title: Do tocotrienols have potential as neuroprotective dietary factors?
abstract: Tocotrienols (T(3)) belong to the family of vitamin E compounds (α-, β-, γ-, δ-tocopherols and -tocotrienols) and have unique biological properties that make them potential neuroprotective dietary factors. In addition to their antioxidant activity, T(3) at micromolar concentrations exert cholesterol-lowering activities in cells, animal models and some, but not all, human studies by means of inhibition of the activity of the rate-limiting enzyme in cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A reductase. At lower concentrations (∼10 nmol/L), T(3) modulate signalling pathways involved in neuronal cell death in cell culture experiments. Targets of T(3) include prenyl transferases, non-receptor tyrosine kinase, phospholipase A(2), 12-lipoxygenase, cyclooxygenase-2, and nuclear factor κB. The low bioavailability and rapid excretion of T(3) represents a major hurdle in their preventive use. Fasting plasma concentrations, even after supplementation with high doses, are below 1 μmol/L. T(3) bioavailability may be enhanced by ingestion with a high-fat meal, self-emulsifying drug delivery systems, or phytochemicals that inhibit T(3) metabolism and excretion. T(3) have no known adverse effects when consumed as part of a normal diet and the studies reviewed here support the notion that they may have potential as neuroprotective agents. However, experiments in relevant animal models and randomised human intervention trials addressing the neuroprotection mediated by T(3) are scarce and, thus, highly warranted.
authors.affiliation: Institute of Biological Chemistry and Nutrition, University of Hohenheim, Stuttgart, Germany. jan.frank@nutrition-research.de
authors.forename: Jan
authors.initials: J
authors.lastname: Frank
authors.forename: Xiao Wei Dawn
authors.initials: XW
authors.lastname: Chin
authors.forename: Charlotte
authors.initials: C
authors.lastname: Schrader
authors.forename: Gunter P
authors.initials: GP
authors.lastname: Eckert
authors.forename: Gerald
authors.initials: G
authors.lastname: Rimbach
mesh_terms: D000375:Aging / Q000187:drug effects* / Q000502:physiology; D000544:Alzheimer Disease / Q000178:diet therapy* / Q000503:physiopathology / Q000517:prevention & control; D000818:Animals; D019587:Dietary Supplements / Q000592:standards*; D006801:Humans; D018696:Neuroprotective Agents / Q000494:pharmacology* / Q000627:therapeutic use; D024508:Tocotrienols / Q000378:metabolism / Q000493:pharmacokinetics* / Q000627:therapeutic use
chemical_list: D018696:Neuroprotective Agents; D024508:Tocotrienols