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A major role for perifornical orexin neurons in the control of glucose metabolism in rats.
Diabetes 58, 1998-2005 (2009)
OBJECTIVE: The hypothalamic neuropeptide orexin influences (feeding) behavior as well as energy metabolism. Administration of exogenous orexin-A into the brain has been shown to increase both food intake and blood glucose levels. In the present study, we investigated the role of endogenous hypothalamic orexin release in glucose homeostasis in rats. RESEARCH DESIGN AND METHODS: We investigated the effects of the hypothalamic orexin system on basal endogenous glucose production (EGP) as well as on hepatic and peripheral insulin sensitivity by changing orexinergic activity in the hypothalamus combined with hepatic sympathetic or parasympathetic denervation, two-step hyperinsulinemic-euglycemic clamps, immunohistochemistry, and RT-PCR studies. RESULTS: Hypothalamic disinhibition of neuronal activity by the gamma-aminobutyric acid receptor antagonist bicuculline (BIC) increased basal EGP, especially when BIC was administered in the perifornical area where orexin-containing neurons but not melanocortin-concentrating hormone-containing neurons were activated. The increased BIC-induced EGP was largely prevented by intracerebroventricular pretreatment with the orexin-1 receptor antagonist. Intracerebroventricular administration of orexin-A itself caused an increase in plasma glucose and prevented the daytime decrease of EGP. The stimulatory effect of intracerebroventricular orexin-A on EGP was prevented by hepatic sympathetic denervation. Plasma insulin clamped at two or six times the basal levels did not counteract the stimulatory effect of perifornical BIC on EGP, indicating hepatic insulin resistance. RT-PCR showed that stimulation of orexin neurons increased the expression of hepatic glucoregulatory enzymes. CONCLUSIONS: Hypothalamic orexin plays an important role in EGP, most likely by changing the hypothalamic output to the autonomic nervous system. Disturbance of this pathway may result in unbalanced glucose homeostasis.
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Publication type
Article: Journal article
Document type
Scientific Article
Language
english
Publication Year
2009
HGF-reported in Year
0
ISSN (print) / ISBN
0012-1797
e-ISSN
1939-327X
Journal
Diabetes
Quellenangaben
Volume: 58,
Issue: 9,
Pages: 1998-2005
Publisher
American Diabetes Association
Publishing Place
Alexandria, VA.
Reviewing status
Peer reviewed
Institute(s)
Institute of Diabetes and Obesity (IDO)
PubMed ID
19592616
WOS ID
000269650400009
Erfassungsdatum
2009-06-10