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Summary
Safflower and coconut oil were compared as protective carriers of dietary vitamin A supplemented to abomasally cannulated sheep. Vitamin A, 240,000 I.U., was predissolved in 11.7 g of safflower or coconut oil and bolused directly into the rumen of mature wethers along with 4 g of chromic oxide. The vitamin A was pre-dissolved in 0, 11.7, 23.4 or 35.0 g of coconut oil in experiment 2. Determination of carrier oil protectiveness of solubilized dietary vitamin A was based on recoveries of vitamin A supplement and chromic oxide in abomasal digesta 24 h post dosage. Vitamin A recoveries were significantly higher (P < 0.05) when dissolved in coconut oil (55.6%) compared to safflower oil (35.5%). Recoveries of vitamin A in abomasal digesta increased linearly (P < 0.01) with the amount of carrier coconut oil in experiment 2. Results of these experiments support the potential use of coconut oil as a protective carrier of ruminal labile vitamin A.
Keywords
Orally dosed vitamin A, Ruminal degradation, Carrier oil
International Journal for Vitamin and Nutrition Research,
Band 67, 1997, Heft 6, © Verlag Hans Huber, Bern
Summary
The in vitro and in vivo interaction between b-carotene (BC) and lipoxygenase (LOX) was studied in rat skin. Significant in vitro inhibitory effects of BC on epidermal LOX activity were observed with both linoleic acid or arachidonic acid as substrate. Lineweaver-Burk plots for the inhibition of epidermal purified LOX indicated mixed competitive /non-competitive inhibition. In vivo effects of BC were examined in an ultraviolet A (UVA) irradiation model. Following UVA irradiation (200 Kjoule/m2) significant increases in LOX activity and malondialdehyde (MDA) values were found, whereas catalase activity was significantly decreased. Topical pretreatment of skin with BC prevented increases in LOX activity and MDA values 4 hr post-irradiation. Catalase activity was not affected by BC treatment. BC was more effective at preventing UVA induced lipid peroxidation at low then at high concentrations. Our present results indicate the protective potential of BC on in vivo UVA induced skin damage by reduction of non-enzymatic and enzymatic lipid peroxidation.
Keywords
b-carotene, Lipoxygenase, Oxidation, Rat, Skin, Ultraviolet
International Journal for Vitamin and Nutrition Research,
Band 67, 1997, Heft 6, © Verlag Hans Huber, Bern
Summary
The inhibitory effects of b-carotene or vitamin A on preneoplastic lesions induced in rats were compared, when specifically administered during early promotion of hepatocarcinogenesis. Initiation was performed by diethyl- nitrosamine. During the selection/promotion period 2-acetylaminofluorene was administered, and a partial hepatectomy was performed. Afterwards, the rats were divided into 3 groups. To two groups, b-carotene or vitamin A were given for five weeks. Another group served as control and received corn oil. At the end of the study, b-carotene reduced the incidence and total number of hepatocyte nodules. Vitamin A rats exhibited a lower number of nodules, but the incidence was 100%. Moreover, b-carotene reduced the total number of gGT-positive preneoplastic lesions, as well as the morphometric parameters of persistent gGT-positive lesions. In contrast, morphometric parameters of persistent lesions remained almost unaffected in vitamin A animals. Furthermore, b-carotene significantly increased the number of remodeling gGT-positive preneoplastic lesions. Vitamin A administration, however, resulted only in a small increase in the number of remodeling lesions. These results suggest that the inhibitory effects of b-carotene during early promotion of hepatocarcinogenesis can be attributed not only to an inhibitory effect on persistent lesions, but also to a striking stimulatory activity on remodeling gGT-positive lesions.
Keywords
Hepatocarcinogenesis, Promotion, Preneoplastic Lesions, b-Carotene, Vitamin A
International Journal for Vitamin and Nutrition Research,
Band 67, 1997, Heft 6, © Verlag Hans Huber, Bern
Summary
Following a single oral dose of all-trans retinoic acid (RA) (0.167 mmole) in corn oil to 6 healthy human subjects, the mean serum retinol (ROL) level fell by approximately 20% within 1 h and remained depressed for 24 h. After dosing, RA appeared in the blood within 30 min, peaked at 0.3 - 0.5 mmol/l, and then declined to very low concentrations after 7 h. All-trans retinoyl b-glucuronide (RAG) appeared simultaneously with RA in the plasma, albeit more sporadically, whereas only traces of 4-oxoretinoic acid (4-oxoRA) were detected. Some possible physiologic consequences of therapeutic uses of all-trans RA are discussed.
