Publications by authors named "Naoya Nakai"

44 Publications

Daily Oral Administration of Protease-Treated Royal Jelly Protects Against Denervation-Induced Skeletal Muscle Atrophy.

Nutrients 2020 Oct 11;12(10). Epub 2020 Oct 11.

Division of Molecular Signaling and Biochemistry, Department of Health Improvement, Kyushu Dental University, Kitakyushu, Fukuoka 803-8580, Japan.

Honeybees produce royal jelly (RJ) from their cephalic glands. Royal jelly is a source of nutrition for the queen honey bee throughout its lifespan and is also involved in fertility and longevity. Royal jelly has long been considered beneficial to human health. We recently observed that RJ delayed impairment of motor function during aging, affecting muscle fiber size. However, how RJ affects skeletal muscle metabolism and the functional component of RJ is as of yet unidentified. We demonstrate that feeding mice with RJ daily prevents a decrease in myofiber size following denervation without affecting total muscle weight. RJ did not affect atrophy-related genes but stimulated the expression of myogenesis-related genes, including and . Trans-10-hydroxy-2-decenoic acid (10H2DA) and 10-hydroxydecanoic acid (10HDAA), two major fatty acids contained in RJ. After ingestion, 10H2DA and 10HDAA are metabolized into 2-decenedioic acid (2DA) and sebacic acid (SA) respectively. We found that 10H2DA, 10HDAA, 2DA, and SA all regulated myogenesis of C2C12 cells, murine myoblast cells. These novel findings may be useful for potential preventative and therapeutic applications for muscle atrophy disease included in Sarcopenia, an age-related decline in skeletal muscle mass and strength.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/nu12103089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7600733PMC
October 2020

Autophagy under glucose starvation enhances protein translation initiation in response to re-addition of glucose in C2C12 myotubes.

FEBS Open Bio 2020 10 20;10(10):2149-2156. Epub 2020 Sep 20.

Laboratory of Exercise Nutrition, Department of Nutrition, University of Shiga Prefecture, Hikone, Japan.

Proteolysis is known to play a crucial role in maintaining skeletal muscle mass and function. Autophagy is a conserved intracellular process for the bulk degradation of proteins in lysosomes. Although nutrient starvation is known to induce autophagy, the effect of nutrient repletion following starvation on the mTOR pathway-mediated protein translation remains unclear. In the present study, we examined the effect of glucose starvation on the initiation of protein translation in response to glucose re-addition in C2C12 myotubes. Glucose starvation decreased the phosphorylation of p70 S6 kinase (p70S6K), a bonafide marker for protein translation initiation. Following re-addition of glucose, phosphorylation of p70S6K markedly increased only in glucose-starved cells. Inhibiting autophagy using pharmacological inhibitors diminished the effect of glucose re-addition on the phosphorylation of p70S6K, whereas inhibition of the ubiquitin-proteasome system did not exert any effect. In conclusion, autophagy under glucose starvation partially accounts for the activation of translation initiation by re-addition of glucose.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/2211-5463.12970DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7530399PMC
October 2020

Iron deficiency attenuates protein synthesis stimulated by branched-chain amino acids and insulin in myotubes.

Biochem Biophys Res Commun 2020 10 8;531(2):112-117. Epub 2020 Aug 8.

Laboratory of Exercise Nutrition, Department of Nutrition and Food Sciences, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga, 522-8533, Japan.

Iron deficiency anemia indicates poor nutrition and is a public health problem. Iron deficiency is also associated with muscle weakness. However, the intracellular mechanisms by which iron deficiency induces muscle weakness are obscure. The purpose of the present study was to evaluate the effect of iron deficiency on protein synthesis in basal and branched-amino acids (BCAA)- and insulin-stimulated state in muscle cells. Differentiated C2C12 myotubes were incubated with an iron chelator, deferoxamine mesylate, and then stimulated with BCAA or insulin to activate protein synthesis. This iron deprivation resulted in a significant reduction in the abundance of iron-containing proteins, such as the mitochondrial complex 1 subunit protein, compared to control cells, but not of protein that does not contain iron, such as citrate synthase. Proteins involved in glucose utilization, such as glucose transpoter-1, hexokinase and AMP-activated protein kinase (AMPK), were upregulated under iron deficiency. Additionally, rates of BCAA- and insulin-stimulated protein synthesis, measured by puromycin incorporation, were lower in iron-deficient myotubes than in control cells. We suggest that low iron availability attenuates BCAA- and insulin-stimulated protein synthesis, possibly via activation of AMPK in myotubes. The present findings advance the understanding of the importance of iron to skeletal muscle protein synthesis and, thus, may contribute to the prevention of sarcopenia and frailty.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbrc.2020.07.041DOI Listing
October 2020

Induction of Autophagy and Changes in Cellular Metabolism in Glucose Starved C2C12 Myotubes.

J Nutr Sci Vitaminol (Tokyo) 2020 ;66(1):41-47

Laboratory of Exercise Nutrition, Department of Nutrition, University of Shiga Prefecture.

Mouse myoblast C2C12 cells are commonly used as a model system for investigating the metabolic regulation of skeletal muscle. As it is therefore important to understand the metabolic features of C2C12 cells, we examined the effect of glucose starvation on autophagy in C2C12 myotubes. After culture of C2C12 myotubes with high (HG, 25.0 mM) or low (LG, 5.6 mM) glucose concentrations, the concentration of glucose in the LG group had decreased to 0 mM after 24 h of culture and was around 17 mM after 48 h of culture in the HG group. The concentration of lactate increased from 0 to approximately 9 mM at 24 h and then dropped slightly in the LG group, while it increased linearly to 21 mM in the HG group at 48 h. The phosphorylation of p70 S6 kinase, marker for the protein translation initiation was significantly lower and the ratio of LC3-II/LC3-I, marker for the induction of autophagy was significantly higher in the LG group. GLUT1 and hexokinase II expression were significantly higher in the LG group. Together, these changes in glucose and lactate concentrations in the culture media suggest that C2C12 myotubes depend on anaerobic glycolysis. Our findings also suggest that glucose depletion stimulates the expression of key molecules involved in glycolysis and that cellular autophagy is also activated in C2C12 myotubes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3177/jnsv.66.41DOI Listing
December 2020

Iron deficiency attenuates catecholamine‑stimulated lipolysis via downregulation of lipolysis‑related proteins and glucose utilization in 3T3‑L1 adipocytes.

