Vitamin A deficiency and reproduction in rhesus monkeys

Mathematical modeling of serum 13C-retinol in captive rhesus monkeys provides new insights on hypervitaminosis A

Hypervitaminosis A is increasingly a public health concern, and thus noninvasive quantitative methods merit exploration. In this study, we applied the (13)C-retinol isotope dilution test to a nonhuman primate model with excessive liver stores. After baseline serum chemistries, rhesus macaques (Macaca mulatta; n = 16) were administered 3.5 mumol (13)C(2)-retinyl acetate. Blood was drawn at baseline, 5 h, and 2, 4, 7, 14, 21, and 28 d following the dose. Liver biopsies were collected 7 d before and 2 d after dosing (n = 4) and at 7, 14, and 28 d (n = 4/time) after dosing. Serum and liver were analyzed by HPLC and GC-combustion-isotope ratio MS for retinol and its enrichment, respectively. Model-based compartmental analysis was applied to serum data. Lactate dehydrogenase was elevated in 50% of the monkeys. Total body reserves (TBR) of vitamin A (VA) were calculated at 28 d. Predicted TBR (3.52 +/- 2.01 mmol VA) represented measured liver stores (4.56 +/- 1.38 mmol VA; P = 0.124). Predicted liver VA concentrations (13.3 +/- 9.7 micromol/g) were similar to measured liver VA concentrations (16.4 +/- 5.3 micromol/g). The kinetic models predict that 27-52% of extravascular VA is exchanging with serum in hypervitaminotic A monkeys. The test correctly diagnosed hypervitaminosis A in all monkeys, i.e. 100% sensitivity. Stable isotope techniques have important public health potential for the classification of VA status, including hypervitaminosis, because no other technique besides invasive liver biopsies, correctly identifies excessive liver VA stores.

Hypervitaminosis A in experimental nonhuman primates: evidence, causes, and the road to recovery

One of the great underlying assumptions made by all scientists utilizing primate models for their research is that the optimal nutritional status and health of the animals in use has been achieved. That is, no nutrient deficiency or excess has compromised their health in any detectable way. To meet this assumption, we rely on the National Research Council's (NRC's) nutritional recommendations for nonhuman primates to provide accurate guidance for proper dietary formulations. We also rely on feed manufacturers to follow these guidelines. With that in mind, the purpose of this commentary is to discuss three related points that we believe have significant ramifications for the health and well being of captive primates as well as for their effective use in biomedical research. First, our laboratory has shown that most experimental primates are likely in a state of hypervitaminosis A. Second, it is apparent that many primate diets are providing vitamin A at levels higher than the NRC's recommendation. Third, the recommendation itself is based on inadequate information about nutrient needs and is likely too high, especially when compared with human requirements.

Progesterone regulation of implantation-related genes: new insights into the role of oestrogen

Genomic profiling was performed on explants of late proliferative phase human endometrium after 24-h treatment with progesterone (P) or oestradiol and progesterone (17β-E₂+P) and on explants of menstrual phase endometrium treated with 17β-E₂+P. Gene expression was validated with real-time PCR in the samples used for the arrays, in endometrium collected from early and mid-secretory phase endometrium, and in additional experiments performed on new samples collected in the menstrual and late proliferative phase. The results show that late proliferative phase human endometrium is more responsive to progestins than menstrual phase endometrium, that the expression of several genes associated with embryo implantation (i.e. thrombomodulin, monoamine oxidase A, SPARC-like 1) can be induced by P in vitro, and that genes that are fully dependent on the continuous presence of 17β-E₂ during P exposure can be distinguished from those that are P-dependent to a lesser extent. Therefore, 17β-E₂ selectively primes implantation-related genes for the effects of P.

Repeated topical treatment, in contrast to single oral doses, with Vitamin A-containing preparations does not affect plasma concentrations of retinol, retinyl esters or retinoic acids in female subjects of child-bearing age

BACKGROUND

Vitamin A is widely used in cosmetic preparations. Given that oral Vitamin A and its metabolites present a potential reproductive risk, the present study investigated the effect of topical Vitamin A on human endogenous plasma levels of Vitamin A and its metabolites.

