Journal Article

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

Ismail, Maznah, Ooi, Der Jiun, Khaza’ai, Huzwah, Imam, Mustapha Umar, Aljaberi, Musheer A., Idrus, Zulkifli, Shamsudin, Mad Nasir, Alsalahi, Abdulsamad

2020

Overview

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.

• Publisher: MDPI AG,MDPI
• Subject: 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