Mol Med Rep 2020 Mar 13;21(3):1383-1389. Epub 2020 Jan 13.

Department of Nutrition, Laboratory of Exercise Nutrition, University of Shiga Prefecture, Hikone, Shiga 522‑8533, Japan.

Iron deficiency has been associated with obesity and related metabolic disorders. The aim of the present study was to evaluate the effect of iron deficiency on fat metabolism, particularly regarding the lipolytic activity, lipolysis‑related protein expression, and glucose utilization of adipocytes. Differentiated 3T3‑L1 adipocytes were incubated with an iron chelator, deferoxamine mesylate (DFO), for 48 h. Subsequently, basal and isoproterenol‑stimulated lipolytic activities, the proteins involved in lipolysis and glucose utilization were compared with a control (CON). The results revealed that treatment with DFO significantly decreased the free iron content but did not affect total protein and lipid contents in adipocytes. Iron deprivation caused a significant reduction in isoproterenol‑stimulated lipolysis, but not basal lipolysis. Lipolysis‑related proteins, including perilipin A, adipose triglyceride lipase, hormone sensitive lipase and comparative gene identification‑58, were decreased in the DFO compared with the CON group. Furthermore, glucose utilization, a major precursor of 3‑glycerol phosphate for micro‑lipid droplet synthesis during lipolysis and the expression of glucose transporter (GLUT) 4 were significantly lower in the DFO group when compared with the CON group. However, hypoxia‑inducible factor‑1α and GLUT1 expressions were upregulated in DFO‑treated adipocytes. In conclusion, the results indicated that low iron availability attenuated catecholamine‑stimulated lipolysis by downregulating lipolytic enzymes and glucose utilization in 3T3‑L1 adipocytes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3892/mmr.2020.10929DOI Listing
March 2020

Low-carbohydrate high-protein diet diminishes the insulin response to glucose load via suppression of SGLT-1 in mice.

Biosci Biotechnol Biochem 2019 Feb 25;83(2):365-371. Epub 2018 Oct 25.

a Laboratory of Exercise Nutrition, Department of Nutrition , The University of Shiga Prefecture , Hikone city , Japan.

The purpose of this study was to examine the effects of a low-carbohydrate high-protein (LCHP) diet on the expression of glucose transporters and their relationships to glucose metabolism. Male C57BL/6 mice were fed a normal control or LCHP diet for 2 weeks. An oral glucose tolerance test and insulin tolerance test (ITT) were performed, and the expression of glucose transporters was determined in the gastrocnemius muscle, jejunum and pancreas. The increase in plasma insulin concentrations after glucose administration was reduced in the LCHP group. However, LCHP diet had no effects on peripheral insulin sensitivity or glucose transporters expression in the gastrocnemius and pancreas. Soluble glucose transporter (SGLT)-1 protein content in jejunum was lower in the LCHP group. Taken together, these results suggest that the blunted insulin response after glucose administration in LCHP diet-fed mice might be due to decreased SGLT-1 expression, but not to an increase in peripheral insulin sensitivity. Abbreviations: LCHP: low-carbohydrate high-protein; ITT: insulin tolerance test; GLUT: glucose transporter; SGLT: soluble glucose transporter; OGTT: oral glucose tolerance test; AUC: area under the curve.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/09168451.2018.1533803DOI Listing
February 2019

Leucine supplementation after mechanical stimulation activates protein synthesis via L-type amino acid transporter 1 in vitro.

J Cell Biochem 2018 02 18;119(2):2094-2101. Epub 2017 Sep 18.

Department of Nutrition, University of Shiga Prefecture, Hikone, Shiga, Japan.

Branched-chain amino acid supplements consumed following exercise are widely used to increase muscle mass. Although both exercise (ie, mechanical stimulation) and branched-chain amino acid leucine supplementation have been reported to stimulate muscle protein synthesis by activating the mammalian target of rapamycin (mTOR) signaling pathway independently, the mechanisms underlying their synergistic effects are largely unknown. Utilizing cultured differentiated C2C12 myotubes, we established a combination treatment model in which the cells were subjected to cyclic uniaxial mechanical stretching (4 h, 15%, 1 Hz) followed by stimulation with 2 mM leucine for 45 min. Phosphorylation of p70 S6 kinase (p70S6K), an mTOR-regulated marker of protein translation initiation, was significantly increased following mechanical stretching alone but returned to the baseline after 4 h. Leucine supplementation further increased p70S6K phosphorylation, with a greater increase observed in the stretched cells than in the non-stretched cells. Notably, the expression of L-type amino acid transporter 1 (LAT1), a stimulator of the mTOR pathway, was also increased by mechanical stretching, and siRNA-mediated knockdown partially attenuated leucine-induced p70S6K phosphorylation. These results suggest that mechanical stretching promotes LAT1 expression and, consequently, amino acid uptake, leading to enhanced leucine-induced activation of protein synthesis. LAT1 has been demonstrated to be a point of crosstalk between exercise- and nutrition-induced skeletal muscle growth.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jcb.26371DOI Listing
February 2018

Vibration acceleration promotes bone formation in rodent models.

PLoS One 2017 6;12(3):e0172614. Epub 2017 Mar 6.

Department of Orthopedic Surgery, Osaka University Graduate School of Medicine, Osaka, Japan.

