Preventive effects of pioglitazone on diabetes and relevant mechanisms, experimental study on non-obese diabetic mice

Objective To explore the effects of pioglitazone on insulitis and diabetes and relevant mechanism. Methods Seventy-three female non-obese diabetic (NOD)/Lt mice aged 4 weeks were randomly divided into 3 groups, control group (n=25, fed with regular diet), low dosage pioglitazone group (n=23, pioglitazone of the concentration of 0.01% was added into the feed) and high dosage pioglitazone group (n=25, pioglitazone of the concentration of 0.04% was added into the feed). The mice were killed when diabetes developed or they reached the age of 30 weeks. The body weight and amount of food intake were measured every week and the amount of drug intake was calculated. Urine glucose was checked weekly from week 10 to week 30. When urine glucose was positive and relevant symptoms appeared, blood glucose was measured. The criterion of diagnosis of diabetes was the consecutive blood glucose level ≥16.7 mmol/L for 2 times. At the 12th week 4～7 mice from the 3 groups respectively were killed and their pancreases were removed to be scored on insulitis by HE staining, the spleen cells were cultured. The IL-4 and IFN-r levels in serum and supernatants of spleen cell cultures were measured by ELISA. The pancreatic IFN-r mRNA level was tested using RT-PCR method. Results (1)At the age of 30 weeks, the diabetes incidence rates was 80%(20/25) in the control group, 60.9% (14/23) in the low dose group, and 60% (15/25) in the high dose group (P0.05). At the following time points the diabetes incidence rates of the 2 treated groups were lower than that of the control group (all P0.05): ①0% in the low dose group vs 16% : of the control group at the age of 100 days, and 39% vs 68% at the age of 185 days; and ② 0% in the high dose group vs 16% in the control group at the age of 110 days, 4% vs 24% at the age of 120 days, and 12%vs 36% at the age of 135 days. (2)There was no difference in insulitis scores between the control group and low dose or high dose groups at the age of 12 weeks (1.99±0.75 vs 1.01±0.68 and 1.19±0.84, both P0.05) , however, the score of the combined pioglitazone group (low dose group + high dos group) was significantly higher than that of the control group (1.12±0.75 vs 1.99±0.75, P0.05). (3)There was no differences in the IL-4/IFN- r ratios in serum and splenocyte culture supernatant and pancreatic IFN-r mRNA levels among the three groups (all P0.05). Conclusion Pioglitazone, to some extent, lessens the insulitis severity and delays the diabetes onset. Its mechanism may be unrelated to immune deviation of Th1 to a Th2.