P22176285
Regular Article
Hyperhomocysteinemia in Tunisian bipolar I patients
Asma Ezzaher,P h D,1,2*Dhouha Haj Mouhamed,P h D,1,2Anwar Mechri,P h D,2
Asma Omezzine,P h D,3Fadoua Neffati,P h D,1Wahiba Douki,P h D,1,2Ali Bouslama,P h D,3 Lot?Gaha,P h D2and Mohamed Fadhel Najjar,P h D1
1Laboratory of Biochemistry-Toxicology and2Research Laboratory‘Vulnerability to Psychotic Disorders’,Department of Psychiatry,Monastir University Hospital,Monastir and3Laboratory of Biochemistry,Sahloul University Hospital,Sousse, Tunisia
Aims:The aim of the present study was to investigate hyperhomocysteinemia in Tunisian bipolar I patients according to5,10-methylenetetrahydrofolate reduc-tase(MTHFR)C677T polymorphism.
Methods:The subjects consisted of92patients with bipolar I disorder diagnosed according to DSM-IV, and170controls.Plasma total homocysteine,folate and vitamin B12were measured.MTHFR C677T polymorphism was determined by polymerase chain reaction–restriction fragment length polymorphism. Results:Compared with controls,patients had a sig-ni?cantly higher homocysteine level(16.4?9.8vs 9.6?4.5m mol/L;P<0.001)and a signi?cantly lower folate level(3.2?0.9vs 6.5?3.2m g/L; P<0.001).C677T MTHFR polymorphism genotype frequencies were in Hardy–Weinberg equilibrium. After adjustment for MTHFR C677T genotypes,hypo-folatemia,hypovitamin B12and for potential confounding factors,the odds ratio(OR)of hyperhomocysteinemia associated with bipolar disorder remained signi?cant(OR, 5.53;95%con?dence interval: 1.92–15.86;P=0.001).In patients,there was no signi?cant change in hyperho-mocysteinemia,hypofolatemia and hypovitamin B12with regard to the clinical and therapeutic char-acteristics,whereas the highest prevalence of hyper-homocysteinemia was found in depressive patients and when illness duration was>12years.Hypo-folatemia was seen in all patients on lithium and in the majority of patients on carbamazepine,and the highest prevalence of hypovitamin B12was noted in patients taking carbamazepine.
Conclusion:Hyperhomocysteinemia was more fre-quent in bipolar I patients independent of C677T polymorphism.Patients had reduced levels of folate, which modulates homocysteine metabolism.Indeed, this?nding indicates that folate supplementation may be appropriate for bipolar patients with hyperhomocysteinemia.
Key words:bipolar I disorder,folate,homocysteine, MTHFR C677T polymorphism.
H OMOCYSTEINE IS A non-protein-forming
sulfur amino acid that has two metabolic path-ways:re-methylation to methionine(requiring folate and vitamin B12);and trans-sulfuration(con-densation with serine to form cystathionine).High concentrations of homocysteine are neurotoxic,and relatively high plasma homocysteine levels have been reported in some psychiatric disorders.1High levels of homocysteine may be toxic to dopaminergic neu-rons,2and dysfunction of dopamine neurons has been implicated in bipolar disorder.3The exact mechanisms underlying the hyperhomocysteinemia in this disease are not completely understood,and the?ndings are controversial.Several hypotheses have been postulated including nutritional folate and vitamin B de?ciency,and/or reduced glomerular ?ltration rate in bipolar patients.4Further-more,common genetic polymorphisms in the
*Correspondence:Asma Ezzaher,PhD,Laboratory of
Biochemistry-Toxicology,Monastir University Hospital,Monastir
5000,Tunisia.Email:ezzaherasma@yahoo.fr
Received21February2011;revised14September2011;accepted23
September2011.
Psychiatry and Clinical Neurosciences2011;65:664–671doi:10.1111/j.1440-1819.2011.02284.x 664?2011The Authors
methylenetetrahydrofolate reductase(MTHFR)gene explain some of the variance in homocysteine levels, with C677T being the most extensively investigated single nucleotide polymorphism:C677T leading to a substitution of alanine with valine.This functional mutation results in diminished enzyme activity,with the TT homozygote variants having only30%and the TC heterozygotes65%enzyme activity compared to the CC wild type.5The low enzyme activity of MTHFR has several consequences,particularly increased homocysteine levels in the blood and altered methy-lation status.2Additionally,this increase could be related to psychopharmacological medication.It is well known that anticonvulsants such as carbam-azepine,phenytoin and phenobarbital can cause elevated homocysteine concentrations.6
The aim of the present study was to investigate hyperhomocysteinemia in Tunisian bipolar I patients according to MTHFR C677T polymorphism and to explore its relationship to the sociodemographic, clinical and therapeutic characteristics of this patient group.
