Promotion Of Protein Synthesis Research Articles

Alpha-linolenic acid/linoleic acid ratio can effectively promote muscle growth and protein deposition in grass carp (Ctenopharyngodon idella)

Polyunsaturated fatty acids (PUFAs) promoted the muscle structure (muscle fiber cross-sectional area and diameter, as well as thickness of the connective tissue surrounding muscle fibers-endomysium) and taste (fishy) of fillets. As members of the omega-3 and omega-6 PUFA family, alpha-linolenic acid (ALA) and linoleic acid (LNA) have important functions. This study explores influences of ALA/LNA ratio on muscle growth and protein deposition and its mechanisms. Six different diets containing ALA/LNA ratios (0.03, 0.47, 0.92, 1.33, 1.69, and 2.15) were fed to grass carp (Ctenopharyngodon idella) for 9 weeks. Results showed that according to the quadratic regression model, the optimal ALA/LNA ratios of grass carp were 1.12 and 1.22 using malondialdehyde content and muscle fiber diameter as indicators, respectively. Optimum ALA/LNA ratio promoted hypertrophy of myofibers, which might be attributed to genes related to myofiber development (myogenic determinant, myogenin, myosin heavy chain, myogenic regulatory factor 4 and myogenic factor 5). Optimum ALA/LNA ratio enhanced protein deposition, which might be associated with the promotion of protein synthesis (insulin-like growth factors-1, phosphoinositide 3-kinase, target of rapamycin), and inhibition of the ubiquitin-proteasome system and autophagy-lysosome system to inhibit protein degradation. In addition, optimum ALA/LNA ratio enhanced muscle amino acid composition and antioxidant capacity of fish.

Bckdk-Mediated Branch Chain Amino Acid Metabolism Reprogramming Contributes to Muscle Atrophy during Cancer Cachexia.

Branched chain amino acids (BCAAs) are essential amino acids and important nutrient signals for energy and protein supplementation. The study uses muscle-specific branched-chain α-keto acid dehydrogenase kinase (Bckdk) conditional knockout (cKO) mice to reveal the contribution of BCAA metabolic dysfunction to muscle wasting. Muscle-specific Bckdk-cKO mice are generated through crossbreeding of Bckdkf/f mice with Myf5Cre mice. Lewis lung cancer (LLC) tumor transplantation is used to establish the cancer cachexia model. The occurrence of cancer cachexia is accelerated in the muscle-specific Bckdk-cKO mice after bearing LLC tumor. Wasting skeletal muscle is characterized by increased protein ubiquitination degradation and impaired protein synthesis. The wasting muscle gastrocnemius is mechanized as a distinct BCAA metabolic dysfunction. Based on the atrophy phenotype resulting from BCAA metabolism dysfunction, the optimized BCAA supplementation improves the survival of cancer cachexia in muscle-specific Bckdk-cKO mice bearing LLC tumors, and improves the occurrence of cancer cachexia. The mechanism of BCAA supplementation on muscle mass preservation is based on the promotion of protein synthesis and the inhibition of protein ubiquitination degradation. Dysfunctional BCAA metabolism contributes to the inhibition of protein synthesis and increases protein degradation in the cancer cachexia model of muscle-specific Bckdk-cKO mice bearing LLC tumors. The reprogramming of BCAA catabolism exerts therapeutic effects by stimulating protein synthesis and inhibiting protein degradation in skeletal muscle.

Exploring the Therapeutic Potential of Ethyl 3-Hydroxybutyrate in Alleviating Skeletal Muscle Wasting in Cancer Cachexia.

Cachexia (CAC) is a debilitating metabolic syndrome. Although dietary interventions are attractive, long-term adherence to specific diets is difficult to maintain and can lead to systemic side effects. Ethyl 3-hydroxybutyrate (EHB) is a commonly used food additive found in wine and Tribolium castaneum. In this study, we investigated the effects of EHB administration in cachectic mice. After a single intraperitoneal injection of EHB into mice, 3-hydroxybutyrate (3-HB) levels were significantly increased in the serum and gastrocnemius of mice. The administration of EHB alleviated cachexia-related symptoms, ameliorated skeletal muscle atrophy, and improved survival in cachectic mice. In addition, the supplementation of cachectic mice with 3-HB by EHB administration significantly reduced tumor weights, indicating the anti-tumor effects of 3-HB. Remarkably, the addition of 3-HB to the culture medium significantly attenuated the C2C12 myotube atrophy induced by the culture supernatant of CT26 cell lines, highlighting its potential to counteract the destructive effects of tumor-derived elements on muscle tissue. NMR-based metabolomics analysis provided insights into the underlying mechanisms and revealed that the anti-cachexia effects of 3-HB treatment can be attributed to three key mechanisms: the promotion of the TCA cycle and the attenuation of proteolysis, the promotion of protein synthesis and the improvement of metabolic homeostasis, and a reduction in inflammation and an enhancement of the antioxidant capacity. This study provided compelling evidence for the protective effects of 3-HB treatment on the cachectic gastrocnemius and highlighted the efficacy of EHB administration as a ketone supplementation approach to achieve nutritional ketosis without the need for dietary restriction.

