Use of a leucine clamp to demonstrate that IGF-I actively stimulates protein synthesis in normal humans.

Russell-Jones, DL, Umpleby, AM, Hennessy, TR, Bowes, SB, Shojaee-Moradie, F, Hopkins, KD, Jackson, NC, Kelly, JM, Jones, RH and Sönksen, PH (1994) Use of a leucine clamp to demonstrate that IGF-I actively stimulates protein synthesis in normal humans. Am J Physiol, 267 (4 Pt 1). E591-E598.

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Abstract

Insulin-like growth factor I (IGF-I) is thought to mediate the anabolic action of growth hormone. A glucose and amino acid clamp technique was used to investigate the effects of a 3-h intravenous infusion of either 43.7 pmol.kg-1.min-1 (20 micrograms.kg-1.h-1) IGF-I or 3.4 pmol.kg-1.min-1 (0.5 mU.kg-1.min-1) insulin on whole body leucine turnover in five normal human volunteers. During the IGF-I infusion, IGF-I levels increased (P < 0.01; 26.6 +/- 2.8 to 88.9 +/- 14.2 nmol/l) and insulin levels fell (P < 0.05; 0.096 +/- 0.018 to 0.043 +/- 0.009 nmol/l). During the insulin infusion, insulin levels increased (P < 0.01; 0.057 +/- 0.013 to 0.340 +/- 0.099 nmol/l), and there was no change in IGF-I. There was no significant change in leucine production rate (Ra; a measure of protein degradation) during the IGF-I infusion (2.23 +/- 0.17 to 2.13 +/- 0.2 mumol.kg-1.min-1), but there was an increase (P < 0.03) in nonoxidative leucine disposal rate (Rd; a measure of protein synthesis; 1.83 +/- 0.15 to 2.05 +/- 0.21 mumol.kg-1.min-1). In contrast, insulin reduced (P < 0.02) leucine Ra (1.81 +/- 0.24 to 1.47 +/- 0.24 mumol.kg-1.min-1) and had no effect on nonoxidative leucine Rd (1.44 +/- 0.25 to 1.41 +/- 0.22 mumol.kg-1.min-1). We conclude that IGF-I, under conditions of adequate substrate supply, directly increases protein synthesis in contrast to insulin, which exerts its anabolic action by reducing proteolysis.

Item Type:	Article
Divisions :	Surrey research (other units)
Authors :	Name Email ORCID Russell-Jones, DL Umpleby, AM Hennessy, TR Bowes, SB Shojaee-Moradie, F Hopkins, KD Jackson, NC n.jackson@surrey.ac.uk Kelly, JM Jones, RH Sönksen, PH
Date :	October 1994
Uncontrolled Keywords :	Adult, Humans, Insulin, Insulin-Like Growth Factor I, Leucine, Male, Middle Aged, Protein Biosynthesis, Reference Values
Related URLs :	Author
Depositing User :	Symplectic Elements
Date Deposited :	17 May 2017 09:32
Last Modified :	24 Jan 2020 17:07
URI:	http://epubs.surrey.ac.uk/id/eprint/824109

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