scholarly journals Effects of hyperthyroidism and hypothyroidism on glutamine metabolism by skeletal muscle of the rat

1990 ◽  
Vol 272 (2) ◽  
pp. 319-322 ◽  
Author(s):  
M Parry-Billings ◽  
G D Dimitriadis ◽  
B Leighton ◽  
J Bond ◽  
S J Bevan ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Soleus Muscle ◽  
Gastrocnemius Muscle ◽  
Glutamine Metabolism ◽  
Thyroid Status ◽  
Pathological Conditions ◽  
Per Se

1. The effects of hyperthyroidism and hypothyroidism on the concentrations of glutamine and other amino acids in the muscle and plasma and on the rates of glutamine and alanine release from incubated isolated stripped soleus muscle of the rat were investigated. 2. Hyperthyroidism decreased the concentration of glutamine in soleus muscle but was without effect on that in the gastrocnemius muscle or in the plasma. Hyperthyroidism also increased markedly the rate of release of glutamine from the incubated soleus muscle. 3. Hypothyroidism decreased the concentrations of glutamine in the gastrocnemius muscle and plasma but was without effect on that in soleus muscle. Hypothyroidism also decreased markedly the rate of glutamine release from the incubated soleus muscle. 4. Thyroid status was found to have marked effects on the rate of glutamine release by skeletal muscle per se, and may be important in the control of this process in both physiological and pathological conditions.

Structural and functional remodeling of skeletal muscle microvasculature is induced by simulated microgravity

2000 ◽  
Vol 278 (6) ◽  
pp. H1866-H1873 ◽  
Author(s):  
Michael D. Delp ◽  
Patrick N. Colleran ◽  
M. Keith Wilkerson ◽  
Matthew R. McCurdy ◽  
Judy Muller-Delp
Keyword(s):  
Skeletal Muscle ◽  
Soleus Muscle ◽  
Skeletal Muscles ◽  
Gastrocnemius Muscle ◽  
Fluid Pressure ◽  
Hindlimb Unloading ◽  
Cross Sectional ◽  
Luminal Diameter ◽  
Structural Remodeling

Hindlimb unloading of rats results in a diminished ability of skeletal muscle arterioles to constrict in vitro and elevate vascular resistance in vivo. The purpose of the present study was to determine whether alterations in the mechanical environment (i.e., reduced fluid pressure and blood flow) of the vasculature in hindlimb skeletal muscles from 2-wk hindlimb-unloaded (HU) rats induces a structural remodeling of arterial microvessels that may account for these observations. Transverse cross sections were used to determine media cross-sectional area (CSA), wall thickness, outer perimeter, number of media nuclei, and vessel luminal diameter of feed arteries and first-order (1A) arterioles from soleus and the superficial portion of gastrocnemius muscles. Endothelium-dependent dilation (ACh) was also determined. Media CSA of resistance arteries was diminished by hindlimb unloading as a result of decreased media thickness (gastrocnemius muscle) or reduced vessel diameter (soleus muscle). ACh-induced dilation was diminished by 2 wk of hindlimb unloading in soleus 1A arterioles, but not in gastrocnemius 1A arterioles. These results indicate that structural remodeling and functional adaptations of the arterial microvasculature occur in skeletal muscles of the HU rat; the data suggest that these alterations may be induced by reductions in transmural pressure (gastrocnemius muscle) and wall shear stress (soleus muscle).

Modulation of muscle protein synthesis by insulin is maintained during neonatal endotoxemia

2006 ◽  
Vol 291 (1) ◽  
pp. E159-E166 ◽  
Author(s):  
Renan A. Orellana ◽  
Pamela M. J. O'Connor ◽  
Jill A. Bush ◽  
Agus Suryawan ◽  
M. Carole Thivierge ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Gastrocnemius Muscle ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Liver Protein ◽  
Fasting Insulin ◽  
Neonatal Pigs

