Background

Clinical trials and animal studies have shown that sodium-glucose co-transporter type 2 (SGLT2) inhibitors improve pancreatic beta cell function. Our study aimed to investigate the effect of dapagliflozin on islet morphology and cell phenotype, and explore the origin and possible reason of the regenerated beta cells.

Methods

Two diabetic mouse models, db/db mice and pancreatic alpha cell lineage-tracing (glucagon-β-gal) mice whose diabetes was induced by high fat diet combined with streptozotocin, were used. Mice were treated by daily intragastric administration of dapagliflozin (1 mg/kg) or vehicle for 6 weeks. The plasma insulin, glucagon and glucagon-like peptide-1 (GLP-1) were determined by using ELISA. The evaluation of islet morphology and cell phenotype was performed with immunofluorescence. Primary rodent islets and αTC1.9, a mouse alpha cell line, were incubated with dapagliflozin (0.25–25 μmol/L) or vehicle in the presence or absence of GLP-1 receptor antagonist for 24 h in regular or high glucose medium. The expression of specific markers and hormone levels were determined.

Results

Treatment with dapagliflozin significantly decreased blood glucose in the two diabetic models and upregulated plasma insulin and GLP-1 levels in db/db mice. The dapagliflozin treatment increased islet and beta cell numbers in the two diabetic mice. The beta cell proliferation as indicated by C-peptide and BrdU double-positive cells was boosted by dapagliflozin. The alpha to beta cell conversion, as evaluated by glucagon and insulin double-positive cells and confirmed by using alpha cell lineage-tracing, was facilitated by dapagliflozin. After the dapagliflozin treatment, some insulin-positive cells were located in the duct compartment or even co-localized with duct cell markers, suggestive of duct-derived beta cell neogenesis. In cultured primary rodent islets and αTC1.9 cells, dapagliflozin upregulated the expression of pancreatic endocrine progenitor and beta cell specific markers (including Pdx1) under high glucose condition. Moreover, dapagliflozin upregulated the expression of Pcsk1 (which encodes prohormone convertase 1/3, an important enzyme for processing proglucagon to GLP-1), and increased GLP-1 content and secretion in αTC1.9 cells. Importantly, the dapagliflozin-induced upregulation of Pdx1 expression was attenuated by GLP-1 receptor antagonist.

Conclusions

Except for glucose-lowering effect, dapagliflozin has extra protective effects on beta cells in type 2 diabetes. Dapagliflozin enhances beta cell self-replication, induces alpha to beta cell conversion, and promotes duct-derived beta cell neogenesis. The promoting effects of dapagliflozin on beta cell regeneration may be partially mediated via GLP-1 secreted from alpha cells.

中文翻译：

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Dapagliflozin通过诱导2型糖尿病小鼠的胰腺内分泌细胞表型转化来促进β细胞再生。

背景

临床试验和动物研究表明，钠-葡萄糖共转运蛋白2型（SGLT2）抑制剂可改善胰腺β细胞功能。我们的研究旨在研究达格列净对胰岛形态和细胞表型的影响，并探讨再生β细胞的起源和可能的原因。

方法

使用了两种糖尿病小鼠模型，即db / db小鼠和胰腺α细胞谱系追踪（胰高血糖素-β-gal）小鼠，其糖尿病是由高脂饮食与链脲佐菌素联合诱导的。每天通过胃内给予达格列净（1 mg / kg）或赋形剂治疗小鼠6周。通过ELISA测定血浆胰岛素，胰高血糖素和胰高血糖素样肽-1（GLP-1）。用免疫荧光法评估胰岛的形态和细胞表型。在有或没有GLP-1受体拮抗剂的情况下，将原代啮齿动物胰岛和小鼠α细胞系αTC1.9与dapagliflozin（0.25–25μmol/ L）或赋形剂在常规或高葡萄糖培养基中孵育24小时。确定了特定标志物的表达和激素水平。

结果

在两种糖尿病模型中，达格列净治疗显着降低血糖，db / db中血浆胰岛素和GLP-1水平上调老鼠。达格列净治疗增加了两只糖尿病小鼠的胰岛和β细胞数量。达格列净促进了C肽和BrdU双阳性细胞所指示的β细胞增殖。达格列净促进了胰高血糖素和胰岛素双阳性细胞评估并通过使用α细胞谱系追踪证实的α细胞到β细胞的转化。达格列净治疗后，一些胰岛素阳性细胞位于导管室中，甚至与导管细胞标记物共定位，提示导管来源的β细胞新生。在培养的原代啮齿动物胰岛和αTC1.9细胞中，达格列净上调了胰腺内分泌祖细胞和β细胞特异性标志物（包括Pdx1）的表达）在高葡萄糖条件下。此外，达格列净上调了Pcsk1的表达（编码激素激素转化酶1/3，这是将胰高血糖素加工成GLP-1的重要酶），并增加了αTC1.9细胞中GLP-1的含量和分泌。重要的是，GLP-1受体拮抗剂减弱了达格列净诱导的Pdx1表达上调。

结论

除了降低葡萄糖的作用外，达格列净对2型糖尿病的β细胞具有额外的保护作用。Dapagliflozin增强β细胞自我复制，诱导α至β细胞转化，并促进导管衍生的β细胞新生。达格列净的对β细胞再生的促进作用可以部分地介导通过GLP-1由α-细胞分泌。