The fiber type transition of skeletal muscle is an intricate and essential physiological process in the body, significantly influencing both the function and metabolism of skeletal muscle. This phenomenon is not only affected by external environmental changes but also intricately regulated by internal physiological mechanisms. Therefore, exploring the physiological process of muscle fiber type transition holds considerable significance for the treatment of human neuromuscular disorders and the improvement of meat quality in livestock and poultry. It has been discovered that the cytokines secreted by skeletal muscle, i.e., myokines, play a role in the fiber type transition of skeletal muscle. Myokines mainly act on skeletal muscle in autocrine and paracrine forms to participate in signal transduction and regulate the fiber type transition of skeletal muscle. This paper reviews the functional differences among various muscle fiber types, expounds the effects and mechanisms of myokines in regulating the transition processes of these fiber types, and prospects the future research directions in this field. This review is expected to provide theoretical support for enhancing the meat quality of livestock and poultry and treating skeletal muscle-related diseases.
Humans ; Animals ; Cytokines/metabolism* ; Muscle Fibers, Skeletal/metabolism* ; Muscle, Skeletal/metabolism* ; Signal Transduction ; Muscle Fibers, Slow-Twitch/metabolism* ; Muscle Fibers, Fast-Twitch/metabolism* ; Myostatin/metabolism* ; Myokines

In an attempt to clarify the function of the suboccipital muscles, we performed morphological observation of the suboccipital muscles for variations in the muscle belly and compared the morphology of their muscle fibers in terms of cross-sectional area by immunostaining with anti-myosin heavy chain antibodies. The cadavers of 25 Japanese individuals were used: 22 for morphological examinations and three for histological examinations. Among samples of the rectus capitis posterior major muscle (RCPma) and rectus capitis posterior minor muscle (RCPmi), 86.4% had a typical muscle appearance with a single belly, and 13.6% had an anomalous morphology. None of the samples of the obliquus capitis superior (OCS) or obliquus capitis inferior (OCI) muscles had an anomalous appearance. Measurement of cross-sectional area revealed that fast-twitch muscle fibers in the RCPma and OCI had a significantly greater cross-sectional area than those of the RCPmi and OCS. The cross-sectional area of intermediate muscle fibers was also significantly greater in the OCS than in the RCPma, RCPmi, and OCI. The cross-sectional area of slow-twitch muscle fibers was significantly greater in the OCS than in the RCPma, RCPmi, and OCI, and the RCPmi showed a significantly greater cross-sectional area for slow-twitch muscle fibers than did the RCPma, and OCI. Our findings indicate that the RCPmi and OCS exert a greater force than the RCPma and OCI, and act as anti-gravity agonist muscles of the head. Prolonged head extension in individuals with anomalous suboccipital muscle groups could result in dysfunction due to undue stress.
Antibodies ; Asian Continental Ancestry Group ; Cadaver ; Classification* ; Head ; Headache ; Humans ; Muscle Fibers, Fast-Twitch ; Muscle Fibers, Slow-Twitch ; Muscles

OBJECTIVETo explore the relationship between contractile characteristics and fiber type conversion in hind-limb unloading mice soleus.

METHODSAfter 28-day hind-limb unloading and muscle atrophy, we used the method of isolated muscle perfusion with different stimulated protocols to determine the changes in contractile characteristics including the isometric twitch force and tetanus force and fatigue index of slow twitch muscle in mice. The muscle myofibrillar composition and fiber type conversion were detected by immunofluorescence staining and real-time PCR.

RESULTSThe isometric twitch force and the tetanus force and fatigue index were decreased progressively in 28-day unloaded mice soleus, with the increase in fast twitch fiber subtype and the decrease in slow twitch fiber subtype.

CONCLUSIONThe alteration of contractile characteristics is relevant to the slow-to-fast fiber conversion in mice soleus after 28-day hind-limb unloading.

Animals ; Hindlimb Suspension ; physiology ; Mice ; Mice, Inbred C57BL ; Muscle Contraction ; physiology ; Muscle Fatigue ; physiology ; Muscle Fibers, Fast-Twitch ; physiology ; Muscle Fibers, Slow-Twitch ; physiology ; Muscle, Skeletal ; pathology ; physiology ; Muscular Atrophy

