Iron Flashcards
Cytochrome P450
An an iron enzyme used in first line of defense against toxins
Oxidizes: Caffeine, acetaminophen, nicotine, diazepam. aniline and benzene
When is iron most needed?
Periods of growth, blood loss (mensuration),
How much Iron is lost a day & from where
1-2mg – GIT, skin, Epithelial lining
How is iron involved in DNA transcription
Ribonucleotide reductase (converts ribonucleotides to deoxyribonucleotides) uses oxygen-bridged iron for stability.
Therefore:
Too little iron = Can’t properly syn DNA
Too much = Free radicals affect DNA
RDA for Adult Men and Women and Pregnant women
Men Always 8
Women: 18
Pregnant women: 27
RDA for Veg and Oral Contraceptive women (why?)
Veg = 1.8x higher (~32) B/c non-heme iron isn’t as bioavail
Oral Contraceptives = 10.9mg B/c there is less blood loss
Why is the AI for infants iron consumption so low?
0.27g ,It’s based off of healthy breastfed infants, which have high needs but really high bioavailability through source Lacto-ferrin
What sources of Food would provide enough iron within one serving?
Peanut butter, Claims, Beef liver (For all)
Claims only for Women 19-50
What form of iron is in dairy products?
low iron, non-heme
Heme Iron absorption
Little regulation, Through hcp 1, hydrolyzed to inorganic ferrous Fe and protoporphyrin, Also hydrolyzed in stomach and Small I (25% absorbed)
Non-heme absorption
Hydrolyzed from food components in the stomach, Fe2+ taken up by DMT1, Fe3+ can reduced into Fe2+ on BBM or turned into Fe(OH) which is insoluble = feces
17% absorbed
Why does increasing acidity improve iron absorption?
Supplies more ways to reduce Fe3+ which would improve absorption
What is iron balance determined by?
Iron absorption.
Increased Iron absorption is a result of duodenal expression of
DCYTB - increase reduction of ferric to ferrous
DMT1 - increase transport into cell
Ferroportin - increase transport of ferrous iron out
All cell iron transporters for uptake and output
When would there be an increased need for iron
pregnancy, erythropoiesis, hypoxia, iron deficiency
Hepcidin
Binds ferroportin for degradation when body stores are high
- depletes expression of brush boarder transporters
Hephaestin
Secreted by liver, oxidizes Ferrous to Ferric before apotransferrin transport
Factors that increase iron absorption
Meat Factor protein (MFP - AA or other food used to increase non-heme
Vit C
Acids/Sugars - Ascorbic, citric, lactic, gastric
Use iron cookware
Factors that decrease absorption
Phytates, polyphenols, soy
Acids: Oxalates (spinach, beets, rhubarb), Tannic
Minerals
EDTA
Vegan diet (10% absorbed)
Intraluminal factors (rapid transit time, malabsorption, gastric juice)
Which salts absorb better in the diet Ferrous or ferric
(& examples)
Ferrous salts absorb better -
Ferrous salts: Lactate, fumarate, gluconate, citrate
Ferric salts: Sulfate, citrate
Why is Calcium a concerning mineral for iron absop
shown to decrease activity of ferroportin
Purpose of Chelators - examples?
Small molecules that bind metal ions
Main purpose: to bind and make iron unavailable
Increase (weak chelators protect iron from strong chelators): ascorbates + citrates
Decease (strong chelators): Tannins, phytates
Endogenous chelator
Mucin = binds and improves absorption
Desferrioxamine, deferasirox
Iron chelators that bind iron specifically. Used for iron excess therapy to protect the cell from toxicity
Where is majority of Iron in the body + Rest
Functional iron ~78% Hb, Mb, Heme/N enzymes (Hemoglobin (2/3) –
Storage: 22% (Ferritin + hemosiderin)
Transport 0.001% - transferrin
How is the need for iron 20mg a day but only ~15mg is required in the diet?
Turnover of Hb, ferritin, and hemosiderin accounts for 18mg/day
Though Diet calls for ~15mg/day only 1-2mg is actually absorbed
TfR 1 vs TfR2
Receptors
1 = protein for transferring iron uptake, subject to regulation
2 = involved in regulation of hepcidin transcription / sensor of iron levels, not regulated
Transferrin Saturation: Levels
30% saturated usually
<30 depleted iron stores
<15 iron deficient erythropoiesis
>60 dangerrr
The difference between STEAP and DcytB
Both on apical side to reduce Fe3 to Fe2 before transport.
STEAP is endosomes
B is duodenal enterocytes
What 3 nutrients are needed for Erythropoiesis, what stims?
Iron, folic acid, B12
Stim: Erythropoietin
How does the body recycle RBC
RBC are recycled by mononuclear phagocytic system -
Lysed in lysosomes of macrophages - heme is broken down and iron exported into cytosol - exported from macrophages via ferroportin into plasma and reduced by ceruloplasmin - loaded onto transferrin
How does the body respond to excess iron?
apotransferring and ceruloplasmin ensure that iron is immediately chelated to limit toxicity and free radicals
Would transferrin increase during iron deficiency?
it may increase but not a good indicator because it’s more likely to show responses to diet
sTfR
Expressed on cells in need of iron
- High mean iron is needed
- Can be overexpressed from inflammation, will decrease when RBC not needed
IRE - Iron response elements
Active - when low iron, binds to restrict ferritin and increase TfR syn
Inactive - when iron is abundant, ferritin syn proceeds
What are normal and deficient levels for Hb for M and F
Normal - M = 135-175. F= 120-160
Deficient - M = Less than 125. F = less than 110
Hemosiderin
Storage of iron within lysosomes