METHODS
Subjects
This study was approved by the local ethics commit-tee and all subjects were of Tunisian origin.The patient sample consisted of92patients from the psy-chiatry department of Monastir University Hospital, Tunisia.The mean age was36.0?11.1years,and there were30women(mean age,35.0?12.2years) and62men(mean age,36.6?10.6years).Consen-sus on the diagnosis,according to the DSM-IV crite-ria,7was made by psychiatrists.The exclusion criteria were age<18years,other psychiatric illnesses,epi-lepsy,mental retardation,hormone therapy,history of vitamin use,diabetes,cardiovascular disease, thyroid dysfunction,liver disease,or renal dysfunc-tion.The control group consisted of170volunteer subjects.The mean age was43.7?14.2years,and there were91women(mean age,42.2?14.6years) and79men(mean age,45.5?13.6years).None of the controls had psychiatric illnesses,epilepsy, mental retardation,hormone therapy,history of vitamin use,diabetes,cardiovascular disease,thyroid dysfunction,liver disease or renal dysfunction. Written informed consent was obtained from all voluntary participants.
All subjects were questioned about their age, gender,previous treatments and smoking and alcohol habits.
Homocysteine,folate and vitamin
B12determination
Venous blood samples were collected after an over-night fast.Homocysteine,folate,and vitamin B12 levels were determined in all subjects.Blood was drawn into tubes containing ethylenediamine tetra-acetic acid/K3,immediately placed on ice,and centri-fuged at4°C.Plasma was separated and immediately stored at-80°C until analysis.Plasma homocysteine concentration(normal,<15m mol/L)was determined using?uorescent polarization immunoassay on AxSYM(Abbott Laboratories,Abbott Park,IL,USA). Folate(normal,>3.7m g/L)and vitamin B12(normal, >187ng/L)were determined using microparticle enzyme immunoassay on Elecsys2010(Roche Diag-nostics,Indianapolis,IN,USA).
Clinical evaluation
The body mass index(BMI)was calculated as weight (kg)divided by height(m2).Obesity was de?ned as BMI?30kg/m2.8
Genotyping
Genomic DNA was extracted from venous blood DNA using the salting-out method.9C677T MTHFR polymorphism was studied by standard protocol as described previously by Belkahla et al.10
Statistical analysis
Statistical analysis was performed using SPSS17.0 (SPSS,Chicago,IL,USA).Quantitative variables were presented as mean?SD and comparisons were per-formed using Student’s https://www.360docs.net/doc/d77659658.html,parisons of quali-tative variables were performed using the c2test. Odds ratio(OR)and95%con?dence interval(CI) were calculated.Adjustment for potential confound-ing parameters was determined by binary logistic regression.Statistical signi?cance was set at P<0.05.
RESULTS
The sociodemographic,clinical and therapeutic subject characteristics are listed in Table1.We noted
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a signi?cant difference between patients and controls in gender,age,cigarette smoking and hypertension.Therefore,these variables were considered as poten-tial confounding factors for this analysis.
Compared to controls,bipolar patients had a sig-ni?cantly higher level of homocysteine (16.4?9.8vs 9.6?4.5m mol/L,P <0.001)and a signi?cantly lower level of folatemia (3.2?0.9vs 6.5?3.2m g/L,P <0.001),but no signi?cant variation in mean vitamin B12was found (Table 2).In addition,the prevalence of hyperhomocysteinemia was signi?-cantly higher in bipolar I patients than controls (37%vs 10.6%,P =0.001)(Table 3).
Table 3lists the genotype distribution of C677T polymorphism.Genotypes were in Hardy–Weinberg equilibrium and were similarly distributed between patients and controls (Table 3).
