Iron Metabolism/Ca And Other Minerals

Question 1

Iron in non-heme structures

Answer 1

. Non-heme proteins have iron-sulfur cluster proteins (NADH dehydrogenase, dehydrogenase, ferrochelatase)
. Single Fe-containing proteins (Phe hydroxylase)
. Oxygen-bridged iron (ribonucleotide reductase)

Question 2

Amount of Fe in adult

Answer 2

. 2-4 g w/ 60-70% present in Hb

. Remainder in Mb or storage

Question 3

Iron found in diet

Answer 3

. Heme Fe: less abundant but readily absorbed (red meat, poultry, some fish)
. Non-here Fe: more abundant but not as easily absorbed (enriched cereal, spinach, lentils, and beans)

Question 4

Enhancers of Fe absorption

Answer 4

. Vit. C
. Organic acids
. Reducing sugars
. Meat factor

Question 5

Inhibitors of absorption

Answer 5

. Dietary fibers/phytates (grains, veggies) 
. Polyphenols veggies, tea, coffee)
. Ca
. Carbonates 
. Polyphenols 
. Oxalates 
. Tannates (tea, coffee)

Question 6

Fe homeostasis

Answer 6

. Closed system, losses o only 1-2 mg/day and are unregulated
. Maintenance dependent on regulation of absorption
. Hepcidin (25-AA antimicrobial) synthesized in hepatocytes binds to ferroportion to promote cellular internalization of hepcidin-ferroportin complex and lysosomal degradation

Question 7

Potential causes of Fe deficiency

Answer 7

. Inadequate absorption: poor bioavailability, antacid therapy, excess dietary bran or starch, competition from other metals, low/dysfunctional enterocytes, bowel resection, celiac, IBD)
. Inc. loss: GI, GU, Pulmonary, or other blood losses

Question 8

Anemia of chronic disease

Answer 8

. Occurs as consequence of cytokines-mediated impaired ability to boiling Fe from storage stores and neg. effects on EPO production and erythropoesis
. Treat underlying disease
. Blood transfusions
. Administration of erythropoietic agents

Question 9

Hereditary hemochromatosis

Answer 9

. Genetic disorder of Fe metabolism where Fe absorption is unregulated and excess Fe is deposited in organs (liver, pancreas, heart, joints, skin)
. Leads to liver cirrhosis, hepatocellular carcinoma, DM, HF, and arthritis
. Type one is assoc. w/ HFE gene mutation
. Treatment: regular phlebotomy

Question 10

Secondary forms of Fe overload

Answer 10

. Consequence of chronic transfusion therapy in patients w/ thalassemia and aplastic anemia

Question 11

Calcium

Answer 11

. Most abundant mineral in body (1,000 g)
. Important in m. Contraction, hemostasis, and cell signaling
. Highly regulated w/in 9-10 mg/dL
. Achieved via PTH, vit. D, and calcitonin on bone, kidney and intestine

Question 12

Ca homeostasis

Answer 12

. Plasma Ca has half bound to albumin and other half is complexed w/ organic anions, phosphate, or free
. Measure of serum Ca used to measure ionized Ca
. Ca-sensing receptor is assoc. w/ PTH secreting cells

Question 13

Hypercalcemia

Answer 13

. Common metabolic emergency

. Primary hyperparathyroidism from parathyroid adenomatous and cancer

Question 14

Hypocalcemia

Answer 14

. Due to hypoparathyroidism due to surgical removal

. Hypoalbuminemia, hyperphosphatemia, and vit. D deficiency/resistance

Question 15

Vit. D related disorders

Answer 15

. Leads to altered Ca and PO4metabolism

. Manifest as rockers

Question 16

Magnesium

Answer 16

. 25g in human Boyd w/ over half found in teeth
. Functions in charge neutralization (stabilize polyphosphateS)
. Bind to induce activation or stabilize active conformation of enzymes

