A case of dilated cardiomyopathy caused by FHL2 gene variant and a literature review / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical phenotype and genetic features of a child with dilated cardiomyopathy (DCM).@*METHODS@#Clinical data of the child who had presented at the Zhengzhou Children's Hospital on April 28, 2020 was collected. Trio-whole exome sequencing (trio-WES) was carried out for the child and her parents, and candidate variants were validated by Sanger sequencing. "FHL2" was taken as the key word to retrieve related literature from January 1, 1997 to October 31, 2021 in the PubMed database and was also searched in the ClinVar database as a supplement to analyze the correlation between genetic variants and clinical features.@*RESULTS@#The patient was a 5-month-old female infant presented with left ventricular enlargement and reduced systolic function. A heterozygous missense variant c.391C>T (p.Arg131Cys) in FHL2 gene was identified through trio-WES. The same variant was not detected in either of her parents. A total of 10 patients with FHL2 gene variants have been reported in the literature, 6 of them had presented with DCM, 2 with hypertrophic cardiomyopathy (HCM), and 2 with sudden unexplained death (SUD). Phenotypic analysis revealed that patients with variants in the LIM 3 domain presented hypertrophic cardiomyopathy and those with variants of the LIM 0~2 and LIM 4 domains had mainly presented DCM. The c.391C>T (p.Arg131Cys) has been identified in a child with DCM, though it has not been validated among the patient's family members. Based on the guidelines of the American College of Medical Genetics and Genomics, the c.391C>T(p.Arg131Cys) variant was re-classified as likely pathogenic (PS2+PM2_Supporting+PP3+PP5).@*CONCLUSION@#The heterozygous missense variant of c.391C>T (p.Arg131Cys) in the FHL2 gene probably predisposed to the DCM in this child, which has highlighted the importance of WES in the clinical diagnosis and genetic counseling.

Effects of high-intensity gymnastics on skeletal muscle proteins / Efeitos da ginástica de alta intensidade sobre as proteínas musculares esqueléticas / Efectos de la gimnasia de alta intensidad en las proteínas musculares esqueléticas

ABSTRACT Introduction: Although the current method of muscle stretching in gymnastics teaching in colleges and universities can reduce sports fatigue, it has been shown to have little effect on the well-being of athletes because it requires a long recovery time from psychological fatigue. Progressive muscle relaxation training is a method that uses the basic principle of sympathetic nerve activity to reduce the impact of negative emotions psychologically and relieve fatigue physiologically, requiring a further study of its impact on muscle protein. Objective: Explore the effect of high-intensity gymnastics on skeletal muscle protein and study the progressive muscle relaxation training method post-workout adjustment. Methods: After three weeks of training, excluding the standard deviations in the experimental data caused by the athletes' irregular movements, the athletes' blood lactate content and heart rate were counted and recorded. The collected data were analyzed using Excel software to integrate and compare the data using the T-test method. Results: After exercise training, the skeletal muscle function indices of the subjects increased to different degrees. From the point of view of heart rate recovery efficiency, the rate of heart rate decline of progressive relaxation training was higher than that of the two groups, and the degree of fluctuation was lower than that of the two groups, indicating that the level of recovery in heart rate of progressive relaxation training was better. Conclusion: The action of the high-intensity gymnastics team has a good effect on improving the athletes' skeletal muscle and skeletal muscle proteins. Post-exercise conditioning training plays an important role in athletes' physical recovery. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