Keywords
Retinol, Retinoic acid, Retinoyl b-glucuronide, 4-Oxoretinoic acid, Human serum
International Journal for Vitamin and Nutrition Research,
Band 67, 1997, Heft 6, © Verlag Hans Huber, Bern
Summary
The present work shows that dietary tretinoin (all-trans-retinoic acid) supplementation may be a useful manuvre for the prevention of age-related renal changes. 18-month-old male Fischer 344 rats fed during three months with standard chow plus tretinoin (1 mg/kg/day) did not exhibit any adverse effect in terms of bodyweight, urinary volume, renal handling of sodium and both hematological and blood chemistry parameters. Although the diet did not reduce age-related proteinuria nor renal lipid peroxidation, glomerular filtration rate and renal cortex protein content were, respectively, 30% higher and 30% lower than in age-matched control rats. These results suggest that dietary tretinoin supplementation may be a useful manuvre to slow the progression of age-related renal changes. Since glomerular H2O2 production increases during renal aging in rats, we studied the effect of tretinoin on the biology of cultured glomerular rat mesangial cells exposed to H2O2. Preincubation with tretinoin abolished cell proliferation or cell death induced, respectively, by low and high concentrations of H2O2. These results suggest that the modulation of the cellular actions of H2O2 may be relevant in the mechanisms through which tretinoin prevents age-related renal changes.
Keywords
Tretinoin, all-trans-Retinoic acid, Kidney, Aging, Hydrogen peroxide, Mesangial cells
International Journal for Vitamin and Nutrition Research,
Band 67, 1997, Heft 6, © Verlag Hans Huber, Bern
Summary
Paediatric reference intervals for blood concentrations of certain nutrients are often based on either adult data or are derived from small samples of young children. Biochemical data were obtained from 467 randomly selected, healthy preschool children aged 9-62 months in Sydney, Australia. Data were obtained for plasma vitamins A, E and b-carotene and for serum zinc, retinol-binding protein and prealbumin. Reference intervals based on the 2.5 and 97.5 centiles for age groups 9-23, 24-35, 36-47, 48-62 months and for the total group (9-62 months) were calculated. The 2.5-97.5 centiles for the whole group were: vitamin A, 0.7-1.8 mmol/l (20.05-51.56 mg/dl); vitamin E, 8-30 mmol/l (0.34-1.29 mg/dl); b-carotene, 0.1-1.1 mmol/l (5.4-59.0 mg/dl); zinc, 9-19 mmol/l (58.8-124.2 mg/dl); retinol-binding protein, 14-36 mg/l; prealbumin, 104-264 mg/l. The reference intervals reported are consistent with the findings of a number of smaller studies and are likely to be an accurate reflection of the true intervals for healthy preschool children in western developed countries.
Keywords
Vitamin A, Vitamin E, b-Carotene, Zinc, Preschool children, Reference intervals, Age-specific
International Journal for Vitamin and Nutrition Research,
Band 67, 1997, Heft 6, © Verlag Hans Huber, Bern
Summary
Phosphoenolpyruvate carboxykinase (GTP) (PEPCK) is one of the key enzymes of gluconeogenesis. Mechanisms responsible for rapid regulation of enzyme activity include activation by bivalent cations such as Mn2+ and Fe2+ and/or alterations of the oxidation state of the enzyme's SH groups. A cytosolic cell free system prepared from rat liver was used to study the effects of the thiol reagents GSH and di-thiothreitol (DTT) and particularly of vitamin C on PEPCK activity. (1) Basal activity and Mn2+-stimulated activity were not affected by variations in the concentrations of GSH and DTT, indicating that some components of the cell free system provided sufficient protection against PEPCK-inactivation due to disulfide bond formation. The latter phenomenon is known to occur with purified PEPCK in the absence of added thiols. Only in the presence of 2 µM Fe2+, GSH/DTT addition increased PEPCK activity. (2) Addition of vitamin C in the range of 0.6-1.2 mM resulted in a marked stimulation of the PEPCK reaction, ranging from 1.5-fold (with 2 µM Mn2+) to 4-7-fold (for basal activity and with 2 µM Fe2+). (3) When 5,5'-dithio-bis (2-nitrobenzoic acid) (DTNB) was used to induce disulfide bond formation and subsequent inactivation of PEPCK, reactivation experiments with GSH/DTT but not with vitamin C restored full enzyme activity. It is concluded that vitamin C activates PEPCK or protects it from inactivation caused by oxidants by a mechanism that does not involve the reduction of the enzyme's thiols.
