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At least 1,369 records · Page 76Linked to original sources
PubMed1997

Supercritical fluid extraction and reversed-phase liquid chromatography methods for vitamin A and beta-carotene heterogeneous distribution of vitamin A in the liver.

We developed supercritical fluid procedures for extracting vitamin A and beta-carotene from vitamin supplements and calf liver tissue. The SF extracts could be injected onto an HPLC column without further pretreatment. Samples were analysed by RP-HPLC using diode array detection or by spectrophotometry. Recoveries were very good. SF extracts from a vitamin preparation of uniform composition had an R.S.D. of 4%. Extracts from calf liver supplements were predictably more heterogeneous. The SF extraction method is less labor intensive then traditional liquid-liquid procedures for extracting vitamin A and carotenoids from tissues.

Animals↗
PubMed1999

Prostaglandin E2 regulates vitamin D receptor expression, vitamin D-24-hydroxylase activity and cell proliferation in an adherent human myeloid leukemia cell line (Ad-HL60).

The effects of prostaglandin E2, forskolin, and phorbol 12-myristate 13-acetate on cell proliferation, cell surface antigen expression, vitamin D-24-hydroxylase activity and vitamin D receptor (VDR) expression have been studied in an adherent variant (Ad-HL60) of the human HL60 promyelomonocytic leukemia cell line. Ad-HL60 cells have a more differentiated phenotype than the nonadherent HL60 cells from which they were derived and, unlike the parent cell line, constitutively express vitamin D-24-hydroxylase activity. Treatment of Ad-HL60 cells with 1 microM PGE2 resulted in a decrease in the rate of cell proliferation (cell numbers were approximately 23% of control values after 72 h treatment), a change in expression of leukocyte surface antigens (decreased CD13 and CD14, increased CD11b and CD49d expression), an increase in the synthesis of 24,25-dihydroxyvitamin D3 from substrate 25-hydroxyvitamin D3 (control 5.76 +/- 0.17, 72 h PGE2-treated cells 12.10 +/- 1.90 pmol/h/10(6) cells), and an increase in receptors for the active metabolite of vitamin D, 1 alpha,25-dihydroxyvitamin D3, from 3910 to 11285 receptors per cell in control and 7-day treated cells, respectively. Prostaglandin E2 may be acting via a mechanism involving cyclic AMP in these cells, as we have also demonstrated that 10 microM forskolin, an adenylate cyclase activator, has similar effects. Phorbol 12-myristate 13-acetate had little effect on any of the parameters measured in this cell line.

24,25-Dihydroxyvitamin D 3↗
PubMed1998

A primary prevention trial using nutritional doses of antioxidant vitamins and minerals in cardiovascular diseases and cancers in a general population: the SU.VI.MAX study--design, methods, and participant characteristics. SUpplementation en VItamines et Minéraux AntioXydants.

The SUpplementation en VItamines et Minéraux AntioXydants (SU.VI.MAX) Study is a randomized, double-blind, placebo-controlled, primary-prevention trial designed to test the efficacy of daily supplementation with antioxidant vitamins (vitamin C, 120 mg; vitamin E, 30 mg; and beta-carotene, 6 mg) and minerals (selenium, 100 microg; and zinc, 20 mg) at nutrition-level doses (one to three times the daily recommended dietary allowances) in reducing several major health problems in industrialized countries, especially the main causes of premature death, cancers and cardiovascular diseases. The present report describes the design, implementation, and baseline characteristics of participants in this 8-year cohort study, which started in 1994 in France; 12,735 eligible subjects (women aged 35-60, and men aged 45-60) were included in 1994 and will be followed for 8 years. Participants undergo a yearly visit consisting, every other year, of either biological sampling or clinical examination. They also regularly provide information on health events and dietary intake by filling out computerized questionnaires using the Minitel Telematic Network. Data on baseline characteristics of the participants suggest that the present sample is close to the national population in terms of geographic density, socioeconomic status, and the distribution of various major risk factors for the diseases under study. The choice of the study population should allow the results of this trial to apply to adult populations of both sexes in France and other industrialized countries.