Question 17

Mg deficiency

Answer 17

. Symptoms non-specific (neuromuscular issues, cardiovascular problems, anorexia, nausea, personality changes)
. GI disorders and renal loss can cause this

Question 18

Mg toxicity

Answer 18

. Due to excessive intake of Mg salts (antacids, laxatives) esp. when combined w/ renal insufficiency
. Nonspecific symptoms: hypotension, vomiting, cardiac arrhythmias, muscle weakness, hyporeflexia

Question 19

zinc

Answer 19

. 1.5 mg in girls, 2.5 in boys
. Mainly in skeletal mm. And bone
. Essential for growth and reproduction, wound healing, taste sensation, and immune function
. Plays catalytic/structural role in over 200 enzymes, stabilization of biomembrane, component of Zn-finger proteins (TFs)
. Dietary sources: shellfish, beef, and other red meat, fortified cereal (attached to physic acid and prevents some absorption)
. RDA: 15 mg men and 12 for women

Question 20

Metallothionein

Answer 20

. Cys-rich protein which binds Zn is important mediator of Zn absorption
. When Zn intake is high, metallothionein synthesis in intestinal cells inc. and less Zn is released into portal circulation
. When intake is low, less is synthesized and more Zn is released into circulation
. Also binds to copper

Question 21

Zn deficiency

Answer 21

. Uncommon
. Occurs in patients w/ acrodermatitis enteropathica (rare genetic disease causing dec. Zn absorption)
. Causes: patients w/ Fe/Cu overload, anticonvulsant drugs, pregnancy, elderly, and diarrhea

Question 22

Clinical manifestations of Zn deficiency

Answer 22

. Delayed growth, sexual maturation, impotence
. Hypogonadism and hypothermia 
. Alopecia 
. Acroorificial skin lesions 
. Delayed wound healing 
. Immune dysfunction 
. Impaired taste and appetite 
. Eye lesions 
. Behavioral abnormalities

Question 23

Zn toxicity

Answer 23

. Rare
. Similar to Cu deficiency symptoms, dec. HDL-C, gastric function, and impaired immune function, may result from long-term ingestion of Zn supplements

Question 24

Copper

Answer 24

. Important for Cu-containing compounds, erythropoesis, and erythrocyte function, platelet function, lipoprotein metabolism, cardiac function, and immune function
. Sources: organ meats, shell fish, nuts, seeds, legumes, chocolate
. Daily intake 1.5-3 mg

Question 25

Copper absorption and transport

Answer 25

. Occurs in SI and is inc. or dec. based on Cu intake
. Cu enters portal circulation and is transported to liver for incorporation into Cu-containing compounds (ceruloplasmin protein in blood)

Question 26

Cu deficiency and toxicity

Answer 26

. Premature babies, babies fed cow’s milk, patients w. Malabsorption issues, patients using high dose zinc supplements, patients receiving long-term parenteral nutrition support

Question 27

Menkes’ disease

Answer 27

. Rare x-linked disease
. Caused by mutation in ATP7A gene
. Causes impaired absorption of Cu from diet and a lethal copper deficiency (death by age 3)

Question 28

Wilson’s disease

Answer 28

. Autosomal recessive disease caused by mutation in ATP7B gene
. Leads to impaired Cu excretion in bile
. Massive deposition of Cu in liver and other organs leading to Cu toxicity
. Treatment: chelation therapy

Question 29

Selenium

Answer 29

. Essential component of selenoproteins that function in antioxidant detoxification, thyroid hormone metabolism, and regulation of cellular redox status
. Co-translational incorporation of selenocysteine into proteins is facilitated via stem-loop structure in mRNA facilitating read through of UGA as selenocysteine
. Sources: organ meats, seafood, Brazil nuts, meat and poultry, some plant foods

Question 30

Other essential minerals

Answer 30

. Molybdenum
. Manganese
. Chromium
. Ultra traces minerals (boron, silicon, nickel)