Submitted on October 3, 2005
Accepted on July 15, 2006
Peripherally administered desacetyl-
-MSH and -MSH both influence post-natal rat growth and associated rat hypothalamic protein expression
Chia-Shan Jenny Wu1, David R Greenwood2, Janine M Cooney3, Dwayne J Jensen3, Michele A Tatnell1, Garth J.S. Cooper4, and Kathleen G Mountjoy5*
1 Physiology, University of Auckland, Auckland, New Zealand
2 MtAlbert, HortResearch, Auckland, New Zealand
3 Ruakura, HortResearch, Hamilton, New Zealand
4 School of Biological Sciences, University of Auckland, Auckland, New Zealand
5 Physiology, University of Auckland, Auckland, New Zealand; Molecular Medicine and Pathology, University of Auckland, Auckland, New Zealand
* To whom correspondence should be addressed. E-mail: kmountjoy{at}auckland.ac.nz.
Desacetyl-
-MSH predominates over -MSH during development but whether it is biologically active and has a physiological role is unclear. We compared the effects of 0.3µg/g/day desacetyl--MSH with that of 0.3µg/g/day -MSH on postnatal body growth by administering the peptides subcutaneously daily for postnatal days 0-14 and also used a 2DE-gel based proteomic approach to analyse protein changes in hypothalami, the relay centre for body weight and growth regulation, after 14 days of treatment. We found the growth rate between days 1-10 was significantly decreased by desacetyl--MSH but not by -MSH, but by day 14, a time reported for development of a mature pattern of hypothalamic innervation, both peptides had significantly increased neonatal growth compared to PBS treated control rats. Desacetyl--MSH significantly increased spleen weight but -MSH had no effect. Alpha-MSH significantly decreased kidney weight but desacetyl--MSH had no effect. Both desacetyl--MSH and -MSH significantly decreased brain weight. By 14 days both peptides significantly changed expression of a number of hypothalamic proteins, specifically metabolic enzymes, cytoskeleton, signalling and stress response proteins. We show that peripherally administered desacetyl--MSH is biologically active and induces responses that can differ from those for -MSH. In conclusion, desacetyl--MSH appears to be an important regulator of neonatal rat growth.
