Subject: iron/epilepsy
J Neurol Neurosurg Psychiatry 2001 Apr;70(4):551-3
Iron overload without the C282Y mutation in patients with epilepsy.
Ikeda M
Department of Clinical Research, National Saigata Hospital,
Ohgata-machi, Niigata 949-3193, Japan massie@saigata-nh.go.jp
[Medline record in process]
To test the hypothesis that iron overload predisposes to epilepsy,
transferrin saturation in 130 patients with epilepsy and sex and age
matched 128 control subjects without epilepsy were studied. Mean
transferrin saturation was significantly higher in the epilepsy group
(39.9 (SD 19.6)%) than in the control group (29.1 (SD 14.9)%).
Abnormally high transferrin saturations (men>60%, women>48%) were
found in 10 patients with epilepsy but in only one subject without
epilepsy. Antiepileptic drugs did not affect the transferrin
saturation. Of the 11 with abnormally high transferrin saturation, two
with epilepsy were heterozygotic for H63D in the haemochromatosis gene
but no patient had the C282Y mutation. These results indicate that
iron overload other than the C282Y mutation underlies epilepsy.
PMID: 11254788, UI: 21154196
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Iron overload without the C282Y mutation in patients with epilepsy
Masayuki Ikeda*, M.D.
*Department of Clinical Research, National Saigata Hospital
Ohgata-machi, Niigata 949-3193, JAPAN
Correspondence to: Dr. Masayuki Ikeda
Department of Clinical Research, National Saigata Hospital,
Ohgata-machi, Niigata 949-3193, JAPAN, Phone +81-255-34-3131, Fax
+81-255-34-6734 (e-mail: massie@saigata-nh.go.jp)
Abstract
To test the hypothesis that iron overload predisposes to epilepsy, I
studied transferrin saturation in 130 patients with epilepsy and sex-
and age-matched 128 control subjects without epilepsy. I found that
transferrin saturation was significantly higher in the epilepsy group
(39.9±19.6 %: mean ± SD) than in the control group (29.1±14.9 %).
Abnormally high transferrin saturations (men: > 60%, women: >50%) were
found in 10 patients with epilepsy but in only one subject without
epilepsy. Antiepileptic drugs did not affect the transferrin
saturation. Of the 11 with abnormally high transferrin saturation, two
with epilepsy were heterozygotic for H63D in the haemochromatosis gene
but no patient had the C282Y mutation. These results indicate that
iron overload other than the C282Y mutation underlies epilepsy.
Keywords: Epilepsy, Haemochromatosis, Iron Overload
Iron accumulation results in the formation of free radicals and
subsequent brain injury.[1] Neurological diseases associated with iron
overload vary: asymptomatic deposition of iron in the basal
ganglia,[2] psychiatric diseases,[3] mental retardation,[4]
parkinsonism,[5][6] dementia, ataxia and myoclonic jerks.[7] Siderosis
in the brain is associated with epilepsy.[8][9] Animal studies suggest
that iron accumulation may underlie the pathophysiology of
epilepsy.[10][11]
The aim of my study was to test the iron metabolism of epileptic
patients. I measured transferrin saturation as an index of iron
overload in patients with epilepsy and age- and sex-matched control
subjects. In patients with high transferrin saturations, I also
examined mutations in the haemochromatosis gene (HFE ).
Patients and Methods
Patients
I studied 258 subjects, 130 patients with epilepsy (63 men, 67 women,
aged 38.7 ± 10.3 years: mean ± SD) and 128 sex- and age-matched (63
men, 65 women, aged 40.8 ± 10.3 years) control subjects without
epilepsy. I excluded subjects with pica, those receiving
iron-containing drugs, blood transfusions or alcohol. None of the
subjects studied got haematologic diseases or active liver diseases.
All subjects, whether epileptic or not, were mentally retarded and
cared for by the nursing staff of Ranzan Institute in Saitama, Japan.
All of them could eat and did not receive forced nutrition. Although I
did not make a quantitative comparison, I found no obvious difference
between the two groups in daily activities.
Methods
Measurement of serum iron, transferrin and ferritin
Serum samples after an overnight fast were obtained from each subject.
I measured serum iron by standard spectrophotometry. Serum transferrin
levels were determined by rate immunoturbidimetry on an automated
analyser (model TBA-20FR, Toshiba Medical, Tokyo, Japan). Serum
ferritin levels were measured by chemiluminescence immunoassay (Eiken
Chemical Co.,Ltd., Tokyo) in patients with high transferrin saturation
(men: > 60%, women: >50%).
Identification of the C282Y and H63D mutations in HFE
I also examined HFE mutations in 11 patients with abnormally high
transferrin saturation. The mutation study was approved by the ethics
committee at Ranzan institute. Since the subjects could not understand
the explanation of the study due to mental retardation, I obtained
written informed consent from their parents or legal guardians.
