Effect of Branched Chain Amino Effect of Branched Chain Amino Acids (BCAA) on Prolonged Acids (BCAA) on Prolonged

Physical ActivityPhysical Activity

BCAABCAABranched chain amino acids (leucine, isoleucine, and Branched chain amino acids (leucine, isoleucine, and valine), or BCAA's, are a group of essential amino valine), or BCAA's, are a group of essential amino acids that play important roles in protein synthesis and acids that play important roles in protein synthesis and energy production. energy production. In humans, about 15-25% of total protein intake is In humans, about 15-25% of total protein intake is BCAA's, and dairy products are particularly high in BCAA's, and dairy products are particularly high in them them BCAA's make up 35-40% of the essential amino acids BCAA's make up 35-40% of the essential amino acids in body protein and 14% of the total amino acids in in body protein and 14% of the total amino acids in skeletal muscle skeletal muscle One of the most important BCAA's is leucine, and One of the most important BCAA's is leucine, and estimates of dietary requirements for leucine range estimates of dietary requirements for leucine range from 1-12 g dailyfrom 1-12 g daily

Amino acidAmino acid

The use of supplemental BCAA's has been The use of supplemental BCAA's has been researched for a variety of purposesresearched for a variety of purposes– in the treatment of liver failurein the treatment of liver failure– catabolic disease states catabolic disease states – improve exercise performance improve exercise performance

a significant a significant decrease in plasma leucine levelsdecrease in plasma leucine levels after aerobic, anaerobic, and strength after aerobic, anaerobic, and strength exercise .This is exercise .This is due to increased BCAA due to increased BCAA metabolism in muscle tissuemetabolism in muscle tissue. .

BCAA and ExerciseBCAA and Exercise

Supplementation with leucine or BCAA's in Supplementation with leucine or BCAA's in both the short and long term prevents the both the short and long term prevents the exercise-induced decline in plasma BCAA's exercise-induced decline in plasma BCAA's and increases muscle BCAA concentrationand increases muscle BCAA concentration

BCAA's may spare muscle and liver glycogen BCAA's may spare muscle and liver glycogen stores and increase fuel supply stores and increase fuel supply

Muscle content of glycogen in biopsy samples taken at rest, during exercise, and in the recovery after exercise in the normal (A)- and low (B)-glycogen legs in the 2 conditions. ○, Branched-chain amino acid (BCAA) condition; ●, placebo condition. Values are means ± SE for 7 subjects

The BCAA's are the The BCAA's are the only amino acids that are only amino acids that are not readily degraded in the livernot readily degraded in the liver

Leucine & protein synthesisLeucine & protein synthesis

In skeletal muscle, In skeletal muscle, leucine stimulates protein leucine stimulates protein synthesissynthesis through multiple independent through multiple independent mechanisms. The mechanisms. The first mechanism is first mechanism is increased insulin secretionincreased insulin secretion

leucine stimulates protein synthesis through leucine stimulates protein synthesis through the mammalian target of rapamycin (mTOR)* the mammalian target of rapamycin (mTOR)* pathways, 70-kDa ribosomal protein S6 kinase pathways, 70-kDa ribosomal protein S6 kinase activity.activity.

* * mTOR is a serine/threonine mTOR is a serine/threonine protein kinaseprotein kinase that that regulates cell growth, cell regulates cell growth, cell proliferation, cell motility, cell survival, protein synthesis, and transcriptionproliferation, cell motility, cell survival, protein synthesis, and transcription ..

