Investigating the relationship between cardiac function and insulin sensitivity in horses

Abstract

Metabolic syndrome in humans is commonly associated with cardiovascular dysfunction, including atrial fibrillation and left ventricular diastolic dysfunction. Although many differences exist between human and equine metabolic syndrome, both of these conditions share some degree of insulin resistance. The aims of this study were to investigate the relationship between magnitude of insulin resistance and degree of myocardial dysfunction. Seven horses (five mares, two geldings, age 17.2 +/= 4.2 years, weight 524 +/= 73 kg) underwent insulin-modified frequently sampled intravenous glucose tolerance testing to determine insulin sensitivity (mean 2.21 +/= L/min/mU). Standard echocardiograms were performed on each horse, including two-dimensional, M-mode, and pulse-wave tissue Doppler imaging. Data were assessed for normality by constructing normal probability plots and performing the Shapiro-Wilks test. Pearson and Spearman correlation analysis was used to determine the association of insulin sensitivity with echocardiographic measures of cardiac function. Insulin sensitivity was found to be significantly correlated with peak myocardial velocity during late diastole (r = 0.89, p = 0.0419), ratio between peak myocardial velocity in early and late diastole (r = -0.92, p = 0.0263), isovolumetric relaxation time (r = -0.97, p = 0.0072), and isovolumetric contraction time (p^2 = -0.90, p = 0.0374). Due to the small sample size of this study, the relationship between insulin sensitivity and myocardial function requires further investigation.