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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
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)
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– Acrodermatitis enteropathica– 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
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
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
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