The intravenous glucose tolerance test in cannulated Wistar rats: a robust method for the in vivo assessment of glucose-stimulated insulin secretion.
BACKGROUND
Glucose-stimulated insulin secretion (GSIS) is critical in mammalian fuel homeostasis and is diminished early in the evolution of beta-cell dysfunction, ultimately contributing to the development of Type 2 diabetes. We sought to standardise and validate the intravenous glucose tolerance test (IVGTT), a commonly used technique to assess GSIS, in anaesthetised and conscious cannulated male Han Wistar rats.


METHODS
Male Han Wistar rats were cannulated via the right jugular vein and left carotid artery. Anaesthetised and chronically cannulated conscious models underwent IVGTT using increasing doses of glucose (0.2, 0.5 and 1.0 g glucose/kg LBM) or following pre-treatment with Exendin-4 (EX-4) before receiving a 0.5 g glucose/kg LBM bolus dose. Blood glucose, plasma insulin and plasma C-peptide were measured at time-points throughout the experiments.


RESULTS
Dose-dependent increases in blood glucose, insulin and C-peptide (where measured) were observed following administration of increasing doses of an intravenous glucose bolus in both the anaesthetised and conscious cannulated rats. The 0.5 g glucose/kg LBM bolus resulted in an intermediate response and was used in the second part of the study. EX-4 pre-treatment in combination with glucose resulted in GSIS potentiation, as assessed by plasma insulin measurement alone (anaesthetised model) or insulin and C-peptide measurements (conscious model).


CONCLUSIONS
The IVGTT was standardised in anaesthetised and conscious cannulated male Han Wistar rats by performing a glucose dose response study and validated by examining GSIS potentiation using EX-4. Based on these results, the 0.5 g glucose/kg LBM bolus dose is recommended as the dose to use to assess GSIS in any standardised screening phase of new compounds with the potential to enhance glucose-sensitive pancreatic function. The experimental conditions described in these studies could be transferred to disease models for more detailed assessment of novel compound efficacy.
Frangioudakis
Georgia
G
Cardiovascular and Gastrointestinal Discovery Department, AstraZeneca Pharmaceuticals, Alderley Park, Macclesfield, Cheshire, United Kingdom.
Gyte
Amie C
AC
Loxham
Susan J G
SJ
Poucher
Simon M
SM
D000704:Analysis of Variance; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D002096:C-Peptide / Q000097:blood / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D000077270:Exenatide; D005947:Glucose; D005951:Glucose Tolerance Test / Q000379:methods*; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007275:Injections, Intravenous; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014688:Venoms / Q000494:pharmacology
D001786:Blood Glucose; D002096:C-Peptide; D007004:Hypoglycemic Agents; D007328:Insulin; D010455:Peptides; D014688:Venoms; D000077270:Exenatide; D005947:Glucose