PURPOSE: The purpose of this study was to determine the effect of dehydroepiandrosterone (DHEA) on recovery of muscle atrophy induced by Parkinson's disease. METHODS: The rat model was established by direct injection of 6-hydroxydopamine (6-OHDA, 20 microg) into the left striatum using stereotaxic surgery. Rats were divided into two groups; the Parkinson's disease group with vehicle treatment (Vehicle; n=12) or DHEA treatment group (DHEA; n=22). DHEA or vehicle was administrated intraperitoneally daily at a dose of 0.34 mmol/kg for 21 days. At 22-days after DHEA treatment, soleus, plantaris, and striatum were dissected. RESULTS: The DHEA group showed significant increase (p<.01) in the number of tyrosine hydroxylase (TH) positive neurons in the lesioned side substantia nigra compared to the vehicle group. Weights and Type I fiber cross-sectional areas of the contralateral soleus of the DHEA group were significantly greater than those of the vehicle group (p=.02, p=.00). Moreover, extracellular signal-regulated kinase (ERK) phosphorylation significantly decreased in the lesioned striatum, but was recovered with DHEA and also in the contralateral soleus muscle, Akt and ERK phosphorylation recovered significantly and the expression level of myosin heavy chain also recovered by DHEA treatment. CONCLUSION: Our results suggest that DHEA treatment recovers Parkinson's disease induced contralateral soleus muscle atrophy through Akt and ERK phosphorylation.
Animals ; Corpus Striatum/drug effects/metabolism ; Dehydroepiandrosterone/*pharmacology/therapeutic use ; Extracellular Signal-Regulated MAP Kinases/metabolism ; Male ; Muscle Fibers, Slow-Twitch/drug effects ; Muscle, Skeletal/drug effects/metabolism ; Muscular Atrophy/drug therapy/*etiology/*pathology ; Myosins/metabolism ; Neurons/drug effects/enzymology ; Oxidopamine/toxicity ; Parkinson Disease, Secondary/*chemically induced/*complications ; Phosphorylation ; Proto-Oncogene Proteins c-akt/metabolism ; Rats ; Rats, Sprague-Dawley ; Tyrosine 3-Monooxygenase/metabolism

Atrophy ; Brain ; pathology ; Child ; Female ; Humans ; Muscle Fibers, Slow-Twitch ; pathology ; Neuromuscular Diseases ; congenital ; pathology

Akt, a key protein of cell survival, can promote cell growth and survival by activations of various cellular protective factors. Ischemic preconditioning (IP) has been known to reduce ischemic injury through upregulation of phosphorylation of Akt (p-Akt). CuZn-superoxide dismutase (SOD-1), an antioxidant enzyme, scavenges reactive oxygen species and protects cell from oxidative stress by increasing the activaiton of Akt. The present study was performed to examine the effects of IP on the expression of p-Akt and SOD-1 in the ischemicreperfused rat skeletal muscles. Thirty weeks old male SD rats were divided into 4 groups, such as controls, IP, 4 hour ischemia and 4 hour ischemia with IP. For IP, commom iliac artery was occluded three times for 5 min ischemia followed by 5 min reperfusion using rodent vascular clamps. Ischemia was induced by occlusion on the same artery for 4 hours. The Tibialis anterior and Soleus were removed at 0, 1, 3, and 24 hours of reperfusion. The expressions of p-Akt (Ser 473) and SOD-1 were examined with immunohistochemistry and Western blot analysis.In the IP group, the p-Akt and SOD-1 were increased, compared to the control group. In the ischemia group, the p- Akt and SOD-1 were decreased, compared to the control group, and were more abundant when reperfusion time were increased. IP increased the p-Akt and SOD-1 after 4 hour ischemia, and the p-Akt and SOD-1 were higher in Soleus compared to Tibialis anterior. These findings suggest that IP increases p-Akt and expression of SOD-1 in the ischemic-reperfused rat skeletal muscles, and that upregulations of p-Akt and SOD-1 induced by IP were higher in the red muscle fiber, Soleus, than the white muscle fiber, Tibialis anterior.
Animals ; Arteries ; Blotting, Western ; Cell Survival ; Humans ; Iliac Artery ; Immunohistochemistry ; Ischemia ; Ischemic Preconditioning ; Male ; Muscle Fibers, Fast-Twitch ; Muscle Fibers, Slow-Twitch ; Muscle, Skeletal ; Oxidative Stress ; Phosphorylation ; Rats ; Reactive Oxygen Species ; Reperfusion ; Rodentia ; Up-Regulation

