Nutrition & Trace Elements
No description yet. This curated deck is ready for daily study.
Card preview (24)
In what form in iron stored in the body?
Ferritin: 24 subunit protein – MW ~450 kD Binds up to 4500 Fe3+ as hydroxyphosphate Present in most cells, esp. liver, spleen, marrow Readily mobilized as needed Hemosiderin: Insoluble complex derived from ferritin Decreased apoferritin content Releases iron less readily than ferritin
Iron is part of what 5 important things in the body?
1 Hemoglobin (2500 mg) 2 Myoglobin (130 mg) 3 Enzymes, cytochromes (8 mg) 4 Transferrin, plasma (3 mg)
In a typical diet 10-20 mg/day is available yet only 5-10% of that is absorbed. Where does iron absorption take place?
Absorbed in duodenum and jejunum only as Fe2+ Gastric reducing environment (e.g., vitamin C) helpful
How is iron transported within plasma and why?
Free unbound iron is toxic. So it is bound and transported very transferrin. Transferrin: ß-globulin glycoprotein MW 79.5 kD Two Fe3+ binding sites per molecule Trf is in excess; Fe saturation 20-50% typically —–Specific Trf receptor for tissue uptake
How is serum iron measured? What type of specimen can be used?
Specimen: serum or heparinized plasma Principle: Fe3+ is released from binding proteins by acidification Fe3+—> Fe2+ by ascorbate or other reducing agent Fe2+ binds to ferrozine, ferene, or bathophenanthroline and is measured with a spectrophotometer Usually not affected by hemolysis Heme iron not released in assay Test should also include iron-binding capacity Reference Interval: Male 65-170 mcg/dL Female 50-170 mcg/dL Diurnal variation (high in am, low in pm)
How is transferrin measured?
Immunoassay (nephelometry or turbidimetry) Reference interval 200-320 mg/dL
What is TIBC? How is it measured?
TIBC-Total Iron Binding Capacity (semi-automated): Add excess Fe3+ to sample and equilibrate Complex non-bound iron (e.g., MgCO3) and separate Measure Trf-bound iron (as in total iron) Reference interval: 175-400 mcg/dL (iron)
What is UIBC? How is it measured?
UIBC-Unsaturated Iron Binding Capacity (automated) Add excess Fe3+ to sample and equilibrate Measure unbound iron only (no acidification) TIBC = UIBC + serum iron UIBC = Added iron-measured iron Do not report UIBC results, only TIBC (& percent saturation)
How is Transferrin Saturation and Transferrin itself calculated?
Transferrin Saturation = Fe ÷ TIBC (or Trf) —Usually expressed as a percent Transferrin (mg/dL) ≈ 0.8 x TIBC (mcg Fe/dL) TIBC reference interval: 175-400 mcg/dL Trf Sat’n reference interval: 15-60% (TIBC)
Serum ferritin is ______ to stored iron and will _____ as iron stores______.
directly proportional. decrease. deplete.
What are the tree stages of iron deficiency anemia?
Stage 1 : Iron DEPLETION Depletion of iron stores marked by ferritin decrease Normal serum iron and TIBC (ferritin maintains serum levels) No anemia Normal RBC morphology Stage 2: Iron-deficient Erythropoiesis Decreased iron available for erythropoiesis (stores depleted) Decreased ferritin, serum iron, Trf sat’n; increase in TIBC (Trf) No anemia; RBC slightly microcytic, no hypochromia, inc. RDW Stage 3 : Iron DEFICIENCY ANEMIA Decrease in ferritin, iron, Trf sat’n; increase in TIBC (Trf) Decrease in hemoglobin, MCV, MCH, MCHC; inc. RDW Microcytic, hypochromic anemia
Describe the pathogensis of anemia due to chronic disease.
Inflammatory cytokines induce hepcidin production by the liver Hepcidin prevents iron release from enterocytes and macrophages Low available iron interferes with bacterial growth
What role does copper play in the body?
Enzyme cofactor – esp. redox enzymes Bound to ceruloplasmin (α2-globulin)
Copper deficiency leads to…?
Deficiency: Microcytic, hypochromic anemia Neutropenia
Copper excess is called…?
Excess: Wilson’s disease Copper deposition in tissues, esp. liver and brain Decreased ceruloplasmin and serum Cu, plus elevated urine Cu
How is copper measured?
Measure Cu by atomic absorption, ceruloplasmin by immunoassay (nephelometry or turbidimetry)
What are the fat soluble vitamins?
A: carotene, retinol, retinal, retinoic acid Vision Epithelial cell stability D: cholecalciferol Ca2+ absorption E: tocopherols Antioxidant, free radical scavenger K: phylloquinones, menaquinones Synthesis of clotting factors II, VII, IX, X, C and S Cofactor for enzymatic formation of γ-carboxyglutamate
Fat soluble vitamins are readily stored in the body and deficiency slowly develops. What can cause it?
Decreased dietary intake Decreased absorption Biliary deficiency Intestinal malabsorption
Which vitamin is commonly measured? How?
(Vitamin D) by HPLC Vitamin D: LC-MS/MS or immunoassay —-Immunoassay: Must measure both D3 and D2 equally Must displace from binding protein - (D3 bound tighter) —–LC-MS/MS: preferred method but more expensive Reference intervals controversial: 80->150 ng/mL seen)
Vitamin D absorption/conversion can be inhibited by…?
Dec. by pigmented skin, low sun angle (high latitude, winter)
Where is Vitamin D mostly found?
primarily in milk (added), cod liver oil, multi-vitamins, and supplements
UV light converts 7-dehydrocholesterol to what?
vitamin D3—-cholecalciferol
How is Vitamin D metabolized?
UV light + 7-dehydrocholesterol in skin——->Vitamin D3 Vitamin D3 to liver—–>25(OH) Vitamin D In Kidney 25(OH)Vitamin D—->1,25(OH)2 Vitamin D (ACTIVE METABOLITE!!!)—–>Tissue specific Vitamin D response
What is Vitamin D2
Ergocalciferol from ergosterol UV irradiation Of plant origin (yeast and mushrooms) Identical hydoxylations as D3 (1- and 25-) 1,25 diOH D2 has same action as D3 Possible shorter half-life More common form of pharmaceutical vitamin D (in U.S.) OTC supplements are usually D3