All living tissues and cells on Earth are subject to gravitational acceleration, but no reports have verified whether acceleration mode influences bone formation and healing. Therefore, this study was to compare the effects of two acceleration modes, vibration and constant (centrifugal) accelerations, on bone formation and healing in the trunk using BMP 2-induced ectopic bone formation (EBF) mouse model and a rib fracture healing (RFH) rat model. Additionally, we tried to verify the difference in mechanism of effect on bone formation by accelerations between these two models. Three groups (low- and high-magnitude vibration and control-VA groups) were evaluated in the vibration acceleration study, and two groups (centrifuge acceleration and control-CA groups) were used in the constant acceleration study. In each model, the intervention was applied for ten minutes per day from three days after surgery for eleven days (EBF model) or nine days (RFH model). All animals were sacrificed the day after the intervention ended. In the EBF model, ectopic bone was evaluated by macroscopic and histological observations, wet weight, radiography and microfocus computed tomography (micro-CT). In the RFH model, whole fracture-repaired ribs were excised with removal of soft tissue, and evaluated radiologically and histologically. Ectopic bones in the low-magnitude group (EBF model) had significantly greater wet weight and were significantly larger (macroscopically and radiographically) than those in the other two groups, whereas the size and wet weight of ectopic bones in the centrifuge acceleration group showed no significant difference compared those in control-CA group. All ectopic bones showed calcified trabeculae and maturated bone marrow. Micro-CT showed that bone volume (BV) in the low-magnitude group of EBF model was significantly higher than those in the other two groups (3.1±1.2mm3 v.s. 1.8±1.2mm3 in high-magnitude group and 1.3±0.9mm3 in control-VA group), but BV in the centrifuge acceleration group had no significant difference compared those in control-CA group. Union rate and BV in the low-magnitude group of RFH model were also significantly higher than those in the other groups (Union rate: 60% v.s. 0% in the high-magnitude group and 10% in the control-VA group, BV: 0.69±0.30mm3 v.s. 0.15±0.09mm3 in high-magnitude group and 0.22±0.17mm3 in control-VA group). BV/TV in the low-magnitude group of RFH model was significantly higher than that in control-VA group (59.4±14.9% v.s. 35.8±13.5%). On the other hand, radiographic union rate (10% in centrifuge acceleration group v.s. 20% in control-CA group) and micro-CT parameters in RFH model were not significantly different between two groups in the constant acceleration studies. Radiographic images of non-union rib fractures showed cartilage at the fracture site and poor new bone formation, whereas union samples showed only new bone. In conclusion, low-magnitude vibration acceleration promoted bone formation at the trunk in both BMP-induced ectopic bone formation and rib fracture healing models. However, the micro-CT parameters were not similar between two models, which suggested that there might be difference in the mechanism of effect by vibration between two models.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0172614PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5338772PMC
August 2017

Muscle-specific deletion of BDK amplifies loss of myofibrillar protein during protein undernutrition.

Sci Rep 2017 01 4;7:39825. Epub 2017 Jan 4.

Laboratory of Nutritional Biochemistry, Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.

Branched-chain amino acids (BCAAs) are essential amino acids for mammals and play key roles in the regulation of protein metabolism. However, the effect of BCAA deficiency on protein metabolism in skeletal muscle in vivo remains unclear. Here we generated mice with lower BCAA concentrations by specifically accelerating BCAA catabolism in skeletal muscle and heart (BDK-mKO mice). The mice appeared to be healthy without any obvious defects when fed a protein-rich diet; however, bolus ingestion of BCAAs showed that mTORC1 sensitivity in skeletal muscle was enhanced in BDK-mKO mice compared to the corresponding control mice. When these mice were fed a low protein diet, the concentration of myofibrillar protein was significantly decreased (but not soluble protein) and mTORC1 activity was reduced without significant change in autophagy. BCAA supplementation in drinking water attenuated the decreases in myofibrillar protein levels and mTORC1 activity. These results suggest that BCAAs are essential for maintaining myofibrillar proteins during protein undernutrition by keeping mTORC1 activity rather than by inhibiting autophagy and translation. This is the first report to reveal the importance of BCAAs for protein metabolism of skeletal muscle in vivo.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/srep39825DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5209746PMC
January 2017

Prenatal myonuclei play a crucial role in skeletal muscle hypertrophy in rodents.

Am J Physiol Cell Physiol 2017 Mar 7;312(3):C233-C243. Epub 2016 Dec 7.

School of Human Cultures, University of Shiga Prefecture, Hikone, Japan.

Multinucleated muscle fibers are formed by the fusion of myogenic progenitor cells during embryonic and fetal myogenesis. However, the role of prenatally incorporated myonuclei in the skeletal muscle fibers of adult animals is poorly understood. We demonstrated, using muscle-specific reporter mice, that the prenatal myonuclei remained in the adult soleus muscle, although cardiotoxin injection caused the loss of prenatal myonuclei. Overloading by the tendon transection of synergists failed to induce compensatory hypertrophy in regenerated soleus muscle fibers of adult rats, whereas unloading by tail suspension normally induced the fiber atrophy. Loss of hypertrophying function correlated with the lowered histone acetylation at the transcription start site of gene, which was one of the genes that did not respond to the overloading. These parameters were improved by the transplantation of cells harvested from the juvenile soleus muscles of neonatal rats in association with enhanced histone acetylation of gene. These results indicated that the presence of prenatal myonuclei was closely related to the status of histone acetylation, which could regulate the responsiveness of muscle fibers to physiological stimuli.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpcell.00151.2016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5401943PMC
March 2017

Differences in histone modifications between slow- and fast-twitch muscle of adult rats and following overload, denervation, or valproic acid administration.

J Appl Physiol (1985) 2015 Nov 24;119(10):1042-52. Epub 2015 Sep 24.

Graduate School of Sports Sciences, Doshisha University, Kyotanabe City, Kyoto, Japan.

Numerous studies have reported alterations in skeletal muscle properties and phenotypes in response to various stimuli such as exercise, unloading, and gene mutation. However, a shift in muscle fiber phenotype from fast twitch to slow twitch is not completely induced by stimuli. This limitation is hypothesized to result from the epigenetic differences between muscle types. The main purpose of the present study was to identify the differences in histone modification for the plantaris (fast) and soleus (slow) muscles of adult rats. Genome-wide analysis by chromatin immunoprecipitation followed by DNA sequencing revealed that trimethylation at lysine 4 and acetylation of histone 3, which occurs at transcriptionally active gene loci, was less prevalent in the genes specific to the slow-twitch soleus muscle. Conversely, gene loci specific to the fast-twitch plantaris muscle were associated with the aforementioned histone modifications. We also found that upregulation of slow genes in the plantaris muscle, which are related to enhanced muscular activity, is not associated with activating histone modifications. Furthermore, silencing of muscle activity by denervation caused the displacement of acetylated histone and RNA polymerase II (Pol II) in 5' ends of genes in plantaris, but minor effects were observed in soleus. Increased recruitment of Pol II induced by forced acetylation of histone was also suppressed in valproic acid-treated soleus. Our present data indicate that the slow-twitch soleus muscle has a unique set of histone modifications, which may relate to the preservation of the genetic backbone against physiological stimuli.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/japplphysiol.00289.2015DOI Listing
November 2015

Mechanical stretch activates mammalian target of rapamycin and AMP-activated protein kinase pathways in skeletal muscle cells.

