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group to cytosine residues in the dinucleotide sequence CpG.1 A lack of alimentary methyl-group donors, like folate, owing to starvation, may be the underlying cause of both elevated homocysteine and DNA hypomethylation in AN. To further investigate possible epigenetic contributions to the pathophysiology of eating disorders, we analyzed the expression and promoter-specific DNA methylation of two genes, SNCA and HERP, recently described to be altered in alcohol dependence.5,7 We found a decreased SNCA expression in patients with AN, which was associated with a DNA hypermethylation of the SNCA promoter. Although showing a decreased expression of SNCA, we failed to find hypermethylation in the BN groups possibly owing to a lack of power of the study, as there was a trend towards hypermethylation when compared to controls (t-test; P = 0.083), but this was lost after correction for multiple comparisons. The observation that unchanged promotermethylation of the HERP gene was associated with a gene expression comparable to that in the control group may suggest that normal patterns of DNA methylation can be kept constant in the promoter regions of certain genes despite a potential lack of methyl groups. In conclusion, we found alterations of epigenetic DNA methylation in females with AN. These findings need to be replicated in a larger sample and different genes should be analyzed, and different methods of analyzing methylation patterns of the DNA should be applied. The restriction enzyme-based approach that we have chosen has some disadvantages when compared to bisulfite sequencing methods, mainly the limitation of analysis to one CpG element in the promoter and the need for reliable digestion results. Longitudinal observations, comparing acute illness with the situation after refeeding and recovery, are warranted. Profound knowledge of the epigenetics of eating disorders may help in understanding the gene– environment nexus postulated for the disorder. H Frieling1, A Gozner1, KD Ro¨mer1, B Lenz1, D Bo¨nsch1, J Wilhelm1, T Hillemacher1, M de Zwaan2, J Kornhuber1 and S Bleich1 1 Department of Psychiatry and Psychotherapy, University Erlangen-Nuremberg, Erlangen, Germany and 2Department of Psychosomatic Medicine and Psychotherapy, University Erlangen-Nuremberg, Erlangen, Germany E-mail:
[email protected]
References 1 Rodenhiser D, Mann M. CMAJ 2006; 174: 341–348. 2 Abdolmaleky HM, Smith CL, Faraone SV, Shafa R, Stone W, Glatt SJ et al. Am J Med Genet B Neuropsychiatr Genet 2004; 127: 51–59. 3 Szyf M, Weaver ICG, Champagne FA, Diorio J, Meaney MJ. Front Neuroendocrinol 2005; 26: 139–162. 4 Tsankova NM, Berton O, Renthal W, Kumar A, Neve RL, Nestler EJ. Nat Neurosci 2006; 9: 519–525. 5 Bleich S, Lenz B, Ziegenbein M, Beutler S, Frieling H, Kornhuber J et al. Alcohol Clin Exp Res 2006; 30: 587–591. Molecular Psychiatry
6 Frieling H, Ro¨mer KD, Ro¨schke B, Bo¨nsch D, Wilhelm J, Fiszer R et al. J Neural Transm 2005; 112: 979–985. 7 Bo¨nsch D, Lenz B, Kornhuber J, Bleich S. Neuroreport 2005; 16: 167–170. 8 Yi P, Melnyk S, Pogribna M, Pogribny IP, Hine RJ, James SJ. J Biol Chem 2000; 275: 29318–29323.
Val66met polymorphism and serum brain-derived neurotrophic factor levels in bipolar disorder Molecular Psychiatry (2007) 12, 230–231. doi:10.1038/sj.mp.4001941
There is strong evidence demonstrating that genetic inheritance is associated with higher susceptibility to bipolar disorder (BD), but the interaction between gene polymorphisms and biochemical changes remains largely unknown. A common polymorphism in the brain-derived neurotrophic factor (BDNF) gene, which substitutes a valine for a methionine at the codon 66 (val66met) has been implicated to play a role in BD.1 Specifically, the BDNF val66met polymorphism is associated with susceptibility to rapid cycling2 and altered cognitive performance in BD subjects.3 Our group has recently reported that serum BDNF levels are decreased during acute manic and depressive episodes in BD patients, suggesting that the regulation of BDNF might be implicated in mood stabilization.4 Considering that the val66met polymorphism affects intracellular packaging and activitydependent secretion of BDNF,5 and that there is a strong positive correlation between brain and serum BDNF levels,6 we have investigated whether the val66met polymorphism is associated with changes in serum BDNF levels in BD patients and normal controls. We hypothesized a priori that met carriers (met/met þ val/met genotypes) would present lower levels of serum BDNF than the val/val group. One hundred and seven Caucasian type-I bipolar patients were recruited from the Bipolar Disorders Program (Hospital de Clinicas de Porto Alegre, Brazil). Psychiatric diagnoses were carried out using the Structured Clinical Interview for DSM-IV-Axis I, and manic and depressive symptoms were assessed using the Young Mania Rating Scale (YMRS) and the Hamilton Depression Rating Scale (HDRS), respectively. One hundred and thirty-seven healthy controls were matched by age, gender and education. Control subjects were non-smokers, were not on medication and had no history of major psychiatric disorders, dementia, mental retardation, cancer or tumor and no such disorders in their first-degree relatives. Ten milliliters of blood were withdrawn from each subject
BDNF serum levels / ug protein
Letters to the Editor Bipolar Healthy Controls
0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Met/Met+Val/Met
Val/Val
Figure 1 Val66met polymorphism and serum BDNF levels in bipolar disorder patients and healthy controls (mean7s.e.m.).
