Involvement of ryanodine receptor in skeletal muscle fatigue / 体力科学

Ryanodine receptors (RyRs) are tetrameric Ca2+ release channels of sarcoplasmic reticulum (SR). This review attempts to detail the key mechanism of RyR channel gating and to discuss the hypothesis that skeletal muscle fatigue, defined as reduced force production, would result from functional changes in both individual RyR channel opening and coupling among RyR channels. Previous studies have shown that RyR channels in skeletal muscle open simultaneously, called coupled gating, because of physical interaction among channels. In this review, mechanisms underlying muscle fatigue are discussed with consideration of the coupling effect. Fatigue mechanisms are thought to be different between acute exercise and long-term exercise training. The impairments in individual channel opening and coupling between RyR channels can occur after acute exercise, leading to decreased SR Ca2+ release and force depression. On the contrary, during long-term exercise training, individual channel opening would be enhanced but coupling between channels would be impaired. If this were to continue for long periods, SR Ca2+ content would reduce, leading to less Ca2+ release and lower force production.

Clinical, pathological, imaging and genetic analysis of two cases of central core disease with different inheritance modes / 中国神经精神疾病杂志

Objective To study the clinical, pathological, imaging features of two cases of central core disease (CCD) with different inheritance and to explore the similarities and differences between autosomal recessive CCD (AR-CCD) and autosomal dominant CCD (AD-CCD). Methods Clinical manifestations, family history, muscle MRI and muscle biopsy were collected. Targeted next generation sequencing (NGS) and sanger sequencing were applied for genetic analysis. Co-segregation analysis was further conducted in one family. Results Their common clinical manifestations included childhood early-onset proximal limbs muscle weakness and dystrophy accompanied with facial involvement. The MRI revealed extensive muscular dystrophy and fatty filtration in the both thighs, but not in rectus femoris. Pathology of skeletal muscle showed typical central cores in type Ⅰ muscle fibers and eccentric cores only in AR-CCD. Targeted NGS identified 3 missense mutations in RYR1, including one novel mutation. Conclusion The present study has described clinical and pathological features of two typical CCD patients with different inheritance, which may be associated with the different mutations in RYR1 gene. Targeted NGS apparently improves the genetic diagnosis of CCD.

Mild Clinical Features and Histopathologically Atypical Cores in Two Korean Families with Central Core Disease Harboring RYR1 Mutations at the C-Terminal Region

BACKGROUND: Central core disease (CCD) is a congenital myopathy characterized by distinctive cores in muscle fibers. Mutations in the gene encoding ryanodine receptor 1 (RYR1) have been identified in most CCD patients. CASE REPORT: Two unrelated patients presented with slowly progressive or nonprogressive proximal muscle weakness since childhood. Their family history revealed some members with the same clinical problem. Histological analysis of muscle biopsy samples revealed numerous peripheral cores in the muscle fibers. RYR1 sequence analysis disclosed a novel mutation in exon 101 (c.14590T>C) and confirmed a previously reported mutation in exon 102 (c.14678G>A). CONCLUSIONS: We report herein two families with CCD in whom missense mutations at the C-terminal of RYR1 were identified. Although it has been accepted that such mutations are usually associated with a severe clinical phenotype and clearly demarcated central cores, our patients exhibited a mild clinical phenotype without facial muscle involvement and skeletal deformities, and atypical cores in their muscle biopsy specimens.

Effects of Aerobic Exercise on Calcium Release Related Genes Expression in Sarcoplasmic Reficulum of Skeletal Muscle in Mice / 中国运动医学杂志

Objective To study the effects of 6-week aerobic treadmill exercise on the genes expression in skeletal muscle of C57BL/6 mice.Gene array was performed and the data was analyzed to evaluate the adaptive changes at gene level caused by exercise.Methods Twenty male C57BL/6 mice were randomly divided into two groups:control group(C) and aerobic exercise group (E).The mice from group E were forced to run on treadmill for 6 weeks.After 6 weeks,all mice were fasted for 16 hours,and then sacrificed.Their flexor muscle was removed.4 samples from each group were analyzed with gene chips to dissect the differentially expressed genes between the two groups.Results Our results showed that 723 genes were differentially expressed in E group as compared with C group after the 6 weeks aerobic exercise,among which 510 genes were up-and 213 down-regulated.There were 6 differentially expressed calcium signaling genes and 2 ofwhich(Gnall and Pdgfra) were up-regulated,while the others(Phka1,Picd4,RYR1 and Ppid)were down regulated.