Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: KEGG:D06543 (Vitamin A)
 3,039 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A literature review of the effect of oral contraceptive (o.c.) use on various metabolic processes is presented. Several studies show an adverse effect of o.c. use on subclinical diabetes and on patients with manifest insulin-independent diabetes. Some researchers have found a beneficial effect of o.c. use on older diabetics. It has not been determined whether the estrogen or gestagen component of o.c.s is responsible for this decrease in glucose tolerance, nor has the mechanism for this effect been discovered. Changes in various plasma protein concentrations have been observed during o.c. use, which affect the blood coagulation and the blood pressure regulation systems. The estrogen component appears to be responsible for the increase in the serum triglyceride concentration during o.c. use; the mechanism is still unknown. Some studies indicate that o.c. use causes an increase in serum cholesterol levels, which could promote gall stone formation. An increase in Vitamin A concentration has been observed during o.c. use. Riboflavin, folic acid, vitamin B 12, and ascorbic acid levels have been shown to decrease during o.c. use. A decrease in pyridoxin levels during o.c. use indicates an increased metabolism of tryptophan to nicotinic acid robosyl-5-phosphate. This would cause a decrease in serotonin production, which could be a cause of the depression experienced by some o.c. users. An increase in the plasma copper and caeruloplasmin levels during o.c. use is apparently due to the estrogen component. An increase in transferrin and the serum iron levels have been observed during o.c. use. Contradictory findings are reported concerning the plasma concentration of zinc.
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PMID:[Metabolic studies under administration of oral contraceptives. A review]. 34 1

This compacted overview of the nutrition-immune response connection underscores the role of nutrition as a deterrent to infection. Malnutrition enhances the propensity to and heightens the intensity of infections by weaknening the various host defense mechanisms. Thus: 1. Deficiencies of vitamin A, niacin, riboflavin, folic acid, vitamin B12, pyridoxine, ascorbic acid, iron and protein disrupt the tissue barriers to infection. 2. Protein-calorie, folate, iron, pyridoxine and zinc deprivations markedly depress the cell-mediated immune system. 3. Deficiencies of protein, pyridoxine, folic acid, pantothenic acid, thiamine, biotin, riboflavin, niacin-tryptophan, vitamin A and ascorbic acid inhibit humoral antibody formation in mammalian systems. 4. Vitamin A lack prevents the formation of lacrimal, salivary and sweat gland lysozymes. 5. Complement, properdin, interferon and transferrin concentrations are reduced in those nutritional deficiencies that interfere with protein synthesis. 6. Protein-calorie, iron and folate deficiencies impair phagocytosis by interfering with phagocyte microbial killing power or with phagocyte production. 7. Protein, ascorbic acid and zinc deficiencies retard wound healing that prevents spread of infectious lesions.
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PMID:Nutrition and the immune response -- a review. 38 Dec 30

Studies were conducted to explore vitamin A transport in the non-mammalian vertebrates, especially Pisces, Amphibia, and Reptilia, and to isolate and partially characterize piscine retinol-binding protein. Retinol-containing proteins in fresh plasma obtained from bullfrogs and a turtle exhibited similar properties to those found in mammalian and chicken plasma: i.e., molecular weight of about 60,000-80,000 as estimated by gel filtration and binding affinity to prealbumin on human prealbumin-Sepharose affinity chromatography. In sharp contrast, vitamin A-containing proteins in plasma from larvae of bullfrogs as well as three fishes (carp, blue sharks, and young yellowtails) appeared to be present in plasma as monomeric retinol-binding proteins without any affinity to human prealbumin. On the other hand, plasma vitamin A in the lamprey (Cyclostomes) was found to exist exclusively as an ester form in association with the lipoproteins of hydrated density less than 1.21 g/ml. Piscine retinol-binding protein was isolated from pooled plasma of young yellowtails and was converted (1000-fold purification) to a homogeneous component by a procedural sequence that included gel filtration on Sephadex G-100, chromatography on SP-Sephadex, gel isoelectric focusing, and, finally, polyacrylamide gel electrophoresis. Purified piscine retinol-binding protein showed physico-chemical properties distinctly different from the mammalian and chicken retinol-binding proteins examined, i.e., a smaller molecular weight of approximately 16,000, a lower isoelectric point of 4.3, a prealbumin mobility on analytical polyacrylamide gel electrophoresis, and a lack of binding affinity for human prealbumin; however, it displayed similar characteristics in two ways: a 1:1 molar complex with retinol, and a high content of tryptophan (four residues). These results strongly suggest that the piscine retinol-binding protein is a prototype of the specific vitamin A-transporting protein in plasma of the vertebrates, being modified later in evolution, during phylogenetic development of the vertebrates, to acquire a binding site for prealbumin on the molecule.
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PMID:Vitamin A transport in plasma of the non-mammalian vertebrates: isolation and partial characterization of piscine retinol-binding protein. 56 10