by venipuncture into a free-anticoagulant vacuum tube for biochemical analyses and 5 ml into an ethylene diamine tetraacetic acid (EDTA) vacuum tube for DNA analyses. BDNF serum levels were measured using a commercial kit of sandwich-ELISA according to the manufacturer’s instruction (Chemicon, Temecula, CA, USA). The standard curve demonstrated a direct relationship between optical density and BDNF concentration. Total protein was measured by Lowry’s method using bovine serum albumin as a standard. The genomic DNA was extracted using standard procedures and the BDNF val66met polymorphism was genotyped according to Neves-Pereira et al.7 All the assays were performed blind to the subject’s status. There were no significant deviations of patients and control groups from Hardy–Weinberg equilibrium (P > 0.05; w2 test), and the prevalence of allele frequencies was consistent with those previously reported for the Caucasian population (bipolar patients: val/val = 73 (64%); val/met = 37 (32.5%); met/ met = 4 (3.5%); controls: val/val = 95 (69.3%); val/ met = 40 (29.2%); met/met = 2 (1.5%)). No significant differences were found in the frequency of the BDNF val66met genotype or allele distribution between patients and controls (P > 0.05; w2 test). We have found no significant interaction between BDNF polymorphism and diagnostic status (bipolar disorder and controls) on serum BDNF levels (P = 0.34; factorial analysis of variance; Figure 1), indicating that the BDNF val66met polymorphism does not affect serum BDNF levels in bipolar subjects and normal controls. Results were kept unchanged when YMRS and HDRS scores were controlled for.
Recent studies showed that serum BDNF levels are decreased during acute major mood episodes in BD4,8 and in major depressive disorder.9 In addition, the regulation of serum BDNF levels is negatively correlated to the severity of manic and depressive symptoms,4,8 and is associated with clinical response to antidepressant treatment,9 suggesting that peripheral BDNF measure could play a role as a neurobiological marker in major mood disorders. Here we demonstrate that the BDNF val66met polymorphism does not affect serum BDNF levels in a sample of mostly euthymic BD subjects (mean YMRS = 3.92; mean HDRS = 9.27). Considering that the BDNFmet variant decreases only the activity-dependent but not the constitutive BDNF secretion,5,10 it is possible that this polymorphism may exert some influence on serum BDNF levels during acute mood episodes.
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J Tramontina1,2, BN Frey2,3, AC Andreazza2,3, M Zandona4, A Santin2 and F Kapczinski1,2,3 1 Programa de Po´s-Graduac¸a˜o em Cieˆncias Me´dicas: Psiquiatria, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil; 2Programa de Transtorno Bipolar, Centro de Pesquisas, Hospital de Clı´nicas de Porto Alegre, Porto Alegre, RS, Brazil; 3Departamento de Bioquı´mica, Instituto de Cieˆncias Ba´sicas da Sau´de, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil and 4Departamento de Gene´tica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil E-mail:
[email protected]
References 1 Craddock N, O’Donovan MC, Owen MJ. J Med Genet 2005; 42: 193–204. 2 Green EK, Raybould R, Macgregor S, Hyde S, Young AH, O’Donovan MC et al. Br J Psychiatry 2006; 188: 21–25. 3 Rybakowski JK, Borkowska A, Skibinska M, Hauser J. Mol Psychiatry 2006; 11: 122–124. 4 Cunha ABM, Frey BN, Andreazza AC, Goi JD, Rosa AR, Goncalves CA et al. Neurosci Lett 2006; 398: 215–219. 5 Chen ZY, Patel PD, Sant G, Meng C-X, Teng KK, Hempstead BL et al. J Neurosci 2004; 24: 4401–4411. 6 Karege F, Schwald M, Cissc M. Neurosci Lett 2002; 328: 261–264. 7 Neves-Pereira M, Mundo E, Muglia P, King N, Macciardi F, Kennedy JL. Am J Hum Genet 2002; 71: 651–665. 8 Machado-Vieira R, Dietrich MO, Leke R, Cerescr VH, Zanatto V, Kapczinski F et al. Biol Psychiatry, in press. 9 Gonul AS, Akdeniz F, Taneli F, Donat O, Eker C, Vahip S. Eur Arch Psychiatry Clin Neurosci 2005; 255: 381–386. 10 Egan MF, Kojima M, Callicott JH, Goldberg TE, Kolachana BS, Bertolino A et al. Cell 2003; 112: 257–269.
Molecular Psychiatry
