| There are majority of children and young people in Type 1 Diabetes Mellitus, it would be in need of long-term insulin to treat and bring heavy burden to the family and society. Thus to approach the prevention of T1DM and reduce morbidity is a very important issue to be resolved. In present, T1DM is a pancreatic isletβ-cell selective autoimmune disease[2,3] that T-cell-mediated the destructi- on,and the destruction of immune tolerance and Th1/Th2 imbalance is an important link in its incidence[4]. The balance of Th1 cell and Th2 cell is the most important key point of immune modulation and play its role with the secreted cytokines. IFN-γand IL-4 can represent Th1 and Th2 immune response levels[6], and the ratio of IFN-γ/IL-4 represent the immune dynamic equilibrium of Th1/Th2.Vitamin A is an essential micronutrient for human. All- trans-retinoic acid(ATRA)is an active derivatives of vitamin A and the relationship of vitamin A and immunity is important[10]. Sufficient vitamin A can activate Th2 response and reduce Th1 response. Deficiency of Vitamin A broke the balance of Th1/Th2, resulting in the increase of Th1 and the reduction of Th2. In recent years, foreign scholars have indicated that ATRA protect the islet cells side through animal and cell culture experiments [13,14], yet it hasn't been reported in China. ATRA can protect islet cells, but the role of immune mechanism has not been entirely clear.The experiment apply the way of the multiple low dose stre- ptozotocin(STZ) to induce mice model of T1DM, and to investigate the protective effect of islet cells by ATRA and the effect of T1DM morbidity and IFN-γ, IL-4, IFN-γ/ IL - 4 level , and to explore the preventive effect and the immune mechanism of ATRA of T1DM. ICR mice were randomly divided into three groups. 1. Prevention group (n=20): ICR mice were pretreated with ATRA (10mg·kg-1) subcutaneous injection for five consecutive days. Every other day, and then STZ(60mg·kg-1) was given intraperitoneal for 5 consecutive days. 2. Diabetic group (n=20): ICR mice were treated with aseptic mixed solution of 95% opeanut oil and 5% dimethyl sulfoxide subcutaneous injection for 5 consecutive days. Every other day, and then STZ (60mg·kg-1) was given intraperitoneal for 5 consecutive days. 3. normal the control group (n=10): ICR mice were treated with aseptic mixed solution of 95% opeanut oil and 5% dimethyl sulfoxide subcutaneous injection for 5 consecutive days. Every other day, and then citrate buffer was given intraperitoneal for 5 consecutive days. The blood glucose level was monitored every week after injectioning STZ, the mice were considered diabetic when blood glucose level was equal to or above 16.7mmol/L and keep on twice .We observed dynamic the general state of mice and monitored the level blood glucose and body weigh every week. The mice in each group were sacrificed after 6 weeks. The serum was collected and the pancreas were prepared pathology. Radioimmunnity analysis was used to detect the serum insulin level. The level of IFN-γand IL-4 were detected with enzyme linked immunosorbent assay. Data were analyzed by SPSS 11.0 software and paired t-test was used to compare the same group with before and after the treatment and single-factor analysis of variance was used to compare the difference between groups. The exact propability was used to compare the difference between the incidence of diabetes. P<0.05 was regarded to have significant difference. The results showed that the mice of diabetic group to drink more, food more, urine more, weight loss, dull hair, and other activities to reduce and gradually increase. The blood glucose level, IFN-γlevel and the ratio of IFN-γ/ IL-4 increased. Serum insulin level and IL-4 level decreased. The autoimmune insulit is and apoptotic isletsβ-cells could be observed. In the Prevention group, the autoimmune insulit is and diabetes incidence could be prevented in ICR mice, which were administrated of ATRA before streptozotocin treatment. Blood glucose level decreased. Serum insulin level increased. IL-4 level was up regulated, IFN-γand the ratio of IFN-γ/ IL-4 were down regulated. Light microscope showed the morphological isletsβ-cells were close to the normal mice. There were statistical significance compared with diabetic group.1. The multiple low dose streptozotocin(STZ) induce mice model is T1DM model.This study observed that diabetic mice developed symptoms gradually worsened and blood glucose level increased gradually, blood glucose and incidence of increased synchronization process is not unexpected. They reached and stabled a high level until the fourth week. Serum insulin level decreased,to explain from the isletβ-cell metabolism migration to diabetes onset after a longer period of time submerged state of the islet damage occurred is a gradal, progressive increase process. In Islets of the diabetic mice that infiltration of inflammatory cells were observed , some islet cell degeneration, and morphological changes consistent with the pathological features of type 1 diabetes that is non-specific inflammation associated with pancreatic isletβ-cell destroying. IFN-γlevel and the ratio of IFN-γ/ IL-4 increased, IL-4 level decreased, Th1/Th2 imbalance which led to immune response of the Th1 cell-mediated, resulting in pancreaticβ-cell damage, resulting in the occurrence of T1DM, consistent with the domestic and international reports[11,37], consistent with the pathogenesis of human T1DM, and the advantages is an ideal method to prepare the animal model of T1DM. 2. The preventive effect and the immune mechanism of ATRA on T1DM.In this study, the isletβ-cells could be prevented in ICR mice, which were administrated of ATRA before streptozotocin treatment,allowing STZ caused by reduced pancreaticβ-cells to increase in size, shape close to normal, restore insulin secretion, and thus decrease the blood glucose,diabetes not obvious symptoms; STZ-induced delay the onset T1DM mice, the incidence rate decreased. There were statistical significance compared with diabetic group. Clearly, ATRA have the preventive effect on low dose STZ by intraperitoneal injection caused of T1DM[15]. At the same time ATRA regulated IFN-γ/IL-4 imbalance by STZ-induced, IL-4 level was up regulated, IFN-γand the ratio of IFN-γ/IL-4 were down regulated, significantly reduce non-specific STZ-induced pancreatic inflammation, reduced the isletβ-cell damage, which consist with the domestic and international reports[15-16]. Therefore, we have reasons to speculate that ATRA increased protection of Th2-type cytokines such as IL-4, decreased theβ-cell toxicity of Th1-type cytokines such as IFN-γ, the islet cells from damage and reduced non-specific STZ-induced pancreatic inflammation occurred.In conclusion, the way of the multiple low dose strepto- zotocin induce mice model of T1DM was set up, and first time analyse the activity of vitamin A and its derivatives ATRA in vivo role of T1DM and the prevention mechanisms, ATRA was found the protective effect on the isletβ-cell, and reducing the incidence of T1DM mice, T1DM as a preventive role, and its rise to the pancreatic isletβ-cells protection of the cytokine IL-4 levels can decrease toxicity of theβ-cell cytokine IFN-γlevels, and adjust the achieve the balance of Th1/Th2. Vitamin A and its derivatives activity can prevent T1DM caused by ATRA including some factors and some others, that is to say it might still exist many other complex ways. In the future work, on the one hand we need to thoroughly investigate the effect of vitamin A and its metabolites ATRA occurred with the development of T1DM, and the molecular and genetic level clarify the role of vitamin A mechanism. On the other hand, we must be even more basic and clinical combination of a prospective randomized controlled study of the crowd to determine vitamin A in the prevention and treatment of human diabetes status. Hopes that the ultimate application of vitamin A breakthrough for the prevention and treatment of human diabetes and open up new prospects. |
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