ßby Elena Kuklina ßGDBBS, NHS, Emory University. Consequences of Iron Deficiency “Present knowledge in nutrition”, 7th edition, Yip and Dallmen ßimpaired

by Elena Kuklina GDBBS, NHS, Emory University

Consequences of Iron Deficiency “Present knowledge in nutrition”, 7th edition, Yip and Dallmen

impaired work performancebehavioral abnormalities and impaired

intellectual performanceimpaired capacity to maintain body

temperaturedecreased resistance to infectionsincreased lead absorptionadverse pregnancy outcomes

Iron-deficiency anemia is associated with

CDC guidelines for prevention, detection and treatment of iron deficiency

low birthweight,

generalized undernutrition,

poverty,

and high blood level of lead

Iron compounds “Present knowledge in nutrition”, 7th edition, Yip and Dallmen

HemoglobinMyoglobinCytochromesNADH dehydrogenaseSuccinate dehydrogenaseAconitaseHydrogen peroxidasePhospoenolpyruvate carboxykinaseRibonucleotide reductase

Iron kinetics http://www.rndsystems.com/heme/hhnews/hh697a1.html

(M. Worwood/Clinica Chimica Acta 250 (1997) 3-23)

Hb (RBC)-3000mg Mb (Muscle)-400mg Cytichromes, other

heme and iron sulfur proteins (All tissues)-50mg

Trasferritin ( Plasma and extravascular fluid)-5mg

Ferritin and hemosiderin-0-1000mg

Overview of iron uptake“Advanced Nutrition:Micronutrients”, Berdanier, 1998

Diet iron

Stomach Fe++ + Fe++

Ferric Ferrous

Mucosal CellFe+++

Ferritin

ApoferritinFe++

BloodFe++

Ceruloplasmin or

FerroxidaseTransferrin(Fe+++)

LiverFerritin (Fe+++) and Hemosiderin

Hemoglobin(Fe++)

Bone MarrowMuscle

Other Cells

Bloodloss

Re

Re

Structural Overview of Ferritin

Major iron storage protein

Can store up to 4500 atoms of iron

5-30 % percent is stored as a tissue ferritin (macrophage, hepatocyte, erythrocytes)

Serum ferritin binds only 0.004% of the body's iron

Rationale for TfR in Diagnosis http://www.aacb.asn.au/educ/note/ferr.html

http://www.rndsystems.com/heme/hhnews/hh697a1.html

TfR is a trans membrane protein consisting of two 95 kDa monomers linked by a pair of disulphide bridges

TfR(s) are found on cell membranes and allow iron-binding transferrin to enter the cell

All cells express TR, about 75 % of this expression is found on erythroid precursors

The general structure ofthe transferrin receptor

http://www-rics.bwh.harvard.edu/sickle/iron_transport.html

The molecule is a transmembrane homodimer linked by disulfide bonds

An acyl group attached to the cytoplasmic tail of the molecule anchors the assembly to the plasma membrane

Diferric transferrin binds with higher affinity than monoferric transferrin or apotransferrin

Receptor-mediated transferrin endocytosis


Ferro-transferrin binds to transferrin receptors on the external surface of the cell

The complex is internalized into an endosome, where the pH is lowered to about 5.5

Iron separates from the transferrin molecule, moving into the cell cytoplasm

Receptor-mediated transferrin endocytosis


Here, an iron transport molecule shuttles the iron to various points in the cell, including mitochondria and ferritin

Ferritin molecules accumulate excess iron

Lysosomes engulf aggregates of ferritin molecules in a process termed "autophagy"

Heme synthesis

Succinyl CoA + glycine

δ-aminolevulinic acid (ALA)

(ALA- synthase )B6

Porphobilinogen

Protophyrinogen

Protoporphyrin + IronHeme

The citric acid cycle is the final, common pathway for the oxidation of fuel molecules

http://falcon.sbuniv.edu/~ggray/CHE3364/b1c20out.html

A Simple Overview of the Citric Acid Cycle http://web.indstate.edu:80/thcme/mwking/tca.html

Aconitase is an iron-sulfur protein that catalyzes two reactions:

http://falcon.sbuniv.edu/~ggray/CHE3364/b1c20out.html

Regulation of iron metabolism in cellsM. Shils, Modern Nutrition in Health and Disease, 9 th edition

Sufficient iron(mitochondria,

cytosol)

Deficient iron

Enzymatically active

aconitase

Iron-responsiveelement-

binding protein

Regulation of iron metabolism in cells M. Shils, Modern Nutrition in Health and Disease, 9 th edition

The three proteins determine the availability of iron to meet the needs of cellular metabolism

Apoferritin within cytosolTrasferrin receptors on the cell membraneδ-aminolevulinic acid synthase (ALA-S) within

mitochondria

Schematic representation of the regulation of gene expression by iron


An iron responsive element (IRE) is a nucleotide sequence that forms a stem loop structure with the ability to bind

specific iron binding proteins (IBP) - enzymatically inactive aconitase

The affinity of the IBP for the IRE is greater in the absence of iron

Schematic representation of the regulation of gene expression by iron


For the IRE on the ferritin mRNA, binding an IBP inhibits translation: apoferritin synthesis is suppressed

