Dietary and supplemental vitamin E is absorbed and delivered to the liver, but of the various antioxidants with vitamin E activity, only alpha-tocopherol is preferentially recognized by the ...alpha-tocopherol transfer protein (alpha-TTP) and is transferred to plasma, while the other vitamin E forms (e.g., gamma-tocopherol or tocotrienols) are removed from the circulation. Hepatic alpha-TTP is required to maintain plasma and tissue alpha-tocopherol concentrations. The liver is the master regulator of the body's vitamin E levels in that it not only controls alpha-tocopherol concentrations, but also appears to be the major site of vitamin E metabolism and excretion. Vitamin Es are metabolized similarly to xenobiotics; they are initially omega-oxidized by cytochrome P450s, undergo several rounds of beta-oxidation, and then are conjugated and excreted. As a result of these various mechanisms, liver alpha-tocopherol and other vitamin E concentrations are closely regulated; thus, any potential adverse vitamin E effects are limited.
In addition to its role as a potent antioxidant, vitamin E is involved in a wide range of physiological processes, ranging from immune function and control of inflammation to regulation of gene ...expression and cognitive performance. Results from multiple studies suggest that poor nutritional status and higher prevalence of other oxidative stressors such as malaria and HIV infection predispose populations in developing countries for vitamin E deficiency. Although direct comparison between study outcomes is complicated by varied definitions of vitamin E deficiency, data trends indicate that children and the elderly are more vulnerable age groups and that men may be at higher risk for deficiency than women. Public health initiatives aimed at improving the vitamin E status of high-risk populations in developing countries would be prudent to counteract oxidative stress, improve immune function, and protect against neurologic and cognitive deficits. Additional research is needed to estabish dose—response relationships of various interventions and to develop cost-effective, culturally-appropriate, and targeted programs.
The Role of Vitamin E in Immunity Lee, Ga Young; Han, Sung Nim
Nutrients,
2018-Nov-01, 2018-11-01, 20181101, Letnik:
10, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Vitamin E is a fat-soluble antioxidant that can protect the polyunsaturated fatty acids (PUFAs) in the membrane from oxidation, regulate the production of reactive oxygen species (ROS) and reactive ...nitrogen species (RNS), and modulate signal transduction. Immunomodulatory effects of vitamin E have been observed in animal and human models under normal and disease conditions. With advances in understating of the development, function, and regulation of dendritic cells (DCs), macrophages, natural killer (NK) cells, T cells, and B cells, recent studies have focused on vitamin E's effects on specific immune cells. This review will summarize the immunological changes observed with vitamin E intervention in animals and humans, and then describe the cell-specific effects of vitamin E in order to understand the mechanisms of immunomodulation and implications of vitamin E for immunological diseases.
The aim of this article is to correct a very general error in scientific articles, in textbooks and in the Internet that has become an accepted fact. In this literature, the term "vitamin E″ is used ...for several similar molecules (both tocopherols and tocotrienols) that have never been shown to have vitamin property, i.e. a protective effect against the human deficiency disease. In fact, the name "vitamin E″ should only be used to define molecules that prevent the human deficiency disease "Ataxia with Vitamin E Deficiency" (AVED). Only one such molecule is known, α-tocopherol. This error may confuse consumers as well as medical doctors, who prescribe vitamin E without realizing that the current use of the name includes molecules of unknown, if not unwanted functions.
D-Alpha-tocopheryl polyethylene glycol 1000 succinate (Tocofersolan, Vedrop), has been developed in Europe to provide an orally bioavailable source of vitamin E in children with cholestasis. The aim ...was to analyze the safety/efficacy of Vedrop in a large group of children with chronic cholestasis.
Two hundred seventy-four children receiving Vedrop for vitamin E deficiency or for its prophylaxis were included from 7 European centers. Median age at treatment onset was 2 months and median follow-up was 11 months. Vedrop was prescribed at a daily dose of 0.34 mL/kg (25 IU/kg) of body weight. Three methods were used to determine a sufficient serum vitamin E status: vitamin E, vitamin E/(total cholesterol), vitamin E/(total cholesterol + triglycerides).