Mol Cell Biochem 2015 Aug 14;406(1-2):285-92. Epub 2015 May 14.

Department of Health and Sports Sciences, Graduate School of Medicine, Osaka University, 1-17 Machikaneyama-cho, Toyonaka, Osaka, 560-0043, Japan,

Cellular protein synthesis is believed to be antagonistically regulated by mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) signaling pathways. In the present study, we examined the relationship between mTOR/p70 S6 kinase (p70S6K) and AMPK in response to mechanical stretch. C2C12 myoblasts were grown on a silicone elastomer chamber to confluence and further cultured in differentiation medium for 4 days to form multinucleated myotubes. Cells were subjected to 15% cyclic uniaxial stretch for 4 h at a frequency of 1 Hz. Phosphorylation of p70S6K at threonine 389 and AMPK at threonine 172 of the catalytic α subunit were concomitantly increased by mechanical stretch. Stimulation of the mTOR pathway by adding leucine and insulin increased the phosphorylation of p70S6K without inactivation of AMPK. In contrast, addition of compound C, a pharmacological inhibitor of AMPK, increased the phosphorylation of p70S6K in stretched cells. Activation of AMPK by the addition of 5-amino-4-imidazolecarboxamide ribonucleoside reduced the phosphorylation of p70S6K in response to mechanical stretch. In conclusion, crosstalk between mTOR and AMPK signaling was not tightly regulated in response to physiological stimuli, such as mechanical stress and/or nutrients. However, pharmacological modulation of AMPK influenced the mTOR/p70S6K signaling pathway.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11010-015-2446-7DOI Listing
August 2015

Retardation of C2C12 myoblast cell proliferation by exposure to low-temperature atmospheric plasma.

J Physiol Sci 2014 Sep 18;64(5):365-75. Epub 2014 Jul 18.

Department of Health and Sports Sciences, Graduate School of Medicine, Osaka University, 1-17 Machikaneyama-cho, Toyonaka, Osaka, 560-0043, Japan,

As the first step in evaluating the possibility of low-temperature atmospheric plasma for clinical applications in the treatment of rhabdomyosarcoma (RMS), we determined the effects of plasma exposure on C2C12 myoblasts. The low-temperature atmospheric plasma was generated through an electrical discharge in argon gas. One minute of plasma exposure every 24 h inhibited the cell proliferation, whereas myoblast differentiation was not affected. Plasma exposure increased the phosphorylation of ERK and JNK at 30 min after the exposure, but the phosphorylation of both was decreased to less than control levels at 1 and 4 h after the exposure. Plasma exposure increased the percentage of cells in the G2/M phase at 8 h after the exposure. In conclusion, plasma exposure retarded the proliferation of C2C12 myoblasts by G2/M arrest. Therefore, plasma exposure can be a possible treatment for the anti-proliferative effects of malignant tumors, such as RMS, without affecting differentiated skeletal muscle cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s12576-014-0328-5DOI Listing
September 2014

Anti-interleukin-6 receptor antibody (MR16-1) promotes muscle regeneration via modulation of gene expressions in infiltrated macrophages.

Biochim Biophys Acta 2014 Oct 15;1840(10):3170-80. Epub 2014 Jan 15.

Graduate School of Medicine, Osaka University, Japan; Graduate School of Frontier Bioscience, Osaka University, Japan. Electronic address:

Background: Although rat anti-mouse IL-6 receptor (IL-6R) antibody (MR16-1) has been reported to effectively ameliorate various tissue damages, its effect on skeletal muscle regeneration has not been determined. Moreover, the localization, persistence and duration of action of this reagent in damaged tissues after systemic administration have not been assessed.

Methods: The MR16-1 was administered i.p. immediately after cardiotoxin (CTX)-induced muscle damage on mice.

Results: MR16-1 administered i.p. was observed only to the damaged muscle. This delivered MR16-1 was dramatically decreased from 3 to 7days post-injury concomitantly with a reduction of IL-6R expression. This reduction of the MR16-1 level in the damaged muscle was not rescued by additional administration of MR16-1, suggesting the short half-life of MR16-1 was not the factor for the remaining levels. In addition, a significant inhibitory effect of MR16-1 on phosphorylation of the signal transducer and activator of transcription 3 was observed in the macrophage-enriched area of damaged muscle 3days after injury. Finally, the acceleration of muscle regeneration observed at day 7 post-injury following MR16-1 treatment was associated with reduced expression of fibrosis-related genes, such as interleukin-10 and arginase, in the infiltrated macrophages.

Conclusions: These results suggest that MR16-1 which was found primarily localized in infiltrated macrophages in the damaged muscle might facilitate muscle regeneration via immune modulation.

General Significance: These findings are deemed to provide further insight into the understanding not only of MR16-1 treatment on muscle regeneration, but also of the other anti-cytokine treatment on the cytokine-related disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbagen.2014.01.014DOI Listing
October 2014

Evaluation of gene, protein and neurotrophin expression in the brain of mice exposed to space environment for 91 days.

PLoS One 2012 9;7(7):e40112. Epub 2012 Jul 9.

Behavioural Neuroscience Section, Cellular Biology and Neuroscience Department, Istituto Superiore di Sanità, Rome, Italy.

Effects of 3-month exposure to microgravity environment on the expression of genes and proteins in mouse brain were studied. Moreover, responses of neurobiological parameters, nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF), were also evaluated in the cerebellum, hippocampus, cortex, and adrenal glands. Spaceflight-related changes in gene and protein expression were observed. Biological processes of the up-regulated genes were related to the immune response, metabolic process, and/or inflammatory response. Changes of cellular components involving in microsome and vesicular fraction were also noted. Molecular function categories were related to various enzyme activities. The biological processes in the down-regulated genes were related to various metabolic and catabolic processes. Cellular components were related to cytoplasm and mitochondrion. The down-regulated molecular functions were related to catalytic and oxidoreductase activities. Up-regulation of 28 proteins was seen following spaceflight vs. those in ground control. These proteins were related to mitochondrial metabolism, synthesis and hydrolysis of ATP, calcium/calmodulin metabolism, nervous system, and transport of proteins and/or amino acids. Down-regulated proteins were related to mitochondrial metabolism. Expression of NGF in hippocampus, cortex, and adrenal gland of wild type animal tended to decrease following spaceflight. As for pleiotrophin transgenic mice, spaceflight-related reduction of NGF occurred only in adrenal gland. Consistent trends between various portions of brain and adrenal gland were not observed in the responses of BDNF to spaceflight. Although exposure to real microgravity influenced the expression of a number of genes and proteins in the brain that have been shown to be involved in a wide spectrum of biological function, it is still unclear how the functional properties of brain were influenced by 3-month exposure to microgravity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0040112PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3392276PMC
March 2013

The impact of long-term exposure to space environment on adult mammalian organisms: a study on mouse thyroid and testis.