To evaluate the adjusted relationship between bipolar I disorder and hyperhomocysteinemia,and C677T polymorphism,we ?rst calculated the OR of bipolar I disorder associated with hyperhomocys-teinemia and adjusted for confounding factors (gender,age,cigarette smoking,hypertension,hypo-folatemia,hypovitamin B12and C677T polymor-phism).We noted a signi?cant association between bipolar I disorder and hyperhomocysteinemia (OR,5.53;95%CI: 1.92–15.86;P =0.001)(Table 3).Second,we calculated the OR of bipolar I disorder associated with C667T polymorphism and adjusted for confounding factors (gender,age,cigarette smoking and hypertension).We noted that this poly-morphism was not signi?cantly associated with this disease (Table 3).
Signi?cant hyperhomocysteinemia and hypo-folatemia were noted in patients compared to con-trols regardless of C677T genotype.The TT genotype of C677T MTHFR polymorphism was signi?cantly associated with hyperhomocysteinemia and with
Table 1.Subject characteristics
Bipolar I patients Control group P (n =92)(n =170)n (%)
n (%)Gender:Male/Female (ratio)62/30(2.07)79/91(0.87)0.001Age (years),mean ?SD 36.0?11.143.7?14.2<0.001BMI (kg/m 2),mean ?SD 26.6?4.526.7?5.10.87Cigarette smoking 48(52.2)41(24.1)<0.001Hypertension
3(3.3)0(0)0.01Current illness episode Depressive 14(15.2)––Euthymic 52(56.5)––Manic 26(28.3)––Treatment
Valproic acid 46(50)––Lithium
10(10.9)––Carbamazepine
9(9.8)––Valproic acid and lithium 3(3.2)Antipsychotics 24(26.1)
–
–
BMI,body mass index.
Table 2.Homocysteine,folate,vitamin B12plasma concentration
Bipolar I patients Controls P (n =92)(n =170)mean ?SD
mean ?SD Homocysteine (m mol/L)16.4?9.89.6?4.5<0.001Folate (m g/L)
3.2?0.9 6.5?3.2<0.001Vitamin B12(ng/L)
362?208
339?227
0.43
666 A.Ezzaher et al .Psychiatry and Clinical Neurosciences 2011;65:664–671
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hypofolatemia when compared to the CC and CT genotypes in all subjects (Table 4).
Table 5shows that homocysteine was signi?cantly higher in both male and female patients compared to control subjects of the same gender,and folatemia was signi?cantly lower in patients compared to control subjects regardless of gender.In patients,men had signi?cantly higher homocysteine and lower folatemia than women.In contrast,no signi?cant association was found between vitamin B12and gender.
Patients had signi?cantly higher homocysteine than controls regardless of age.Moreover,we noted that patients aged <60years had signi?cantly lower folatemia and those aged <25years had signi?cantly higher vitamin B12than controls of the same age (Table 6).There was no signi?cant variation in prevalence of hyperhomocysteinemia,hypofolatemia and hypovi-tamin B12with regard to episode and duration of illness,while the highest prevalence of hyperho-mocysteinemia was found in depressive patients (57.1%)and when duration of illness was >12years (77.3%).Additionally,there was no difference in the parameters according to treatment,while hypo-folatemia was seen in all patients on lithium and in the majority of patients on carbamazepine (approx.80%).In addition,the highest prevalence of hypovi-tamin B12(22.2%)was noted in patients taking carbamazepine (Table 7).
Moreover,after exclusion of patients on mood sta-bilizers,the difference between patients and controls with regard to homocysteine and folate remained signi?cant.
Table 3.C677T polymorphism distribution vs hyperhomocysteinemia
Bipolar I patients Controls OR Adjusted 95%CI P (n =92)(n =170)(%)
(%)Hyperhomocysteinemia 3710.6 5.53? 1.92–15.860.001C677T MTHFR CC 44.555.51?
–
–CT 43.536.1 1.48?0.79–2.730.21TT
12
8.4
1.33?
0.77–2.28
0.29
?
OR adjusted for gender,age,cigarette smoking,hypertension,hypofolatemia,hypovitamin B12and C677T MTHFR.?OR adjusted for gender,age,cigarette smoking and hypertension.
CI,con?dence interval;MTHFR,5,10-methylenetetrahydrofolate reductase;OR,odds ratio.
Table 4.Homocysteine,folate and vitamin B12plasma concentration vs C677T genotype
Parameters
C677T genotype Bipolar I patients Controls P ?(n =92)(n =170)mean ?SD mean ?SD Homocysteine (m mol/L)
CC 15.2?9.2a 8.0?4.4a <0.001CT 15.1?5.8b 10.8?2.9b <0.001TT 25.5?17.4c 14.1?4.9c 0.04?
