Minerals Flashcards
What are forms of Coppers and how are they absorbed?
Cu+ or Cu2+ , mainly Cu2+.
90% in plasma bound to caeruloplasmin
Absorption ↓ by Zn, which induces metallothionein, which binds Cu in intestine
What are functions of Copper?
- Cytochrome oxidase: mitochondrial electron transport chain)
- Superoxide dismutase: free radical scavenger, prevents against oxidative damage
- Dopamine hydroxylase: catecholamine synthesis
- Monoamine oxidase: catecholamine breakdown)
- Tyrosinase: melanin synthesis
What causes Copper Deficiency?
Caused by:
- Loss from body in bile
- Chronic malabsorption resulting in diarrhoea;
- With jejunostomies
- Rarely genetic disorders of copper transport (Menke’s disease: ATP7A gene)
What are Symptoms of Copper Deficiency?
- Anaemia
- Neutropenia
- Bone changes similar to osteoporosis
- Hair changes,
- Neurological (neuropathy, myelopathy)
What causes excess in Copper and their signs/symptoms?
Caused by Contaminated drinking water (copper pipes) and Wilson’s disease (ATP7B gene)
Symptoms/Signs:
- Kaiseer Fleischer rings
- Cirrhosis
- Parkisonian disease
What are features of Zinc?
- Highly bound in serum to α2 macroglobulin and albumin
- Zinc is required for the activity of many enzymes, including those in DNA and protein synthesis.
- Zinc is beneficial for wound healing in zinc-deficient subjects
- Body does not store Zn to any appreciable extent in any organ therefore need regular dietary supply
- Primary route of elimination is biliary; normally only small amounts is excreted in urine
What are causes of Zinc Deficiency?
- Catabolic states (after trauma, surgery, burns) lose Zn in their urine
- Chronic malabsorption syndromes
- Pregnancy
- Lactation
- Old Age
- Alcoholism
- Diuretics
- Chelating agents (eg. penicillamine for Wilson’s),
- Cancer
- Chemotherapy
- Acrodermatitis enteropathica (inherited defect in intestinal Zn absorption)
What are Symptoms of Zinc deficiency?
- Dermatitis
- Delayed wound healing
- Alopecia
- Diarrhoea
- Weight loss
What are features of Selenium?
- Constituent of Selenoproteins: Glutathione peroxidase (protects against oxidative damage) and Deiodinases (T4ÞT3)
- Selenium bioavailability higher in plant foods (absorbable forms Se-methionine, Se-cysteine) than animal foods
- Inorganic forms (selenite, selenate) in drinking water - less absorbable
What causes Selenium deficiency and what are their signs/symptoms?
- May be caused by malabsorption e.g. Crohn‘s and specialist diets e.g. for PKU.
Symptoms
- Leads to muscle weakness, cardiomyopathy
- In Keshan in China: low Se in soil associated with deficiency and susceptibility to cardiomyopathy
What are features of Iodine?
- Forms part of thyroid hormones: Thyroxine (T4) and Triiodothyronine (T3)
- Deficiency is an Important worldwide health problem resulting in mental retardation
- Number of mechanisms prevent toxicity, but persistently high intakes can cause hyperthyroidism
Who are tested for Vitamin and Trace element analysis?
- Patients on nutritional supplementation
- Patients who are malnourished
- Patients where there is clinical suspicion of overdose or deficiency
- Malabsorption syndromes e.g. Crohn’s disease
- Fat malabsorption syndromes e.g. pancreatitis, Zollinger-Ellison
- Congenital disorders e.g. Abetalipoproteinaemia
- Patients with increased loss e.g. haemodialysis
What is the causes of Acute Phase?
- Metabolic changes occur in the body in response to infection, trauma, tissue damage.
- Can result in changes in micronutrients which are unrelated to nutritional status
Caused by:
Redistribution of binding proteins
Increased uptake by tissues
What happens to Vitamin and Trace element analysis in Acute Phase Response?
- CRP >10mg/L – Plasma Copper, Selenium and Vitamin C are unreliable
- CRP >20 mg/L – Plasma Zinc, Vitamin A and Vitamin D are unreliable
How can Vitamins and Trace Elements be measured indirectly?
- Haemoglobin used as a surrogate of Iron status
- Iodine infrequently measured but thyroid hormone status often checked
- Cobalt may be measured as an indicator of vitamin B12 status
- Homocysteine can indicate vitamin B12/folate status. Homocysteine may be elevated when folate/B12 is deficient
- Methylmalonic acid (MMA) can indicate vitamin B12 status. Increased MMA may indicate B12 deficiency
- Prothrombin time (INR) indicates vitamin K status
What has to be done with sample taken for Vitamin and Trace element analysis?
Mainly serum/plasma samples which may have specific collection requirements
- Vitamins A, E, B2 and B6 are light sensitive
- Vitamin C is extremely unstable
Ideally fasting sample. If this is not possible, sample should be taken at least 8 hours post treatment for patients receiving parenteral nutrition
What are methods and features of Trace Element Analysis?
- Matrix: mainly Serum/Plasma
- Method of analysis: mainly HPLC or immunoassay
- Frequency of measurement: repeat 2-4 weeks after initial supplementation, but many vitamins do not require repeat testing for several months
- Not a role for routine measurement of some vitamins e.g. vitamin C
What are methods and features of Trace Element Analysis?
- Generally measured by ICP-MS
- Careful collection of samples is required
- Other analytes may be useful, e.g. caeruloplasmin is measured in conjunction with copper in the investigation of Wilson’s disease. Gives an indication of free copper available
What is the sequence for Inductively Coupled Plasma Mass Spectrometry?
- Ionisation source that fully decomposes a sample into its constituent elements
- Elements transformed into ions
- Usually made from argon gas
- Energy is coupled to it using an induction coil to form the plasma
- Ions are produced, sampled, filtered by mass and detected
What are features of Inductively Coupled Plasma Mass Spectrometry?
Highly sensitive analysis
Simultaneous analysis of metals at trace concentrations (pmol/L)
- Copper, Selenium, Zinc
- Toxic metals e.g. Lead
