Trace elements
Lecture from pathological physiology
Oliver Rácz
2009/2013
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Trace elements - overview
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The elements of life
Current knowledge and unanswered questions
Iron metabolism
Zinc and copper
Vanadium, nickel, molybdenium, cobalt
Selenium
Iodine and fluorine
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Elements of life
• Main biogenic elements - 6
– C, H, N, O, & P, S
• Electrolytes
– Na+, K+, Mg++, Ca++ against Cl- (?)
• Trace, < 1 g with two exceptions (Fe, Zn)
– metals: Fe, Zn, Cu, Mn, Mo, Cr, Co, V, Sn
– most of them transition metals (complexes)
– nonmetals: F, I, Se, Si, B
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Elements of life - be careful!
• Not the same as the elements found in human body:
– As, Au, Pb, Hg….(contaminations)
• Strong selection:
– Earth crust - O, Si, Al, Fe, Ca
– Sea water ? Sea when life was arising ?
– Element composition of plants resembles that of soil
• Life is „easy“ - first half of Mendelejev table,
only 4 with atomic No > 30:
34Se (79) ,42Mo (96), 50Sn (119), 53I (127)
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Trace elements - current
knowledge - 1
• Composition of body, tissues, cells, O.K.
• Form - metals only as complexes!
– Stable complexes are well known (heme,
molybdopterin, etc.)
– Less stable complexes are difficult to study
– Added to biochemical structures after their
synthesis - with exception of Se
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Trace elements - current
knowledge - 2
• Cycles in biosphere - natural & influenced by
human activity (ecology)  influence on health
• Cycles in human body - many unanswered
questions
• Clinical chemistry
– Only iron status is routinely assessed
– Plasmatic levels do not reflect metabolism
– Indirect markers - e.g. GPX for Se
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Essential or toxic ?
+---------------------------------------------------------------------+
¦
¦
BIOGÉNNE PRVKY
¦
¦
¦
+-----------------------------------------+---------------------¦
¦
¦ HLAVNÉ ¦ELEKTROLYTY¦
STOPOVÉ
¦
TOXICKÉ
¦
¦
¦
¦
¦ a
¦b
¦
¦
+-----+--------+-----------+-------------+------+---------------------¦
¦ I
¦ 1H
¦ 11Na 19K ¦ 29Cu
¦
¦ 47Ag 79Au
¦
¦ II ¦
¦ 12Mg 20Ca ¦ 30Zn
¦
¦ 4Be 48Cd 56Ba 80Hg ¦
¦ III ¦
¦
¦
¦ 5B
¦ 5B 13Al
¦
¦ IV ¦ 6C
¦
¦ 50Sn
¦14Si ¦ 82Pb
¦
¦ V
¦ 7N 15P ¦
¦ 23V
¦
¦ 33As 73Ta 83Bi
¦
¦ VI ¦ 8O 16S ¦
¦ 24Cr 42Mo
¦34Se ¦ 24Cr 34Se 42Mo
¦
¦ VII ¦
¦ 17Cl
¦ 25Mn
¦9F 53I¦ 9F 35Br
¦
¦ VIII¦
¦
¦ 26Fe27Co28Ni¦
¦ 26Fe 27Co 28Ni
¦
+---------------------------------------------------------------------+
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Supplementaion ?
• RDA = recommended daily allowance
• Enough for deficiency prevention
• New system - DRI = daily recommended intake
–
–
–
–
Estimated average requirement
RDA
Adequate intake
Upper limit
• YES - Fe, Zn, Cr, Se, I, F (if indicated)
• NO - Cu, V, Mn, Ni, Co, Sn, Si
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Iron distribution
Total amount
4000 mg 100 %
Haemoglobin
2500
63
Myoglobin
160
4
Enzymes (catalase)
8
0,2
Stores (ferritin)
1350
33
Transport
(transferrin)
5
0,12
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Iron balance
• Destruction of red
cells
(0,8 % /day @ 20 ml)
20 - 25 mg Fe/ day
• 90 - 95 % recycled!
• Losses only 1 - 2 mg/d
• Average diet
10 - 15 mg/ day
controlled resorbtion
1 - 2 mg/d
Physiologic increased losses:
Menstruation: 30 mg, gravidity 300 mg, lactation 180 mg
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Diagnosis ?
• Anemia - suspected sideropenia
• Serum iron (m: 14 - 29, w: 12 - 23 mmol/l)
is not sufficient for dg. !!!
