scholarly journals REDD2 expression in rat skeletal muscle correlates with nutrient-induced activation of mTORC1: responses to aging, immobilization, and remobilization

2015 ◽  
Vol 308 (2) ◽  
pp. E122-E129 ◽  
Author(s):  
Andrew R. Kelleher ◽  
Suzette L. Pereira ◽  
Leonard S. Jefferson ◽  
Scot R. Kimball
Keyword(s):  
Skeletal Muscle ◽  
Mrna Expression ◽  
Muscle Mass ◽  
Soleus Muscle ◽  
Sprague Dawley ◽  
Age Related ◽  
Sprague Dawley Rats ◽  
Mtorc1 Signaling ◽  
Elevated Expression ◽  
Old Rats

In a previous study (Kelleher AR, Kimball SR, Dennis MD, Schilder RJ, and Jefferson LS. Am J Physiol Endocrinol Metab 304: E229–236, 2013.), we observed a rapid (i.e., 1–3 days) immobilization-induced repression of mechanistic target of rapamycin complex 1 (mTORC1) signaling in hindlimb skeletal muscle of young (2-mo-old) rats that was associated with elevated expression of regulated in development and DNA-damage response (REDD) 1 and REDD2. The present study extends that observation to include an assessment of those parameters in soleus muscle of the immobilized hindlimb of various-aged rats as well as in response to remobilization. Male Sprague-Dawley rats aged 2, 9, and 18 mo were subjected to unilateral hindlimb immobilization for 7 days, whereas one group of the 9-mo-old animals underwent 7 days of remobilization. Soleus muscle mass-to-body mass ratio declined with age, with the loss of muscle mass following hindlimb immobilization being inversely proportional to age. Compared with 2-mo-old rats, the older rats exhibited reduced mTORC1 signaling in the nonimmobilized limb in association with elevated REDD2, but not REDD1, mRNA expression. In the 2-mo-old rats, 7 days of hindlimb immobilization attenuated mTORC1 signaling and induced REDD2, but not REDD1, mRNA expression. In contrast, hindlimb immobilization did not further attenuate the age-related reduction in mTORC1 signaling nor further enhance the age-related induction of REDD2 mRNA expression in 9- and 18-mo-old rats. Across ages, REDD1 mRNA was not impacted by immobilization. Finally, remobilization elevated mTORC1 signaling and lowered REDD2 mRNA expression, with no impact on REDD1 gene expression. In conclusion, changes in mTORC1 signaling associated with aging, immobilization, and remobilization were inversely proportional to alterations in REDD2 mRNA expression.

scholarly journals The mTORC1 signaling repressors REDD1/2 are rapidly induced and activation of p70S6K1 by leucine is defective in skeletal muscle of an immobilized rat hindlimb

2013 ◽  
Vol 304 (2) ◽  
pp. E229-E236 ◽  
Author(s):  
Andrew R. Kelleher ◽  
Scot R. Kimball ◽  
Michael D. Dennis ◽  
Rudolf J. Schilder ◽  
Leonard S. Jefferson
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Molecular Mechanisms ◽  
Bed Rest ◽  
Disuse Atrophy ◽  
Sprague Dawley ◽  
Ribosomal Protein S6 ◽  
Sprague Dawley Rats ◽  
Mtorc1 Signaling ◽  
Limb Immobilization

