Iron absorption Flashcards
HFE
mutation responsible for most common absorption problems hemochromatosis
chromosome 6
protein HFE
HJV
mutation responsible for jeuvanile absorption problems
protein Hemojeuvelin
chromosome 1
TFR2
mutation responsible for clinically similar features to HFE but rare
chromosome 7
protein Transferrin receptor 2
SLC40A1
chromosome 2
protein ferroportin
HAMP
hepcidin, an iron regulation hormone critical for absorption
chromosome 19
factors that INCREASE iron absorption
inadequate diet impaired absorption celiac disease GI bleeding hypoxia anemias decreased erythropoiesis
factors decreasing iron absorption
regular blood transfusions
high iron diet
iron loading vitamins
human hemochromatosis protein
HFE
functions to regulate circulating iron uptake by regulating the interaction of the TFR 1/2 with transferrin
Hepcidin
key regulator of the entry of iron into circulation
transferrin
iron binding blood plasma glycoprotein that controls the level of free iron in biological fluids
TFR1
a protein required for iron imort from transferrin into cells by endocytosis
TFR2
protein involved in uptake of transferrin bound iron into cells by endocytosis, although role is minor compared to TFR1
Ferroportin
transmembrane protein that transports iron from the inside of the cell to the outside of the cell. inhabited by hepcidin, results in the retention of iron
Low iron and Hepcidin
low iron decreases hepcidin, which causes ferroportin to ne expressed in order to allow iron to be absorbed by the duodenum
High iron and hepcidin
high iron causes hepcidin to be high, which causes ferroportin to be prevented from bringing more iron in from the duodenum and gut
hepcidin expression is regulated by
HFE, HJV, TRF2
mutation ins HFE, HJV and TRF2 effect
hepcidin expression, which regulates iron absorption
Transferrin binds two molecules
TRF and HFE
Transferrin and HFE compete for the TRF1 receptor, although transferrin has a higher affinity. Unbound HFE is raised to the surface of the cell which stimulates hepcidin expression
high iron levels and TRF2
high iron causes TRF2 to be expressed, binding more transferrin than TRf1
TRF2 upregulates more hepcidin expression downregulates transport of Fe out of the enterocytes
Too much iron causes more ____ to be produced than _____. Transferrins then bind more ______ than _____ because more is expressed. TRF2 binding stimulates ____ expression
TRF2 than TRF1
transferrins bind more TRF2 than TRF1
stimulates hepcidin production
hepcidin downregulates ferroportin which decreases Fe secretion out of enterocytes