Trace Elements - Chemistry PDF

CHROMIUM CHEMISTRY essential trace element that enhances the action of insulin in the hexavalent (Cr61) form it is a strong oxidant that can cause tissue damage DIETARY SOURCES Processed meats, whole grain products, green beans, broccoli, and some spices ABSORPTION, TRANSPORT, METABOLISM AND E...

CHROMIUM CHEMISTRY essential trace element that enhances the action of insulin in the hexavalent (Cr61) form it is a strong oxidant that can cause tissue damage DIETARY SOURCES Processed meats, whole grain products, green beans, broccoli, and some spices ABSORPTION, TRANSPORT, METABOLISM AND EXCRETION Absorption is increased marginally by ascorbic acid, amino acids, oxalate, and other dietary factors. After absorption, Cr binds to plasma transferrin. It then concentrates in human liver, spleen, other soft tissue, and bone. Running and resistive exercises increase urine Cr excretion FUNCTIONS essential trace element that enhances the action of insulin DEFICIENCY Insulin-resistant glucose intolerance, weight loss, and in some cases neurologic deficits Increased CVS risk TOXCICITY Hexavalent Cr (Cr^6+^) is a recognized carcinogen, and industrial exposure to fumes and dusts containing this metal is associated with increased incidence of lung cancer, dermatitis, skin ulcers, and hypersensitivity reactions Hexavalent Cr is more efficiently absorbed than Cr31, and its toxicity and carcinogenic effects involve reduction of Cr61 to Cr31 by cysteine, with formation of intracellular DNA adducts LAB ASSESSMENT A beneficial response of glucose-intolerant patients to Cr supplementation is presently the only means of confirming Cr deficiency No practicable method of assessing intracellular Cr depletion is yet available Elevated plasma chromium may be a good indicator of recent dietary of or excessive exposure to chromium. Graphite furnace AAS with Zeeman correction and ICP-MS are the two common methods for measuring chromium in serum or urine +-----------------------------------+-----------------------------------+ | COBALT | | +===================================+===================================+ | CHEMISTRY | Cobalt (Co) is essential for | | | humans only as an integral part | | | of vitamin B12 | | | | | | Microflora of the human intestine | | | cannot use Co to synthesize | | | physiologically active cobalamin | +-----------------------------------+-----------------------------------+ | FUNCTIONS | Erythropoiesis can be stimulated | | | by inorganic Co ions. t Co21 ion | | | stabilizes the hypoxiainducible | | | transcription factors (HIFs) that | | | increase the expression of the | | | erythropoietin gene (EPO) | +-----------------------------------+-----------------------------------+ | DEFICIENCY | Vitamin B12 | +-----------------------------------+-----------------------------------+ | TOXCICITY | Increased exposure from | | | industrial uses, particularly | | | with hard metal drilling and | | | cutting blades, leads to high | | | urinary Co concentrations | | | | | | Increases are also associated | | | with hip prostheses | +-----------------------------------+-----------------------------------+ | LAB ASSESSMENT | Co status is usually assessed | | | through measurement of vitamin | | | B12 or cobalamin | | | | | | Concentrations in biological | | | fuids and tissues can be | | | determined by ICP-MS. | +-----------------------------------+-----------------------------------+ +-----------------------------------+-----------------------------------+ | MANGANESE | | +===================================+===================================+ | CHEMISTRY | associated mainly with the | | | formation of connective and bony | | | tissue, with growth and | | | reproductive functions, and with | | | carbohydrate and lipid metabolism | +-----------------------------------+-----------------------------------+ | DIETARY SOURCES | whole grain foods, nuts, leafy | | | vegetables, soy products, and | | | teas | +-----------------------------------+-----------------------------------+ | ABSORPTION, TRANSPORT, METABOLISM | absorbed from the small intestine | | AND EXCRETION | | | | Mn is transported in portal blood | | | to the liver bound to albumin. It | | | is exported to other tissues | | | bound to transferrin | | | | | | Excretion of Mn occurs primarily | | | via bile into feces, with urine | | | output being very low and not | | | sensitive to dietary intake. | +-----------------------------------+-----------------------------------+ | FUNCTIONS | Acts as a nonspecifc enzyme | | | activator. Mn21 ions can be | | | replaced by Mg21, Co21, and other | | | cations during the activation of | | | some enzymes | | | | | | Superoxide dismutase Mn-dependent | | | SOD is a mitochondrial enzyme | | | that is an important factor in | | | limiting oxygen toxicity | | | | | | Pyruvate carboxylase. This enzyme | | | acts in combination with | | | phosphoenol pyruvate (PEP) | | | carboxykinase, an enzyme that is | | | activated by Mn ions. These | | | enzymes are required to catalyze | | | the formation of PEP, from | | | pyruvate, a key reaction in the | | | hepatic synthesis of glucose | | | | | | Arginase | +-----------------------------------+-----------------------------------+ | DEFICIENCY | Overt Mn defciency has not been | | | documented in humans eating | | | natural diets | +-----------------------------------+-----------------------------------+ | TOXCICITY | Neurologic symptoms resembling | | | Parkinson disease develop slowly | | | over a period of months or years | | | | | | patients with severe liver | | | disease may have neurologic and | | | behavioral signs of Mn | | | neurotoxicity resulting from | | | failure to excrete Mn in bile | +-----------------------------------+-----------------------------------+ | LAB ASSESSMENT | e biomonitoring of Mn relies on | | | the analysis of whole blood Mn | | | concentrations, which are highly | | | variable among human population | | | and are not strictly correlated | | | with Mn-induced neurotoxicity | | | | | | Whole blood Mn concentrations are | | | not responsive to dietary | | | depletion, but measurements of | | | serum Mn, lymphocyte Mn SOD | | | activity, and blood arginase are | | | potentially useful when possible | | | nutritional depletion is | | | assessed, although these are | | | rarely performed in clinical | | | practice. Whole blood Mn and | | | serum Mn in combination with | | | brain MRI scans and neurologic | | | assessment are used to detect | | | excessive exposure. Manganese in | | | whole blood and plasma or serum | | | can be determined by standard | | | graphite furnace AAS (GFAAS) or | | | by ICP-MS | +-----------------------------------+-----------------------------------+ +-----------------------------------+-----------------------------------+ | MOLYBDENUM | | +===================================+===================================+ | CHEMISTRY | Molybdenum enzymes are | | | ecologically vital, facilitating | | | important carbon, nitrogen, and | | | sulfur cycles | +-----------------------------------+-----------------------------------+ | DIETARY SOURCES | Legumes, such as peas, lentils, | | | and beans | +-----------------------------------+-----------------------------------+ | ABSORPTION, TRANSPORT, METABOLISM | Urine output directly reflects | | AND EXCRETION | the dietary intake of mo, with | | | stable isotope studies at high | | | and low concentrations of intake | | | indicating renal homeostatic | | | regulation | +-----------------------------------+-----------------------------------+ | FUNCTIONS | Sulfte oxidase, xanthine | | | dehydrogenase, and aldehyde | | | oxidase, require Mo as a | | | cofactor. | +-----------------------------------+-----------------------------------+ | DEFICIENCY | Mo defciency has not been | | | observed in healthy people | | | consuming a normal diet | | | | | | Rare recessive inherited diseases | | | usually early demise | | | | | | Biochemical diagnosis has been | | | made by detection of excess | | | sulfte