Limb immobilization, limb suspension, and bed rest cause substantial loss of skeletal muscle mass, a phenomenon termed disuse atrophy. To acquire new knowledge that will assist in the development of therapeutic strategies for minimizing disuse atrophy, the present study was undertaken with the aim of identifying molecular mechanisms that mediate control of protein synthesis and mechanistic target of rapamycin complex 1 (mTORC1) signaling. Male Sprague-Dawley rats were subjected to unilateral hindlimb immobilization for 1, 2, 3, or 7 days or served as nonimmobilized controls. Following an overnight fast, rats received either saline or l-leucine by oral gavage as a nutrient stimulus. Hindlimb skeletal muscles were extracted 30 min postgavage and analyzed for the rate of protein synthesis, mRNA expression, phosphorylation state of key proteins in the mTORC1 signaling pathway, and mTORC1 signaling repressors. In the basal state, mTORC1 signaling and protein synthesis were repressed within 24 h in the soleus of an immobilized compared with a nonimmobilized hindlimb. These responses were accompanied by a concomitant induction in expression of the mTORC1 repressors regulated in development and DNA damage responses (REDD) 1/2. The nutrient stimulus produced an elevation of similar magnitude in mTORC1 signaling in both the immobilized and nonimmobilized muscle. In contrast, phosphorylation of 70-kDa ribosomal protein S6 kinase 1 (p70S6K1) on Thr229 and Thr389 in response to the nutrient stimulus was severely blunted. Phosphorylation of Thr229 by PDK1 is a prerequisite for phosphorylation of Thr389 by mTORC1, suggesting that signaling through PDK1 is impaired in response to immobilization. In conclusion, the results show an immobilization-induced attenuation of mTORC1 signaling mediated by induction of REDD1/2 and defective p70S6K1 phosphorylation.

scholarly journals Analysis of Chemokines and Receptors Expression Profile in the Myelin MutantTaiepRat

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Guadalupe Soto-Rodriguez ◽  
Juan-Antonio Gonzalez-Barrios ◽  
Daniel Martinez-Fong ◽  
Victor-Manuel Blanco-Alvarez ◽  
Jose R. Eguibar ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Expression Profile ◽  
Proinflammatory Cytokines ◽  
Mrna Levels ◽  
Pcr Array ◽  
Sprague Dawley ◽  
Protein Levels ◽  
Chronic Neuroinflammation ◽  
Sprague Dawley Rats ◽  
Old Rats

Taieprat has a failure in myelination and remyelination processes leading to a state of hypomyelination throughout its life. Chemokines, which are known to play a role in inflammation, are also involved in the remyelination process. We aimed to demonstrate that remyelination-stimulating factors are altered in the brainstem of 1- and 6-month-oldtaieprats. We used a Rat RT2Profiler PCR Array to assess mRNA expression of 84 genes coding for cytokines, chemokines, and their receptors. We also evaluated protein levels of CCL2, CCR1, CCR2, CCL5, CCR5, CCR8, CXCL1, CXCR2, CXCR4, FGF2, and VEGFA by ELISA. Sprague-Dawley rats were used as a control. PCR Array procedure showed that proinflammatory cytokines were not upregulated in thetaieprat. In contrast, some mRNA levels of beta and alpha chemokines were upregulated in 1-month-old rats, but CXCR4 was downregulated at their 6 months of age. ELISA results showed that CXCL1, CCL2, CCR2, CCR5, CCR8, and CXCR4 protein levels were decreased in brainstem at the age of 6 months. These results suggest the presence of a chronic neuroinflammation process with deficiency of remyelination-stimulating factors (CXCL1, CXCR2, and CXCR4), which might account for the demyelination in thetaieprat.

Skeletal muscle Ca2+ flux and catabolic response during sepsis

1993 ◽  
Vol 265 (3) ◽  
pp. R487-R493 ◽  
Author(s):  
J. Bhattacharyya ◽  
K. D. Thompson ◽  
M. M. Sayeed
Keyword(s):  
Skeletal Muscle ◽  
Soleus Muscle ◽  
Experimental Sepsis ◽  
Protein Catabolism ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Rat Soleus Muscle ◽  
Catabolic Response ◽  
Net Protein

