The Role Of Nrf2 In Insulin Secretion And Differentiation Function Of Pancreatic β-cell

Objective: The prevalence of diabetes remains high,and the global prevalence of diabetes was 10.5 percent.Diabetes is known as a "sweet killer".long-term and ineffectively controlled hyperglycemia leads to dehydration,fatigue,metabolic disorders.It causes people to suffer from various diabetic complications,such as retinopathy cardiovascular,cerebrovascular diseases,kidney disease,retinopathy,neurovascular lesions.The insufficiency β-cells is considered the main factor in the development of diabetes and has received wide attention.Studies have shown,Nrf2 can control antioxidant,antiinflammatory,detoxification,anti-apoptotic and other cytoprotection mechanisms,maintain the redox balance of β-cells and play an important role in the secretion of insulin.However,most research has focused on the antioxidant defense function of Nrf2 on β-cells,and most studies used the whole-body knockout of Nrf2 mouse model.Therefore,in this study,to study the effect of Nrf2 deletion on β-cells function,pancreatic β cells specific Nrf2 knockout mice was constructed,MIN6 β-cell lines with stable and low expression of Nrf2 were used.We investigated the mechanism tentatively.Methods: Pancreatic β cells-specific Nrf2 knockout mouse model,Nrf2(β)-KO mice,were established to detect mouse basal indices and evaluate mouse glucose metabolism function.The pancreatic tissues of adulthood mice were obtained,subsequently,we performed hematoxylin-eosin staining,immunohistochemistry and immunofluorescence experiments.The experimental results were quantitatively analyzed.Transcriptome sequencing was performed on MIN6 Nrf2-KD cells and MIN6 Scramble cells.Transcriptome analysis results are explored and validated by using realtime fluorescence quantification.Results:1.The results of basic index detection: There was no apparent difference in body weight and organ coefficients of mice in the same age,and there was no clear difference in body composition between male mice.There was no significant difference in muscle content in female mice.Nrf2(β)-KO mice had higher body fat content than Nrf2-Lox P mice and Ins2-Cre mice,with statistically significant differences at 12-14 weeks.2.The results of glucose metabolism evaluation: There was no significant difference in fasting blood glucose and postprandial blood glucose in these mice.Nrf2(β)-KO mice show impaired glucose tolerance in intraperitoneal glucose tolerance experiments.In the glucose-stimulated insulin secretion experiments,Nrf2(β)-KO mice showed lower basal serum insulin content and lower serum insulin content after glucose stimulation than Nrf2-Lox P mice.The difference was statistically significant.3.The results of hematoxylin-eosin staining: HE staining showed that the exocrine part of the mouse pancreas,the size and morphology of the mouse islet did not change significantly.The results of insulin and glucagon immunofluorescence double staining: Nrf2(β)-KO mice had more glucagon-positive cells in the internal region of the islet.The results of insulin and somatostatin immunofluorescence double staining: More insulin and somatostatin co-staining appeared in the pancreas sections of Nrf2(β)-KO mice,and some somatostatin-positive cells appeared in the internal region of the islet.4.The results of cell experiments: The expression levels of NRF2 and INSULIN in MIN6 Nrf2-KD cells were significantly lower than those in Min6 Scramble cells.Transcriptome sequencing of Nrf2-KD cells showed that Nrf2-KD cells significantly downregulated glucose metabolism processes,such as glucose response,glucose transport,and maintenance of glucose homeostasis.The transcription factors,Ins1、Maf A、Pdx1、Pax4、Neurod1、Ucn3、Cul4B、Pax6 were significantly reduced in Nrf2-KD cells.In Nrf2-KD cells,the expression of Ldha、Hk1、Rbp4 transcription factors was significantly increased.Conclusion: Specific deletion of Nrf2 in pancreatic islet β cells had no effect on body weight,basal blood glucose and body composition in mice,but Nrf2 regulates insulin synthesis and secretion.Nrf2 deficiency causes transdifferentiation of islet β cells into islet δ cells.