Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024523 (malabsorption)
 7,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Zinc is essential for many metabolic and enzymatic functions in man. Deficiency of zinc in man has now been recognized to occur not only as a result of nutritional factors, but also in various disease states, including malabsorption syndromes, acrodermatitis enteropathica, Crohn's disease, alcoholism and cirrhosis of the liver. The deficiency state in human subjects exists as a spectrum extending from mild to severe degree. The clinical manifestations of mild zinc deficiency include oligospermia, weight loss and hyperammonaemia. Moderate zinc deficiency is characterized clinically by growth retardation, hypogonadism in males, skin changes, poor appetite, mental lethargy, delayed wound healing, taste abnormalities and abnormal dark adaptation. In severe zinc deficiency states, bullous-pustular dermatitis, alopecia, diarrhoea, emotional disorders, weight loss, intercurrent infections, hypogonadism in males and, if unrecognized, death have been observed. Zinc is needed for the functions of over 100 enzymes. It is essential for DNA, RNA and protein synthesis and, as such, is important for cell division. Zinc is an inducer of mRNA of metallothionein, a protein which may have an important role in the regulation of intestinal zinc absorption. Zinc has a specific effect on testes in animals and man. Recent reports indicate that in human subjects thymopoietin may be zinc dependent and in animal studies somatomedin may be affected adversely due to dietary zinc restriction. Zinc plays an important role in the protection of cell membrane integrity and may be protective against free radical injury. Zinc is known to compete with cadmium, lead, copper, iron and calcium for similar binding sites. In the future, a potential use of zinc may be to alleviate toxic effects of cadmium and lead in human subjects. Recent evidence suggests that thymic-dependent lymphocytes (T cells are zinc dependent. T-helper and suppressor cells, T-effector cells and T-natural killer cells appear to be zinc dependent. Zinc is also essential for some of the neutrophil functions. Thus, it appears that zinc may play an important role in immunity. One may suggest that some of the clinical features of cirrhosis of the liver, such as testicular atrophy, loss of body hair, night blindness, poor wound healing, poor appetite, susceptibility to infections and enhanced sensitivity to drugs, may be related to conditioned deficiency of zinc, future studies are required to determine whether or not zinc supplementation is beneficial to these patients.
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PMID:The role of zinc in gastrointestinal and liver disease. 661 39

Giardia lamblia undergoes surface antigenic variation. The variant-specific surface proteins (VSPs) are a distinct family of cysteine-rich proteins. Characteristically, cysteine residues occur mostly as CXXC tetrapeptides. Four of the reported five VSPs contain a putative metal-binding domain that resembles other metal-binding motifs; the fifth is closely related but lacks an essential histidine. Three different native VSPs bound Zn2+. Co2+, Cu2+, and Cd2+ inhibited Zn2+ binding. Analysis of recombinant VSP fusion proteins showed that the putative binding motif bound Zn2+. Surprisingly, peptide fragments from other regions of the VSP contain numerous CXXCXnCXXC motifs that also bound Zn2+. Analysis of deduced amino acid sequences showed well-conserved CXXC spacing in three out of five VSPs, suggesting conservation of structure despite amino acid sequence divergence. The function of VSPs is unknown, but by binding Zn2+ or other metals in the intestine, VSPs may contribute to Zn2+ malnutrition or inhibition of metal-dependent intestinal enzymes, which would lead to malabsorption, a well-known consequence of giardiasis.
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PMID:Variant-specific surface proteins of Giardia lamblia are zinc-binding proteins. 851 91

Cadmium compounds are widely spread in the environment. Animal exposure to cadmium compounds occurs mainly through foods or drinks contaminated by this metal. Cadmium has been shown to produce several negative effects on the gastrointestinal tract such as inhibition on sugars and amino acids absorption. The aim of the present work was to study the inhibitory characteristics of cadmium on L-threonine intestinal absorption in rabbits in order to understand about this malabsorption of nutrients. Our results show that L-threonine tissue accumulation as well as mucosal to serosal transepithelial fluxes are decreased in a dose-dependent manner in rabbit jejunum. Amino acid diffusion across the intestinal epithelium was not affected by cadmium. A noncompetitive mechanism and a partial reversion by dithioerythritol (thiol groups protector) is described for this inhibition.
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PMID:Inhibition of L-threonine intestinal absorption in rabbits by cadmium. 877 54

High oral intake of cadmium via food or drink in a single dose by humans gives rise to vomiting, abdominal pain, and diarrhea. Concentrations of cadmium in drinks giving rise to such symptoms have been 16 mg/liter and higher corresponding to doses of 3 mg and higher. Longer term intakes of food (rice) with concentrations around 1 mg/kg corresponding to daily intakes of 600 micrograms have given rise to some less pronounced symptoms including signs of malabsorption. Reproductive and developmental effects have been observed in animal experiments at oral and other exposures. The present provisional tolerable weekly intake (PTWI) for Cd is 500 micrograms (a weekly intake of 7 micrograms/kg body wt), corresponding to a daily intake of 70 micrograms or 1 microgram per kg body wt. Recent data demonstrating renal dysfunction in humans at even lower lifelong oral exposures indicate that the PTWI needs to be lowered in the future. An estimated lowest-observed-adverse-effect level (LOAEL) for symptoms from the gastrointestinal tract in humans after intake of a single oral dose is 43 micrograms/kg body wt. If a safety factor of 3-10 is used based on LOAEL, a tolerable single dose would be 0.3-1 mg (4 to 14 micrograms/kg body wt). For longer time exposures (months-a few years) daily intakes of 200 micrograms (3 micrograms/kg body wt) may be tolerated without obvious gastrointestinal symptoms or signs. At present, there is no convincing human evidence that such doses can cause reproductive or developmental effects, but since such effects have been reported in animals, it may be advisable not to exceed a daily intake of 1 microgram/kg body wt for such potentially sensitive subsections of the population as children and women who are pregnant or lactating. Any excursions above the PTWI need to be compensated for by a corresponding period with intake below the PTWI in order for the cumulative dose to be low enough to avoid the long-term effects of cadmium on the kidney.
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PMID:Excursions of intake above ADI: case study on cadmium. 1059 15

Measuring heavy metal levels in the urine is an accepted method for assessing the presence of a heavy metal burden in an individual. Random samples (without a flushing agent) are excellent for showing current exposures, as they reflect the level of heavy metals in the bloodstream during the hours immediately before bladder voiding. Samples taken after using a heavy metal mobilizing agent are a reflection of total body burden. Part 1 reviewed the benefits of doing pre-flush (baseline) testing utilizing the published Centers for Disease Control (CDC) heavy metal normal ranges for interpretation that allow the clinician to identify current exposures to lead and mercury and to identify cadmium toxicity. In part 2 the benefits of doing both pre- and post-challenge testing are reviewed. Information gleaned from performing both tests is unparalleled in allowing the clinician to identify which chelating agent will be most effective for the patient. If oral agents are employed, then possible absorption problems can be identified. Since none of these benefits are realized with only post-flush testing, it is recommended that clinicians do heavy metal testing both before and after a challenge with an effective and proven heavy metal mobilizing agent. The pitfalls of oral chelation in the case of malabsorption syndromes, such as gluten intolerance, are also discussed.
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PMID:The benefit of pre- and post-challenge urine heavy metal testing: part 2. 1959 21