Administration of tauroursodeoxycholic acid attenuates dexamethasone-induced skeletal muscle atrophy

Glucocorticoids are known to induce skeletal muscle atrophy by suppressing protein synthesis and promoting protein degradation. Tauroursodeoxycholic acid (TUDCA) has beneficial effects in several diseases, such as hepatobiliary disorders, hindlimb ischemia and glucocorticoid-induced osteoporosis. However, the effects of TUDCA on glucocorticoid -induced skeletal muscle atrophy remains unknown. Therefore, in the present research, we explored the effects of TUDCA on dexamethasone (DEX)-induced loss and the potential mechanisms involved. We found TUDCA alleviated DEX-induced muscle wasting in C2C12 myotubes, identified by improved myotube differentiation index and expression of myogenin and MHC. And it showed that TUDCA activated the Akt/mTOR/S6K signaling pathway and inhibited FoxO3a transcriptional activity to decreased expression of MuRF1 and Atrogin-1, while blocking Akt by MK2206 blocked these effects of TUDCA on myotubes. Besides, TUDCA also attenuated DEX-induced apoptosis of myotubes. Furthermore, TUDCA was administrated to the mouse model of DEX-induced skeletal muscle atrophy. The results showed that TUDCA improved DEX-induced skeletal muscle atrophy and weakness (identified by increased grip strength and prolonged running exhaustive time) in mice by suppression of apoptosis, reduction of protein degradation and promotion of protein synthesis. Taken together, our research proved for the first time that TUDCA protected against DEX-induced skeletal muscle atrophy not only by improving myogenic differentiation and protein synthesis, but also through decreasing protein degradation and apoptosis of skeletal muscle.

PGC-1α and PGC-1β Increase Protein Synthesis via ERRα in C2C12 Myotubes.

The transcriptional coactivators peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) and PGC-1β are positive regulators of skeletal muscle mass and energy metabolism; however, whether they influence muscle growth and metabolic adaptations via increased protein synthesis is not clear. This study revealed PGC-1α or PGC-1β overexpression in C2C12 myotubes increased protein synthesis and myotube diameter under basal conditions and attenuated the loss in protein synthesis following the treatment with the catabolic agent, dexamethasone. To investigate whether PGC-1α or PGC-1β signal through the Akt/mTOR pathway to increase protein synthesis, treatment with the PI3K and mTOR inhibitors, LY294002 and rapamycin, respectively, was undertaken but found unable to block PGC-1α or PGC-1β’s promotion of protein synthesis. Furthermore, PGC-1α and PGC-1β decreased phosphorylation of Akt and the Akt/mTOR substrate, p70S6K. In contrast to Akt/mTOR inhibition, the suppression of ERRα, a major effector of PGC-1α and PGC-1β activity, attenuated the increase in protein synthesis and myotube diameter in the presence of PGC-1α or PGC-1β overexpression. To characterize further the biological processes occurring, gene set enrichment analysis of genes commonly regulated by both PGC-1α and PGC-1β was performed following a microarray screen. Genes were found enriched in metabolic and mitochondrial oxidative processes, in addition to protein translation and muscle development categories. This suggests concurrent responses involving both increased metabolism and myotube protein synthesis. Finally, based on their known function or unbiased identification through statistical selection, two sets of genes were investigated in a human exercise model of stimulated protein synthesis to characterize further the genes influenced by PGC-1α and PGC-1β during physiological adaptive changes in skeletal muscle.

