Author contributions. The initiation, conception and planning for this study were by F.T., N.F., R.J.G. and R.C.B. Its execution was by F.T., N.F., S.B.E., K.P. and R.C.B., with statistics by F.T. and N.F. The paper was written by F.T., N.F. and R.C.B.
Optimisation of the frequently sampled intravenous glucose tolerance test to reduce urinary glucose spilling in horses
Article first published online: 5 JAN 2010
2009 EVJ Ltd
Equine Veterinary Journal
Volume 41, Issue 9, pages 844–851, December 2009
How to Cite
TÓTH, F., FRANK, N., ELLIOTT, S. B., PERDUE, K., GEOR, R. J. and BOSTON, R. C. (2009), Optimisation of the frequently sampled intravenous glucose tolerance test to reduce urinary glucose spilling in horses. Equine Veterinary Journal, 41: 844–851. doi: 10.2746/042516409X439661
- Issue published online: 5 JAN 2010
- Article first published online: 5 JAN 2010
- Paper received for publication 19.01.09; Accepted 18.03.09
- insulin resistance;
- minimal model;
Reasons for performing study: The frequently sampled i.v. glucose tolerance test (FSIGTT) is used to evaluate glucose and insulin dynamics in horses, but it has not been determined whether urinary glucose spilling (UGS) affects results.
Hypothesis: UGS occurs in horses during the FSIGTT and this problem can be minimised by adjusting the dextrose and insulin dosages used.
Methods: Six mature mares were included in this study. In the first phase, 6 FSIGTT procedures were performed in each horse to evaluate 6 different dextrose dosages. Six different insulin dosages were evaluated during the second phase of the study after administration of 300 mg/kg bwt dextrose. Area under the glucose (AUCg) and insulin (AUCi) curves were calculated and minimal model analyses performed. UGS was measured in the third and fourth phases of the study during the combined glucose insulin test and established FSIGTT. A new FSIGTT was developed and evaluated.
Results: Positive linear effects of dextrose dosage on AUCg, AUCi and acute insulin response to glucose were detected, with AUCg reaching a plateau at doses 200 mg/kg bwt. Insulin dosage had an inverse linear effect on AUCg, but other values remained unaffected. UGS occurred during all 3 tests and was the highest for the established FSIGTT and the lowest for the new FSIGTT. The type of FSIGTT performed did not affect minimal model results.
Conclusions: Results indicate that the dextrose dosage of 300 mg/kg bwt used in the established FSIGTT is too high. UGS can be reduced by lowering the dextrose dosage to 100 mg/kg bwt.
Potential relevance: A new FSIGTT involving the administration of 100 mg/kg bwt dextrose followed by 20 mu/kg bwt insulin 20 min later is recommended for use in horses because this test provides adequate data for minimal model analysis while minimising UGS.