• TIBS, total iron binding capacity is a simple and
not expensive assay
• Ferritin assay ? if you are rich, it is an excellent
marker of total stores (plasma: 40 - 50 ng/l)
• Transferrin assay ? (2 - 3 mg/l), fluctuating
• Soluble transferrin receptor assay
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Iron binding capacity (TIBC)
• 1. Iron assay from serum (16)
• Excess iron added to the sample saturation of transferrin to 100 %
• Removal on non bound iron
• 2. Iron assay (64)
• Saturation index = 16/64 = 0,25 (25 %)
• < 0,2 = sideropenia; > 0,55 = iron excess
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Iron deficiency and excess
• Sideropenia is common in women living in poor
countries – repeated gravidities, infections, poor
nutrition
• In rich countries - achlorhydria & diseases
associated with chronic blood loss - kidney,
gynecologic diseases, peptic ulcer
• Strict vegetarians - children
• 3 stages, microcytic hypochromic anemia is the
last
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Iron deficiency and excess
• Popeye, the brave seaman and the spinach
• Mistake - spinach is not a good source of iron
(meat)
• Bigger mistake - iron excess is a risk factor of
coronary heart disease
• Hereditary haemochromatosis - our european
heritage (10 - 15 thousand years ago)
• Secondary haemochromatosis (Sickle cell
disease and transfusions)
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Clinical manifestation of haemochromatosis
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Bronze-colored skin
Hepatomegalia, later liver cirrhosis
Painful damage of joints
Disorders of endocrine glands (e.g. diabetes bronze).
Cardiomyopathy
Chronic fatigue syndrome
Loss of libido, impotency
Oxidative stress and accelerated atherosclerosis already
in latent stage
 Factors of manifestation: sex (m>w), nutrition (meat),
excess alcohol consumption
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Hemochromatosis
and the regulation of iron resorbtion
 OMIM *235200; carrier frequency 0,045 - 0,071 (!)
 Homozygotes 2 - 5/1000
 HFE gene in HLA region, 1 common mutation
 1999 HFE2 - long arm, ch. 1
 2000 HFE3 - 7q22, transferrin receptor 2
 2001 HFE4 - ch 2; SCL40A1 gene for ferroportin
 2003 HAMP gene; ch 1 for hepcidin
 2004 HJV gene for hemojuvelin
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Hemochromatosis
and the regulation of iron resorbtion
 For general practice these extremely rare
conditions are not important but
 they are important to understand the
physiological regulation of iron resorbtion
 The main regulator is the hepcidin from liver
 increased expression in experiment - Fe deficiency
 mutation or decreased expression – Fe excess
 and also hemojuvelin
And iron accumulation in substantia nigra Parkinsonism
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Zinc, Zn
2 - 3 g; RDA 12 - 15 mg
• Constituent of enzymes (cca 300) and other
proteins ( insulin crystalls)
• Smell and taste receptors, ion channels
• Not a catalyst
• Stabilisation of proper spatial structure of
domains - zinc fingers, regulating gene
expression
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Zn - history
• Nihil album (ZnO) used already in Middle Ages ro
treat eye and skin diseases
• 1746 A.S. Margaff, Germany
• 1869 - 1957 essential micronutrient for plants and
domestic animals, deficiency described
• 1940 - 1961 essential for man, Zn-proteins
described
• 1974 RDA
• Now intensive research about marginal deficiency
not only in human but also in veterinary medicine
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Zn-metalloenzymes and proteins
• DNA polymerase
• Zn-Cu SOD
• Retinol
dehydrogenase
• Collagenase
• Metallothionein
• Zn fingers
• Thymulin
• Steroid receptors
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• NA synthesis, cell division
• Antioxidant defense
• Regeneration of visual
pigment
• Connective tissue, vessel
wall
• Transport
• Gene expression
• T lymfocyte differentiation !
• Endocrine functions
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Zinc, Zn - deficiency
2 - 3 g; RDA 12 - 15 mg
• Sources, liver, kidney, mushrooms, red beet
• Small stores, phytates from cereals block
resorbtion
• Marginal deficiency is probably common repeated infections, growth retardation
• Severe deficiency
– Middle East - cereals
– Alcoholism, cirrhosis, nefrotic & malabosrbtion sy.
• Hereditary disturbance of absorbtion -
acrodermatitis enteropathica
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Copper, Cu
100 - 150 mg; RDA 2 - 5 mg
• Muscles, bones, liver
• Active centre of many enzymes, mainly
oxidoreductases
• Cu++ + e-  Cu+
• Superoxddismutase, lysyloxidase,
cytochromoxidase and others
• Ceruloplasmin is the main transporter of
copper
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Cu metabolism, deficiency and excess
• Sources: nuts, oysters, sea fish
• Binding to albumin, transcuprein and in the liver to
ceruloplasmin
• Excretion through bile
• Deficiency - experimental and severe malnutrition anemia, leukopenia, brittle bones
• Accumulation in obstructive icterus,
• Intoxication - diarrhoe, liver damage
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Hereditary pathological conditions
• m. Wilson is a hereditary deficiency of
coeruloplasmin - hepatolenticular degeneration
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–
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Autosomal recessive, 1/30 000 newborns
Free copper induces oxidative damage
ATP7B 13q14; 200 different mutation, 1 common
Different clinical manifestation, from mild (only higher
transaminases and Kayser-Fleischer ring to serious
liver damage, hemolysis and neurological/psychiatric
spts.