P =0.04?
P <0.001Folate (m g/L)
CC 3.3?0.77.2?3.5<0.001CT 3.3?1.0 5.9?3.1<0.001TT 2.7?0.6 4.8?2.90.03?
P =0.05?
P =0.02Vitamin B12(ng/L)
CC 316?131347?2350.44CT 415?265344?2480.19TT
340?173301?850.51
?
P =0.09
?
P =0.84
?
ANOVA ;
?Student’s t -test.
For bipolar I patients:a vs c and b vs c;P =0.005;for controls:a vs b;a vs c:P <0.001;b vs c:P =0.02.
Psychiatry and Clinical Neurosciences 2011;65:664–671Hyperhomocysteinemia in bipolar I patients 667
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DISCUSSION
Compared with controls,bipolar I patients had sig-ni?cantly higher levels of homocysteine and signi?-cantly lower levels of folatemia.Additionally,a signi?cant association was found between bipolar I disorder and hyperhomocysteinemia(37%vs10.6%; OR,5.53;95%CI:1.92–15.86;P=0.001).At a high
concentration,homocysteine is considered to be a
neurotoxic substance,causing activation of N-methyl D-aspartate receptors and leading to excitotoxicity.By impairing neural plasticity and promoting neuronal
degeneration,homocysteine could contribute to the
pathogenesis of neurodegenerative and psychiatric disorders.11Additionally,homocysteine is a methyl donor to S-adenosylmethionine when activated, suggesting that aberrant DNA methylation due to hyperhomocysteinemia may be involved in the pathogenesis of bipolar disorder as well as in schizophrenia.12
Table6.Homocysteine,folate and vitamin B12vs age
Homocysteine Folate Vitamin
(m mol/L)(m g/L)B12(ng/L) Bipolar I patients
Age(years)
<25(17/11)12.8?3.0a 3.4?0.8a323?135a ?26–59(73/124)17.1?10.7b 3.2?0.9b373?223?60(2/24)21.3?10.0c 2.8?0.8282?21 P0.2080.5280.582 Controls
Age(years)
<25(17/11)9.2?2.7 6.1?3.0215?102?26–59(73/124)9.0?4.2? 6.6?3.2?340?204?60(2/24)12.4?5.0? 6.0?3.9?399?338 P0.0030.6830.086
a P<0.05between patients and controls for age<25years;
b P<0.05between patients and controls for age between26 and59years;
c P<0.05between patients an
d controls for ag
e ?60years;?vs?:P<0.05.
Table5.Homocysteine,folate and vitamin B12vs gender
Homocysteine Folate Vitamin B12
(m mol/L)(m g/L)(ng/L)
Bipolar I patients
Male18.0?10.7 3.1?0.8369?236
Female13.0?6.5 3.6?0.9346?133
P0.0060.0040.550
Controls
Male10.7?5.0 6.3?3.4314?211
Female8.6?3.7 6.7?3.3361?239
P0.0030.4550.213
Table7.Hyperhomocysteinemia,hypofolatemia and hypovitamin B12vs bipolar I treatment
Clinical and treatment characteristics Homocysteine Folate Vitamin B12 (?15m mol/L)(?3.7m g/L)(?187ng/L) n(%)n(%)n(%)
Current illness episode
Depressive(n=14)8(57.1)9(64.3)1(7.1) Euthymic(n=52)17(32.7)36(69.2)6(11.5) Manic(n=26)9(34.6)20(76.9)2(7.8)
P0.230.660.81
Illness duration?
<12years(n=53)17(32.1)35(66)7(13.2)
?12years(n=39)17(77.3)30(76.9)2(5.3)
P0.250.250.19 Treatments
Valproic acid(n=46)16(34.8)29(63)4(8.7) Lithium(n=10)5(50)10(100)0(0) Carbamazepine(n=9)3(33.3)7(77.8)2(22.2) Valproic acid/lithium(n=3)2(66.7)2(66.7)0(0) Antipsychotics(n=24)8(33.3)17(70.8)3(12.5)
P0.700.220.51
?12is a median.
