Bcaa Info

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BCAAs prevent protein breakdown, but do not increase protein synthesis.
-Since 1978 a variety of studies have been performed in humans where BCAAs or leucine alone was administrated in varying amounts and durations. An anabolic effect of leucine and the branched-chain amino acids (BCAAs) on reduction of muscle protein breakdown was found in these studies, with no measured effect upon muscle protein synthesis. In addition, no untoward effects have been reported in any of these studies from infusion of the BCAAs at upward 3 times basal flux or 6 times normal dietary intake during the fed portion of the day (B1).
-BCAA infusion in 10 postabsorptive normal subjects causes a 4-fold rise in arterial BCAA levels. Plasma insulin levels were unchanged from basal levels. Whole-body phenylalanine flux, an index of proteolysis, was significantly suppressed by BCAA infusion. Despite the rise in whole-body non-oxidative leucine disposal, and in forearm leucine uptake and disposal, forearm phenylalanine disposal, an index of muscle protein synthesis, was not stimulated by infusion of branched-chain amino acids (B2).
-Short-term (3 to 4 hours) infusion of branched-chain amino acids (BCAA) has been shown to suppress muscle protein breakdown.
An overnight (16-hour) systemic BCAA infusion in 8 subjects increases plasma BCAA concentrations by fivefold to eightfold, and this was associated with a 20% to 60% decline in arterial concentrations of other amino acids.
In the forearm, overnight BCAA infusion resulted in a diminished net release of Phe (-3 +/- 2 v -18 +/- 4 [saline] nmol/min/100 mL, P < .02), and BCAA balance became markedly positive (751 +/- 93 v -75 +/- 30, P < .001) (B4).
-BCAA infusion in 10 postabsorptive normal subjects does not change plasma insulin levels. Skeletal muscle proteolysis was suppressed in the absense of any apparent increase in muscle protein synthesis (B5).
-In humans, infusion of BCAA alone slows skeletal muscle protein degradation, but does not increase protein synthesis. This is perhaps not surprising, as the BCAA also inhibit whole body protein degradation and thereby decrease the arterial concentrations of other essential and nonessential amino acids. This decline may blunt any effect of infused BCAA on protein synthesis by limiting substrate availability and/or interfering with nutrient signaling by other amino acids.
BCAA stimulate the phosphorylation of eIF4E-BP1 and p70S6K involved in activating the mRNA translation apparatus. These results demonstrate that the cellular pathways that regulate translation initiation are, in fact, stimulated by BCAA in humans and suggest a potentially significant anabolic signaling role for BCAA in increasing mRNA translation and protein synthesis. This occurs with increments of circulating BCAA like those seen postprandially, suggesting that this is a normal physiological response.
After a 12 h overnight fast 7 healthy volunteers were adminitered a BCAA infusion for 6 h. Insulin concentrations did not significantly change. BCAA infusion significantly improved forearm phenylalanine balance in control subjects at 6 h (Fig. 4A), although, as we previously reported, it did not increase phenylalanine Rd (B6).
-BCAAs during 1h cycle exercise and a 2h recovery period does not influence the rate of exchange of the aromatic AAs during exercise. In the recovery period, a faster decrease in the muscle concentration of aromatic AAs was found (46% compared with 25% in the placebo condition). There was also a tendency to a smaller release (an average of 32%) of these amino acids from the legs. The results suggest that BCAA have a protein-sparing effect during the recovery after exercise (E5)
-7.5-12 g BCAAs during intense exercise (a 30 km cross-country race and a full marathon) increases BCAA plasma and muscle concentration. In the placebo group plasma BCAA decreased and left muscle levels unchanged. The placebo group showed a 20-40% increase in the muscle concentration of aromatic AAs. BCAA supplementation prevented this increase in aromatic AAs in both muscle and plasma. These results suggest that an intake of BCAAs during exercise can prevent or decrease the net rate of protein degradation caused by heavy exercise (E8).
-Consumption of BCAA (30 to 35% leucine) before or during endurance exercise may prevent or decrease the net rate of protein degradation, may improve both mental and physical performance and may have a sparing effect on muscle glycogen degradation and depletion of muscle glycogen stores (E14).
-77 mg BCAAs/kg supplementation before exercise resulted in a doubling (P < 0.05) of the arterial BCAA levels before exercise (339 +/- 15 vs. 822 +/- 86 microM). During the 60 min of exercise, the total release of BCAA was 68 +/- 93 vs. 816 +/- 198 mumol/kg (P < 0.05) for the BCAA and control trials, respectively. Furthermore, the increased intramuscular and arterial BCAA levels before and during exercise result in a suppression of endogenous muscle protein breakdown during exercise.(E105).
-BCAA activate mRNA translation initiation, but without the anticipated increase in protein synthesis. One possible explanation for this apparent discrepancy is that BCAA inhibit proteolysis and thereby decrease the arterial concentrations of other AA (P4).