Neel Chowdhury
Palm oil has a pretty bad reputation. The product of this hard-shell red fruit, harvested primarily on plantations in Southeast Asia, is typically used as cheap cooking oil for fried foods like noodles and curry puffs. Indeed, by the time the palm oil is processed, much of its nutritional value is destroyed. And the fact that it can congeal at room temperature makes it even look extra artery clogging.
Tocotrienol (T3) is an important phytonutrient found in rice bran and palm oil. T3 has gained much interest for lipid lowering effects, especially for cholesterol (Cho) by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A reductase. Also, usefulness of T3 in improving triglyceride (TG) profiles has been suggested, but its efficacy and mechanism have been unclear. We investigated how T3 decreases TG concentration in cultured cells and animals. In a cell culture study, human hepatoma cells (HepG2) were incubated in a control or a fat (1 mM oleic acid)-loaded medium containing γ-T3 for 24 h. We found that 10-15 μM γ-T3 inhibited cellular TG accumulation significantly, especially in the fat-loaded medium. This manifestation was supported by mRNA and protein expressions of fatty acid synthase, carnitine palmitoyltransferase 1, and cytochrome P450 3A4. In concordance with these results, rice bran T3 supplementation to F344 rats (5 or 10 mg T3/day/rat) receiving a high fat diet for 3 weeks significantly reduced TG and the oxidative stress marker (phospholipid hydroperoxides, PLOOH) in the liver and blood plasma. T3 supplementation did not show changes in the Cho level. These results provided new information and the mechanism of the TG-lowering effect of T3. The lipid lowering effects of dietary T3 might be mediated by the reduction of TG synthesis.
γ-Tocotrienol (γ-T3), a member of the vitamin E family, has been reported to possess an anticancer activity. γ-T3 is a lipophilic compound with low oral bioavailability. Previous studies showed that γ-T3 has low intestinal permeability. Thus, we have hypothesized that enhancing γ-T3 intestinal permeability will increase its oral bioavailability. Solid lipid nanoparticles (SLN) were tested as a model formulation to enhance γ-T3 permeability and bioavailability. γ-T3 intestinal permeability was compared using in situ rat intestinal perfusion, followed by in vivo relative oral bioavailability studies. In addition, in vitro cellular uptake of γ-T3 from SLN was compared to mixed micelles (MM) in a time and concentration-dependent studies. To elucidate the uptake mechanism(s) of γ-T3 from SLN and MM the contribution of NPC1L1 carrier-mediated uptake, endocytosis and passive permeability were investigated. In situ studies demonstrated SLN has tenfold higher permeability than MM. Subsequent in vivo studies showed γ-T3 relative oral bioavailability from SLN is threefold higher. Consistent with in situ results, in vitro concentration dependent studies revealed γ-T3 uptake from SLN was twofold higher than MM. In vitro mechanistic characterization showed that while endocytosis contributes to γ-T3 uptake from both formulations, the reduced contribution of NPC1L1 to the transport of γ-T3, and passive diffusion enhancement of γ-T3 are primary explanations for its enhanced uptake from SLN. In conclusion, SLN successfully enhanced γ-T3 oral bioavailability subsequent to enhanced passive permeability.
Ethanol-induced damage in the developing brain may result in cognitive impairment including deficits on neuropsychological tests of learning, memory and executive function, yet the underlying mechanisms remain elusive. In the present study we investigated the protective effect of tocotrienol against cognitive deficit, neuroinflammation and neuronal apoptosis in rat pups postnatally exposed to ethanol. Pups were administered ethanol (5g/kg, 12% v/v) by intragastric intubation on postnatal days 7, 8 and 9. Ethanol-exposed pups showed significant memory impairment in Morris water maze task as evident from increase in escape latency and total distance travelled to reach the hidden platform. Time spent in target quadrant, % total distance traversed in target quadrant and frequency of appearance in target quadrant was also significantly decreased in ethanol exposed pups in probe trial. Poor memory retention was exhibited by ethanol-exposed pups in elevated plus maze test also. Impaired cognition was associated with significantly enhanced acetylcholinesterase activity, increased neuroinflammation (oxidative-nitrosative stress, TNF-α, IL-1β and TGF-β1) and neuronal apoptosis (NF-κβ and Caspase-3) in different brain regions of ethanol-exposed pups. Co-administration with tocotrienol significantly ameliorated all the behavioral, biochemical and molecular alterations in the different brain regions of ethanol exposed pups. The current study thus demonstrates the possible involvement of NF-κβ mediated apoptotic signaling in cognitive deficits associated with postnatal ethanol exposure in rats and points to the potential of tocotrienol in the prevention of cognitive deficits in children with fetal alcohol spectrum disorders (FASDs).