Poster The Annual Scientific Meeting of the Endocrine Society of Australia and the Society for Reproductive Biology 2013

Triglycerides alter the hepatic expression of growth factors, but not growth, in the developing tammar wallaby  (#223)

Jennifer Hetz 1 , Geoff Shaw 1 , Brandon R Menzies 1 , Marilyn B Renfree 1
  1. Department of Zoology, The University of Melbourne, Victoria 3010, Australia

Growth and development relies on the coordinated action of a number of growth factors, their receptors and binding proteins including growth hormone (GH) and insulin-like growth factors (IGFs). Their expression in the developing fetus appears to be sensitive to perturbations in maternally-supplied nutrients. Marsupials are born at a relatively early stage of development and subsequent growth occurs over a long lactation period. During this period, pouch young growth is highly responsive to alterations in nutrition. Early stage tammar wallaby young undergo accelerated growth and development when fostered forward into mothers at later stage of lactation1,2,3. Triacylglycerol concentrations increase substantially in late stage tammar milk of which, oleic and palmitic acids represent about 70% of total triglycerides4,5. To determine whether these fatty acids are responsible for the accelerated growth seen in fostered young, we supplemented pouch young at day 70 post-partum with either emu or macadamia oil, which have a composition of fatty acids similar to tammar milk. Growth and development of treated young was compared with control and fostered-forward (growth accelerated) young. There were no significant differences in growth parameters between supplemented and control young. However, body mass was significantly higher (p<0.01) in the fostered group. Fat mass content was significantly higher in both the oil supplemented and fostered young (p<0.04 and p<0.01 respectively) compared to control animals using dual-energy x-ray absorptiometry. Surprisingly, liver as percentage of body mass and hepatic IGF-1 mRNA expression were significantly higher in both groups relative to controls (p<0.05). No significant differences were found in pituitary GH mRNA expression. Thus, the fatty acids present in late-stage of tammar milk do affect liver mass and mRNA expression of a key growth factor. Nevertheless, the young also require other milk components to achieve the accelerated growth and development observed in fostered tammar young.

  1. Trott J.L. et al. (2003) Biology of Reproduction 68: 929-36
  2. Menzies et al. (2007) Reproduction, Fertility and Development 19: 976-83
  3. Kwek J.H. et al. (2009) Mechanisms of Development 126: 449-63
  4. Green B. et al. (1980) Australian Journal of Biological Sciences 33: 35–42
  5. Green B. et al. (1988) Australian Journal of Zoology 36: 217-27