True or false: Iron is excreted following heme degradation.
False, Fe is conserved
What 3 things may be underproduced to cause microcytic anemia?
Heme (prosthetic group), Iron, or Globin (protein)
True or false: Iron is very soluble.
False
True or false: free iron is toxic
True
What form of Fe is in the heme atom?
Fe++ (methemoglobin is Fe+++)
What are bacterial Siderophores?
Siderophores are produced by bacteria to bind iron and bring it into the cell. Increased iron may lead to bacteremia.
What are the 5 ways that iron is circulated/stored in the body?
Erythroid marrow, Circulating erythrocytes (hemoglobin), reticulo-endothelial cells (ferritin), Liver (ferritin), Gut (food iron - heme and non-heme Fe)
True or false: the Oxygen dissociation curve is steepest at the O2 concentraitons that occur in the tissues, allowing for O2 delivery to respond to small changes in pO2.
True
What is Transferrin? How many Fe binding sites does it have?
A molecule that binds Fe+++ for transport, found in the liver. It has two high-affinity Fe binding sites.
What is ferritin?
A large protein for Fe storage. It contains of precipitate of Fe in the middle to keep it soluble.
What is Hemosiderin?
An Fe storage complex found in cells (as opposed to in circulating blood) containing partially degraded ferritin and lysosomal proteins.
What do serum Fe/Transferritin tests tell us?
Measure of Fe delivery to marrow
What does testing serum ferritin levels tell us?
It tells us the measure of body Fe stores because serum ferritin is proportional to this.
What does Hemoglobin testing tell us?
Gives overall measure of functional Fe metabolism (how much Hb is in RBCs)
What does the transferritin saturation test tell us?
The proportion of transferritin bound to ferritin.
For Fe nutrition, which type of Fe is more soluble, Heme bound or non-heme bound?
Heme bound iron is more soluble
What luminal (2) and mucosal factors (1) increase iron solubility?
Luminal: reducing agents (HCL, ascorbic acid) and chelating agents (organic acids and amino acids). Mucosal: Iron deficiency.
What luminal (1) and mucosal (1) factors decrease iron solubility?
Luminal: intraluminal binders (ie. phosphate, phyates and dietary fibre), Mucosal: proximal small bowel disease
What is Hepcidin and what is its role in iron absorption?
Hepcidin is a protein produced by the liver that inhibits iron transport by binding to the iron export channel ferroportin, which is located on the basolateral surface of gut enterocytes.
How is iron absorption controlled at the level of villi cells?
While forming in the crypt, the gene expression for different iron transporters on villi cells can be altered to increase or decrease iron absorption depending on need.
Give examples of anemias not caused by iron deficiency.
What are two possible causes of sideroblastic anemia?
Genetic: delta-ALA synthase deficiency;
Environmental: alcoholics with a lack of vitamin B6
Why is too much iron toxic?
It causes free radical production in mitochondria.
What is hematochromatosis, how is it inherited, and who is at greatest risk?
It is an increase in iron absorption. It is inherited in an autosomal recessive fashion, and males are more at risk. This is because females menstruate, so extra iron often isn't an issue.