RESUMO Introdução: Embora o método de alongamento muscular atual no ensino de ginástica em faculdades e universidades consiga reduzir a fadiga esportiva, tem se mostrado pouco eficaz no bem-estar dos atletas por exigir grande tempo de recuperação da fadiga psicológica. O treinamento progressivo de relaxamento muscular é um método que usa o princípio básico da atividade nervosa simpática para reduzir o impacto das emoções negativas psicologicamente e aliviar a fadiga fisiologicamente, necessitando de mais estudos do seu impacto sobre a proteína muscular. Objetivo: Explorar o efeito da ginástica de alta intensidade sobre as proteínas musculares esqueléticas e estudar o método de treinamento progressivo de relaxamento muscular no ajuste pós-treino. Métodos: Após 3 semanas de treinamento, excluídos os desvios-padrão nos dados experimentais causados pelos movimentos irregulares dos atletas, foram contabilizados e registrados os conteúdos de lactato sanguíneo e frequência cardíaca dos atletas. Analisou-se os dados coletados, com o software Excel, para integrar e comparar os dados pelo método de teste-T. Resultados: Após o treinamento do exercício, os índices de função muscular esquelética dos sujeitos aumentaram em diferentes graus. Do ponto de vista da eficiência da recuperação da frequência cardíaca, a taxa de declínio da frequência cardíaca do treinamento de relaxamento progressivo foi maior do que a dos dois grupos, o grau de flutuação foi menor do que o dos dois grupos, indicando que o nível de recuperação na frequência cardíaca do treinamento de relaxamento progressivo foi melhor. Conclusão: A ação da equipe de ginástica de alta intensidade tem um bom efeito na melhoria do músculo esquelético e das proteínas musculares esqueléticas dos atletas. O treinamento de condicionamento pós-exercício desempenha um papel importante na recuperação física dos atletas. Nível de evidência II; Estudos terapêuticos - investigação dos resultados do tratamento.

RESUMEN Introducción: Aunque el método actual de elongación muscular en la enseñanza de la gimnasia en colegios y universidades consigue reducir la fatiga deportiva, se ha demostrado que tiene poco efecto en el bienestar de los atletas porque requiere un largo tiempo de recuperación de la fatiga psicológica. El entrenamiento de la relajación muscular progresiva es un método que utiliza el principio básico de la actividad nerviosa simpática para reducir el impacto de las emociones negativas desde el punto de vista psicológico y aliviar la fatiga desde el punto de vista fisiológico, lo que requiere un estudio más profundo de su impacto en la proteína muscular. Objetivo: Explorar el efecto de la gimnasia de alta intensidad sobre la proteína del músculo esquelético y estudiar el método de entrenamiento de relajación muscular progresiva en el ajuste posterior al entrenamiento. Métodos: Después de 3 semanas de entrenamiento, excluyendo las desviaciones estándar en los datos experimentales causadas por los movimientos irregulares de los atletas, se contó y registró el contenido de lactato en sangre y la frecuencia cardíaca de los atletas. Los datos recogidos se analizaron, con el programa informático Excel, para integrar y comparar los datos mediante el método de la prueba T. Resultados: Tras el entrenamiento con ejercicios, los índices de función del músculo esquelético de los sujetos aumentaron en diferentes grados. Desde el punto de vista de la eficacia de la recuperación de la frecuencia cardíaca, el índice de disminución de la frecuencia cardíaca del entrenamiento de relajación progresiva fue mayor que el de los dos grupos, el grado de fluctuación fue menor que el de los dos grupos, lo que indica que el nivel de recuperación de la frecuencia cardíaca del entrenamiento de relajación progresiva fue mejor. Conclusión: La acción del equipo de gimnasia de alta intensidad tiene un buen efecto en la mejora del músculo esquelético y de las proteínas del músculo esquelético de los atletas. El entrenamiento de acondicionamiento posterior al ejercicio desempeña un papel importante en la recuperación física de los deportistas. Nivel de evidencia II; Estudios terapéuticos - investigación de los resultados del tratamiento.

Kindlin-2 loss in condylar chondrocytes causes spontaneous osteoarthritic lesions in the temporomandibular joint in mice / 国际口腔科学杂志·英文版

The progressive destruction of condylar cartilage is a hallmark of the temporomandibular joint (TMJ) osteoarthritis (OA); however, its mechanism is incompletely understood. Here, we show that Kindlin-2, a key focal adhesion protein, is strongly detected in cells of mandibular condylar cartilage in mice. We find that genetic ablation of Kindlin-2 in aggrecan-expressing condylar chondrocytes induces multiple spontaneous osteoarthritic lesions, including progressive cartilage loss and deformation, surface fissures, and ectopic cartilage and bone formation in TMJ. Kindlin-2 loss significantly downregulates the expression of aggrecan, Col2a1 and Proteoglycan 4 (Prg4), all anabolic extracellular matrix proteins, and promotes catabolic metabolism in TMJ cartilage by inducing expression of Runx2 and Mmp13 in condylar chondrocytes. Kindlin-2 loss decreases TMJ chondrocyte proliferation in condylar cartilages. Furthermore, Kindlin-2 loss promotes the release of cytochrome c as well as caspase 3 activation, and accelerates chondrocyte apoptosis in vitro and TMJ. Collectively, these findings reveal a crucial role of Kindlin-2 in condylar chondrocytes to maintain TMJ homeostasis.

