The formation of alanine from amino acids in diaphragm muscle of the rat.
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ABSTRACT:
SUBMITTER: Goldstein L
PROVIDER: S-EPMC1172735 | biostudies-other | 1976 Feb
REPOSITORIES: biostudies-other
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Project description:Dichloroacetate (which activates pyruvate dehydrogenase) decreases the release of alanine, pyruvate and lactate in hemidiaphragm incubations with valine. Dichloroacetate interferes with alanine formation by diverting pyruvate into oxidative pathways, which not only limits pyruvate availability for direct transamination to form alanine but also indirectly affects branched-chain amino acid transamination by limiting 2-oxoglutarate regeneration from glutamate.
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Project description:Alanine release by rat diaphragm muscle in vitro is stimulated by glutamate, valine, leucine and glucose. The stimulation by glutamate and valine (but not leucine) is inhibited by 3-mercaptopicolinate. These results suggest a metabolic route involving phosphoenolpyruvate carboxykinase which directs amino acid carbon skeletons towards pyruvate synthesis for alanine formation.
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Project description:Eccentric exercise results in prolonged muscle damage that may lead to muscle dysfunction. Although inflammation is essential to recover from muscle damage, excessive inflammation may also induce secondary damage, and should thus be suppressed. In this study, we investigated the effect of leucine-enriched essential amino acids on muscle inflammation and recovery after eccentric contraction. These amino acids are known to stimulate muscle protein synthesis via mammalian target of rapamycin (mTOR), which, is also considered to alleviate inflammation. Five sets of 10 eccentric contractions were induced by electrical stimulation in the tibialis anterior muscle of male SpragueDawley rats (8-9 weeks old) under anesthesia. Animals received a 1 g/kg dose of a mixture containing 40 % leucine and 60 % other essential amino acids or distilled water once a day throughout the experiment. Muscle dysfunction was assessed based on isometric dorsiflexion torque, while inflammation was evaluated by histochemistry. Gene expression of inflammatory cytokines and myogenic regulatory factors was also measured. We found that leucine-enriched essential amino acids restored full muscle function within 14 days, at which point rats treated with distilled water had not fully recovered. Indeed, muscle function was stronger 3 days after eccentric contraction in rats treated with amino acids than in those treated with distilled water. The amino acid mix also alleviated expression of interleukin-6 and impeded infiltration of inflammatory cells into muscle, but did not suppress expression of myogenic regulatory factors. These results suggest that leucine-enriched amino acids accelerate recovery from muscle damage by preventing excessive inflammation.
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Project description:Hepatic gluconeogenesis from amino acids contributes significantly to diabetic hyperglycemia, but the molecular mechanisms involved are incompletely understood. Alanine transaminases (ALT1 and ALT2) catalyze the interconversion of alanine and pyruvate, which is required for gluconeogenesis from alanine. Hepatocyte-specific knockout of Gpt2 attenuated incorporation of 13C-alanine into newly synthesized glucose by hepatocytes. However, Gpt2 knockout in liver had no effect on glucose concentrations in lean mice, which may suggest that metabolic compensation is occurring.
