A modified oral sugar test for evaluation of insulin and glucose dynamics in horses

Abstract

BackgroundAn oral sugar test (OST) using Karo® Light Corn Syrup has been developed in the USA as a field test for the assessment of insulin dysregulation in horses but the syrup is not available in Scandinavian grocery stores. The aim of the study was to compare the results of a modified OST between horses with equine metabolic syndrome (EMS) and healthy horses using a Scandinavian commercially available glucose syrup (Dansukker glykossirap). In addition, the effect of breed and the repeatability of the test were evaluated. In the present study, clinically healthy horses (7 Shetland ponies, 8 Icelandic horses, 8 Standardbred horses) and 20 horses of various breeds with EMS underwent the modified OST test. The Icelandic horses and Shetland ponies underwent the OST twice. Insulin and glucose data from the OST were used to calculate peak insulin concentration (PeakINS), time to peak insulin concentration (T-peakINS), area under the curve for insulin (AUCINS) and glucose (AUCGLU) as well as whole body insulin sensitivity index (ISICOMP).ResultsCompared to the healthy group, the EMS group had 6–7 times higher geometric mean for PeakINS and AUCINS and 8 times lower geometric mean for ISICOMP. The EMS group had a delayed T-peakINS compared to the healthy group. There was no effect of breed in the group of healthy horses on PeakINS, T-peakINS, AUCINS, AUCGLU and ISICOMP. Coefficient of variation for repeated tests was 19.8, 19.0 and 17.6 % for PeakINS, AUCINS and ISICOMP respectively.ConclusionsThe results of the present study demonstrate that the modified OST appears to be a practical and useful diagnostic tool for assessment of insulin dysregulation in the horse. However, to make it possible to establish the most appropriate sampling interval and to evaluate the accuracy of the modified OST, further studies in horses with a variable degree of insulin resistance are needed, where results from the modified OST are compared with quantitative measurements for IS.

The effect of insulin infusion on heart rate and systemic blood pressure in horses with equine metabolic syndrome

“…Privately owned horses from first opinion practice with at least one episode of laminitis (diagnosis based on clinical and lameness examination), general adiposity (body condition score (BCS) ≥7) and/or regional adiposity (cresty neck score (CNS) ≥3.5) and with insulin dysregulation, based on an oral sugar test (OST) , were recruited to the study. The OST was performed in the field and the diagnosis was based on a single blood sample obtained at 60–90 min post sugar administration . If the plasma insulin response was above 80 μIU/mL, plasma ACTH concentrations were within the seasonally adjusted range and there was no ongoing episode of laminitis, the owner was asked to enrol the horse in the study.…”

“…The horses in the EMS group were examined at the University Equine Hospital at the Swedish University of Agricultural Sciences, whereas the control horses were examined at the Equine clinic, at the Swedish Horse Industry Foundation. An additional OST test was performed after the acclimatisation period where serial blood samples were collected after sugar administration . The day after the OST, a euglycaemic hyperinsulinaemic clamp (EHC) was performed.…”

“…The day before the OST, an intravenous catheter was inserted into one of the jugular veins under local anaesthesia . The OST was performed as described previously . Briefly, Dan Sukker Glucossirap was administered orally at a dosage of 0.2 mL/kg body weight.…”

Effect of varying the dose of corn syrup on the insulin and glucose response to the oral sugar test

“…A single dose of 0.15 mL/kg bwt corn syrup (Karo Light Corn Syrup)a for the OST has been used , but limited differing doses have been investigated . Higher doses, which provide amounts of sugar more similar to the oral glucose test, may afford improved diagnostic abilities.…”

Repeatability of the hyperglycaemic clamp for assessment of β‐cell response and insulin sensitivity in horses

“…The OGTT can also be used to assess the β‐cell response in both humans and horses . The different types of oral glucose tolerance tests in horses (OGTT and oral sugar test; OST) have shown low repeatability for indices of β‐cell response . This low repeatability is likely a result of more delayed and inconsistent appearance of glucose in the circulation after oral administration caused by differences in rate of glucose absorption as well as in first‐pass effect of the liver between test occasions .…”