Placental transport of retinol in ewes fed high intakes of vitamin A

Twelve ewes were fed retinyl propionate equivalent to 12,000 micrograms retinol/kg body weight per day for the last two trimesters of pregnancy (group fed high vitamin A). Four ewes received a control level of 120 micrograms/kg body weight per day. Indwelling catheters were implanted surgically in fetal jugular veins and carotid arteries. Ewes or fetal lambs received [3H]retinol intravenously, and blood was sampled until parturition. The ewes fed large amounts of vitamin A maintained viable fetal lambs for 6 d less than did controls. Plasma retinyl ester concentrations were elevated in the ewes fed a high level of vitamin A but not in their fetal lambs. Rates of plasma retinol transport and clearance increased with vitamin A intake in ewes and their fetal lambs. Efficiency of placental retinol transport in the group fed high levels of vitamin A was less than one-quarter that for controls. However, placental transport rate was approximately 100 micrograms/d greater than that of controls with an equivalent amount retained by the fetoplacental unit in the group fed high vitamin A. These data indicate that placental transport of retinol is partially regulated. High maternal vitamin A intake results in high retinol transport to the fetus.     

Nonsupplemented children of Latino immigrants have low vitamin E intakes and plasma concentrations and normal vitamin C, selenium, and carotenoid intakes and plasma concentrations

OBJECTIVE: This study sought to determine and evaluate the intakes and plasma concentrations of vitamin E (alpha-tocopherol), gamma-tocopherol, vitamin C, selenium, and carotenoids (alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin, and lycopene) of nonsupplemented boys and girls, 4 to 8 years old, of Latino immigrants living in rural Nebraska. DESIGN: Dietary intakes of the Latino children were estimated. Their plasma samples (fasting) were analyzed for vitamin E, vitamin C, selenium, and carotenoid concentrations. Data were evaluated by sex. SUBJECTS: The subjects were a convenience sample of 4- to 8-year-old (n=29), apparently healthy, nonsupplemented children of Latino immigrants living in rural Nebraska. STATISTICAL ANALYSIS: Sex differences in parameter values were determined using general linear models; Pearson r was used for determining correlations. RESULTS: No significant differences in parameter values were observed by sex, with the exception of plasma lutein/zeaxanthin concentration. The majority (69%) had plasma vitamin E (alpha-tocopherol) concentrations<0.516 mg/dL (12 micromol/L), which is indicative of vitamin E inadequacy, and over half (59%) reported consuming less than the Estimated Average Requirement for vitamin E. All subjects had plasma vitamin C and selenium concentrations indicative of adequacy (>0.41 mg/dL or >23 micromol/L, and >6.32 microg/dL or >0.8 micromol/L, respectively), and consumed at least the Recommended Dietary Allowances for these nutrients. The plasma carotenoid concentrations of the children may be useful as norms. CONCLUSIONS: These children of Latino immigrants who did not take supplements had low plasma vitamin E (alpha-tocopherol) concentrations but normal plasma vitamin C and selenium concentrations. IMPLICATIONS: Dietetics professionals and others involved in health care need to work with Latino immigrant parents so that their children consume adequate amounts of vitamin E.     

Decreased resistance and immune response to Escherichia coli infection in chicks with low or high intakes of vitamin A

The effects of vitamin A excess of insufficiency on resistance to Escherichia coli infection and subsequent anti-E. coli immune response were examined in chicks. Chicks receiving depleted (0 microgram/kg), sufficient (0.85 mg/kg) or excess (1000 mg/kg) levels of vitamin A in their feed were inoculated by a subcutaneous injection of pathogenic E. coli (1 x 10(9) and 2 x 10(9) cfu per chick). Susceptibility to E. coli was determined by mortality, morbidity and immune responses (antibody production and T lymphocyte proliferation). Excess of insufficient vitamin A led to increased susceptibility of chicks of E. coli infection; this was accompanied by depressed immune responses. Chicks receiving excess vitamin A were more sensitive to E. coli than vitamin A-depleted chicks. This was reflected in higher mortality and morbidity rates and in severely depressed immune responses. In contrast to chicks receiving excess vitamin A, T lymphocyte responses (though not antibody responses) of vitamin A-depleted chicks achieved levels similar to those of vitamin A-sufficient birds with a lag period of 6 to 10 d. Therefore, reduction in resistance to E. coli infection, resulting from vitamin A excess or deficiency, probably was compounded by a delayed immune response.     