METHODS

Two groups of 14 female volunteers of child-bearing age were kept on a Vitamin A-poor diet and treated topically for 21 days with creams containing 0.30% retinol or 0.55% retinyl palmitate on approximately 3000 cm2 of their body surface area, amounting to a total of approximately 30,000 IU Vitamin A/subject/day. After a 12-day wash-out period, the study groups received single oral doses of 10,000 IU or 30,000 IU retinyl palmitate (RP), corresponding to the maximal EU allowance during pregnancy or three-times higher, respectively. Blood samples were collected over 24h on study days -3 (pre-study), 1, 21 (first and last days of topical treatment) and 34 (oral administration) at 0, 1, 2, 4, 6, 8, 12, 14-16 h and 24 h after treatment for determination of plasma concentrations of retinol (REL), retinyl palmitate (RP), oleate (RO) and stearate (RS), 9-cis-, 13-cis-, all-trans- (AT), 13-cis-4-oxo- or AT-4-oxo-retinoic acids (RAs).

RESULTS

With the exception of transient mild (RP-group) to moderate (REL-group) local irritation on the treatment sites, no adverse local or systemic effects were noted. On days 1 or 21 of topical treatment, no changes were measured in individual or group mean plasma Cmax, AUC0-24 h or other pharmacokinetic parameters of REL, retinyl esters or RAs relative to pre-study data. In contrast, single oral doses of RP at 10,000 IU or 30,000 IU produced dose-related and sustained increases in Cmax and AUC0-24 h values of plasma RP, RO, RS, 13-cis- and 13-cis-4-oxo-RAs, as well as a transient increase in AT-RA. In conclusion, our results provide evidence that human topical exposure to retinol- or retinyl ester-containing cosmetic creams at 30,000 IU/day and maximal use concentrations do not affect plasma levels of retinol, retinyl esters or RAs, whereas single oral doses at 10,000 IU or 30,000 IU produce significant increases in plasma retinyl esters and RAs.

The acute and chronic toxic effects of vitamin A

The acute and chronic effects of vitamin A toxicity are well documented in the literature. Emerging evidence suggests that subtoxicity without clinical signs of toxicity may be a growing concern, because intake from preformed sources of vitamin A often exceeds the recommended dietary allowances (RDA) for adults, especially in developed countries. Osteoporosis and hip fracture are associated with preformed vitamin A intakes that are only twice the current RDA. Assessing vitamin A status in persons with subtoxicity or toxicity is complicated because serum retinol concentrations are nonsensitive indicators in this range of liver vitamin A reserves. The metabolism in well-nourished persons of preformed vitamin A, provided by either liver or supplements, has been studied by several research groups. To control vitamin A deficiency, large therapeutic doses are administered in developing countries to women and children, who often are undernourished. Nevertheless, little attention has been given to the short-term kinetics (ie, after absorption but before storage) of a large dose of vitamin A or to the short- and long-term effects of such a dose given to lactating women on serum and breast-milk concentrations of retinol and its metabolites. Moreover, appropriate dosing regimens have not been systematically evaluated to ascertain the quantitative improvement in vitamin A status of the women and children who receive these supplements. The known acute and chronic effects of vitamin A toxicity have been reported previously. However, further research is needed to ascertain the areas of the world in which subclinical toxicity exists and to evaluate its effects on overall health and well-being.

