Preventive effects of glycaemic control on ocular complications of Spontaneously Diabetic Torii rat.

Aim:  Spontaneously Diabetic Torii (SDT) rat is a new model of non-obese type 2 diabetes. SDT rats show severe ocular complications such as cataracts, tractional retinal detachment with fibrous proliferation and massive haemorrhaging in the anterior chamber. In the present study, blood glucose levels of SDT rats were controlled in order to examine whether these ocular complications are caused by hyperglycaemia. Methods:  SDT rats were treated with an insulin implant to control blood glucose. To evaluate retinal function, we used electroretinograms (ERG) and measured vascular endothelial growth factor (VEGF) concentrations within the aqueous humour. Finally, we studied retinal flat-mounts and trypsin digestion to evaluate vascular abnormalities in SDT rats. Results:  Forty-four-week-old SDT rats displayed an increase in VEGF concentrations within the aqueous humour and significant prolongation of the peak latencies in ERG (Σ(OP1–OP4); Sprague–Dawley (SD): 146.2 ± 1.06 ms; SDT: 166.3 ± 2.38 ms; SDT + insulin: 149.2 ± 1.83 ms). Retinal flat-mounts of SDT rats showed venous dilation and meandering vascular networks. Furthermore, acellular capillaries were observed in the retinal trypsin digestion. Insulin treatment prevented these ocular abnormalities in SDT rats. Conclusions:  These findings indicate that ocular complications of SDT rats are caused by hyperglycaemia. The features of SDT rats indicate their usefulness for the future study of diabetic retinopathy.