Micronutrients Flashcards
1
Q
Micronutrients and trace elements
A
- Vitamins, antioxidants and trace elements
- Includes zinc, iron, copper, selenium
- Important in metabolism and maintenance of tissue function - adequate intake necessary
2
Q
Iron as a micronutrient post surgery
A
- transferrin is its carrier protein
- transferrin:iron ration falls
- remains low for several weeks after surgery
3
Q
Zinc as a micronutrient post surgery
A
- albumin is its carrier protein
- albumin:zinc ration falls
- maintained decrease in albumin concentration after surgery, lasts
- zinc being actively removed from albumin
- Increase to support protein synthesis after surgery, likely to support acute phase proteins
- Zinc increased due to induction of methalothionen (metal binding protein) in liver
- Increased uptake of zinc into the liver to bind methallothionein
4
Q
Copper as a micronutrient post surgery
A
- ceruloplasmin is its carrier protein
- ceruloplasmin:copper remains constant showing that rise inc copper is due to an increase in serum ceruloplasmin, an acute phase protein synthesised in the liver
5
Q
Effects of excessive iron
A
- Increases oxidative damage as a result of the production of mention and the haber-weiss reaction
- Stimulates bacterial infection due to iron being key nutrient for bacterial growth
- More beneficial to have lower circulating iron
6
Q
Control or iron concentration
A
- Iron levels are controlled by lowering of transferrin
- Increase of ferritin - the iron stage protein
- Increase in hepcidin - increased hepcidin blocks the action of iron transporter so iron is neither absorbed from the gut nor released by macrophages
7
Q
Case of selenium deficiency and availability of trace elements
A
- Presence of trace elements in foods is often determined by the availability of metals in the soil. Thus, within a geographical region with soil deprived of trace elements, its population is at risk and trace element supplementation becomes necessary
- Selenium is a metalloid, a trace element
- Selenium needed for glutathione peroxidase, with selenocysteine as its active site
- In Finland, the soil was deficient of selenium and required fertilisation.
- In China, the incidence of Keshan disease (Keshan a region in China), a lethal cardiomyopathy partly caused by selenium deficiency. Reduction of incidence through selenium addition to salt
- Another factor is coxsackievirus B3,CUB3
- Example of disease with dual aetiology
8
Q
Vitamins and Organic micronutrients
Source - Coenzyme - Major metabolic roles
A
- Niacin -> NAD+ & NADP+ -> Redox reactions including II electron transfer
- Riboflavin (B2) -> Flavin mononucleotide (FMN) & Flavin adenine dinucleotide (FAD) -> Redox reaction including I and II electron transfer
- Pantothenic Acid (B3)-> Coenzyme A-> Transfer of Acyl group
- Thiamine (B1)-> Thiamin Pyrophosphate (TPP)-> Transfer of aldehyde groups
- Pyrodoxine (B6)-> Pyridoxal Phosphate (PLP)-> Trasnfer of groups to and from amino acids
- Biotin-> Biocytin-> ATP dependant carboxylation of substrates or carboxyl group transfer between substrates
- Folic Acid-> Tetrahyrdofolate (THF)-> One carbon transfer
- Cobalamine(B12)-> Adenosylcobalamine +Methylcobalamine-> Transfer of methyl groups
- Ascorbate (C)-> No co-enzyme-> Reduction of vitamin E, antioxidant role, collagen synthesis
- Vitamin A-> cis-retinal-> vision
- Vitamin D-> No co-enzyme-> Regulation of Ca2+ utilisation
- a-Tocopherol (E)-> No co-enzyme-> Lipid soluble antioxidant
- Vitamin K-> Vitamin K-> Carboxylation of some glutamate residues
9
Q
Trans-suphuration pathway and Homocystnuria
A
- Major route for metabolism of sulphur containing amino acids
- Vitamin B12 deficiency
- Common disease affecting this pathway is Homocystnuria
- Homocytnuria is an inherited disease in which sufferers exhibit a disorder of metabolism of amino acid methionine due to cystathione beta synthase deficiency
10
Q
Impact of smoking on micronutrients
A
- Low conc of vitamin C and beta carotene are associated with smoking
- Catabolism of vitamin c in smokers is greater, lower steady state conc of plasma ascorbate
- Lower conc possibly due to high oxidative stress from substances in smoke that stimulate inflammatory response
- Inverse correlation between plasma conc of Dehydroascorbic acid (partially stable oxidised version of vitamin c) and total ascorbic acid in smokers but not non smokers suggesting increased turnover of vitamin C in response to the high and sustained oxidant load from smoking
11
Q
Beta Carotene and smoking
A
-Supplements have not shown any benefit in prevention of major diseases
-Supplements coupled with smoking may cause adverse effects on smoking
At present no specific recommendations are proposed for supplements of B carotene or other carotenoids
12
Q
Alpha tocopherol and smoking
A
- No consistent difference in conc of smokers and non smokers therefor dietary supplements are sufficient
- Smoking supposedly has no effect on appetite of foods containing vitamin E
13
Q
Selenium and smoking
A
- Serum selenium concentrations and erythrocyte Glutathione peroxidase activities tend to be lower in smokers
- there is some evidence to suggest that lower serum selenium concentrations are associated with inflammation
14
Q
Measures of copper in blood plasma
A
- Two main measures of copper in smokers are erythrocyte CuZn- SOD activity and serum ceruloplasmin concentrations
- Stduies have shown that CuZn-SOD activity was consistently higher in smokers than non smokers - the increase may have been part of the anti-inflammatory response to smoking
- In vivo it has been shown to act as an acute phase protein with anti-oxidant and anti-inflammatory properties
15
Q
Iron and smoking
A
- Smoking appears to affect iron homeostasis, mainly by causing changes in blood haemoglobin concentration
- Serum ion, transferrin and ferritin concentrations appear to not be affected by smoking during pregnancy
