University of Massachusetts Medical School, Diabetes Center of Excellence, 373 Plantation Street, Suite 218, Worcester, MA 01605, USA.
Gen Comp Endocrinol. 2011 Jan 15;170(2):334-45. doi: 10.1016/j.ygcen.2010.10.010. Epub 2010 Oct 20.
Zebrafish embryos are emerging as models of glucose metabolism. However, patterns of endogenous glucose levels, and the role of the islet in glucoregulation, are unknown. We measured absolute glucose levels in zebrafish and mouse embryos, and demonstrate similar, dynamic glucose fluctuations in both species. Further, we show that chemical and genetic perturbations elicit mammalian-like glycemic responses in zebrafish embryos. We show that glucose is undetectable in early zebrafish and mouse embryos, but increases in parallel with pancreatic islet formation in both species. In zebrafish, increasing glucose is associated with activation of gluconeogenic phosphoenolpyruvate carboxykinase1 (pck1) transcription. Non-hepatic Pck1 protein is expressed in mouse embryos. We show using RNA in situ hybridization, that zebrafish pck1 mRNA is similarly expressed in multiple cell types prior to hepatogenesis. Further, we demonstrate that the Pck1 inhibitor 3-mercaptopicolinic acid suppresses normal glucose accumulation in early zebrafish embryos. This shows that pre- and extra-hepatic pck1 is functional, and provides glucose locally to rapidly developing tissues. To determine if the primary islet is glucoregulatory in early fish embryos, we injected pdx1-specific morpholinos into transgenic embryos expressing GFP in beta cells. Most morphant islets were hypomorphic, not a genetic, but embryos still exhibited persistent hyperglycemia. We conclude from these data that the early zebrafish islet is functional, and regulates endogenous glucose. In summary, we identify mechanisms of glucoregulation in zebrafish embryos that are conserved with embryonic and adult mammals. These observations justify use of this model in mechanistic studies of human metabolic disease.
斑马鱼胚胎正逐渐成为研究葡萄糖代谢的模型。然而，内源性葡萄糖水平的模式以及胰岛在糖调节中的作用尚不清楚。我们测量了斑马鱼和小鼠胚胎中的绝对葡萄糖水平，并证明了这两种物种中都存在相似的动态葡萄糖波动。此外，我们还表明，化学和遗传扰动会在斑马鱼胚胎中引起类似哺乳动物的血糖反应。我们发现，在早期的斑马鱼和小鼠胚胎中，葡萄糖是不可检测的，但在这两种物种中，随着胰腺胰岛的形成，葡萄糖水平会平行增加。在斑马鱼中，葡萄糖的增加与糖异生磷酸烯醇丙酮酸羧激酶 1（pck1）转录的激活相关。非肝组织的 Pck1 蛋白在小鼠胚胎中表达。我们通过 RNA 原位杂交显示，在肝发生之前，斑马鱼 pck1 mRNA 也在多种细胞类型中表达。此外，我们证明 Pck1 抑制剂 3-巯基丙酮酸抑制了早期斑马鱼胚胎中正常的葡萄糖积累。这表明，肝前和肝外的 pck1 是有功能的，并且可以为快速发育的组织提供局部葡萄糖。为了确定初级胰岛在早期鱼胚胎中是否具有糖调节功能，我们将 pdx1 特异性的 morpholino 注入在β细胞中表达 GFP 的转基因胚胎中。大多数形态发生素胰岛是低能的，而不是遗传的，但胚胎仍然表现出持续的高血糖。我们从这些数据中得出结论，早期的斑马鱼胰岛是有功能的，并调节内源性葡萄糖。总之，我们确定了斑马鱼胚胎中糖调节的机制，这些机制与胚胎和成年哺乳动物中的机制保守。这些观察结果证明了该模型在人类代谢性疾病的机制研究中的合理性。
