Effect of dietary energy restriction on the expression of insulin-like growth factor-I in liver and corpus luteum of heifers.
The effects of energy balance on the corpus luteum may be mediated by IGF-I. Our objective was to determine whether negative energy balance decreases expression of IGF-I mRNA in the liver or corpus luteum of heifers. For four consecutive estrous cycles, 14 Holstein heifers were maintained in negative or positive energy balance to lose 510 g/d of BW or gain 560 g/d of BW, respectively. The liver was biopsied and the corpus luteum was collected 7 d after fourth estrus. Heifers fed below maintenance had a smaller corpus luteum than did control heifers. Compared with that of controls, negative energy balance increased growth hormone in serum but decreased IGF-I in serum and the abundance of mRNA for growth hormone receptor and IGF-I in liver. In contrast, diet did not affect the abundance of mRNA for the growth hormone receptor or IGF-I in luteal tissue. Negative energy balance increased IGF binding protein-2 in serum but did not affect IGF binding protein-3. We conclude that negative energy balance of cattle decreases IGF-I mRNA abundance in the liver but not in the 7-d corpus luteum. If decreased IGF-I mediates the adverse effect of negative energy balance on luteal growth, the mode of action is likely endocrine, not autocrine or paracrine.
Vandehaar
M J
MJ
Department of Animal Science, Michigan State University, East Lansing 48824, USA.
Sharma
B K
BK
Fogwell
R L
RL
D000818:Animals; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000378:metabolism; D002417:Cattle / Q000378:metabolism*; D003338:Corpus Luteum / Q000378:metabolism*; D004032:Diet; D002149:Energy Intake; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D015870:Gene Expression; D018971:Insulin-Like Growth Factor Binding Protein 2; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008099:Liver / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism
D002352:Carrier Proteins; D005230:Fatty Acids, Nonesterified; D018971:Insulin-Like Growth Factor Binding Protein 2; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I