Insulin-like growth factors and body growth in chickens divergently selected for high or low growth rate.
Insulin-like growth factors (IGFs) stimulate growth rate in a number of animal species and are likely to contribute to genetic variations of growth potential. The present study was designed to link levels of IGF-I and IGF-II mRNA and peptides with growth rate in divergently selected genotypes of chickens with high (HG) or low (LG) growth rates. Circulating IGF-I and -II and hepatic mRNA levels were measured under ad libitum feeding conditions from 1 to 12 weeks of age, and at 6 weeks of age under three different nutritional conditions (fed, fasted for 16 or 48 h, re-fed for 4 or 24 h after a 48-h fast). IGF binding proteins (IGFBPs) were also measured. Circulating IGFs increased with age and were higher in HG chickens from 1 to 6 weeks. They decreased with fasting and only IGF-II was fully restored after 24 h of re-feeding, while IGF-I remained low. A significant decrease in steady state IGF-I mRNA levels was also observed with fasting. Across the nutritional study, hepatic IGF-I mRNAs were significantly higher in HG chickens. Variations of IGF-II mRNA levels with nutritional state or genotype exhibited a similar trend. IGFBP (28, 34 and 40 kDa) levels increased with age, while only faint differences were observed between genotypes. IGFBP-28 transiently increased with fasting and was inversely related to blood glucose and insulin levels, suggesting that it is equivalent to mammalian IGFBP-1. In HG chickens, IGFBP-28 and IGFBP-34 levels decreased markedly following re-feeding. Therefore, high and low growth rates were respectively associated with high and low IGF-I and -II levels, supporting the hypothesis of a stimulatory role for both IGFs during post-hatching growth of chickens.
Beccavin
C
C
Institut National de la Recherche Agronomique, Centre de Recherche de Tours, Station de Recherches Avicoles, 37380 Nouzilly, France.
Chevalier
B
B
Cogburn
L A
LA
Simon
J
J
Duclos
M J
MJ
D000375:Aging / Q000502:physiology; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002645:Chickens / Q000097:blood / Q000235:genetics / Q000254:growth & development*; D015870:Gene Expression; D005838:Genotype; D006128:Growth / Q000502:physiology*; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008297:Male; D009752:Nutritional Status; D012333:RNA, Messenger / Q000235:genetics; D015430:Weight Gain / Q000502:physiology
D001786:Blood Glucose; D007328:Insulin; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II