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Summary
Lipoxygenase catalyzes the dioxygenation of polyenoic fatty acids
such as linoleate and arachidonate. The aim of the present study was
to examine the effect of retinol, all-trans-retinoic acid and
13-cis-retinoic acid on the activity of lipoxygenase-1 and
lipoxygenase-2 towards linoleic acid.
Lipoxygenase activity toward linoleic acid was followed by
determining changes in absorption at 234 nm. All retinoids inhibited
lipoxygenase-1 and lipoxygenase-2 activity. Lipoxygenase-2 activity
towards linoleic acid was rapid at pH 6.5; all-trans-retinol (10 mM)
caused a 50% inhibition in reaction rate. All-trans-retinol was
oxidized in parallel with diene production by lipoxygenase-2.
Lipoxygenase-2 activity on linoleic acid was competitively inhibited
by all-trans-retinol and all-trans-retinoic acid; 13-cis-retinoic
acid exhibited mixed type inhibition. Activity of lipoxygenase-1
towards linoleic acid at pH 9.0 was also inhibited by retinoic acids
by 32-73%. All-trans-retinoic acid and 13-cis-retinoic acid inhibited
lipoxygenase-1 activity competitively, whereas all-trans-retinol
inhibited lipoxygenase-1 activity in a mixed manner.
These findings suggest that retinoids may bind to the active site of
the enzyme or simultaneously act as an antioxidant.
Keywords
Vitamin A - Lipoxygenase - Soya - Retinol - Retinoids
International Journal for Vitamin and Nutrition Research, 1997, Heft 1 © Verlag Hans Huber, Bern
Summary
The influence of ascorbic acid (AA) on lymphocyte functions was examined in vitro and ex vivo in peripheral blood mononuclear cells (PBMC) of vitamin C-deficient pigs, which are unable to synthesise ascorbic acid. AA is accumulated to physiological levels in PBMC in vitro. The cell proliferation induced by T lymphocyte mitogens was unaltered at all AA concentrations tested (0-400 mg/ml, i.e. 0-2.3 mM). Conversely, the response to pokeweed mitogen (PWM) which activates T and B lymphocytes was significantly reduced with increasing intracellular and extracellular AA concentrations. The response to lipopolysaccharide (LPS) showed a tendency to increase at low (9 mM) and was significantly reduced at high AA concentrations (>36 mM). The IL2 production induced by PWM (but not by concanavalin A (Con A) or phytohemagglutinin (PHA)) decreased at high AA (>142 mM). In contrast, IL6 production induced by mitogens was not dependent on AA concentrations. In concordance with these results, AA-depleted PBMC which were obtained from pigs that were fed an AA-free diet, displayed an increasing response to LPS and PWM. Collectively, the data indicate that ascorbic acid selectively influences the proliferation of B lymphocytes and negatively acts on IL2 production by T lymphocytes when a threshold of saturation is exceeded.
Keywords
Vitamin C - Immune function - Interleukins - Lymphocyte proliferation - Swine
International Journal for Vitamin and Nutrition Research, 1997, Heft 1 © Verlag Hans Huber, Bern
Summary
The effect of vitamin B12 (B12)-deficiency on testicular tissue was investigated through morphological observations of the rats which had been fed on a B12-deficient soybean protein diet by pair-feeding for 100 days. Testicular B12 content was depressed distinctly by the deficiency. Testes weight and their relative weight (weight per 100 g body weight) as well, decreased significantly as compared with those of pair-feeding control rats. Although the decrease in the testicular B12 content due to B12-deficiency was compensated by the administration of cyanocobalamin (CN-B12), alleviation of the decrease in testes weight and relative testes weight was not observed under the condition of the short-term CN-B12 administration. Morphological observations of the testicular tissue in B12-deficient rats revealed atrophy of the seminiferous tubules and aplasia of sperms and spermatids, while testicular findings in both ad libitum-feeding control rats and pair-feeding control rats were normal. There was a tendency for the decrease in seminiferous tubules showing spermatogenesis to be alleviated by administration of CN-B12. The above results indicate that the morphological changes in the testicular tissue are ascribable to B12-deficiency.