Before Vedrop therapy, 51% of children had proven vitamin E deficiency, 30% had normal vitamin E status and 19% had an unknown vitamin E status. During the first months of treatment, vitamin E status was restored in the majority of children with insufficient levels at baseline (89% had a normal status at 6 months). All children with a normal baseline vitamin E status had a normal vitamin E status at 6 months. Among children with an unknown vitamin E status at baseline, 93% had a normal vitamin E status at 6 months. A sufficient vitamin E status was observed in 80% of children with significant cholestasis (serum total bilirubin >34.2 μmol/L). No serious adverse reaction was reported.
Vedrop seems a safe and effective oral formulation of vitamin E that restores and/or maintains sufficient serum vitamin E level in the majority of children with cholestasis, avoiding the need for intramuscular vitamin E injections.
Growing evidence indicates that oxidative stress contributes markedly to endothelial dysfunction. The selenoenzyme glutathione peroxidase 4 (Gpx4) is an intracellular antioxidant enzyme important for ...the protection of membranes by its unique activity to reduce complex hydroperoxides in membrane bilayers and lipoprotein particles. Yet a role of Gpx4 in endothelial cell function has remained enigmatic.
To investigate the role of Gpx4 ablation and subsequent lipid peroxidation in the vascular compartment in vivo.
Endothelium-specific deletion of Gpx4 had no obvious impact on normal vascular homeostasis, nor did it impair tumor-derived angiogenesis in mice maintained on a normal diet. In stark contrast, aortic explants from endothelium-specific Gpx4 knockout mice showed a markedly reduced number of endothelial branches in sprouting assays. To shed light onto this apparent discrepancy between the in vivo and ex vivo results, we depleted mice of a second antioxidant, vitamin E, which is normally absent under ex vivo conditions. Therefore, mice were fed a vitamin E-depleted diet for 6 weeks before endothelial deletion of Gpx4 was induced by 4-hydroxytamoxifen. Surprisingly, ≈80% of the knockout mice died. Histopathological analysis revealed detachment of endothelial cells from the basement membrane and endothelial cell death in multiple organs, which triggered thrombus formation. Thromboembolic events were the likely cause of various clinical pathologies, including heart failure, renal and splenic microinfarctions, and paraplegia.
Here, we show for the first time that in the absence of Gpx4, sufficient vitamin E supplementation is crucial for endothelial viability.
Background
Equine neuroaxonal dystrophy/degenerative myeloencephalopathy (eNAD/EDM) is a neurodegenerative disease that primarily affects young, genetically predisposed horses that are deficient in ...vitamin E. Equine NAD/EDM has not previously been documented in Gypsy Vanner horses (GVs).
Objectives
To evaluate: (1) the clinical phenotype, blood vitamin E concentrations before and after supplementation and pedigree in a cohort of GV horses with a high prevalence of neurologic disease suspicious for eNAD/EDM and (2) to confirm eNAD/EDM in GVs through postmortem evaluation.
Animals
Twenty‐six GVs from 1 farm in California and 2 cases from the Midwestern U.S.
Methods
Prospective observational study on Californian horses; all 26 GVs underwent neurologic examination. Pre‐supplementation blood vitamin E concentration was assessed in 17‐ GVs. Twenty‐three were supplemented orally with 10 IU/kg of liquid RRR‐alpha‐tocopherol once daily for 28 days. Vitamin E concentration was measured in 23 GVs after supplementation, of which 15 (65%) had pre‐supplementation measurements. Two clinically affected GVs from California and the 2 Midwestern cases had necropsy confirmation of eNAD/EDM.
Results
Pre‐supplementation blood vitamin E concentration was ≤2.0 μg/mL in 16/17 (94%) of GVs from California. Post‐supplementation concentration varied, with a median of 3.39 μg/mL (range, 1.23‐13.87 μg/mL), but only 12/23 (52%) were normal (≥3.0 μg/mL). Normalization of vitamin E was significantly associated with increasing age (P = .02). Euthanized horses (n = 4) had eNAD/EDM confirmed at necropsy.
Conclusions and Clinical Importance
GVs could have a genetic predisposition to eNAD/EDM. Vitamin E supplementation should be considered and monitored in young GVs.
