NUTRITIONAL REGULATION OF CELL AND ORGAN GROWTH, DIFFERENTIATION, AND DEVELOPMENT
Location: Children Nutrition Research Center (Houston, Tx)
Title: Acute IGF-I infusion stimulates whole body protein synthesis but does not reduce proteolysis in neonates
Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: February 7, 2007
Publication Date: April 28, 2007
Citation: Wilson, F., Fiorotto, M.L., Burrin, D.G., Jahoor, F., Nguyen, H.V., Suryawan, A., Davis, T.A. 2007. Acute IGF-I infusion stimulates whole body protein synthesis but does not reduce proteolysis in neonates [abstract]. The Federation of American Societies for Experimental Biology Journal. 21(6):A1119.
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.