Laboratory of Molecular Biomedicine, Institute of Bioscience, Universiti Putra Malaysia, Serdang 43400 UPM, Selangor, Malaysia.
Department of Medical Biochemistry, Faculty of Basic Medical Sciences, Usmanu Danfodiyo University, Sokoto, Nigeria.
Nutrients. 2020 Feb 18;12(2):521. doi: 10.3390/nu12020521.
Several natural products have been reported to elicit beneficial effects against neurodegenerative disorders due to their vitamin E contents. However, the neuroprotective efficacy of palm oil or its tocotrienol-rich fraction (TRF) from the pre-clinical cell and animal studies have not been systematically reviewed.
The protocol for this systematic review was registered in "PROSPERO" (CRD42019150408). This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The Medical Subject Heading (MeSH) descriptors of PubMed with Boolean operators were used to construct keywords, including ("Palm Oil"[Mesh]) AND "Nervous System"[Mesh], ("Palm Oil"[Mesh]) AND "Neurodegenerative Diseases"[Mesh], ("Palm Oil"[Mesh]) AND "Brain"[Mesh], and ("Palm Oil"[Mesh]) AND "Cognition"[Mesh], to retrieve the pertinent records from PubMed, Scopus, Web of Science and ScienceDirect from 1990 to 2019, while bibliographies, ProQuest and Google Scholar were searched to ensure a comprehensive identification of relevant articles. Two independent investigators were involved at every stage of the systematic review, while discrepancies were resolved through discussion with a third investigator.
All of the 18 included studies in this review (10 animal and eight cell studies) showed that palm oil and TRF enhanced the cognitive performance of healthy animals. In diabetes-induced rats, TRF and α-tocotrienol enhanced cognitive function and exerted antioxidant, anti-apoptotic and anti-inflammatory activities, while in a transgenic Alzheimer's disease (AD) animal model, TRF enhanced the cognitive function and reduced the deposition of β-amyloid by altering the expression of several genes related to AD and neuroprotection. In cell studies, simultaneous treatment with α-tocotrienols and neurotoxins improved the redox status in neuronal cells better than ϒ- and δ-tocotrienols. Both pre-treatment and post-treatment with α-tocotrienol relative to oxidative insults were able to enhance the survival of neuronal cells via increased antioxidant responses.
Palm oil and its TRF enhanced the cognitive functions of healthy animals, while TRF and α-tocotrienol enhanced the cognitive performance with attenuation of oxidative stress, neuroinflammation and apoptosis in diabetes-induced or transgenic AD animal models. In cell studies, TRF and α-tocotrienol exerted prophylactic neuroprotective effects, while α-tocotrienol exerted therapeutic neuroprotective effects that were superior to those of ϒ- and δ-tocotrienol isomers.
由于其维生素 E 含量，几种天然产物已被报道具有对抗神经退行性疾病的有益作用。然而，棕榈油或其富含生育三烯酚（TRF）的馏分（TRF）在临床前细胞和动物研究中的神经保护功效尚未得到系统评价。
本系统评价的方案已在“PROSPERO”（CRD42019150408）中注册。本综述遵循系统评价和荟萃分析的首选报告项目（PRISMA）指南。使用 PubMed 中的医学主题词（MeSH）描述符和布尔运算符来构建关键字，包括（“棕榈油”[Mesh]）和“神经系统”[Mesh]，（“棕榈油”[Mesh]）和“神经退行性疾病”[Mesh]，（“棕榈油”[Mesh]）和“大脑”[Mesh]，和（“棕榈油”[Mesh]）和“认知”[Mesh]，从 1990 年到 2019 年从 PubMed、Scopus、Web of Science 和 ScienceDirect 检索相关记录，同时检索书目、ProQuest 和 Google Scholar 以确保全面识别相关文章。两名独立的调查员参与了系统评价的各个阶段，如有分歧则通过与第三名调查员讨论解决。
本综述中纳入的 18 项研究（10 项动物研究和 8 项细胞研究）均表明，棕榈油和 TRF 提高了健康动物的认知表现。在糖尿病诱导的大鼠中，TRF 和 α-生育三烯酚增强了认知功能，并发挥了抗氧化、抗凋亡和抗炎作用，而在转基因阿尔茨海默病（AD）动物模型中，TRF 通过改变与 AD 和神经保护相关的几种基因的表达来增强认知功能并减少 β-淀粉样蛋白的沉积。在细胞研究中，α-生育三烯酚与神经毒素的同时治疗比γ-和δ-生育三烯酚更好地改善神经元细胞的氧化还原状态。与氧化损伤相比，α-生育三烯酚的预处理和后处理均能通过增加抗氧化反应来增强神经元细胞的存活。
棕榈油及其 TRF 提高了健康动物的认知功能，而 TRF 和 α-生育三烯酚在糖尿病诱导或转基因 AD 动物模型中增强了认知表现，并减轻了氧化应激、神经炎症和细胞凋亡。在细胞研究中，TRF 和 α-生育三烯酚发挥了预防神经保护作用，而 α-生育三烯酚发挥了治疗神经保护作用，优于γ-和δ-生育三烯酚异构体。