PLoS One 2012 25;7(4):e35418. Epub 2012 Apr 25.

DIPTERIS, University of Genoa, Genova, Italy.

Hormonal changes in humans during spaceflight have been demonstrated but the underlying mechanisms are still unknown. To clarify this point thyroid and testis/epididymis, both regulated by anterior pituitary gland, have been analyzed on long-term space-exposed male C57BL/10 mice, either wild type or pleiotrophin transgenic, overexpressing osteoblast stimulating factor-1. Glands were submitted to morphological and functional analysis.In thyroids, volumetric ratios between thyrocytes and colloid were measured. cAMP production in 10(-7)M and 10(-8)M thyrotropin-treated samples was studied. Thyrotropin receptor and caveolin-1 were quantitized by immunoblotting and localized by immunofluorescence. In space-exposed animals, both basal and thyrotropin-stimulated cAMP production were always higher. Also, the structure of thyroid follicles appeared more organized, while thyrotropin receptor and caveolin-1 were overexpressed. Unlike the control samples, in the space samples thyrotropin receptor and caveolin-1 were both observed at the intracellular junctions, suggesting their interaction in specific cell membrane microdomains.In testes, immunofluorescent reaction for 3β- steroid dehydrogenase was performed and the relative expressions of hormone receptors and interleukin-1β were quantified by RT-PCR. Epididymal sperm number was counted. In space-exposed animals, the presence of 3β and 17β steroid dehydrogenase was reduced. Also, the expression of androgen and follicle stimulating hormone receptors increased while lutenizing hormone receptor levels were not affected. The interleukin 1 β expression was upregulated. The tubular architecture was altered and the sperm cell number was significantly reduced in spaceflight mouse epididymis (approx. -90% vs. laboratory and ground controls), indicating that the space environment may lead to degenerative changes in seminiferous tubules.Space-induced changes of structure and function of thyroid and testis/epididymis could be responsible for variations of hormone levels in human during space missions. More research, hopefully a reflight of MDS, would be needed to establish whether the space environment acts directly on the peripheral glands or induces changes in the hypotalamus-pituitary-glandular axis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0035418PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3338839PMC
September 2012

Effects of mechanical over-loading on the properties of soleus muscle fibers, with or without damage, in wild type and mdx mice.

PLoS One 2012 16;7(4):e34557. Epub 2012 Apr 16.

Graduate School of Frontier Biosciences, Osaka University, Toyonaka City, Osaka, Japan.

Effects of mechanical over-loading on the characteristics of regenerating or normal soleus muscle fibers were studied in dystrophin-deficient (mdx) and wild type (WT) mice. Damage was also induced in WT mice by injection of cardiotoxin (CTX) into soleus muscle. Over-loading was applied for 14 days to the left soleus muscle in mdx and intact and CTX-injected WT mouse muscles by ablation of the distal tendons of plantaris and gastrocnemius muscles. All of the myonuclei in normal muscle of WT mice were distributed at the peripheral region. But, central myonuclei were noted in all fibers of WT mice regenerating from CTX-injection-related injury. Further, many fibers of mdx mice possessed central myonuclei and the distribution of such fibers was increased in response to over-loading, suggesting a shift of myonuclei from peripheral to central region. Approximately 1.4% branched fibers were seen in the intact muscle of mdx mice, although these fibers were not detected in WT mice. The percentage of these fibers in mdx, not in WT, mice was increased by over-loading (∼51.2%). The fiber CSA in normal WT mice was increased by over-loading (p<0.05), but not in mdx and CTX-injected WT mice. It was suggested that compensatory hypertrophy is induced in normal muscle fibers of WT mice following functional over-loading. But, it was also indicated that muscle fibers in mdx mice are susceptible to mechanical over-loading and fiber splitting and shift of myonuclei from peripheral to central region are induced.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0034557PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3327707PMC
August 2012

Adaptation of mouse skeletal muscle to long-term microgravity in the MDS mission.

PLoS One 2012 28;7(3):e33232. Epub 2012 Mar 28.

Department of Biomedical Sciences, University of Padova, Padova, Italy.

The effect of microgravity on skeletal muscles has so far been examined in rat and mice only after short-term (5-20 day) spaceflights. The mice drawer system (MDS) program, sponsored by Italian Space Agency, for the first time aimed to investigate the consequences of long-term (91 days) exposure to microgravity in mice within the International Space Station. Muscle atrophy was present indistinctly in all fiber types of the slow-twitch soleus muscle, but was only slightly greater than that observed after 20 days of spaceflight. Myosin heavy chain analysis indicated a concomitant slow-to-fast transition of soleus. In addition, spaceflight induced translocation of sarcolemmal nitric oxide synthase-1 (NOS1) into the cytosol in soleus but not in the fast-twitch extensor digitorum longus (EDL) muscle. Most of the sarcolemmal ion channel subunits were up-regulated, more in soleus than EDL, whereas Ca(2+)-activated K(+) channels were down-regulated, consistent with the phenotype transition. Gene expression of the atrophy-related ubiquitin-ligases was up-regulated in both spaceflown soleus and EDL muscles, whereas autophagy genes were in the control range. Muscle-specific IGF-1 and interleukin-6 were down-regulated in soleus but up-regulated in EDL. Also, various stress-related genes were up-regulated in spaceflown EDL, not in soleus. Altogether, these results suggest that EDL muscle may resist to microgravity-induced atrophy by activating compensatory and protective pathways. Our study shows the extended sensitivity of antigravity soleus muscle after prolonged exposition to microgravity, suggests possible mechanisms accounting for the resistance of EDL, and individuates some molecular targets for the development of countermeasures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0033232PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3314659PMC
August 2012

Effects of hindlimb unloading on neurogenesis in the hippocampus of newly weaned rats.

Neurosci Lett 2012 Feb 22;509(2):76-81. Epub 2011 Dec 22.

Graduate School of Medicine, Osaka University, Toyonaka City, Osaka 560-0043, Japan.

