Streptozotocin Induced The Molecular Mechanisms Of Islet ¦Â Cell Injury

PartⅠFunctional Analysis of Differential Expression Genes in Pancreas ofStreptozotocin Induced Diabetic MonkeysObjective To screen the differential expression genes in pancreas ofstreptozotocin induced diabetic monkeys versus controls and discuss their probableroles in the process of 13 cell destruction in diabetes. Methods Through a singleinjection of large amount of STZ to monkeys, type 1 diabetic animal model wasestablished. Differential expression genes were screened from an oligo-microarraychip hybridized to cRNA extracted from pancreas of diabetic or control monkeys.Some of the genes related to apoptosis, metabolism or function maintaining wereselected to a further discussion. Semi-quantitative RT-PCR was performed to verifythe differential expression of some important genes. Results Totally 425 genes weredifferential expressed in the pancreas of STZ induced diabetes versus that of controls.Genes implicated in the process of protein synthesis, transcription, signal transductionand metabolism have the largest amount among the known differential expressiongenes. Conclusions Genes related to JAK/STAT/SOCS signal transduction andendoplasm reticulum(ER) stress might play important roles in the process ofβcellapoptosis or function destruction. GH-IGF-IGFBP axis and some other growth factorsmay associated to the hyperplasia followingβcell destruction. Disturbance ofmetabolism further worsensβcell function. PartⅡExpression of Nicotinamide N-Methyltransferase(NNMT) inPancreatic Islets and Insulin Targeting Tissues of STZ-inducedDiabetic Monkeys and Type 2 DiabetesObjective To verify and localize the increased expression of nicotinamideN-methyltransferase (NNMT) in pancreas of STZ induced diabetic monkeys andtype 2 diabetes compared to that of controls. To observe the differential expression ofNNMT in insulin sensitive tissues of type 2 diabetic patients. MethodsSemiquantitative RT-PCR and Western blotting were performed to observe theexpression of NNMT in pancreas or insulin sensitive tissues of STZ induced diabeticmonkeys and type 2 diabetic patients. The cellular localization of NNMT expressionwithin pancreas was identified by immunohistochemical(IHC) staining. Results Anobviously elevated expression of NNMT at both mRNA and protein levels was shownin pancreas of STZ-induced diabetic monkeys but not in that of type 2 diabeticpatients. Further localization of the protein by IHC staining in pancreas specimensshowed that its altered expression was restricted to central islets most of which areβcells. In type 2 diabetic patients but not in STZ induced diabetic monkeys, expressionof NNMT was increased in muscle and adipose tissues. Conclusion Expression ofNNMT was increased in islets of STZ induced diabetic monkeys versus that ofcontrols which infers that the enzyme might participate in the process of beta-celldamage in diabetes probably through the mechanism of energy metabolismdisturbance. The different expression pattern of NNMT between STZ induced diabeticmonkeys and type 2 diabetic patients implied that it may participate in thepathogenesis ofβcell destruction of type 1 diabetes and insulin resistance of type 2diabetes. PartⅢThe Effects of Streptozotocin on the Expression of Apoptosis-relatedGenes in Mouseβ-TC3 CellsObjective To evaluate the pro-apoptosis effects and thedifferential expression of apoptosis related genes in mouseβ-TC3 cell line understreptozotocin (STZ) treatment. Methods (1) Treated with different concentrationsof STZ, the morphology ofβ-TC3 cells were observed under an optical microscope.(2) After incubated in the culture medium containing 2.5mmol/L STZ for 24 hours,βoTC3 cells were double stained with Annexin V/FITC and PI and measured in a flowcytometer. Caspase-3 activity ofβ-TC3 cells at the same treatment was measuredusing an assay kit. (3) The expression of apoptosis related genes inβ-TC3 cellsunder treatment of STZ were evaluated by an olig-microarray hybridization. (4)Real-time PCR were performed to verify the altered expression of Bcl-2 familymumbers. Results (1)Treatingβ-TC3 cells with different concentrations of STZ for6 hours induced morphological alterations gradually following increasingconcentrations including cells protuberance blunted or disappeared, cells shrunk androunded up, cytoplasmic granules accumulated and nucleus condensed. (2)Aftertreatment with STZ, the early apoptosis rates ofβ-TC3 cells increased markedlycompared to controls. Caspase-3 activity was also elevated in STZ-treated cells versusthat of controls. (3)The mRNA expression of 24 apoptosis related genes inβ-TC3cells was altered under 24 hours of 2.5mmol/L STZ culture including some membersof caspase family, Bcl-2 family, TNF receptor family, IAP family, TRAF family, deathdomain family, CIDE family and p53 family. The increased expression of Bax, Bad orBok of Bcl-2 family in STZ treatedβ-TC3 cells was verified by Real-time PCR.Conclusion STZ might induceβ-cell apoptosis even under low concentrations andmay be accelerated while under higher concentrations manifesting cells shrinking.STZ might directly or indirectly activate two main pro-apoptosis pathways to induceapoptosis ofβ-TC3 cells.