1 How does iron status regulate iron absorption Iron balance is controlled at point of absorption Absorption adapts to a person s needs Mucosal cells in the intestine store excess iron in mucosal ferritin a storage protein If the body needs iron mucosal ferritin releases iron to mucosal transferrin a transport protein which hands off iron to another transferrin that travels through the blood to the rest of the body If the body does not need iron Hepcidin a hormone released from the liver tells the digestive system to reduce the absorption of iron Thus iron is not absorbed and is excreted in shed intestinal cells instead Iron absorption is therefore reduced when the body does not need iron Hepcidin maintains iron levels in the body Hepcidin prevents hemochromatosis excess iron in the body 2 How does heme iron absorption compare to non heme iron absorption For the non heme iron what form is better absorbed Heme iron from hemoglobin is better absorbed 23 than non heme iron from plant foods and animal foods Non heme iron must be reduced from Fe 3 ferric to Fe 2 vitamin C needed and ferrireductase Non heme iron once reduced to Fe 2 goes through DMT 1 Heme iron goes through the heme transporter HCP1 Non heme iron is hard for our body to transport Fe 3 non heme iron is soluble in acid insoluble in alkaline solution less absorbed 3 Identify the enhancers and inhibitors of iron absorption Non heme iron absorption enhancing factors o Meat fish poultry MFP factor o Ascorbic acid vitamin C sugars acids Reduces non heme iron from Fe 3 to Fe 2 Fe 2 can be absorbed better o Ferrireductase at brush border o Low iron status Non heme iron absorption inhibitors o Phytates and fibers o Calcium and phosphorous at high intakes o EDTA in food additives o Tannic acid o Polyphenols tea coffee o Oxalates spinach o Phosvitin o Divalent cations o Excess alkalinization o Malabsorption syndromes o Rapid transit time 4 How do Zn and Fe influence each other s absorption High Zinc causes low copper and iron absorption because o Copper binds to metallothionein trapped o Zinc binds with transferrin decreases iron absorption High iron intake causes low zinc absorption 5 What s the function of metallothionein in zinc homeostasis Metallothionein is a zinc storage protein for iron it is mucosal ferritin It is a zinc binding protein Regulates Zinc absorption Releases zinc into the blood when needed 6 What protein transfers iron in the blood What form of iron does it bind to How is iron transported in the way taken up by cells Mucosal transferrin transfers iron to blood transferrin Blood transferrin carries iron in the blood to the rest of the body Fe 3 is the form of iron on transferrin Iron is taken up by the cells when it is bound to transferrin holoenzyme 7 What protein stores iron inside of the cells Ferritin Homosiderin Storage in the bone marrow spleen and liver 8 How does iron status regulate the amount of the two proteins above By what mechanisms Note This regulation is a good example of a nutrient regulating gene expression at the mRNA level as opposed to at the transcriptional level like vitamin D and A do If you have low iron o Iron response element binding protein 3 Fe binds to IRE on ferritin mRNA and inhibits translation of ferritin o IRE BP 3 Fe binds to transferrin receptor mRNA and increases the stability of the mRNA If you have iron o IRE BP binds an additional Fe ion IRE BP9 4 Fe translocates into the mitochondria to function as aconitase in the TCA cycle AN o INTERACTION WITH mRNA WILL NOT OCCUR WHEN IRON IS HIGH ADDITIONAL QUESTION What organs store iron in the body In red blood cells as heme in hemoglobin Storage iron mainly in the bone marrow spleen and liver Myoglobin 9 What are the commonly used methods to determine iron status Iron deficiency can be assessed by measuring various biochemical indices o Measure serum ferritin and transferrin Ferritin is reduced storage and transferrin is increased o Measure transferrin saturation o Measure erythrocyte polyporphyrin A precursor to hemoglobin that accumulates in plasma o Measure hemoglobin and hematocrit volume of RBC values 10 Generally what are the functions of iron in the body What are the functions of zinc in the body Iron Functions o Oxidation reduction reactions of energy metabolism Cofactor to enzymes Part of the electron carriers in the ETC o Structural functional component of Hemoglobin blood and myoglobin muscle Most of the body s iron is found here Carries oxygen Accept carry and release oxidation o Cofactor in enzymes that control brain function tissue formation immune function hormone production Zinc functions o Catalytic role in enzymes Zinc metalloenzymes Aid in synthesis of DNA and RNA Manufacture heme for hemoglobin Participate in essential fatty acid metabolism Release vitamin A from liver stores Metabolize alcohol in the liver Dispose damaging free radicals ANTIOXIDANT Zinc is needed for action of several hormones insulin and thyroid gland Zinc is essential for cell division Zinc affects blood clotting Zinc is required for normal taste perception Zinc is required for normal sperm development and fetal development ADDITIONAL QUESTION What are metalloenzymes Metalloenzymes are enzymes that contain one or more minerals as part of This is an enzyme containing tightly bound metal atoms e g the their structure cytochromes 11 What are the major causes of iron deficiency Iron is the most common mineral deficiency in the world Results from depleted tissue stores Occurs when iron absorption cannot keep pace over an extended period of time with the rate of iron loss Initially ferritin levels decrease transferrin increases to help facilitate absorption Increase in drug abuse increase in iron deficiency Primary causes low intake of bioavailable iron increase iron requirements rapid growth pregnancy menstruation excess blood loss pathologic infestations unsanitary conditions 12 List a few main symptoms of iron deficiency o Reduced iron stores compromise energy metabolism o Tired tissues o Impairment of neurotransmitter synthesis o Reduction in physical and mental work Iron deficiency with anemia o Severe depletion of Fe stores o Low hemoglobin concentrations o Microcytic hypochromic no color anemia Symtpoms o Impaired cognitive function o Impaired immune function o Reduced work capacity o Fatigue weakness headaches apathy o Inability to regulate temperature o PICA a craving for nonfood substances o Depression Anxiety 13 Is the iron RDA the
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