Effects of hindlimb suspension (HS) and ambulation recovery on hippocampal neurogenesis of newly weaned rats were studied by using immunohistochemical techniques. The number of proliferating cell nuclear antigen-positive (PCNA(+)) cells in the subgranular zone (SGZ) markedly decreased during normal growth. However, neither HS nor subsequent recovery caused additional changes in the number of PCNA(+) cells. The number of doublecortin-positive (DCX(+)) neurons decreased gradually during normal growth. HS resulted in a further decrease in these neurons. However, DCX(+) cell numbers became identical to the levels in age-matched controls after 14 days of recovery. PCNA and DCX-double positive cells in the SGZ were also observed, and their cell numbers were not affected by HS and 14-day ambulation. Thus, HS suppressed the generation of DCX(+) neurons without affecting PCNA(+) cells in the SGZ of weaned rats. Taken together, hippocampal neurogenesis in weaned rats was not severely affected by HS while it decreased significantly as they had grown.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neulet.2011.12.022DOI Listing
February 2012

HSP25 can modulate myofibrillar desmin cytoskeleton following the phosphorylation at Ser15 in rat soleus muscle.

J Appl Physiol (1985) 2012 Jan 13;112(1):176-86. Epub 2011 Oct 13.

Graduate School of Medicine, Osaka University, Toyonaka City, Osaka, Japan.

The main purpose of the present study was to investigate the role(s) of 25-kDa heat shock protein (HSP25) in the regulation and integration of myofibrillar Z-disc structure during down- or upregulation of the size in rat soleus muscle fibers. Hindlimb unloading by tail suspension was performed in adult rats for 7 days, and reloading was allowed for 5 days after the termination of suspension. Interaction of HSP25 and Z-disc proteins, phosphorylation status, distribution, and complex formation of HSP25 were investigated. Non- and single-phosphorylated HSP25s were generally expressed in the cytoplasmic fraction of normal muscle. The level of total HSP25, as well as the phosphorylation ratio, did not change significantly in response to atrophy. Increased expressions of HSP25, phosphorylated at serine 15 (p-Ser15) and dual-phosphorylated form, were noted, when atrophied muscles were reloaded. Myofibrillar HSP25 was also noted in reloaded muscle. Histochemical analysis further indicated the localization of p-Ser15 in the regions with disorganization of Z-disc structure in reloaded muscle fibers. HSP25 formed a large molecular complex in the cytoplasmic fraction of normal muscle, whereas dissociation of free HSP25 with Ser15 phosphorylation was noted in reloaded muscle. The interaction of p-Ser15 with desmin and actinin was detected in Z-discs by proximity ligation assay. Strong interaction between p-Ser15 and desmin, but not actinin, was noted in the disorganized areas. These results indicated that HSP25 contributed to the desmin cytoskeletal organization following the phosphorylation at Ser15 during reloading and regrowing of soleus muscle.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/japplphysiol.00783.2011DOI Listing
January 2012

Responses of HSC70 expression in diencephalon to iron deficiency anemia in rats.

J Physiol Sci 2011 Nov 3;61(6):445-56. Epub 2011 Aug 3.

Section of Applied Physiology, Graduate School of Medicine, Osaka University, Toyonaka, Osaka, 560-0043, Japan.

A powdered diet containing 100 or 3 ppm Fe was fed to rats starting at the age of 3 weeks. The voluntary activity level was checked using a wheel in the cage during the 17th week after the beginning of supplementation. Significantly less activity was seen in the 3 ppm Fe group during both light and dark periods. After 20 weeks, the blood and diencephalon were sampled from both groups. Lower hematocrit and blood hemoglobin content was observed in the 3 ppm Fe group. The level of 70 kDa heat shock cognate (HSC70) expression was greater in the diencephalon of the 3 ppm Fe group. In addition, the distribution of HSC70 was determined by proximity ligation assay. More HSC70-positive as well as total cells were noted in several areas of the diencephalon of the iron-deficient rats. The altered expression and distribution of HSC70 might play some role in the neurological changes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s12576-011-0164-9DOI Listing
November 2011

Region-specific responses of adductor longus muscle to gravitational load-dependent activity in Wistar Hannover rats.

PLoS One 2011 22;6(6):e21044. Epub 2011 Jun 22.

Graduate School of Frontier Biosciences, Osaka University, Toyonaka City, Osaka, Japan.

Response of adductor longus (AL) muscle to gravitational unloading and reloading was studied. Male Wistar Hannover rats (5-wk old) were hindlimb-unloaded for 16 days with or without 16-day ambulation recovery. The electromyogram (EMG) activity in AL decreased after acute unloading, but that in the rostral region was even elevated during continuous unloading. The EMG levels in the caudal region gradually increased up to 6th day, but decreased again. Approximately 97% of fibers in the caudal region were pure type I at the beginning of experiment. Mean percentage of type I fibers in the rostral region was 61% and that of type I+II and II fiber was 14 and 25%, respectively. The percent type I fibers decreased and de novo appearance of type I+II was noted after unloading. But the fiber phenotype in caudal, not rostral and middle, region was normalized after 16-day ambulation. Pronounced atrophy after unloading and re-growth following ambulation was noted in type I fibers of the caudal region. Sarcomere length in the caudal region was passively shortened during unloading, but that in the rostral region was unchanged or even stretched slightly. Growth-associated increase of myonuclear number seen in the caudal region of control rats was inhibited by unloading. Number of mitotic active satellite cells decreased after unloading only in the caudal region. It was indicated that the responses of fiber properties in AL to unloading and reloading were closely related to the region-specific neural and mechanical activities, being the caudal region more responsive.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0021044PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3120817PMC
November 2011

Effects of creatine and its analog, β-guanidinopropionic acid, on the differentiation of and nucleoli in myoblasts.

Biosci Biotechnol Biochem 2011 13;75(6):1085-9. Epub 2011 Jun 13.

Department of Health and Sports Sciences, Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan.

