Studies on the impact of the drug transporter OATP1B3 on the pancreatic effects of CCK-8 and sulfonylurea derivatives

促进细胞摄取的转运蛋白在调节其底物的细胞内功能方面起着关键作用。有机阴离子转运多肽是一类介导细胞摄取的转运蛋白家族。特别是，OATP1B亚家族的成员是药理学研究的重点，因为这些蛋白运输临床上使用的各种药物。在这项提案的准备过程中，我们能够展示摄取转运体OATP1B3在人胰腺产生胰岛素的胰岛细胞中的表达。考虑到以前的研究揭示了胆囊素-8(CCK-8)是一种肠道形成的胰岛素作为OATP1B3的特异性内源性底物，而且我们的初步数据和其他人的先前发现表明几种磺脲类化合物与OATP1B3相互作用，因此OATP1B3在胰腺中表达的生理学和药理学相关性的问题提出了。为了深入了解OATP1B3在胰岛细胞中的功能，我们将建立一个葡萄糖敏感、分泌胰岛素、高表达OATP1B3的细胞系，并对其进行功能鉴定。转运蛋白对CCK-8和磺酰尿衍生物细胞效应的影响将是后续评估内源性和外源性底物对转基因胰岛细胞胰岛素分泌影响的体外研究的重点。此外，还将确定磺酰脲衍生物与CCK-8生理功能的潜在相互作用。除了这些细胞效应外，它还将旨在显示OATP1B3直接转运磺酰基脲衍生物。翻译方法的基础是我们之前发现的OATP1B3功能受损和频繁发生的遗传变异。在纳入研究之前，对健康志愿者进行OATP1B3基因分型的临床研究的目的是确定各自的基因多态对CCK-8生理功能的影响。为了做到这一点，将进行一项双臂研究。在第一个治疗期，将在摄入标准化膳食后确定基因变异对肠道形成和分泌的CCK-8的系统处置的影响。值得注意的是，OATP1B3在肝细胞中高表达，因此可能影响CCK-8的生物利用度。在第二个疗程中，将在摄入75g葡萄糖后评估OATP1B3基因变异对CCK-8促进胰岛素释放作用的影响。除了CCK-8，还将测定胰岛素和其他已知的葡萄糖稳态调节剂的水平。这项研究已经得到了当地伦理委员会的批准，并将与格雷夫斯瓦尔德大学的临床药理学系合作进行。

Transporters facilitating cellular uptake play a pivotal role in modulating the intracellular functions of their substrates. Organic Anion Transporting Polypeptides are one family of transporters mediating cellular uptake. Particularly, the members of the OATP1B-subfamily were focus of pharmacological studies as these proteins transport a variety of drugs in clinical use.In preparation of this proposal we were able to show expression of the uptake transporter OATP1B3 in the insulin-producing -islet cells of human pancreas. Considering that previous studies revealed choleystokinin-8 (CCK-8), an intestinal formed incretine as an OATP1B3-specific endogenous substrate and that our preliminary data and previous findings by others show interaction of several sulfonylurea derivatives with OATP1B3 the question of the physiological and pharmacological relevance of the pancreatic expression of OATP1B3 rises. In order to obtain insights in the function of OATP1B3 in -islet cells, a glucose-sensitive, insulin-producing, and OATP1B3-overexpressing cell-line will be generated and functionally characterized. The impact of the transporter on the cellular effects of CCK-8 and of sulfonylurea derivatives will be focus of the subsequent in vitro studies assessing the influence of the endogenous and exogenous substrates on the insulin secretion by transfected -islet cells. In addition, the potential interaction of sulfonylurea derivatives with the physiological function of CCK-8 will be determined. In addition to those cellular effects it will be aim to show direct transport of sulfonylurea derivatives by OATP1B3. Basis of a translational approach are our previous findings of function impairing, and frequently occurring genetic variants of OATP1B3. It is aim of the clinical study in healthy volunteers genotyped for OATP1B3 variants prior to study inclusion, to determine the influence of the respective polymorphisms on the physiological function of CCK-8. In order to do so, a two-armed study will be conducted. In the first treatment period the impact of the genetic variants on the systemic disposition of intestinal formed and secreted CCK-8 will be determined after intake of a standardized meal. It seems noteworthy, that OATP1B3 is highly expressed in hepatocytes and might therefore influence bioavailability of CCK-8. In the second treatment period the impact of genetic variants of OATP1B3 on the insulin release promoting effects of CCK-8 will be assessed after intake of 75 g Glucose. In addition to CCK-8, the levels of insulin and other known modulators of glucose homeostasis will be determined. The study has been approved by the local ethic committee and will be conducted in collaboration with the Department of Clinical Pharmacolgy of the Universitätsmedizin Greifswald.