70-kDa S6 protein kinase (p70S6k) phosphorylation at Ser424/Thr421 in skeletal muscle at rest and after exercise during placebo and BCAA trials. Representative immunoblots are shown (top). Values in graph are arbitrary units (means ± SE for 7 subjects). #P < 0.05 vs. rest; *P < 0.05 for BCAA vs. placebo

leucine also leucine also enhances eIf4E-binding protein enhances eIf4E-binding protein phosphorylationphosphorylation and the association of and the association of eukaryotic initiation factor (eIF)4E* with eukaryotic initiation factor (eIF)4E* with eIF4G, effects that have been determined both eIF4G, effects that have been determined both in vitro and in vivo in humans in vitro and in vivo in humans

*proteins involved in the initiation phase of eukaryotic translation*proteins involved in the initiation phase of eukaryotic translation. . eIF4E eIF4E recognizes and binds to the 5' cap structure of mRNA, while eIF4G binds recognizes and binds to the 5' cap structure of mRNA, while eIF4G binds to Poly(A)-binding protein which binds the poly(A) tail, circularizing and to Poly(A)-binding protein which binds the poly(A) tail, circularizing and activating the bound mRNAactivating the bound mRNA

An additional mechanism for improved An additional mechanism for improved exercise performance from exercise performance from BCAA's is BCAA's is inhibition of CNS fatigueinhibition of CNS fatigue. .

BCAA's share the BCAA's share the same transporter system same transporter system with tryptophanwith tryptophan (the serotonin precursor (the serotonin precursor amino acid), so BCAA supplementation causes amino acid), so BCAA supplementation causes competitive inhibition of tryptophan transport competitive inhibition of tryptophan transport to the brainto the brain, and this in turn reduces serotonin , and this in turn reduces serotonin levels. levels.

Exercise increases the tryptophan/BCAA Exercise increases the tryptophan/BCAA ratioratio in the bloodstream, and a in the bloodstream, and a BCAA BCAA supplement may prevent or reverse thissupplement may prevent or reverse this. .

Further, animal studies find that tryptophan Further, animal studies find that tryptophan administration reduces exercise performanceadministration reduces exercise performance

This means that in theory, This means that in theory, BCAA's could BCAA's could increase exercise performance by decreasing increase exercise performance by decreasing buildup of serotonin in the brainbuildup of serotonin in the brain. Multiple . Multiple studies indicate that BCAA supplements studies indicate that BCAA supplements successfully change the tryptophan/BCAA successfully change the tryptophan/BCAA plasma ratio, especially during more plasma ratio, especially during more prolonged exerciseprolonged exercise

Muscle concentration of tyrosine (A and B) and phenylalanine (C and D) in biopsy samples taken at rest, after exercise, and in recovery after exercise in the normal (A and C)- and low (B and D)-glycogen legs in the 2 conditions.  , BCAA condition;  , placebo condition. Values are means ± SE for 7 subjects. *P < 0.05 for BCAA vs. placebo.

F-tryp/BCAA and Central FatigueF-tryp/BCAA and Central Fatigue

Low levels of BCAA in conjunction with high Low levels of BCAA in conjunction with high levels of free-tryptophan (F-tryp) in the blood levels of free-tryptophan (F-tryp) in the blood could cause central fatiguecould cause central fatigue

F-tryp is needed for the formation of the brain F-tryp is needed for the formation of the brain neurotransmitter serotonin, which may depress neurotransmitter serotonin, which may depress the central nervous system and induce the central nervous system and induce symptoms of sleepiness and fatigue. symptoms of sleepiness and fatigue.

The amount of F-tryp The amount of F-tryp entering the brain to form entering the brain to form serotonin is limited for two serotonin is limited for two reasons:reasons:– High level of BCAA block the High level of BCAA block the

entry of F-tryp in the brainentry of F-tryp in the brain– tryptophan is normally bound tryptophan is normally bound

with the blood protein with the blood protein albumin, so it is not freealbumin, so it is not free

F-tryp may gain easier entry to the brain for tow F-tryp may gain easier entry to the brain for tow reasons:reasons:

– as muscle glycogen levels fall, the BCAA levels as muscle glycogen levels fall, the BCAA levels in the blood might also fall because they may be in the blood might also fall because they may be used to compensate for the decreased energy used to compensate for the decreased energy production from glycogenproduction from glycogen

– free fatty acid (FFA), which are bound to free fatty acid (FFA), which are bound to albumin for transport in the blood, increase and albumin for transport in the blood, increase and therefore decrease the amount of albumin therefore decrease the amount of albumin available to bind with tyrpophan. available to bind with tyrpophan.

