Lecture 28 - Iron metabolism

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Lecture 28
Lesley Howard
Karteikarten von Lesley Howard, aktualisiert more than 1 year ago
Lesley Howard
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Heme iron Usually found in meat Most bioavailable kind Heme shields iron from dietary chelators 5-35% absorbed
Non heme iron Found in fruits, veggies, eggs Mostly Fe3
Fe3 Ferric iron Abundant but low bioavailability
Fe2 Ferrous iron More soluble Less available Used in iron supplements
Fe Elemental iron Insoluble at physiologic pH Used to fortify foods
Iron enhancers Reducing molecules Amino acids Acidic foods
Iron inhibitors Phytates Polyphenols Phosphates and phosphoproteins Oxalate Zn and Ca
Reducing molecules Things like vitamin C that reduce Fe3 to Fe2 and form soluble complexes
Amino acids Form soluble complexes with Fe2 Found in meat and fish
Acidic foods Increased solubility of Fe and Fe3
Phytates Form insoluble complexes with Fe2 Cereal grains and legumes
Polyphenols Form insoluble complexes with Fe2 Tannins in tea and coffee
Phosphates and phosphoproteins Form insoluble complexes with Fe2 and Fe3 Egg yolk
Oxalate Forms insoluble complexes with Fe2 and Fe3 Spinach
Zn + Ca Compete with Fe Supplements
Fenton reaction Unbound ferrous iron (Fe2) is toxic Non enzymatically catalyzes the formation of hydroxide radicals Fe2 + H2O2 = Fe3 + OH + OHdot
Transferrin Binds ferric iron and solubilizes it Attenuates reactivity Delivers it to sites of use and storage
Transferrin receptor Binds to the iron-transferrin complex Mediates endocytosis and the formation of an endosome Releases the iron-transferrin complex and is recycled to the cell surface
Ferritin Intracellular iron storage protein 24 H or L subunits Homopolymers only found in pathologies Iron stored in ferritin cannot catalyze the Fenton reaction
Hemosiderin A form of ferritin in lysosomes Stores insoluble iron Found in conditions of iron overload
Iron loss in toddlers Nutritional deficiency
Iron loss in adults Bleeding other than menstruation
I Menstruation
Iron loss in pregnant women Increased need
Serum transferrin test Presented as total iron binding capacity (TIBC) Reflects total levels of transferrin
Serum ferritin test Accurately reflects intracellular ferritin levels Inversely proportional to TF and TFR levels Low iron = low ferritin = high TF and TFR High iron = high ferritin = low TF and TFR Best test for iron deficiency anemia
Iron deficiency anemia Caused by acute or chronic blood loss koilonychias, anisocytosis, poikilocytosis, target cells HGB < 10g /dL RBCs can be microcytic and hypochromic
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