Orexin has several biological functions, including the regulation of reproductive endocrine signaling, which has received much attention. However, little is known about the mechanism through which orexin regulates the...Orexin has several biological functions, including the regulation of reproductive endocrine signaling, which has received much attention. However, little is known about the mechanism through which orexin regulates the levels of neuroendocrine hormones and peptides. We injected orexin A or physiological saline into the lateral ventricle of 10 ovariectomized （OVX） gilts, and determined the subsequent changes in serum luteinizing hormone （LH） concentration by using radioimmunoassay （RIA）. We also examined the expression of GnRH, NPY, and POMC mRNAs in the hypothalamus and that of LH, folliclestimulating hormone （FSH）, POMC, and ghrelin mRNAs in the pituitary by using semi-quantitative reverse transcription polymerase chain reaction. We found the following results： （1） Orexin A transiently promoted LH secretion; serum LH concentration started to increase at 10 min after the orexin injection, peaked at 30 min, and returned to its initial level at 1.5 h; （2） orexin A upregulated GnRH mRNA expression and downregulated NPY and POMC mRNAs expression in the hypothalamus; （3） orexin A upregulated LH and FSH mRNAs expression （FSH, P〉 0.05）, but downregulated ghrelin mRNA expression in the pituitary. No significant effects were observed on the pituitary expression of FSH and POMC mRNAs. Our data suggest that orexin A regulates reproductive function by stimulating GnRH and LH release directly and indirectly via its effects on NPY, POMC and ghrelin expression.展开更多
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. Metho...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.展开更多
基金sponsored by the National Natural Sci-ence Foundation of China (30471248)
文摘Orexin has several biological functions, including the regulation of reproductive endocrine signaling, which has received much attention. However, little is known about the mechanism through which orexin regulates the levels of neuroendocrine hormones and peptides. We injected orexin A or physiological saline into the lateral ventricle of 10 ovariectomized （OVX） gilts, and determined the subsequent changes in serum luteinizing hormone （LH） concentration by using radioimmunoassay （RIA）. We also examined the expression of GnRH, NPY, and POMC mRNAs in the hypothalamus and that of LH, folliclestimulating hormone （FSH）, POMC, and ghrelin mRNAs in the pituitary by using semi-quantitative reverse transcription polymerase chain reaction. We found the following results： （1） Orexin A transiently promoted LH secretion; serum LH concentration started to increase at 10 min after the orexin injection, peaked at 30 min, and returned to its initial level at 1.5 h; （2） orexin A upregulated GnRH mRNA expression and downregulated NPY and POMC mRNAs expression in the hypothalamus; （3） orexin A upregulated LH and FSH mRNAs expression （FSH, P〉 0.05）, but downregulated ghrelin mRNA expression in the pituitary. No significant effects were observed on the pituitary expression of FSH and POMC mRNAs. Our data suggest that orexin A regulates reproductive function by stimulating GnRH and LH release directly and indirectly via its effects on NPY, POMC and ghrelin expression.
基金Supported by Important FinancialIssueof Shi-Wu Programming Key Problem in Liaoning Provinceand Financial Issue for Scientific Research in the Department of Education.
文摘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.
