HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: db07-1329v1 57/2/470    most recent Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Google Scholar Articles by Arbelaez, A. M. Articles by Cryer, P. E. PubMed PubMed Citation Articles by Arbelaez, A. M. Articles by Cryer, P. E. Social Bookmarking                What's this?

Attenuation of Counterregulatory Responses to Recurrent Hypoglycemia by Active Thalamic Inhibition

A Mechanism for Hypoglycemia-Associated Autonomic Failure

¹ Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri
² Departments of Neurology and Radiology, Washington University School of Medicine, St. Louis, Missouri
³ Department of Neurological Surgery, Washington University School of Medicine, St. Louis, Missouri
⁴ Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, North Carolina
⁵ Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri
⁶ Department of Medicine, Washington University School of Medicine, St. Louis, Missouri

Address correspondence and reprint requests to Philip E. Cryer, MD, Campus box 8127, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, MO 63110. E-mail: pcryer{at}wustl.edu

Abbreviations: CBF, cerebral blood flow; HAAF, hypoglycemia-associated autonomic failure; PET, positron emission tomography; PVNT, paraventricular nucleus of the thalamus

OBJECTIVE—Hypoglycemia, the limiting factor in the glycemic management of diabetes, is the result of the interplay of therapeutic insulin excess and compromised glycemic defenses. The key feature of the latter is an attenuated sympathoadrenal response to hypoglycemia that typically follows an episode of recent antecedent iatrogenic hypoglycemia, a phenomenon termed hypoglycemia-associated autonomic failure (HAAF) in diabetes. We investigated the role of cerebral mechanisms in HAAF by measuring regional brain activation during recurrent hypoglycemia with attenuated counterregulatory responses and comparing it with initial hypoglycemia in healthy individuals.

RESEARCH DESIGN AND METHODS—We used [¹⁵O]water and positron emission tomography to measure regional cerebral blood flow as a marker of brain synaptic activity during hyperinsulinemic hypoglycemic clamps (55 mg/dl [3.0 mmol/l]) in the naïve condition (day 1) and after 24 h of interval interprandial hypoglycemia (day 2) in nine healthy adults.

RESULTS—Interval hypoglycemia produced attenuated sympathoadrenal, symptomatic, and other counterregulatory responses to hypoglycemia on day 2, a model of HAAF. Synaptic activity in the dorsal midline thalamus during hypoglycemia was significantly greater on day 2 than day 1 (P = 0.004).

CONCLUSIONS—Greater synaptic activity associated with attenuated counterregulatory responses indicates that the dorsal midline thalamus plays an active inhibitory role in reducing sympathoadrenal and symptomatic responses to hypoglycemia when previous hypoglycemia has occurred, the key feature of HAAF in diabetes.

CiteULike    Del.icio.us    Digg    Reddit    Technorati    What's this?