Sepsis promotes insulin resistance and reduces protein synthesis in skeletal muscle of adults. The effect of sepsis on insulin-stimulated muscle protein synthesis has not been determined in neonates, a highly anabolic population that is uniquely sensitive to insulin. Overnight fasted neonatal pigs were infused for 8 h with endotoxin [lipopolysaccharide (LPS), 0 and 10 μg·kg−1·h−1]. Glucose and amino acids were maintained at fasting levels, insulin was clamped at either fasting or fed (2 or 10 μU/ml) levels, and fractional protein synthesis rates were determined at the end of the infusion. LPS infusion induced a septic-like state, as indicated by a sustained elevation in body temperature, heart rate, and cortisol. At fasting insulin levels, LPS reduced fractional protein synthesis rates in gastrocnemius muscle (−26%) but had no effect on the masseter and heart. By contrast, LPS stimulated liver protein synthesis (+28%). Increasing insulin to fed levels accelerated protein synthesis rates in gastrocnemius (controls by +38%, LPS by +60%), masseter (controls by +50%, LPS by +43%), heart (controls by +34%, LPS by +40%), and diaphragm (controls by +54%, LPS by +29%), and the response to insulin was similar in LPS and controls. Insulin did not alter protein synthesis in liver, kidney, or jejunum in either group. These findings suggest that acute endotoxemia lowers basal fasting muscle protein synthesis in neonates but does not alter the response of protein synthesis to insulin.

scholarly journals Physiological glucocorticoid levels regulate glutamine and insulin-mediated glucose metabolism in skeletal muscle of the rat. Studies with RU 486 (mifepristone)

1991 ◽  
Vol 274 (1) ◽  
pp. 187-192 ◽  
Author(s):  
B Leighton ◽  
M Parry-Billings ◽  
G Dimitriadis ◽  
J Bond ◽  
E A Newsholme ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Soleus Muscle ◽  
Plasma Glucose ◽  
Dark Period ◽  
Feeding Activity ◽  
Glycogen Synthesis ◽  
Glutamine Metabolism ◽  
Ru 486

This study examined the effects of antagonism of the peak level of glucocorticoids in vivo, which occurs as rats enter the feeding/activity (dark) period on glucose and glutamine metabolism in incubated isolated rat soleus muscle preparations. Thus the rats were treated with the potent glucocorticoid antagonist RU 486 2 h before and 1 and 2 h into the dark period. Both the content of glutamine in skeletal muscle in vivo and plasma glucose and glutamine concentrations were elevated midway through the dark period, compared with the beginning of the period. RU 486 prevented the increases in plasma glucose and glutamine and caused a significant decrease in both the rate of release of glutamine in soleus muscle in vitro and the content of glutamine in gastrocnemius muscle. The sensitivity of soleus muscle to insulin in vitro is markedly decreased when isolated midway through the dark period (i.e. at 03:00 h) [Leighton, Kowalchuk, Challiss & Newsholme (1988) Am. J. Physiol. 255, E41-E45]. We now show that the concentrations of insulin required to stimulate lactate formation and glycogen synthesis half-maximally were 95 and 250 muunits/ml respectively, and treatment of rats with RU 486 decreased these values to 55 and 90 muunits of insulin/ml respectively. Thus antagonism of the action of the normal circadian rise in the level of glucocorticoids in rats reverses insulin insensitivity in soleus muscles in vitro.

scholarly journals PO-242 Effects of tail suspension on the expression of FNDC5/Irisin protein in rat skeletal muscle

2018 ◽  
Vol 1 (5) ◽  
Author(s):  
Junzhi Sun ◽  
Qiang Jiang
Keyword(s):  
Skeletal Muscle ◽  
Protein Expression ◽  
Muscle Atrophy ◽  
Muscle Fiber ◽  
Soleus Muscle ◽  
Gastrocnemius Muscle ◽  
Skeletal Muscle Atrophy ◽  
Type I ◽  
Tail Suspension ◽  
Gastrocnemius Muscles

