Lectures 10 and 11 - Iron Flashcards
what is the most important factor effecting bioavailability or iron
iron status
how does pregnancy affect iron absorption
increases
how does recent iron intake affect iron absorption
the mucosal iron block = large amount of iron will decrease absorption of iron you consume after this
what is the relative absorption of haem iron
~25-30%
what is the relative absorption of non heam iron
~5-15%
what are the enhancers of iron absorption
vitamin C and flesh meats (meat, fish, poultry factor)
what are inhibitors of iron absorption
phytate, tannins and oxalic acid
how is heme iron absorbed and what happens when it is in the enterocyte
heme iron is transported through heme transporter into enterocyte
heme oxygenase reacts with the heme and removes the iron ion from the heme molecule
how is non heme iron absorbed and what happens prior to this
non heme iron in the diet is in the Fe3+ form (ferric form)
duodenal cytochrome B reduces the non heme iron from the ferric form (Fe3+) to the ferris form (Fe2+)
the ferris form is the absorbed through the transport of DMT1
some iron will be stored as ……… and this will be lost by ….
some iron will be stored as ferratin in the mucosa, which will be lost by shedding of epithelial cells
what will transport iron out of the enterocyte
ferroportin
ferris form of iron is really reactive so you do not want this floating around in the body, what converts it to Fe3+ before it goes to the rest of the body
hephaestin
during high iron intake, what will diferric transferrin bind to in the liver and what will this cause the release of
TfR1 = will then release HFE
HFE released from TfR1 will bind to what and what will the stimulate
HFE binds to TfR2 stimulating hepcidin synthesis
what does hepcidin bind to and what does this cause
ferroportin on enterocytes and macrophages
- causes hepcidin-ferroportin complex to internalise and be degraded
meaning Fe trapped inside the enterocyte and cant be absorbed into the body
~67% body Fe is in the form of
haemoglobin
~4% of body Fe is in the form of
myoglobin
~0.2% of body Fe is for enzymes involved in ….
- energy metabolism
- neurotransmitter formation
- bacterial killing leukocytes
what are the two forms of storage Fe (which is the efficient way and what is not as effective)
- ferritin = most effective way of storage
- haemosiderin
how is iron excretion controlled in the body
there is no controlled excretion of iron from the body
what are the ways the body loses iron
epithelial cells
fluids
formation of erythrocytes requires how much iron
~30mg Fe/day
how does majority of iron reutilisation occur
majority from breakdown old red blood cells by macrophages in spleen and liver
what is the difference of iron deficiency anaemia and depletion of iron stores
iron deficiency anaemia affects the haemoglobin levels
symptoms of iron deficiency anaemia
- decreased growth
- behavioural disturbance
- decreased cognitive function
- fatigue
etc
- how are pre term infants at risk of iron deficiency
haven’t had enough time to accrue their iron stores
how are infants are risk of iron deficiency
high growth rate and pretty small appetite
what adults are at risk of iron deficiency
- menstruating women
- pregnant women
- blood donors
types of iron supplements to help iron deficiency
ferrous sulphate tablet or liquid
diet is affective in help non anaemia iron deficiency but not as effective as
supplements
what is acute iron toxicity
unintentional overdose iron tablets
what is hereditary haemochromatosis and what does this lead to
genetic condition = mutation to the HFE gene
poor control of iron absorption = iron accumulates in liver, pancreas, heart muscle …..
“african” iron overload was thought it was to do with intake of beer from cast iron drums but what was it really from
unidentified gene responsible
what is the RDI or adult men and women
RDI men : 8mg/day
RDI women : 18mg/day
