A new spontaneously diabetic strain of the Sprague-Dawley rat was established in 1997 and named
the SDT (Spontaneously Diabetic Torii) rat. In this
research, we investigated the characteristics of the
disease condition in the SDT rats. The time of onset
of glucosuria was different between male and
female SDT rats; glucosuria appeared at approximately
20 weeks of age in male rats and at approximately
45 weeks of age in female rats. A cumulative
incidence of diabetes of 100% was noted by 40
weeks of age in male rats, while it was only 33.3%
even by 65 weeks of age in female rats. The survival
rate up to 65 weeks of age was 92.9% in male
rats and 97.4% in female rats. Glucose intolerance
was observed in male rats from 16 weeks of age.
The clinical characteristics of the male SDT rats
were (1) hyperglycemia and hypoinsulinemia (from
25 weeks of age); (2) long-term survival without insulin
treatment; (3) hypertriglyceridemia (by 35
weeks of age); however, no obesity was noted in
any of the male rats. The histopathological characteristics
of the male rats with diabetes mellitus
(DM) were (1) fibrosis of the pancreatic islets (by
25 weeks of age); (2) cataract (by 40 weeks of age);
(3) tractional retinal detachment with fibrous proliferation
(by 70 weeks of age) and (4) massive hemorrhaging
in the anterior chamber (by 77 weeks of age).
These clinical and histopathological characteristics
of the disease in SDT rats resemble those of human
Type 2 diabetes with insulin hyposecretion. In conclusion,
SDT rat is considered to be a potentially
useful model for studies of diabetic retinopathy
encountered in humans.
It is suggested that maxacalcitol attenuates the progression of diabetic nephropathy by suppression of oxidative stress and amelioration of the Nrf2-Keap1 pathway in nonobese type 2 diabetes without significant changes in blood pressure and glomerular filtration rate.
We overviewed the pathophysiological features of diabetes and its complications in obese
type 2 diabetic rat models: Otsuka Long-Evans Tokushima fatty (OLETF) rat, Wistar fatty
rat, Zucker diabetic fatty (ZDF) rat and Spontaneously diabetic Torii (SDT) fatty rat.
Pancreatic changes with progression of diabetes were classified into early changes, such
as islet hypertrophy and degranulation of β cells, and degenerative changes, such as islet
atrophy and fibrosis of islet with infiltration of inflammatory cells. Renal lesions in
tubuli and glomeruli were observed, and nodular lesions in glomeruli were notable changes
in OLETF and SDT fatty rats. Among retinal changes, folding and thickening were
interesting findings in SDT fatty rats. A decrease of motor nerve conduction velocity with
progression of diabetes was presented in obese diabetic rats. Other diabetic
complications, osteoporosis and sexual dysfunction, were also observed. Observation of
bone metabolic abnormalities, including decrease of osteogenesis and bone mineral density,
and sexual dysfunction, including hypotestosteronemia and erectile dysfunction, in obese
type 2 diabetic rats have been reported.
Large retinal folds mimicking tractional retinal detachment with extensive leakage of fluorescein around the optic disk was the most prominent finding of DR in SDT rats.
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