What is topical vitamin E used for?

Vitamin E is an essential vitamin that should be consumed in the diet in adequate amounts to promote optimal health outcomes.  However, it is also used in some cosmetics and topical skin care products.  What is topical vitamin E, what is it used for, and are there any side effects?

Read More

Involvement of PD-L1-mediated Tumor Intrinsic Signaling and Immune Suppression in Tumorigenic Effect of α-Tocopherol

Zhenou Sun, Shutao Yin, Chong Zhao, Li Hong Fan, Hongbo Hu

Carcinogenesis . 2021 Oct 17;bgab096. doi: 10.1093/carcin/bgab096. Online ahead of print.

Abstract

Numerous studies have shown that the different isoforms vitamin E have distinct activity on carcinogenesis. α-Tocopherol (α-T), the most abundant vitamin E in certain types of food and animal tissues, has demonstrated a cancer-promoting effect in a number of human clinical trials and pre-clinical studies, whereas the γ- and δ- forms of Tocopherols and Tocotrienols have exhibited significant anticancer effect in various pre-clinical studies. However, the mechanisms underlying the tumorigenic effect of α-T have not yet been fully understood. In the present study, we found that α-T was able to activate Programmed death-ligand 1 (PD-L1)-mediated tumor-intrinsic signaling and immune suppression via JAK/STAT3-dependent transcriptional and ERK-dependent posttranscriptional mechanism. In line with PD-L1 induction, α-T treatment increased cancer cell viability in vitro and promoted tumor growth in LLC xenograft mouse model. The findings of the present study for the first time provided evidence that PD-L1-mediated tumor-intrinsic and immune escape mechanism contributed to the tumorigenic effect of α-T.

Read More

Cytotoxicity, cellular uptake, and metabolism to short-chain metabolites of 11′-α-tocomonoenol is similar to RRR-α-tocopherol in HepG2 cells

Alexander Montoya-Arroyo, Tanja Wagner, Nadine Sus, Marco Müller, Alexander Kröpfl, Walter Vetter, Jan Frank

Free Radic Biol Med . 2021 Oct 16;S0891-5849(21)00768-1. doi: 10.1016/j.freeradbiomed.2021.10.018. Online ahead of print.

Abstract

Contrary to the major vitamin E congener α-tocopherol, which carries a saturated sidechain, and α-tocotrienol, with a threefold unsaturated sidechain, little is known about the intracellular fate of α-tocomonoenol, a minor vitamin E derivative with a single double bond in C11′-position of the sidechain. We hypothesized that, due to structural similarities, the uptake and metabolism of α-tocomonoenol will resemble that of α-tocopherol. Cytotoxicity, cellular uptake of α-tocomonoenol, α-tocopherol and α-tocotrienol and conversion into the short-chain metabolites αCEHC and αCMBHC were studied in HepG2 cells. α-Tocomonoenol did not show significant effects on cell viability and its uptake was similar to that observed for α-tocopherol and significantly lower than for α-tocotrienol. α-Tocomonoenol was mainly metabolized to αCMBHC in liver cells, but to a lower extent than α-tocotrienol, while α-tocopherol was not metabolized in quantifiable amounts at all. In summary, the similarities in the cytotoxicity, uptake and metabolism of α-tocomonoenol and α-tocopherol suggest that this minor vitamin E congener deserves more attention in future research with regard to its potential vitamin E activity.

Read More

α-tocopherol, a slow-binding inhibitor of acetylcholinesterase

Irina Zueva, Sofya Lushchekina, Polina Shulnikova, Oksana Lenina, Konstantin Petrov, Elena Molochkina, Patrick Masson

Chem Biol Interact . 2021 Oct 1;348:109646. doi: 10.1016/j.cbi.2021.109646. Epub 2021 Sep 8.