Metabolomics analysis of Tripterygium wilfordii formulation based on theory of detoxicity compatibility

Tripterygium wilfordii Hook. f. induced-hepatotoxicity was the main limitation for its usage in clinic. Qingluo Tongbi formulation showed obvious attenuation for hepatotoxicity in clinic and fundamental research in vivo. To explore the potential mechanism of the attenuation, we conducted a study on the plasma metabolomic profiles of T. wilfordii and Qingluo Tongbi formulation in rats by a sensitive gas chromatography-mass spectrometry (GC-MS/MS) method. In plasma samples, a total of 72 compounds were analyzed by EI source MS, and were successfully identified by matching NIST database. The semi-quantification results were then calculated by OPLS-DA model with SIMCA-P 13.0 software. The three groups were clearly distinguished in OPLS-DA score plot. In addition, the observation values of Qingluo Tongbi formulation showed the obvious trend towards the control levels, suggesting the detoxicity effect of the formulation. Variation metabolites were further analyzed by VIP and One Way ANOVAs, and the results showed a significant increase in compounds of glycogenic amino acids, such as alanine, proline, serine and glutamine after the administration of T. wilfordii, indicated that the tissue proteins were decomposed and amino acids were leakage into blood. Qingluo Tongbi formulation could reverse the amino acids into normal level. On the contrary, the levels of glucose, lactic acid and hydroxy butyrate decrease, and the formulation can relieve the disorder in the levels of lactic acid, suggesting the regulation of the energy metabolism. Additionally, the level of branched chain amino acid was decreased, suggested the toxicity was induced, but the formulation cannot increase it into the normal levels. Nevertheless, all the above results suggested that the classical Qingluo Tongbi formulation displayed the liver protection effect by adjusting the amino acid levels and regulating the energy metabolism. Qingluo Tongbi formulation was developed based on traditional Chinese medicine theory "detoxicity compatibility", and contained Panax notoginseng (Burk.) F. H. Chen to nourish blood and absorb clots. Modern pharmacology suggested that its liver protection effect was correlated with the promotion of protein synthesis. Another important herb is Rehmannia glutinosa Libosch., which can regulate the energy metabolism. Both were consistent with the metabolomic results in this study, which explained the potential mechanism of "detoxicity compatibility" theory. Therefore, the currently developed metabolomic approach and the obtained results would be highly useful for the comprehensive toxicity studies for other herbal medicines and various complex deoxicity formulations.

Effects Of Potassium, Phosphorus And Nitrogen Fertilization On Endogenous Ethylene And Quality Characteristics Of Apples (Malus Domestica L.)

Factor analysis of the data from experiment one with fertilization of ‘Spartan’ apples using various levels of nitrogen, phosphorus, and potassium and their interactions showed significances between ethylene and potassium, soluble solids and potassium, acidity and phosphorus, ethylene and phosphorus, and between ethylene and nitrogen. Factor analysis of data from experiment two with twenty apple cultivars showed that maturation time and ethylene were positively associated, whereas ethylene was inversely related to acidity that is reduced during the apple fruit maturation, and soluble solids are produced during apple fruit maturation. The effects of potassium on ethylene could be through promotion of enzyme activation, promotion of protein synthesis and increased solute transport in the xylem and phloem. Production of ethylene through soluble solids could be due to increased synthesis of the amino acid cysteine that is precursor of ethylene that may be extended to synthesis of other amino acids. The decreasing concentration of malic acid during fruit maturation may be due to increasing rates of several enzymes involved in the citric acid and glyoxylate cycles that are delivering precursors to synthesis of amino acids and porphyrins. The significant relationships between soluble solids and potassium and between acidity and phosphorus may increase the synthesis of nucleic acids and improve energy supply through adenosine phosphates. The significance between ethylene and nitrogen may also increase synthesis of amino acids, proteins and enzymes. On this basis it may be concluded that the three major minerals nitrogen, phosphorus and potassium are very important for apple fruit maturation because they may be involved in several biochemical processes.

Characterization of the Raptor/4E-BP1 Interaction by Chemical Cross-linking Coupled with Mass Spectrometry Analysis

mTORC1 plays critical roles in the regulation of protein synthesis, growth, and proliferation in response to nutrients, growth factors, and energy conditions. One of the substrates of mTORC1 is 4E-BP1, whose phosphorylation by mTORC1 reverses its inhibitory action on eIF4E, resulting in the promotion of protein synthesis. Raptor in mTOR complex 1 is believed to recruit 4E-BP1, facilitating phosphorylation of 4E-BP1 by the kinase mTOR. We applied chemical cross-linking coupled with mass spectrometry analysis to gain insight into interactions between mTORC1 and 4E-BP1. Using the cross-linking reagent bis[sulfosuccinimidyl] suberate, we showed that Raptor can be cross-linked with 4E-BP1. Mass spectrometric analysis of cross-linked Raptor-4E-BP1 led to the identification of several cross-linked peptide pairs. Compilation of these peptides revealed that the most N-terminal Raptor N-terminal conserved domain (in particular residues from 89 to 180) of Raptor is the major site of interaction with 4E-BP1. On 4E-BP1, we found that cross-links with Raptor were clustered in the central region (amino acid residues 56-72) we call RCR (Raptor cross-linking region). Intramolecular cross-links of Raptor suggest the presence of two structured regions of Raptor: one in the N-terminal region and the other in the C-terminal region. In support of the idea that the Raptor N-terminal conserved domain and the 4E-BP1 central region are closely located, we found that peptides that encompass the RCR of 4E-BP1 inhibit cross-linking and interaction of 4E-BP1 with Raptor. Furthermore, mutations of residues in the RCR decrease the ability of 4E-BP1 to serve as a substrate for mTORC1 in vitro and in vivo.