Membrane Ca2+ flux and net protein catabolism were studied in the skeletal muscle during experimental sepsis. Sterilized rat fecal pellets with (septic) or without (sterile) gram-negative bacteria, Escherichia coli [10(2) colony-forming units (cfu)] and Bacteroides fragilis (2 x 10(3) cfu), were implanted into the abdomens of male Sprague-Dawley rats (110-120 g). Septic and sterile rats were febrile and hyperlactacidemic on day 1 postimplantation. These responses subsided by day 2 in sterile but not septic rats. Initial Ca2+ flux, estimated from measurements of 45Ca uptake by soleus muscles in vitro, was elevated on day 1 in both sterile and septic rats and on day 2 and 3 in septic rats only. The septic rat soleus muscle showed a significantly increased net protein catabolic response (measured as tyrosine release by soleus muscle, in vitro) over that found in muscles of sterile rats on day 1-3 postimplantation. The increase in Ca2+ flux in septic (day 1-3 postimplantation) and sterile (day 1 only) rats was abolished when the rats were treated with the calcium channel blocker diltiazem. In unoperated control rat soleus muscles the Ca2+ ionophore, ionomycin, concomitantly caused an increase in Ca2+ flux and net protein catabolism. Overall, the present study suggested that altered cellular Ca2+ regulation plays a role in the net protein catabolic response in the skeletal muscle during sepsis.

scholarly journals Consequences of age-related splanchnic sequestration of leucine on interorgan glutamine metabolism in old rats

2013 ◽  
Vol 115 (2) ◽  
pp. 229-234 ◽  
Author(s):  
Marion Jourdan ◽  
Nicolaas E. P. Deutz ◽  
Luc Cynober ◽  
Christian Aussel
Keyword(s):  
Young Adult ◽  
De Novo ◽  
Vena Cava ◽  
Glutamine Metabolism ◽  
Whole Body ◽  
Sprague Dawley ◽  
Age Related ◽  
Sprague Dawley Rats ◽  
Old Rats ◽  
Body Level

Dietary leucine (Leu) serves as a nitrogen donor for de novo glutamine (Gln) synthesis in muscle. However, aging is characterized by an increase in the splanchnic extraction of Leu (SPELeu), i.e., splanchnic sequestration (SSLeu), which may affect muscle Gln metabolism and its subsequent homeostasis at the whole-body level. The aim of the work was to assess the effect of age-related SSLeu on Gln metabolism in the muscle, gut, liver, kidney, and Gln exchanges among these organs during fed conditions. Young-adult (3-mo-old) or aged (24-mo-old), male Sprague-Dawley rats were studied during fed condition [infusion of amino acids (AA) into the duodenum from time 0 min (T0) to T60] under anesthesia. L-[5-15N]Gln and L[1-13C]Leu were infused into the jugular vein and L-[5,5,5-2H3]Leu into the duodenum. At T60, blood samples were taken from carotid artery, portal vein, hepatic vein, renal vein, and inferior vena cava for tracer-tracee ratio and AA level measurements. SSLeu was observed in old rats and was negatively correlated with muscle Gln production ( r = −0.501, P < 0.01). In addition, reduced Gln muscle release in old rats was accompanied by reduced Gln uptake by the gut and kidney. However, net Gln balance across organs was not different between young adult and old rats. During fed conditions in old rats, muscle Gln production and release are reduced in relation to the observed, increased SPELeu and reduced renal and intestinal Gln uptake to maintain whole-body Gln homeostasis. Our results demonstrate the existence of an age-related change of interorgan Gln metabolism, which may be, in part, driven by SSLeu.

Age-related differences in apoptosis with disuse atrophy in soleus muscle

2005 ◽  
Vol 288 (5) ◽  
pp. R1288-R1296 ◽  
Author(s):  
Christiaan Leeuwenburgh ◽  
Cathy M. Gurley ◽  
Beau A. Strotman ◽  
Esther E. Dupont-Versteegden
Keyword(s):  
Skeletal Muscle ◽  
Soleus Muscle ◽  
Caspase 3 ◽  
Cross Sectional Area ◽  
Disuse Atrophy ◽  
Sectional Area ◽  
Cross Sectional ◽  
Age Related ◽  
Old Rats ◽  
Subsarcolemmal Mitochondria

