Enhancing Effect Of Vitamin Research Articles

Calcipotriol Enhances Efficacy of Imatinib and Nilotinib on Cells Derived from Plexiform Neurofibroma.

Plexiform neurofibromas (PNFs) are benign tumors composed mainly of tumorous Schwann cells and non-tumorous fibroblasts. This study examined the possible enhancing effect of vitamin D on the efficacy of drugs used for the treatment of PNF in vitro. Paired Schwann cells and fibroblasts were cultured from 10 PNFs and treated with imatinib and nilotinib in the absence and presence of calcipotriol, an analogue of the active metabolite of vitamin D. IC50 values for cell proliferation were calculated. Calcipotriol reduced the IC50 of the two drugs in both tumorous Schwann cells and non-tumorous fibroblasts by 40 to 45%. Calcipotriol enhanced the efficacy of imatinib and nilotinib on PNF-derived cells in vitro, though rather non-specifically. Nevertheless, sustaining vitamin D at 100-200 nM, the physiological range, may be beneficial for reducing the dose of drugs without scarifying efficacy.

No enhancing effect of vitamin A administration on iron absorption or body total iron content in preschool children from Chengdu, China.

To explore the effect of vitamin A supplements on iron metabolic homeostasis for preschoolers. This was a randomized, placebo-controlled and blinded intervention trial with 3- to 6-y old preschoolers. A total of 445 subjects were randomly divided into four groups: a vitamin A supplementation group (group 1, a single oral dose of vitamin A as retinol 200,000 IU), an iron supplement group (group 2, daily oral supplement with the elemental iron 1-2 mg/kg/d for 5 d a week, lasting for 6 mo) a combined vitamin A and iron (group 3) and administration of no vitamin A or iron as a placebo-control (group 4). A total of 387 (95, 98, 90 and 104 from groups 1, 2, 3 and 4) children completed the intervention. After intervention, serum retinol levels of children in group 1 and group 3 was markedly higher than those of children in groups 2 and 4 (p<0.05). The serum ferritin level of children in group 1 significantly decreased after intervention (p<0.05), but increased in group 2 (p<0.05). The sTfR-SF index (TFR-F) and total body iron content (BTIC) showed the same change after intervention. In group 2 and group 3, the levels of TRF-F index and BTIC had statistically increased to the same degree after intervention (p<0.05). The impact of vitamin A intervention on iron metabolic homeostasis was mainly manifested in storage and mobilization; there was no direct effect on total body iron content or iron absorption in the intestine.

Dual role of vitamin C in an oxygen-sensitive system: Discrepancy between DNA damage and dell death

Although vitamin C is considered to act both as pro-oxidant and antioxidant, the mechanisms underlying these actions are still unclear. Using the oxygen-sensitive system of a strict anaerobe, Prevotella melaninogenica, we investigated both the pro-oxidant and antioxidant mechanisms of vitamin C. In the presence of vitamin C, the 8-hydroxydeoxyguanosine (8OHdG) formation induced by oxygen exposure was enhanced, probably due to the action of vitamin C on hydrogen peroxide generated during oxygen exposure: while catalase almost completely suppressed the enhancing effect of vitamin C, 8OHdG formation induced by hydrogen peroxide was enhanced by vitamin C. By contrast, the presence of vitamin C inhibited bacterial cell death, membrane damage, and lipid peroxidation induced by oxygen exposure. Sodium azide showed similar effects to vitamin C, thus the antioxidant action of vitamin C may be due to its quenching of the singlet oxygen generated in this system. Both the pro-oxidant and antioxidant effects of vitamin C were observed only in acidic conditions.

No enhancing effect of vitamin A on iron absorption in humans

Vitamin A and beta-carotene were recently reported to enhance iron absorption by counteracting the inhibitory effect of phytic acid in cereal-based meals and of polyphenol-containing beverages on nonheme-iron absorption in humans. Our objective was to further evaluate the influence of vitamin A on iron absorption. Iron absorption from corn bread with or without added vitamin A (retinyl palmitate) was determined in 5 studies in young adult human subjects by using either a stable-isotope method (2 studies) or a radioisotope technique (3 studies). Iron absorption was measured by erythrocyte incorporation of the isotopic labels and by whole-body retention of (59)Fe. Corn bread was served with water (studies 1 and 3) or coffee (studies 2, 4, and 5). The studies differed in the amounts and chemical forms of added tracer and fortification iron. The possibility of methodologic artifacts in earlier investigations was evaluated. No effect of vitamin A on iron absorption from the test meals was identified in the individual studies by using paired Student's t test. A slightly negative effect of vitamin A on iron absorption was found with the use of analysis of variance. The previously reported findings of a positive effect of vitamin A on nonheme-iron absorption in humans was not confirmed. Incomplete isotopic equilibration of the tracer with native iron in the meal or with fortification iron cannot explain the previous findings. However, the present study does not exclude the possibility that suboptimal vitamin A status influences the effect of dietary vitamin A on iron absorption.

Effectiveness of vitamin A acetate for enhancing the production of lung cancer specific monoclonal antibodies.

The antibody productivity of the human-human hybridoma cell line AE6, which produces the lung cancer specific human monoclonal antibody AE6F4, was enhanced fourfold upon stimulation with 1 mug/ml of vitamin A acetate for one day. The enhancement lasted for about two weeks, and could be repeated by another stimulation with vitamin A acetate. The enhancing effect of vitamin A acetate was influenced by the cell density. Enhancement was clearly observed when the cell density was under 10(6) cells/ml. However, when the cell density was over 10(7) cells/ml, enhancement was observed weakly or not at all. Although the enhancing effect of vitamin A acetate is not unique to AE6 cells, not all human-human hybridoma cell lines show increased productivity upon VA acetate stimulation. This study suggests that the response to vitamin A acetate may be related to the properties of a particular fusion partner which the hybridoma cell inherits. The efficacy of vitamin A acetate for production of human monoclonal antibodies using human-human hybridomas is discussed.

Effect of dietary vitamin E on the development of altered hepatic foci and hepatic tumors induced by the peroxisome proliferator ciprofibrate

The purpose of this study was to determine the effect of the dietary antioxidant vitamin E on hepatocarcinogenesis by peroxisome proliferators which, it is hypothesized, induce tumors by increased production of hydrogen peroxide or other oxygen radicals. Rats were fed diets containing the peroxisome proliferator ciprofibrate and one of three concentrations (10, 50, or 500 ppm) of alpha-tocopheryl acetate for 6 months or 21 months. The incidence of hepatic tumors and the number and volume of gamma-glutamyl-transpeptidase-positive, ATPase-negative, glucose-6-phosphatase-negative, and glucose-6-phosphatase-positive foci were quantified. No tumors or altered hepatic foci were seen at 6 months, but at 21 months the incidence of hepatic tumors and the number and volume of altered hepatic foci were increased in rats fed higher levels of vitamin E. Indices of oxidative damage--concentrations of malonaldehyde, conjugated dienes, and lipid-soluble fluorescence products--were not affected or were lower in rats fed higher amounts of vitamin E; the enhancing effect of vitamin E on the development of altered hepatic foci and hepatic tumors, therefore, was not related to the induction of cellular oxidative damage. Hepatic peroxisomal fatty acid beta-oxidation and vitamin C concentrations were not affected by vitamin E, whereas the glutathione concentration was decreased in rats fed higher amounts of vitamin E. This study shows that increasing the vitamin E content of the diet enhances ciprofibrate-induced hepatocarcinogenesis, but the mechanism of this effect is unclear.