Trace elements
Definition • Inorganic micronutrients present at very low concentrations in body fluids and tissue. • Present at • (μg/dL) in body fluids • (mg/kg) in tissue • Amounts required • Micrograms per day • Dietary requirements • mg/day
Classification of Trace Mineral Elements
The biological function • Essential • The signs and symptoms induced by a deficient diet are uniquely reversed by an adequate supply of the particular trace element • Clinical examples • Iron-deficiency anemia • Goiter (iodine)
Trace elements • When insufficient, deficiency symptoms may arise, and if present in excess they may be toxic
Depending upon • The element in question, • The nature of the chemical species present in the diet.
Trace elements • In the form of metalloenzymes • Intermediary metabolism • Transport and safe storage • Examples • Metallothionein (Cu, Zn), transferrin, ferritin and hemosiderin (Fe),and ceruloplasmin (Cu). • Absorption, transport, uptake and storage, control of excretion.
Trace elements • Excretory route • Intestinal tract in bile and other intestinal fluids • By regulation of initial absorption and by resecretion • In feces • (Zn, Cu) • Urine • Halides • Other routes • Hair and/or nails, skin cell desquamation, and in sweat • Minor
Trace elements • Trace element deficiency disease • Poor dietary supply • Malabsorption • Antagonistic effects • Blockage of uptake by substances • Increased excretory losses • Disease, injury, and infection • Inborn errors • Defects in the metabolism of trace elements • Hemochromatosis • Wilson's disease and Menkes' syndrome)
Trace elements • Acrodermatitis enteropathica • Molybdenum cofactor disease
INTERACTIONS • Between different essential trace elements • With the other essential major minerals • Affecting the intestinal bioavailability • Synergistic and antagonistic • Example, • Zinc ions block copper absorption • Molybdate ion can form insoluble copper-molybdate • Between molybdenum and tungsten.
INTERACTIONS • Organic phosphate (phytic acid) in limiting zinc absorption • Synergistic interactions • Selenium and iodine • Selenoproteins • Deiodinases • Glutathione peroxidase • Zinc and vitamin A • Zinc depletion limits the bioavailability of vitamin A.
Deficiencies • Interference from other dietary ingestants • Lack of a protein needed to absorb or metabolize the element. • Total parenteral nutrition
The roles of the trace mineral elements • Structural, signal transduction • as enzyme co factors • Electron and oxygen transport • Maintenance of macromolecule conformation • Genetic defects in trace element metabolism • Menkes’ • Congenital atransferrinemia • Acrodermatitisenteropathica • Xanthine and sulfite oxidase
Trace element analysis • Atomic absorption spectrometry (AAS) • Assessment of trace element • Activity of a trace element-dependent enzyme • Concentration in accessible tissues
Laboratory assessment • Indirect determination • Metalloenzymes and protein species • Iodine • Assay of the thyroid hormones and of their control and feedback systems • Cobalt • Cobalamin (Immunoassay) • Direct methods • Analytical difficulties • Sample contamination
Laboratory assessment • Carrier proteins • Transferrin (Fe), albumin (Zn), ceruloplasmin (Cu), and selenoprotein P (Se) • Can give useful additional information. • Analytical consideration • Prolonged storage of samples • Storage at 4 °C to 10 °C with a rapid turnaround analytical time is good practice. • Repeated freezing and thawing • Precipitation of proteins and nonhomogeneous samples.