Comparative 19F NMR studies were performed on rat cellular retinol-binding protein (CRBP) and cellular retinol-binding protein II (CRBPII) to better understand their role in intracellular retinol metabolism within the polarized absorptive epithelial cells (enterocytes) of the intestine. Efficient incorporation of 6-fluorotryptophan (6-FTrp) into these homologous proteins was achieved by growing a tryptophan auxotroph of Escherichia coli, harboring prokaryotic expression vectors with either a full-length rat CRBPII or CRBP cDNA on defined medium supplemented with the analog. It is possible to easily distinguish resonances corresponding to 6-FTrp-apoCRBP, 6-FTrp-CRBP-retinol (or retinal), 6-FTrp-apoCRBPII, and 6-FTrp-CRBPII-retinol (or retinal). We were thus able to use 19F NMR spectroscopy to monitor transfer of all-trans-retinol and all-trans-retinal between CRBPII and CRBP in vitro. Retinol complexed to CRBPII is readily transferred to CRBP, whereas retinol complexed to CRBP is not readily transferred to CRBPII. We estimated that the Kd for CRBP-retinol is approximately 100-fold less than the Kd for CRBPII-retinol. Transfer of all-trans-retinal occurs readily from CRBPII to CRBP and from CRBP to CRBPII. Results from competitive binding studies with retinol and retinal indicated that there is a much larger difference between the affinities of CRBP for retinol and retinal than between the affinities of CRBPII for these two ligands. However, the differences in binding specificities reflect differences in how the two proteins interact with retinol, rather than with retinal. 19F NMR analysis of recombinant isotopically labeled proteins represents a sensitive new and useful method for monitoring retinoid flux between the CRBPs in vitro.
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PMID:Fluorine nuclear magnetic resonance analysis of the ligand binding properties of two homologous rat cellular retinol-binding proteins expressed in Escherichia coli. 199 21

The state of knowledge concerning the effects of OCs (oral contraceptives) and mineral metabolism is assessed. A review of the literature indicates that OCs depress the levels of Vitamin B2, or riboflavin, Vitamin B6, or pyridoxine, folacin, Vitamin B12, Vitamin C, or ascorbic acid, zinc and elevate levels of Vitamin K, copper, and iron. The ingestion of OCs produces little effect on Vitamin E, or alpha tocopherol. Findings on the effects of OC ingestion on Vitamin A are ambiguous. OC users have 50%-80% higher serum levels of Vitamin A than nonusers; however, OC users may have a greater need for Vitamin A than nonusers. The need for riboflavin may also be higher for OC users. OC users need more pyridoxine and riboflavin is needed to oxidize pyridoxine phosphate to pyridoxal phosphate. Most studies support the contention that OC usage leads to a deficiency of Vitamin B6. Approximately 80% of all women using OCs for 6 or more months experience abnormal typtophan metabolism. In order to correct this problem, 25 mg daily, or 12 times the normal daily requirement, is needed. Some investigators recommend givng this dosage to women, who experience abnormal tryptophan metabolism, while others warn that the long-term effects of such high dosages are unknown. Most investigators recommend that OC users, with Vitamin B12 or Vitamin C deficiencies, should be given supplementary vitamins.
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PMID:Nutritional effects of oral contraceptive use: a review. 700 Oct 15

Metabolic changes caused by oral contraceptives (OCs) in terms of the vitamins pyridoxine, folacin, thiamin, riboflavin, ascorbic acid, and A and the minerals zinc and copper are discussed. Pyroxidine in the form of coenzyme pyridoxal phosphate is involved in conversion of tryptophan to niacin, and tryptophan load tests have shown that certain metabolites of B6 have increased secretion when OCs are used. Folic acid deficiency has been found in some OC users. As with pyroxidine and folacin, OC users may require supplementation of thiamin as well. When riboflavin deficiency is preexistent, OCs exacerbate the condition (this effect may be race-dependent). Vitamin A, in contrast to the B vitamins, increases in the plasma of women taking OCs, perhaps due to greater mobilization of the vitamin by the liver. OC users generally show significantly lower leukocyte and platelet levels of ascorbic acid, and supplementation may be necessary. Zinc levels generally decrease, whereas copper levels in serum significantly increase in association with OC use. At present, supplements of vitamins and minerals are recommended only for high-risk groups.
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PMID:Effect of oral contraceptive agents on vitamin and mineral requirements. 740 Apr 87