• KF ring = green/brown ring in cornea = deposit of Cu
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Hereditary pathological conditions
• Menkes’ kinky hair syndrome
– X chromosome related, ATP7A (1/250 000)
– disorder of intracellular transport of Cu
– Low activity of key copper enzymes (SOD,
Cytochromoxidase, etc.)
– Severe fatal disease with progressive
neurological spts., connective tissue, skin,
digestion
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m. Wilson
Index
Norm
Ceruloplazmin
1,8 – 2,5 mmol/l < 1,8 mmol/l
Cu – plasma
16 – 31 mmol/l < 16 mmol/l
Cu – liver
30 – 50 mg/g
100 – 150 mg/g
Cu – urine
traces
100 mg/d
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m. Wilson – case report
• 22 yearold man, elevated transaminases during
investigation for blood donation
• All possible causes of liver disease excluded
• Targeted laboratory assays - m. Wilson
• Two sisters - asymptomatic form, one healthy
• No Kayser – Fleischer ring
• Think of it! – molecular genetic dg. is possible
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Morbus Wilson
Age
Father
59
S-Cu
mmol/l
16,1
Mother
56
12,0
0,42
0,24
Son
22
2,7
1,50
0,00
Daughter1
31
2,6
0,88
0,03
Daughter2
29
15,7
0,54
0,39
Daughter3
25
3,8
1,9
0,00
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Du-Cu
mmol/d
0,35
CPL
g/l
0,37
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m. Wilson – case report
• Manifestation mostly in age 8 - 20 y.
• Mostly liver damage, if liver failure and
mental deterioration is present, too late for
therapy!
– Dysartria, dysphagia, rigidity, tremor,
psychiatric symptoms
• Th: penicillamin, Zn, trietyltetramin, also
liver transplantation
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Chromium, Cr
1 mg, decrease with age
• Very toxic
• In complex form (picolinate) increases insulin
sensitivity
• Prevention of impaired glucose tolerance
• Adjuvant therapy in Type 2 diabetes
• Cr activates a step in insulin induced signal
pathway (2003)
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Vanadium, manganese, nickel cobalt, a
molybdenium
• Vanadium
– No deficiency in humans, intoxication is possible
– Insulin like effect in vitro ?
• Manganese, nickel
– No deficiency syndromes
• Cobalt
– very toxic - additive to beer - cardiomypathy
– only as the constituent of vitamin B12
• Molybdenium (molybdopterin)
– No deficiency in humans, intoxication is possible
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Selenium, Se
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•
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Toxic compound (semi-condcuctors)
m. Keshan (China), cardiomyopathy
No selenium in soil, plants, food
Active center of glutathione peroxidase (GPX), key
enzyme of antioxidant defense
• Involved also in iodine metabolism
• Selenocysteine is incorporated to peptide chain
during synthesis
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Selenium, Se
• Sources: garlic, yeast, sea fish
• Marginal deficiency in many countries of Europe
(SK, H, PL, CZ)
• RDA m: 70 mg; w: 50 mg,
• Recently up to 200 mg
• Supplementation is recommended in
atherosclerosis and cancer prevention
• In 2001 after 10 years of supplementation
significantly less prostata and colon cancer
• Not a panacea
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Iodine, I
Metabolism, differentiation, CNS development
• Thyroid gland and hormones (TG, T3, T4)
• RDA: 100 - 200 mg/d
• Deficiency threatens cca 1 billion people living in
mountains but also in lowlands (far from sea),
• This country: In the past high incidence of
endemic goiter
• Sources: seafood, egg yolk / salt iodidation
• Strumigens (cabbage) block thyroid metabolism
• Normal urine excretion > 100 mg/d
• USG volume measurement of thyroid
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Requirements
Group
RDA, mg/d Ioduria mg/l
adults and
adolescents
gravidity
150
100 – 200
200
200 – 300
newborns
90
> 150
children, 6mo – 6y
90
180 – 220
children, 6 – 12y
120
100 – 200
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Consequences of iodine deficiency
Embryo
abortion,
malformations
Newborn increased mortality
goiter, hypothyreosis
psychosomatic retardation
cretenism
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Child
goiter, hypothyreosis
psychosomatic retardation
cretenism
Adult
goiter, hypothyreosis
low IQ
cretenism
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Markers of iodine metabolism
Ioduria, mg/l Deficiency
< 20
severe
20 – 50
significant
50 – 100
mild
100 – 200
no
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Volume of
thyroid
ml (USG)
men
< 22 ml
women
< 18 ml
children
according to
body surface
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Fluorine, F - metabolic toxin/caries
prevention
• Already 0,1 mmol/l fluoride blocks bacterial
enolase
• Fluoroapatite, forming 10 % tooth enamel is more
resistant as hydroxyapatite
• Fluorine helps convert amorph
calciumphosphate into crystallic apatite
 Tooth pasta, mouthwash, KF pills, 1 - 2 mg/d
 Fluoridation of tap water
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