Fbxw7 subtypes, negatively regulates differentiation, proliferation and migration of myoblasts and satellite cells on muscle fiber. However, these phenomena were not observed in myoblasts expressing a dominant‐negative, F‐box deleted Fbxw7β, mutant. Our results suggest that myoblast differentiation potential and muscle regeneration can be regulated by Fbxw7β.     

Increase in muscle endurance in mice by dietary Yamabushitake mushroom (Hericium erinaceus) possibly via activation of PPARδ

Skeletal muscle fiber is largely classified into two types: type 1 (slow‐twitch) and type 2 (fast‐twitch) fibers. Meat quality and composition of fiber types are thought to be closely related. Previous research showed that overexpression of constitutively active peroxisome proliferator‐activated receptor (PPAR)δ, a nuclear receptor present in skeletal muscle, increased type 1 fibers in mice. In this study, we found that hexane extracts of Yamabushitake mushroom (Hericium erinaceus) showed PPARδ agonistic activity in vitro. Eight‐week‐old C57BL/6J mice were fed a diet supplemented with 5% (w/w) freeze‐dried Yamabushitake mushroom for 24 hr. After the treatment period, the extensor digitorum longus (EDL) muscles were excised. The Yamabushitake‐supplemented diet up‐regulated the PPARδ target genes Pdk4 and Ucp3 in mouse skeletal muscles in vivo. Furthermore, feeding the Yamabushitake‐supplemented diet to mice for 8 weeks resulted in a significant increase in muscle endurance. These results indicate that Yamabushitake mushroom contains PPARδ agonistic ligands and that dietary intake of Yamabushitake mushroom could activate PPARδ in skeletal muscle of mice. Unexpectedly, we observed no significant alterations in composition of muscle fiber types between the mice fed control and Yamabushitake‐supplemented diets.     

Reduced dietary protein level influences the free amino acid and gene expression profiles of selected amino acid transceptors in skeletal muscle of growing pigs

This study was conducted to evaluate the effect of reduced dietary protein level on growth performance, muscle mass weight, free amino acids (FAA) and gene expression profile of selected amino acid transceptors in different fibre type of skeletal muscle tissues (longissimus dorsi, psoas major, biceps femoris) of growing pigs. A total of 18 cross‐bred growing pigs (Large White × Landrace × Duroc) with initial body weight (9.57 ± 0.67 kg) were assigned into three dietary treatments: 20% crude protein (CP) diet (normal recommended, NP), 17% CP diet (low protein, LP) and 14% CP diet (very low protein, VLP). The results indicated improved feed‐to‐gain ratio was obtained for pigs fed LP and NP diets (p < 0.01), while the pigs fed VLP diet showed the worst growth performance (p < 0.01). There was no significant difference in the weights of longissimus dorsi and psoas major muscle between LP and NP groups (p > 0.05). Majority of the determined FAA concentration of LP group were greater than or equal to those of NP group in both longissimus dorsi and psoas major muscle (p < 0.01). Further, the mRNA expression levels of sodium‐coupled neutral amino acid transceptor 2, L‐type amino acid transceptor 1 and proton‐assisted amino acid transceptors 2 were higher in skeletal muscle tissue in LP group compared to those of the pigs fed NP or VLP diet. These results suggested that reduced dietary protein level (3 points of percentage less than recommended level) would upregulate the mRNA expression of amino acid transceptors to enhance the absorption of FAA in skeletal muscle of growing pigs. There seems to be a relationship between response of AA transceptors to the dietary protein level in skeletal muscle tissue of different fibre type. To illustrate the underlying mechanisms will be beneficial to animal nutrition.     

Leucine‐induced promotion of post‐absorptive EAA utilization and hepatic gluconeogenesis contributes to protein synthesis in skeletal muscle of dairy calves

The high rate of protein synthesis in skeletal muscle of dairy calves can benefit their first lactation even lifetime milk yield. Since the rate of protein synthesis is relatively low in the post‐absorptive state, the aim of this research was to determine whether leucine supplementation could increase the post‐absorptive essential amino acid (EAA) utilization and protein synthesis in the skeletal muscle. Ten male neonatal dairy calves (38 ± 3 kg) were randomly assigned to either the control (CON, no leucine supplementation, n = 5) or supplementation with 1.435 g leucine/L milk (LEU, n = 5). Results showed that leucine significantly increased the length and protein concentration in longissimus dorsi (LD) muscle, whereas it decreased creatinine concentration and glutamic‐oxalacetic transaminase (GOT) activity. Compared to the control group, leucine supplementation also reduced the glutamic‐pyruvic transaminase (GPT) activity. Supplementation of leucine improved the phosphorylation of mammalian target of rapamycin (mTOR), eukaryotic initiation factor 4E‐binding protein 1 (4EBP1) and substrates ribosomal protein S6 kinase 1 (p70S6K). Supplementation of leucine resulted in increased concentrations of glucose, methionine, threonine, histidine and EAAs and decreased concentration of arginine in serum. Liver glucose concentration was higher and pyranic acid was lower in LEU compared to CON. In conclusion, leucine supplementation can promote post‐absorptive EAA utilization and hepatic gluconeogenesis, which contributes to protein synthesis in skeletal muscle of dairy calves.     

