title: Growth axis maturation is linked to nutrition, growth and developmental rate.
abstract: Maturation of the mammalian growth axis is thought to be linked to the transition from fetal to post-natal life at birth. However, in an altricial marsupial, the tammar wallaby (Macropus eugenii), this process occurs many months after birth but at a time when the young is at a similar developmental stage to that of neonatal eutherian mammals. Here we manipulate growth rates and demonstrate in slow, normal and fast growing tammar young that nutrition and growth rate affect the time of maturation of the growth axis. Maturation of GH/IGF-I axis components occurred earlier in fast growing young, which had significantly increased hepatic GHR, IGF1 and IGFALS expression, plasma IGF-I concentrations, and significantly decreased plasma GH concentrations compared to age-matched normal young. These data support the hypothesis that the time of maturation of the growth axis depends on the growth rate and maturity of the young, which can be accelerated by changing their nutritional status.
authors.affiliation: School of BioSciences, The University of Melbourne, Vic. 3010, Australia.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Hetz
authors.affiliation: School of BioSciences, The University of Melbourne, Vic. 3010, Australia. Electronic address: menziesb@unimelb.edu.au.
authors.forename: Brandon R
authors.initials: BR
authors.lastname: Menzies
authors.affiliation: School of BioSciences, The University of Melbourne, Vic. 3010, Australia.
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Shaw
authors.affiliation: Department of Physiology, Monash University, Vic. 3800, Australia.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Rao
authors.affiliation: Department of Physiology, Monash University, Vic. 3800, Australia.
authors.forename: Iain J
authors.initials: IJ
authors.lastname: Clarke
authors.affiliation: School of BioSciences, The University of Melbourne, Vic. 3010, Australia.
authors.forename: Marilyn B
authors.initials: MB
authors.lastname: Renfree
mesh_terms: D000818:Animals; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D007614:Macropodidae / Q000254:growth & development / Q000502:physiology*; D009752:Nutritional Status; D011986:Receptors, Somatotropin / Q000378:metabolism
chemical_list: D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone
keywords: Endocrinology; GH; GHR; IGF-I; IGF-II; Marsupial