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Leucine's Impact on Muscle Protein Synthesis

Investigative study examining the role that leucine plays in the quality and quantity of muscle protein synthesis
by

Eric Yager-Schweller

on 12 November 2012

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Transcript of Leucine's Impact on Muscle Protein Synthesis

Leucine's Impact on
Muscle Protein Synthesis Eric Yager-Schweller
CME 590 - Comfort
Fall 2012 Effects of Resistance Exercise Agenda: Background
Mechanism
Performance
Conclusion
Questions Importance of Leucine as a BCAA: Mechanism?
How much?
How often?
Performance Enhancements
Clinical Studies What is Leucine? Today's Emphasis MECHANISM:
Leucine Sensing, Transport, and Anabolic Signaling What do some of the most commonly used post-wokout nutritional meals consist of? Carbohydrates
Quality Protein
BCAAs
Electrolytes What is a BCAA? What is Leucine? Relative rates of MPS and degradation undergo cyclical patterns depending on resistance exercises and nutritional intake Catabolism Anabolism Exercise stimulates muscle synthesis as well as muscle degradation
Muscle wasting = imbalance in catabolism versus anabolism due to lack of nutritional replenishment
EAAs primarily responsible for MPS
In particular, leucine is a key regulator of MPS and is vital to maximizing MPS levels with its anabolic responses Amino acids are organic substances containing both an amino group and an acidic group
Differentiated by their side chains Leucine is considered an EAA
Cannot be synthesized de novo Anabolic Response and MPS MPS occurs through modulation of mRNA translation; altered by:
Energy status
Growth factors
Nutrient (AA) availibility
mTORC
Mammalian target of rapamycin complex
Nutritionally regulated signaling component of MPS affecting mRNA translation MPS and mTOR Signaling mTOR is the primary component of the protein synthetic insulin signaling cascade
Regulates mRNA translation via:
Inactivation of the eukaryotic initiation factor binding protein (4EB1) which is a repressor of mRNA translation
Activation of p70 S6 kinase
Changes phosphorylation state of intracellular signaling proteins Affects mRNA translation initiation and elongation Directly influences rate of MPS hVps34 MEK P13K TSC2 Akt mTOR 4E-BP1 p70 RHEB mRNA translation initiation & MPS e1F4E Leucine and Anabolic Signaling Conclusion: BCAAs (Leucine) is needed after exercise to promote MPS via the mTOR pathway Performance:
Leucine's Role in Enhancing Muscle Growth Exercise and Central Fatigue Sustained exercise: decreases blood glucose levels and increases free tryptophan/BCAAs ratios


synthesis and release of 5-HT (5-hydroxytryptamine)


Elevated 5-HT results in development of central fatigue Exercise and Central Fatigue Ingestion of BCAAs (Leucine) increases their concentration in plasma


Prevents increase in free tryptophan/BCAAs


Decreases synthesis of 5-HT and delays central fatigue Dose Dependency Studies conducted regarding the optimal leucine dose needed to promote MPS
Moore et al. administered 0, 5, 10, 20, or 40g of egg protein (high quality EAA) after a bout of resistance exercise
Changes in MPS were dose dependent
Maximal stimulation at 20g protein (~9g EAA or ~3.5g of leucine)
Doses beyond 20g resulted in increased leucine oxidation Protein availability is crucial for optimizing adaptions in skeletal muscle protein in response to resistance/endurance exercises Timing of Leucine Ingestion MPS and the FSR of protein peak ~45-90min after leucine ingestion
Returns to baseline at 3 hours Study by Norton et al. demonstrated these results in MPS and FSR after a meal containing 20% energy from whey protein was consumed Improving Resistance Exercise Performance Mechanical stimuli (RE) induces microdamages to muscle fibers Effects strength, tension, and DOMS Recent studies by Shimomura et al. examined RE-induced muscle damage 5g of BCAA before squat exercises
DOMS peaked after second day of exercise; however, significantly lower than placebo group In Conclusion: Conclusion: Leucine stimulates MPS via the mTOR pathway
The correct dosage and timing of leucine ingestion can reduce DOMS and promote faster recovery
These findings highlight the power of AA biochemistry in augmenting athletic activities Works Cited: (Zoom in to see specific details) Questions or Comments? with BCAA placebo Leucine Insulin RE
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