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Hypothalamic orexin expression: modulation by blood glucose and feeding.
X J Cai1, P S Widdowson, J Harrold
1Department of Medicine, University of Liverpool, UK.
Diabetes
|October 27, 1999
Summary
Orexins, peptides that stimulate feeding, are regulated by glucose levels. Their expression increases with fasting and hypoglycemia, suggesting a role in short-term energy balance.
Area of Science:
- Neuroscience
- Endocrinology
- Metabolism
Background:
- Orexins (hypocretins) are peptides produced in the lateral hypothalamic area (LHA) that stimulate feeding.
- The precise role of orexins in regulating feeding behavior under various physiological conditions remains to be fully elucidated.
Purpose of the Study:
- To investigate the role of orexins in feeding regulation in rats.
- To measure hypothalamic prepro-orexin mRNA levels under conditions of increased hunger and altered metabolic states.
Main Methods:
- Measurement of hypothalamic prepro-orexin mRNA levels in rats.
- Experimental conditions included fasting, acute and chronic hypoglycemia, diabetes, and glucoprivation.
Main Results:
- Prepro-orexin mRNA levels significantly increased after 48 hours of fasting and acute hypoglycemia when food was withheld.
- Orexin expression was not altered by chronic food restriction, diabetes, hypoglycemia with food available, overconsumption, or systemic glucoprivation.
- Orexin expression was stimulated by low plasma glucose in the absence of food.
Conclusions:
- Orexins may play a role in the short-term regulation of energy homeostasis.
- Orexin neurons may initiate feeding in response to falling glucose levels and terminate feeding after food ingestion.
- Orexin neurons in the LHA might be the neuronal population sensitive to glucose fluctuations and inhibited by feeding signals.