Brain Insulin Action Regulates Hypothalamic Glucose Sensing and the Counterregulatory Response to Hypoglycemia
| Autor: | Dorit Daphna-Iken, Vanessa H. Routh, Zhentao Song, Kelly A. Diggs-Andrews, Simon J. Fisher, Xuezhao Zhang |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2010 |
| Předmět: |
0303 health sciences
medicine.medical_specialty biology Glucokinase Endocrinology Diabetes and Metabolism Insulin medicine.medical_treatment Glucose uptake Central nervous system 030209 endocrinology & metabolism Hypoglycemia medicine.disease Pathophysiology 03 medical and health sciences Insulin receptor 0302 clinical medicine Endocrinology medicine.anatomical_structure Hypothalamus Internal medicine Internal Medicine medicine biology.protein Pancreatic hormone 030304 developmental biology |
| Zdroj: | Diabetes |
| ISSN: | 1939-327X 0012-1797 |
| Popis: | OBJECTIVE An impaired ability to sense and appropriately respond to insulin-induced hypoglycemia is a common and serious complication faced by insulin-treated diabetic patients. This study tests the hypothesis that insulin acts directly in the brain to regulate critical glucose-sensing neurons in the hypothalamus to mediate the counterregulatory response to hypoglycemia. RESEARCH DESIGN AND METHODS To delineate insulin actions in the brain, neuron-specific insulin receptor knockout (NIRKO) mice and littermate controls were subjected to graded hypoglycemic (100, 70, 50, and 30 mg/dl) hyperinsulinemic (20 mU/kg/min) clamps and nonhypoglycemic stressors (e.g., restraint, heat). Subsequently, counterregulatory responses, hypothalamic neuronal activation (with transcriptional marker c-fos), and regional brain glucose uptake (via 14C-2deoxyglucose autoradiography) were measured. Additionally, electrophysiological activity of individual glucose-inhibited neurons and hypothalamic glucose sensing protein expression (GLUTs, glucokinase) were measured. RESULTS NIRKO mice revealed a glycemia-dependent impairment in the sympathoadrenal response to hypoglycemia and demonstrated markedly reduced (3-fold) hypothalamic c-fos activation in response to hypoglycemia but not other stressors. Glucose-inhibited neurons in the ventromedial hypothalamus of NIRKO mice displayed significantly blunted glucose responsiveness (membrane potential and input resistance responses were blunted 66 and 80%, respectively). Further, hypothalamic expression of the insulin-responsive GLUT 4, but not glucokinase, was reduced by 30% in NIRKO mice while regional brain glucose uptake remained unaltered. CONCLUSIONS Chronically, insulin acts in the brain to regulate the counterregulatory response to hypoglycemia by directly altering glucose sensing in hypothalamic neurons and shifting the glycemic levels necessary to elicit a normal sympathoadrenal response. |
| Databáze: | OpenAIRE |
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