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Title: Acute regulation of IGF-I by alterations in post-exercise macronutrients

Author
item FOSTER, E - Auburn University
item FISHER, G - Auburn University
item SARTIN, J - Auburn University
item Elsasser, Theodore
item WU, G - Texas A&M University
item COWAN, W - Texas A&M University
item PASCOE, D - Texas A&M University

Submitted to: Amino Acids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2011
Publication Date: 2/4/2011
Citation: Foster, E.B., Fisher, G., Sartin, J.L., Elsasser, T.H., Wu, G., Cowan, W., Pascoe, D.D. 2011. Acute regulation of IGF-I by alterations in post-exercise macronutrients. Amino Acids. Available: http://www.ncbi.nlm.nih.gov/pubmed/21293890.

Interpretive Summary: Practical ways to modulate growth in domestic and companion animals are still considered a laudable goal of both animal and human nutrition and medicine. A major regulator of growth and metabolism in young animals and people is the insulin-like growth factor system. While many years of study of the insulin-like growth factor system’s effects on animal growth have been documented, none has focused on the ability of specific nutrient balance to change the status of free, noncarrier bound components of the IGF-1 axis and in models other than static model systems. Exercise is known to influence the gene expression patterns of growth factors and the combination of exercise coupled with nutrition has largely been ignored by the research community as a means of regulating lean growth through the insulin-like growth factor system. . Through controlled applications of both aerobic exercise and specific nutrient ingestion, changes in the free components of the insulin-like growth factor axis were studied by our laboratories. This is the first study to demonstrate collectively that free IGF-I, IGFBP-1, and IGFBP-2 concentrations can be manipulated through exercise and dietary alteration. While the importance of exercise and post-exercise nutrition has long been known, this investigation adds valuable insight into the mechanisms of growth factor control and regulation. The precise physiological implications of these findings are as yet unknown, as the specific role of IGF-I in the peripheral vasculature is incompletely understood at this time. Thus while the exact practical implications of these findings are unclear, their main significance lies in the fact that they draw us closer to unraveling the complex regulatory dynamics of the IGF system.

Technical Abstract: This investigation sought to examine the contributions of exercise and nutrient replenishment on in vivo regulation of the insulin-like growth factor-I (IGF-I) axis components. Eight college-aged males completed three high-intensity interval training (HIIT) protocols followed by three post-exercise nutritional protocols: (1) placebo (EX); (2) carbohydrate only (CHO); and (3) essential amino acid/carbohydrate (EAA/CHO). Samples were analyzed for growth hormone (GH), free IGF-I, IGFBP-1, IGFBP-2, insulin, hematocrit, hemoglobin, serum leucine, matrix metalloproteinase-9 (MMP-9) proteolytic activity, and presence of IGFBP-3 protease activity. No evidence for IGFBP-3 proteolysis was observed. Significant increases in [free IGF-I] and [leucine] were observed in the EAA/CHO group only. Significant differences were noted in [IGFBP-1] and [IGFBP-2] across conditions. Significant increases in [GH] and MMP-9 activity were observed in all groups. These results indicate that post-exercise macronutrient ratio is a determinant of [free IGF-I], [IGFBP-1 and -2] and may play a role in modulating the IGF-I axis in vivo.