The effects of supplementation with creatine (Cr) and its analog, β-guanidinopropionic acid (β-GPA), on the differentiation of myoblasts and the numbers of nucleoli were studied in C2C12 cells. The cells were cultured in differentiation medium for 4 d. Then Cr (1 mM) or β-GPA (1 mM) was added to the cells, and the mixture was cultured for an additional 2 d. Although the number of myotubes was not different among the groups, myotube diameters and nuclear numbers in myotubes were increased by Cr and β-GPA treatment respectively. The expression of differentiation marker proteins, myogenin, and the myosine heavy chain, was increased in the β-GPA group. Supplementation with β-GPA also increased the percentage of p21 (inhibitor for cell cycle progression)-positive myoblasts. Supplementation with Cr inhibited the decrease in nucleoli numbers, whereas β-GPA increased nucleolar sizes in the myotubes. These results suggest that β-GPA supplementation stimulated the differentiation of myoblasts into multi-nucleated myotubes through induction of p21 expression.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1271/bbb.100901DOI Listing
October 2011

Mechanical stretch activates signaling events for protein translation initiation and elongation in C2C12 myoblasts.

Mol Cells 2010 Dec 14;30(6):513-8. Epub 2010 Oct 14.

Section of Applied Physiology, Department of Health and Sports Sciences, Graduate School of Medicine, Osaka University, Osaka 560-0043, Japan.

It has been proposed that mechanically induced tension is the critical factor in the induction of muscle hypertrophy. However, the molecular mechanisms involved in this process are still under investigation. In the present study, the effect of mechanical stretch on intracellular signaling for protein translation initiation and elongation was studied in C2C12 myoblasts. Cells were grown on a silicone elastomer chamber and subjected to 30-min of 5 or 15% constant static or cyclic (60 cycles/min) uniaxial stretch. Western blot analyses revealed that p70 S6 kinase (p70S6K) and eukaryotic elongation factor 2 (eEF2), which are the markers for translation initiation and peptide chain elongation, respectively, were activated by both static and cyclic stretch. The magnitude of activation was greater in response to the 15% cyclic stretch. Cyclic stretch also increased the phosphorylation of MAP kinases (p38 MAPK, ERK1/2 and JNK). However, the pharmacological inhibition of MAP kinases did not block the stretch-induced activation of p70S6K and eEF2. An inhibitor of the mammalian target of rapamycin (mTOR) blocked the stretch-induced phosphorylation of p70S6K but did not affect the eEF2 activation. A broad-range tyrosine kinase inhibitor, genistein, blocked the stretch-induced activation of p70S6K and eEF2, whereas Src tyrosine kinase and Janus kinase (JAK) inhibitors did not. These results suggest that the stretch-induced activation of protein translation initiation and elongation in mouse myoblast cell lines is mediated by tyrosine kinase(s), except for Src kinase or JAK.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10059-010-0147-3DOI Listing
December 2010

Role(s) of gravitational loading during developing period on the growth of rat soleus muscle fibers.

J Appl Physiol (1985) 2010 Mar 7;108(3):676-85. Epub 2010 Jan 7.

Graduate School of Medicine, Osaka University, Toyonaka City, Osaka 560-0043, Japan.

Effects of gravitational loading or unloading on the gain of the characteristics in soleus muscle fibers were studied in rats. The tail suspension was performed in newborn rats from postnatal day 4 to month 3, and the reloading was allowed for 3 mo in some rats. Single expression of type I myosin heavy chain (MHC) was observed in approximately 82% of fibers in 3-mo-old controls, but the fibers expressing multiple MHC isoforms were noted in the unloaded rats. Although 97% of fibers in 3-mo-old controls had a single neuromuscular junction at the central region of fiber, fibers with multiple nerve endplates were seen in the unloaded group. Faster contraction speed and lower maximal tension development, even after normalization with fiber size, were observed in the unloaded pure type I MHC fibers. These parameters generally returned to the age-matched control levels after reloading. It was suggested that antigravity-related tonic activity plays an important role in the gain of single neural innervation and of slow contractile properties and phenotype in soleus muscle fibers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/japplphysiol.00478.2009DOI Listing
March 2010

Myonucleus-related properties in soleus muscle fibers of mdx mice.

Cells Tissues Organs 2010 18;191(3):248-59. Epub 2009 Sep 18.

Osaka University, Japan.

Distribution and total number of myonuclei in single soleus muscle fibers, sampled from tendon to tendon, were analyzed in mdx and wild-type (WT) mice. Apoptotic myonuclei and the microscopic structure around the myonuclei were also analyzed. Three types of muscle fibers of mdx mice with myonuclear distribution at either central, peripheral, or both central and peripheral regions were observed in the longitudinal analyses. All of the myonuclei were located at the peripheral region in WT mice. The total number of myonuclei counted in the whole length of fibers with peripheral myonuclei only was 17% less in mdx than in WT mice (p < 0.05). But the total myonuclear numbers in mdx mouse fibers with different distribution (peripheral vs. central) of myonuclei were identical, and the peripheral nucleus was noted where the central nucleus was missing. Myonuclei located between the center and peripheral regions were also seen in the cross-sectional analyses of muscle fibers. The cross-sectional area and length of fibers, sarcomere number, myonuclear size, myosin heavy chain expression, satellite cell number and neuromuscular junction were identical between each type of fiber. Apoptosis was not detected in any myonuclei located either in central or peripheral regions of muscle fibers. Thus, it was suggested that apoptosis-related loss of central myonuclei and regeneration-related new accretion at the peripheral region is not the cause of different distribution of myonuclei seen in muscle fibers in mdx mice. However, it was speculated that cross-sectional migration of myonuclei from central to peripheral regions may be induced in response to regeneration, because the total myonuclear numbers in fibers with different distribution of myonuclei were identical, and the peripheral nucleus was noted where the central nucleus was missing. Further, myonuclei located between the center and peripheral regions were also seen. However, the question remains as to how or why nuclei might migrate to the periphery in a regenerating muscle fiber, since there was no microscopic evidence of any structural changes around the myonuclei that may be responsible for the movement of the nucleus.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1159/000240245DOI Listing
May 2010

Effects of peroxisome proliferator-activated receptor alpha (PPARalpha) agonists on leucine-induced phosphorylation of translational targets in C2C12 cells.

Biochim Biophys Acta 2008 Oct 18;1780(10):1101-5. Epub 2008 Jun 18.

Department of Health and Sports Sciences, Graduate School of Medicine Bioscience, Osaka University, Osaka 560-0043, Japan.

