Superiority of Tetrapeptide Tyr-Gly-Leu-Phe over Amino Acid Mixture: Mechanisms Underlying Enhanced Systemic Amino Acid Delivery, Anti-Fatigue Efficacy, and Muscle Damage Repair.

YGLF was rapidly degraded in vitro, with less than 1% remaining intact.

• The abstract states that YGLF underwent 'rapid in vitro degradation (<1% intact)'.
• The degradation result is presented as contrasting with its superior in vivo effect on plasma amino acid levels.

YGLF raised plasma amino acid levels more than the equimolar amino acid mixture 15 min after ingestion.

• Plasma amino acids were 51.97 mg/100 mL after YGLF versus 46.34 mg/100 mL after the AA mixture at 15 min postingestion.
• The comparison used an equimolar amino acid mixture as the control.

After exercise, YGLF outperformed the amino acid mixture on several fatigue-related measures.

• YGLF further increased muscle amino acids and blood glucose relative to the AA mixture.
• YGLF reduced metabolic byproducts more than the AA mixture.
• YGLF activated AMPK.

After muscle damage, the amino acid mixture and YGLF produced different transcriptomic responses.

• Transcriptomics showed that the AA mixture primarily modulated energy metabolism.
• YGLF uniquely upregulated muscle growth genes.

YGLF promoted muscle damage repair through the Sestrin2/mTOR and Pax7/MYOD pathways.

• Western blotting confirmed involvement of the Sestrin2/mTOR pathway.
• Western blotting also confirmed involvement of the Pax7/MYOD pathway, which is associated with muscle regeneration.

The findings indicate that YGLF has bioactivity distinct from free amino acids, supporting the use of specific peptides in sports nutrition and muscle recovery.

• The comparison covered three stages: postingestion absorption, postexercise fatigue, and muscle damage repair.
• The authors conclude this establishes a rationale for using specific peptides rather than free amino acids.