Vitamin A intake of captive rhesus monkeys exceeds national research council recommendations

The specific vitamin A (VA) requirements of nonhuman primates have not been adequately determined via species-specific scientific experimentation. Recommendations are considered to be similar to human requirements, particularly for Old World monkeys. Manufacturers of primate diets add an excess of most nutrients in order to compensate for losses that occur during storage and handling. Moreover, the form of VA used in these diets is synthetic VA esters, which are readily absorbed and stored. Primates in the wild obtain much of their VA from provitamin A carotenoids, which are cleaved as needed to form active VA and are considered nontoxic, unlike preformed VA. The purpose of this study was to determine what types of feed are used at the National Primate Centers and to estimate the amount of VA that rhesus macaques are consuming. Five of the eight centers responded to a short survey that was administered through telephone and electronic mail contacts. VA intakes are well above those that are considered adequate for humans, and VA concentrations in commercially prepared standard primate diets exceed National Research Council (NRC) recommendations by as much as four times. Thus, the VA provided in primate diets should be reevaluated with regard to the concentration and form of the vitamin used.

Haemoconcentration associated with low vitamin A status can mask anaemia

As part of a pig study to elucidate the interactions between low vitamin A status and helminth infections, surprisingly, we observed higher haemoglobin levels and packed cell volumes in the pigs with low vitamin A status. A possible haemoconcentration effect, due to some disturbance in the regulation of the extracellular fluid volume, could lead to underestimation of the prevalence of anaemia in vitamin A deficient human populations. Therefore, this phenomenon needs to be further clarified in studies involving determination of plasma volumes.

Steroid and cytokine regulation of matrix metalloproteinase expression in endometriosis and the establishment of experimental endometriosis in nude mice

The cyclic expression of matrix metalloproteinases (MMPs) by human endometrium has been suggested to play a role in the invasive process necessary to establish endometriosis. The ability of progesterone exposure to inhibit endometrial MMP-3 and MMP-7 expression requires the local action of TGF beta and may also be linked to the local production of retinoic acid by stromal cells. A continuous expression of several MMPs in endometriotic lesions has been reported, indicating a failure of progesterone or locally produced factors to suppress these enzymes. To address cell-specific MMP regulation associated with endometriosis, we examined expression of MMP-3 and MMP-7 mRNA in eutopic endometrium and endometriotic lesions acquired during the secretory phase of the menstrual cycle. We examined the in vitro regulation of MMP-3 and MMP-7 protein in similar tissues. We also examined the in vitro regulation of MMP secretion by progesterone, retinoic acid, and TGF beta in endometriosis tissues relative to the establishment of experimental disease. Our studies indicate that either eutopic or ectopic tissue from women with endometriosis exhibit patterns of altered MMP regulation in vivo. A lack of responsiveness to progesterone was demonstrated in vitro, associated with a failure to suppress MMP expression and an enhanced ability of the tissue to establish experimental endometriosis. However, in vitro treatments with retinoic acid and TGF beta restored the ability of progesterone to suppress MMPs in vitro and prevented the establishment of experimental disease.

The anemia of vitamin A deficiency: epidemiology and pathogenesis

OBJECTIVE

To gain insight into vitamin A deficiency as a cause of anemia.

METHODS

Comprehensive review of the scientific literature.

RESULTS

Although vitamin A deficiency is recognized to cause anemia, 'vitamin A deficiency anemia' lacks complete characterization as a distinct clinical entity. Vitamin A appears to be involved in the pathogenesis of anemia through diverse biological mechanisms, such as the enhancement of growth and differentiation of erythrocyte progenitor cells, potentiation of immunity to infection and reduction of the anemia of infection, and mobilization of iron stores from tissues. Epidemiological surveys show that the prevalence of anemia is high in populations affected by vitamin A deficiency in developing countries. Improvement of vitamin A status has generally been shown to reduce anemia, but the actual public health impact on anemia is unclear.

CONCLUSIONS

Further work is needed to elucidate the biological mechanisms by which vitamin A causes anemia. The inclusion of anemia as an outcome measure in future micronutrient intervention studies should help provide further insight into the anemia of vitamin A deficiency.