Changes in gene expression of adipose tissue CD14 / 中南大学学报(医学版)

OBJECTIVES@#To study the gene expression of adipose tissue CD14@*METHODS@#The data of GSE54350 were obtained from the public database of gene expression profiling. The data were pre-processed by Network Analyst, String 11.0, Cytoscape 3.7.1, and other analytical software. The differentially expressed genes were analyzed by gene ontology biological function and kyoto encycopedia of genes and genomes (KEGG) signaling pathway to establish differential gene protein interaction network, transcription factor-gene regulatory network, microRNA-gene regulatory network, environmental factors-gene regulatory network, and other interaction systems.@*RESULTS@#The gene expression pattern of CD14@*CONCLUSIONS@#The gene expression of adipose tissue CD14

Effect of the regulator of G-protein signaling 2 on the proliferation and invasion of oral squamous cell carcinoma cells and its molecular mechanism / 华西口腔医学杂志

OBJECTIVES@#This study aims to investigate the effect of the regulator of G-protein signaling 2 (RGS2) on the proliferation and invasion of oral squamous cell carcinoma (OSCC) cells and its potential molecular mechanism. Metho⁃ds The expression status and clinical significance of RGS2 in head and neck squamous cell carcinomas and matched adjacent normal tissues were evaluated using TCGA database. Three OSCC cell lines (i.e., SCC-9, Cal27, and Fadu) were overexpressed with RGS2, and the effect of RGS2 on cell proliferation and invasion was determined using the Transwell, clone formation, and cell counting kit (CCK)-8 assays. Moreover, the yeast two-hybrid scree-ning and co-immunoprecipitation (Co-IP) assays were conducted to detect the correlation of RGS2, four and a half LIM domains protein 1 (FHL1), and damage DNA-binding protein 1 (DDB1).@*RESULTS@#The expression level of RGS2 in OSCC was significantly lower than that in matched adjacent normal tissues (@*CONCLUSIONS@#RGS2 plays an important role in the inhibition of OSCC proliferation and invasion. The structure stability of RGS2 is competitively regulated by FHL1 and DDB1.

Roles of smooth muscle 22α in vascular homeostasis and vascular remodeling / 生理学报

The research on the molecular mechanism of vascular injury has been a hot topic in recent years since the mechanism can be targeted for the treatment of vascular injury diseases. A large number of studies have found that vascular injury, repair and pathological remodeling are closely related to phenotype switching, abnormal proliferation and migration, and apoptosis of vascular smooth muscle cells (VSMCs). Smooth muscle 22α (SM22α) is a shape change and transformation sensitive F-actin-binding protein. SM22α decorates the contractile filament bundles within cultured VSMCs exhibiting differentiated phenotypes. In addition, SM22α is involved in regulation of cell signaling pathways related to vascular homeostasis and vascular remodeling. Here, we reviewed the recent research progress of SM22α in vascular homeostasis and remodeling.

Bioprospection of proteases from Halobacillus andaensis for bioactive peptide production from fish muscle protein