Objective Irisin is a myokine secreted by skeletal muscle,and it is a type I membrane protein factor encoded by the protein 5(FNDC5) gene after cleavage and modification of the type III fibronectin component.Dependence of peroxisome proliferator-activated receptor gamma coactivator (PGC-1α).In this study, the potential association between skeletal muscle atrophy and irisin was explored by detecting changes in rat soleus and gastrocnemius irisin-related proteins during unloading. Methods Twenty male 8-week rats were randomly divided into control group C (n=10) and suspension group T (n=10). The tail suspension system (TSS) was used to perform a 2-week tail suspension experiment on the T group. Two weeks after the tail suspension test, the weights of the rats and the wet weights of soleus and gastrocnemius muscles were measured. HE staining was performed under light microscope to observe the changes of muscle fiber area of skeletal muscle in each group. Western-blot was used to detect the protein expression of MURF1, PGC-1α and FNDC5 in soleus muscle and gastrocnemius muscle of each group. Results (1) The soleus muscle and gastrocnemius muscle mass in T group decreased by 28.6% (P<0.05) and 25.8% (P<0.01), respectively. (2) The cross-sectional area of soleus muscle and gastrocnemius muscle fiber in T group decreased by 20.5% (P<0.01) and 25.2% (P<0.05), respectively. (3) The MURF1 protein expression in the gastrocnemius muscle and soleus muscle in the T group was significantly higher than that in the C group (P<0.01). (4) The expression of PGC-1α protein in gastrocnemius muscle and soleus muscle of T group was significantly lower than that in group C (P<0.05). (5) The expression of FNDC5 protein in gastrocnemius muscle and soleus muscle in T group was significantly lower than that in group C (P<0.05). Conclusions After sole tail suspension for two weeks, the soleus and gastrocnemius muscles of the rats were obviously atrophied, and soleus muscle atrophy was more obvious. Skeletal muscle atrophy may be related to increased expression of MURF1. The decrease of FNDC5/Irisin content may be related to the occurrence of skeletal muscle atrophy, and PGC-1α also may be involved in this process.

Plasma and skeletal muscle free amino acids in type I, insulin-treated diabetic subjects

Diabetes ◽  
1985 ◽  
Vol 34 (8) ◽  
pp. 812-815 ◽  
Author(s):  
L. Borghi ◽  
R. Lugari ◽  
A. Montanari ◽  
P. Dall'Argine ◽  
G. F. Elia ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Free Amino Acids ◽  
Free Amino ◽  
Type I

scholarly journals Autophagy Deficiency by Atg4B Loss Leads to Metabolomic Alterations in Mice

Metabolites ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 481
Author(s):  
Gemma G. Martínez-García ◽  
Raúl F. Pérez ◽  
Álvaro F. Fernández ◽  
Sylvere Durand ◽  
Guido Kroemer ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Mammalian Cells ◽  
Tissue Homeostasis ◽  
In Vivo Studies ◽  
Protective Mechanism ◽  
Cardiac Damage ◽  
Wide Range ◽  
First Time

Autophagy is an essential protective mechanism that allows mammalian cells to cope with a variety of stressors and contributes to maintaining cellular and tissue homeostasis. Due to these crucial roles and also to the fact that autophagy malfunction has been described in a wide range of pathologies, an increasing number of in vivo studies involving animal models targeting autophagy genes have been developed. In mammals, total autophagy inactivation is lethal, and constitutive knockout models lacking effectors of this route are not viable, which has hindered so far the analysis of the consequences of a systemic autophagy decline. Here, we take advantage of atg4b−/− mice, an autophagy-deficient model with only partial disruption of the process, to assess the effects of systemic reduction of autophagy on the metabolome. We describe for the first time the metabolic footprint of systemic autophagy decline, showing that impaired autophagy results in highly tissue-dependent alterations that are more accentuated in the skeletal muscle and plasma. These changes, which include changes in the levels of amino-acids, lipids, or nucleosides, sometimes resemble those that are frequently described in conditions like aging, obesity, or cardiac damage. We also discuss different hypotheses on how impaired autophagy may affect the metabolism of several tissues in mammals.

scholarly journals 146 Prematurity Blunts the Protein Synthetic Response of Skeletal Muscle to Insulin and Amino Acids

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 118-119
Author(s):  
Teresa A Davis ◽  
Marko Rudar ◽  
Jane Naberhuis ◽  
Agus Suryawan ◽  
Marta Fiorotto
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Body Weight Gain ◽  
Human Infant ◽  
Long Term Effects ◽  
Plasma Insulin Concentration ◽  
Akt Phosphorylation ◽  
Relative Body Weight

