Influence of nutrition on hepatic IGF-I mRNA levels and plasma concentrations of IGF-I and IGF-II in meat-type chickens

• Published in: Journal of endocrinology Vol. 149; no. 1; pp. 181 - 190
• Main Authors: KITA, K, TOMAS, F. M, OWENS, P. C, KNOWLES, S. E, FORBES, B. E, UPTON, Z, HUGHES, R, BALLARD, F. J
• Format: Journal Article
• Language: English
• Published: Colchester BioScientifica 01.04.1996; Portland Press
• Subjects: Animal Nutritional Physiological Phenomena; Animals; Apud cells. Peptide and protein hormones. Growth factors; Biological and medical sciences; Blotting, Western; Chickens - blood; Chickens - metabolism; Fasting - blood; Female; Fundamental and applied biological sciences. Psychology; Insulin-Like Growth Factor Binding Proteins - blood; Insulin-Like Growth Factor I - genetics; Insulin-Like Growth Factor I - metabolism; Insulin-Like Growth Factor II - metabolism; Liver - metabolism; Radioimmunoassay; RNA, Messenger - metabolism; Vertebrates: endocrinology; Insulin like growth factor binding protein; Vertebrata; Nutrition; Liver; Chicken; Aves; Gene expression; Insulin like growth factor 1; Insulin like growth factor 2
• ISSN: 0022-0795; 1479-6805
• DOI: 10.1677/joe.0.1490181

Abstract We have examined the influence of nutrition on plasma IGF-I, IGF-II and IGF-binding protein (IGFBP) levels and on hepatic IGF-I gene expression in young meat-type chickens. Plasma IGF concentrations were measured by using RIA with recombinant chicken IGFs as standards. In chickens fed the control diet containing 200 g/kg dietary protein ad libitum for 7 days, plasma IGF-I concentrations increased significantly from those found in the initial control group. Food restriction for either 4 or 7 days decreased plasma IGF-I by 30% from the initial control. When chickens were refed ad libitum for 3 days after 4 days of restricted feeding, plasma IGF-I levels recovered to those of the control birds fed ad libitum. In chickens eating a low protein diet (100 g/kg protein), the plasma IGF-I tended to be lowered but the decrease was not significant. Although the intensity of IGF-I and β-actin mRNA bands protected in the RNase protection assay was changed by nutrition, no statistical effect of nutrition on the ratio of IGF-I to β-actin was observed. The nutritional treatments had no effect on plasma IGF-II concentrations. Western ligand blot and chromatographic analyses were used to investigate the influence of nutrition on IGFBP profiles. Both IGF-I and IGF-II ligands in the Western ligand blot revealed the most intense binding at 30 kDa for plasma obtained from chickens with restricted food intake. The 30 kDa band also appeared at a lower intensity in the group fed a low protein diet but not in any other groups. These observations were confirmed by neutral gel chromatography. The chicken IGF-II ligand revealed an intensely labelled band corresponding to 75 kDa and this was not affected by nutrition. IGF-I and IGFBP concentrations in the plasma of young broiler chickens were influenced by nutritional state but IGF-II concentrations were not. The lack of a response in circulating IGF-II levels may have been due to the presence of high concentrations of a 75 kDa specific binding protein which did not respond to nutrition in this experiment. Journal of Endocrinology (1996) 149, 181–190