BACKGROUND: Biologically active peptides produced from fish wastes are gaining attention because their health benefits. Proteases produced by halophilic microorganisms are considered as a source of active enzymes in high salt systems like fish residues. Hence, the aim of this study was the bioprospection of halophilic microorganisms for the production of proteases to prove their application for peptide production. RESULTS: Halophilic microorganisms were isolated from saline soils of Mexico and Bolivia. An enzymatic screening was carried out for the detection of lipases, esterases, pHB depolymerases, chitinases, and proteases. Most of the strains were able to produce lipases, esterases, and proteases, and larger hydrolysis halos were detected for protease activity. Halobacillus andaensis was selected to be studied for proteolytic activity production; the microorganism was able to grow on gelatin, yeast extract, skim milk, casein, peptone, fish muscle (Cyprinus carpio), and soy flour as protein sources, and among these sources, fish muscle protein was the best inducer of proteolytic activity, achieving a protease production of 571 U/mL. The extracellular protease was active at 50°C, pH 8, and 1.4 M NaCl and was inhibited by phenylmethylsulfonyl fluoride. The proteolytic activity of H. andaensis was used to hydrolyze fish muscle protein for peptide production. The peptides obtained showed a MW of 5.3 kDa and a radical scavenging ability of 10 to 30% on 2,2-diphenyl-1-picrylhydrazyl and 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and a ferric reducing ability of plasma. Conclusion: The use of noncommercial extracellular protease produced by H. andaensis for biologically active peptide production using fish muscle as the protein source presents a great opportunity for high-value peptide production.

Síndrome miasténico congénito por deficiencia de rapsina: reporte de caso con nueva mutación y heterocigosidad compuesta / Congenital myasthenic syndrome due to rapsyn deficiency: A case report with a new mutation and compound heterozygosity

INTRODUCCIÓN Los síndromes miasténicos congénitos son un grupo heterogéneo de desórdenes genéticos, caracterizados por una transmisión sináptica anormal en la placa neuromuscular. REPORTE Presentamos el caso de un paciente de dos años, varón, con hipotonía, ptosis palpebral y debilidad simétrica y de predominio proximal, características que aparecieron desde el nacimiento y que motivaron varias hospitalizaciones por neumonía e insuficiencia ventilatoria. Desde el inicio de la deambulación a los dos años, los padres notaron que la debilidad empeoraba por las tardes y con la actividad física repetida o prolongada. El examen físico a los dos años mostró ptosis palpebral, debilidad de predominio proximal y fatigabilidad con el esfuerzo sostenido. La electro-miografía evidenció decremento del 27% en el potencial de acción muscular compuesto. El análisis de tríos mostró heterocigosis compuesta por transmisión de dos mutaciones diferentes en el gen de rapsina, una ya conocida procedente del padre y la otra no reportada previa-mente, procedente de la madre. El paciente recibió piridostigmina obteniendo mejoría inmediata y logrando un desempeño óptimo en actividades escolares, deportivas y de la vida cotidiana. A la fecha, no ha presentado nuevos episodios de insuficiencia ventilatoria. CONCLUSIONES La debilidad de inicio neonatal y la fatigabilidad o agotamiento con el esfuerzo sostenido, con afección principalmente de los músculos con inervación troncal y con un decremento mayor al 10% en el potencial de acción muscular compuesto en la electromiografía, deben hacer sospechar en un síndrome miasténico congénito. Se revisan los puntos clínicos clave que permiten establecer el diagnóstico oportuno y las opciones de tratamiento efectivo para algunos de estos síndromes.

INTRODUCTION The congenital myasthenic syndromes are a heterogeneous group of genetic disorders characterized by an abnormal synaptic transmission in the neuromuscular plate. REPORT We present a two-year-old patient, male, with hypotonia, palpebral ptosis, and proximal symmetric weakness with a neonatal onset that motivated several and prolonged hospitalizations for pneumonia and respiratory failure. From two years of age, the parents noticed that the facial and general weakness worsened in the afternoons and with repeated or prolonged physical activity. The physical examination showed palpebral ptosis, predominantly proximal weakness, and fatigability with sustained muscular effort. The electromyography showed a 27% decrement in the Compound Muscular Action Potential and the case-parents genetic study showed compound heterozygosity with the transmission of two different mutations in the rapsyn gene from both parents. The patient received pyridostigmine with great improvement, achieving optimal performance in school, sports, and daily life activities. CONCLUSIONS Weakness and fatigability with neonatal onset, mainly affecting the muscles with brain stem innervation and the decrement greater than 10 percent in the Compound Muscular Action Potential in the electromyographic studies, should make us suspect in a congenital myasthenic syndrome. We review the literature and key clinical points to establish a timely diagnosis and effective treatment in some of these syndromes.