Subtoxic hepatic vitamin A concentrations in captive rhesus monkeys (Macaca mulatta)

Although the rhesus monkey (Macaca mulatta) is a widely used experimental animal, its exact vitamin A requirement is unknown. An amount of 430-3600 IU/d [129-1080 retinol equivalents (RE)] is recommended, largely on the basis of depletion studies. Normal hepatic vitamin A appears to be 1 micromol/g liver. Our goal was to determine hepatic vitamin A concentrations of captive monkeys. Liver autopsy samples from rhesus and marmoset (Callithrix jacchus) monkeys were obtained from the Wisconsin Regional Primate Research Center. The rhesus monkeys consumed a diet with 40 IU (12 RE) retinyl acetate/g. Male and female monkeys consumed an estimated 250 and 175 g diet/d, respectively. Marmosets were fed a powder-based diet consisting of 20 IU (6 RE) retinyl acetate/g. The marmosets consumed an estimated 25 g of the diet/d. Liver samples were extracted and analyzed by HPLC. The vitamin A concentration of the rhesus monkey livers was very high at 17.0 +/- 6.3 micromol/g. The hepatic vitamin A of the marmosets was 1.25 +/- 0.58 micromol/g liver. Histologic examination of the livers revealed Ito cell hypertrophy and hyperplasia in the rhesus monkeys compared with the marmosets. Considering that the natural diet of the rhesus monkey (fruits, seeds, roots and insects) is not high in preformed vitamin A, the vitamin A content of the diet appears excessive, supplying four times the NRC recommendation and resulting in high liver stores.

Dietary factors and risk of spontaneous abortion

OBJECTIVE

This study examines the association between dietary habits and risk of spontaneous abortion.

DESIGN

Hospital-based case-control study.

SETTING

Obstetric hospitals in Milan, Italy.

SUBJECTS

Cases were: 912 women admitted for spontaneous abortion (within the 12th week of gestation). Controls were: women who gave birth at term to healthy infants on randomly selected days at the same hospitals where cases had been identified.

RESULTS

The risk of spontaneous abortion was inversely and significantly related to green vegetables, fruit, milk, cheese, eggs and fish consumption. The multivariate odds ratios (OR), for highest versus lowest levels of intake, were 0.3 for fruit, 0.5 for cheese, 0.6 for green vegetables and milk and 0.7 for fish and eggs. The major type of seasoning fats have showed a direct association with risk of miscarriage. Comparing the highest with the lowest intake, the ORs were 2.0 (95% confidence interval, CI 1.1-3.6) and 1.6 (95% CI 1.1-2.3) for butter and oil, respectively. No consistent association emerged between meat, liver, ham and carrots intake and the risk of spontaneous abortion.

CONCLUSIONS

This result suggests that a diet poor in several aspects, including vegetables and fruit, milk and dairy products, but rich in fats, may be a determinant or a correlate of increased risk of spontaneous abortion.

Gestational trophoblastic disease

BACKGROUND

Gestational trophoblastic disease consists of a group of interrelated diseases, including molar pregnancy, placental site trophoblastic tumor, and choriocarcinoma.

METHODS

Advances in the diagnosis and management of gestational trophoblastic diseases over the past 5 years were reviewed.

RESULTS

Molar pregnancy is now categorized as complete or partial on the basis of gross and microscopic histopathologic and karyotypic findings. Early detection of persistent gestational trophoblastic tumor (GTT) depends on careful postmolar gonadotropin follow-up and consideration of the diagnosis for any woman of reproductive age with unexplained gynecologic and/or systemic symptoms. Triple therapy with methotrexate, actinomycin D, and cyclophosphamide was once the preferred treatment for patients with high risk metastatic GTT but induced remission in only about 50%. Treatment with etoposide, methotrexate, actinomycin D, cyclophosphamide, and vincristine is now the preferred regimen for treatment of high risk metastatic GTT and has been shown to induce remission in about 70% of patients.

CONCLUSIONS

Important advances have been made in the diagnosis and treatment of patients with gestational trophoblastic disease, and patients can be reassured that they can anticipate normal reproductive functioning.