For the IRE on the TfR mRNA and ALA-S mRNA, binding an IBP stabilizes the mRNA: synthesis of TfR on the cell membrane and ALA-S within mitochondria is increased

Laboratory Diagnosis of Iron Deficiency

Serum Ferritin

Transferrin Saturation

Serum Iron

Transferrin Saturation

Total iron Binding Capacity Transferrin Receptor

Iron deficiency anemiaAnemia of chronic disorders

Thalassemia

Indices - M CV , M CH , M CHC - decreasedRDW increased (reflects the anisocytosis)

Hgb, Hct and RBC -decreased

Biochemical indicators and stages of iron status

“Present knowledge in nutrition”, 7th edition, Yip and Dallmen

Overload

Normal DepletedStores

IronDeficiency

IDAnemia

SerumFerritin

N

TrasferrinSaturation

N N

ErythrocyteProtoporphirin

N N N

MCV N N N N

Hemoglobin N N N N

Red Cell Indiceshttp://www.lrc.arizona.edu/webpath2/TUTORIAL/HGB/RBCMORPH.HTM

RBC Count The number of RBC's per unit volume is measured

directly and given in millions per microliterHb concentration

Hematocrit

Mean cell volume

Red blood cell distribution width


Hemoglobin (Hgb) is the iron-containing protein Hb

in circulating red blood cells The Hgb content is measured directly and given in grams

per deciliter. This value, along with Hct, provides the most useful measure of the oxygen carrying capacity of the blood

Hematocrit (Hct) = RBC count x MCV The Hct is a calculated value and provides a measure of

the amount of oxygen carrying capacity of the blood

Red Cell Indices: Hemoglobinand Hematocrit

CDC guidelines for prevention, detection and treatment of iron deficiency

low cost and the ease and rapidity in performing

Hb is the more direct and sensitive measure

Hct it falls only after the Hb concentration falls

cigarette smoking cause a generalized upward shift in Hb concentration and Hct (adjustment)

cannot be used to determine the cause of anemia

a diagnosis of iron-deficiency anemia can be made if Hb or Hct increases after a course of therapeutic iron supplementation

Red Cell Indiceshttp://www.lrc.arizona.edu/webpath2/TUTORIAL/HGB/RBCMORPH.HTM CDC guidelines for prevention, detection and treatment of iron deficiency

http://www.ironpanel.org.au/AIS/AISdocs/labq1ab.htm

Mean Corpuscular Volume (MCV)

The MCV is measured directly; the unit is a femtoliter. The MCV measures the size of RBC's and is the most important index for classification of anemias into "macrocytic" with higher than normal MCV and "microcytic" with low MCV

If cases of lead poisoning and the anemias of infection, chronic inflammatory disease, and thalassemia minor can be excluded, a low MCV serves as a specific index for iron-deficiency anemia


Red Cell Distribution Width (RDW) = standard deviation of MCV

The RDW is calculated to provide a measure of the anisocytosis, or variation in size of the RBC's

A low MCV together with an increased RDW is strongly suggestive of iron deficiency and when accompanied by an increased erythrocyte protoporphyrin, can be considered diagnostic


Mean Corpuscular Hemoglobin (MCH) = Hgb ÷ RBC count

The MCH is calculated and gives the average mass of Hgb in an individual RBC; the unit is a picogram

Mean Corpuscular Hemoglobin Concentration (MCHC) = Hgb ÷ Hct

The MCHC is calculated and provides a measure of the concentration of Hgb in the cells

Serum ferritin http://www.ironpanel.org.au/AIS/AISdocs/labq1ab.htm

A reliable and sensitive indicator for assessment of iron store

A valid indicator of iron absorptionAn acute phase reactant: inflammation, infection,

malignancy and liver diseaseSex, age, race, BMI, alcohol consumption,

contraceptionA little or no diurnal variation IRMA, IRIA, ELISA

Erythrocyte Protoporphyrin CDC guidelines for prevention, detection

and treatment of iron deficiency

http://www.ironpanel.org.au/AIS/AISdocs/labq1ab.htm Erythrocyte protoporphyrin is the immediate precursor of Hb

The concentration of erythrocyte protoporphyrin in blood increases when insufficient iron is available for Hb production

EP can be easily measured using a hematofluorometer which requires only a couple of drops of blood and minimal technical experience

Inexpensive, clinic-based methods have been developed for measuring erythrocyte protoporphyrin concentration, but these methods can be less reliable than other laboratory methods

Erythrocyte Protoporphyrin CDC guidelines for prevention, detection

and treatment of iron deficiency Infection, inflammation, and lead poisoning as well as iron

deficiency can elevate erythrocyte protoporphyrin concentration

the day-to-day variation within persons for erythrocyte protoporphyrin concentration is less than that for serum iron concentration and transferrin saturation