Keywords
Vitamin B12 -deficiency - Pair-feeding - Testicular morphology
International Journal for Vitamin and Nutrition Research, 1997, Heft 1 © Verlag Hans Huber, Bern
Summary
Three groups of young male Wistar rats were maintained on diets consisting of 7 mg pyridoxine hydrochloride/kg diet (control and pair-fed groups) and 0 mg pyridoxine hydrochloride/kg diet (deficient group) for six weeks. The zinc status of all rats was assessed by measuring their erythrocyte zinc-metallothionein-1 (Zn-Mt-1) and plasma zinc levels. A significant difference (p < 0.001) in plasma zinc levels was observed between the deficient group and the control and pair-fed groups (1.35 mg/ml ± 0.08, 1.99 mg/ml ± 0.06 and 2.03 mg/ml ± 0.07 respectively). Erythrocyte Zn-Mt-1 levels were significantly lower in vitamin B6 deficient rats when compared to control animals. No significant difference in Zn-Mt-1 levels existed between vitamin B6 deficient and pair-fed groups suggesting that the reduced Zn-Mt-1 levels in vitamin B6 deficient rats may be due entirely to their decreased food intake (8.9 g/day compared to 15 g/day of control rats).
Keywords
Vitamin B6 - Zinc - Metallothionein - Status
International Journal for Vitamin and Nutrition Research, 1997, Heft 1 © Verlag Hans Huber, Bern
Summary
Females (n=28) and males (n=39) had their plasma analysed for selenium (Se), ubiquinone, a-tocopherol (vitamin E), the essential fatty acid (EFA) classes: omega-3 (w-3, n-3) and omega-6 (w-6, n-6) fatty acids. Selenium averaged 0.99±0.03 mmol/l and was positively related to plasma ubiquinone, a-tocopherol and the EFA index: the w-6/w-3 ratio. Food supplements (nutratherapy) with the lipophilic antioxidants ubiquinone and a-tocopherol (Q+E) had no effect on selenium but the addition of omega-3 fatty acids as a fish oil concentrate (Q+E+n-3) had (1.12±0.05 mmol/l, + 36%, p <0.001). (Q+E) and (Q+E+n-3) with the addition of selenium (200 mg or 2.5 mmol a day) raised selenium but not higher than (Q+E+n-3) itself (1.17±0.12 mmol/l, p <0.05). After (Q+E) alone, selenium was related as at base-line to both ubiquinone and a-tocopherol but not to any marker for EFA. After (Q+E+n-3), selenium was only related to ubiquinone. An unsatisfactory a-tocopherol nutratherapy was suggested as the explanation. EFA or markers for EFA were in no situation related to plasma selenium.
Keywords
Plasma selenium - Se - Antioxidant vitamins - Essential fatty acids - Ubiquinone - a-Tocopherol - Vitamin E - Omega-3 fatty acids - n-3 - Omega-6 fatty acids - n-6
International Journal for Vitamin and Nutrition Research, 1997, Heft 1 © Verlag Hans Huber, Bern
Summary
Using biochemical indices thiamin, riboflavin, pyridoxine, ascorbic acid, retinol, a-tocopherol, folic acid, cyanocobalamin, carotene and biotin status were assessed in a sample of 243 young British adults. Using conventional definitions the number of individuals whose vitamin status can be described as adequate, marginal or deficient was determined. Vitamin status was related to alcohol intake and smoking. The status of ascorbic acid, cyanocobalamin, a-tocopherol, folic acid, and in males retinol, was adequate in the majority of cases. In the cases of riboflavin and pyridoxine the status of a substantial minority was either borderline or deficient. The thiamin and biotin status of a minority of both sexes, and retinol in the females, was marginal. In males alcohol was associated with better retinol, ascorbic acid, a-tocopherol and pyridoxine status and lower levels of biotin. Lower carotene values were associated with drinking alcohol. In both sexes those who smoked had lower ascorbic acid, folic acid and carotene values. In males smoking was additionally associated with lower riboflavin and biotin; in females cyanocobalamin and a-tocopherol were lower. As all the subjects were students volunteers, care should be taken in generalizing the data to other groups.
