Maintenance ofβcell identity and functional maturation:a novel mechanism for diabetes intervention / 中华内分泌代谢杂志

The main etiology of diabetes mellitus is loss of functional β cell mass, which is responsible for the secretion of the insulin hormone to reduce elevated plasma glucose and to maintain glucose homeostasis. Type 1 diabetes has traditionally been characterized by autoimmune-mediated β-cell death leading to insulin dependence, whereas type 2 diabetes has hallmarks of peripheral insulin resistance, accompanied by β cell dysfunction, and cell death. However, a growing body of evidence suggests that β cell dysfunction and defects of functional maturation in type 2 diabetes involve: (1 ) loss of cell identity, specifically proteins associated with mature cell function and transcription factors like Pdx1,MafA,Nkx6. 1,Glut2,and GK,and (2) de-differentiation,defined by regression to a progenitor or stem cell-like state. Moreover, ectopic expression of genes that are disallowed in β cells is also crucial to maintain the mature phenotype of β cells. In this review, we will combine our preliminary data and summarize the recent literature describing how β cell functional maturation is regulated. We hope that this perspective could shed some lights on possible avenues of new therapeutic intervention for diabetes mellitus.

Influence of NNT mutation on glucose homeostasis in C57BL/6 mice / 中华内分泌代谢杂志

Objective To explore the effect of nicotinaide nucleotide transhydrogenase(NNT) mutation on glucose homeostasis in C57BL/6 mice with mix background. Methods We generated wild type NNT homozygous, mutant NNT homozygous and heterozygous by mating the C57BL/6J (with NNT mutation) and 6N (without NNT mutation). At the age of 4 weeks, those mice were randomly assigned to normal control diet(NCD) or high-fat diet(HFD) for 4 weeks. The body weight was measured every week. At the age of 8 weeks, an intraperitoneal glucose tolerance test(IPGTT) and an intraperitoneal insulin tolerance test (ITT) were performed. Results The body weight growth was not affected by NNT mutation during an HFD fed. NNT mutant mice showed significant glucose intolerance. After 4 weeks of high fat diet, the NNT mutant mice showed a decreased insulin sensitivity, while the glucose excursion curve was not elevated in the heterozygous mice. Conclusion NNT mutation had a significant influence on the phenotype of glucose metabolism and insulin resistance of mice, in particular under a metabolic stress. The phenotypes of heterozygous and homozygous mutant ones differed from each other. When using mice with C57BL/6J and C57BL/6N mixed background in research, NNT mutation should be carefully screened in all metabolic studies.

Regulation and mechanism of mTOR pathway in β-cell function and survival / 中华内分泌代谢杂志

mTOR pathway plays a critical role in cell proliferation, growth and metabolism. This pathway is composed of two different large protein complexes, mTORC1 and mTORC2, which have their distinct downstream effects. Its inhibitor, rapamycin, has been proved to cause β-cell damage and glucose intolerance. Furthermore, various transgenic mouse models and ex vivo studies have revealed that mTORC1 and mTORC2 are both essential for maintaining normal β cell mass and function, whereas the underlying molecular mechanism and the relevance of the whole mTOR signaling to pathogenesis of type 2 diabetes remain to be explored and further clarified.