Safety and Neuroprotective Efficacy of Palm Oil and Tocotrienol-Rich Fraction from Palm Oil: A Systematic Review

• Published in: Nutrients Vol. 12; no. 2; p. 521
• Main Authors: Ismail, Maznah, Alsalahi, Abdulsamad, Imam, Mustapha Umar, Ooi, Der Jiun, Khaza’ai, Huzwah, Aljaberi, Musheer A., Shamsudin, Mad Nasir, Idrus, Zulkifli
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 18.02.2020; MDPI
• Subjects: Alzheimer disease; Alzheimer Disease - metabolism; Alzheimer Disease - psychology; Alzheimer Disease - therapy; Amyloid beta-Peptides - metabolism; animal models; Animals; anti-inflammatory activity; Anti-Inflammatory Agents; antioxidant activity; Antioxidants; apoptosis; Bias; Bibliographic literature; brain; Cells, Cultured; Chemical Fractionation; cognition; Cognition - drug effects; Disease Models, Animal; Gene expression; genes; genetically modified organisms; heading; Humans; Intervention; isomers; meta-analysis; Mice; Neurodegeneration; neurodegenerative diseases; neurons; Neuroprotective Agents; neuroprotective effect; neurotoxins; nutrients; Oils & fats; oxidative stress; Oxidative Stress - drug effects; Palm Oil - chemistry; Palm Oil - pharmacology; Palm Oil - therapeutic use; Phytotherapy; pretreatment; Proteins; protocols; Rats; Review; Systematic review; therapeutics; Tocotrienols - isolation & purification; Tocotrienols - pharmacology; Tocotrienols - therapeutic use; Vegetable oils; vitamin E; neurodegeneration; cognition; neuroprotection; tocotrienol; tocotrienol-rich fraction; palm oil
• ISSN: 2072-6643; 2072-6643
• DOI: 10.3390/nu12020521

Background: 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. Methods: 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. Results: 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 γ- 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. Conclusions: 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 γ- and δ-tocotrienol isomers.