常见肠、肝、肾疾病以及糖尿病状态下相关药物转运体的变化及其应用意义

转运体是位于细胞膜上的功能性膜蛋白。目前研究证明转运体在药物的吸收、分布以及排泄过程中发挥着重要的作用,其中以肠道、肝脏以及肾脏转运体的作用最为明显。疾病状态下转运体的表达和功能会发生改变,影响药物在体内的处置过程,使药物的药代动力学发生明显改变而对疾病的药物治疗产生影响。本文综述了常见肠道疾病、肝脏疾病、肾脏疾病以及糖尿病状态下相关转运体的变化及其对临床药物治疗的影响。     

常见药物转运体基因多态性对药动学影响及研究进展

药物转运体在体内药物的吸收（absorption）、分布（distribution）、代谢（metabolism）及排泄（excretion）的过程（ADME）中发挥着关键的作用。转运体在各组织器官的不同分布以及其基因多态性,导致某些药物的吸收、分布、代谢和排泄过程产生明显的个体差异。随着药物基因组学的快速发展,关于转运体基因多态性的研究报道越来越多。本文对近年来人体主要药物转运体基因多态性在药动学和药效学中的影响研究进行综述。     

肝脏的药物转运体及其临床意义的研究进展

介绍肝脏的药物转运体的功能、分布、底物特征及其对药物的体内处置过程的影响。按照肝脏药物转运体系统、体内处置的影响进行分类归纳总结。肝脏作为机体对内源物和外源物(药物)的代谢和排泄的重要器官,除了药物代谢酶外,肝脏转运体在其中也发挥着一定的作用。当药物转运体的功能受到影响时,往往会使其底物性药物的有效性和安全性发生改变。     

转运体介导的食物-药物相互作用

食物与药物之间的相互作用普遍存在,且作用机制也多种多样。目前,研究较多的是单个食物或食物中的某些营养成分通过调节药物转运体或代谢酶的功能从而影响药物的体内过程。食物对药物体内过程的影响包括吸收、分布、代谢、排泄四个方面,并且主要是调节其中参与的药物转运体和代谢酶的功能。转运体介导的食物对药物体内吸收的影响主要是通过调节肠上皮摄取型和外排型的转运体,从而影响药物的吸收;对分布的影响主要是通过调节体内一些屏障中的转运体;对代谢的影响主要是同时调节药物代谢酶和转运体;对排泄的影响是通过调节肾脏和肝脏胆汁排泄的药物转运体,从而影响药物的清除率。因此,转运体介导的食物与药物相互作用直接影响药物治疗的效果。     

慢性肾脏病对药物转运和代谢的影响

本文介绍了慢性肾脏病状态下,肾脏、肝脏及肠道中主要代谢酶和药物转运体介导药物转运和代谢的最新研究进展,以期为临床合理用药提供参考。肾脏疾病对肾脏、肝脏和肠道转运体及代谢酶均有一定的影响,是与肾脏本身器质性病变协同进展而表现出来的病理生理过程。在科研及临床实践中,有必要将肾脏疾病对其他器官的影响一并分析、综合考虑,以作出最客观最合理的判断。     

代谢酶和转运体介导的中药-西药相互作用的药动学机制研究进展

随着中草药的广泛应用,中药-西药相互作用(herb-drug interaction,HDI)问题日益凸显。代谢酶和转运体是影响药物体内处置过程的重要因素,其表达和功能的改变常常引起药代动力学的变化,是药物相互作用的主要靶点。代谢酶负责药物的代谢清除,主要包括细胞色素P450超家族(CYP)、UDP-葡萄糖醛酸基转移酶(UGT)以及磺酸化酶(SULT);转运体参与药物的口服吸收、体内分布以及排泄,主要包括肠道转运体、肾脏转运体、肝脏转运体以及脑转运体等。葛根、银杏叶、人参、圣约翰草等中草药在临床上应用广泛,且常与西药联合应用,其成分与代谢酶以及转运体存在相互作用,容易产生HDI。本文综述代谢酶、转运体介导的HDI的药代动力学机制,阐述常用中草药在与西药联合应用时应注意的问题。     

与肝肠循环相关的转运体及其基因多态性

药物穿过磷脂双分子层是其发挥作用和消除的重要步骤.转运体是一种穿过细胞膜磷脂双分子层的特殊蛋白,它通过主动和/或被动过程介导药物的跨膜转运.转运体在诸多参与体内药物、营养物质代谢及消除过程的组织和器官中都有表达.例如表达于小肠的转运体对于药物的吸收起重要作用;表达于肝细胞表面的不同类型转运体,可以介导药物进入肝细胞或排入胆汁;而表达于肾脏的转运体则可以参与药物的排泄.肝肠循环(enterohepatic circulation,EHC)是药物经胆汁排泄和小肠重吸收的过程,也有一些药物如霉酚酸以结合型代谢物排入肠道后再水解为原形药物重新吸收.EHC可能导致血药浓度的多重峰或半衰期的延长,进而影响药效.小肠和肝脏是药物EHC的重要器官,其中转运体对药物的EHC发挥着重要作用,转运体的表达和功能存在显著个体差异,本文将讨论肝脏和小肠中与EHC过程相关的主要转运体及基因多态性对其表达及功能的影响.     