Keywords
Phosphoenolpyruvate Carboxykinase, Vitamin C, Ascorbic acid, Thiol, Disulfide bond, Manganese, Iron, Rat Liver
International Journal for Vitamin and Nutrition Research,
Band 67, 1997, Heft 6, © Verlag Hans Huber, Bern
Summary
In order to compare the nutritional effect of vitamin B6 derivatives, long-term feeding experiments with rats were carried out using pyridoxine-a-D-glucoside (PN-a-Glc), pyridoxine-b-D-glucoside (PN-b-Glc) or e- (N-phosphopyridoxyl)lysine (PNP-Lys) with test diets consisting of basically the AIN-76 composition, except for the addition of 0.1 mg pyridoxine equivalent (PN eq.)/100 g diet. During 21 days of pair-feeding against the vitamin B6-deficient diet group, body weight gain, urinary excretion of xanthurenic acid and pyridoxic acid were measured. After the feeding experiment, rats were killed and examined in terms of liver kynureninase activity (EC 3.7.1.3) with and without adding exogenous pyridoxal 5'-phosphate (PLP), erythrocyte aspartate aminotransferase activity (EC 2.6.1.1), as well as PLP concentration in blood. Rats fed with PN-a-Glc grew well, relative to the PN group. On the contrary, PN-b-Glc poorly served as vitamin B6 source, because average bioavailability was only about 22% in comparison to that of PN (100%). From this long-term feeding experiments, we have shown that PN-a-Glc (average bioavailability about 84%) is a good source of vitamin B6 similar to PN.
Keywords
Rat, Bioavailability, Pyridoxine-a-glucoside, Pyridoxine-b-glucoside, e-(N-phosphopyridoxyl)-lysine, Feeding experiment, Vitamin B6-deficiency
International Journal for Vitamin and Nutrition Research,
Band 67, 1997, Heft 6, © Verlag Hans Huber, Bern
Summary
A randomized double-blind trial was performed in order to assess
the efficacity of differing combinations of antioxidant nutrients on
biochemical parameters of vitamin and trace element status,
immunological parameters and free radical metabolism in elderly long
term hospitalized subjects. A total of 756 institutionalized elderly
subjects were recruited in 26 nursing homes in different areas of
France. Four groups were constituted, receiving daily, for 1 year,
either vitamins (beta-carotene, 6 mg; vitamin C, 120 mg; and vitamin
E, 15 mg), trace elements (zinc, 20 mg and selenium, 100 mg), trace
elements associated with vitamins, or a placebo. Biochemical
indicators of trace elements and vitamin status and free radical
parameters were measured before and after 6 months and 1 year of
supplementation. Some immunological markers were investigated
initially and after 6 months of supplementation on a subsample of 134
subjects.
Mean plasma levels of alpha-tocopherol, gamma-tocopherol, vitamin C,
alpha-carotene, beta-carotene and copper increased significantly
after 6 months of supplementation in groups receiving vitamins alone
or associated with trace elements. Serum selenium concentrations were
significantly increased at 6 months of supplementation, and serum
zinc only after one year in the trace element groups. Serum lycopene
levels were significantly decreased by trace element supplementation.
A significant increase in Se-glutathione peroxidase (GPx) levels was
observed in groups receiving trace elements alone or associated with
vitamins. No effect was noted on superoxide dismutase (SOD) activity
or TBARs production.
No effect of supplementation was found for in vitro lymphocyte
proliferative responses or most lymphocyte subsets, except for a
significantly lower percentage of CD2 subsets observed in groups
receiving mineral supplementation either alone or associated with
vitamins. A significant difference in CD19 subsets was found in
groups receiving trace elements. Mean IL-1 production was
significantly higher after 6 months of supplementation in the vitamin
groups.
Keywords
beta-Carotene, Carotenoids, Vitamin C, Vitamin E, Selenium, Zinc, Free radicals, Antioxidants, Immune response, Elderly people
International Journal for Vitamin and Nutrition Research,
Band 67, 1997, Heft 6, © Verlag Hans Huber, Bern
Summary
Influence of depletion of biotin on spontaneously occurring spike-wave seizures in the tottering mutant mouse was tested by electrocorticographic recordings over three hours in five mice fed a biotin deficient diet. Frequency of seizures as well as percent of time with epileptic discharges were clearly lowered in the biotin deficient animals compared with eight mice of the same age under normal food (p < 0.01 in Wilcoxon's U-test).
Keywords
Biotin deficiency, Tottering mutant mouse, Epilepsy, Spike-wave seizures
International Journal for Vitamin and Nutrition Research,
Band 67, 1997, Heft 6, © Verlag Hans Huber, Bern