HFE contains two common missense mutations.[12] One mutation (guanine
to adenine at nucleotide 845) in HFE results in the substitution of
tyrosine for cysteine at amino acid 282 and is termed the C282Y
mutation. The other mutation (cytosine to guanine at nucleotide 187)
in HFE results in the substitution of aspartate for histidine at amino
acid 63 and is termed the H63D mutation.
PCR amplification of the regions containing the missense mutations was
performed with the primer sequences of Feder et al..[12] The C282Y and
the H63D mutations were identified with allele-specific
oligonucleotide hybridisation.[13]
Ethical considerations
After detailed explanations of the study, written informed consent was
obtained from the family or legal guardian of each patient. I
performed this study after the approval by the committee for human
investigations of Ranzan Institute.
Statistical analysis
All values are presented as means ± SD. Differences between means were
analysed by a two-tailed StudentÕs t-test or Mann-WhitneyÕs U-test.
Results
The serum iron was significantly higher ( P < 0.01 ) in the epilepsy
group (106 ± 8 µg/dL) than in the control group (88 ± 8 µg/dL) while
the unsaturated iron binding capacity was significantly lower ( P <
0.01 ) in the epilepsy group (173±78 µg/dL) than in the control group
(228 ± 76 µg/dL). Thus, the transferrin saturation was significantly
higher ( P < 0.01 ) in the epilepsy group (39.9±19.6 %) than in the
control group (29.1±14.9 %). On the assumption that some
antiepileptics may affect iron metabolism, I compared the degrees of
transferrin saturation in the subgroups within the epilepsy group
according to the prescribed drugs (Table 1). There was no significant
difference in transferrin saturation between the subjects who were
taking one of the four antiepileptic drugs and those who were not.
Table 2 shows that an abnormal increase in transferrin saturation
(men: > 60%, women: >50%) was found in 11 patients (5 men and 6 women)
consisting of 10 patients with epilepsy and only one in the control
group. I found no cause of secondary iron overload in these patients.
Serum ferritin was not increased in any of them. Among the 11
patients, two were heterozygous for H63D. Both of them were epileptic.
No C282Y mutation was found in any of the 11 patients with abnormally
high transferrin saturations.
Discussion
I found that the transferrin saturation was significantly higher in
patients with epilepsy than in those without epilepsy. Moreover,
abnormally high transferrin saturations were found in 10 patients in
the epilepsy group but only in one in the control group. These data
indicate iron overloa(HOME) d in the patients with epilepsy. Factors which
cause secondary iron overload, including diet, blood transfusions,
alcohol, liver injury and haematologic diseases, were ruled out.
Antiepileptic drugs cannot explain the iron overload in epileptic
patients, either. Since phenytoin is an iron-chelator,[14] it would
reduce iron load rather than increase it. Previous studies on rats and
mice showed that administration of phenytoin, phenobarbital or
primidone does not change the iron concentration in the serum or
brain.[15][16] My data, showing that none of the antiepileptics
affected the transferrin saturation, also provide evidence that the
higher transferrin saturation in the epilepsy group is not due to
antiepileptics.
I then studied mutations in HFE because haemochromatosis is the most
common disease of primary iron overload. I found two patients
hetetozygotic for the H63D mutation, but no patient with the C282Y
mutation. Haemochromatosis is thought to be uncommon in Japanese,[17]
but the frequency is unknown. Merryweather-Clarke and others [18]
reported that the C282Y mutation was most frequent in northern
European populations and absent from 484 Asian chromosomes. The
positive predictive value of the transferrin saturation test, i. e. ,
the possibility that a patient with a positive result actually has
haemochromatosis, is unknown in Japanese.
I do not assume that heterozygosity for H63D affects iron metabolism
in epileptic patients, because its high frequency in control
populations, ranging from 16 to 23%,[19] makes the heterozygosity for
H63D unlikely to be pathogenic. H63D is probably deleterious only in
compound heterozygotes (heterozygous for both C282Y and H63D).[20] To
determine the cause of iron overload in patients with epilepsy, I
continue to look at other genes regulating iron metabolism in these
patients.
Acknowledgements
I acknowledge the invaluable co-operation of Professor Ernest Beutler
in HFE mutation analysis. I am grateful to Drs Akiko Takaki, Shunji
Takaki and Kenji Kuroda at Ranzan Institute for obtaining the informed
consent of the patients and to Dr Toshiyuki Himi at Tokyo Medical and
Dental University for the DNA extraction.
References
1. Halliwell B. Reactive oxygen species and the central nervous
system. J Neurochem 1992;59:1609-1623.
2. Berg D, Hoggenmuller U, Hofmann E, Fischer R, et al. The basal
ganglia in haemochromatosis. Neuroradiology 2000;42:9-13.
3. Cutler P. Iron overload and psychiatric illness. Can J Psychiatry
1994;39:8-11.