Adult↗
PubMed1997

Vitamin D receptor content and transcriptional activity do not fully predict antiproliferative effects of vitamin D in human prostate cancer cell lines.

Prostate cancer cell lines exhibit variable growth suppression by the hormonal form of vitamin D3, 1,25-Dihydroxyvitamin D3 [1,25 (OH)2D] (1,25 D3). To understand the molecular basis for this differential sensitivity to 1,25 D3, we compared growth response to 1,25 d3, vitamin D receptor (VDR) content and VDR transcriptional activity in four well-characterized human prostate cancer cell lines: LNCaP, DU145, PC-3 and ALVA-31. In PC-3 and DU145 cells, relative lack of growth inhibition by 1,25 D3 (< 10% inhibition) correlates with very low levels of VDR (9-15 fmol/mg protein) compared to classical vitamin D3 target tissues (approximately 75-200 fmol/mg protein). Transfection of DU145 and PC-3 cells with a VDR cDNA expression vector is sufficient to establish growth sensitivity to 1,25 D3, suggesting that low VDR levels are responsible for the failure of these cell lines to respond to 1,24 D3. LNCaP cells are highly sensitive to growth inhibition by 1.25 D3 (approximately 55% inhibition) and contain approximately 2-3-fold more VDR (25 fmol/mg) than the relatively 1,25 D3-insensitive PC-3 and DU145 cell lines. However, ALVA-31 cells display less than 20% growth inhibition to 1.25 D3 although they contain the highest levels of VDR (45 fmol/mg) of the four cell lines. Thus, sensitivity to growth inhibition by 1,25 D3 does not correlate with VDR content in ALVA-31 and LNCaP cells. This lack of correlation between VDR density and growth responses to 1,25 D3 led us to investigate VDR-mediated gene transcription in these cell lines. We employed two different naturally occurring vitamin D response elements (VDREs) linked to a reporter gene. Reporter gene activation by 1,25 D3 correlated well with VDR content in all four cell lines. Therefore, compared to LNCaP cells, decreased sensitivity of ALVA-31 to growth inhibition by 1,25 D3 is not due to a decrease in the general transcriptional activity of VDR. We conclude that growth inhibition by 1,25 D3 in prostate cancer cells requires VDR but that this response is modulated by non-receptor factors that are cell line-specific.

Calcitriol↗
PubMed2000

Chromate-induced human erythrocytes haemoglobin oxidation and peroxidation: influence of vitamin E, vitamin C, salicylate, deferoxamine, and N-ethylmaleimide.

In order to attenuate or to prevent chromate-induced human erythrocytes injury, the influence of vitamin E, vitamin C, salicylate, deferoxamine, and N-ethylmaleimide on chromate-induced human erythrocytes haemoglobin oxidation and peroxidation were investigated. It was observed that pretreatment of human erythrocytes with vitamin E (20 microM), vitamin C (1 mM), salicylate (3 mM), and deferoxamine (4 mM) significantly increased (P=0.0001) chromate-induced human erythrocytes haemoglobin oxidation in a time dependent manner, while it was significantly decreased (P=0.0001) by pretreatment with N-ethylmaleimide (1 mM). In contrast, pretreatment of human erythrocytes with deferoxamine (4 mM) immediately inhibited (P=0.0001) chromate-induced human erythrocytes peroxidation, while it was significantly increased (P=0.0001) by pretreatment with N-ethylmaleimide (1 mM) during the first 4 h of cells exposition to chromate. For time periods superior to 6 h pretreatment with N-ethylmaleimide (1 mM) significantly decreased (P=0.0001) chromate-induced human erythrocytes peroxidation. It was concluded that care must be taken as these drugs are used to prevent against toxicity induced by chromium(VI) compounds.

Ascorbic Acid↗
PubMed1999

Low concentrations of 17beta-estradiol reduce oxidative modification of low-density lipoproteins in the presence of vitamin C and vitamin E.

