Interleukin-15 decreases proteolysis in skeletal muscle: a direct effect.
Incubation of rat isolated skeletal muscles (extensor digitorum longus) in the presence of 100 ng/ml of human recombinant interleukin-15 (IL-15) resulted in a significant decrease in total proteolytic rate, while it had no effect on total protein synthesis as measured by the incorporation of (14)C-phenylalanine into muscle protein. In addition, IL-15 had no effect on either amino acid uptake (as determined by the tissue uptake of labelled [1-(14)C]MeAIB) or alanine utilization by incubated skeletal muscles. Similarly, a single injection of IL-15 (100 microg/kg) in vivo did not result in any changes in amino acid uptake (as measured by the tissue uptake of alpha-[1-(14)C]AIB) or alanine metabolism, with the exception of alanine carbon incorporation into lipids, which was significantly increased in adipose tissue as a result of IL-15 administration. The results suggest that the main mechanism involved in the anabolic effects of IL-15 in skeletal muscle relies on a decrease in the proteolytic rate.
Busquets
Sílvia
S
Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Spain.
Figueras
Maria T
MT
Meijsing
Sebastiaan
S
Carbó
Neus
N
Quinn
Lebris S
LS
Almendro
Vanessa
V
Argilés
Josep M
JM
López-Soriano
Francisco J
FJ
D000409:Alanine / Q000378:metabolism; D000621:Aminoisobutyric Acids / Q000493:pharmacokinetics; D000818:Animals; D002250:Carbon Radioisotopes; D002460:Cell Line; D006801:Humans; D066298:In Vitro Techniques; D019409:Interleukin-15 / Q000494:pharmacology*; D008297:Male; D008954:Models, Biological; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000494:pharmacology
D000621:Aminoisobutyric Acids; D002250:Carbon Radioisotopes; D019409:Interleukin-15; D009124:Muscle Proteins; D011994:Recombinant Proteins; C017911:2-(methylamino)isobutyric acid; D000409:Alanine