Renal lesions in leptin receptor-deficient medaka (Oryzias latipes)

The aim of this study was to elucidate the renal lesions of leptin receptor-deficient medaka showing hyperglycemia and hypoinsulinemia and to evaluate the usefulness of the medaka as a model of diabetic nephropathy. Leptin receptor-deficient medaka at 20 and 30 weeks of age showed hyperglycemia and hypoinsulinemia; they also showed a higher level of plasma creatinine than the control medaka. Histopathologically, dilation of glomerular capillary lumina and of afferent/efferent arterioles was observed in leptin receptor-deficient medaka at 20 weeks of age, and then glomerular enlargement with cell proliferation and matrix expansion, formation of fibrin cap-like lesions, glomerular atrophy with Bowman’s capsule dilation, and renal tubule dilation were observed at 30 weeks of age. These histopathological characteristics of leptin receptor-deficient medaka were similar to the characteristics of kidney lesions of human and rodent models of type II diabetes mellitus, making leptin receptor-deficient medaka a useful model of diabetic nephropathy.

The spontaneously diabetic torii rat: an animal model of nonobese type 2 diabetes with severe diabetic complications

The Spontaneously Diabetic Torii (SDT) rat is an inbred strain of Sprague-Dawley rat and recently is established as a nonobese model of type 2 diabetes (T2D). Male SDT rats show high plasma glucose levels (over 700 mg/dL) by 20 weeks. Male SDT rats show pancreatic islet histopathology, including hemorrhage in pancreatic islets and inflammatory cell infiltration with fibroblasts. Prior to the onset of diabetes, glucose intolerance with hypoinsulinemia is also observed. As a result of chronic severe hyperglycemia, the SDT rats develop profound complications. In eyes, retinopathy, cataract, and neovascular glaucoma are observed. Proliferative retinopathy, especially, resulting from retinal neovascular vessels is a unique characteristic of this model. In kidney, mesangial proliferation and nodular lesion are observed. Both peripheral neuropathy such as decreased nerve conduction velocity and thermal hypoalgesia and autonomic neuropathy such as diabetic diarrhea and voiding dysfunction have been reported. Osteoporosis is another complication characterized in SDT rat. Decreased bone density and low-turnover bone lesions are observed. Taking advantage of these features, SDT rat has been used for evaluating antidiabetic drugs and drugs/gene therapy for diabetic complications. In conclusion, the SDT rat is potentially a useful T2D model for studies on pathogenesis and treatment of diabetic complications in humans.

Pathophysiological characteristics of diabetic ocular complications in spontaneously diabetic torii rat

The Spontaneously Diabetic Torii (SDT) rat, a nonobese type 2 diabetes model, develops severe diabetic retinopathy as result of chronic severe hyperglycemia. Although existing diabetes animal models also develop ocular complications, severe retinal lesions frequently observed in human diabetes patients such as preretinal neovascularization or retinal detachment are not found. Distinctive features in SDT rat are hypermature cataract, tractional retinal detachment with fibrous proliferation, and massive hemorrhaging in the anterior chamber. These pathophysiological changes are caused by sustained hyperglycemic condition and subsequent increased expression of vascular endothelial growth factor (VEGF) in retina, iris, and ciliary body. Although some differences in diabetic retinopathy exist between SDT rats and humans (e.g., a low incidence of neovascular formation and poor development of nonperfused area are found in this animal), SDT rat will be a useful model in studies of the pathogenesis and treatment of diabetic retinopathy.