Micromolar concentrations of estradiol are required to inhibit the oxidation of low-density lipoproteins (LDL) in vitro. Recent evidence suggests that estradiol must be modified before it can become an effective antioxidant at physiological levels. Our aim was to determine other possible conditions under which low concentrations of 17beta-estradiol can reduce LDL oxidation. LDL susceptibility to oxidation was monitored by measurements of conjugated diene formation. High levels of 17beta-estradiol reduced oxidative modification of LDL. Vitamin C and vitamin E also increased LDL resistance to Cu2+-mediated oxidation. More importantly, 10 nM 17beta-estradiol, which on its own had no effect, exhibited significant antioxidant actions in the presence of either vitamins C or E. In conclusion, supraphysiological concentrations of 17beta-estradiol are required to exert antioxidant effects directly in vitro. However, in the presence of vitamins C and E, concentrations of 17beta-estradiol close to physiological levels can also protect LDL from oxidation.

Adult↗
PubMed1998

Direct repeat 3-type element lacking the ability to bind to the vitamin D receptor enhances the function of a vitamin D-responsive element.

In a previous study, we identified the element which allows the maximum response to 1,25(OH)2D3 in concert with two vitamin D-responsive elements (VDREs) in the rat 25-hydroxyvitamin D3 24-hydroxylase gene promoter, and designated it an accessory element [Ohyama, Y., Ozono, K., Uchida, M., Yoshimura, M., Shinki, T., Suda, T. and Yamamoto, O. Functional assessment of two vitamin D-responsive elements in the rat 25-hydroxyvitamin D3 24-hydroxylase gene. J. Biol. Chem., 1996, 271, 30381-30385]. The accessory element located adjacent to the proximal VDRE is not capable of binding to the vitamin D receptor (VDR), while its nucleotide sequence resembles the consensus sequence of VDREs, direct repeat 3 (DR3). To clarify the difference between the accessory element and VDREs, the function of the accessory element was compared with that of VDREs. The mutated accessory elements with a single nucleotide substitution showed the capability of binding to the VDR in vitro. However, these mutants still did not act as a VDRE when driven by the heterologous SV40 promoter. The accessory element did not enhance the function of a cAMP-responsive element. The corresponding site of the accessory element in the human 24-hydroxylase is a DR4-type element, and this element did not function as an accessory element. These results indicate that a critical nucleotide sequence is necessary for the binding to the VDR and for mediating the vitamin D effect, and suggest the different regulation between the rat and human 24-hydroxylase gene.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1976

Vitamin A transport in human vitamin A toxicity.

The plasma retinol transport system was studied in three patients with chronic hypervitaminosis A. The toxic state in each was associated with increased plasma concentrations of total vitamin A, and particularly of retinyl esters. The concentrations of plasma retinol-binding protein and prealbumin were, in contrast, non to retinol-binding protein. These limited clinical data support conclusions from detailed studies with hypervitaminotic rats, which suggest that vitamin A toxicity occurs when excessive amounts of vitamin A are presented to cell membranes in association with plasma lipoproteins, rather than specifically bound to retinol-binding protein. Retinol-binding protein may not only regulate the supply of retinol to tissues but also protect tissues from the surface-active properties of the vitamin.

Adult↗
PubMed2004

Dietary sources of vitamin C, vitamin E and specific carotenoids in Spain.