668 A.Ezzaher et al.Psychiatry and Clinical Neurosciences2011;65:664–671?2011The Authors
In contrast,folate appears to in?uence the synthe-sis rate of tetrahydrobiopterin,a cofactor in the hydroxylation of phenylalanine and tryptophan, rate-limiting steps in the biosynthesis of dopamine, norepinephrine,and serotonin,neurotransmitters postulated to play a role in the monoamine hypoth-esis of affective disorders.In addition,methyl tet-rahydrofolate has been shown to bind to presynaptic glutamate receptors,where it may potentially modu-late the release of other neurotransmitters,including the monoamines.13
Moreover,some studies have shown that lower folatemia in patients with psychiatric disorders can be due to their nutritional status.14Indeed,poor appetite as a symptom of bipolar disorder could lead to decreased intake of B vitamins,which could then lead to elevated homocysteine concentrations.15 Hyperhomocysteinemia has long been identi?ed as a risk factor for vascular disease.Lowering of homocysteine concentration is done by treating with folic acid,or possibly vitamin B12and vitamin B6, which might reduce the risk of both cardiovascular and cerebrovascular disease.Long-term prophylactic studies with folic acid are therefore under way.16
In patients,men had the signi?cantly highest level of homocysteine and the signi?cantly lowest level of folate.This is in line with results reported by Mennen et al.,who suggested that most classic cardiovascular disease risk factors were associated with homocys-teine in men but not in women.17Furthermore,none of the lifestyle determinants was the same in women and men.
With regard to age,we found that patients had signi?cantly higher homocysteine levels than con-trols regardless of this characteristic.Moreover, patients aged<60years had signi?cantly lower folatemia and those aged<25years had signi?cantly higher vitamin B12than controls of the same age. This could con?rm the effect of bipolar disorder on perturbations of these parameters.Indeed,this disease is known to appear at an early age.
A signi?cant increase in homocysteine and a decrease in folate were noted in patients compared to controls regardless of C677T genotype.The TT geno-type of C677T MTHFR polymorphism was signi?-cantly associated with hyperhomocysteinemia and with low levels of folate when compared to the CC and CT genotypes in all subjects.The results are consistent with previous reports noting that increased homocysteine and decreased folate and vitamin B12levels were associated with pathogenesis of bipolar disorder but not with C677T MTHFR
polymorphism.18
In the present study we did not?nd any signi?cant
association between C677T MTHFR polymorphism
and bipolar disorder.This is in line with other
studies,19–22although some researchers have found an
association between the distributions of the geno-
types of MTHFR polymorphism and this disease.23–25
In the present study there was no signi?cant varia-
tion in prevalence of hyperhomocysteinemia,hypo-
folatemia and hypovitamin B12with regard to
episode and duration of illness,while the highest
prevalence of hyperhomocysteinemia was found in
depressive patients and when duration of illness was >12years.These?ndings are in part in consistent with previous studies.Ozbek et al.showed that these
parameters were not related to illness duration.18Fur-
thermore,Hasanah et al.reported that low folate may
cause a vulnerability to mania as much as to depres-
sion.26Affective disorder,regardless of mania and
depression,will result in low red-cell folate level.
Considering that reduced red-cell folate has a
correlation with reduced cerebrospinal?uid
5-hydroxyindoleacetic acid,a de?cit of brain seroto-
nin may also be responsible for mania.
Analysis of the therapeutic characteristics showed
that drug usage appears to have an effect on the
vitamin status.Indeed,all patients on lithium and
the majority taking carbamazepine(approx.80%)
had hypofolatemia.In addition,the highest preva-
lence of hypovitamin B12(22.2%)was noted in
patients taking carbamazepine.Therefore,theses
?ndings can explain the differences in the studied
parameters between patients and controls and may
be an indicator of an unhealthy lifestyle in patients.