Autoradiographic analysis of the effect of cytokinin on protein and RNA syntheses in the Ceratodon purpureus protonema

In the protonema of <em>Ceratodon purpureus</em> (Hedw.) Brid., apical parts of the protonemal filaments (apical cells, initials of protonemal side branches and of gametophore buds) proved to be preferential sites of [<sup>14</sup>C]-leucine incorporation into proteins. In some filaments, a similar preference for [<sup>3</sup>H]-uridine incorporation into RNA was observed, whereas in others there was a rather uniform distribution of label over all cells. A short (0.5-2 h) treatment with cytokinin (N<sup>6</sup>-2-isopentenyladenine) enhanced [<sup>14</sup>C]-leucine incorporation, without changing the relative distribution of label. No such enhancement, as well as no change in label distribution could be observed in [<sup>3</sup>H]-uridine incorporation. No direct relationship seems to exist between the early promotion of protein synthesis by cytokinin in the protonema and cytokinin induction of gametophore buds.

A multiple functional protein: the herpes simplex virus type 1 tegument protein VP22

The herpes simplex virus type 1 (HSV-1) VP22, is one of the most abundant HSV-1 tegument proteins with an average stoichiometry of 2 400 copies per virion and conserved among alphaherpesvirinae. Many functions are attributed to VP22, including nuclear localization, chromatin binding, microtubule binding, induction of microtubule reorganization, intercellular transport, interaction with cellular proteins, such as template activating factor I (TAF-I) and nonmuscle myosin II A (NMIIA), and viral proteins including tegument protein VP16, pUS9 and pUL46, glycoprotein E (gE) and gD. Recently, many novel functions performed by the HSV-1 VP22 protein have been shown, including promotion of protein synthesis at late times in infection, accumulation of a subset of viral mRNAs at early times in infection and possible transcriptional regulation function.

Glucose Regulates EF-2 Phosphorylation and Protein Translation by a Protein Phosphatase-2A-dependent Mechanism in INS-1-derived 832/13 Cells

The role of elongation factor (EF)-2 phosphorylation in the regulation of pancreatic beta-cell protein synthesis by glucose was investigated in the INS-1-derived cell line 832/13. Incubation of cells in media containing 1 mm glucose resulted in a progressive increase in EF-2 phosphorylation that was maximal by 1-2 h. Readdition of 10 mm glucose promoted a rapid dephosphorylation of EF-2 that was complete in 10 min and maintained over the ensuing 2 h. Similar results were obtained using primary rat islets or Min-6 insulinoma cells. The glucose effect in 832/13 cells was replicated by addition of pyruvate or alpha-ketocaproate, but not 2-deoxyglucose, suggesting that mitochondrial metabolism was required. Accordingly, glucose-mediated dephosphorylation of EF-2 was completely blocked by the mitochondrial respiratory antagonists antimycin A and oligomycin. The hyperglycemic effect was not mimicked by incubation of cells in 100 nm insulin, 30 mm potassium chloride, or 0.25 mm diazoxide, indicating that insulin secretion and/or depolarization of beta cells was not required. The locus of the high glucose effect appeared to be protein phosphatase-2A, the principal phosphatase acting on EF-2. Protein phosphatase-2A activity was stimulated by glucose addition to 832/13 cells, but neither protein phosphatase-1 nor calmodulin kinase III (EF-2 kinase) activity was affected under these conditions. The slower rephosphorylation of EF-2 during the transition from high to low glucose may involve effects on EF-2 kinase activity. Addition of 5-aminoimidazole-4-carboxamide 1-beta-d-ribofuranoside in high glucose led to a marked stimulation of EF-2 phosphorylation, consistent with the possibility that increased AMP kinase activity in low glucose stimulates EF-2 kinase. In parallel with the effects on EF-2 dephosphorylation, addition of high glucose to 832/13 cells markedly increased the incorporation of [(35)S]methionine into total protein. Taken together, these results suggest that modulation of extracellular glucose impacts protein translation rate in beta cells at least in part through regulation of the elongation step, via phosphorylation/dephosphorylation of EF-2.