转运体在药物经肝脏清除过程中的作用

肝脏在药物的体内清除过程中具有重要作用,它不仅是药物代谢的主要场所,还控制着药物及其代谢物的胆汁排泄过程。转运体是控制细胞内外物质传输的一类功能性膜蛋白,其在肝脏有广泛表达,并能对药物进入肝细胞以及排泄至胆汁的过程进行调控,因而,对于肝脏清除过程具有重要作用。本文从肝脏中重要转运体的分布、功能以及底物选择性出发,对其在药物的肝脏清除中的作用、由其引起的药物药物相互作用以及重要转运体的基因多态性研究进行了综述。     

肾脏转运体和/或代谢酶介导药物排泄及药物相互作用的研究进展

肾脏是人体最重要的排泄器官。肾单元近端小管细胞具有多种药物转运体和代谢酶,在药物及其代谢物处置中发挥关键作用。近端小管细胞中主要转运体包括有机阴离子转运体、有机阳离子转运体、有机阳离子/肉毒碱转运体、多药及毒素外排转运蛋白、P-糖蛋白、乳腺癌耐药蛋白和多药耐药相关蛋白;主要代谢酶包括细胞色素P450酶,UDP-葡萄糖醛酸基转移酶、磺酸基转移酶、谷胱甘肽S-转移酶。肾脏转运体和/或代谢酶介导药物相互作用(DDIs)是临床关注的重要问题。肾脏转运体和代谢酶存在密切协作关系,在肾脏也存在多种相互作用现象(包括转运-转运相互作用,代谢-代谢相互作用和转运-代谢相互作用),其显著影响药物肾脏处置、临床疗效和肾毒性。本文系统阐述了这些相互作用对药物及其代谢物的肾脏排泄、药动学、DDIs和肾毒性的影响。今后需要进一步阐明肾脏转运-代谢相互作用机制,将有助于研究体内药物肾脏处置和DDIs,促进临床合理用药。     

肝脏转运体和代谢酶在化学性肝损伤中的作用

肝脏是机体重要的代谢和解毒器官。肝细胞膜上存在多种功能性膜蛋白即肝脏药物转运体,它的功能是介导许多内源性及外源性物质如药物摄取进入肝脏,在肝脏内经过一定的代谢转化,最终将其从肝脏排入胆汁。研究发现,转运体和代谢酶在化学性肝损伤的发展过程中发挥重要的作用,其涉及的多种调控机制成为研究热点。就肝脏转运体和代谢酶的分类、转运体和代谢酶在化学性肝损伤中的变化及其调控机制作一综述。     

Kinetic impact of presystemic intestinal metabolism on drug absorption: experiment and data analysis for the prediction of in vivo absorption from in vitro data

Orally administered drugs suffer from attack by metabolic enzymes not only in the liver, but also in the gastrointestine during the absorption process across the intestinal tissue. Although kinetic study on hepatic metabolism has been done well, the intestinal metabolism has not been well focused on compared with hepatic metabolism. In order to emphasize the role of intestinal metabolism in drug absorption and bioavailability, I have reviewed the experimental methods for intestinal absorption and metabolism, and the data analysis. Since Klippert et al. reported the prediction of intestinal first-pass effect of phenacetin in the rat from enzyme kinetic data in 1982, several reports have showed a good prediction, but others have not. Although intestinal absorption is an integrated process of transport (transporters) and metabolism (metabolic enzymes), most of the researchers missed the pathway of intestinal drug absorption and applied the kinetic model effective on only systemic metabolism to presystemic intestinal metabolism for their analysis of intestinal metabolism of orally administered drugs. A kinetic model, which incorporated factors of membrane transport, metabolic activity and protein binding, was structured to compare the equations in the reported models. In conclusion, we need more studies including kinetic modeling and experiments to understand the impact of intestinal metabolism on drug absorption. That knowledge must lead to the construction of ADME in silico (e-ADME).     

Projecting ADME Behavior and Drug-Drug Interactions in Early Discovery and Development: Application of the Extended Clearance Classification System

Purpose

To assess the utility of Extended Clearance Classification System (ECCS) in understanding absorption, distribution, metabolism, and elimination (ADME) attributes and enabling victim drug-drug interaction (DDI) predictions.

Methods

A database of 368 drugs with relevant ADME parameters, main metabolizing enzymes, uptake transporters, efflux transporters, and highest change in exposure (%AUC) in presence of inhibitors was developed using published literature. Drugs were characterized according to ECCS using ionization, molecular weight and estimated permeability.