The E3 ligase MuRF2 plays a key role in the functional capacity of skeletal muscle fibroblasts

Fibroblasts are a highly heterogeneous population of cells, being found in a large number of different tissues. These cells produce the extracellular matrix, which is essential to preserve structural integrity of connective tissues. Fibroblasts are frequently engaged in migration and remodeling, exerting traction forces in the extracellular matrix, which is crucial for matrix deposition and wound healing. In addition, previous studies performed on primary myoblasts suggest that the E3 ligase MuRF2 might function as a cytoskeleton adaptor. Here, we hypothesized that MuRF2 also plays a functional role in skeletal muscle fibroblasts. We found that skeletal muscle fibroblasts express MuRF2 and its siRNA knock-down promoted decreased fibroblast migration, cell border accumulation of polymerized actin, and down-regulation of the phospho-Akt expression. Our results indicated that MuRF2 was necessary to maintain the actin cytoskeleton functionality in skeletal muscle fibroblasts via Akt activity and exerted an important role in extracellular matrix remodeling in the skeletal muscle tissue.

Isolated branched-chain amino acid intake and muscle protein synthesis in humans: a biochemical review / Consumo isolado de aminoácidos de cadeia ramificada e síntese de proteína muscular em humanos: uma revisão bioquímica

ABSTRACT Alongside a proper diet, ergogenic aids with potential direct and/or indirect physical performance enhancing effects are sought after for improved adaptation to physical training. Nutritional ergogenics include diet composition changes and/or dietary supplementation. Branched-chain amino acids valine, leucine and isoleucine are widely popular among products with ergogenic claims. Their major marketing appeal derives from allegations that branched-chain amino acids intake combined with resistance physical exercise stimulates muscle protein synthesis. Evidence supporting the efficacy of branched-chain amino acids alone for muscle hypertrophy in humans is somewhat equivocal. This brief review describes physiological and biochemical mechanisms underpinning the effects of complete protein source and branched-chain amino acid intake on skeletal muscle growth in the postabsorptive and post-exercise state. Evidence in favor of or against potential anabolic effects of isolated branched-chain amino acid intake on muscle protein synthesis in humans is also examined.

RESUMO No treinamento físico, buscam-se, além de uma dieta adequada, recursos ergogênicos que possam maximizar direta e/ou indiretamente o desempenho físico. Entre as categorias de recursos ergogênicos, o nutricional compreende a modulação da composição dietética e/ou uso de suplementação. A comercialização dos suplementos de aminoácidos de cadeia ramificada valina, leucina e isoleucina possui muita popularidade entre aqueles com alegação ergogênica. O principal marketing está na afirmação de que o consumo isolado de aminoácidos de cadeia ramificada associado ao exercício físico resistido estimula a síntese de proteína muscular. As evidências da eficácia da ingestão isolada de aminoácidos de cadeia ramificada para a hipertrofia muscular em humanos parecem equivocadas. Nesta breve revisão, apresentamos a compreensão fisiológica e bioquímica de como a ingestão de uma fonte completa de proteína e de aminoácidos de cadeia ramificada afeta o crescimento do músculo esquelético no estado pós-absortivo e pós-exercício. Mostramos também as evidências que suportam ou não a afirmação dos potenciais efeitos anabólicos na síntese de proteína muscular dos aminoácidos de cadeia ramificada quando consumidos isoladamente em humanos.

A 1:1 exercise-to-rest period ratio needed by animals to restore energy sources and replenish anti-oxidative status after exercise

BACKGROUND/OBJECTIVES: Successful recovery of an animal from exercise is essential, especially prior to the next exercise session. This study was conducted to find an effective exercise-to-rest period ratio for the restoration of energy sources and replenishment of anti-oxidative status in tissue after exercise. MATERIALS/METHODS: Thirty-two rats were assigned to either non-training or training exercise groups for 5 weeks. After that period, the two groups were subdivided into four smaller groups: non-exercise (NE), exercise 0.5 hour and rest 1 hour (ER0.5:1), exercise 1 hour and rest 1 hour (ER1:1), exercise 2 hours and rest 1 hour (ER2:1). RESULTS: In the training group animals and compared to the NE group, the levels of plasma glucose after the rest period were significantly high in all ER groups but highest in the ER2:1 group. Similarly, the liver glycogen level was highest in the ER2:1 group. The plasma FFA level reached the highest level in the ER2:1 group but was similarly high in the ER0.5:1 group. Liver TG level was unchanged in the ER2:1 and ER1:1 groups but was significantly high in the ER0.5:1 group. Muscle TG levels were decreased in all three ER groups. Plasma protein levels were significantly high in the ER2:1 and ER0.5:1 groups. In both training animal and non-training animals, the liver protein levels did not change significantly between the NE and ER groups, irrespective of the exercise-to-rest ratio. In the training animal group, muscle protein level was significantly low in the ER2:1 and ER0.5:1 groups. The activity levels of superoxide dismutase and catalase, as well as the malondialdehyde concentration, were not significantly different between NE and ER groups, irrespective of the exercise-to-rest period ratio. CONCLUSIONS: These results indicate that animals provided with a 0.5:1 to 1:1 exercise-to-rest period ratio can restore their muscle energy sources and recover their anti-oxidative defense system.

