Spiergroei door aminozuren is onafhankelijk van IGF-1 en insuline

[Big'r]

Aminozuren geven een onafhankelijke en directe trigger voor proteine synthese:

Effects of amino acids on synthesis and degradation of skeletal muscle proteins in humans.

Synthesis and degradation of globular and myofibrillar proteins across arm and leg muscles were examined during stepwise increased intravenous infusion of amino acids (0.1, 0.2, 0.4, and 0.8 g N.kg-1.day-1) to healthy volunteers. Protein dynamics were measured by a primed constant infusion of L-[ring-2H5]phenylalanine and the release of 3-methylhistidine from skeletal muscles. Arterial concentrations and flux of glucose, lactate, and free fatty acids were unchanged despite increasing concentrations of plasma amino acids from 2.6 to 5.7 mM. Plasma insulin, insulin-like growth factor I (IGF-I), and plasma concentrations of IGF-I-binding proteins-1 and -3 remained at fasting levels throughout the investigation. Amino acid infusion caused a significant uptake of the majority of amino acids across arm and leg tissues, except tyrosine, tryptophan, and cysteine, probably due to low concentrations of these amino acids in the formulation. The balance of globular proteins improved significantly (P < 0.01) due to stimulation of synthesis and attenuation of degradation across arm and leg tissues, despite insignificant uptake of tyrosine, tryptophan, and cysteine. Degradation of myofibrillar proteins was uninfluenced by provision of amino acids. The results demonstrate that neither insulin nor circulating IGF-I explained improved protein balance in skeletal muscles after elevation of plasma amino acids. Rather, some amino acids in themselves trigger cellular reactions that initiate peptide formation. Limited availability of some extracellular amino acids was overcome by increased reutilization of the intracellular amino acid.

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Alleen maar weer een bevestiging (dit keer via verklaring van het onderliggende mechanisme voor activering van eiwitsynthese) dat aminozuren bij de training belangrijker zijn dan suikers.

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[Big-T]

Hoewel dit niet uitsluit dat de pre-training combinatie aminozuren en bijv. maltodextrine voor een surplus bij de opname en synthese zorgt. Interessant onderzoek dat duidelijk het belang van beschikbare essentiële aminozuren tijdens training aantoont.

 

[Gouwetonny]

Alleen maar weer een bevestiging (dit keer via verklaring van het onderliggende mechanisme voor activering van eiwitsynthese) dat aminozuren bij de training belangrijker zijn dan suikers.

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Waar staat dat?

 

[BBD]

Maar zegt dit niet dat insuline wel degelijk invloed heeft?

Am J Physiol Endocrinol Metab. 2006 Jan 17;

The insulin-facilitated increase of muscle protein synthesis after resistance exercise involves a MAP-kinase pathway.

Fluckey JD, Knox M, Smith LM, Dupont-Versteegden EE, Gaddy D, Tesch PA, Peterson CA.

Department of Health and Kinseiology, Texas A&M University, College Station, TX, USA.

Recent studies have implicated the mTOR signaling pathway as a primary component for muscle growth in mammals. The purpose of this investigation was to examine signaling pathways for muscle protein synthesis after resistance exercise. Sprague-Dawley rats (male, 6 months old) were assigned to either resistance exercise or control groups. Resistance exercise was accomplished in operantly conditioned animals using a specially designed flywheel apparatus. Rats performed two sessions of resistance exercise, separated by 48 h, each consisting of 2 sets of 25 repetitions. Sixteen hours after the second session, animals were sacrificed, and soleus muscles were examined for rates of protein synthesis with and without insulin and/or rapamycin (mTOR inhibitor) and/or (PD)098059 (MEK-kinase inhibitor). Results of this study demonstrated that rates of synthesis were higher (p<0.05) with insulin after exercise in comparison to without insulin, or to control muscles, regardless of insulin. Rapamycin lowered (p<0.05) rates of synthesis in controls, with or without insulin, and after exercise without insulin. However, insulin was able to overcome the inhibition of rapamycin after exercise (p<0.05). PD had no effect on protein synthesis in control rats, but the addition of PD to exercised muscle resulted in lower (p<0.05) rates of synthesis, and this inhibition was not rescued by insulin. Western blot analyses demonstrated that the inhibitors used in the present study were selective and effective for preventing activation of specific signaling proteins. Together, these results suggest that the insulin-facilitated increase of muscle protein synthesis after resistance exercise requires multiple signaling pathways.

 

[Big-T]

Zijn genoeg studies die dat aantonen, gaat er in deze studie over dat bepaalde aminozuren geen insuline nodig hebben om te synthetiseren. Er wordt nergens gezegd dat insuline geen invloed heeft.

 

[BBD]

Ow ok. Dan ben ik het eens met jou conclusie dat insuline wel voor een betere opname van amino's kan zorgen en dus toch wenselijk is.