Iron Metabolism in
Anaemia of Chronic Disease
Guenter Weiss, MD
Professor of Medicine
Department of Internal Medicine, Clinical
Immunology, and Infectious Diseases
Medical University of Innsbruck
Innsbruck, Austria
Anaemia of Chronic Disease (ACD)
• Most frequent anaemia among hospitalised
patients
• Mild to moderate, normo-/normochromic
• Develops in patients with cellular immune
activation
• Degree of anaemia correlated to immune
activation
Inflammatory Diseases Associated
with the Development of ACD
I. Infections (acute and chronic)
A.
B.
C.
D.
E.
Viral infections including HIV
Bacterial
Parasitic
Fungal
Helminth
II. Malignancies
A.
B.
Haematologic
Solid tumor
III. Autoimmune
A.
B.
C.
D.
Rheumatoid arthritis
Systemic lupus erythematosus and connective tissue
diseases
Vasculitis
Inflammatory bowel disease
IV. Chronic kidney disease and inflammation
Pathophysiology—Cornerstones
• Iron retention within the reticulo-endothelial
system
• Impairment of erythrocyte progenitor formation
• Inadequate formation and function of
erythropoietin
Intestinal Iron Absorption
Enterocyte
Fe3+
Tf Fe3+
DcytB
Hephaestin
Fe2+
Fe2+
DMT1
Heme
Hemeoxygenase
Fe2+
Fe
Luminal
Ferroportin
+
HCP-1
Slide courtesy of G. Weiss, MD
Hentze MW, et al. Cell. 2010;142:24-28.
-
Fe2+
Hepcidin
Baso-lateral
Hepcidin
Master Regulator of Iron Homeostasis
• 20-,22-,25- AA peptide with antimicrobial potential
• Expression induced by iron in the liver
• Stimulated also by LPS and IL-6 by an iron independent
pathway—acute phase protein (blocked by TNF-a)
• Hepcidin over-expression leads to iron-deficient anaemia
and hepcidin knock-out to iron overload
• Hepcidin inhibits duodenal iron absorption and
macrophage iron release
• Mechanism of action: interferes with ferroportin, thereby
leading to ferroportin degradation and blockage of iron
export
Control of Body Iron Homeostasis by
Hepcidin
Luminal
Baso-lateral
Enterocyte
Macrophage
Tf Fe3+
Fe3+
DcytB
HO-1
Heph
Fe2+
Fe2+
DMT1
Heme
Fpn1
-
Fe2+
Fe2+
-
HCP-1?
Heph
Fe
Fpn1
Fe2+
+ HO-1
Hepcidin
Tf-Fe+3
Fe2+
-
Hepcidin
+
+
Tf-Fe+3
Liver
Slide courtesy of Dr. G. Weiss. Hentze MW, et al. Cell. 2010;142:24-28
Tf Fe3+
Inflammation (IL-6, LPS)
Pathophysiology—Cornerstones
• Iron retention within the reticulo-endothelial
system
• Inadequate formation and function of
erythropoietin
• Impairment of erythrocyte progenitor formation
Pathways for Iron Retention in ACD
A collaborative work of acute phase proteins
(Hepcidin) and cytokines
Hepcidin
Hepcidin
+
ACD is an immunity
driven disease
Fe+2 Duodenum
-
Liver
Fe+2
b
+
LPS
Monocyte
CD3+
IL-6
IL-1
TNFα
IL-10
IFN-γ
+
+
Tf/TfR
Fe+2
FP-1
a
Ferritin
Macrophage
+
Fe+2
Hepcidi
n
Slide courtesy of Dr. G. Weiss.
Weiss G. Biochim Biophys Acta. 2009;1790:682-693.
c
Pathophysiology—Cornerstones
• Iron retention within the reticulo-endothelial
system
• Impairment of erythrocyte progenitor formation
• Inadequate formation and function of
erythropoietin
Cytokine Effects on Epo Production
IL-6
LPS
Monocyte
IL-1
TNF-α
IL-10
CD3+
IFN-γ
-
-
?
Epo
Kidneys
Bone marrow
Fe+2
Slide courtesy of Dr. G. Weiss.
Weiss G, Goodnough LT. N Engl J Med. 2005;352:1011-1023.
