20 Can a common cereal grain be used to help indicate the presence of insulin dysregulation

Abstract

Equine insulin dysregulation (ID) comprises a combination of basal and/or postprandial hyperinsulinemia and/or tissue insulin resistance. ID increases the risk of hyperinsulinemia-associated laminitis (HAL) and equids with ID need to be managed appropriately with a low non-structural carbohydrate (NSC) diet. Diagnosis is therefore crucial. The oral sugar test (OST) or the oral glucose test are currently the recommended practical diagnostic tests for basal and post prandial hyperinsulinemia. The Karo syrup orally administered in the OST is not available in all countries and glucose powder added to feed is not accepted by all equids. Recent work has shown ID animals have an augmented response to small amounts of even moderate NSC feedstuffs. This study evaluated the potential to use this response as a possible alternative indicator of ID status. The postprandial insulin responses to small amounts of the cereal grain, dehulled oats (DO, no further processing), were therefore evaluated in healthy (non-insulin dysregulated; NID) and ID horses (categorized by their results to an OST, 0.15 mL/kg BW). Twelve non-insulin dysregulated (573.2 + 59.9 kg; 16.1 + 3.6 yrs.) and 18 ID horses (594.7 + 93.3 kg; 15.2 + 2.6 yrs.) from 2 separate studies were examined. Horses were grain fasted and blood was collected via jugular venipuncture before (T0)offering DO (1.25 kg/BW study 1, S1; 1.0 kg/BW study 2, S2) and 60-min postprandially (T60). Insulin was analyzed by RIA and delta insulins were calculated (T60-T0). Statistics were analyzed on GraphPad 9.4.0 using ANOVA and Tukey post-hoc. Significance taken as P < 0.05. NID horses’ showed no significant change (P = 0.8) from basal insulin levels following both the DO and the OST (∼8 μIU/mL delta insulin). The ID horses showed a similar augmented mean insulin response to both the DO and the OST which was significantly higher than the NID response (P < 0.05). There was, however, more individual variation in the response to the DO than to the OST (T60 mean + SD [delta insulin]: S1–140.1 + 45.5 [82.0 + 10.1] μIU/mL OST, 170.4 + 92.1 [100.6 + 21.7] μIU/mL DO; S2–123.9 + 37.0 [76.0 + 11.3] μIU/mL OST, 158.6 + 64.4 [98.7 + 19.2] μIU/mL DO). The work suggests that feeding 1g/kg BW of DO might be a possible alternative method of identifying an ID animal when the currently recommended methods are not possible. However, more work is needed to define indicative cutoffs and to evaluate the individual variability.