  Results of the recent Danish study Results of the recent Danish study

suggest that an intake of BCAA has an suggest that an intake of BCAA has an anabolic effect on protein metabolism anabolic effect on protein metabolism during the recovery period after exercise rather during the recovery period after exercise rather than during the actual exercisethan during the actual exercise

Ingestion of BCAA repeatedly during exercise Ingestion of BCAA repeatedly during exercise and recovery in an amount of 100 mg/kg body and recovery in an amount of 100 mg/kg body weight does not increase the rate of release weight does not increase the rate of release of ammonia from the muscle of ammonia from the muscle

Ingestion of BCAA caused the concentration of these Ingestion of BCAA caused the concentration of these amino acids to increase by 135% in the plasma and amino acids to increase by 135% in the plasma and by 57% in muscle tissue during exercise.by 57% in muscle tissue during exercise.

The plasma concentration of alanine increased by The plasma concentration of alanine increased by 48% during exercise when BCAA were ingested, and 48% during exercise when BCAA were ingested, and the increase in the muscle concentration of alanine the increase in the muscle concentration of alanine during exercise was larger (70% versus 31% in the during exercise was larger (70% versus 31% in the placebo trial), suggesting an increased rate of alanine placebo trial), suggesting an increased rate of alanine production. production.

Arterial concentration and rate of exchange of glucose and lactate during exercise and Arterial concentration and rate of exchange of glucose and lactate during exercise and recovery. Open symbols, BCAA condition; filled symbols, placebo condition. Values for recovery. Open symbols, BCAA condition; filled symbols, placebo condition. Values for arterial concentrations are means ± SE of 7 subjects and for rates of exchange are means ± SE arterial concentrations are means ± SE of 7 subjects and for rates of exchange are means ± SE of 6 subjects. *of 6 subjects. *PP < 0.05 for BCAA vs. placebo.  < 0.05 for BCAA vs. placebo. 

Arterial concentration and rate of exchange of ammonia and free fatty acids (FFA) during Arterial concentration and rate of exchange of ammonia and free fatty acids (FFA) during exercise and recovery. Open symbols, BCAA condition; filled symbols, placebo condition. exercise and recovery. Open symbols, BCAA condition; filled symbols, placebo condition. Values for arterial concentrations are means ± SE of 7 subjects; values for rates of exchange Values for arterial concentrations are means ± SE of 7 subjects; values for rates of exchange are means ± SE of 6 subjects.  are means ± SE of 6 subjects. 

Arterial concentrations of insulin, growth hormone, and norepinephrine during exercise and Arterial concentrations of insulin, growth hormone, and norepinephrine during exercise and recovery in the 2 conditions.  recovery in the 2 conditions.  □□, BCAA condition;  , BCAA condition;  ■■, placebo condition. Values are , placebo condition. Values are means ± SE of 7 subjects. means ± SE of 7 subjects. 

Typical claims for BCAA-based Typical claims for BCAA-based productsproducts

Increased endurance Increased endurance 增加耐力 增加耐力 Prevention of fatigue Prevention of fatigue 預防疲勞 預防疲勞 Improved mental performanceImproved mental performance增進身心健康、增強增進身心健康、增強意志力 意志力 Increased energy levels Increased energy levels 增強能量 增強能量 Improved immune system function Improved immune system function 加強免疫系統 加強免疫系統 Improved post-exercise recovery (less muscle Improved post-exercise recovery (less muscle soreness and fewer upper respiratory tract infections) soreness and fewer upper respiratory tract infections) 促使運動後恢復促使運動後恢復

DiscussionDiscussionDue to its high F-tryp content, before training Due to its high F-tryp content, before training or competition what kind of FOOD should or competition what kind of FOOD should avoid to massive intake and why.avoid to massive intake and why.In your opinion what kind of sport event In your opinion what kind of sport event requires BCAA supplement for its athlete and requires BCAA supplement for its athlete and why.why.Why serotonin can cause central fatigue and Why serotonin can cause central fatigue and then decrease work capacitythen decrease work capacity