Effects of experimental hyperthyroidism on protein turnover in skeletal and cardiac muscle as measured by [14C]tyrosine infusion.
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ABSTRACT:
SUBMITTER: Carter WJ
PROVIDER: S-EPMC1158316 | biostudies-other | 1982 Apr
REPOSITORIES: biostudies-other
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Project description:It is not clear whether the muscle wasting commonly observed in hyperthyroidism is due to alteration in the rate of protein synthesis or degradation. The effect of experimental hyperthyroidism on skeletal-muscle proteolysis in the rat was studied by measuring alanine and tyrosine release from isolated skeletal muscles in vitro and 3-methyl-histidine excretion in vivo. Alanine release from the isolated epitrochlaris-muscle preparation was increased as soon as 24h after a 25 microgram dose of L-tri-iodothyronine in vivo. Conversely, alanine release from muscles of hypothyroid rats was decreased, but restored by L-tri-iodothyronine supplementation before death. Furthermore, 3-methylhistidine excretion was increased in hyperthyroid rats throughout an 18-day treatment period. The increased amino acid release from isolated muscles and the increased 3-methylhistidine excretion in vivo strongly suggests that hyperthyroidism increases skeletal-muscle proteolysis. Furthermore, the thyroid-hormone concentration may be an important factor in regulating muscle proteolysis.
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Project description:Aim. Hyperthyroidism reduces the oxidative capacity of skeletal muscle (SKM) and promotes development of a glycolytic phenotype by altering the expression of metabolic proteins. Our previous results showed that smoothelin-like protein 1 (SMTNL1), a transcriptional coregulator, promotes insulin sensitivity in SKM. Our aim was to elucidate the role of SMTNL1 in SKM under physiological and pathological 3,3′,5-Triiodo-L-thyronine (T3) concentrations. Methods. Human hyper- and euthyroid SKM biopsies were used for microarray analysis and phospho-kinase arrays. Physiological and hyperthyroid concentrations of T3 were applied on differentiated C2C12 cells upon SMTNL1 overexpression to assess the activity and expression level of the element of insulin signaling. Real-time metabolic measurements of oxygen consumption rate and extracellular acidification rate were measured. Results. Expression of genes related to energy production, nucleic acid- and lipid metabolism were changed significantly in hyperthyroid samples. SMTNL1 expression decreased in the hyperthyroid samples and in T3 treated C2C12 cells. SMTNL1 regulated muscle cell differentiation and compensated for the glycolytic shift in SKM triggered by pathological T3 exposure. Moreover, it selectively regulated TR expression at the transcriptional level. T3 excess triggered the development of insulin resistance while overexpression of SMTNL1 induced insulin sensitivity through the inhibition of JNK activity and hampered the non-genomic effects of T3 by decreasing the activity of ERK1/2 through PKC. SMTNL1 overexpression induced GLUT4 expression in hyperthyroid model to restore the normal responsiveness of glucose transport to insulin. SMTNL1 regulated glucose phosphorylation and balances glycolysis and glycogen synthesis via the downregulation of hexokinase II. T3 overload strongly increased the rate of lactate production, while SMTNL1 overexpression antagonizes the T3 effects. Conclusion. These lines of evidence suggest that SMTNL1 potentially prevents hyperthyroidism-induced changes in SKM and it holds great promise as a novel therapeutic target. Smoothelin-like Protein 1 in Hyperthyroidism
2021-10-27 | GSE178996 | GEO
Project description:It is appreciated that aerobic endurance exercise can attenuate unfavorable myocardial remodeling following myocardial infarction. In contrast, little is known about the effects of increasing skeletal muscle mass, typically achieved through resistance training, on this process. Here, we utilized transgenic (TG) mice that can induce the growth of functional skeletal muscle by switching Akt1 signaling in muscle fibers to assess the impact of glycolytic muscle growth on post-myocardial infarction cardiac remodeling.Male-noninduced TG mice and their nontransgenic littermates (control) were subjected to left anterior coronary artery ligation. Two days after surgery, mice were provided doxycycline in their drinking water to activate Akt1 transgene expression in a skeletal muscle-specific manner. Myogenic Akt1 activation led to diminished left ventricular dilation and reduced contractile dysfunction compared with control mice. Improved cardiac function in Akt1 TG mice was coupled to diminished myocyte hypertrophy, decreased interstitial fibrosis, and increased capillary density. ELISA and protein array analyses demonstrated that serum levels of proangiogenic growth factors were upregulated in Akt1 TG mice compared with control mice. Cardiac eNOS was activated in Akt1 TG mice after myocardial infarction. The protective effect of skeletal muscle Akt activation on cardiac remodeling and systolic function was abolished by treatment with the eNOS inhibitor l-NAME.Akt1-mediated skeletal muscle growth attenuates cardiac remodeling after myocardial infarction and is associated with an increased capillary density in the heart. This improvement appears to be mediated by skeletal muscle to cardiac communication, leading to activation of eNOS-signaling in the heart.
