VESS 3 IL 1.1:
Vitamin E: gene regulation effects and lipid metabolism
Prof. Maret Traber | Oregon State University | United States
Vitamin E (VitE) is recognized to have a significant role in fetal development. We use the alpha-tocopherol-deficient zebrafish embryo (E– embryos) to study VitE implications in fetal development, especially neurogenesis. Early development gene expression networks are highly conserved between the zebrafish and humans. We showed in zebrafish embryos that the alpha-tocopherol transfer protein (TTP) gene (Ttpa) increases 7-fold by 12 hours post-fertilization (hpf) and remains elevated. Ttpa knockdown is lethal within 24 hpf. It is found in in the yolksac, the developing brain, eyes, and tail bud. Since TTP is needed for trafficking alpha-tocopherol, these data emphasize VitE’s importance in critical tissues. Using mass spectrometry (lipidomics and metabolomics), we discovered the occurrence of increased lipid peroxidation (LPO) especially of phosphatidyl choline with docosahexaenoic acid (DHA-PC) in E– embryos. VitE specifically prevents LPO by acting as a peroxyl radical scavenger swiftly terminating LPO chain reactions. However, this process consumes both energy (NADPH) and glutathione, as well as dysregulating phospholipid metabolism as evidenced by altered lysophospholipid, choline and betaine levels. E– embryos also display altered gene expression associated with 1-carbon metabolism, energy metabolism, anabolic reactions, and gene transcription. Thus, VitE deficiency likely impacts choline and its interactions with the methionine and folic acid cycles resulting not only in impacts in neurogenesis, but also potential impacts on epigenetic regulation in the developing embryo. We also found that mTOR, which is critical in regulating metabolic function, embryonic patterning and neural stem cell differentiation, is also dysregulated in E– embryos. Our findings provide a critical link to understanding the downstream consequences of increased LPO and how VitE acts as a lynchpin to prevent the metabolic dysregulation caused by DHA-PC depletion in embryos. These data are also applicable to other cellular environments and suggest why VitE is a critical nutrient for humans.
VESS 3 IL 1.2:
Structures, activities and analytical determination of Vitamin E and its metabolites
Prof. Dr. Marc Birringer | Hochschule Fulda University of Applied Sciences | Germany
Plant and marine organisms developed numerous natural products based on a 6-hydroxychromal ring structure. Most of the molecules are diterpenoids, among them tocopherols and tocotrienols; the biological active forms of vitamin E. The structural variability of the compounds is remarkable, since side chain modifcations by oxidation and/or cyclization occur widely, especially in marine organisms.
Cytochrome P450 enzymes are most likely responsible for the initial oxidation to epoxy-, hydroxy- and carboxy-derivatives, respectively. Besides the well investigated tocopherols and tocotrienols, side chain modified 6-hydroxychromanols are rarely studied for their biological activities and might have a high potential as anti-cancer and/or anti-inflammatory drug lead structure. A specific class of side chain modified 6-hydroxychromanols belong to the human vitamin E metabolism. Long chain metabolites of alpha- and delta-tocopherol has been investigated in the recent years and open new avenues in vitamin E research. Besides chemical syntheses approaches toward the long chain metabolites, we developed analytical methods to determine the metabolites in human plasma and cell cultures. Recently, a stable isotope dilution method was established to simultaneously determine tocopherol long chain metabolites and tocopherols via LC-MS. We were able to quantify nanomolar metabolite concentrations of metabolites besides micromolar concentrations of tocopherols in the same chromatographic run.