Insulin resistance and compensation in laminitis-predisposed ponies characterized by the Minimal Model

Abstract

Glucose metabolism in Welsh and Dartmoor ponies and ponies disposed to pasture laminitis was characterized using the Minimal Model of glucose and insulin dynamics. Laminitis-disposed ponies were selected based on farm records of previous disease incidence and nonparallel hoof-lines. All ponies were maintained on pasture and in early March each underwent a frequent sampling intravenous (iv) glucose tolerance test which involved a bolus of 300 mg/kg glucose followed 20 min later by an iv bolus of 20 mlU/kg insulin. Sampling began just prior to the glucose dose and continued for 4 h. Glucose and insulin curves were modeled to determine insulin sensitivity, glucose effectiveness, acute insulin response to glucose and disposition index. Ponies with previous incidents of laminitis were less insulin sensitive and demonstrated compensatory insulin hypersecretion compared to ponies not at risk. Management of at-risk ponies to avoid insulin resistance and triggers for insulin secretion could reduce the likelihood of developing clinical laminitis.