J Neural Transm DOI 10.1007/s00702-014-1336-6
PSYCHIATRY AND PRECLINICAL PSYCHIATRIC STUDIES - SHORT COMMUNICATION
BDNF serum levels and promoter methylation of BDNF exon I, IV and VI in depressed patients receiving electroconvulsive therapy Alexandra Kleimann • Alexandra Kotsiari • Wolfgang Sperling • Michael Gro¨schl Annemarie Heberlein • Kai G. Kahl • Thomas Hillemacher • Stefan Bleich • Johannes Kornhuber • Helge Frieling
•
Received: 16 July 2014 / Accepted: 5 November 2014 Ó Springer-Verlag Wien 2014
Abstract We examined potential changes in brainderived neurotrophic factor (BDNF) serum levels and promoter methylation of the BDNF gene in 11 patients with treatment-resistant major depressive disorder during a series of electroconvulsive therapy (ECT). Blood samples were taken before, 1 and 24 h after ECT treatment sessions 1, 4, 7 and 10. Patients remitting under ECT had significantly lower mean promoter methylation rates, especially concerning the exon I promoter, compared to non-remitters (both p \ 0.002). These findings may point to a depression subtype in which ECT is particularly beneficial. Keywords Brain-derived neurotrophic factor Electroconvulsive therapy Treatment-resistant depression DNA methylation Promoter
Electronic supplementary material The online version of this article (doi:10.1007/s00702-014-1336-6) contains supplementary material, which is available to authorized users. A. Kleimann (&) A. Kotsiari A. Heberlein K. G. Kahl T. Hillemacher S. Bleich H. Frieling Laboratory for Molecular Neuroscience, Department of Psychiatry, Social Psychiatry and Psychotherapy, Hannover Medical School (MHH), Carl-Neubergstr. 1, 30625 Hannover, Germany e-mail: [email protected] W. Sperling J. Kornhuber Department of Psychiatry and Psychotherapy, FriedrichAlexander-University Erlangen-Nuremberg, Maximiliansplatz 2, 91054 Erlangen, Germany M. Gro¨schl Bioanalytical Laboratory, Celerion Switzerland AG, Allmendstr. 32, 8320 Fehraltorf, Switzerland
Introduction Electroconvulsive therapy (ECT) belongs to the most effective treatment options for refractory depressed patients, but its mechanisms still remain elusive (Lisanby 2007). In rodents, treatment with electroconvulsive stimulation (ECS) has been shown to increase hippocampal brainderived neurotrophic factor (BDNF) levels (Nibuya et al. 1995). As several lines of evidence have linked BDNF to the pathophysiology and pharmacotherapy of depression, this increase has been interpreted as a possible therapeutic effect of ECT. Nevertheless, studies in humans led to contradicting results concerning peripheral BDNF levels after ECT (Marano et al. 2007; Gedge et al. 2012). The complex regulation of BDNF expression underlies epigenetic mechanisms, such as histone modification and DNA methylation. Fuchikami et al. (2011) were able to distinguish between healthy controls and depressed patients through analysis of BDNF exon I methylation profiles. Furthermore, we could show in our previous study that the methylation status of a single Cytosine–phosphatidyl–Guanine (CpG) site within the promoter region of BDNF exon IV, predicts antidepressant treatment response (Tadic et al. 2014). Regarding epigenetic alterations within the BDNF gene through ECT, the only study published so far indicated that chronic upregulation of BDNF transcription within the rat hippocampus after chronic ECS may be mediated through histone3 acetylation (Tsankova et al. 2004). The purpose of our study was to investigate (1) whether the promoter methylation of BDNF exon I, IV and VI are changed in depressed patients during a series of ECT and (2) whether there is an association between serum levels of BDNF and the investigated changes in the methylation of the CpG sites.