Muscle atrophy is associated with a loss of muscle fiber nuclei, most likely through apoptosis. We investigated age-related differences in the extent of apoptosis in soleus muscle of young (6 mo) and old (32 mo) male Fischer 344 × Brown Norway rats subjected to acute disuse atrophy induced by 14 days of hindlimb suspension (HS). HS-induced atrophy (reduction in muscle weight and cross-sectional area) was associated with loss of myofiber nuclei in soleus muscle of young, but not old, rats. This resulted in a significant decrease in the myonuclear domain (cross-sectional area per nucleus) in young and old rats, with changes being more pronounced in old animals. Levels of apoptosis (TdT-mediated dUTP nick end labeling and DNA fragmentation) were higher in soleus muscles of old control rats than young animals. Levels were significantly increased with HS in young and old rats, with the greatest changes in old animals. Caspase-3 activity in soleus muscle tended to be increased with age, but changes were not statistically significant ( P = 0.052). However, with HS, caspase-3 activity significantly increased in young, but not old, rats. Immunohistochemistry showed that the proapoptotic endonuclease G (EndoG, a mitochondrion-specific nuclease) was localized in the subsarcolemmal mitochondria in control muscles, and translocation to the nucleus occurred in old, but not young, control animals. There was no difference between EndoG total protein content in young and old control rats, but EndoG increased almost fivefold in soleus muscle of old, but not young, rats after HS. These results show that deregulation of myonuclear number occurs in old skeletal muscle and that the pathways involved in apoptosis are distinct in young and old muscles. Apoptosis in skeletal muscle is partly mediated by the subsarcolemmal mitochondria through EndoG translocation to the nucleus in response to HS.

scholarly journals Age-related Changes in p56lckProtein Levels and Phenotypic Distribution of T Lymphocytes in Young Rats

2005 ◽  
Vol 12 (1) ◽  
pp. 75-84 ◽  
Author(s):  
Heather J. Hosea ◽  
Edward S. Rector ◽  
Carla G. Taylor
Keyword(s):  
T Cells ◽  
T Cell ◽  
Absolute Number ◽  
T Cell Subsets ◽  
Sprague Dawley ◽  
Double Positive ◽  
Cd8 Cells ◽  
Age Related ◽  
Sprague Dawley Rats ◽  
Old Rats

p56lckis involved in the maturation of T-cells from double negative (DN) into double positive (DP) T-cells. The objective of this experiment was to determine changes in the levels of thymic and splenic T-cell p56lckusing Western immunoblotting, along with the proportion and number of T-cell subsets in thymus, spleen and blood using flow cytometry in growing Sprague-Dawley rats. Thymic p56lcklevels were negatively correlated with age (r=-0.42,p=0.04) and positively correlated with age in the spleen (r=0.50,p=0.01). Nine-week-old rats had a higher percentage of thymic DN and CD8 cells with fewer DP cells compared to younger rats. There were minor differences in the proportions of T-cell subsets in the spleen and blood. T-cell numbers remained proportional to body weight in the lymphoid organs; however, the lower absolute number of T-cells in the younger rats might indicate that they are less able to respond to antigens.

scholarly journals Effects of short-term GH supplementation and treadmill exercise training on physical performance and skeletal muscle apoptosis in old rats

2008 ◽  
Vol 294 (2) ◽  
pp. R558-R567 ◽  
Author(s):  
Emanuele Marzetti ◽  
Leanne Groban ◽  
Stephanie E. Wohlgemuth ◽  
Hazel A. Lees ◽  
Marina Lin ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Exercise Training ◽  
Physical Performance ◽  
Soleus Muscle ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Advanced Age ◽  
Short Term ◽  
Age Related ◽  
Old Rats