Classification of Involuntary Movements in Dogs: Myoclonus and Myotonia

Myoclonus is a sudden brief, involuntary muscle jerk. Of all the movement disorders, myoclonus is the most difficult to encapsulate into any simple framework. On the one hand, a classification system is required that is clinically useful to aid in guiding diagnosis and treatment. On the other hand, there is need for a system that organizes current knowledge regarding biological mechanisms to guide scientific research. These 2 needs are distinct, making it challenging to develop a robust classification system suitable for all purposes. We attempt to classify myoclonus as “epileptic” and “nonepileptic” based on its association with epileptic seizures. Myotonia in people may be divided into 2 clinically and molecularly defined forms: (1) nondystrophic myotonias and (2) myotonic dystrophies. The former are a group of skeletal muscle channelopathies characterized by delayed skeletal muscle relaxation. Many distinct clinical phenotypes are recognized in people, the majority relating to mutations in skeletal muscle voltage‐gated chloride (CLCN1) and sodium channel (SCN4A) genes. In dogs, myotonia is associated with mutations in CLCN1. The myotonic dystrophies are considered a multisystem clinical syndrome in people encompassing 2 clinically and molecularly defined forms designated myotonic dystrophy types 1 and 2. No mutation has been linked to veterinary muscular dystrophies. We detail veterinary examples of myotonia and attempt classification according to guidelines used in humans. This more precise categorization of myoclonus and myotonia aims to promote the search for molecular markers contributing to the phenotypic spectrum of disease. Our work aimed to assist recognition for these 2 enigmatic conditions.     

一日龄大通牦牛和平原黄牛骨骼肌显微结构的比较

为了探讨1日龄大通牦牛骨骼肌组织学特点及对低氧的适应,以平原黄牛为对照,利用光镜和计算机图像分析系统测定骨骼肌肌纤维直径、表面积密度;通过透射电镜比较骨骼肌线粒体的面数密度、面积密度、体积密度、平均体积等结构参数。结果显示,1日龄大通牦牛骨骼肌肌纤维直径显著细于1日龄平原黄牛,表面积密度明显大于平原黄牛,差异极显著(P<0.01);1日龄大通牦牛骨骼肌细胞中线粒体平均体积小于1日龄平原黄牛,并具有极显著差异(P<0.01);而1日龄大通牦牛骨骼肌细胞中线粒体体积密度、面积密度、面数密度均大于1日龄平原黄牛,且差异极显著(P<0.01)。以上结果表明,大通牦牛通过增加骨骼肌线粒体面数密度、面积密度、体积密度,降低线粒体平均体积来提高其在低氧环境中对氧的利用,并且在长期进化中形成了肌纤维直径小,表面积密度大的组织学特点。     

Dietary thymol supplementation promotes skeletal muscle fibre type switch in longissimus dorsi of finishing pigs

As one of the key points related to meat quality, skeletal muscle fibre type is determined by energy metabolism and genetic factors, but its transformation could be also greatly influenced by many factors. Thymol, the primary effective ingredients of thyme, is well known for its anti-oxidation and anti-inflammatory, while little is known about its effect on skeletal muscle oxidative metabolism and fibre type switch. Therefore, in order to investigate its effects and possibility to be applied in livestock production, 36 150-day-old fattening Pigs were fed with different diet for six-week experiment. As a result, the drip loss ratio of longissimus dorsi (LD) was significantly reduced (p < .05). Oxidative metabolism-related enzyme activity, the mRNA levels and protein expression of COX5B and PGC1α, mRNA level of myosin heavy chain I (MyHC I) and protein level of MyHC IIa were significantly upregulated (p < .05). While compared with control group, the protein expression of MyHC IIb was significantly decreased (p < .05). The result revealed that thymol could promote the oxidative metabolism in the muscle of pigs and improve the meat quality to a certain extent.