Effects of insulin-like growth factor-I (IGF-I), insulin and combined IGF-I-insulin infusions on protein metabolism in dogs.
The effect of infusions of recombinant insulin-like growth factor-I (IGF-I) (34, 103 or 688 pmol min-1 kg-1), insulin (3.4, 10.3 or 68.8 pmol min-1 kg-1) or combined infusions (34 pmol IGF-I + 3.4 pmol min-1 kg-1 insulin or 103 pmol IGF-I + 3.4 pmol min-1 kg-1 insulin) on protein metabolism, using an infusion of [1-14C]leucine was investigated in anaesthetized fasted dogs. Leucine concentration, production rate (measure of protein degradation), oxidation rate and non-oxidative disappearance rate (measure of protein synthesis) were decreased in a similar dose dependent manner by the IGF-I and insulin infusions (P < 0.01). The decrease in these measurements of leucine metabolism were greater following 34 pmol IGF-I + 3.4 pmol insulin than with either component infused alone (P < 0.05). Free fatty acid concentrations were decreased by all insulin doses (P < 0.01) but only by 103 and 688 pmol min-1 kg-1 insulin-like growth factor (P < 0.05, P < 0.01). These data demonstrate that IGF-I, like insulin, has a dose dependent effect on protein metabolism and that combined insulin and IGF-I infusions have additive effects on protein metabolism.
Umpleby
A M
AM
Department of Endocrinology and Chemical Pathology, St Thomas's Campus, UMDS, London, UK.
Shojaee-Moradie
F
F
Thomason
M J
MJ
Kelly
J M
JM
Skottner
A
A
Sonksen
P H
PH
Jones
R H
RH
D000818:Animals; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005230:Fatty Acids, Nonesterified / Q000097:blood; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage / Q000494:pharmacology*; D007930:Leucine / Q000378:metabolism; D008297:Male; D011506:Proteins / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000187:drug effects
D005230:Fatty Acids, Nonesterified; D007328:Insulin; D011506:Proteins; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D007930:Leucine