Vitamin E: Not only a single stereoisomer

The recent publication by Azzi and colleagues puts forth the argument that only RRR-α-tocopherol should be considered as vitamin E from a physiological point of view. They base their argument primarily on the assertion that only this form has been used to treat stark vitamin E deficiency in humans (known as AVED, or Ataxia with Vitamin E Deficiency). Azzi et al. also argue that other chemically similar molecules, such as tocopherols other than α-tocopherol and tocotrienols do not provide vitamin E activity. Azzi and colleagues are correct on this second point. An investigation into the biological activities of vitamin E, and the mechanisms behind these activities, confirms that physiological vitamin E activity is limited to certain α-tocopherol forms. However, it is also clear that these activities are not restricted only to the RRR-form but include other 2R-forms as well. Indeed, the α-tocopherol transfer protein (α-TTP), which is critical to mediate vitamin E trafficking and biological activity, and genetic defects of which lead to vitamin E deficiency, binds well to all 2R-forms of α-tocopherol. Furthermore, both RRR-α-tocopherol and the other 2R-forms are maintained in human plasma and distributed to tissues and organs, whereas the 2S-stereoisomers are excreted quickly. As such, in recent years the definition of vitamin E including both 2R- and RRR-α-tocopherol has gained both broad scientific and regulatory acceptance. Consistent with this understanding, we provide evidence that AVED has indeed been treated successfully with forms in addition to RRR-α-tocopherol, again arguing against the restriction of the definition to RRR-α-tocopherol only. Finally, we provide evidence against any safety concerns utilizing the currently accepted definition of vitamin E.

Low density lipoprotein immunoapheresis does not increase plasma lipid peroxidation products in vivo

Extracorporeal elimination of low density lipoprotein (LDL) is frequently used in drug-resistant hypercholesterolemia. LDL-immunoapheresis selectively removes LDL and lipoprotein(a) [Lp(a)] from plasma. Lipid peroxidation is one unwanted side effect, that occurs during extracorporeal plasma treatment. The purpose of this study was to investigate the effect of LDL immunoapheresis on lipid peroxidation. Before and after a single LDL-immunoapheresis treatment, plasma concentrations of lipid hydroperoxides, determined with two different spectophotometric assays, thiobarbituric acid-reacting substances (TBARS), determined spectrophotometrically and malondialdehyde (MDA), determined by an MDA-TBA/HPLC method, were measured in 13 hypercholesterolemic patients. In addition MDA was also determined in the eluate of the apheresis column. Before treatment, plasma cholesterol and LDL cholesterol concentrations were significantly higher in patients than in healthy control subjects, as were the lipid peroxidation products. LDL-immunoapheresis treatment of the patients led to significant decreases in total cholesterol (69+/-8%), LDL-cholesterol (79+/-7%), HDL-cholesterol (35+/-17%), triglycerides (38+/-21%), apolipoprotein-B (77+/-6%), apolipoprotein-A1 (25+/-5%) and Lp(a) concentrations (76+/-10%). Changes in plasma lipid peroxide concentrations (17+/-8 nmol/l before vs. 14+/-5 nmol/l after treatment) were not significant, neither were those in TBARS (3. 0+/-2.6 micromol/l vs. 2.3+/-1.3 micromol/l) or MDA concentrations (1.03+/-0.17 micromol/l vs. 1.0+/-0.20 micromol/l). Patients with high baseline values showed a decrease, whereas others did not. MDA was present (0.57+/-0.13 micromol/l) in the eluate of the apheresis column, suggesting that, along with LDL, lipid peroxidation products are also removed. From these results we conclude that a single LDL-immunoapheresis treatment effectively reduces LDL and Lp(a) in the absence of increases in plasma lipid peroxidation products.

[Diagnosis and treatment of celiac disease--what is the status in 1990?]

Summarizing the development of experiences and discussions of the last 20 years, a working group of the ESPGAN has recently updated the criteria of diagnosis of coeliac disease. The reliable finding of the initial typical mucosal lesion in the untreated patient is a hallmark of the disease and, if followed by an unequivocal clinical response to a gluten free diet, can be considered as final evidence for the diagnosis. Gluten challenges should be limited to cases without this evidence. High levels of antigliadin- and antireticulin- or or antiendomysium antibodies are supportive for the diagnosis but cannot substitute biopsy proof of the disease. The importance of a very long term strict gluten free diet in coeliac disease is established by recent evidence showing that in such cases there is no increased risk of malignancy.