Keywords
Ascorbic acid - Biotin - Carotene - Cyanocobalamin - Folic acid - Pyridoxine - Retinol - Riboflavin - Thiamin - a-Tocopherol - Vitamin status
International Journal for Vitamin and Nutrition Research, 1997, Heft 1 © Verlag Hans Huber, Bern
Summary
Food intake and Body Mass Index (BMI) of privately institutionalized elderly in Tehran was studied using a 5-day food intake survey and anthropometric measurements. Thirty-seven males and sixty-three females in private institutions were selected. The intake of many nutrients including protein, calcium, zinc, vitamins A, riboflavin, folic acid and cobalamin, were deficient. Almost half the subjects were under the 5th percentile of standard BMI for their age and sex, indicating chronic energy malnutrition. More attention needs to be paid to this group of vulnerable people.
Keywords
Nutritional status - Institutionalized elderly - Malnutrition
International Journal for Vitamin and Nutrition Research, 1997, Heft 1 © Verlag Hans Huber, Bern
Summary
In this paper a HPLC method for the determination of lutein,
zeaxanthin, b-cryptoxanthin, a-carotene, b-carotene and lycopene in
mixed vegetables and fruit and in human plasma is described.
The carotenoids were well separated and the separation was achieved
within fifteen minutes using a HPLC system consisting of a 5µm
Vydac 201TP54 C18 column, an UV detector, methanol-tetrahydrofuran
(95:5 v/v) as mobile phase and a flow rate of 1.0 ml/min. The
validity of the separation method was determined by evaluating the
linearity of the calibration graphs of each carotenoid (between 0.1
and 1.0 µg/ml for all compounds except lycopene between 0.1 and
0.8 µg/ml, r = 0.999) and the accuracy of the chromatographic
response (CV <10%). The reproducibility of the retention times was
also good.
In the foods samples the extraction procedure was very effective
whereas, the saponification step significantly damaged some of the
carotenoids. In the plasma the extraction and separation of these
compounds were also effective and the qualitative data obtained
comparable with those reported in literature. The use of echinenone
as internal standard helped to improve quality control.
Keywords
Carotenoids - Vegetable foods - Plasma - Extraction - HPLC
International Journal for Vitamin and Nutrition Research, 1997, Heft 1 © Verlag Hans Huber, Bern
Summary
Soluble dietary fibers include an alginate which reduces the
postprandial glycaemic response. We speculated that the cause of the
reduction of alginate on the glycaemic response is the gel formation
of alginate with dietary calcium in the stomach. The aim of the
present study was to confirm our hypothesis and to examine the effect
of the sugar composition of alginates on the glycaemic response and
the effect of continuous feeding of alginate-containing diet to rats.
Diabetic rats were made by injecting streptozotocin (STZ)
intravenously. These rats were fed 5 g of the experimental diet with
or without sodium alginate and with or without calcium after
overnight fasting. In the rats fed the diet containing both alginate
and calcium, the postprandial glycaemic response was lower than in
the rats fed other diets and gastric contents were retained as gel
form. Three b-d-mannuronic acid (M) to a-l-guluronic acid (G) (ratios
(M/G 0.5, 1.3, 2.1) of alginates were not associated with the acute
glycaemic response in STZ rats. Then, we fed normal rats with an
alginate-free or one of three respective alginate-containing diets
for 4 weeks. During the first 2 weeks of the feeding period, the
total amount of food intake of rats fed the G-rich alginate diet was
smaller than that of rats in the other dietary groups. Moreover, the
weight of the dorsal abdominal adipose tissue of rats given the
G-rich alginate diet was the lowest among the dietary groups.
We conclude that the reductive effect of alginate feeding on the
postprandial glycaemic response was not caused only by their inherent
viscosity, but also by gel formation with dietary calcium in the
stomach. Moreover, it is necessary to pay attention to the M/G ratio
of alginates for estimating their physiological effect.
Keywords
Alginate - Calcium - Gel formation - Gastric emptying - Glycaemic response
International Journal for Vitamin and Nutrition Research, 1997, Heft 1 © Verlag Hans Huber, Bern