Effect of peroxisome proliferator-activated receptor alpha (PPARalpha) agonists, WY-14,643 (WY) and/or clofibrate, on the leucine-induced phosphorylation of translational targets in C2C12 myoblasts was studied. C2C12 cells were treated with WY or clofibrate for 24 h prior to stimulation with leucine. Western blot analyses revealed that the leucine-induced phosphorylation of p70 S6 kinase (p70S6K), a key regulator of translation initiation, was significantly higher in WY-treated cells than in control and clofibrate-treated cells. Phosphorylation of extracellular-regulated kinase (ERK1/2) was higher in WY-treated cells. WY treatment also increased the leucine-induced phosphorylation of ribosomal protein S6 and eukaryotic initiation factor 4B. In contrast, eukaryotic elongation factor 2, a marker for peptide chain elongation process, was significantly activated (dephosphorylated) only in leucine-stimulated control cells. Pre-treatment of the cells with PD98059 (ERK1/2 kinase inhibitor) prevented the phosphorylation of ERK1/2 and decreased the leucine-induced phosphorylation of p70S6K. It is concluded that WY increased the leucine-induced phosphorylation of target proteins involving in translation initiation via ERK/p70S6K pathway, but impaired the signaling for elongation process, suggesting that p70S6K phosphorylation may be essential, but not sufficient for the activation of entire targets for protein translation in WY-treated cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbagen.2008.06.002DOI Listing
October 2008

Essential role of satellite cells in the growth of rat soleus muscle fibers.

Am J Physiol Cell Physiol 2008 Aug 4;295(2):C458-67. Epub 2008 Jun 4.

Graduate School of Medicine, Osaka University, Osaka, Japan.

Effects of gravitational loading or unloading on the growth-associated increase in the cross-sectional area and length of fibers, as well as the total fiber number, in soleus muscle were studied in rats. Furthermore, the roles of satellite cells and myonuclei in growth of these properties were also investigated. The hindlimb unloading by tail suspension was performed in newborn rats from postnatal day 4 to month 3 with or without 3-mo reloading. The morphological properties were measured in whole muscle and/or single fibers sampled from tendon to tendon. Growth-associated increases of soleus weight and fiber cross-sectional area in the unloaded group were approximately 68% and 69% less than the age-matched controls. However, the increases of number and length of fibers were not influenced by unloading. Growth-related increases of the number of quiescent satellite cells and myonuclei were inhibited by unloading. And the growth-related decrease of mitotically active satellite cells, seen even in controls (20%, P > 0.05), was also stimulated (80%). The increase of myonuclei during 3-mo unloading was only 40 times vs. 92 times in controls. Inhibited increase of myonuclear number was not related to apoptosis. The size of myonuclear domain in the unloaded group was less and that of single nuclei, which was decreased by growth, was larger than controls. However, all of these parameters, inhibited by unloading, were increased toward the control levels generally by reloading. It is suggested that the satellite cell-related stimulation in response to gravitational loading plays an essential role in the cross-sectional growth of soleus muscle fibers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpcell.00497.2007DOI Listing
August 2008

Clinical aspects of physical exercise for diabetes/metabolic syndrome.

Diabetes Res Clin Pract 2007 Sep 11;77 Suppl 1:S87-91. Epub 2007 May 11.

Department of Health Science, Faculty of Psychological and Physical Science, Aichi Gakuin University, Nisshin 470-0195, Japan.

Evidence-based medicine (EBM) has come to be regarded as essential in all fields of medical sciences and practical medicine. In the field of diabetes and exercise, among the epidemiological studies of physical exercise, recent mega-trials such as the Diabetes Prevention Program (DPP) in the U.S. have shown that lifestyle intervention programs involving diet and/or exercise reduce the progression of impaired glucose tolerance (IGT) to type 2 diabetes. In studies examining the endocrinological and metabolic effects of exercise, it has been demonstrated that physical exercise promotes the utilization of blood glucose and free fatty acids in muscles and lowers blood glucose levels in well-controlled diabetic patients. Long-term, mild, regular jogging increases the action of insulin in both carbohydrate and lipid metabolism without influencing body mass index or maximal oxygen uptake. A significant correlation has been observed between delta MCR (Deltainsulin sensitivity) and the average number of steps performed in a day. Our recent data suggested that the improved effectiveness of insulin that occurs as a result of physical exercise is attributable, at least in part, to increases in GLUT4 protein, IRS1 and PI3-kinase protein in skeletal muscle. As a prescription for exercise, aerobic exercise of mild to moderate intensity, including walking and jogging, 10-30 min a day, 3-5 days a week, is recommended. Resistance training of mild intensity with the use of light dumbbells and stretch cords should be combined in elderly individuals who have decreased muscle strength. An active lifestyle is essential in the management of diabetes, which is one of typical lifestyle-related diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.diabres.2007.01.039DOI Listing
September 2007

Leucine-induced activation of translational initiation is partly regulated by the branched-chain alpha-keto acid dehydrogenase complex in C2C12 cells.

Biochem Biophys Res Commun 2006 May 22;343(4):1244-50. Epub 2006 Mar 22.

Department of Health and Sports Sciences, Graduate School of Medicine, Osaka University, Osaka 560-0043, Japan.

Branched-chain amino acid leucine has been shown to activate the translational regulators through the mammalian target of rapamycin. However, the leucine's effects are self-limiting because leucine promotes its own disposal by an oxidative pathway. The irreversible and rate-limiting step in the leucine oxidation pathway is catalyzed by the branched-chain alpha-keto acid dehydrogenase (BCKDH) complex. The complex contains E1 (alpha2beta2), E2, and E3 subunits, and its activity is abolished by phosphorylation of the E1alpha subunit by BCKDH kinase. The relationship between the activity of BCKDH complex and leucine-mediated activation of the protein translation was investigated using the technique of RNA interference. The activity of BCKDH complex in C2C12 cell was modulated by transfection of small interfering RNA (siRNA) for BCKDH E2 subunit or BCKDH kinase. Transfection of siRNAs decreased the mRNA expression and protein amount of corresponding gene. Suppression of either E2 subunit or kinase produced opposite effects on the cell proliferation and the activation of translational regulators by leucine. Suppression of BCKDH kinase for 48h resulted in decreasing cell proliferation. In contrast, E2 suppression led to increased amount of total cellular protein. The phosphorylation of p70 S6 kinase by leucine was increased in E2-siRNA transfected C2C12 cells, whereas the leucine's effect was diminished in kinase-siRNA transfected cells. These results suggest that the activation of the translational regulators by leucine was partly regulated by the activity of BCKDH complex.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbrc.2006.03.074DOI Listing
May 2006