Intestinal, hepatic, and circulating vitamin K levels at low and high intakes of vitamin K in rats

The aim of the present study was to assess how high doses of dietary vitamin K influence the intestinal profile of K-vitamins in vitamin K-deficient rats, and whether the induced changes are reflected in the hepatic vitamin K store. Vitamin K-deficient rats were fed for 10 d on diets containing different forms of vitamin K, and it was determined how these diets affected the vitamin K concentration at various sites of the instestine, serum, and the liver. It was found that the absorption of phylloquinone from standard food is not more than 10%, while the absorption of pharmacological doses of oil-solubilized phylloquinone and menaquinone-4 was also far from complete (18 and 55% respectively). High intakes of phylloquinone suppress the colonic production of all higher menaquinones. High menaquinone-4 intake induces very high menaquinone-8 concentrations, both in the colonic contents as well as in the liver. These data suggest that menaquinone-4 may be converted into menaquinone-8 (but not into other menaquinones) via a metabolic pathway which has not been reported previously.     

Transfer of alpha-tocopherol from plasma to erythrocytes in vitamin E-deficient rats

The transfer of alpha-tocopherol from plasma to erythrocytes was examined using labeled alpha-tocopherol in vitamin E-deficient rats and at the same time the appearance of resistance to dialuric acid-induced hemolysis in the erythrocytes was observed. It was noticed that the transfer took place in two sequential steps. The second step seemed to correlate the appearance of resistance to dialuric acid-induced hemolysis, d-alpha and d,l-alpha-Tocopherol were compared under the same in vitro experimental conditions and no difference between them was observed in the effect on the recovery of antihemolytic activity. The difference in physiological activity between d-alpha- and d,l-alpha-tocopherol may exist other than in the transfer step. The coexistence of alpha-tocopherol and alpha-tocopherol quinone did not show any inhibiton for transfer of alpha-tocopherol from plasma to erythrocytes in vitamin E-deficient rats.     

Association between plasma and liver vitamin A levels in the calf; weanling pig, rabbit and rat; and adult goat fed fixed intakes of vitamin A.

To reexamine the relationship between plasma and liver vitamin A levels, data from various species of animals fed fixed intakes of vitamin A ester (expressed as retinol equivalents/kg liver weight/day) were vitamin A ester (expressed as retinol equivalents/kg live weight/day) were studied. The intakes ranging from deficient to toxic were for 48 calves, 4 to 17,600 micrograms; 39 pigs, 17.6 to 19,842 micrograms; 86 rabbits, 4.5 to 287 micrograms; 138 rats, 4 to 16,384 micrograms; and 40 goats, 1 to 17,640 micrograms. Following the feeding of these intakes for periods of between 5 and 133 weeks, blood and liver samples were taken for vitamin A determinations. Plasma vitamin A concentrations reached minimum values at low liver vitamin A levels whereas liver vitamin A levels reached maximum values at high plasma vitamin A concentrations. Upon elimination of data pairs at the extremes, linear regressions of log10 (total liver vitamin A) on plasma vitamin A concentrations and of plasma vitamin A concentrations on log10 (total liver vitamin A) were statistically significant. Therefore it was possible to estimate within limits the log10 (total liver vitamin A) from plasma vitamin A. Applicable limits were for the calf 8 to 46 micrograms/100 ml of plasma, for the pig 14 to 32, for the rabbit 14 to 74, for the rat 5 to 51 and for the goat 22 to 55. Simple correlation coefficients were 0.92, 0.60, 0.93, 0.92 and 0.75.     

Zinc utilization in young men fed adequate and low zinc intakes

Zinc absorption and balances were measured in six young men who were confined while participating in a 75-d metabolic study. A diet of conventional food providing either 16.5 or 5.5 mg Zn/d was fed. Apparent absorption of zinc was calculated from the zinc balance data and from the absorption of a zinc stable isotope added to the diet. The apparent zinc absorption calculated from the isotope data was about 25% when 16.5 mg zinc was fed; it increased to about 53 and 49% after 13 and 42 d, respectively, when 5.5 mg zinc was fed. Total zinc absorption fell from 4.1 mg/d to 2.7-2.9 mg/d during the low zinc period, however. This zinc absorption was sufficient to maintain crude zinc balances in five of the six subjects. Neither serum nor urinary zinc levels changed significantly during the period of feeding low levels of zinc. It appears that zinc absorption readily responds to changes in dietary zinc and that an intake of 5.5 mg Zn/d for about 8 wk does not cause serum or urinary zinc level to fall.     

Vitamin A alcohol and vitamin A palmitate transfer from ewes to lambs.