Therapeutic effect of massage on denervated skeletal muscle atrophy in rats and its mechanism / 中国应用生理学杂志

OBJECTIVE@#To investigate the therapeutic effects of massage on denervated skeletal muscle atrophy in rats and its mechanism.@*METHODS@#Forty-eight male SD rats were randomly divided into model group (n=24) and massage group (n=24). Gastrocnemius muscle atrophy model was established by transecting the right tibial nerve of rat. On the second day after operation, the gastrocnemius muscle of the rats in the massage group was given manual intervention and the model group was not intervened. Six rats were sacrificed at the four time points of 0 d, 7 d, 14 d and 21 d. The gastrocnemius of the rats were obtained and measured the wet mass ratio after weighing. Cross-sectional area and diameter of the muscle fiber were measured after HE staining. The relative expressions of miR-23a, Akt, MuRF1 and MAFbx mRNA were tested with qPCR.@*RESULTS@#Compared with 0 d, the wet weight ratio, cross-sectional area and diameter of gastrocnemius muscle showed a progressive decline in the model group and massage group. The wet weight ratio, cross-sectional area and diameter of gastrocnemius muscle in the massage group were higher than those in the model group on 7 d, 14 d and 21 d (P＜0.05, P＜0.01). Compared with 0 d, the expressions of MuRF1, MAFbx and Akt mRNA were increased first and then were decreased in the model group and massage group. The expression of MuRF1 mRNA in massage group was lower than that in model group on 7 d and 21 d (P＜0.05, P＜0.01). The expression of MAFbx mRNA in massage group was lower than that in model group on 7 d, 14 d and 21 d (P＜0.01, P＜0.05, P＜0.01). The expression of Akt mRNA in massage group was higher than that in model group on 7 d, 14 d and 21 d (P＜0.05, P＜0.01). Compared with 0 d, the expression of miR-23a mRNA was increased in the model group and massage group on 21 d, and the expression of miR-23a mRNA in massage group was higher than that in model group (P＜ 0.05).@*CONCLUSION@#Massage can delay the atrophy of denervated skeletal muscle. The mechanism may be related to up-regulation of the expression of miR-23a and Akt mRNA, down-regulation of the expressions of MuRF1 and MAFbx mRNA, inhibition of protein degradation rate, and reduction of skeletal muscle protein degradation.

Expressions of GPR81, MCT1 and MCT4 in squamous carcinoma and their clinical significance / 中南大学学报(医学版)

To validate the expressions of G protein-coupled receptor 81 (GPR81), monocarboxylate transporter (MCT) 1 and MCT4 in cervical squamous carcinoma and to explore their role in the onset of cervical squamous carcinoma.
 Methods: Immunohistochemical method was used to detect the expressions of GPR81, MCT1 and MCT4 in 16 normal cervical tissue and 44 cervical squamous carcinoma tissue. The associations of these proteins expression with cervical squamous carcinoma or clinicopathological factors were analyzed.
 Results: The expressions of GPR81, MCT1 and MCT4 in cervical squamous carcinoma tissue were higher than those in normal cervical tissue (P0.05). No difference of the expressions of GPR81, MCT1 and MCT4 were found between cases with or without lymphatic metastasis (P>0.05). No correlation was found among GPR81, MCT1 and MCT4 in cervical squamous carcinoma (P>0.05).
 Conclusion: GPR81, MCT1 and MCT4 may be associated with the onset of cervical squamous carcinoma, and GPR81 may be associated with the progression of cervical squamous carcinoma.