Growth hormone (GH) supplementation at old age has been shown to improve body composition, although its effect on muscle performance is still debated. On the other hand, resistance training increases muscle mass and strength even when initiated at advanced age. In the present study, we investigated the effects of short-term GH supplementation and exercise training on physical performance and skeletal muscle apoptosis in aged rats. Old (28 mo) male Fischer 344 × Brown Norway rats were randomized to 4 wk of GH supplementation (300 μg subcutaneous, twice daily) or 4 wk of treadmill running or used as sedentary controls. Eight-month-old rats, sedentary or exercised, were used as young controls. Exercise training improved exercise capacity and muscle strength in old animals. In soleus muscle, age and exercise were not associated with significant changes in the extent of apoptosis. However, we detected an age-related increase of cleaved caspase-8 (+98%), cleaved caspase-3 (+136%), and apoptotic DNA fragmentation (+203%) in the extensor digitorum longus muscle of old sedentary rats, which was attenuated by exercise. GH administration neither ameliorated physical performance nor attenuated apoptosis in extensor digitorum longus and was associated with increased apoptosis in soleus muscle (+206% vs. old controls). Our findings indicate that a short-term program of exercise training started at advanced age reverses age-related skeletal muscle apoptosis and represents an effective strategy to improve physical performance. In contrast, short-term administration of GH late in life does not provide any protection against functional decline or muscle aging and may even accelerate apoptosis in slow-twitch muscles, such as the soleus.

A farnesyltransferase inhibitor attenuated β-adrenergic receptor downregulation in rat skeletal muscle

2002 ◽  
Vol 282 (1) ◽  
pp. R317-R322 ◽  
Author(s):  
Julie L. Lavoie ◽  
Angelino Calderone ◽  
Louise Béliveau
Keyword(s):  
Skeletal Muscle ◽  
Soleus Muscle ◽  
Adrenergic Receptor ◽  
Cardiac Fibroblasts ◽  
Medial Gastrocnemius ◽  
Sprague Dawley ◽  
Farnesyltransferase Inhibitor ◽  
Concurrent Administration ◽  
Sprague Dawley Rats ◽  
Muscle Types

Farnesylation represents an essential posttranslational modification of several well-defined proteins implicated in the homologous desensitization of the β-adrenergic receptor (β-ADR). The following study examined the effect of a novel farnesyltransferase inhibitor, BMS-191563, on agonist-mediated β-ADR downregulation in skeletal muscle. Female Sprague-Dawley rats were treated for 12 days with the β2-adrenergic agonist clenbuterol (4 mg/kg) with or without the concurrent administration of BMS-191563 (2 mg · kg−1 · day−1). Clenbuterol promoted gastrocnemius muscle hypertrophy, whereas the soleus muscle was unaffected. Total β-ADR density was decreased by 45 and 40% in the soleus and medial gastrocnemius (MG), respectively, after clenbuterol treatment. BMS-191563 treatment did not prevent clenbuterol-stimulated MG hypertrophy, but markedly attenuated β-ADR downregulation in both muscle types. This latter effect in the soleus muscle was not associated with the inhibition of Ras farnesylation. Likewise, in rat cardiac fibroblasts, isoproterenol-mediated decrease of total β-ADR density was abrogated by the prior treatment with BMS-191563. Collectively, these data demonstrate that the mechanism(s) implicated in agonist-mediated β-ADR downregulation was sensitive to BMS-191563, thereby suggesting the involvement of farnesylated proteins.

Age-related variation in circadian rhythms of mitosis in the adrenal cortex of the male rat

1989 ◽  
Vol 120 (2) ◽  
pp. 307-310 ◽  
Author(s):  
A. M. McNicol ◽  
I. D. Penman ◽  
A. E. Duffy
Keyword(s):  
Circadian Rhythm ◽  
Adrenal Cortex ◽  
Hpa Axis ◽  
Proliferative Activity ◽  
Male Rat ◽  
Sprague Dawley ◽  
Metaphase Arrest ◽  
Age Related ◽  
Sprague Dawley Rats ◽  
Old Rats

ABSTRACT Using a metaphase arrest technique, mitotic activity was quantified in the adrenal cortex over a 24-h period in 14-day-old male Sprague–Dawley rats before functional rhythmicity of the hypothalamic pituitary-adrenal (HPA) axis is established, and after its onset, in 6- to 7-week-old rats. At all times, proliferative activity was greater in the younger animals, as previously reported. A significant circadian rhythm was identified in both groups, but the timing of the peak differed, lying between 17.00 and 21.00 h at 14 days and 11.00 and 15.00 h at 6–7 weeks. These results raise the possibility that functional rhythmicity of the HPA axis may alter an inherent proliferative rhythm. Journal of Endocrinology (1989) 120, 307–310

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