Results

Analyses suggested that ECCS class 1A drugs are well absorbed and systemic clearance is determined by metabolism mediated by CYP2C, esterases, and UGTs. For class 1B drugs, oral absorption is high and the predominant clearance mechanism is hepatic uptake mediated by OATP transporters. High permeability neutral/basic drugs (class 2) showed high oral absorption, with metabolism mediated generally by CYP3A, CYP2D6 and UGTs as the predominant clearance mechanism. Class 3A/4 drugs showed moderate absorption with dominant renal clearance involving OAT/OCT2 transporters. Class 3B drugs showed low to moderate absorption with hepatic uptake (OATPs) and/or renal clearance as primary clearance mechanisms. The highest DDI risk is typically seen with class 2/1B/3B compounds manifested by inhibition of either CYP metabolism or active hepatic uptake. Class 2 showed a wider range in AUC change likely due to a variety of enzymes involved. DDI risk for class 3A/4 is small and associated with inhibition of renal transporters.

Conclusions

ECCS provides a framework to project ADME profiles and further enables prediction of victim DDI liabilities in drug discovery and development.

     

口服降糖药的遗传药理学研究进展

糖尿病是一种受多基因和环境因素共同影响的代谢性疾病。药物代谢酶、受体和转运体的遗传多态性对口服降糖药的体内代谢和降糖疗效有重要作用。本文从细胞色素P450酶、转运体和受体多态性方面对5种主要口服降糖药（磺脲类、噻唑烷二酮类、氯茴苯酸类、双胍类、α-葡萄糖甙酶抑制剂）的体内代谢和药物效应的影响作一综述。     

大黄酸对药物转运体和代谢酶影响的研究进展

药物转运体和药物代谢酶是影响药物体内处置过程中至关重要的因素。大黄酸作为传统中药大黄的主要活性成分,具有广泛药理活性。研究发现,大黄酸与药物转运体和代谢酶密切相关,能够直接激活或抑制多种转运体的功能及其蛋白表达。而且大黄酸对药物代谢酶细胞色素P450（CYP450）的功能及其蛋白表达同样有抑制作用。因此,大黄酸与其他药物合用时,可能发生基于药动学的药物相互作用（drug-drug interaction,DDI）。从药物转运体和代谢酶的体内分布、大黄酸对转运体及代谢酶的影响等方面进行综述。     

Scientific perspectives on drug transporters and their role in drug interactions

Recently, increased interest in drug transporters and research in this area has revealed that drug transporters play an important role in modulating drug absorption, distribution, and elimination. Acting alone or in concert with drug metabolizing enzymes they can affect the pharmacokinetics and pharmacodynamics of a drug. This commentary will focus on the potential role that drug transporters may play in drug-drug interactions and what information may be needed during drug development and new drug application (NDA) submissions to address potential drug interactions mediated by transporters.     

Circadian regulation of the hepatic endobiotic and xenobitoic detoxification pathways: the time matters

Metabolic processes have to be regulated tightly to prevent waste of energy and to ensure sufficient detoxification. Most anabolic processes operate in a timely manner when energy intake is the highest, while catabolism takes place in energy spending periods. Endobiotic and xenobiotic metabolism are therefore under circadian control. Circadian regulation is mediated through the suprachiasmatic nucleus (SCN), a master autonomous oscillator of the brain. Although many peripheral organs have their own oscillators, the SCN is important in orchestrating and entraining organs according to the environmental light cues. However, light is not the only signal for entrainment of internal clocks. For endobiotic and xenobitoic detoxification pathways, the food composition and intake regime are equally important. The rhythm of the liver as an organ where the major metabolic pathways intersect depends on SCN signals, signals from endocrine tissues, and, importantly, the type and time of feeding or xenobiotics ingestion. Several enzymes are involved in detoxification processes. Phase I is composed mainly of cytochromes P450, which are regulated by nuclear receptors. Phase II enzymes modify the phase I metabolites, while phase III includes membrane transporters responsible for the elimination of modified xenobiotics. Phases I-III of drug metabolism are under strong circadian regulation, starting with the drug-sensing nuclear receptors and ending with drug transporters. Disturbed circadian regualtion (jet-lag, shift work, and dysfunction of core clock genes) leads to changed periods of activity, sleep disorders, disturbed glucose homeostasis, breast or colon cancer, and metabolic syndrome. As many xenobiotics influence the circadian rhythm of the liver, bad drug administration timing can worsen the above listed effects. This review will cover the major hepatic circadian regulation of endogenous and xenobiotic metabolic pathways and will provide examples of how good timing of drug administration can change drug failure to treatment success.     

转运体和代谢酶在胆汁淤积性肝损伤中的作用机制

胆汁淤积性肝损伤是临床常见的肝脏疾病,主要由体内胆汁酸平衡失调引起,其发病机制与胆汁酸转运体、合成酶和代谢酶的表达和功能变化直接相关。核受体通过调控胆汁酸转运体及代谢酶的表达,在胆汁淤积所致的肝损伤中发挥重要作用。对肝脏转运体和代谢酶在胆汁淤积性肝损伤中的作用及核受体对转运体和代谢酶的调控机制作一综述。