Putative molecular mechanisms:
• TNF-α/IL-1 induce NF-kB/GATA-2
with suppression of Epo gene
promotor
• Cytokine mediated radical formation
negatively affects Epo-producing cells
in the kidney
• Interaction with Epo/EpoR signal
transduction
(JAK2/STAT5/MAPK/PKC)
• Reduction of EpoR expression on
CFU-e
• Impaired Epo function because of
reduced iron availabiltiy
• Impaired Epo function due to
impaired erythroid progenitor
proliferation
Pathophysiology—Cornerstones
• Iron retention within the reticulo-endothelial
system
• Inadequate formation and function of
erythropoietin
• Impairment of erythrocyte progenitor formation
Cytokine Effects on Erythroid Progenitor
Cell Proliferation
LPS
Monocyte
IL6
IL1
TNF-a
IL-10
CD3+
IFN-abg
Putative molecular mechanisms:
• TNF-α -inhibitory effect via stroma
cells
• IL-1 acts primarily via IFN-g induction
• IFN-γ induces apotposis of CFU-e
• IFN-γ: caspase mediated apoptosis
involving ceramide
Epo
• IFN-γ induces NO; inhibits heme
synthesis
• Cytokines (IFN-γ) inhibit Epo and
SCF formation and functionality
-
Kidneys
Bone marrow
Fe+2
Slide courtesy of Dr. G. Weiss.
Weiss G, Goodnough LT. N Engl J Med. 2005;352:1011-1023.
• Iron restriction due to
cytokines/hepcidin
ACD Is an Immunity-Driven Disease
Hepcidin
Hepcidin
+
Duodenum
Fe+2
-
Liver
LPS
IL-1
Monocyte
Spleen
Fe+2
IL-6
++
Fe
TNF-α
2
IL-10
IFN-γ
CD4+
DMT1
+
Fe+2
Ferritin
Tf/TfR
-
-
Macrophage
-
Epo
Bone marrow -
-
FP-1
Fe+2
Fe+
2
Slide courtesy of Dr. G. Weiss.
+
Hepcidin
Positive Effects of ACD?
• Withholding iron from infectious
pathogens in order to limit their growth1
– Iron acquisition linked to pathogenicity in
microbes, fungi?
• Reducing the supply of oxygen to rapid
proliferating tissues
• Strengthening of immune response
Weinberg ED. Biochim Biophys Acta. 2009;1790:600-605.
Iron Loading of Macrophages Impairs Their Ability to
Kill Intracellular Pathogens by IFN- Mediated Pathways
IFN-
IFNMEF, macrophage effector function
MEF
Macrophage
Fe
+
Fe
MEF
Macrophage
Slide courtesy of Dr. G. Weiss.
Weiss G, Goodnough LT. N Engl J Med. 2005;352:1011-1023. Nairz M, et al. Cell Microbiol. 2009;11:13651381. Wessling-Resnick M. Annu Rev Nutr. 2010;30:105-122.
Iron, Immunity, and Infection
• Iron affects cell-mediated immune function and thus
host responses towards pathogens
• Microbes need iron for proliferation and pathogenicity
• Cytokines and acute-phase proteins regulate iron
metabolism genes under inflammatory conditions,
leading to
– Development of anaemia of chronic disease
– Iron limitation for pathogens
• Thus, ACD may result from the endeavour of the
body to limit the availability of iron for invading
pathogens and to strengthen antimicrobial immune
effector pathways
ACD Diagnosis
Parameter
ACD
IDA
Serum iron concentration
Transferrin levels
Transferrin saturation
Ferritin
Serum transferrin receptor
sTfR/log ferritin
Zinc protoporphyrin IX
Percentage hypochromic RBC
Cytokines (TNF, IL-1, IL-6)
Reduced to normal
Reduced to normal
Reduced to normal
Normal to increased
Normal
Low (<1)
High
N/A
Increased
Reduced
Increased
Reduced
Reduced
Increased
High (>2)
High
High
Normal
Cytokine levels are inversely correlated with the degree of anaemia
Sole iron determination in serum is clinically not useful
Slide courtesy of Dr. G. Weiss.
Several Patients Suffer from a Combination of ACD and
Iron Deficiency (ACD/IDA) as a Consequence of
Inflammatory Anaemia and Blood Loss (Mostly on the
Basis of Gastrointestinal or Urogenital Bleeding)
Parameter
ACD
Both (ACD + IDA)
Reduced
Reduced
Reduced to normal
Reduced
Reduced
Reduced
Normal to increased
Reduced to normal
Normal
Normal to increased
sTfR/log ferritin
Low (<1)
High (>2) ?