The effects of pre-partum intravenous injections of vitamin A alcohol and vitamin palmitate on vitamin A levels in the plasma and livers of newborn lambs and in colostrum were studied with twenty mature Romney ewes. Injecting ewes with 250000 IU of vitamin A alcohol significantly (P less than .05) increased vitamin A levels in the blood (77%) and livers (75%) of newborn lambs. Differences between effect of vitamin A alcohol and vitamin A palmitate on either blood or liver levels in lambs were not significant. Transfer of injected vitamin A to lamb liver was inefficient (0.37% for palmitate, 0.12% for alcohol). There was 52% more vitamin A in colostrum from alcohol-injected than from palmitate-injected ewes. Although consistent with a postulation of preferential mammary transfer of vitamin A alcohol, this difference was not statistically significant (P greater than .05).     

Plasma-Saturating intakes of vitamin C confer maximal antioxidant protection to plasma.

OBJECTIVE: Supplemental vitamin C has been shown to reduce oxidative damage in vivo, yet the dose-response relationship between vitamin C intake and antioxidant protection is not known. This report examined blood indicators of oxidative stress in subjects consuming graded doses of vitamin C, from 75 to 2,000 mg/day. METHODS: Ten healthy, non-smoking men and women (26.1 +/- 2.1 years) were recruited from a campus population. During the ten-week study, subjects limited fruit and vegetable consumption (< or = 3 servings/day) and consumed a multivitamin and mineral pill daily. Beginning at week 3, subjects ingested either a vitamin C (n = 8) or placebo (n = 2) capsule, which were identical in appearance and taste. The content of the vitamin C capsule increased every two weeks (from 250 mg at weeks 3-4 to 500 mg, 1,000 mg. and 2,000 mg at weeks 5-6. 7-8. 9-10, respectively). Fasting blood samples were collected at two-week intervals and analyzed for vitamin C, total lipid hydroperoxides and Heinz bodies in packed erythrocytes incubated 24 hours at 37 degrees. RESULTS: Plasma vitamin C rose 55% in vitamin C-supplemented subjects by the end of the ten-week treatment (p < 0.05), and measures of oxidative stress decreased 60% to 90% (8.1 +/- 0.6 to 3.5 +/- 0.4 nmol/mL and 69.1 +/- 7.8% to 6.7 +/- 6.0% for total lipid hydroperoxides and Heinz bodies, respectively). Significant decreases in markers of oxidative stress were noted at the 500 mg, 1,000 mg and 2,000 mg dosages versus placebo. Antioxidant protection was similar at the 1,000 mg and 2,000 mg dosage. CONCLUSIONS: These data indicate that the antioxidant protection afforded by short-term vitamin C supplementation is maximal at the 500-1,000 mg dosage range.     

Dietary vitamin A modulates the concentrations of RRR-alpha-tocopherol in plasma lipoproteins from calves fed milk replacer

The practice of supplementing milk replacers fed to neonatal calves with high concentrations of vitamin A has raised concerns regarding the effect of excess vitamin A on the bioavailability of vitamin E. A 4 x 2 factorial experiment evaluated the effects of four dietary amounts of vitamin A [0, 1.78 [National Research Council (NRC)(6) requirement, control], 35.6 and 71.2 micromol daily as retinyl acetate] and two forms of vitamin E (RRR-alpha-tocopherol and RRR-alpha-tocopheryl acetate, 155 micromol daily) on plasma RRR-alpha-tocopherol and RRR-gamma-tocopherol and RRR-alpha-tocopherol associated with plasma lipoproteins (Lp) from milk replacer-fed Holstein calves from birth to 28 d of age. The VLDL, LDL, HDL and very high-density lipoprotein (VHDL) fractions were separated by ultracentrifugal flotation, and the amount of vitamin E associated with each fraction was determined by normal-phase HPLC. The amount and distribution of RRR-alpha-tocopherol in Lp fractions were unaffected by the form of dietary vitamin E. Plasma and Lp RRR-alpha-tocopherol concentrations increased with age (P < 0.0001) and were maximal at 28 d of age. Concentrations of RRR-alpha-tocopherol associated with Lp were 25% (P < 0.01) to 39% (P < 0.0001) lower in calves fed 35.6 and 71.2 micromol of vitamin A daily than in control calves at 28 d of age. The RRR-gamma-tocopherol concentrations were unaffected by dietary vitamin A (P >/= 0.05). In conclusion, dietary vitamin A modulated the amount and distribution of RRR-alpha-tocopherol in the circulation of milk replacer-fed neonatal calves. Because of the essential antioxidant role of vitamin E, the health-related consequences associated with the depression of the LP RRR-alpha-tocopherol concentrations in calves fed vitamin A at 35.6 and 71.2 micromol need to be investigated.     

