Journal of Nutrition

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© 2003 The American Society for Nutritional Sciences J. Nutr. 133:2783-2787, September 2003

Nutrient Metabolism

Insulin/Insulin-Like Growth Factor-I Hybrid Receptor Abundance Decreases with Development in Suckling Pigs1,2

Agus Suryawan, Hanh V. Nguyen, Renan A. Orellana, Jill A. Bush and Teresa A. Davis3

U.S. Department of Agriculture/Agriculture Research Service, Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030

3To whom correspondence should be addressed. E-mail: tdavis{at}bcm.tmc.edu.

The activation of the insulin signaling pathway that leads to translation initiation is enhanced in skeletal muscle of neonates, and decreases with development in parallel with the developmental decline in muscle protein synthesis. Because the elevated expression of insulin receptor (IR)/insulin-like growth factor-I receptor (IGF-IR) hybrids has been associated with insulin resistance in some studies, we hypothesized that IR/IGF-IR hybrid abundance and binding affinity increase with development. To test this hypothesis, we determined the abundances and binding affinities of the IR, IGF-IR and hybrid receptor in skeletal muscle of 7- and 26-d-old pigs. We found that the abundances of IR, IGF-IR and hybrid receptor were higher in muscle of 7- than 26-d-old pigs. However, the relative proportions of hybrid receptor abundance compared with IR abundance and IGF-IR abundance were similar at both ages. The binding affinities of the IR, IGF-IR and hybrid receptor also were similar at both ages. Overall, the results suggest that insulin/IGF-I hybrid receptor abundance and binding affinity do not contribute to the developmental decline in the activation of the insulin signaling pathway.

KEY WORDS: • neonate • insulin signaling • protein synthesis • muscle • growth






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