Hypertonia-linked protein Trak1 functions with mitofusins to promote mitochondrial tethering and fusion

Hypertonia is a neurological dysfunction associated with a number of central nervous system disorders, including cerebral palsy, Parkinson's disease, dystonia, and epilepsy. Genetic studies have identified a homozygous truncation mutation in Trak1 that causes hypertonia in mice. Moreover, elevated Trak1 protein expression is associated with several types of cancers and variants in Trak1 are linked to childhood absence epilepsy in humans. Despite the importance of Trak1 in health and disease, the mechanisms of Trak1 action remain unclear and the pathogenic effects of Trak1 mutation are unknown. Here we report that Trak1 has a crucial function in regulation of mitochondrial fusion. Depletion of Trak1 inhibits mitochondrial fusion, resulting in mitochondrial fragmentation, whereas overexpression of Trak1 elongates and enlarges mitochondria. Our analyses revealed that Trak1 interacts and colocalizes with mitofusins on the outer mitochondrial membrane and functions with mitofusins to promote mitochondrial tethering and fusion. Furthermore, Trak1 is required for stress-induced mitochondrial hyperfusion and pro-survival response. We found that hypertonia-associated mutation impairs Trak1 mitochondrial localization and its ability to facilitate mitochondrial tethering and fusion. Our findings uncover a novel function of Trak1 as a regulator of mitochondrial fusion and provide evidence linking dysregulated mitochondrial dynamics to hypertonia pathogenesis.

Measurement of kinetic parameters of skeletal muscle protein synthesis in rats by deuterated water / 生理学报

The aim of the present study was to measure the kinetic parameters of skeletal muscle protein synthesis in rats by deuterated water (HO). Twenty Sprague-Dawley (SD) rats were labeled byHO through intraperitoneal injection and drinking. At the each end of the 1st, 3rd, 5th, 6th and 10th week after the firstHO labeling, four rats were sacrificed by cardiac puncture for blood plasma and quadriceps femoris sampling. Skeletal muscle protein and free amino acids in plasma were purified, hydrolyzed by hydrochloric acid and derived. The deuterium enrichments ofH-labeled alanyl in skeletal muscle protein and plasma protein-boundH-labeled alanine were determined by gas chromatography-mass spectrometry (GC-MS). The fractional synthesis rate of skeletal muscle protein and synthetic dynamic equation were calculated. The fractional synthetic rate of skeletal muscle protein was 12.8%/week, and synthetic dynamic equation was f= 0.158 × (1 - e). The results suggest that the kinetic parameters of skeletal muscle protein synthesis can be measured byHO labeling, and the method can be applied in long-term labeling experiment.

Myostatin promotes distinct responses on protein metabolism of skeletal and cardiac muscle fibers of rodents

Myostatin is a novel negative regulator of skeletal muscle mass. Myostatin expression is also found in heart in a much less extent, but it can be upregulated in pathological conditions, such as heart failure. Myostatin may be involved in inhibiting protein synthesis and/or increasing protein degradation in skeletal and cardiac muscles. Herein, we used cell cultures and isolated muscles from rats to determine protein degradation and synthesis. Muscles incubated with myostatin exhibited an increase in proteolysis with an increase of Atrogin-1, MuRF1 and LC3 genes. Extensor digitorum longus muscles and C2C12 myotubes exhibited a reduction in protein turnover. Cardiomyocytes showed an increase in proteolysis by activating autophagy and the ubiquitin proteasome system, and a decrease in protein synthesis by decreasing P70S6K. The effect of myostatin on protein metabolism is related to fiber type composition, which may be associated to the extent of atrophy mediated effect of myostatin on muscle.

