HUN3226 Exam 2 Study Guide Iron Distribution in the body o Average adult body contains 2 5g Fe females 4g Fe males o Fe is essential to life because it is central in heme which carries oxygen to all living tissues o The distribution in a 70kg male body goes as follows Hemoglobin 2 3rd of Fe is found in hemoglobin is around 2g Storage includes ferritin hemosiderin is around 1g o Tissue Iron mg Myoglobin iron 130mg Enzyme iron 8mg Labile iron pool rapid turnover not found in 1 location 80mg Transferrin 3mg o Hemoglobin organic ring composed of 4 hemes carries Fe o Myoglobin protein that contains heme enclosed in one polypeptide chain porphyrin It stores oxygen used in cellular aerobic metabolism in the muscle Storage o Iron is stored in the liver spleen and bone marrow About 25 30 is stored as ferritin and hemosiderin Males store 1g of iron 3x more than females Females store about 300mg iron this is the basis for the RDAs Ferritin A ball shaped protein the interior of which can hold about 4500 Fe atoms Lower levels of ferritin is a major sign of Fe deficiency Small amounts of ferritin are in the plasma and reflect storage pools Hemosiderin The second storage form of iron Major functions of Fe o Oxygen transport and storage in hemoglobin myoglobin o Fe is also part of enzymes that are involved in the electron transport chain immune system Enzymes in the Krebs cycle Enzymes used by plants in photosynthesis Various plant enzymes used in legumes for nitrogen fixation Dietary Fe o Fe in food is in 2 forms heme non heme Heme Fe is in dietary meat sources Meat contains myoglobin muscle and hemoglobin blood Non heme Fe is in the form of iron salts Found in non meat sources primarily vegetables and grains Also found in iron enriched flour and cereal production To be utilized Fe must be released from various food components by HCl from the stomach proteases from the small intestine Therefore gastric acid and Fe absorption are positively related In people with low gastric acid Fe absorption is low anti acids proton pump inhibitors Fe intake in the U S is between 10 30 mg day depending on meat consumption In the 2001 RDA 8 mg for all men and older women 18 mg for childbearing age women In the last 25 30 years overall meat consumption has slightly decreased meaning that iron from heme sources has also decreased o 2000 kcal mixed American diet provides about 12 mg Fe o For a quick estimate of Fe intake 5 7mg Fe for each 1000 kcal of mixed diet In order to get RDA for Fe women need to consume 3000 kcal rarely the case o Fe is a problem in women who are reducing energy for weight control Need to account for the amount of Fe that is exogenous to the foods The use of aluminum stainless steel and plastic coated pots decreases Fe intake and influences Fe status The opposite is true as well Iron from water that stands in iron pipes and also cooking in iron pots Fe absorption o Fe absorption is most efficiently absorbed in the upper duodenum although it can occur throughout the small intestine o The average person absorbs 5 15 of total iron intake For males this is about 1mg d and females 2mg d Heme Fe is hydrolyzed from the protein globin part and absorbed as such metalloporphyrin This is absorbed easier than non heme Non heme Fe must be released from food components This Fe is primarily in the oxidized Fe or ferric form This form is poorly soluble and is difficult to absorb in this form In the healthy stomach the acid reduces the iron so it is in the ferrous form Fe or reduced state o In patients with achloryhdria or insufficient acid or post gastrectomy or who are taking antacids or acid blockers Fe absorption is depressed since they can t keep it in the ferrous form o Factors that increase Fe absorption all refer to the non heme iron heme is not influenced Vitamin C by far the strongest factor Organic acids including amino acids citric acid and lactic acid Meat Fish Poultry factor MFP factor refers to beef chicken fish lamb and port And the cysteine content of the meats Also peptides from the digestion of myosin and actin appear to enhance absorption All of the above keep Fe in its ferrous form Fe or more readily absorbable form Enhanced erythropoiesis Due to blood loss hemolysis hemorrhage or hypoxia Fe deficient person will absorb more Pregnancy particularly in the last half o Factors that decrease Fe absorption all refer to the non heme iron heme is not influenced Rapid transit time Achlorhydria or any medical surgical condition that increases gastric pH Malabsorption syndromes Phytate in wheat bran chelate Fe Clay pica Tea 60 reduction due to tannins Coffee 40 reduction due to polyphenols Oxalate Overuse of antacids precipitates Fe Calcium might interfere with Fe absorption Iron overload Infection inflammation The interaction of calcium on Fe absorption has potential for being an important factor in women s health A word on Hepcidin o Hepcidin is a newly discovered peptide hormone that regulates iron metabolism via absorption transportation and distribution in cell tissues o It is important in infections by integrating signals from distinct physiological inputs forming a key molecular bridge between iron trafficking and response to infection Fe transport o Transferrin The most important transfer protein It is synthesized in the liver as apotransferrin As Fe enters the blood from intestinal mucosa it is oxidized to Fe by ceruloplasmin another circulating protein Apotransferrin has 2 sites that bind Fe tightly to form Transferrin transports iron to various tissues and to the bone marrow cells Fe deficiency o Fe deficiency is still a serious public health and medical problem that affects many people all over the world It is manifested as Weakness overall malaise Ill health Substandard performance both physical and mental Poor ability to maintain body temperature in a cold environment Infants between 6 months 2 yr who are Fe deficient show Decreased responsiveness and activity they are more fatigued more fearful and exhibit other behavioral abnormalities and impaired psychomotor development In children poor scholastic performance and concentration Decreased resistance to lead poisoning Fe deficiency increases Pb absorption Poor maternal stores may be related to Preterm delivery higher maternal mortality May or may not influence immunity not clear o Fe deficiency anemia the final stage of iron deficiency Meaning without blood or not enough blood There is a difference between iron deficiency and
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