in urine using the | | | Merckoquant Sulfte Dipstick test | | | Samples should not be evaluated | | | until at least 10 days after | | | birth and should be tested within | | | 10 minutes of collection. Mo | | | cofactor defciency can also be | | | identifed by fnding a low plasma | | | uric acid. Specialized centers | | | offer biochemical prenatal | | | diagnosis on chorionic villous | | | samples | +-----------------------------------+-----------------------------------+ | TOXCICITY | Mo compounds have low toxicity in | | | humans. | | | | | | Excess Mo intake induces Cu | | | defciency in ruminants by | | | blocking absorption through | | | formation of an insoluble | | | thiomolybdate-copper complex. | | | This is the basis for the use of | | | ammonium molybdate in the | | | management of Wilson disease | +-----------------------------------+-----------------------------------+ | LAB ASSESSMENT | Whole blood and serum or plasma | | | Mo concentrations are too low to | | | be used to detect deficiency | | | | | | Measuring urate or sulfte in the | | | urine is the most valuable means | | | of confirming Mo cofactor | | | disorder or possible Mo | | | deficiency by detecting changes | | | in sulfur and purine metabolism | | | | | | ICP-MS, studies using stable Mo | | | isotopes are now possible. This | | | technique has been used to | | | investigate absorption and | | | excretion of Mo during depletion | | | and repletion studies | +-----------------------------------+-----------------------------------+ +-----------------------------------+-----------------------------------+ | SELENIUM | | +===================================+===================================+ | CHEMISTRY | A constituent of the enzyme | | | glutathione peroxidase and is | | | considered an essential element | | | for humans; it is believed to be | | | closely associated with vitamin E | | | in its functions | | | | | | biologically active compounds | | | contain selenocysteine, where Se | | | is substituted for sulfur in | | | cysteine. | | | | | | Se in selenomethionine makes up | | | about half of the total dietary | | | intake and is made available for | | | selenocysteine synthesis when the | | | methionine pathways catabolize | | | selenomethionine | +-----------------------------------+-----------------------------------+ | DIETARY SOURCES | Selenomethionine from plants that | | | take the element up from the soil | +-----------------------------------+-----------------------------------+ | ABSORPTION, TRANSPORT, METABOLISM | Ingested Se compounds, selenate, | | AND EXCRETION | selenite, selenocysteine, and | | | selenomethionine, are metabolized | | | largely via selenide | | | | | | Intestinal absorption of various | | | dietary forms of Se is efficient | | | but is not regulated | | | | | | Ingested Se compounds, selenate, | | | selenite, selenocysteine, and | | | selenomethionine, are metabolized | | | largely via selenide that may be | | | associated with a chaperone | | | protein before being converted to | | | selenophosphate, which is an | | | important precursor in the | | | synthesis of selenocysteine | | | proteins | | | | | | The concentrations of Se in whole | | | blood and in plasma and/or serum | | | are related to dietary intake. | | | | | | Urinary output of Se is the major | | | route of excretion and refects | | | recent dietary intake | +-----------------------------------+-----------------------------------+ | FUNCTIONS | More than 30 biologically active | | | selenocysteine containing | | | proteins: | | | | | | Glutathione peroxidase use | | | reducing power of glutathione to | | | remove an oxygen atom from | | | hydrogen peroxide and lipid | | | hydroperoxides | | | | | | Iodothyronine deiodinase | | | | | | Thioredoxin reductases | | | | | | Selenophosphate synthetase | | | | | | Selenoprotein P | +-----------------------------------+-----------------------------------+ | DEFICIENCY | MUSCULOSKELETAL: | | | | | | - White Muscle Disease | | | | | | - Affects