Cytokine levels
Increased
Increased
Serum iron
Transferrin levels
TfS
Ferritin
sTfR
Why Is the Differential Diagnosis
Between ACD and ACD + IDA
Important?
Because these patients need
contrasting therapies!
Differential Diagnosis Between ACD and
ACD Plus IDA
Anaemia
Biochemical or clinical
evidence of inflammation
Transferrin saturation <16%
Rule out other causes of anaemia
Ferritin <30 mg/L
Ferritin 30–100 mg/L
Ferritin >100 mg/L
sTfR determination
sTfR/log ferritin >2
ACD/IDA
ACD/IDA
sTfR/log ferritin <1
ACD
With permission from Weiss G, Goodnough LT. N Engl J Med. 2005;352:1011-1023.
Diagnostic Window with sTfR/log Ferritin
How suitable are other haematologic parameters (MCH, MCV,
hepcidin) for the differential diagnosis of ACD vs ACD/IDA?
Anaemia
Biochemical or clinical
evidence of inflammation
Transferrin saturation <16%
Ferritin <30 mg/L
Ferritin 30–100 mg/L
Ferritin >100 mg/L
sTfR determination
sTfR/log ferritin >2
sTfR/log ferritin <1
>1 to <2?
ACD/IDA
ACD/IDA
ACD
With permission from Weiss G, Goodnough LT. N Engl J Med. 2005;352:1011-1023.
Valuable Diagnostic Tools for the Differential
Diagnosis Between ACD and ACD/IDA
(Separated by the sTfR/log Ferritin Ratio)
Parameter
ACD
sTfR/log Ferritin <1
ACD+IDA
sTfR/log Ferritin >2
Haemoglobin
Decreased
Decreased
(No difference from ACD)
Hepcidin
Increased
Significantly lower than in
ACD and in age-matched
controls without anaemia
Normal (as in age-matched
controls without anaemia)
Below the lower limit
of normal
?
Increased
Mean cellular
haemoglobin (MCH)
Number of reticulocytes with
reticulocyte haemoglobin
content (CHr) <29-32pg
sTfR and CHr are also used in combination for the Thomas blot to
estimate iron availability for erythropoiesis in patients with inflammation
Assessment of Iron Status in the
Setting of Inflammation and Anaemia
• Hepcidin expression is more affected by the needs of iron
for erythropoiesis than by inflammation
• Hepcidin levels closely correlate to sTfR/ log ferritin ratio
in patients with inflammation, thus both parameters
(hepcidin currently not widely available) can differentiate
between absolute vs functional iron deficiency
• Haematologic indices (eg, MCH, CHr, and combinations
with sTfR) may add additional information on true iron
availability for erythropoiesis in patients with ACD and/or
sTfR/ log ferritin between 1 and 2
ACD Best Therapy
Treatment or Cure of the
Underlying Disease!
Current Therapeutic Options in ACD
• Blood transfusions
• Recombinant human erythropoietin
• Iron
Therapeutic measures are aimed to increase
haemoglobin levels in ACD patients
However, the impact of such interventions on iron
overload on the reticulo-endothelial system,
immunity, radical formation, and most importantly
the underlying disease, are largely unknown
ACD Therapy
Blood Transfusions
• Can be readily used for rapid correction of
severe anaemia
– Immediate increase of haemoglobin
– 1 unit contains ~200 mg of iron
• Uncertainties
– Negative effects on immune effector function
 Risk of infections
 In some studies, associated with increased risk of cancer
(Possible bias – more need for transfusions may reflect more
advanced disease)
 Negative effects seen with transfusions older than 3 weeks?
 Effects also seen with leukocyte-depleted products?
ACD Therapy
Iron
• NO, if infections or cancer underlie ACD;
ferritin >100 ng/mL
– May favor proliferation of pathogens
 By countering iron-withholding strategy
 By impairing immune function
– May not reach erythroid cells due to diversion into
reticulo-endothelial system
– May cause tissue damage via formation of toxic
radicals by the Fenton reaction (triggered by TNF-a)
• However, in autoimmune diseases, iron may
inhibit pro-inflammatory immune effector
pathways, thus reducing disease activity
Kaltwasser JP, et al. J Rheumatol 2001; 28:2430-2436.
