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Acute IGF‐I infusion stimulates whole body protein synthesis but does not reduce proteolysis in neonates
Author(s) -
Wilson Fiona,
Fiorotto Marta L.,
Burrin Douglas G.,
Jahoor Farook,
Nguyen Hanh V.,
Suryawan Agus,
Davis Teresa A.
Publication year - 2007
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.21.6.a1119-c
Subject(s) - proteolysis , medicine , endocrinology , insulin like growth factor , insulin , protein degradation , protein catabolism , chemistry , protein turnover , endogeny , protein biosynthesis , insulin like growth factor binding protein , leucine , nitrogen balance , growth factor , biology , biochemistry , amino acid , receptor , enzyme , organic chemistry , nitrogen
Skeletal muscle protein synthesis increases in response to a physiological rise in total insulin‐like growth factor I (IGF‐I) in neonatal pigs. To determine the response of whole body protein synthesis and degradation to IGF‐I, fasted 7‐day‐old pigs (n=4/dose) were infused with IGF‐I (0, 20, or 50 μg/(kg/hr)) to achieve levels within the physiological range. Because IGF‐I infusion lowers plasma insulin, an additional group of IGF‐I pigs was provided replacement insulin (10 ng/(kg 0.66 /min)). Plasma glucose was clamped with dextrose and AA were clamped with a balanced AA mixture at fasting levels. Whole body protein turnover was determined with 13 C‐leucine. Total IGF‐I levels in controls, low‐dose IGF‐I, high‐dose IGF‐I, and high‐dose IGF‐I with replacement insulin were 15±2, 23±2, 37±3, and 41±3 ng/ml, respectively. High dose IGF‐I increased flux (+26%, P<0.01), protein synthesis (+25%, P<0.009), AA oxidation (+28%, P<0.008), and protein balance (+29%, P<0.05) but had no effect on proteolysis. Provision of replacement insulin during the high dose IGF‐I infusion did not further enhance endogenous flux, protein synthesis, AA oxidation, or protein balance, or alter proteolysis. Low dose IGF‐I had no effect on any parameter. The results demonstrate that a physiological rise in total IGF‐I stimulates whole body protein synthesis but does not alter protein degradation in neonates. NIH AR44474, USDA 58‐6250‐6‐001