Maternal vitamin A restriction alters biochemical development of the brain in rats

The biochemical development of the fetal brain in relation to maternal vitamin A restriction was studied in rats. The vitamin A status of pregnant rats was varied by supplying low, medium and adequate amounts (6, 40, and 100 micrograms retinol/day/kg body weight, respectively) of vitamin A during pregnancy and suckling. The maternal vitamin A restriction caused an altered brain development in terms of tissue weight, DNA, RNA and protein levels, and biosynthesis of DNA and protein from [3H]-thymidine and [3H]-leucine, respectively. A dose-dependent effect of maternal vitamin A restriction on the metabolism of DNA, RNA and protein was noticed in the developing fetal brain of rats.

An in situ-hybridization study of the localization of retinol-binding protein and transthyretin messenger RNAs during fetal development in the rat

The patterns, and the cellular sites, of expression of the genes for retinol-binding protein (RBP) and transthyretin (TTR) were studied during early- to mid-stages of rat embryogenesis. In situ hybridization of single-stranded RNA probes to rat embryo sections revealed specific sites at which RBP messenger RNA (mRNA) and TTR mRNA were localized in rat conceptuses from 7 to 13 days of gestation. RBP and TTR mRNAs were both observed in the visceral endoderm as early as at 7 days of gestation. The transcripts were not expressed in the parietal endoderm. At 9 days of gestation, TTR mRNA was strongly detected in the visceral extraembryonic endoderm and in the foregut endoderm, whereas RBP mRNA was detected only in the visceral extraembryonic endoderm. From the 10th day to the 13th day of gestation, both transcripts were increasingly expressed in the visceral yolk sac endoderm and in the developing fetal liver, and gradually decreased in the foregut. At 11 days of gestation, TTR mRNA was first detected in the tela choroidea of the fourth ventricle in the brain; and at 13 days, the TTR mRNA was strongly evident in the developing choroid plexus of the fourth and lateral ventricles. These in situ hybridization studies with embryos at different developmental stages show that RBP and TTR mRNAs are transcribed quite early during embryogenesis. The protein products of these transcripts may play important roles in vitamin A and thyroid hormone metabolism, and in the functions that these regulatory compounds play, in the developing rat embryo.

Vitamin A supply and biochemical development of the rat heart: studies on cellular DNA, RNA and protein

The effect of restricted vitamin A supply to the mother on the biochemical development of the heart in rats has been studied. The vitamin A status of female rats was varied by supplying low, medium and adequate amounts (6, 40, 100 micrograms retinol/day/kg body weight respectively) of vitamin A during pregnancy and suckling. The vitamin A status of the mother caused an alteration in the developmental pattern of fetal heart in parameters of tissue weight, DNA, RNA and protein contents and the biosynthesis of DNA and protein from [3H]-thymidine and [3H]-leucine respectively. A dose-dependent effect of vitamin A on the metabolism of DNA, RNA and protein was observed in the developing rat hearts. Hence, emphasis should be given to the adequate availability of vitamin A to dams for the normal growth and development of fetal organs.

Dietary factors and risk of trophoblastic disease

The risk of gestational trophoblastic disease in relation to frequency of consumption of selected dietary items was evaluated with data from a case-control study conducted in Northern Italy on 148 women with histologically confirmed gestational trophoblastic disease and two control groups, one consisting of 372 obstetric control subjects and one consisting of 406 patients in the hospital for acute, nonobstetric, nongynecologic conditions. Patients with gestational trophoblastic disease tended to consume several foods less frequently, including the major sources of vitamin A and animal protein in the Italian diet. Relative risk estimates were significantly below unity in both control groups for green vegetable, carrot, liver, and cheese consumption and in the obstetric control group only for milk, meat, eggs, fresh fruit, and fish. Inverse relationships emerged between the risk of gestational trophoblastic disease and beta-carotene or retinol intake index. The trend of decreasing risk with increasing intake was significant for beta-carotene consumption. The present findings confirm that various aspects of diet may influence the risk of gestational trophoblastic disease. However, the limitation of available evidence still introduces serious uncertainties in the interpretation of these findings and suggests the potential importance of further epidemiologic and biochemical research to obtain more precise definition of specific dietary correlates of gestational trophoblastic disease.