Alteration of pancreatic enzyme activities in small intestine of rats fed a high fructose, low copper diet

This study describes the progressive effects on pancreatic enzyme activities from washings of the small intestine of rats fed diets containing either 62% starch (S) or fructose (F), with 0.6 mg copper/kg diet (-Cu) or 6.0 mg copper/kg diet (+Cu) from 21 to 61 d of age. Hepatic copper concentration of the copper-deficient groups was 50% of that of the copper-supplemented groups. Body and relative pancreatic weights were lower in the F-Cu dietary group than in any other group. Relative liver weight was significantly higher in the fructose dietary groups than in the starch dietary groups. There were significant carbohydrate (CHO) X week and Cu X week interactions for luminal amylase activities and the CHO X Cu X week interaction was significant for luminal lipase and trypsin activities. The lowest enzyme activities were observed in the F-Cu-fed rats. The CHO X week interaction was significant for chymotrypsin with the lowest enzyme activities in the fructose-fed rats. It appears that high dietary fructose and low dietary copper interact to produce greatly reduced pancreatic enzyme activities in small intestinal washings. We speculate that subsequent digestive and absorptive abnormalities during a period of rapid growth may account for the severe morbidity and mortality in copper-deficient, fructose-fed rats.     

Lung retinyl ester is low in young adult rats fed a vitamin A deficient diet after weaning, despite neonatal vitamin A supplementation and maintenance of normal plasma retinol

Although it is understood that plasma retinol concentration is not proportional to the concentration of vitamin A stored in liver, plasma retinol still is often used as an indicator of vitamin A status. An aim of vitamin A supplementation strategies is to maintain plasma retinol concentration in a range considered adequate, generally >1.05 micromol/L in humans, with some adjustment for age. In the present study in rats, we addressed the following question: Does lung vitamin A increase postnatally, as is observed in rats fed a vitamin A-adequate diet, if plasma retinol is maintained at approximately 1 micromol/L by supplementation at neonatal age, but the weaning diet is deficient in vitamin A? We treated rats on postnatal d 6, 7, and 8 with placebo (oil), vitamin A, retinoic acid (RA), and a nutrient-metabolite combination of vitamin A and RA, VARA, after which tissues were analyzed on d 9. Other rats treated identically as neonates were fed a vitamin A-deficient diet from 3-9 wk of age, and in parallel, another group of rats was fed a vitamin A-adequate diet. Although supplementation with vitamin A or VARA elevated liver and lung retinyl esters (RE) on d 9 (P < 0.0001), and prevented the fall in plasma retinol to <1 micromol/L by 9 wk of age, when the diet was vitamin A-deficient, lung RE fell to 28% of the concentration present in the lungs of rats fed the vitamin A-adequate diet (P < 0.0001). We infer that the lungs depend, at least in part, on the uptake of dietary vitamin A, probably from chylomicrons, to develop RE stores in the postweaning growth period.     

Upake of plasma lipids by extrahepatic tissues of vitamin A fed rats.

The uptake of newly synthesized plasma lipids from intraportally injected palmitate 1(-14)C by heart, kidney and adipose tissues of rats fed 33 mg retinol for 2 days have been studied. The uptake of plasma lipids by adipose tissues and heart was decreased and that by kidney increased in rats fed retinol as compared to the controls.     

Influence of dietary fats and vitamin E on plasma and hepatic vitamin A and beta-carotene levels in rats fed excess beta-carotene

Effects of different dietary lipids and excess vitamin E on plasma and hepatic concentrations of beta-carotene were evaluated in rats fed diets containing a large excess (0.2%) of beta-carotene. Male weanling Wistar Kyoto rats were fed beta-carotene-supplemented diets containing various dietary lipids as follows: Group I, a saturated fat (coconut oil); Group II, a monounsaturated fat (olive oil); Group III, a polyunsaturated fat rich in omega-6 fatty acids (safflower oil); Group IV, same as Group III plus vitamin E; and Group V, a polyunsaturated fat rich in omega-3 fatty acids (menhaden oil). All diets contained 2% safflower oil to provide sufficient amounts of linoleic acid (an essential fatty acid). Rats were killed after six weeks of feeding the various diets, and the concentrations of beta-carotene and vitamin A were determined in plasma and liver. Plasma vitamin A levels were not altered by any of the dietary lipids or by an excess of vitamin E. The concentrations of beta-carotene in plasma were the lowest in rats fed the diet containing menhaden oil. The feeding of the diet containing an excess of vitamin E also resulted in a significant decrease in plasma beta-carotene concentration. Similarly, the hepatic beta-carotene concentration was also reduced to about one-half in rats fed the diet containing an excess of vitamin E. Liver beta-carotene concentration was higher in Groups II and III than in the other three dietary groups. Hepatic vitamin A concentrations were also affected by the type of dietary fat.(ABSTRACT TRUNCATED AT 250 WORDS)