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Meal-induced insulin sensitization in conscious and anaesthetized rat models comparing liquid mixed meal with glucose and sucrose

Published online by Cambridge University Press:  08 March 2007

Parissa Sadri ,
Maria A. G. Reid ,
Ricardo A. Afonso ,
Joshua Schafer ,
Dallas J. Legare ,
M. Paula Macedo  and
W. Wayne Lautt
Parissa Sadri
Affiliation:
Department of Pharmacology & Therapeutics, Faculty of Medicine, University of Manitoba, A210 – 753 McDermot Avenue, Winnipeg, Manitoba, CanadaR3E 0T6
Maria A. G. Reid
Affiliation:
Department of Pharmacology & Therapeutics, Faculty of Medicine, University of Manitoba, A210 – 753 McDermot Avenue, Winnipeg, Manitoba, CanadaR3E 0T6
Ricardo A. Afonso
Affiliation:
Departamento de Fisiologia – FCM-UNL, Campo Martires da Patria 130, 1169-056 Lisbon, Portugal
Joshua Schafer
Affiliation:
Department of Pharmacology & Therapeutics, Faculty of Medicine, University of Manitoba, A210 – 753 McDermot Avenue, Winnipeg, Manitoba, CanadaR3E 0T6
Dallas J. Legare
Affiliation:
Department of Pharmacology & Therapeutics, Faculty of Medicine, University of Manitoba, A210 – 753 McDermot Avenue, Winnipeg, Manitoba, CanadaR3E 0T6
M. Paula Macedo
Affiliation:
Departamento de Fisiologia – FCM-UNL, Campo Martires da Patria 130, 1169-056 Lisbon, Portugal
W. Wayne Lautt*
Affiliation:
Department of Pharmacology & Therapeutics, Faculty of Medicine, University of Manitoba, A210 – 753 McDermot Avenue, Winnipeg, Manitoba, CanadaR3E 0T6
*
*Corresponding author: Dr W. Wayne, fax +1 204 975 7784, email [email protected]
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Abstract

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We have recently shown that meal-induced insulin sensitization (MIS) occurs after feeding and decreases progressively to insignificance after 24h of fasting and is caused by action of a hepatic insulin sensitizing substance (HISS). In order to carry out quantitative studies of MIS, some standardized meal intake is required. Our objective was to establish animal models to be tested in both the conscious and anaesthetized state using intragastric injection of liquid meals in order to quantify MIS. Insulin sensitivity was assessed before and 90min after the meal using the rapid insulin sensitivity test (RIST) which is a transient euglycaemic clamp. Rats tested in the conscious state were instrumented under anaesthesia 6–9d prior to testing with catheters in the carotid artery, jugular vein and stomach. Meals, injected into the stomach, consisted of a liquid mixed meal, sucrose, glucose or water. The glucose sequestration in response to insulin increased by 90% and 61% following the liquid mixed meal (10ml/kg) in conscious and anaesthetized rats, respectively. Glucose, sucrose and water did not effectively activate MIS. MIS was completely reversed in the conscious model by atropine and completely prevented from developing in the anaesthetized model that had previously undergone hepatic denervation. Gastric administration of a liquid mixed meal but not glucose or sucrose is capable of activating MIS for purposes of mechanistic studies and quantification of the MIS process. The feeding signal is mediated by the hepatic parasympathetic nerves.

Keywords

HISSRISTInsulin sensitivityMealFeedingSucroseGlucose
Type
Research Article
Information
British Journal of Nutrition , Volume 95 , Issue 2 , February 2006 , pp. 288 - 295
Copyright
Copyright © The Nutrition Society 2006

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