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

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).

To determine a cut-off value for using HMW adiponectin as an adjunct diagnostic tool for ID.

Cohort of 127 privately and university-owned horses and ponies of various breeds with 55 classified as ID positive and 72 as ID negative.

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.

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.

Use of a single cut-off value for HMW adiponectin as an adjunct biomarker for ID for both horses and ponies is not accurate.