Weiss G, et al. Kidney Int. 2003;64:572-578.
ACD Therapy
Iron
• What to do in ACD with true iron deficiency
(ACD and IDA)?
– Iron is needed for basic metabolic functions and
cannot be mobilized
• How to substitute iron?
– Iron is very poorly absorbed in ACD (downregulation of ferroportin in the duodenum by
hepcidin)1
1. Theurl I, et al. Blood. 2009;113:5277-5286.
ACD Therapy
Iron
• What to do in ACD with true iron deficiency (ACD
and bleeding)?
– Iron is needed for basic metabolic functions and cannot be
mobilized
• How to substitute iron?
– Iron is very poorly absorbed in ACD (down-regulation of
ferroportin in the duodenum by hepcidin)1
• IV iron administration is very effective in
inflammatory bowel disease and ACD but also
increases haemoglobin in cancer patients2
• Caveat
– No prospective studies on such intervention on the course
of underlying malignant diseases
– Retrospective analyses: iron supplementation may
negatively impact disease progression in cancer
1. Theurl I, et al. Blood. 2009;113:5277-5286. 2. Auerbach M, et al. J Clin Oncol. 2004;22:1301-1307.
Iron Therapy in Dialysis Patients
 Prospective study investigating the incidence of
infectious complications in ESRD patients
receiving IV iron therapy
―
―
―
Group 1: ferritin <100 ng/mL and TfS <20%
Group 2: ferritin >100 ng/mL and TfS >20%
Observation period: 1 year
 Frequency of septicaemia in Group 2 was 2.5fold higher than in Group 1
 Too much iron may be harmful in ACD!
Plotkin SA. Clin Infect Dis. 2004;38:1030-1039.
Why Is the Differential Diagnosis
Between ACD and ACD + IDA
Important?
Because these patients need
contrasting therapies!!!
No iron in ACD
Iron needed in ACD/IDA
Therapy—
Erythropoietin-Stimulating Agents (ESA)
• Effective in increasing haemoglobin levels in
ACD: patients with cancer, infections, and
autoimmune disorders
• Response rate to treatment depends on
underlying disease, stage, immune activation,
and iron availability
• Increase of haemoglobin with ESA treatment is
associated with a gain in QOL and a decreased
need for blood transfusions
• Uncertainties based on recent studies indicating
increased mortality in certain patient groups in
association with ESA therapy; biologic role of
EpoR on tumor cells undefined
Therapeutic End Points
• Optimal haemoglobin related to the course of
the disease underlying ACD, minimization of
cardiovascular risk, best QOL?
• The maximum incremental gain in QOL in
patients with anaemia and cancer occurs
(upon anaemia treatment with ESA) when the
haemoglobin is between 11 and 13 g/dL1
• However, a normal target haemoglobin may
not be optimal!
1. Crawford J, et al. Cancer. 2002;95:888-895.
Therapeutic End Points
• Normalization of haemoglobin levels in end stage
renal disease patients was associated with a
significant increase of cardiovascular mortality as
compared with patients with haemoglobin levels
below the normal range1
• Dialysis patients: risk of death was highest with
haematocrit levels between 33% and 36%2
• Avoid over-correction of anaemia (Hgb >12 g/dL)
• Currently recommended therapeutic end point:
Hgb 11–12 g/dL (some guidelines cite up to
13 g/dL for men)
1. Besarab A, et al. N Engl J Med. 1998;339:584-590. 2. Locatelli F, et al. Nephrol Dial Transplant.
2004;19:121-132.
Anaemia of Chronic Disease
Unanswered Questions—THERAPY
• Effects of anaemia correction by different
treatments (iron, transfusion, ESA) on the
underlying disease
• Evaluation of the positive effects
(radio/chemosensitizer, cardiac performance,
QOL) vs the putative negative effects (feeding
of pathogens, immunodepression) of various
treatments
Anemia of Chronic Disease
Unanswered Questions—THERAPY
• Urgent need for randomized, prospective trials
– Definition of therapeutic end points, which are
associated with
 Good QOL
 Best outcome concerning the underlying disease
 Cardiovascular endpoints
• Emerging therapies
–
–
–
–
–
(Anti)-cytokine therapies
Iron chelation
Hepcidin/ferroportin agonists/antagonists
Combination therapy (Epo + iron)
Epo R modulation