Effect of Isolation Stress on Glucose/Lipid Metabolism in Spontaneously Diabetic Torii (SDT) Fatty Rats

Aim: The Spontaneously Diabetic Torii (SDT) fatty rat is a novel obese type 2 diabetic model, showing hyperphagia, obesity, and diabetes mellitus from a young age. In this study, we investigated the effects of isolation stress on pathophysiology in SDT fatty rats.
Methods: SDT fatty rats (4 weeks old) were housed 3 per cage for 2 weeks and separated as males or females so as each gender will be placed in a separate cage to avoid mating. After acclimatization in 6 weeks of age, the rats were exposed to isolation stress (IS) (one rat per cage, using 5 animals in each sex). In the control group, each sex of experimental rats were housed separately continuously 3 per cage (using 6 animals in each sex). Food intake, body weights, and blood chemical parameters, such as glucose, insulin, triglyceride and total cholesterol levels, of the rats from 6 to 15 weeks of age were measured at every 3 weeks. Satellite groups were prepared for pathological analyses. Necropsy of satellite group was performed at 12 weeks of age, and the pathological analyses, such as adrenal, thymus and spleen, were performed.
Results: The blood glucose level in IS group in female SDT fatty rats was significantly increased at 12 weeks of age as compared with that in control group. Female SDT fatty rats showed accelerated diabetic progression, but the male rats did show the effects of IS on the glucose/lipid metabolism. In male SDT fatty rats, an increase of adrenal weight and a decrease of thymus weight were observed in IS group and the female rats in IS group showed a tendency of an increase of adrenal weight and a decrease of thymus weight. In histopathological analyses, adrenal hypertrophy and thymus atrophy were observed in IS group in both male and female rats.
Conclusion: Isolation stress affected the progression of diabetes in female SDT fatty rats. Housing conditions is a factor to care for in evaluation of pathophysiology in diabetic models.