4. Milder MS, Cook JD, Stray S, Finch CA. Idiopathic hemochromatosis,
an interim report. Medicine 1980;59:34-49.
5. Nielsen JE, Jensen LN, Krabbe K. Hereditary haemochromatosis: a
case of iron accumulation in the basal ganglia associated with a
parkinsonian syndrome. J Neurol Neurosurg Psychiatry 1995;59:318-21.
6. Miyasaki K, Murao S, Koizumi N. Hemochromatosis associated with
brain lesions--a disorder of trace-metal binding proteins and/or
polymers? J Neuropathol Exp Neurol 1977;36:964-76.
7. Jones HJ, Hedley WE. Idiopathic hemochromatosis (IHC): dementia and
ataxia as presenting signs. Neurology 1983;33:1479-83.
8. Hughes JT, Oppenheimer DR. Superficial siderosis of the central
nervous system. A report on nine cases with autopsy. Acta Neuropathol
(Berl) 1969;13:56-74.
9. Rojas G, Messen L. Generalized cytosiderosis in two cases of
progressive myoclonic epilepsy with Lafora inclusion bodies.
Histopathological and ultrastructural studies. Neurocirugia
1968;26:3-11.
10. Campbell KA, Bank B, Milgram NW. Epileptogenic effects of
electrolytic lesions in the hippocampus: role of iron deposition. Exp
Neurol 1984;86:506-14.
11. Willmore LJ, Hiramatsu M, Kochi H, Mori A. Formation of superoxide
radicals after FeCl3 injection into rat isocortex. Brain Res
1983;277:393-6.
12. Feder JN, Gnirke A, Thomas W, Tsuchihashi Z, et al. A novel MHC
class I-like gene is mutated in patients with hereditary
haemochromatosis. Nature Genet 1996;13:399-408.
13. Beutler E, Gelbart T. Large-scale screening for HFE mutations:
Methodology and cost. Genet Test 2000;4:131-142.
14. Garzon P, Garcia LP, Garcia EJ, Almodovar CC, et al. Iron binding
to nutrients containing fiber and phenytoin. Gen Pharmacol
1986;17:661-4.
15. Critchfield JW, Carl FG, Keen CL. Anticonvulsant-induced changes
in tissue manganese, zinc, copper, and iron concentrations in Wistar
rats. Metabolism 1993;42:907-10.
16. Pick CG, Statter M, Ben SD, Youdim MB, Yanai J. Normal zinc and
iron concentrations in mice after early exposure to phenobarbital. Int
J Dev Neurosci 1987;5:391-8.
17. Witte DL, Crosby WH, Edwards CQ, Fairbanks VF, Mitros FA. Practice
guideline development task force of the College of American
Pathologists. Hereditary hemochromatosis. Clin Chim Acta
1996;245:139-200.
18. Merryweather-Clarke AT, Pointon JJ, Shearman JD, Robson KJ. Global
prevalence of putative haemochromatosis mutations. J Med Genet
1997;34:275-8.
19. Burke W, Thomson E, Khoury MJ, McDonnell SM, et al. Hereditary
hemochromatosis: gene discovery and its implications for
population-based screening. JAMA 1998;280:172-8.
20. Beutler E. The significance of the 187G (H63D) mutation in
hemochromatosis. Am J Hum Genet 1997;61:762-4.
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Cell Mol Biol (Noisy-le-grand) 2000 Jun;46(4):743-60
Iron involvement in neural damage and microgliosis in models of
neurodegenerative diseases.
Shoham S, Youdim MB
Research Department, Herzog Hospital, Jerusalem, Israel.
sshoham@md2.huji.ac.il
In several neurodegenerative diseases, iron accumulates at sites of
brain pathology. Since post-mortem examination cannot distinguish
whether iron accumulation caused the damage or resulted from damage,
it is necessary to manipulate iron in animal and tissue culture models
to assess its causal role(s). However, only in models of Parkinson's
disease and of global ischemia, iron deprivation (ID) or
iron-chelators have been used to protect from damage. In these
studies, documentation of microgliosis was not performed even though
several lines of evidence converge to suggest that activation of
microglia is an important source of oxidative stress. In the kainate
model of epilepsy, we found that ID protected the olfactory cortex,
thalamus and hippocampus and attenuated microgliosis, whereas iron
supplementation to ID rats increased damage and microgliosis in the
above regions. In the hilus of the hippocampal dentate gyrus, even
though no cell loss was observed, ID attenuated microgliosis and
iron-supplementation increased it. Thus there is a tight relationship
between iron and microgliosis. In addition, iron+zinc supplementation
dramatically increased damage to hippocampal CA1 whereas zinc
supplementation alone had no effect. This study demonstrates an
anatomically unique interaction of iron and zinc, which may lead to
new insights to neurodegeneration in epilepsy.
Publication Types:
* Review
* Review, academic
PMID: 10875437, UI: 20331692
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