A high erythrocyte protoporphyrin concentration is an earlier indicator of irondeficient erythropoiesis than is anemia, but it is not as early an indicator of low iron stores

as is low serum ferritin concentration

Transferrin saturation CDC guidelines for prevention, detection

and treatment of iron deficiency Transferrin saturation indicates the extent to

which transferrin has vacant ironbinding sites (e.g., a low transferrin saturation indicates a high proportion of vacant iron-binding sites)

Transferrin saturation (%) =

[serum iron concentration (ug/dL) /

total iron-binding capacity (TIBC) (ug/dL)]

x 100

Serum Iron CDC guidelines for prevention, detection

and treatment of iron deficiency the concentration of serum iron increases after

each meal

infections and inflammations can decrease the concentration

diurnal variation causes the concentration to rise in the morning and fall at night

The day-to-day variation of serum iron concentration within individuals is greater than that for Hb concentration and Hct

TIBC CDC guidelines for prevention, detection

and treatment of iron deficiency inflammation, chronic infection, malignancies,

liver disease, nephrotic syndrome, and malnutrition can lower TIBC readings

oral contraceptive use and pregnancy can raise the readings

the day-to-day variation is less than that for serum iron concentration

TIBC is less sensitive to iron deficiency than is serum ferritin concentration, because changes in TIBC occur after iron stores are depleted

Rationale for TfR in Diagnosishttp://www.aacb.asn.au/educ/note/ferr.html


When the iron supply is inadequate, there is an up-regulation of TfR(s)

2.8-8.5mg/l Value in identifying if

early iron deficiency and in distinguishing of ACD

TR assays are costly, about 3-4 fold more expensive than ferritin assays which are about $4.00/assay

Rationale for TfR in Diagnosishttp://www.ironpanel.org.au/AIS/AISdocs/labq1ab.htm

provides a more stable measurement than transferrin saturation, and

is affected earlier in the development of functional iron deficiency than traditional haematological indices such as the erythrocyte protoporphyrin or MCV

Rationale for TfR in Diagnosis http://www.ironpanel.org.au/AIS/AISdocs/labq1ab.htm

remains normal in patients with acute or chronic inflammation or liver disease

particularly useful in pregnancy (like SF)

relatively new, it is not routinely used in clinical practice or in population screening

Biochemical indicators and stages of iron status (NHANES)

“Present knowledge in nutrition”, 7th edition, Yip and Dallmen

Ferritin Model: Serum FerritinTransferrin SaturationErythrocyte Protoporphirin

MCV Model:Mean Corpuscular VolumeTransferrin SaturationErythrocyte Protoporphirin

Cutoffs for abnormal values of Iron Indicators used in the analysis of NHANES III data

(A. Looker et al, JAMA, March26, 1997, Vol 227, 12)

Age,years

Serumferritinng/ml

TrasferrinSaturation%

ErythrocyteProtopor-thyrin, g/dl RBC

MCV(NHANESII)

1-2 <10 <10 >80(1.42mol/L)

<73

3-5 <10 <12 >70(1.24mol/L)

<75

6-11 <12 <14 >70 <76

12-15 <12 <14 >70 <78

>=16 <12 <15 >70 <80

Cutoffs for abnormal values of Hemoglobinused in the analysis of NHANES III data

(A. Looker et al, JAMA, March26, 1997, Vol 227, 12)

Age, yBothsexes

CutoffValue,g/l

Age, yFemales

CutoffValue,g/l

Age, yMales

CutoffValue,g/l

1-2 <110 12-15 <119 12-15 <126

3-5 <112 16-19 <120 16-19 <136

6-11 <118 20-49 <120 20-49 <137

50-69 <120 50-69 <133

>=70 <118 >=70 <124

Common Laboratory Tests for the Diagnosis of Iron Deficiency in Young Children

Oski: N Engl J Med, Volume 329(3).Jul 15, 1993.190-1931-2 years 3-5 years

Hemoglobin <10.7 g/dL <10.9 g/dL

Hemotocrit <32% <32%

MCV <67 <73

MCH <22 pg <25 pg

MCHC <32 g/dL <32 g/dL

RDW >14.5% >14.5%

RBC Morphology: hypochromic microcyticanemia

http://www.lrc.arizona.edu/webpath2/TUTORIAL/HGB/RBCMORPH.HTM

Megaloblastic anaemiaFrom: Newland: BMJ, Volume 314(7089).April 26, 1997.1262-1265

Megaloblastic anaemia: peripheral blood (top) showing

macrocytes,

tear drops, and

multisegmented neutrophils;

Megaloblastic bone marrow (bottom) showing

megaloblasts,

giant metamyelocytes,

and hypersegmented neutrophil

Differential diagnosis of hypochromic anemia From: Frewin: BMJ, Volume 314(7077).February 1, 1997.360-363

Documents

ßby Elena Kuklina ßGDBBS, NHS, Emory University. Consequences of Iron Deficiency “Present knowledge in nutrition”, 7th edition, Yip and Dallmen ßimpaired