Abstract

Acetylcholinesterase (AChE) is reversibly inhibited by α-tocopherol (α-T). Steady state kinetic analysis shows that α-T is a mixed slow-binding inhibitor of type A of human enzyme (Kci = 0.49 μM; Kui = 1.6 μM) with a residence time of 2 min on target. Molecular dynamics (MD) simulations support this mechanism, and indicate that α-T first forms multiple non-specific interactions with AChE surface near the gorge entrance, then binds to the peripheral side with alkylene chain slowly sliding down the gorge, inducing no significant conformational change. α-T slightly modulates the progressive inhibition of AChE by the cyclic organophosphorus, cresyl saligenylphosphate, accelerating the fast pseudo-first order process of phosphorylation. A moderate accelerating effect of α-T on phosphorylation by paraoxon was also observed after pre-incubation of AChE in the presence of α-T. This accelerating effect of α-T on ex vivo paraoxon-induced diaphragm muscle weakness was also observed. The effect of α-T on AChE phosphylation was interpreted in light of molecular modeling results. From all results it is clear that α-T does not protect AChE against phosphylation by organophosphorus.

Read More

Different functions of vitamin E homologues in the various types of cell death induced by oxysterols

Atsuki Suzuki, Yasuomi Urano, Tomohisa Ishida, Noriko Noguchi

Free Radic Biol Med . 2021 Oct 12;176:356-365. doi: 10.1016/j.freeradbiomed.2021.10.008. Online ahead of print.

Abstract

24(S)-Hydroxycholesterol (24S-OHC) and 25-hydroxycholesterol (25-OHC) are produced by cholesterol 24-hydroxylase and cholesterol 25-hydroxylase, respectively. The purpose of the present study was to determine the type of cell death induced by these oxysterols in neuronal cells, hepatic cells, and keratinocytes, and to elucidate the inhibitory effect of vitamin E homologues on various types of cell death. In human neuronal cells (SH-SY5Y cells), 24S-OHC and 25-OHC caused a cell death that was independent of caspase activation. We reported previously that the esterification of 24S-OHC by acyl-CoA:cholesterol acyltransferase 1 (ACAT1) and the resulting formation of a lipid droplet (LD)-like structure are responsible for the 24S-OHC-induced neuronal cell death. Here, we found that 25-OHC also induced ACAT1-mediated 25-OHC esterification and LD formation in neuronal cells. 25-OHC-induced cell death was inhibited by α-tocopherol (α-Toc) but not by α-tocotrienol (α-Toc3), as observed for 24S-OHC-induced cell death in SH-SY5Y cells. In human hepatic cells (HepG2 cells), these oxysterols caused a cell death that was caspase- and oxysterol-esterification-independent. This cell death was suppressed by both α-Toc and α-Toc3, suggesting the involvement of free-radical-mediated lipid peroxidation in the cell death induced by these oxysterols in hepatic cells. In human keratinocytes (HaCaT cells), these oxysterols caused a caspase-dependent but oxysterol-esterification-independent cell death that was inhibited by α-Toc but not by α-Toc3. These results suggest that α-Toc and α-Toc3 act as radical-scavenging antioxidants against oxysterol-induced cell death in the same way in hepatic cells, whereas their behavior is different in inhibition of cell death in neuronal cells and keratinocytes. Collectively, these results demonstrated that 24S-OHC and 25-OHC induced the same type of cell death in each of the cell types examined, and that α-Toc and α-Toc3 exerted different effects, depending on the type of cell death.

Read More

Pressurized liquid extraction to obtain chia seeds oils extracts enriched in tocochromanols. Nanoemulsions approaches to preserve the antioxidant potential

Lucía Castro-Vázquez, Virginia Rodríguez-Robledo, María Plaza-Oliver, Manuel J Santander-Ortega, M Victoria Lozano, Joaquín González, Noemí Villaseca, Pilar Marcos, M Mar Arroyo-Jiménez

J Food Sci Technol . 2021 Oct;58(10):4034-4044. doi: 10.1007/s13197-020-04866-9. Epub 2021 Jan 5.

