Faculty Collaboration Database

Energy flux, more so than energy balance, protein intake, or fitness level, influences insulin-like growth factor-I system responses during 7 days of increased physical activity. J Appl Physiol (1985) 2007 Nov;103(5):1613-21

Date

08/19/2007

Pubmed ID

17702838

DOI

10.1152/japplphysiol.00179.2007

Scopus ID

2-s2.0-35648956653 (requires institutional sign-in at Scopus site)   40 Citations

Abstract

The purpose of this study was to determine the impact of dietary factors and exercise-associated factors on the response of IGF-I and its binding proteins (IGFBPs) during a period of increased physical activity. Twenty-nine men completed a 4-day (days 1-4) baseline period of a controlled energy balanced diet while maintaining their normal physical activity level followed by 7 days (days 5-11) of a 1,000 kcal/day increase in physical activity above their normal activity levels. Two subject groups, one sedentary (Sed, mean Vo(2peak): 39 mlxkg(-1)xmin(-1), n = 7) and one fit (FIT1, mean Vo(2peak): 56 ml.kg(-1)xmin(-1), n = 8) increased energy intake to maintain energy balance throughout the 7-day intervention. In two other fit subject groups (FIT2, n = 7 and FIT3, n = 7), energy intake remained at baseline resulting in a 1,000 kcal/day exercise-induced energy deficit. Of these, FIT2 received an adequate protein diet (0.9 g/kg), and FIT3 received a high-protein diet (1.8 g/kg). For all four groups, IGF-I, IGFBP-3, and the acid labile subunit (ALS) were significantly decreased by day 11 (27 +/- 4%, 10 +/- 2%, and 19 +/- 4%, respectively) and IGFBP-2 significantly increased by 49 +/- 21% following day 3. IGFBP-1 significantly increased only in the two negative energy balance groups, FIT2 (38 +/- 6%) and FIT3 (46 +/- 8%). Differences in initial fitness level and dietary protein intake did not alter the IGF-I system response to an acute increase in physical activity. Decreases in IGF-I were observed during a moderate increase in physical activity despite maintaining energy balance, suggesting that currently unexplained exercise-associated mechanisms, such as increased energy flux, regulate IGF-I independent of energy deficit.

Author List

Rarick KR, Pikosky MA, Grediagin A, Smith TJ, Glickman EL, Alemany JA, Staab JS, Young AJ, Nindl BC

Author

Kevin Richard Rarick PhD Assistant Professor in the Pediatrics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Body Composition
Carrier Proteins
Dietary Proteins
Energy Metabolism
Glycoproteins
Humans
Insulin-Like Growth Factor Binding Protein 1
Insulin-Like Growth Factor Binding Protein 2
Insulin-Like Growth Factor Binding Protein 3
Insulin-Like Growth Factor Binding Proteins
Insulin-Like Growth Factor I
Male
Motor Activity
Nutritional Physiological Phenomena
Oxygen Consumption
Physical Fitness
Time Factors