沒食子酸丙酯對甲基乙二醛誘導小鼠腦神經損傷之保護效果

The protective effects of propyl gallate on methylglyoxal-induced brain nerve injury in mice

廖漢偉(Liao Han-Wei)

指導教授 ： 陳與國

國立屏東科技大學/農學院/食品科學系所/碩士(2021年)

https://doi.org/10.6346/NPUST202100325

摘要

阿茲海默症 (Alzheimer's disease) 是全世界失智症最常見的形式，佔了失智症病例的60-80%。發病的主要假設為β-澱粉樣蛋白 (β-amyloid, Aβ) 的累積和tau蛋白過度磷酸化，兩者均可導致神經元死亡和失智症狀的出現。甲基乙二醛 (Methylglyoxal, MG) 為一種高反應性的雙羰基醛類化合物，同時也為糖化終產物 (Advanced glycation end-products, AGEs) 的前驅物。許多研究也證實MG會造成神經損傷導致神經退化性疾病的發生，且AGEs也會加劇Aβ及磷酸化tau蛋白的產生。有研究指出沒食子酸丙酯 (Propyl gallate, PG) 可以與MG結合，並抑制超過77.5%的MG。故本實驗將MG添加於飲用水中讓小鼠飲用，並以管餵的方式探討20、40及100 mg/kg不同劑量之PG對MG誘導腦神經損傷之保護效果。在莫里斯水迷宮試驗中，給予PG能夠縮短小鼠找到平台的時間，改善小鼠的空間認知障礙，於新物體識別試驗也能發現MG組小鼠的辨別率只有0.34 ± 0.02，而在給予不同劑量的PG後，其辨別率提升為0.59 ± 0.01、0.65 ± 0.01與0.73 ± 0.03，可以依據劑量效應減少小鼠的長期記憶能力受損，並且於曠場試驗中餵食PG的小鼠可以表現出較佳的抗焦慮能力。西方墨點法的結果也顯示，給予PG後可以增加小鼠腦中PI3K、p-Akt、p-GSK-3β的蛋白表現量，進而抑制MG所造成的tau蛋白過度磷酸化和Aβ的生成，並改善海馬迴中的發炎反應，降低TNF-α及IL-6的蛋白質表現。此外，組織病理切片中可以看到給予PG能減少MG誘導產生的神經元功能障礙及神經元死亡，經過免疫組織化學染色也發現藉由PG的給予可以減少MG誘導的海馬迴tau蛋白過度磷酸化。且於血液生化數值分析中，ALT值的結果顯示給予20、40及100 mg/kg 的PG並不會對小鼠造成明顯的肝毒性。總結以上結果，PG具有保護MG誘導小鼠產生的腦神經損傷作用以及改善小鼠的認知能力下降之潛力。

關鍵字

阿茲海默症 ； 甲基乙二醛 ； 糖化終產物 ； 沒食子酸丙酯 ； β-澱粉樣蛋白 ； tau蛋白

並列摘要

Alzheimer's disease (AD) is the most common form of dementia worldwide and involves 60-80% of all reported dementias. The main hypothesis of pathogenesis focuses on the β-amyloid accumulation and tau hyperphosphorylation, both of which can lead to neuronal death and subsequent dementia. Methylglyoxal (MG) is a highly reactive dicarbonyl aldehyde, it is also the precursor of the advanced glycation end-products (AGEs). MG has been proved to be toxic to neuron and may be the reason of many neurodegenerative diseases, and AGEs also increased the production of Aβ and phosphorylated tau protein. Some studies indicated that Propyl gallate (PG) can bind to MG to form adduct and suppressed more than 77.5% MG. In this experiment, MG was added to drinking water of mice, and 20, 40 and 100 mg/kg of PG were administered orally to evaluate the protective effects of PG on MG-induced brain nerve injury in mice. In Morris water maze test, giving PG can shorten the time for mice to find the platform, which indicated the spatial cognitive impairment of mice was improved. In novel object recognition test, it can also showed that the discrimination ratio of mice in MG group was only 0.34 ± 0.02, and after treated with different doses of PG, the discrimination ratio increased to 0.59 ± 0.01, 0.65 ± 0.01 and 0.73 ± 0.03, which can be based on the dose effect to reduce impairment of long-term memory in mice. Moreover, the mice fed with PG showed better anxiolytic ability in the open field test than those of MG group. In western blot, the results showed that PG increased the protein expression of PI3K, p-Akt, p-GSK-3β of hippocampus in mice, and inhibiting MG-caused hyperphosphorylation of tau protein and Aβ accumulation. PG also reduced the protein expression of TNF-α and IL-6, representing that it improved the inflammatory response in the hippocampus. In addition, the results of histopathological examination indicated that administration of PG reduced neuronal dysfunction and neuronal death induced by MG. Immunohistochemical staining also showed that trapping of MG by PG reduced the hyperphosphorylation of tau protein of hippocampus in mice. In the analysis of blood biochemical parameters, the result of ALT levels indicated that 20, 40, and 100 mg/kg of PG treatment did not cause significant hepatotoxicity in mice. In summary, PG has the potential to protect the brain nerve damage induced by MG in mice and to improve the cognitive decline of mice.

並列關鍵字

Alzheimer's disease ； methylglyoxal ； advanced glycation end-products ； propyl gallate ； β-amyloid ； tau

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