Insulin-like growth factors and body growth in chickens divergently selected for high or low growth rate

Abstract

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 refeeding. 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.

Domestication and growth hormone transgenesis cause similar changes in gene expression in coho salmon ( Oncorhynchus kisutch )

“…In domestic dogs, elevated GH (during early life) and IGF1 are associated with large dog breeds (44,45), and the IGF1 locus has been associated with variation influencing body size (46). Extensive work in domestic chickens and turkeys has found GH and IGF1 to be variably correlated with growth rate or to have an ability to further stimulate organismal or cellular growth (47)(48)(49)(50). In fish, fast-growing strains of rainbow trout have not been found to possess elevated plasma or pituitary GH or plasma IGF1 (51), and fast-growing Atlantic salmon showed no change in IGF1 but pituitary and plasma GH were elevated when examined across stages (52).…”

Regulation of ANKRD9 expression by lipid metabolic perturbations

“…The use of animals in these studies complies with the University of Delaware Animal Care and Use Guidelines. Experimental paradigms for thyroid hormone manipulation and nutritional management were described previously (7,8,29). Total RNA samples were isolated using RNeasy mini kit (Qiagen, Valencia, CA).…”

Differential expression of growth and immunity related genes influenced by in ovo supplementation of amino acids in broiler chickens

“…The dietary intrinsic factors and related metabolic interactions have direct as well as indirect influence on growth via expression and regulation of genes. Moreover, the genes present on the somatotropic axis respond to nutrition differently at the level of transcription (Beccavin et al 2001). The growth hormone (GH) that regulates the growth exerts its effects mainly by insulin-like growth factor-I (IGF-I), which is synthesized in the liver under GH control and secreted into the circulation (Mc Murtry et al 1997).…”