A Major Role for Perifornical Orexin Neurons in the Control of Glucose Metabolism in Rats

  1. Chun-Xia Yi1,
  2. Mireille J. Serlie2,
  3. Mariette T. Ackermans3,
  4. Ewout Foppen1,2,
  5. Ruud M. Buijs4,
  6. Hans P. Sauerwein2,
  7. Eric Fliers2 and
  8. Andries Kalsbeek1,2
  1. 1Department of Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Amsterdam, the Netherlands;
  2. 2Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands;
  3. 3Department of Clinical Chemistry, Laboratory of Endocrinology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands;
  4. 4Instituto de Investigaciones Biomedicas Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico City, Mexico.
  1. Corresponding author: Chun-Xia Yi, c.yi{at}nin.knaw.nl.

Abstract

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 γ-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.

Footnotes

  • The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

    • Received March 13, 2009.
    • Accepted June 9, 2009.
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  1. Diabetes vol. 58 no. 9 1998-2005
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