Although a thorough characterization of binding parameters is essential for application of beta-lactoglobulin as a carrier for a variety of small hydrophobic ligands, the binding parameters derived in various studies using various techniques are inconsistent. The bindings of several small ligands as detected by fluorometry and equilibrium dialysis were compared. Fluorescence spectroscopy showed that beta-ionone, retinol, and fatty acid lactones all bound in the vicinity of a tryptophan residue. Retinol and fatty acid lactone competed for the same binding site. Exclusively for ligands that quench the beta-lactoglobulin fluorescence through a resonance energy transfer mechanism, fluorometry yielded a systematically higher binding affinity than equilibrium dialysis. The binding overestimation in fluorometric measurements can be explained by oligomer formation of protein, together with an underestimation of the limiting quenching level at saturating ligand concentrations due to the use of a limited set of data points.
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PMID:Interaction of beta-lactoglobulin with small hydrophobic ligands as monitored by fluorometry and equilibrium dialysis: nonlinear quenching effects related to protein--protein association. 1136 43

Humans have evolved complex immune systems to protect against infection by pathogens. However, pathogens possess a remarkable genetic versatility that allows them to gain new vigour and so escape such population immunity. Conflicting pathogen-host objectives, therefore, lead to the evolutionary equivalent of an "arms race". Typically, in this struggle, pathogens attempt to deplete their host of specific nutrients that are essential for immune system function. After infection, the resulting deficiency of nutrient(s) may cause many of the disease symptoms and sequela. In malaria, Plasmodium falciparum, for example, depletes its host of Vitamin A, possibly resulting in blindness in some cases. However, 200,000 International Units of Vitamin A, given to children every three months can reduce significantly their susceptibility to malaria. This would seem to be a minimum child dosage for the treatment of the disease. In contrast, the Coxsackie B virus causes a selenium deficiency that may result in myocardial infarction or Keshan disease. However, table salt fortified with 15ppm anhydrous sodium selenite can cause dramatic drops in the incidence of Keshan disease, while selenium supplementation also reduces re-infarction rates. HIV-1 depletes its host of four nutrients: selenium, cysteine, glutamine and tryptophan, resulting in symptoms known as AIDS. Open and closed clinical trials in South Africa, Zambia and Uganda, involving daily adult doses of 600mcg l-selenomethione, and some 500mg l-glutamine, hydroxytryptophan and N-acetyl cysteine, however, have shown that such supplementation can reverse the symptoms of AIDS and prevent HIV-1 infected patients declining into this disease. It is obvious, therefore, that supplementation of diet with specific nutrients can reduce infection by particular pathogens. In addition, if infection still occurs, their use as a treatment may prevent many of the symptoms and sequela commonly associated with diseases such as malaria, myocardial infarction and AIDS.
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PMID:Host-pathogen evolution: Implications for the prevention and treatment of malaria, myocardial infarction and AIDS. 1759 May 22

Birth weight is an important indicator of maternal and fetal health and a predictor of health in later life. However, the determinants of variance in birth weight are still poorly understood. We aimed to identify the biological pathways, which may be perturbed by environmental exposures, that are important in determining birth weight. We applied untargeted mass-spectrometry-based metabolomics to 481 cord blood samples collected at delivery in four birth cohorts from across Europe: ENVIRONAGE (Belgium), INMA (Spain), Piccolipiu (Italy), and Rhea (Greece). We performed a metabolome-wide association scan for birth weight on over 4000 metabolic features, controlling the false discovery rate at 5%. Annotation of compounds was conducted through reference to authentic standards. We identified 68 metabolites significantly associated with birth weight, including vitamin A, progesterone, docosahexaenoic acid, indolelactic acid, and multiple acylcarnitines and phosphatidylcholines. We observed enrichment (p < 0.05) of the tryptophan metabolism, prostaglandin formation, C21-steroid hormone signaling, carnitine shuttle, and glycerophospholipid metabolism pathways. Vitamin A was associated with both maternal smoking and birth weight, suggesting a mediation pathway. Our findings shed new light on the pathways central to fetal growth and will have implications for antenatal and perinatal care and potentially for health in later life.
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PMID:Cord Blood Metabolic Signatures of Birth Weight: A Population-Based Study. 2940

Biofortification is an upcoming, promising, cost-effective, and sustainable technique of delivering micronutrients to a population that has limited access to diverse diets and other micronutrient interventions. Unfortunately, major food crops are poor sources of micronutrients required for normal human growth. The manuscript deals in all aspects of crop biofortification which includes-breeding, agronomy, and genetic modification. It tries to summarize all the biofortification research that has been conducted on different crops. Success stories of biofortification include lysine and tryptophan rich quality protein maize (World food prize 2000), Vitamin A rich orange sweet potato (World food prize 2016); generated by crop breeding, oleic acid, and stearidonic acid soybean enrichment; through genetic transformation and selenium, iodine, and zinc supplementation. The biofortified food crops, especially cereals, legumes, vegetables, and fruits, are providing sufficient levels of micronutrients to targeted populations. Although a greater emphasis is being laid on transgenic research, the success rate and acceptability of breeding is much higher. Besides the challenges biofortified crops hold a bright future to address the malnutrition challenge.
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PMID:Biofortified Crops Generated by Breeding, Agronomy, and Transgenic Approaches Are Improving Lives of Millions of People around the World. 2949 5


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