在路易氏體失智症模式中胰島素與神經毒性之關聯

The relationship between insulin and neurotoxicity in dementia with Lewy bodies model

張清棊(Ching-Chi Chang)

指導教授 ： 賴德仁

中山醫學大學/醫學院/醫學研究所/博士(2020年)

https://doi.org/10.6834/csmu202000226

摘要

路易氏體失智症(Dementia with Lewy bodies, DLB)為盛行率第三高的失智症，僅次於阿茲海默症(Alzheimer’s disease, AD)，及血管性失智症(Vascular dementia)。DLB的臨床症狀，混合了類似阿茲海默症的記憶力退化，及巴金森氏症(Parkinson's disease, PD)的運動障礙症狀，而病理生理學表現方面，也可發現DLB腦內具有巴金森氏症患者腦內的α-synuclein，與阿茲海默症腦內的β-類澱粉蛋白(Amloid-β)，並且均會產生大量的神經元損傷及腦部萎縮。然而目前臨床上並無能改善DLB疾病病程的治療藥物，亟待開發更有效的治療藥物。過去研究顯示糖尿病患者罹患失智症的機率會比一般人高，而近年來也有許多證據指出許多神經退化疾病中都可觀察到發生胰島素訊息發生阻抗。
研究目的：希望探討Aβ在誘發α-synuclein的聚集及造成神經毒性中所扮演的角色，並嘗試藉由胰島素減輕Aβ所造成的細胞損傷，並進一步研究胰島素信號傳遞與α-synuclein、
Aβ造成神經毒性之間的關聯性，以對於未來治療方式做出突破性的進展。
研究方法：<1>在本研究的細胞實驗部分，利用質體轉染神經細胞，促進α-synuclein過度表現，並且在對此細胞加上Aβ的共同作用，藉以模擬DLB患者腦部的情況，並觀察細胞的存活度、氧化壓力、細胞自噬現象是否有改變。之後再加上胰島素，觀察細胞毒性是否減輕。
<2>動物實驗部分：用病毒將可過度表現α-synuclein的基因載體注射進大鼠的腦室，並
Aβ也注射入大鼠的腦部，之後進行認知測驗，並進行腦部切片檢查，觀察是否有類似細胞實驗的結果。
<3>臨床實驗部份：我們收集醫學中心的臨床數據，觀察同時罹患DLB與糖尿病的患者，計算糖化血色素值與認知功能的皮爾森相關係數，觀察是否能呼應細胞及動物實驗的結果。
研究結果：細胞實驗中，Aβ確實會加強α-synuclein的細胞毒性，讓細胞存活率降低，而若再給予胰島素，則可顯著提升細胞存活率、降低氧化壓力、亦可增加自噬作用相關蛋白表現、減緩Aβ加成α-synuclein神經毒性所誘導的氧化壓力傷害。大鼠的動物模式中，發現Aβ加成α-synuclein會對大鼠的腦細胞造成類似我們在細胞實驗看到的神經細胞損傷，且動物在認知測驗中表現也較差。醫學中心的臨床數據中，DLB患者的糖化血色素值與認知功能測驗結果，呈現中度負相關。這些結果顯示，胰島素訊號對於Aβ加成α-synuclein的神經毒性產生保護效果，這提供了DLB未來可能的治療策略新的發展方向。

關鍵字

路易氏體 ； 失智症 ； 胰島素 ； α突觸核蛋白 ； β類澱粉蛋 白

並列摘要

Dementia with Lewy bodies (DLB) is the third most common cause of dementia, following Alzheimer's disease (AD) and vascular dementia. DLB has some similar clinical and pathological features with AD and Parkinson's disease (PD) that simultaneously accompany α-synuclein and Amloid-β (Aβ). These misfolded proteins accumulate in the brain and result in a large number of neuronal damage and brain atrophy, eventually leading to the damages of the corresponding neurological function. However, there is currently still no effective treatment to modify the degenerative course of DLB. It is in urgent need for developing new therapeutic strategies. According to previous studies, diabetes itself is a risk factor of dementia. Past studies have stated insulin resistance may be a common feature of many neurodegenerative diseases.
Research Purpose：Investigate the possible roles of Aβ in α-synuclein aggregation, and try to use insulin to reduce neurotoxicity related to Aβ and α-synuclein. We hope to find new strategies for DLB treatment in the future.
Research Methods：<1>cell model：We developed a model to stimulate α-synuclein over-expression in neuronal cells, and then co-treated with Amyloid-β to mimic the pathological condition of DLB. We also tried to co-treat insulin, and we observed the effect of insulin to neurotoxicity related to Aβ and α-synuclein.
<2>animal model：We established a DLB-like animal model. We performed gene transduction in Rats’ brain to over-express α-synuclein. We also injected Aβ to Rats’ brain. Cognitive tests and brain autopsy were arranged.
<3>Clinical chart review：We tried to collect medical charts in a medical center, to find the relationships between blood sugar level and cognitive function impairment in patients have both DLB and diabetes mellitus.
Research Results：In cell model, the results showed Aβ significantly enhances cytotoxicity of α-synuclein and decreases cell viability. We also found insulin demonstrated a propective effect to neuronal cells. Oxidative stress induced by Aβ and α-synuclein was also reduced by insulin treatment. Autophagy was also enhanced. In animal model, we found Aβ and α-synuclein induced similar cytotoxicity in rats’ brains and cognitive function decline was also observed. In clinical chart review, we found a moderate negative correlation between HbA1c and MMSE data in DLB patients. Taken together, our study demonstrated that Aβ significantly enhance cytotoxicity of α-synuclein, and insulin signaling may reduce the cytotoxicity and increasecell viability.

並列關鍵字

Lewy bodies ； dementia ； insulin ； synucleinopathy ； amyloid beta

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