A cross-sectional study was conducted within the Spanish cohort of the European Prospective Investigation in Cancer and Nutrition to assess the principal food sources of vitamin C, vitamin E, alpha-carotene, beta-carotene, lycopene, lutein, beta-cryptoxanthin and zeaxanthin in an adult Spanish population. The study included 41446 healthy volunteers (25812 women and 15634 men), aged 29-69 years, from three Spanish regions in the north (Asturias, Navarra and Guipúzcoa) and two in the south (Murcia and Granada). Usual food intake was estimated by personal interview through a computerized version of a dietary history questionnaire. Foods that provided at least two-thirds of the studied nutrients were: fruits (mainly oranges) (51 %) and fruiting vegetables (mainly tomato and sweet pepper) (20 %) for vitamin C; vegetable oils (sunflower and olive) (40 %), non-citrus fruits (10 %), and nuts and seeds (8 %) for vitamin E; root vegetables (carrots) (82 %) for alpha-carotene; green leafy (28 %), root (24 %) and fruiting vegetables (22 %) for beta-carotene; fruiting vegetables (fresh tomato) (72 %) for lycopene; green leafy vegetables (64 %) for lutein; citrus fruits (68 %) for beta-cryptoxanthin; citrus fruits (43 %) and green leafy vegetables (20 %) for zeaxanthin. In conclusion, the main food sources of nutrients with redox properties have been identified in a Mediterranean country. This could provide an insight into the interpretation of epidemiological studies investigating the role of diet in health and disease.

Adult↗
PubMed1987

Intermittent high-dose vitamin D prophylaxis during infancy: effect on vitamin D metabolites, calcium, and phosphorus.

In infants receiving intermittent high dose vitamin D prophylaxis (600,000 IU ergocalciferol per dose orally) every 3-5 mo, the serum concentrations of vitamin D metabolites, calcium (Ca), and phosphorus (P) were determined before and 2 wk after each dose. The 25-hydroxyvitamin D (OHD) concentrations increased to well above normal but the values returned to the normal range before each subsequent dose. The 24,25- and 25,26-dihydroxyvitamin D ([OH]2D) levels followed a pattern similar to that of 25-OHD, and both were closely related to the latter (r = 0.85, p less than 0.005, and r = 0.84, p less than 0.005, respectively). The 1,25-(OH)2D concentrations did not vary in a consistent pattern and remained largely within the normal range. All infants had normal Ca levels before the first dose but 14 infants (34%) later had one or both Ca values above the upper normal limit of 2.80 mmol/L (2.81-3.32 mmol/L), indicating that the vitamin D doses were excessive despite the lack of accumulative increases in serum vitamin D concentrations.

24,25-Dihydroxyvitamin D 3↗
PubMed1988

Vitamin A-fortified monosodium glutamate and vitamin A status: a controlled field trial.

A controlled trial of fortification of crystalline monosodium glutamate (MSG) with 810 micrograms RE vitamin A/g was undertaken in an area of endemic vitamin A deficiency in Indonesia. Powdered MSG was used to mask the yellow color of the vitamin A. Fortified MSG was marketed through ordinary channels in five villages in the program area and five nearby villages served as the control area. The product retained 84% of its potency after 4 mo and 57% after 11 mo in the marketplace. Base-line serum and breast-milk vitamin A levels were slightly higher in the control areas. Follow-up serum levels increased dramatically in program villages, 0.67 +/- 0.33 at prefortification base line to 0.92 +/- 0.33 mumol/L (p less than 0.001) at 11 mo after introduction of the fortified product. Breast-milk levels also rose, from 0.60 +/- 0.29 at base line to 0.67 +/- 0.30 mumol/L at 11 mo (p less than 0.05). Serum and breast-milk levels in control villages did not change.

Female↗
PubMed1993

Glycosylated hemoglobin concentrations and vitamin E, vitamin C, and beta-carotene intake in diabetic and nondiabetic older adults.

Studies indicate that large doses of all-rac-alpha-tocopherol in people with diabetes or ascorbic acid in nondiabetic subjects reduces protein glycosylation. The mechanisms by which these nutrients influence glycosylation are poorly understood but may be related to their ability to function as antioxidants. We examined the relationship between glycosylated hemoglobin (GHb) and intake of vitamins E and C and beta-carotene in a population-based sample of middle-aged and older adults participating in the Beaver Dam Eye Study. In people with diabetes, no significant associations were observed between GHb and intake of vitamins E and C and beta-carotene. In people without diabetes, energy-adjusted vitamin C intake was negatively associated with GHb after age and sex were controlled for (dietary, P = 0.02; total, P = 0.04). No significant relationships between GHb and intake of vitamin E and beta-carotene were observed.

