P21: Unique histopathological characteristics of diabetic ocular lesions in both sexes of the Spontaneously Diabetic Torii (SDT) rat

Abstract

The Spontaneously Diabetic Torii (SDT) rat is a novel rat model recently established for type 2 diabetes mellitus. The rats develop hyperglycemia (non-fasting plasma glucose level in males at 25 weeks: about 700 mg/dL) but can survive for long period of time without insulin therapy. The onset of diabetes is as early as 15 weeks of age in males and 40 weeks in females. The cumulative incidence of diabetes reaches 100% by 40 weeks of age in males, however, only 33% of female SDT rats develop diabetes by 65 weeks of age. To elucidate the histopathologic characteristics of the diabetic ocular lesions and the gender difference of the lesions, eyes of various ages from 23 SDT rats (twelve males of 39–70 weeks, mean, 63 weeks; eleven females 60–82 weeks, mean, 67 weeks) kept without any treatment were examined. Histopathologically, severe diabetic ocular lesions including cataracts (total incidence, 23/23:100%), rapture of the lens (57%), posterior vitreous detachment (83%), proliferative retinopathy (57%), tractional retinal detachment (74%) and iris neovascularization (83%) were observed in both sexes. In one case of 64-week-old male, a massive anterior chamber hemorrhage was observed. The onset of diabetes is about 6 months later in females, however, the diabetic ocular lesions were similar in females and males at ages over 60 weeks. Female SDT rats suffered from impaired glucose tolerance (IGT) as early as 25 weeks of age and over a long period of time of IGT in females may relate to the progressive development of the lesions. In conclusion, SDT rats of both sexes can develop similar ocular complications, which closely mimic morphologically those reported in diabetic patients. The SDT rats represent the first animal model for diabetic ocular complications.