Additionally,these results are consistent with the
Hasanah et al.study,which suggested that prolonged
medication and chronic illness may affect nutritional
intake,and medication may interfere with folate
absorption in the gut.26In contrast,the present?nd-
ings are not in agreement with other studies.Dierkes
and Westphal showed that carbamazepine can cause
elevated homocysteine concentration,6although
Ozbek et al.showed that homocysteine,folate and
vitamin B12were not related to drug usage.18Addi-
tionally,Osher et al.reported that there were no sig-
ni?cant differences in homocysteine level between
patients receiving versus those not receiving lithium,
neuroleptics or valproate.1
The mechanisms by which thymoregulators
induce folate depletion are still unclear;the pro-
Psychiatry and Clinical Neurosciences2011;65:664–671Hyperhomocysteinemia in bipolar I patients669
?2011The Authors
posed mechanisms can be summarized as(i)inter-ference with the intestinal absorption of folate;(ii) induction of enzymes in the liver that require and ?nally deplete folate;and(iii)interference with the metabolism of folate co-enzymes.27It has been suggested that phenytoin and carbamazepine,as enzyme inducers,can directly modulate the activity of different liver enzymes.Liver enzyme induction may cause depletion of the cofactor involved,folic acid,pyridoxal5′-phosphate and vitamin B12, leading to the alterations observed in homocysteine status.28
Limitations
Several methodological limitations should be consid-ered when interpreting these?ndings.First,a larger sample size would be bene?cial.Second,the work is a cross-sectional study that does not permit follow up of biological parameters.Third the sample of bipolar patients may not be representative of more heteroge-neous populations.Finally,the diagnosis of controls was made by psychiatrists but without formal use of structured instruments to exclude psychiatric disorders in controls.
CONCLUSION
Hyperhomocysteinemia was more frequent in bipolar I patients but was not associated with C677T polymorphism.After adjustment for MTHFR C677T genotype,hypofolatemia,hypovitamin B12and potential confounding parameters,hyperhomocys-teinemia associated with bipolar disorder remained signi?cant.There was no signi?cant variation in prevalence of hyperhomocysteinemia,hypofolatemia and hypovitamin B12with regard to episode and duration of illness,while the highest prevalence of hyperhomocysteinemia was found in depressive patients and when duration of illness was>12years. Additionally,there was no difference in the param-eters according to treatment,while hypofolatemia was seen in all patients on lithium and in the major-ity of patients on carbamazepine.In addition,the highest prevalence of hypovitamin B12was noted in patients taking carbamazepine.Therefore,a folate supplement may be appropriate in bipolar patients with hyperhomocysteinemia.Additionally,they should undergo regular testing of homocysteine and vitamin status.Clinicians should track the effects of treatment on the physical and the biological param-eters,and should facilitate access to appropriate medical care.
ACKNOWLEDGMENTS
The authors thank the present subjects for their assis-tance in this study.The authors thank Mr Samir Boukattaya for his help with the manuscript. REFERENCES
1.Osher Y,Bersudsky Y,Silver H et al.Neuropsychological
correlates of homocysteine levels in euthymic bipolar patients.J.Affect.Disord.2008;105:229–233.
2.Lee ES,Chen H,Soliman KF et al.Effects of homocysteine
on the dopaminergic system and behavior in rodents.
Neurotoxicology2005;26:361–371.
3.Greene JG.Gene expression pro?les of brain dopamine
neurons and relevance to neuropsychiatric disease.J.
Physiol.2006;575:411–416.
4.Vuksan-C′usa B,Jakovljevic′M,?agud M et al.Metabolic
syndrome and serum homocysteine in patients with bipolar disorder and schizophrenia treated with SGA.Psy-chiatry Res.2011;189:21–25.
5.Frosst P,Blom HJ,Milos R et al.A candidate genetic risk
factor for vascular disease:A common mutation in meth-ylenetetrahydrofolate reductase.Nat.Genet.1995;10: 111–113.
6.Dierkes J,Westphal S.Effect of drugs on homocysteine
concentrations.Semin.Vasc.Med.2005;5:124–139.
7.American Psychiatric Association.Diagnostic and Statistical
Manual of Mental Disorders,4th edn.American Psychiatric Association,Washington,DC,2004.
8.World Health Organization.Obesity:Preventing and Man-
aging the Global Epidemic(publication WHO/NUT/NCD/
98.1).World Health Organization,Geneva,1997.
https://www.360docs.net/doc/d77659658.html,ler SA,Dykes DD,Polesky HF.A simple salting out
procedure for extracting DNA from human nucleated cells.Nucleic Acids Res.1988;16:1215.
10.Belkahla R,Omezzine A,Kchok K et al.Effet des polymor-
phismes des enzymes clés du métabolisme de l’homocystéine sur l’homocystéinémie et le risque coro-narien chez une population tunisienne.Ann.Cardiol.
Angeiol.2008;57:219–224.