Preanalytical Factors • Effect of disease • Hepatic synthesis of some plasma proteins • acute phase proteins • Proteins increase • Metals increase • Inflammatory response • Increased permeability • Metal kinetics and distribution
Individual trace elements
Chromium • Function/enzyme component • Potentiates insulin action • Glucose and lipid metabolism • Cr(lll) low toxicity • Poorly absorbed • Component of glucose tolerance factor
Chromium • Effects of deficiency • No method to determine deficiency in humans • Impaired glucose tolerance in type 2 diabetes • Insulin resistance • Hyperglycemia • Peripheral neuropathy • Hyperlipidemia
Chromium • Effects of toxicity • Cr(VI)toxic, oxidative damage, skin ulcers, • Contact dermatitis, asthma, renal and hepatic necrosis, lung cancer
Cobalt • Function • Hemoglobin synthesis • Component of vitamin B12 • Effects of deficiency • Cobalt deficiency, as such, not in humans • Symptoms due to lack of vitamin B12 • Anemia , anorexia, growth depression
Cobalt • Effects of toxicity • Cardiomyopathy, heart failure, goiter, • hypothyroidism; warm sensation, vomiting, diarrhea
Copper • Function • Cellular respiration, neurotransmitter regulator, • Oxidation reaction, electron transport, collagen • Synthesis, development of vascular and skeletal Structures and CNS • Antioxidant Component of CuZnSOD, metallothionein, • Cytochrome c, tyrosinase, dopamine β-hydroxylase, Iysyl oxidase
Effects of deficiency • Menkes' kinky hair syndrome: X-linked; congenital failure of Cu absorption • Abnormal collagen crosslinking, muscle weakness, iron-refractory hypochromic anemia, leukopenia, neurological defects, hypopigmentation • In prematurity: bone fractures, skeletal defects • Occurs in malnourished children and premature infants not supplemented
Effects of toxicity • Relatively nontoxic • Wilson's disease: autosomal recessive; failure to excrete Cu in bile • Excess Cu in liver, kidneys, brain, eyes; hepatic necrosis, hypertension,Kayser-Fleischer rings in eyes • Cu interferes with absorption of iron and zinc
Fluorine • Function • Prevents tooth decay • Effects of deficiency • Increased dental caries • Effects of toxicity • Mottled enamel, fluorosis
Iodine • Function • Component of thyroid hormone • Effects of deficiency • Goiter, hypothyroidism, cretinism in infants, myxedema in adults • Effects of toxicity • Goiter, thyrotoxicosis
Iron • Function/enzyme component • Oxygen transport, respiration, amino acids and • free radical metabolism, lipids, oxidative • Phosphorylation, Component of hemoglobin, metalloenzymes, vitamin A
Effects of deficiency • Hypochromic microcytic anemia, • glossitis, angular stomatitis, cheilosis, • Blood loss or inadequate iron intake; • iron deficiency anemia: < 7 g/100 mL blood
Effects of toxicity • Hemochromatosis: genetic, primary, autosomal recessive acquired, secondary, iron overload iron deposition in liver, pancreas, heart and skin
Manganese • Function/enzyme component • Bone and connective tissue • Component of metalloenzymes: hydrolases, • Oxidoreductases, and lipases, pyruvate caboxylase • Superoxide dismutase, and arginase
Effects of deficiency • Not well-defined in humans • Skeletal and cartilage defects • Effects of toxicity • Least toxic of trace elements • Psychiatric disorders: memory, speech, • hallucinations; syndrome resembles Parkinson's • and WiIson's diseases
Molybdenum • Function • DNA metabolism, essential for uric acid Production • Component of sulfite and xanthine oxidase • Effects of deficiency • Naturally occurring deficiency not known; • Growth depression, hypercuprinemia, defective keratin formation, goiter, cretinism
Effects of toxicity • Anemia, goiter, thyrotoxicosis • Hypouricemia,hyperoxypurinemia
Selenium • Function • Protects against oxidative damage of lipid, • gene expression, thyroxin deiodinase • Component of glutathione peroxidase
Effects of deficiency • Cardiomegaly, heart failure, cataracts, • Osteoarthritis in children, myopathy, • discolored/thickened nails, impaired growth
Effects of toxicity • Hair and nail loss, selenosis, tooth decay, • neuropathy, liver failure, garlic odor on breath
Zinc • Function • Protein synthesis, zinc finger proteins - gene • expression, immunity, needed for normal skin, • bones and hair Component of metallothionein, - 300 enzymes
Effects of deficiency • Acrodermatitis enteropathica; causes • Cardiomyopathy in children • In children, low height, hypogeusia, • growth retardation, infertility, immune • deficits, delayed wound healing, glossitis, seborrheic-like dermatitis, osteoporosis
Effects of toxicity • Relatively nontoxic, nausea, vomiting • GI-irritation, causes copper deficiency
Properties of Essential Trace Mineral Elements