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Project description:Skeletal muscle atrophy is associated with a disruption in protein turnover involving increased protein degradation and suppressed protein synthesis. Although it has been well studied that the IGF-1/PI3K/Akt pathway plays an essential role in the regulation of the protein turnover, molecule(s) that triggers the change in protein turnover still remains to be elucidated. TRB3 has been shown to inhibit Akt through direct binding. In this study, we hypothesized that TRB3 in mouse skeletal muscle negatively regulates protein turnover via the disruption of Akt and its downstream molecules. Muscle-specific TRB3 transgenic (TRB3TG) mice had decreased muscle mass and fiber size, resulting in impaired muscle function. We also found that protein synthesis rate and signaling molecules, mTOR and S6K1, were significantly reduced in TRB3TG mice, whereas the protein breakdown pathway was significantly activated. In contrast, TRB3 knockout mice showed increased muscle mass and had an increase in protein synthesis rate, but decreases in FoxOs, atrogin-1, and MuRF-1. These findings indicate that TRB3 regulates protein synthesis and breakdown via the Akt/mTOR/FoxO pathways.
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Project description:Because of turnover, protein synthesis and breakdown can each be involved in the regulation of the growth of tissue protein. To investigate the regulation of skeletal-muscle-protein growth we measured rates of protein synthesis and breakdown in growing rats during development on a good diet, during development on a marginally low-protein diet and during rehabilitation on a good diet after a period of severe protein deficiency. Rates of protein synthesis were measured in vivo with a constant intravenous infusion of [14C]tyrosine. The growth rate of muscle protein was measured and the rate of breakdown calculated as breakdown rate=synthesis rate-growth rate. These measurements showed that during development on a good diet there was a fall with age in the rate of protein synthesis resulting from a fall in capacity (RNA concentration) and activity (synthesis rate per unit of RNA). There was a fall with age in the breakdown rate so that the rate was highest in the weaning rats, with a half-life of 3 days. There was a direct correlation between the fractional growth and breakdown rates. During rehabilitation on the good diet, rapid growth was also accompanied by high rates of protein breakdown. During growth on the inadequate diet protein synthesis rates were lesss than in controls, but growth occurred because of decreased rates of protein breakdown. This compression was not complete, however, since ultimate muscle size was only one-half that of controls. It is suggested that increased rates of protein breakdown are a necessary accompaniment to muscle growth and may result from the way in which myofibrils proliferate.
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Project description:An equation was derived from which the turnover time of individual muscle proteins could be calculated from measurements made at a single time interval in individual animals after initiation of constant intravenous infusion of labelled amino acid. The calculation requires only the specific radioactivities of the amino acid in plasma, in the intracellular fluid and in the protein under study. Pool sizes were not required. When the equation was applied to adult guinea-pig cardiac myosin, the average turnover time was 16 +/- 1 days.
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Project description:To identify insulin responsive genes in humans, in the first protocol, skeletal muscle biopsies from six non-diabetic subjects were obtained before and after a two-hour of hyperinsulinaemic (infusion rate 40 mU/m2/min) euglycemic clamp. A variable infusion of glucose (180 g/l) enriched with tritiated glucose (100 μCi/500 ml) maintained euglycemia during insulin infusion, with monitoring of plasma glucose concentration every 5 to 10 min during the basal and clamp periods using an automated glucose oxidation method (Glucose Analyzer 2, Beckman Instruments, Fullerton, CA). In the second protocol, skeletal muscle biopsies from six non-diabetic subjects were obtained before and after a 3-hour hyperinsulinemic (infusion rate 40 mU/m2/min) euglycemic clamp in order to increase the effects of insulin on gene expression. A variable infusion of glucose (180 g/l) was used to maintain euglycemia during insulin infusion with monitoring of plasma glucose concentration every 5 to 10 min using an automated glucose oxidation method (Glucose Analyzer 2, Beckman Instruments, Fullerton, CA). Keywords: dose response The muscle biopsies were obtained from the vastus lateralis muscle under local anesthesia before and after hyperinsulinaemic (infusion rate 40 mU/m2/min) euglycemic clamp
2007-03-01 | E-GEOD-7146 | biostudies-arrayexpress
Project description:In the fed state, hyperthyroidism increased glucose utilization indices (GUIs) of skeletal muscles containing a lower proportion of oxidative fibres. Glycogen concentrations were unchanged, but active pyruvate dehydrogenase (PDHa) activities were decreased. Hyperthyroidism attenuated the effects of 48 h of starvation to decrease muscle GUI. Glycogen concentrations and PDHa activities after 48 h of starvation were low and similar in euthyroid and hyperthyroid rats. The increase in glucose uptake and phosphorylation relative to oxidation and storage in skeletal muscle induced by hyperthyroidism may contribute to increased glucose re-cycling in the fed hyperthyroid state and to glucose turnover in the starved hyperthyroid state.
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Project description:To identify insulin responsive genes in humans, in the first protocol, skeletal muscle biopsies from six non-diabetic subjects were obtained before and after a two-hour of hyperinsulinaemic (infusion rate 40 mU/m2/min) euglycemic clamp. A variable infusion of glucose (180 g/l) enriched with tritiated glucose (100 μCi/500 ml) maintained euglycemia during insulin infusion, with monitoring of plasma glucose concentration every 5 to 10 min during the basal and clamp periods using an automated glucose oxidation method (Glucose Analyzer 2, Beckman Instruments, Fullerton, CA). In the second protocol, skeletal muscle biopsies from six non-diabetic subjects were obtained before and after a 3-hour hyperinsulinemic (infusion rate 40 mU/m2/min) euglycemic clamp in order to increase the effects of insulin on gene expression. A variable infusion of glucose (180 g/l) was used to maintain euglycemia during insulin infusion with monitoring of plasma glucose concentration every 5 to 10 min using an automated glucose oxidation method (Glucose Analyzer 2, Beckman Instruments, Fullerton, CA). Keywords: dose response
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