Degradation of glucose-dependent insulinotropic polypeptide and truncated glucagon-like peptide 1 in vitro and in vivo by dipeptidyl peptidase IV.
Degradation of glucose-dependent insulinotropic polypeptide and truncated glucagon-like peptide 1 in vitro and in vivo by dipeptidyl peptidase IV.
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DOI：
10.1210/endo.136.8.7628397
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发表时间：
1995-08
期刊：
影响因子：
4.8
通讯作者：
T. Kieffer;C. Mcintosh;R. Pederson
中科院分区：
文献类型：
--
作者：
T. Kieffer;C. Mcintosh;R. Pederson
葡萄糖依赖性胰岛素性多肽（GIP）和截断胰高血糖素样肽-1 （tGLP-1）的联合作用可能充分解释了肠促胰岛素效应。这些激素在口服葡萄糖的作用下从小肠释放，并刺激胰岛素的释放。最近，有证据表明血清酶二肽基肽酶IV （DPP IV）可降解GIP-(1-42)和GLP-1-(7-36)NH2，生成具有生物活性的产物GIP-(3-42)和GLP-1-(9-36)NH2。本研究的目的是开发一种监测这些激素在体内降解的方法。用高效液相色谱法对合成肽进行放射性标记和纯化。随后在不同条件下对肽的降解进行进一步的HPLC分析。[125I]GIP-(1-42)或[125I]GLP-1-(7-36)NH2与Wistar大鼠血清或纯化的DPP IV孵育可产生n端截断的主要产物[125I]GIP-(3-42)和[125I]GLP-1-(9-36)NH2。当在孵育混合物中加入特异性DPP IV抑制剂双蛋白A时，这些产物显著减少，而当使用DPP IV缺陷大鼠的血清时，这些产物不存在。在生理激素水平范围内，将标记肽输注到大鼠体内，超过50%的肽在2分钟内被代谢成截短形式。当将示踪剂注入DPP iv缺陷动物体内时，这些产物不存在。综上所述，DPP IV可能是体内GIP和tGLP-1的初级灭活酶。由于目前使用的检测方法可能无法将DPP IV切割的n端截断产物与生物活性激素区分开来，因此应该重新考虑循环激素水平的报告。本文描述的方法可用于研究正常和病理生理条件下GIP和tGLP-1的作用持续时间。
The combined actions of glucose-dependent insulinotropic polypeptide (GIP) and truncated glucagon-like peptide-1 (tGLP-1) may fully account for the incretin effect. These hormones are released from the small intestine in response to oral glucose and stimulate insulin release. Recently, evidence has been provided demonstrating the degradation of GIP-(1-42) and GLP-1-(7-36)NH2 by the serum enzyme dipeptidyl peptidase IV (DPP IV) into the biologically inactive products GIP-(3-42) and GLP-1-(9-36)NH2. The objective of the current investigation was to develop a method to monitor the degradation of these hormones in vivo. Synthetic peptides were radiolabeled and purified by HPLC. Subsequent degradation of the peptides under various conditions was then monitored by further HPLC analysis. Incubation of [125I]GIP-(1-42) or [125I]GLP-1-(7-36)NH2 with Wistar rat serum or purified DPP IV resulted in the major N-terminal-truncated products [125I]GIP-(3-42) and [125I]GLP-1-(9-36)NH2. These products were significantly reduced when the specific DPP IV inhibitor diprotin A was included in the incubation mixture and were absent when serum from DPP IV-deficient rats was used. When the labeled peptides were infused into rats at hormone levels within the physiological range, over 50% was metabolized to the truncated forms within 2 min. These products were absent when the tracers were infused into DPP IV-deficient animals. It is concluded that DPP IV may be a primary inactivating enzyme of both GIP and tGLP-1 in vivo. As the N-terminal-truncated products of the DPP IV cleavage may not be distinguished from the biologically active hormone by currently employed assays, reports of circulating hormone levels should be reconsidered. The method described in this manuscript may be useful for investigating the durations of action of GIP and tGLP-1 in normal and pathophysiological conditions.