Limits to sustained energy intake during lactation were investigated in MF1 mice. The feeding of high protein to females at 21°C had negative effects on lactation performance. This was because the females consumed much less food and energy at peak lactation but their mean daily energy expenditure (DEE) was higher than that of females fed high carbohydrate diet, so the energy available for milk production was greatly reduced. The feeding of high and medium fat diets to lactating females at 21°C had positive effects on lactation performance. The females consumed much more food and energy at peak lactation but their mean DEE was the same as that of females fed low fat, so the energy available for milk production was greatly increased. The positive effects of feeding high and medium fat to the lactating mice were far greater than predicted by the heat dissipation limit hypothesis, suggesting that this hypothesis can not explain all the findings of the present study. The fixed DEE of high fat, medium fat and low fat fed females strongly support the heat dissipation limit hypothesis. Lactation significantly decreased pro-opiomelanocortin (POMC) and increased agouti-related peptide (AgRP) gene expression in the hypothalamic arcuate nucleus (ARC) despite the reduced neuropeptide Y (NPY) expression in the ARC. Activated AgRP orexigenic pathways and attenuated anorexigenic POMC pathways in the hypothalamus probably promoted the hyperplagia of lactation. The fact that AgRP increased while POMC decreased but SOCS-3 was unchanged in the lactating females exposed to 21°C indicates that the MF1 mice were sensitive to the action of leptin. mTOR was not involved in lactation hyperphagia in MF1 mice. Lactation significantly increased fat mass and obesity-associated gene (FTO) expression in the hypothalamic ventromedial nucleus. There were no changes in the main anabolic and catabolic neuropeptides at 30°C.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:499617 |
| Date | January 2008 |
| Creators | Kagya-Agyemang, James Kwame |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=25326 |
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