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Is leucine induced p70S6 kinase phosphorylation following resistance exercise dependent on elevated phenylalanine levels in human skeletal muscle?
Author(s) -
Apró William,
Holmberg HansChrister,
Rooyackers Olav,
Blomstrand Eva
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.lb273
Subject(s) - leucine , p70 s6 kinase 1 , phosphorylation , phenylalanine , ingestion , endocrinology , medicine , placebo , skeletal muscle , chemistry , amino acid , biochemistry , protein kinase b , alternative medicine , pathology
The purpose of this study was to investigate the specific role of leucine in the stimulation of the mammalian target of rapamycin signalling pathway. Six male subjects performed four heavy resistance exercise sessions, each separated by approximately one week. Subjects were randomly supplemented with one of four drinks: placebo (flavored water), leucine or essential amino acids (EAA) with and without leucine. Immediately following each exercise session, four subjects were infused with a flooding dose of L‐[2H5] phenylalanine (Inf) while two subjects served as controls (Ctrl). Muscle biopsies were taken before and one hour after exercise. In the Ctrl group, resistance exercise resulted in a substantial increase (45‐fold) in p70 S6 kinase phosphorylation when all EAA were ingested, whereas ingestion of leucine alone had no greater effect than that of placebo. In the Inf group, however, ingestion of leucine alone and EAA increased p70 S6k phosphorylation to a similar extent (35‐fold). The divergent signalling response in the two groups suggests that leucine alone is insufficient to increase p70 S6k phosphorylation. Indeed, in the Inf group, there was a strong correlation (r=0.91) between p70 S6k phosphorylation and the product of muscle leucine and phenylalanine levels. These results suggest that the stimulatory effect of leucine on p70 S6k phosphorylation is dependent on elevated muscle phenylalanine levels. Supported by the Swedish National Centre for Research in Sports