Abstract

The objective of this study was to use accelerated-solvent-extraction to achieve antioxidant extracts from chia seeds oils, enriched in tocopherols and tocotrienols, namely tocochromanols. Nanotechnology applications have been also incorporated to develop an innovative formulation of chia seeds oil nanoemulsion that preserve its antioxidant potential after conditions of oxidative stress. Chia seeds oils proved to be a valuable source of tocochromanols, from 568.84 to 855.98 μg g-1, depending on the geographical provenance. Quantitative data obtained by LC-DAD-ESI-MS/MS showed outstanding levels of γ-Tocopherol, over 83%, followed far behind by Tocopherols-(α, β, δ) and Tocotrienols-(α, β, δ, γ)-tocotrienols. The characteristic tocochromanols fingerprint of chia seeds oils was positively correlated with the FRAP and DPPH antioxidant activity of the extracts (between 18.81 and 138.48 mg Trolox/g). Formulation of the Chia seeds oils as nanoemulsions did not compromised the antioxidant properties of fresh extracts. Interestingly, nanoemulsions retained about the 80% of the initial antioxidant capacity after UV-induced stress, where the non-emulsified oils displayed a remarkable reduction (50-60%) on its antioxidant capacity under the same conditions. These antioxidant chia seeds formulations can constitute a promising strategy to vectorizing vitamin E isomers, in order to be used for food fortification, natural additives and to increase the self-life of food products during packing.

Read More

Vitamin E: A potential preventive approach against dental erosion-an in vitro short-term erosive study

Daniela Rios , Ana Paula Boteon, Camilla Cristina Lira Di Leone, Tainara Tonon Castelluccio, Fernanda Lyrio Mendonça, Franciny Querobim Ionta, Marília Afonso Rabelo Buzalaf, Thiago Saads Carvalho

J Dent . 2021 Oct;113:103781. doi: 10.1016/j.jdent.2021.103781. Epub 2021 Aug 13.

Abstract

Objectives: This study evaluated the in vitro effect of different components of palm oil on enamel in a short-term erosive challenge.

Methods: The acquired enamel pellicle (AEP) was previously formed in situ for 2 h. Subsequently, the bovine enamel blocks were treated in vitro according to following solutions: G1-palm oil; G2-85% tocotrienol solution; G3-oily vitamin E; G4-oily vitamin A; G5-deionized water (negative control); G6-stannous-containing solution (Elmex® Erosion Protection Dental Rinse) (positive control). After application of the treatment solutions (500 µl, 30 s), the blocks were immersed in 0.5% citric acid (pH 2.4) during 30 s (initial erosion). The response variable was the percentage of surface hardness loss. Data were analyzed by one-way ANOVA and Fisher’s Test (p < 0.05).

Results: The positive control (G6), palm oil (G1) and oily vitamin E (G3) groups presented the lowest percentage of surface hardness loss, and were statistically different from the negative group (G5) (p < 0.05), and no differences were found between these three groups. The 85% tocotrienol solution (G2) and oily vitamin A groups (G4) were not different to the negative control group.

Conclusions: Stannous-containing positive control (Elmex® Erosion Protection), palm oil and oily Vitamin E were able to protect enamel against the erosive challenge performed in this in vitro study. In addition, vitamin E is probably the key ingredient of palm oil responsible for preventing enamel erosion.

Clinical significance: Vitamin E presented similar preventive effect to a commercial mouthwash stannous-containing solution (Elmex® Erosion Protection) against initial erosion and, it can be considered as a promising natural alternative for the formulations of solutions aiming to prevent erosive tooth wear.

Read More

Vitamin E as an essential micronutrient for human health: Common, novel, and unexplored dietary sources

Fereidoon Shahidi, Ana Clara C Pinaffi-Langley, Jocelyn Fuentes, Hernán Speisky, Adriano Costa de Camargo

Free Radic Biol Med . 2021 Oct 2;176:312-321. doi: 10.1016/j.freeradbiomed.2021.09.025. Online ahead of print.

Abstract

Vitamin E comprises a group of vitamers that includes tocopherols and tocotrienols. They occur in four homologues according to the number and position of methyl groups attached to the chromanol ring. Vitamin E, a liposoluble antioxidant, may participate as an adjuvant in the prevention and treatment of cardiovascular, neurological, and aging-related diseases. Furthermore, vitamin E has applications in the food industry as a natural additive. In this contribution, the most recent information on the dietary sources of vitamin E, including common, novel, and unexplored sources, is presented. Common edible oils, such as those of corn, olive, palm, rice bran, and peanut, represent the most prominent sources of vitamin E. However, specialty and underutilized oils such as those obtained from tree nuts, fruit seeds, and by-products, emerge as novel sources of this important micronutrient. Complementary studies should examine the tocotrienol content of vitamin E dietary sources to better understand the different biological functions of these vitamers.

Read More