DPP-4 抑制劑 Linagliptin對抗β類澱粉蛋白導致神經毒性之保護作用

胰島素阻抗是引發代謝疾患的重要危險因子。高血糖會增加周邊系統的胰島素使用率，並減少腦部胰島素的運送。胰島素與類胰島素生長因子調控中樞神經系統中神經生存與長壽等重要功能，另外，學習與記憶功能也受其掌控。由神經發展的觀點來看，胰島素訊息傳遞可能控制著神經退化的關鍵因子。阿茲海默症是神經退化疾病中最常見的疾患，這是一個由膽鹼神經元逐漸失能導致病人開始出現嚴重的行為、運動與認知功能障礙的疾病，最終將導致身體功能逐漸衰弱的神經疾患。逐漸增加的證據顯示，阿茲海默症與代謝疾患如：第二型糖尿病之間在病原學方面可能有相似的機制，如：胰島素阻抗。而由研究第二型糖尿病而發展出的藥物可能可以緩和阿茲海默症的病程發展，並且維持其認知功能。 DPP-4抑制劑是新一代發展出的第二型糖尿病用藥，它的主要功能是增強腸道內生性荷爾蒙 GLP-1的功能，由此促進胰島素的分泌。但是，抑制 DPP-4酵素的活性對中樞神經系統的影響機制則尚未有進一步的探討。在本研究中，我們測試了 DPP-4抑制劑： Linagliptin在神經元細胞中的功能，並進一步了解其對神經退化性疾病是否有正向影響。我們使用細胞存活率測定 DPP-4抑制劑： Linagliptin是否減少乙型類澱粉蛋白在神經元細胞 SK-N-MC中造成的傷害，然後使用免疫螢光染色偵測 SK-N-MC中 GLP-1受體的表現情形。以 Western Blot 偵測 DPP-4抑制劑： Linagliptin在神經元細胞中對胰島素訊息傳遞路徑相關蛋白的影響，以免疫螢光染色測試 DPP-4抑制劑： Linagliptin對自噬小體與粒線體的影響，最後以 Western Blot偵測自噬作用與 SOD-1等蛋白表現的影響。結果顯示， DPP-4抑制劑： Linagliptin能夠活化神經元細胞 SK-N-MC中胰島素訊息傳遞路徑相關蛋白的表現，並且透過增加自噬小體來提高神經元細胞 SK-N-MC之自噬作用，並且可以增加 SOD-1的活性來提高氧化壓力分子的清除機制，藉此減少乙型類澱粉蛋白對神經元細胞 SK-N-MC的傷害。根據結果顯示， DPP-4抑制劑： Linagliptin的確可以透過調控特定機轉來幫助神經元細胞 SK-N-MC對抗由乙型類澱粉蛋白所引發的傷害。另外，雖然在本研究中初步得知 DPP-4抑制劑： Linagliptin可以透過機制影響神經元細胞 SK-N-MC，但在中樞神經系統中除了目前已知的功能以外，我們認為 DPP-4抑制劑： Linagliptin尚有其他未知的機轉存在。因此，進一步探討 DPP-4抑制劑： Linagliptin在中樞神經系統的功能將會帶給我們對此藥物更進一步的了解。

關鍵字

DPP-4抑制劑； Linagliptin ；胰島素訊息傳遞；神經退化性疾病；阿茲海默症

並列摘要

Insulin resistance is a major risk factor for metabolic disorder. Hyperglycaemia induces increased peripheral utilization of insulin, resulting in reduced insulin transport into the brain. Insulin and insulin-like growth factor (IGF) regulate key processes such as neuronal survival and longevity, as well as learning and memory in the central nervous system (CNS). From the perspective of neurodevelopment, insulin signaling may control the key process of neurodegeneration. Alzheimer disease (AD) is the most common disease of neurodegeneration disorder, it is a debilitating neurodegenerative disorder characterized by the progressive loss of cholinergic neurons, leading to the onset of severe behavioral, motor and cognitive impairments. With increase of evidence, AD and metabolic disorder such as type 2 diabetes mellitus (T2DM) may share some similar mechanism in their etiology, for example, insulin resistance. Drugs developed for the treatment of T2DM may be beneficial in modifying the pathophysiology of AD and maintaining cognitive function. Dipeptidyl peptidase 4 (DPP-4) inhibitors are current drugs for the treatment of T2DM based on their main property to enhance endogenous glucagon-like peptide-1 (GLP-1) levels, thus increasing insulin secretion. However, the mechanism of action of DPP-4 inhibition in CNS has been poorly investigated. In this study, we investigated the functional activity in neurons of Linagliptin (one of the DPP-4 inhibitors) to understand is there any positive effect in neurodegenerative disorder. We tested the function of Linagliptin in reduced the damage of amyloid-β for SK-N-MC by cell survival rate, and we detected the expression of GLP-1 receptors in SK-N-MC by immunofluorescence staining assay. To understand if Linagliptin has any effects on insulin signaling pathway in SK-N-MC, we detected the protein expression by Western Blot. In order to further learn the effects of Linagliptin in SK-N-MC, we tested the function of autophagosome and mitochondria, and detected the protein expression by Western Blot. The results indicated that Linagliptin can enhance the insulin signaling pathway, and increased autophagy of SK-N-MC by increasing the number of autophagosome. Moreover, Linagliptin can also enhance the clearance of oxidative stress by increasing the expression of SOD-1. Therefore, by the administration of Linagliptin, the injury by amyloid-β in SK-N-MC will be reduced. Above all, our data showed that Linagliptin can reduce the damage of amyloid-β in SK-N-MC by certain mechanisms; however, other possible mechanisms in CNS are still unknown. Further investigation of Linagliptin in CNS will help to reveal more insights on this drug.

並列關鍵字

DPP-4 inhibitor ； Linagliptin ； insulin signaling pathway ； neurodegeneration disorder ； Alzheimer disease

參考文獻

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DPP-4 抑制劑 Linagliptin對抗β類澱粉蛋白導致神經毒性之保護作用

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