sheep and cattle | | | | | | - Requires both selenium | | | deficiency and oxidative | | | stress/vitamin E | | | deficiency | | | | | | - Myopathy | | | | | | - Affects cardiac and | | | skeletal muscle in lambs | | | and calves | | | | | | - Occurs with combined | | | selenium and vitamin E | | | deficiency | | | | | | CARDIAC: | | | | | | - Keshan Disease | | | | | | - Presents as | | | cardiomyopathy | | | | | | - Prevalent in | | | selenium-depleted regions | | | of China | | | | | | - Shows seasonal variations | | | | | | - May involve virulent | | | Coxsackie virus strain | | | | | | IMMUNOLOGICAL: | | | | | | - AIDS/HIV | | | | | | - May influence progression | | | from HIV to AIDS | | | | | | - Impairs antioxidant | | | defenses | | | | | | - Studies in Tanzania | | | showed selenium | | | supplements reduced | | | mortality in children \>6 | | | weeks | | | | | | - Did not improve HIV | | | disease progression in | | | pregnant women | | | | | | REPRODUCTIVE: | | | | | | - Male Fertility Issues | | | | | | - Affects testosterone | | | synthesis | | | | | | - Impacts sperm viability | | | | | | - Required for sperm | | | maintenance and | | | reproductive success | | | | | | NEUROLOGICAL: | | | | | | - Mood Disorders | | | | | | - Presents with anxiety, | | | confusion, and hostility | | | | | | - Brain prioritized during | | | selenium depletion | | | | | | - Results in altered | | | neurotransmitter turnover | | | | | | - Optic/Peripheral Neuropathy | | | | | | - Major epidemic in Cuba | | | affected \>50,000 | | | individuals | | | | | | - Associated with multiple | | | micronutrient | | | deficiencies | | | | | | INFLAMMATORY CONDITIONS: | | | | | | - Asthma | | | | | | - Low serum selenium levels | | | observed | | | | | | - Limited benefit from | | | supplementation | | | | | | - Arthritis and Pancreatitis | | | | | | - Positive effects reported | | | from supplementation | | | | | | - SIRS (Systemic Inflammatory | | | Response Syndrome) | | | | | | - High-dose selenium | | | supplements over 9 days | | | reduced mortality in | | | severely ill patients | | | | | | - Results not confirmed in | | | all studies | | | | | | CANCER RISK: | | | | | | - Liver Cancer | | | | | | - 35% reduction in | | | incidence with | | | selenium-enriched salt in | | | Chinese study | | | | | | - Reduced development in | | | chronic hepatitis B | | | patients with | | | selenium-enriched yeast | | | (2-year follow-up) | | | | | | - Prostate Cancer | | | | | | - SELECT trial showed no | | | prevention with selenium | | | alone or combined with | | | vitamin E | | | | | | SPECIAL SITUATIONS: | | | | | | - Severe Burns | | | | | | - Considerable selenium | | | losses in wound exudates | | | | | | - Supplementation with | | | selenium, zinc, and | | | copper reduces | | | respiratory infection | | | | | | - Intensive Care | | | | | | - Mixed results with | | | supplementation | | | | | | - No definitive | | | recommendations for | | | high-dose supplements | +-----------------------------------+-----------------------------------+ | TOXCICITY | Clinical signs of selenosis | | | include garlic odour on the | | | breath, hair loss, nail damage, | | | nervous system and skin | | | disorders, poor dental health, | | | and paralysis in extreme cases | | | | | | Symptoms of Se toxicity vary | | | among individuals and are | | | dependent on several factors such | | | as dose, type, and form of Se | | | ingested and length of time the | | | product was used. | | | | | | Symptoms of Se poisoning can | | | include significant hair loss, | | | muscle cramps, nausea, vomiting, | | | diarrhoea, joint pain, fatigue, | | | fingernail changes, and | | | blistering skin | | | | | | Nail changes are the most common | | | sign of chronic Se poisoning | | | nails become brittle, and white | | | spots and longitudinal streaks | | | appear on the surface | +-----------------------------------+-----------------------------------+ | LAB ASSESSMENT | 1. Plasma/Serum Selenium | | | | | | - Methods: | | | | | | - Fluorometry (post | | | acid digestion) | | | | | | - Graphite Furnace | | | Atomic Absorption | | | Spectroscopy (GFAAS) | | | | | | - Inductively Coupled | | | Plasma Mass | | | Spectrometry | | | (ICP-MS) - gold | | | standard for routine | | | labs | | | | | | 2. Selenium-Containing Proteins | | | | | | - Glutathione Peroxidase: | | | | | | - GSHPx-3 | | | (extracellular/plasma | | | ) | | | | | | - GSHPx-1 (RBC) | | | | | | - Enzymatic assay using | | | tert-butyl peroxide | | | substrate (preferred | | | over H2O2 due to | | | minimal catalase | | | interference) | | | | | | - Selenoprotein P: | | | | | | - Quantification via | | | immunological methods | | | | | | - Major | | | selenium-containing | | | plasma protein | | | | | | CLINICAL CONSIDERATIONS: | | | | | | 1. Acute Phase Response (APR) | | | Effects: | | | | | | - Decreased levels in: | | | | | | - Plasma selenoprotein | | | P | | | | | | - Plasma GSHPx-3 | | | | | | - Total plasma selenium | | | | | | - Critical for | | | interpretation in: | | | | | | - Post-surgical cases | | | | | | - Active infections | | | | | | - Inflammatory | | | conditions | | | | | | 2. Status Assessment: Short-term | | | Status: | | | | | | - Plasma selenium | | | | | | - GSHPx activity | | | | | | - Note: Must consider APR | | | influence | | | | | | Long-term Status Markers: | | | | | | - Platelet GSHPx | | | | | | - RBC GSHPx | | | | | | - Neutrophil GSHPx | | | | | | - Hair selenium | | | | | | - Nail selenium | | | | | | 3. Urinary Selenium: | | | | | | - Primarily reflects recent | | | dietary intake | | | | | | - Limited utility in | | | population studies | | | | | | - Not preferred for status | | | assessment | | | | | | KEY INTERPRETATIVE POINTS: | | | | | | - Multiple marker approach | | | recommended for comprehensive | | | assessment | | | | | | - APR status must be considered | | | for accurate interpretation | | | | | | - Short-term markers should be | | | interpreted alongside | | | clinical context | | | | | | - Long-term markers provide | | | more stable assessment of | | | selenium status | +-----------------------------------+-----------------------------------+ +-----------------------------------+-----------------------------------+ | ZINC | | +===================================+===================================+ | CHEMISTRY | Zn has fast ligand exchange | | | kinetics and fexible coordination | | | geometry, and it is a good | | | electron acceptor | +-----------------------------------+-----------------------------------+ | DIETARY SOURCES | Zn is widely distributed in food | | | mainly bound to proteins. The | | | bioavailability of dietary Zn is | | | dependent on the digestion of | | | these proteins to release Zn and | | | allow it to bind to peptides, | | | amino acids, phosphate, and other | | | ligands within the intestinal | | | tract | +-----------------------------------+-----------------------------------+ | ABSORPTION, TRANSPORT, METABOLISM | 1. Absorption Rate: | | AND EXCRETION | | | | - \~30% of dietary zinc | | | absorbed | | | | | | - Significant enterohepatic | | | circulation present | | | | | | 2. Absorption Mechanisms: | | | | | | - Dual pathway system: | | | | | | - Active transport | | | | | | - Passive diffusion | | | | | | - Metallothionein-mediated | | | regulation: | | | | | | - Enterocyte binding | | | | | | - Increased | | | metallothionein | | | synthesis when zinc | | | levels high | | | | | | - Acts as negative | | | feedback mechanism | | | limiting absorption | | | | | | BODY DISTRIBUTION: | | | | | | 1. Tissue Distribution: | | | | | | - Skeletal muscle: 60% | | | | | | - Bone: 30% | | | | | | - Skin: 4-6% | | | | | | 2. Blood Distribution: (Absorbed | | | Zn is transported to the | | | liver by the portal | | | circulation, where active | | | incorporation into | | | metalloenzymes and plasma | | | proteins, such as albumin and | | | a2-macroglobulin) | | | | | | - Erythrocytes: 80% of | | | circulating zinc | | | | | | - Plasma proteins: | | | | | | - α2-macroglobulin: | | | \~33% (firm binding) | | | | | | - Albumin: majority of | | | remaining (loose | | | binding) | | | | | | 3. Excretion: | | | | | | - Primary route: Faecal | | | elimination | | | | | | KEY CONCEPTS: | | | | | | - Homeostatic control primarily | | | at absorption level | | | | | | - Metallothionein serves as key | | | regulatory protein | | | | | | - Predominantly intracellular | | | distribution | | | | | | - Complex plasma protein | | | binding pattern | | | | | | - Enterohepatic recycling | | | significant for maintenance | +-----------------------------------+-----------------------------------+ | FUNCTIONS | 2\. Zinc primarily serves as a | | | cofactor for metalloenzymes. | | | | | | Important in remodeling of a | | | wound and replacing type III | | | collagen with type I collagen to | | | increase tensile strength | | | | | | Important in bone mineralization | | | | | | Marker of obstruction to bile | | | flow in the liver or common bile | | | duct | | | | | | Zinc is also important in | | | spermatogenesis and in growth in | | | children. | +-----------------------------------+-----------------------------------+ | DEFICIENCY | Requirements for zinc are | | | increased in premature infants, | | | during pregnancy and lactation | | | and following trauma. | | | | | | 1. Disease States: | | | | | | - Alcoholism | | | | | | - Rheumatoid arthritis | | | | | | - Inflammatory conditions: | | | | | | - Acute | | | | | | - Chronic | | | | | | - Chronic diarrhea | | | | | | 2. Genetic Disorder: | | | Acrodermatitis Enteropathica | | | | | | - Inheritance: Autosomal | | | recessive | | | | | | - Clinical manifestations: | | | | | | - Dermatitis | | | | | | - Diarrhea | | | | | | - Growth retardation | | | (pediatric) | | | | | | - Impaired | | | spermatogenesis | | | | | | - Poor wound healing | | | | | | CLINICAL MANIFESTATIONS: | | | | | | 1. Sensory Disturbances: | | | | | | - Dysgeusia (taste | | | impairment) | | | | | | - Anosmia (loss of smell) | | | | | | 2. Cutaneous: | | | | | | - Perioral rash | | | | | | - Poor wound healing | | | | | | 3. Endocrine/Developmental: | | | | | | - Hypogonadism | | | | | | - Growth retardation | | | | | | - Zn depletion is | | | associated with low | | | circulating | | | concentrations of | | | testosterone, free T4, | | | insulin-like growth | | | factor (IGF)-1, and | | | thymulin | | | | | | 4. Immune | | | | | | - Zn depletion impairs | | | immunity and has a direct | | | effect on GIT increases | | | severity of enteric | | | infections | | | | | | KEY CLINICAL CONSIDERATIONS: | | | | | | - Multiple organ system | | | involvement | | | | | | - Both acquired and genetic | | | causes | | | | | | - Significant impact on growth | | | and development | | | | | | - Affects both sensory and | | | reproductive function | | | | | | - Important consideration in | | | chronic disease states | +-----------------------------------+-----------------------------------+ | TOXCICITY | abdominal pain, diarrhea, nausea, | | | and vomiting | | | | | | Chronic ingestion of high zinc | | | intakes in otherwise healthy | | | people may lead to features of | | | copper deficiency (e.g. | | | microcytic anaemia, neutropenia). | | | This is because the induction of | | | metallothionein synthesis in | | | enterocytes by zinc results in | | | increased binding of copper to | | | metallothionein, which prevents | | | its transfer to the circulation. | | | Acute toxicity has been recorded | | | following ingestion of water with | | | a high zinc content, or the use | | | of such water in renal dialysis. | +-----------------------------------+-----------------------------------+ | LAB ASSESSMENT | 1. Plasma/Serum: | | | | | | - No confirmed preference | | | between plasma vs serum | | | | | | - Key Analytical Factors: | | | | | | - Multiple methods | | | available with | | | adequate sensitivity | | | | | | - Spectrophotometric | | | methods subject to | | | interference | | | | | | Critical Pre-analytical | | | Variables: | | | | | | - Meal timing | | | | | | - Diurnal variation | | | | | | - Steroid medications | | | (including oral | | | contraceptives) | | | | | | - Hypoalbuminemia | | | | | | - Acute Phase Response (APR): | | | | | | - Albumin redistribution | | | | | | - Metallothionein-induced | | | sequestration | | | | | | - Required concurrent | | | testing: Albumin and CRP | | | | | | 2. Cellular Components: | | | | | | - White Blood | | | Cells/Platelets: | | | | | | - Better tissue zinc | | | reflection | | | | | | - Faster depletion | | | response than plasma | | | | | | - Limitations: Large | | | sample volume, | | | contamination risk | | | | | | - Erythrocytes: | | | | | | - Limited utility | | | | | | - Poor correlation with | | | intake | | | | | | 3. Hair Analysis: | | | | | | - Associated with growth | | | assessment in children | | | | | | - Limitations: | | | | | | - Variable growth rates | | | | | | - External | | | contamination | | | | | | - Poor individual | | | result interpretation | | | | | | 4. Zinc-Dependent Enzymes: | | | | | | - No single validated | | | status marker | | | | | | - Potentially useful | | | enzymes: | | | | | | - Bone-specific | | | alkaline phosphatase | | | | | | - Extracellular SOD | | | | | | - Lymphocyte/plasma | | | 5-nucleotidase | | | | | | 5. Metallothionein: | | | | | | - Measurement options: | | | | | | - RBC metallothionein | | | | | | - Monocyte MT mRNA | | | | | | - Decreases in deficiency | | | | | | - Needs large-scale | | | validation | | | | | | 6. Urinary Zinc: | | | | | | - Limited diagnostic value | | | | | | - Clinical utility: | | | | | | - Monitoring severe | | | catabolic states | | | | | | - TPN with amino acid | | | administration | | | | | | - Limitations: | | | Contamination issues | | | | | | SPECIAL CONSIDERATIONS: | | | | | | - Hyperzincemia cases with | | | functional deficiency | | | (calprotectin dysregulation) | | | | | | - Kinetic studies show 5-week | | | lag for plasma depletion | | | | | | - Essential to interpret | | | results in clinical context | | | | | | - Multiple marker approach | | | recommended for accurate | | | assessment | +-----------------------------------+-----------------------------------+ | VANADIUM | | +-----------------------------------+-----------------------------------+ | CHEMISTRY | Vanadyl sulfate and ammonium | | | vanadate have been found to bind | | | serum transferrin tightly, | | | indicating that this protein may | | | serve as a vanadium transporter | +-----------------------------------+-----------------------------------+ | DIETARY SOURCES | | +-----------------------------------+-----------------------------------+ | ABSORPTION, TRANSPORT, METABOLISM | Food is the major source of | | AND EXCRETION | exposure to V for the general | | | population; however, absorption | | | of V salts from the | | | gastrointestinal tract is poor. | | | Excretion by the kidneys is | | | rapid, with a biological | | | half-life of 20 to 40 hours | +-----------------------------------+-----------------------------------+ | FUNCTIONS | plays a limited role in biology | | | | | | Clinical interest in the vanadate | | | compounds involves their | | | potential role in the treatment | | | of diabetes | | | | | | The insulin-like effects of V may | | | be initiated by inhibiting | | | phosphotyrosine phosphatases | | | (PTPases) and stimulating protein | | | tyrosine kinase activity, | | | implying that cells (adipose | | | cells in particular) contain | | | distinct vanadyl-sensitive and | | | vanadate sensitive PTPases. | +-----------------------------------+-----------------------------------+ | DEFICIENCY | / | +-----------------------------------+-----------------------------------+ | TOXCICITY | / | +-----------------------------------+-----------------------------------+ | LAB ASSESSMENT | Plasma and urine concentrations | | | are usually measured by graphite | | | furnace AAS or ICP-AES. Use of | | | ICP-MS | +-----------------------------------+-----------------------------------+