Effects of acute hypoglycemia on the orexin system in rat.
OBJECTIVE
To evaluate the effects of acute glucose level changes on expression of prepro-orexin, orexin 1 receptor (OX1R) and orexin 2 receptor (OX2R) mRNA in rat hypothalamus tissue and pancreatic islets cells.


METHODS
Thirty adult male Wistar rats were randomly divided into three equal groups (n = 10). The acute hypoglycemia rat model was induced by a single subcutaneous injection of insulin. Twenty acute hypoglycemia rats were divided into group B and group C. Group B was allowed to eat freely, while group C was food-deprived. Control rats were injected the same volume of saline. The effect of glucose levels (2.8 mmol/L and 8.3 mmol/L) on pancreatic islet cell orexin system was detected in pancreas islet cell cultured in vitro. The expression of prepro-orexin and OXR mRNA was examined in rat hypothalamus tissue and pancreatic islets cell cultured in vitro using reverse transcription-polymerase chain reaction (RT-PCR).


RESULTS
Expression of orexin mRNA increased about 150% for the food-deprived hypoglycemia rats in comparison with control group (P < 0.01), whereas expression of OX1R mRNA decreased up to 30% (P < 0.01). However, expression of OX2R mRNA was unchanged in comparison with control group. In vitro, after incubation with 2.8 mmol/L glucose for 6 hours, the expression of prepro-orexin mRNA increased 2 times in rat pancreas islet cells in comparison with 8.3 mmol/L glucose group (P < 0.01). But the expression of OX1R mRNA was not sensitive to acute glucose fluctuation.


CONCLUSIONS
Orexin in rat hypothalamus is stimulated by decline in blood glucose and inhibited by signals related to feeding. Moreover, glucose plays a role in modulating the gene expression of prepro-orexin in rat pancreatic islet cells.
Zhao
Yu-yan
YY
Department of Endocrinology, the First Affiliated Hospital, China Medical University, Shenyang 110001. g572@sina.com
Guo
Lei
L
Du
Jian
J
Liu
Guo-liang
GL
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D007003:Hypoglycemia / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D007515:Islets of Langerhans / Q000378:metabolism; D008297:Male; D009479:Neuropeptides / Q000096:biosynthesis* / Q000235:genetics; D064446:Orexin Receptors; D000068797:Orexins; D011498:Protein Precursors / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide / Q000096:biosynthesis* / Q000235:genetics
D001786:Blood Glucose; C578627:Hcrtr1 protein, rat; D007328:Insulin; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D011498:Protein Precursors; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide; D005947:Glucose