2022-04-06 | GSE199975 | GEO
Project description:BACKGROUND:A previous clinical study reported that the addition of an amylopectin/chromium complex (ACr; Velositol®) to 6?g of whey protein (WP) significantly enhanced muscle protein synthesis (MPS). Branched-chain amino acids (BCAAs) are also well-known to enhance MPS. The aim of this study was to determine if the addition of ACr to BCAAs can enhance MPS and activate expression of the mammalian target of the rapamycin (mTOR) pathway compared to BCAAs and exercise alone in exercise-trained rats. METHODS:Twenty-four male Wistar rats were randomly divided into three groups (n?=?8 per group): (I) Exercise control, (II) Exercise plus BCAAs (0.465?g/kg BW, a 6?g human equivalent dose (HED)), and (III) Exercise plus BCAAs (0.465?g/kg BW) and ACr (0.155?g/kg BW, a 2?g HED). All animals were trained with treadmill exercise for 10?days. On the day of the single-dose experiment, rats were exercised at 26?m/min for 2?h and then fed, via oral gavage, study product. One hour after the consumption of study product, rats were injected with a bolus dose (250?mg/kg BW, 25?g/L) of phenylalanine labeled with deuterium to measure the fractional rate of protein synthesis (FSR). Ten minutes later, muscle tissue samples were taken to determine MPS measured by FSR and the phosphorylation of proteins involved in the mTOR pathway including mTOR, S6K1, and 4E-BP1. RESULTS:ACr combined with BCAAs increased MPS by 71% compared to the exercise control group, while BCAAs alone increased MPS by 57% over control (p?<?0.05). ACr plus BCAAs significantly enhanced phosphorylation of mTOR, S6K1 and 4E-BP1 compared to exercise control rats (p?<?0.05). The addition of ACr to BCAAs enhanced insulin levels, mTOR and S6K1 phosphorylation compared to BCAAs alone (p?<?0.05). Serum insulin concentration was positively correlated with the levels of mTOR, (r?=?0.923), S6K1 (r?=?0.814) and 4E-BP1 (r?=?0.953). CONCLUSIONS:In conclusion, the results of this study provide evidence that the addition of ACr to BCAAs significantly enhances exercise-induced MPS, and the phosphorylation of mTOR signaling proteins, compared to BCAAs and exercise alone.
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Project description:Introduction: Functional tests and training regimens intensity-controlled by an individual are used in sport practice, clinical rehabilitation, and space medicine. The model of voluntary wheel running in rats can be used to explore molecular mechanisms of such training regimens in humans. Respiratory and locomotor muscles demonstrate diverse adaptations to treadmill exercise, but the effects of voluntary exercise training on these muscle types have not been compared yet. Therefore, this work aimed at the effects of voluntary ET on rat triceps brachii and diaphragm muscles with special attention to reactive oxygen species, which regulate muscle plasticity during exercise. Methods: Male Wistar rats were distributed into exercise trained (ET) and sedentary (Sed) groups. ET group had free access to running wheels, running activity was continuously recorded and analyzed using the original hardware/software complex. After 8 weeks, muscle protein contents were studied using Western blotting. Results: ET rats had increased heart ventricular weights but decreased visceral/epididymal fat weights and blood triglyceride level compared to Sed. The training did not change corticosterone, testosterone, and thyroid hormone levels, but decreased TBARS content in the blood. ET rats demonstrated higher contents of OXPHOS complexes in the triceps brachii muscle, but not in the diaphragm. The content of SOD2 increased, and the contents of NOX2 and SOD3 decreased in the triceps brachii muscle of ET rats, while there were no such changes in the diaphragm. Conclusion: Voluntary wheel running in rats is intensive enough to govern specific adaptations of muscle fibers in locomotor, but not respiratory muscle.
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Project description:The diaphragm is the most important inspiratory muscle in all mammals, and ventilatory insufficiency caused by diaphragm dysfunction is the leading cause of morbidity and mortality in many genetic and acquired diseases affecting skeletal muscle. Currently, pharmacological inhibitors, genetically modified animals, and invasive procedures are used to study disorders affecting the diaphragm. However, these methodologies can be problematic because of off-target drug effects and the possible nonphysiological consequences of lifelong genetic alterations. Therefore, alternative methods to study this important respiratory muscle are needed. To resolve this, we have developed a methodology to deliver recombinant adeno-associated virus (rAAV) vectors to the rat diaphragm via direct intramuscular injection. We hypothesized that by direct injection of rAAV into the muscle we can selectively target the diaphragm and establish a novel experimental method for studying signaling pathways and also provide a strategy for effectively using rAAV to protect the diaphragm against disease. This report describes the methods and evidence to support the use of rAAV as a therapeutic intervention to study rat diaphragm biology during conditions that promote diaphragm dysfunction.
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