title: Reduced serum insulin-like growth factor (IGF) I is associated with reduced liver IGF-I mRNA and liver growth hormone receptor mRNA in food-deprived cattle.
abstract: Nutritional deprivation decreases blood insulin-like growth factor I (IGF-I) concentrations in a variety of species. In this study, we explored the underlying mechanism by determining the effects of food deprivation on the levels of total IGF-I mRNA and total growth hormone receptor (GHR) mRNA, as well as the levels of individual IGF-I mRNA variants and GHR mRNA variants in the liver of steers. Food deprivation for nearly 3 d decreased the levels of serum IGF-I by 63% (P < 0.01), and this decrease was associated with a 75% decrease (P < 0.01) in total IGF-I mRNA in the liver. The food deprivation-induced decrease in liver total IGF-I mRNA was associated with an equivalent decrease in the levels of both class 1 and class 2 IGF-I mRNA. In addition to IGF-I mRNA, food deprivation also decreased the levels of total GHR mRNA in the liver (P < 0.05), and this decrease was associated with a decrease in the liver expression of GHR mRNA variants 1C3 (P < 0.05) and 1A (P = 0.08). Food deprivation did not affect the levels of two other major GHR mRNA variants, 1B and 1C2, in the liver. These results demonstrate that the food deprivation-induced decrease in circulating IGF-I in steers is associated with a coordinate decrease in the expression of different IGF-I mRNA variants and a specific decrease in the expression of GHR mRNA variants 1C3 and 1A in the liver.
authors.affiliation: Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Satyanarayana
authors.initials: S
authors.lastname: Eleswarapu
authors.forename: William E
authors.initials: WE
authors.lastname: Beal
authors.forename: William S
authors.initials: WS
authors.lastname: Swecker
authors.forename: R Michael
authors.initials: RM
authors.lastname: Akers
authors.forename: Honglin
authors.initials: H
authors.lastname: Jiang
mesh_terms: D000818:Animals; D002417:Cattle; D005508:Food Deprivation / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism*; D011986:Receptors, Somatotropin / Q000235:genetics*
chemical_list: D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I