Adult↗
PubMed1996

Bioavailability of calcium supplements and the effect of Vitamin D: comparisons between milk, calcium carbonate, and calcium carbonate plus vitamin D.

Our aim was to examine a regimen for calcium supplementation because various factors seem to be important for its bioavailability, and to examine the effect of adding vitamin D to the supplement. The participants were 20 healthy women aged 28-59 y (chi: 38 y). During the 3-d periods and 1 d before, the participants were consuming a calcium and energy-balanced diet as similar to their usual daily diet as possible. The study was designed as a randomized, placebo-controlled, partly blinded crossover study divided into four periods of 3 d each: 1) three tablets containing 1000 mg CaCO3/d, 2) three tablets containing 1000 mg CaCO3 plus 5 micrograms (200 IU) vitamin D/d, 3)1 L more milk than in the usual daily diet, and 4) three placebo tablets daily. Bioavailability of the different calcium-supplement regimens were evaluated by changes in 24-h urinary excretion of calcium, phosphate, and magnesium. A significant increase in urinary calcium excretion was found during all periods of supplementation compared with the placebo period (P<0.01). Excretion of calcium in the calcium carbonate period was not significantly higher that that in the milk period, but calcium carbonate plus vitamin D resulted in significantly higher calcium excretion compared with that in the milk period. We conclude that the examined calcium carbonate regimen is at least as good a calcium supplement as milk, and that addition of 600 IU vitamin D/d promptly resulted in an increase in urinary calcium excretion after an increase in calcium absorption, even in healthy women.

Adult↗
PubMed2003

Reliability and validity of self-report of vitamin and mineral supplement use in the vitamins and lifestyle study.

In the United States, dietary supplements contribute a large proportion of micronutrient intakes. Therefore, it is important to collect accurate information on supplement use for studies of micronutrients and disease risk. This report describes the test-retest reliability and validity of a detailed, self-administered mailed questionnaire on vitamin and mineral supplement use. Participants (n = 220) completed the questionnaire at baseline and 3 months later. During an in-person interview, participants provided spot urine and blood samples, and interviewers transcribed nutrient information from their supplement bottle labels. The questionnaire had very good test-retest reliability for mean supplement intake over the past 10 years, with intraclass correlations ranging from 0.69 for beta-carotene to 0.87 for vitamin E. Pearson's correlation coefficients comparing current supplemental intakes from the questionnaire and interviews/label transcriptions were high, ranging from 0.58 for beta-carotene to 0.82 for chromium; however, for some nutrients, median intakes from the questionnaire were slightly lower than from the interviews. Beta-carotene, vitamin C, and vitamin E (alpha-tocopherol) showed clear linear trends of increasing blood concentrations with higher self-reported supplemental intakes (Pearson's correlation coefficients adjusted for potential confounding factors and diet = 0.31, 0.29, and 0.69, respectively; all p < 0.0001). Creatinine-adjusted spot urinary calcium values were not associated with supplemental calcium intakes (Pearson's r = -0.07). This self-administered questionnaire demonstrated high reproducibility and validity for collecting detailed information on supplement use.

Aged↗
PubMed1984

Effect of sow vitamin D status at parturition on the vitamin D status of neonatal piglets.

The plasma concentrations of calcium, phosphorus, vitamin D, and vitamin D metabolites were determined in cholecalciferol-treated sows and untreated sows at parturition and their piglets (at birth and at 10 days of age) to determine the relationship between sow vitamin D status and neonatal piglet vitamin D status. At birth, there was a high degree of correlation between sow and piglet plasma concentrations of 25-hydroxycholecalciferol (r = 0.944), 24,25-dihydroxycholecalciferol (r = 0.895), and 25,26-dihydroxycholecalciferol (r = 0.737). Neonatal piglet plasma 1,25-dihydroxyvitamin D was low (42.0 +/- 10.2 pg/ml) and was not correlated with maternal plasma 1,25-dihydroxyvitamin D (r = 0.022). Neonatal plasma calcium and phosphorus were significantly correlated (P less than 0.05) with maternal plasma 1,25-dihydroxyvitamin D (r = 0.515 and 0.581, respectively). Parenteral cholecalciferol treatment of sows before parturition proved an effective means of supplementing young piglets with cholecalciferol (via the sow's milk) and its more polar metabolites via placental transport. However, it had no significant effect on either the plasma mineral or 1,25-dihydroxyvitamin D status of the sow or young piglet.

