Risk Factors for Retinopathy in Spontaneously-Diabetic Monkeys

Abstract

Abstract: : Purpose: Rhesus monkeys spontaneously develop type 2 diabetes, with complications similar or identical to those seen in humans. One important advantage to studying these animals is that systemic factors that naturally contribute to pathology in this disease can be evaluated. The purpose of this study is to determine systemic risk factors for developing diabetic choroidopathy and retinopathy. Methods: Histology and immunohistochemistry (using ADPase and anti-HSPG to stain viable retinal and choroidal vasculatures, respectively) were performed on the eyes of 14 diabetic monkeys that were electively euthanized because of failing health. Systemic data had been collected periodically on all animals, 13 out of 14 which developed diabetes while members of the colony. Data reported here were obtained while all monkeys were relatively healthy, i.e. prior to or at the onset of weight loss. Results: 8 monkeys had evidence of diabetic retinopathy, including microaneurysms, cotton wool spots, venous pruning, intraretinal hemorrhages, IRMA, and retinal capillary dropout. 6 had no retinopathy. Monkeys that developed retinopathy had more severe diabetes than the animals without retinopathy; i.e. higher fasting plasma glucose levels (p = 0.015, t-test) and lower glucose clearance rates (p = 0.025, t-test). They had diabetes for longer periods of time (p = 0.012, t-test), but were not older (p = 0.107, t-test). Peak systolic pressure (p = 0.035, t-test), cholesterol (p = 0.026, Mann-Whitney U test) and triglycerides (p = 0.026, Mann-Whitney U test) were all higher in animals with retinopathy. Conclusions: Hypertension and high triglyceride and cholesterol levels predict development of retinopathy in spontaneously-diabetic monkeys. Better control of these factors may prevent or delay onset of ocular complications.

Keywords: diabetic retinopathy • animal model • diabetes