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dc.contributor.advisorLimesand, Sean W.en_US
dc.contributor.authorChen, Xiaochuan
dc.creatorChen, Xiaochuanen_US
dc.date.accessioned2012-08-14T22:18:21Z
dc.date.available2012-08-14T22:18:21Z
dc.date.issued2012
dc.identifier.urihttp://hdl.handle.net/10150/238671
dc.description.abstractPlacental insufficiency-induced intrauterine growth restriction (IUGR) increases risk of mortality and morbidity in newborn infants and domestic animals. IUGR fetuses are typically exposed to prolonged hypoxemia, hypoglycemia, and hypercatecholaminemia, which results in perinatal pancreatic β-cell dysfunction. Recent evidence indicates that chronic exposure to norepinephrine in utero suppresses insulin secretion through α2-adrenergic receptors (ARs), but if the adrenergic actions are blocked compensatory hyper insulin secretion response is observed in the IUGR sheep fetus. In the current studies, we demonstrate that chronic NE exposure alone can produce the compensatory enhancement of β-cell responsiveness following termination of a chronic NE infusion. In the fetus NE was continuously infused at 1-4 μg/min for seven days starting at 131 days of gestational age (term = 145 days). During treatment, NE infused fetuses had higher (P < 0.05) plasma NE concentrations and lower (P < 0.01) insulin concentrations than vehicle infused control fetuses. Glucose stimulated insulin secretion (GSIS), which measures β-cell function, prior to NE treatment was not different between treatments. However, insulin concentrations during hyperglycemic steady state period of GSIS studies and area under the curve of glucose-potentiated arginine-induced insulin secretion were higher (P < 0.01) than control values and this augmentation was confirmed at 3 hours, 24 hours, and five days in NE-infused fetuses after discontinuing the infusion. Pancreatic islets isolated within 10 hours post NE infusion had lower (P < 0.05) mRNA expression of α1D (58%), α2A (43%), α2C (42%), α1 (67%) adrenergic receptors (ARs), and uncoupling protein 2 (40%) compared to islets from controls. Isolated islets from NE-infused fetuses 5 days after NE treatment had lower (P < 0.05) inhibitory responsiveness from NE and a greater (P < 0.05) maximal insulin release with glucose simulation in static incubations compared to controls. These findings show that following chronic NE exposure insulin secretion responsiveness was augmented and was coupled with desensitized adrenergic signaling. Moreover, this compensatory β-cell enhancement persists for days indicating chronic NE exposure permanently alters β-cell responsiveness.
dc.language.isoenen_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.subjectMetabolismen_US
dc.subjectPancreasen_US
dc.subjectPregnancyen_US
dc.subjectType 2 Diabetesen_US
dc.subjectAnimal Sciencesen_US
dc.subjectAdrenergic receptoren_US
dc.subjectFetal programmingen_US
dc.titleChronic Norepinephrine Suppression Induces a Compensatory B-Cell Adaptation that Enhances Insulin Secretion after Alleviation of the Catecholamine Inhibition in Fetal Sheepen_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
thesis.degree.grantorUniversity of Arizonaen_US
thesis.degree.leveldoctoralen_US
dc.contributor.committeememberAllen, Ronald E.en_US
dc.contributor.committeememberCollier, Robert J.en_US
dc.contributor.committeememberGriffin, Kurt J.en_US
dc.contributor.committeememberLynch, Ronald M.en_US
dc.contributor.committeememberLimesand, Sean W.en_US
dc.description.releaseRelease after 20-Apr-2013en_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineAnimal Sciencesen_US
thesis.degree.namePh.D.en_US
refterms.dateFOA2013-04-20T00:00:00Z
html.description.abstractPlacental insufficiency-induced intrauterine growth restriction (IUGR) increases risk of mortality and morbidity in newborn infants and domestic animals. IUGR fetuses are typically exposed to prolonged hypoxemia, hypoglycemia, and hypercatecholaminemia, which results in perinatal pancreatic β-cell dysfunction. Recent evidence indicates that chronic exposure to norepinephrine in utero suppresses insulin secretion through α2-adrenergic receptors (ARs), but if the adrenergic actions are blocked compensatory hyper insulin secretion response is observed in the IUGR sheep fetus. In the current studies, we demonstrate that chronic NE exposure alone can produce the compensatory enhancement of β-cell responsiveness following termination of a chronic NE infusion. In the fetus NE was continuously infused at 1-4 μg/min for seven days starting at 131 days of gestational age (term = 145 days). During treatment, NE infused fetuses had higher (P < 0.05) plasma NE concentrations and lower (P < 0.01) insulin concentrations than vehicle infused control fetuses. Glucose stimulated insulin secretion (GSIS), which measures β-cell function, prior to NE treatment was not different between treatments. However, insulin concentrations during hyperglycemic steady state period of GSIS studies and area under the curve of glucose-potentiated arginine-induced insulin secretion were higher (P < 0.01) than control values and this augmentation was confirmed at 3 hours, 24 hours, and five days in NE-infused fetuses after discontinuing the infusion. Pancreatic islets isolated within 10 hours post NE infusion had lower (P < 0.05) mRNA expression of α1D (58%), α2A (43%), α2C (42%), α1 (67%) adrenergic receptors (ARs), and uncoupling protein 2 (40%) compared to islets from controls. Isolated islets from NE-infused fetuses 5 days after NE treatment had lower (P < 0.05) inhibitory responsiveness from NE and a greater (P < 0.05) maximal insulin release with glucose simulation in static incubations compared to controls. These findings show that following chronic NE exposure insulin secretion responsiveness was augmented and was coupled with desensitized adrenergic signaling. Moreover, this compensatory β-cell enhancement persists for days indicating chronic NE exposure permanently alters β-cell responsiveness.


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