11.Ipcioglu OM,Ozcan O,Gultepe M et al.Reduced urinary
excretion of homocysteine could be the reason of elevated plasma homocysteine in patients with psychiatric ill-nesses.Clin.Biochem.2008;41:831–835.
https://www.360docs.net/doc/d77659658.html,l J,Tang T,Kaminsky Z et al.Epigenomic pro?ling
reveals DNA-methylation changes associated with major psychosis.Am.J.Hum.Genet.2008;82:696–711.
13.Atmaca M,Tezcan E,Kulolu M et al.Serum folate
and homocysteine levels in patients with
670 A.Ezzaher et al.Psychiatry and Clinical Neurosciences2011;65:664–671?2011The Authors
obsessive-compulsive disorder.Psychiatry Clin.Neurosci.
2005;59:616–620.
14.Reif A,Pfuhlmann B,Lesch KP.Homocysteinemia as well
as methylenetetrahydrofolate reductase polymorphism are associated with affective psychoses.Prog.Neuropsychop-harmacol.Biol.Psychiatry2005;29:1162–1168.
15.Tolmunen T,Hintikka J,Voutilainen S et al.Association
between depressive symptoms and serum concentrations of homocysteine in men:A population study.Am.J.Clin.
Nutr.2004;80:1574–1578.
16.Reynolds E.Vitamin B12,folic acid,and the nervous
https://www.360docs.net/doc/d77659658.html,ncet Neurol.2006;5:949–960.
17.Mennen LI,Potier de Courcy G,Guilland JC et al.
Homocysteine,cardiovascular disease risk factors,and habitual diet in the French Supplementation with Antioxi-dant Vitamins and Minerals Study.Am.J.Clin.Nutr.2002;
76:1279–1289.
18.Ozbek Z,Kucukali CI,Ozkok E et al.Effect of the methyl-
enetetrahydrofolate reductase gene polymorphisms on homocysteine,folate and vitamin B12in patients with bipolar disorder and relatives.Prog.Neuropsychopharmacol.
Biol.Psychiatry2008;32:1331–1337.
19.Kunugi H,Fukuda R,Hattori M et al.C677T polymor-
phism in methylenetetrahydrofolate reductase gene and psychoses.Mol.Psychiatry1998;5:435–437.
20.Kempisty B,Mostowska A,Gorska I et al.Association of
677CNT polymorphism of methylenetetrahydrofolate reductase(MTHFR)gene with bipolar disorder and schizophrenia.Neurosci.Lett.2006;3:267–271.
21.Kempisty B,Bober A,Luczak M et al.Distribution of
1298ANC polymorphism of methylenetetrahydrofolate
reductase gene in patients with bipolar disorder and schizophrenia.Eur.Psychiatry2007;1:39–43.
22.Cohen-Woods S,Craig I,Gaysina D et al.The Bipolar
Association Case-Control Study(BACCS)and meta-analysis:No association with the5,10-methylenetetrahydrofolate reductase gene and bipolar disorder.Am.J.Med.Genet.B.2010;153B:1298–1304.
23.Gilbody S,Lewis S,Lightfoot T.Methylenetetrahydrofolate
reductase(MTHFR)genetic polymorphisms and psychiat-ric disorders:A HuGE review.Am.J.Epidemiol.2007;165: 1–13.
24.Zintzaras E.C677T and A1298C methylenetetrahydro-
folate reductase gene polymorphisms in schizophrenia, bipolar disorder and depression:A meta-analysis of genetic association studies.Psychiatr.Genet.2006;16: 105–115.
25.Peerbooms OLJ,Van Os J,Drukker M et al.Meta-analysis
of MTHFR gene variants in schizophrenia,bipolar disor-der and unipolar depressive disorder:Evidence for a common genetic vulnerability?Brain Behav.Immun.2011;
25:1530–1543.
26.Hasanah CI,Khan UA,Musalmah M et al.Reduced
red-cell folate in mania.J.Affect.Disord.1997;46:95–
99.
27.Ono H,Sakamoto A,Eguchi T et al.Plasma total homocys-
teine concentrations in epileptic patients taking anticon-vulsant.Metabolism1997;46:959–962.
28.Sener U,Zorlu Y,Karaguzel O et al.Effects of common
anti-epileptic drug monotherapy on serum levels of homocysteine,vitamin B12,folic acid and vitamin B6.
Seizure2006;15:79–85.
Psychiatry and Clinical Neurosciences2011;65:664–671Hyperhomocysteinemia in bipolar I patients671
?2011The Authors