Vitamin E, antioxidant and nothing more Traber, Maret G.; Atkinson, Jeffrey
Free radical biology & medicine,
07/2007, Letnik:
43, Številka:
1
Journal Article
Recenzirano
Odprti dostop
All of the naturally occurring vitamin E forms, as well as those of synthetic
all-rac-α-tocopherol, have relatively similar antioxidant properties, so why does the body prefer α-tocopherol as its ...unique form of vitamin E? We propose the hypothesis that all of the observations concerning the in vivo mechanism of action of α-tocopherol result from its role as a potent lipid-soluble antioxidant. The purpose of this review then is to describe the evidence for α-tocopherol’s in vivo function and to make the claim that α-tocopherol’s major vitamin function, if not only function, is that of a peroxyl radical scavenger. The importance of this function is to maintain the integrity of long-chain polyunsaturated fatty acids in the membranes of cells and thus maintain their bioactivity. That is to say that these bioactive lipids are important signaling molecules and that changes in their amounts, or in their loss due to oxidation, are the key cellular events that are responded to by cells. The various signaling pathways that have been described by others to be under α-tocopherol regulation appear rather to be dependent on the oxidative stress of the cell or tissue under question. Moreover, it seems unlikely that these pathways are specifically under the control of α-tocopherol given that various antioxidants other than α-tocopherol and various oxidative stressors can manipulate their responses. Thus, virtually all of the variation and scope of vitamin E’s biological activity can be seen and understood in the light of protection of polyunsaturated fatty acids and the membrane qualities (fluidity, phase separation, and lipid domains) that polyunsaturated fatty acids bring about.
Polydopamine-based surface modification is a simple way to functionalize polymeric nanoparticle (NP) surfaces with ligands and/or additional polymeric layers. In this work, we developed DTX-loaded ...formulations using polydopamine-modified NPs synthesized using D-α-tocopherol polyethylene glycol 1000 succinate-poly(lactide) (pD-TPGS-PLA/NPs). To target liver cancer cells, galactosamine was conjugated on the prepared NPs (Gal-pD-TPGS-PLA/NPs) to enhance the delivery of DTX via ligand-mediated endocytosis. The size and morphology of pD-TPGS-PLA/NPs and Gal-pD-TPGS-PLA/NPs changed obviously compared with TPGS-PLA/NPs. In vitro studies showed that TPGS-PLA/NPs, pD-TPGS-PLA/NPs and Gal-pD-TPGS-PLA/NPs had similar release profiles of DTX. Both confocal laser scanning microscopy and flow cytometric results showed that coumarin 6-loaded Gal-pD-TPGS-PLA/NPs had the highest cellular uptake efficiency in liver cancer cell line HepG2. Moreover, DTX-loaded Gal-pD-TPGS-PLA/NPs inhibited the growth of HepG2 cells more potently than TPGS-PLA/NPs, pD-TPGS-PLA/NPs, and a clinically available DTX formulation (Taxotere®). The in vivo biodistribution experiments show that the Gal-pD-TPGS-PLA/NPs are specifically targeted to the tumor. Furthermore, the in vivo anti-tumor effects study showed that injecting DTX-loaded Gal-pD-TPGS-PLA/NPs reduced the tumor size most significantly on hepatoma-bearing nude mice. These results suggest that Gal-pD-TPGS-PLA/NPs prepared in the study specifically interacted with the hepatocellular carcinoma cells through ligand-receptor recognition and they may be used as a potentially eligible drug delivery system targeting liver cancers.
Polydopamine-based surface modification is a simple way to functionalize polymeric nanoparticle surfaces with ligands and/or additional polymeric layers. In this work, we developed docetaxel (DTX)-loaded formulations using polydopamine-modified NPs synthesized from D-α-tocopherol polyethylene glycol 1000 succinate-poly(lactide) (pD-TPGS-PLA/NPs). To target liver cancer cells, galactosamine was conjugated on the prepared NPs (Gal-pD-TPGS-PLA/NPs) to enhance the delivery of DTX via ligand-mediated endocytosis. Both confocal laser scanning microscopy and flow cytometric results showed that coumarin 6-loaded Gal-pD-TPGS-PLA/NPs had the highest cellular uptake efficiency for liver cancer cell line HepG2. The in vivo biodistribution experiments show that the Gal-pD-TPGS-PLA/NPs are specifically targeted to the tumor. Furthermore, the in vivo anti-tumor effects study showed that injecting DTX-loaded Gal-pD-TPGS-PLA/NPs reduced the tumor size most significantly on hepatoma-bearing nude mice. These results suggest that Gal-pD-TPGS-PLA/NPs prepared in the study specifically interacted with the hepatocellular carcinoma cells through ligand-receptor recognition and they could be used as a potentially eligible drug delivery system targeting liver cancers.
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