| 摘要: | 神經退化的症狀包含運動、認知、情緒及其他行為上的改變，隨著年紀加劇外，也會由其他突發狀況所誘發，像腦創傷 (traumatic brain injury, TBI) 或腦中風，此已不僅僅是全球性的健康議題，甚已造成社會經濟的嚴重負擔。TBI每年發生率高於腦中風，亦做為急性與慢性神經退化過程中的誘因。TBI患者中以輕度 (mild TBI, mTBI) 比例最高，患者在急性損傷後可能遭受各種長期性神經及精神後遺症，甚至發展成慢性神經退化性疾病如阿茲海默症 (Alzheimer’s disease, AD) 及巴金森氏症 (Parkinson’s disease, PD)。但不管是急性或慢性，至今仍缺乏藥物能改善神經退化所伴隨的症狀，然而，促胰島素相關的藥物在目前已逐漸發展成一新適應症，以抗糖尿病藥物來治療神經退化性疾病。
在本研究計畫，將探討葡萄糖依賴性促胰島素多肽 (glucose-dependent insulinotropic polypeptide, GIP) 的神經保護作用，其與類升糖素胜肽 (glucagon-like peptide-1, GLP-1)皆為為腸促胰島素。運用輕度可控制皮質撞擊腦創傷 (mild controlled cortical impact, mCCI) 及顱內注射神經毒6-羥基多巴胺 (6-hydroxydopamine, 6-OHDA) 所誘發之動物疾病模式，討論在神經退化造成的行為改變中，GIP所扮演的角色。在疾病模式建立前兩天，透過ALZET植入式滲透壓膠囊持續並穩定釋放的方式給予GIP治療。針對急性神經退化，我們利用Morris水迷宮 (Morris water maze, MWM) 及辨識新物件 (novel object recognition, NOR) 的方法來驗證GIP治療mTBI大鼠認知作用的假設。進一步再用走平衡木及撕貼紙的方式來檢測mTBI大鼠的感覺運動功能。再者針對慢性神經退化，GIP對6-OHDA所誘發之PD大鼠的神經保護作用，將以鹽酸阿朴嗎啡 (apomorphine) 誘導向損傷的對側轉圈以及開放空間內的活動力與類焦慮行為作檢測。在藥物治療期間的第五天監測大鼠血漿中人類具活性及總GIP的濃度，以酵素連結免疫吸附法 (enzyme-linked immunosorbent assay, ELISA) 檢測並確立兩者神經退化性疾病動物模式的濃度能合乎臨床轉譯的濃度範圍。最後，我們將利用組織免疫 (immunohistochemistry, IHC) 染色及西方墨點 (western blot, WB) 法來探討在大鼠體內的相關調控機制。
總述，GIP在神經退化性疾病的誘發及進程中，具神經保護作用，能改善mCCI及6-OHDA所誘發之行為缺失。此外，GIP能減少mTBI所引發的神經發炎反應，包含膠質微纖維酸性蛋白質(glial fibrillary acidic protein, GFAP)、類澱粉前驅蛋白 (amyloid precursor protein, APP) 及染色體X骨髓酪胺酸激酶 (bone marrow tyrosine kinase gene in chromosome X, BMX) 的蛋白質表現。據此，GIP有益於改善神經退化性相關病症，做為此類藥物治療神經退化性疾病之新適應症。
Neurodegenerative symptoms involving motor, cognitive, emotional and other behavioral changes have increased progressively with age and can be triggered by a sudden event like traumatic brain injury (TBI) or stroke. This presents not only a global health problem but also a serious socioeconomic burden. The incidence rate of TBI in each year is higher than stroke and is identified as a potential initiator of acute and chronic neurodegenerative processes. Additionally, mild TBI (mTBI) is the most common among TBI survivors, the patients with acute injury suffer various long term neurological and neuropsychiatric sequelae even with increased risk for the development of chronic neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). Despite the lack of pharmaceutical-based therapies to manage the acute and chronic neurodegenerative syndromes, incretin-based therapy has become a new class of antidiabetic agent for potentially treating neurodegenerative diseases.
In this study, we investigated the neuroprotective effects of glucose-dependent insulinotropic polypeptide (GIP), an incretin similar to glucagon-like peptide-1 (GLP-1). We used the mild controlled cortical impact (mCCI) and intracranial injection of the neurotoxin 6-hydroxydopamine (6-OHDA) to create the progression of pathogenic events in neurodegeneration manifesting into altered behavioral outcomes. For acute neurodegeneration, we used the Morris water maze (MWM) and novel object recognition (NOR) tests to identify the putative therapeutic effects of GIP on cognitive function. Further, beam walking and the adhesive removal tests were used to evaluate sensory-motor functions in mTBI rats. For chronic neurodegeneration, the neuroprotection effects of GIP on 6-OHDA-lesioned rat model of PD were evaluated by apomorphine-induced contralateral rotations, as well as by locomotor and anxiety-like behaviors in open-field tests. Concentrations of human active and total GIP were measured in plasma during a five-day treatment period by enzyme-linked immunosorbent assay (ELISA) and were found to be within a clinically translatable range in two animal models of neurodegenerative disease. Lastly, we explored the underlying mechanisms using immunohistochemical (IHC) staining and western blot (WB) analyses in vivo.
In summary, GIP has neuroprotective effect on ameliorating mCCI- and 6-OHDA-induced behavioral deficits in neurodegenerative disease initiation and progression. In addition, GIP mitigated mTBI-induced neuroinflammatory changes in glial fibrillary acidic protein (GFAP), amyloid-b precursor protein (APP), and bone marrow tyrosine kinase gene in chromosome X (BMX) protein levels. These findings suggest GIP has significant benefits in managing neurodegeneration-related symptoms and represents a novel strategy for neurodegeneration treatment. |