Aging↗
PubMed2002

N-Acetylcysteine, vitamin C and vitamin E diminish homocysteine thiolactone-induced apoptosis in human promyeloid HL-60 cells.

We showed previously that homocysteine thiolactone (HcyT) is a potent inducer of apoptosis in HL-60 cells. In the present study, the role of some radical scavengers (N-acetylcysteine, vitamin C, vitamin E and folate) on the reduction of HcyT-induced apoptosis was investigated. Preincubation of HcyT-treated HL-60 cells with vitamin C (Vit C; 100 micro mol/L) or vitamin E (Vit E; 100 micro mol/L) for 2 h significantly reduced the proportion of apoptotic cells with hypodiploid DNA contents or with membrane phosphatidylserine exposure, and attenuated the apoptotic DNA fragmentation. Preincubation of cells with N-acetylcysteine (NAC; 5 mmol/L) for 2 h significantly reduced HcyT-promoted apoptosis measured by membrane phosphatidylserine exposure only. The reduction of HcyT-induced apoptosis by NAC, Vit C or Vit E occurred simultaneously with a significant decrease in intracellular H(2)O(2) levels and reduced caspase-3 enzymatic activity. In contrast, folate had no H(2)O(2) scavenging capacity and did not suppress caspase-3 activity 6 h after HcyT treatment, although folate exhibited antioxidant behavior toward superoxide anions, hydroxyl radicals and peroxynitrite. Preincubation of cells with folate (10 micro mol/L) for 3 d did not affect the extent of HcyT-promoted apoptotic damage. Taken together, our findings suggest that antioxidant pretreatment with NAC, Vit C or Vit E exerts more beneficial effects than folate on reducing apoptotic cell damage induced by homocysteine thiolactone.

Acetylcysteine↗
PubMed1988

Association of food frequency questionnaire estimates of vitamin A intake with serum vitamin A levels.

To assess the validity of nutrient intake estimates from a food frequency questionnaire, the authors compared estimates of intake of preformed retinol (dietary plus supplements), beta-carotene, other active carotenoids, and total vitamin A computed from questionnaire responses with serum retinoid and carotenoid concentrations. Data were obtained from 302 male and female current or former smokers, participants in a lung cancer chemoprevention trial at the Fred Hutchinson Cancer Research Center in Seattle, Washington, during 1985-1986. Both serum beta-carotene and serum alpha-carotene were associated, although weakly, with food frequency estimates of total vitamin A intake, dietary vitamin A, beta-carotene, other carotenoids, and total carotenoids (0.18 less than or equal to r less than or equal to 0.26). Serum retinol was associated with supplementary vitamin A intake (r = 0.16). Nondietary factors were also associated with serum nutrient concentrations--in particular, cigarette smoking, alcohol intake, and body mass index. Cigarette smoking emerged as an important modifying factor of the relation between serum beta-carotene and dietary beta-carotene (r = 0.14 for current smokers, r = 0.30 for former smokers).

Aged↗
PubMed1976

Inhibitory effect of eggs on vitamin B12 absorption: description of a simple ovalbumin 57Co-vitamin B12 absorption test.

Ovalbumin and egg yolks, mixed separately in vitro with radiocyanocobalamin (57 Co-vitamin B12), were served to normal volunteers in a cooked form. Ovalbumin, and to a lesser degree, egg yolks were observed to inhibit vitamin B12 absorption. This observation explains the rather poor assimilation of vitamin B12 from eggs labelled in vivo with 57 Co-vitamin B12.

Absorption↗