High molecular weight adiponectin as an adjunct biomarker for insulin dysregulation in equids.

BACKGROUND: Total adiponectin concentration is associated with hyperinsulinemia and laminitis risk in ponies but the high molecular weight (HMW) multimer is a more sensitive indicator of metabolic disease in other species and could be a useful biomarker for insulin dysregulation (ID). HYPOTHESIS/OBJECTIVES: To determine a cut-off value for using HMW adiponectin as an adjunct diagnostic tool for ID. ANIMALS: Cohort of 127 privately and university-owned horses and ponies of various breeds with 55 classified as ID positive and 72 as ID negative. METHODS: Cohort study. Baseline and postprandial blood samples from an in-feed oral glucose test (0.75 g/kg dextrose) were used to determine ID status. Insulin and HMW adiponectin concentrations were measured using validated immunoassays. High molecular weight adiponectin cut-off values were derived with receiver-operator characteristic curve analysis using a bootstrap method to maximize the sum of sensitivity and specificity. RESULTS: Median [IQR] HMW adiponectin concentration was higher (P < .001) in ID negative animals (4.19 [2-6.5] μg/mL) compared to ID positive animals (1.79 [0.63-3.5] μg/mL), with a cut-off value (95% CI) of 2.1 (1.26, 3.15) μg/mL (area under the curve 0.71; sensitivity 0.62; and specificity 0.74). Horses had higher (P < .001) HMW adiponectin concentrations (4.38 [2.22-7.3] μg/mL) than ponies (1.84 [0.64-3.75] μg/mL). However, HMW adiponectin did not differ between horses with and without ID, and both horse subgroups had concentrations higher (P ≤ .002) than ponies with ID. CONCLUSIONS AND CLINICAL IMPORTANCE: Use of a single cut-off value for HMW adiponectin as an adjunct biomarker for ID for both horses and ponies is not accurate.