Abstract Livestock animals are important dual-purpose models that benefit both agricultural and biomedical research. The neonatal pig is an appropriate model for the human infant to assess long-term effects of early life nutrition on growth and metabolic outcomes. Previously we have demonstrated that prematurity blunts the feeding-induced stimulation of translation initiation and protein synthesis in skeletal muscle of neonatal pigs. The objective of this study was to determine whether reduced sensitivity to insulin and/or amino acids drives this blunted response. Pigs were delivered by caesarean section at preterm (PT, 103 d gestation) or at term (T, 112 d gestation) and fed parenterally for 4 d. On day 4, pigs were subject to euinsulinemic-euaminoacidemic-euglycemic (FAST), hyperinsulinemic-euaminoacidemic-euglycemic (INS), or euinsulinemic-hyperaminoacidemic-euglycemic (AA) clamps for 120 min, yielding six treatments: PT-FAST (n = 7), PT-INS (n = 9), PT-AA (n = 9), T-FAST (n = 8), T-INS (n = 9), and T-AA (n = 9). A flooding dose of L-[4-3H]Phe was injected into pigs 30 min before euthanasia. Birth weight and relative body weight gain were lower in PT than T pigs (P &lt; 0.001). Plasma insulin concentration was increased from ~3 to ~100 µU/mL in INS compared to FAST and AA pigs (P &lt; 0.001); plasma BCAA concentration was increased from ~250 to ~1,000 µmol/L in AA compared to FAST and INS pigs (P &lt; 0.001). Despite achieving similar insulin and amino acid levels, longissimus dorsi AKT phosphorylation, mechanistic target of rapamycin (mTOR)·Rheb abundance, mTOR activation, and protein synthesis were lower in PT-INS than T-INS pigs (Table 1). Although amino-acid induced dissociation of Sestrin2 from GATOR2 was not affected by prematurity, mTOR·RagA abundance, mTOR·RagC abundance, mTOR activation, and protein synthesis were lower in PT-AA than T-AA pigs. The impaired capacity of premature skeletal muscle to respond to insulin or amino acids and promote protein synthesis likely contributes to reduced lean mass accretion. Research was supported by NIH and USDA.

Dietary protein paradox: decrease of amino acid availability induced by high-protein diets

1993 ◽  
Vol 264 (6) ◽  
pp. G1057-G1065 ◽  
Author(s):  
C. Moundras ◽  
C. Remesy ◽  
C. Demigne
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Dietary Protein ◽  
High Protein ◽  
Glutamine Metabolism ◽  
Metabolic Adaptation ◽  
Casein Diet ◽  
Serine Dehydratase ◽  
High Protein Diets ◽  
Protein Diets

The aim of the present study was to evaluate the effect of changes in dietary protein level on overall availability of amino acids for tissues. For this purpose, rats were adapted to diets containing various concentrations of casein (7.5, 15, 30, and 60%) and were sampled either during the postprandial or postabsorptive period. In rats fed the protein-deficient diet, glucogenic amino acids (except threonine) tended to accumulate in plasma, liver, and muscles. In rats fed high-protein diets, the hepatic balance of glucogenic amino acids was markedly enhanced and their liver concentrations were consistently depressed. This response was the result of a marked induction of amino acid catabolism (a 45-fold increase of liver threonine-serine dehydratase activity was observed with the 60% casein diet). The muscle concentrations of threonine, serine, and glycine underwent changes parallel to plasma and liver concentrations, and a significant reduction of glutamine was observed. During the postabsorptive period, adaptation to high-protein diets resulted in a sustained catabolism of most glucogenic amino acids, which accentuated the drop in their concentrations (especially threonine) in all the compartments studied. The time course of metabolic adaptation from a 60 to a 15% casein diet has also been investigated. Adaptation of alanine and glutamine metabolism was rapid, whereas that of threonine, serine, and glycine was delayed and required 7-11 days. This was paralleled by a relatively slow decay of liver threonine-serine dehydratase (T-SDH) activity in contrast to the rapid adaptation of pyruvate kinase activity after refeeding a high-carbohydrate diet.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Identification in skeletal muscle of a distinct extracellular pool of amino acids, and its role in protein synthesis

1971 ◽  
Vol 121 (5) ◽  
pp. 817-827 ◽  
Author(s):  
R. C. Hider ◽  
E. B. Fern ◽  
D. R. London
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Incubation Medium ◽  
Extensor Digitorum Longus ◽  
Extensor Digitorum ◽  
Longus Muscle ◽  
Kinetics Of

1. The kinetics of radioactive labelling of extra- and intra-cellular amino acid pools and protein of the extensor digitorum longus muscle were studied after incubations with radioactive amino acids in vitro. 2. The results indicated that an extracellular pool could be defined, the contents of which were different from those of the incubation medium. 3. It was concluded that amino acids from the extracellular pool, as defined in this study, were incorporated directly into protein.

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