Docosahexaenoic acid-mediated protein aggregates may reduce proteasome activity and delay myotube degradation during muscle atrophy in vitro

Proteasomes are the primary degradation machinery for oxidatively damaged proteins that compose a class of misfolded protein substrates. Cellular levels of reactive oxygen species increase with age and this cellular propensity is particularly harmful when combined with the age-associated development of various human disorders including cancer, neurodegenerative disease and muscle atrophy. Proteasome activity is reportedly downregulated in these disease conditions. Herein, we report that docosahexaenoic acid (DHA), a major dietary omega-3 polyunsaturated fatty acid, mediates intermolecular protein cross-linkages through oxidation, and the resulting protein aggregates potently reduce proteasomal activity both in vitro and in cultured cells. Cellular models overexpressing aggregation-prone proteins such as tau showed significantly elevated levels of tau aggregates and total ubiquitin conjugates in the presence of DHA, thereby reflecting suppressed proteasome activity. Strong synergetic cytotoxicity was observed when the cells overexpressing tau were simultaneously treated with DHA. Antioxidant N-acetyl cysteine significantly desensitized the cells to DHA-induced oxidative stress. DHA significantly delayed the proteasomal degradation of muscle proteins in a cellular atrophy model. Thus, the results of our study identified DHA as a potent inducer of cellular protein aggregates that inhibit proteasome activity and potentially delay systemic muscle protein degradation in certain pathologic conditions.

Association between Sarcopenic Obesity and Metabolic Syndrome in Postmenopausal Women: A Cross-sectional Study Based on the Korean National Health and Nutritional Examination Surveys from 2008 to 2011

BACKGROUND: Menopause contributes to an increase in visceral fat mass and a decrease in muscle protein synthesis. Therefore, we performed this study to examine their relationship how effect the changes of body composition as obesity and sarcopenia on metabolic syndrome (MS) as a predictor of cardiovascular disease in postmenopausal women. METHODS: Using data from the Korean National Health and Nutrition Examination Survey (KNHANES) from 2008 to 2011, we estimated that 4,183 postmenopausal women underwent dual energy X-ray absorptiometry scans. Sarcopenia was defined as an appendicular skeletal muscle mass divided by body weight that was less than 1 standard deviation below the sex specific mean for the young reference group. After classification into four groups, the results were adjusted with menopausal age and hormonal treatment. The relationship between sarcopenic obesity (SO) and MS in postmenopausal women was analyzed by logistic regression analysis in a complex sampling. RESULTS: In an unadjusted model, the odds ratio (OR) of MS for sarcopenia was 1.94 (95% confidence interval [CI], 1.52-2.49); the obesity group had an OR of 4.55 (95% CI, 3.63-5.71); and distinctly, the SO group had an OR of 6.26 (95% CI, 5.10-7.70). Even though there was controlling for variable adjustment, no definite difference was seen in the results. CONCLUSIONS: Sarcopenia and obesity were associated with MS independent of other metabolic impairment risk factors in both early menopausal and postmenopausal women. The results showed that, in particular, the prevalence of MS has increased more in postmenopausal women compared with previous research.

Protein metabolism and physical training: any need for amino acid supplementation?

Muscle mass is the major deposit of protein molecules with dynamic turnover between net protein synthesis and degradation. In human subjects, invasive and non-invasive techniques have been applied to determine their skeletal muscle catabolism of amino acids at rest, during and after different forms of physical exercise and training. The aim of this review is to analyse the turnover flux and the relative oxidation rate of different types of muscle proteins after one bout of exercise as well as after resistance and endurance condition of training. Protein feeding in athletes appears to be a crucial nutrition necessity to promote the maintenance of muscle mass and its adaptation to the need imposed by the imposed technical requirements. In resting human individuals, there commended protein daily allowance is about 0.8 g (dry weight) kg−body weight per 24 h knowing that humans are unable to accumulate protein stores in muscle tissues. Nevertheless, practical feeding recommendations related to regular exercise practice are proposed to athletes by different bodies in order to foster their skills and performance. This review will examine the results obtained under endurance and resistance type of exercise while consuming single or repeated doses of various ingestions of protein products (full meat, essential amino acids, specific amino acids and derivatives, vegetarian food). From the scientific literature, it appears that healthy athletes(and heavy workers) should have a common diet of 1.25 g kg−24 h to compensate the exercise training muscle protein degradation and their resyn thesis within the following hours. A nitrogen-balance assay would berecommended to avoid any excessive intake of protein. Eventually, a daily equilibrated food intake would beof primer importance versus inadequate absorption of some specific by-products.