Retinol-binding protein and transthyretin mRNA levels in visceral yolk sac and liver during fetal development in the rat

Studies were conducted to explore the synthesis of retinol-binding protein and transthyretin by embryonic and extraembryonic tissues during fetal development in the rat. The levels of retinol-binding protein mRNA and transthyretin mRNA were measured in fetal liver and in extraembryonic tissues by RNA gel blot analysis and hybridization with specific cDNA probes. Retinol-binding protein mRNA and transthyretin mRNA were both detected in the liver of fetuses at 14 days of gestation. The relative levels of these two transcripts increased during later fetal development; by the 20th day of gestation retinol-binding protein mRNA levels were comparable to those of the adult liver, while the levels of transthyretin mRNA were only 46% of those of the adult liver. Examination of the extraembryonic membranes for retinol-binding protein mRNA and transthyretin mRNA showed that these two transcripts were present specifically and only in the visceral yolk sac. The relative levels of retinol-binding protein mRNA and transthyretin mRNA in visceral yolk sac were constant from 14 to 20 days of gestation, averaging 58% and 51%, respectively, of the adult liver levels of these two transcripts. Both retinol-binding protein mRNA and transthyretin mRNA in the visceral yolk sac were found to be specifically localized in the endodermal layer. Finally, both immunoprecipitable retinol-binding protein and transthyretin were found to be synthesized and secreted by explant cultures of visceral yolk sac tissue. These data show that the visceral yolk sac is a major source of both retinol-binding protein and transthyretin in the developing fetus. Since the visceral yolk sac is a site of true placentation and nutrient transfer in the rodent, this raises the possibility that visceral yolk sac-derived retinol-binding protein and transthyretin may play important roles in the transport and delivery of retinol from the maternal blood to the developing fetus.

Risk factors for complete molar pregnancy from a case-control study

Demographic, reproductive, and dietary histories for 90 white women with complete molar pregnancy were compared in a multivariate analysis with those of 90 parous controls matched to cases by residence, birth year, and race. Women with molar pregnancy were more likely to have been born outside North America (relative risk = 1.9, p = 0.05), were more likely to have been past age 30 at time of their molar pregnancy (relative risk = 1.6, p = 0.05), and were more likely to have diets deficient in the vitamin A precursor carotene. Women with dietary scores for carotene above the control median had a relative risk for molar pregnancy of 0.6 (p = 0.02). In addition, there was a significant trend for decreasing risk for molar pregnancy with increasing consumption of carotene. Although other nutritional deficiencies in patients with complete molar pregnancy may exist, carotene is a biologically plausible candidate for a nutritional risk factor that could explain the geographic distribution of molar pregnancy.

Vitamin A and retinol-binding protein metabolism during fetal development in the rat

Studies were conducted on the metabolism and placental transport of vitamin A and plasma retinol-binding protein (RBP) during fetal development in the rat. Vitamin A accumulated in the conceptus in three phases: an early phase (days 7-9 of gestation) characterized by a high vitamin A concentration; a second phase (days 11-14) where vitamin A and RBP accumulated in parallel; and a third phase of continued vitamin A and RBP accumulation (days 16-20) in which vitamin A was stored in the fetal liver. The early phase of vitamin A accumulation may reflect a mechanism that exists to prepare the conceptus to meet the presumably higher vitamin A requirements of the critical period (days 10-14) of organ differentiation. Fetuses and placentas from retinol-deficient dams showed low levels of RBP through days 16-18 of gestation. A retinol-repletion study suggested, moreover, that the maternal retinol-RBP complex crossed the placenta. The various studies all suggest that vitamin A is transported from dam to fetus, from and after day 11, mainly by transplacental transport of maternal retinol-RBP. Finally, evidence was obtained indicating that the fetal liver begins to synthesize RBP around the 16th day of gestation and that by the 20th day, the fetal liver has a considerable capacity for RBP synthesis.