The elevated plasma level of thyroxin and/or triiodothyronine in hyperthyroidism not only induces a transition from the innervated slow-twitch muscle fibers to fast-twitch fibers, but also changes the contractile function in transition muscle fibers. So the muscle weakness of thyrotoxic myopathy would relate to alteration in fatigability of tetanic contraction in muscles, especially in slow-twitch fibers. The aim of the present study was to observe the extent of fatigue of soleus in 4-week hyperthyroid rats and elucidate its underlying mechanism. The isolated soleus muscle strips were perfused in Krebs-Henseleit solution with or without an inhibitor of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA), cyclopiazonic acid (CPA). The contractile function of soleus was observed in twitch and intermittent tetanic contraction. The body weight in 4-week hyperthyroid rats decreased as compared with that in the control group [(292±13) g vs (354±10) g], but there was no difference between hyperthyroid and control groups in the wet weight of soleus [(107.3±8.6) mg vs (115.1±6.9) mg]. The time to peak tension (TPT) and time from peak tension to 75% relaxation (TR(75)) in twitch contraction were shortened in the soleus of hyperthyroid rats, and the TR(75) of tetanic contraction was also shortened as compared with that in the control group [(102.8±4.1) ms vs (178.8±15.8) ms]. The optimal stimulation frequency at which a maximal tension of tetanic contraction happened was shifted from 100 Hz in the control group to 140 Hz in hyperthyroid group. The soleus of hyperthyroid rat was easier to fatigue than that of the control rat during intermittent tetanic contraction. The SERCA activity also increased in soleus of hyperthyroid rat. The TR(75) in tetanic contraction was prolonged and showed an increased fatigue resistance in the soleus of control and hyperthyroid groups treated with 1.0 μmol/L CPA. The fatigue resistance of tetanic contraction in the soleus of hyperthyroid rat increased further with 5.0 μmol/L CPA treatment, but the resting tension kept rising. The 10 μmol/L CPA reduced the fatigue resistance of tetanic contraction in the soleus of hyperthyroid rat. The above results demonstrate that the SERCA activity in soleus can also influence the relaxation duration of twitch contraction like that in the myocardium. The SERCA activity in slow-twitch fibers is possibly involved in the regulation of fatigue resistance of intermittent tetanic contraction.
Animals ; Fatigue ; Glucose ; Hyperthyroidism ; enzymology ; In Vitro Techniques ; Muscle Contraction ; Muscle Fibers, Slow-Twitch ; enzymology ; physiology ; Muscle, Skeletal ; enzymology ; physiology ; Rats ; Sarcoplasmic Reticulum Calcium-Transporting ATPases ; metabolism ; Tromethamine

OBJECTIVETo observe the change of the muscular fiber phynotype at different condition of nerve injury.

METHODSRabbits were used as an animal model in this study. The trigeminus and facial nerves of the animal were simultaneously severed (group 1) or only the latter was severed (group 2). The morphologic change of the muscular fibers was observed with histochemical methods; the tension of contraction and the threshold value of electrical stimulation were observed with electrical physiological methods.

RESULTSTrigeminus nerve play an important role in delaying muscular atrophy after facial nerve was severed. The atrophy degree of type II a and II b muscular fibers was less in group 2 than that in group 1. The change of type 1 muscular fibers was not affected by trigeminus nerve. New muscular fibers emerged in group 2. The tension of contraction and the threshold value of electrical stimulation were better in group 2 than that of in group 1.

CONCLUSIONSSensory nerve could delay muscle atrophy after denervation. Sensory nerve should be repaired simultaneously when the motor nerve was sutured. The results of this study would facilitate clinical treatment for facial palsy.

Animals ; Denervation ; Disease Models, Animal ; Facial Nerve ; Facial Nerve Diseases ; pathology ; Female ; Muscle Fibers, Skeletal ; pathology ; Muscle Fibers, Slow-Twitch ; pathology ; Rabbits

OBJECTIVETo study the effect of testosterone propionate (TP) on the distribution pattern of calcitonin gene-related peptide (CGRP) in two types of motoneuron (Mn) pools in rats.

METHODThe double labeling of cholera toxin B subunit coupled with colloidal gold (CB-Au) retrograde identification combining with immunocytochemistry was mainly used to reveal the distribution pattern of CGRP-like immunoreactivity (CGRP-LI) and its changes in the motoneuron pools labeled by CB-Au.

RESULTTP injected intramuscularly 28 days later significantly decreased CGRP expression in Mn pool innervating extensor digitorum longus (EDL, fast-twitch), comparing with corresponding control and castration group respectively (P < 0.001), while no significant effect on Mn pools innervating soleus (SOL, slow-twitch, P > 0.05) was observed.

CONCLUSIONEDL-Mn pool is more sensitive to testosterone propionate than SOL-Mn pool in regulating CGRP expression.

Animals ; Calcitonin Gene-Related Peptide ; drug effects ; metabolism ; Male ; Motor Neurons ; drug effects ; metabolism ; Muscle Fibers, Fast-Twitch ; cytology ; drug effects ; Muscle Fibers, Slow-Twitch ; cytology ; drug effects ; Rats ; Rats, Wistar ; Testosterone Propionate ; pharmacology

Congenital neuromuscular disease with uniform type 1 fiber (CNMDU1) is a rare but distinct form of nonprogressive, congenital myopathy. CMNDU1 is characterized by a type 1 muscle fiber content of more than 99%. This condition has only been previously described in a few reports. The authors report an 11-year-old girl who exhibited delayed developmental milestones, proximal muscle weakness, and bilateral ptosis. Her serum creatine kinase level was normal but an electromyographic study showed myopathic changes. A biopsy specimen from the left deltoid muscle revealed a uniformity of type 1 fibers (greater than 99%) with a moderate variation in fiber size. This is the first case of CNMDU1 reported in Korea.
Biopsy ; Child ; Developmental Disabilities/*pathology ; Female ; Human ; Muscle Fibers, Slow-Twitch/*pathology ; Muscle, Skeletal/*pathology ; Neuromuscular Diseases/congenital/*pathology