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1,25( OH ) 2 ‐vitamin D 3 enhances the stimulating effect of leucine and insulin on protein synthesis rate through A kt/ PKB and m TOR mediated pathways in murine C 2 C 12 skeletal myotubes
Author(s) -
Salles Jérôme,
Chanet Audrey,
Giraudet Christophe,
Patrac Véronique,
Pierre Philippe,
Jourdan Marion,
Luiking Yvette C.,
Verlaan Sjors,
Migné Carole,
Boirie Yves,
Walrand Stéphane
Publication year - 2013
Publication title -
molecular nutrition and food research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.495
H-Index - 131
eISSN - 1613-4133
pISSN - 1613-4125
DOI - 10.1002/mnfr.201300074
Subject(s) - leucine , insulin , chemistry , western blot , vitamin d and neurology , calcitriol receptor , receptor , microbiology and biotechnology , medicine , endocrinology , biochemistry , amino acid , biology , gene
Scope In recent years, there has been a growing body of evidence pointing to an effect of vitamin D on muscle mass and function. Our aim was to investigate the combined effect of 1,25( OH ) 2 ‐vitamin D 3 (1,25( OH ) 2 D 3 ) with anabolic factors insulin and leucine on protein fractional synthesis rate ( FSR ) and regulation in the mouse C 2 C 12 myotube. Methods and results After differentiation, myotubes were cultured in 1,25( OH ) 2 D 3 solutions at 0, 1, or 10 nM for 72 h. Cells were treated by l ‐[1– 13 C ]valine and puromycin in presence or not of leucine and insulin, and protein FSR was determined by measuring tracer enrichments and puromycin incorporation in proteins, respectively. Protein expression and phosphorylation state of insulin receptor ( IR ), A kt, GSK 3, m TOR , p70 S 6 kinase, rp S 6, and 4 EBP 1 were measured by W estern blot. Transcript levels of IR and 1,25( OH ) 2 D 3 receptor ( VDR ) were determined by q PCR . 1,25( OH ) 2 D 3 (10 nM) with leucine and insulin increased protein FSR in C 2 C 12 myotubes (14–16%). IR and VDR m RNA expression was increased with 1,25( OH ) 2 D 3 treatment. The A kt/m TOR ‐dependent pathway was activated by insulin and leucine and further enhanced by 1,25( OH ) 2 D 3 . Conclusion 1,25( OH ) 2 D 3 sensitizes the A kt/m TOR ‐dependant pathway to the stimulating effect of leucine and insulin, resulting in a further activation of protein synthesis in murine C 2 C 12 skeletal myotubes.