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Materials and methods Patients and treatment We conducted a prospective study, including eleven patients suffering from treatment-resistant major depressive disorder (MDD). Diagnoses were established using the German version of the Structured Clinical Interview for DSM IV diagnoses. Depression severity was assessed before and 24 h after ECT treatment session 1, 4, 7 and 10 using the Montgomery Asberg Depression Scale (MADRS) and the German version of the Beck´s Depression Inventory (BDI-II) (Montgomery and Asberg 1979; Hautzinger et al. 2006). A 50 % reduction of the MADRS score was interpreted as response to therapy, a MADRS Score B12 as remission. ECT was applied as common practice in the facility with a customised Thymatron IV brief-pulse device (Somatics; Lake Bluff, IL, USA). Motor and electro-encephalogram seizure duration was monitored and stimulus intensity was adjusted accordingly. Three ECT sessions/week were applied over 3, 5 weeks. The study adhered to the Declaration of Helsinki (1964) and its later amendments. It was approved by the Ethics Committee of the University of Erlangen. Written informed consent was obtained from all patients after the procedures had been fully explained to them and prior to their inclusion in the study. All patients were recruited as in-patients at the Department of Psychiatry and Psychotherapy of the University Hospital Erlangen. BDNF serum levels Fasting blood samples were taken directly before (8–10 a.m.), 1 and 24 h after ECT sessions 1, 4, 7 and 10. All blood samples were stored at -80 °C immediately after collection (and centrifugation in case of serum samples). BDNF serum levels were assessed using the DuoSet enzyme-linked immunosorbent assay Development System (DY248, DY212 E, R&D Systems, Wiesbaden-Nordenstadt, Germany). All the assays were performed according to the manufacturer’s description. The lower limit of determination was 21 pg/mL BDNF. The intraassay and interassay coefficient of variation were 5.0 and 8.7 %. Bisulfite-sequencing of BDNF promoter I, IV and VI Genomic DNA was extracted with the QIAamp DNA Blood Mini Kit (QIAGEN GmbH, Hilden, Germany) from whole EDTA blood according to the manufacturer’s protocol. Genomic DNA was then modified with sodium bisulfite to deaminate unmethylated cytosines to uracils using the
123
EpiTect Bisulfite Kit (QIAGEN). Primers were designed to amplify CpG-rich regions in the promoters of BDNF exon I, IV and VI as shown in Online Resource 1. For amplification of the products semi-nested PCR was performed. After purification of the PCR product using Agencourt AMPure XP (Beckman Coulter GmbH, Krefeld, Germany) each product was visualised on a standard 2.0 % agarose gel. Sequencing in reverse direction was performed with a maximum of 30 ng of purified PCR product using the BigDye Terminator v3.1 Cycle Sequencing Kit (Life Technologies, Foster City, CA, USA) and, after purification with Agencourt CleanSEQ (Beckman Coulter), with the 3500xL Genetic Analyzer (Life Technologies) according to the manufacturer’s instructions. Statistical analysis The methylation of each CpG-site in the CpG-islands of all three BDNF promoters was assessed using the ESME computer program, which compares each methylation site to the original sequence of the promoter. For methylation analysis, mixed linear models for repeated measurements were performed including the factors age and body mass index (BMI), as they had an impact on the mean methylation levels of all three investigated promoters. The same procedure was used for analysis of the BDNF serum levels. For normally distributed parameters (Kolmogorov–Smirnov test) Pearson’s test was used, for not normally distributed data Spearman´s Rho test was used. Results are presented as mean ± SD. P values of less than 0.05 (two tailed) were considered to indicate statistical significance. Data were analysed employing IBM SPSS Statistics for Windows, Version 21.0. (Armonk, NY: IBM Corp.). Data are presented using Graph Pad Prism 5 (Graph Pad Inc., San Diego, CA).
Results Patients´ baseline characteristics are shown in Table 1. At the end of the ECT series four patients were in remission and six patients had responded to ECT. Remitters had a significantly lower mean methylation rate compared to nonremitters (p = 0.002). Additionally, also responders had a lower mean promoter methylation rate compared to nonresponders (p = 0.002). Analysis of the individual promoter methylation rates revealed that this effect is mainly driven by the promoter methylation of exon I, which was significantly lower in remitters/responders than in nonremitters/non-responders as shown in Fig. 1a. Patients´ BDNF levels negatively correlated with the mean methylation rate of all promoters (p = 0.03). This correlation could not be found when analysed for each promoter (exon
BDNF serum levels and promoter methylation of BDNF exon I, IV and VI Table 1 Patients´ characteristics at baseline
A
Characteristics, mean (SD) Age, years Women, n (%) Body mass index MADRS BDI
47 (16.5) 5 (45.5) 27 (3.5) 34 (8.3) 35.5 (10.2)
Duration of current depressive episode, weeks
20 (27.3)
Age at initial diagnosis, years
38 (14.1)
Number of previous depressive episodes
5 (2.7)
Psychotic symptoms, n (%)
8 (73)
History of suicide attempt, n (%) Antidepressants, n (%) Atypical antipsychotics, n (%)
2 (18) 10 (91) 9 (82)
I, IV and VI). Furthermore BDNF serum levels correlated with patients´ BDI scores (p = 0.008), but not with patients MADRS scores (p = 0.062). We did not find any correlation between patients´ BDNF serum levels and outcome (p = 0.37). BDNF serum levels are shown in Fig. 1b. There was no significant change in the methylation rates of all investigated BDNF promoters or the BDNF serum levels concerning the different time points (before, 1 and 24 h after ECT) or different ECT sessions (1, 4, 7 and 10).
B
Discussion The aim of the present study was to further investigate the role of BDNF in ECT. We studied acute and chronic effects of ECT on BDNF serum levels and, for the first time, on methylation of BDNF promoter I, IV, VI. The major finding of the study is the difference in the mean methylation between remitters/responders and nonremitters/non-responders, which was present over the whole ECT time course. Interestingly, the observed difference in methylation was mainly driven by the methylation rate of BDNF exon I promoter, which has been suggested as a biomarker able to distinguish between healthy and depressed subjects (Fuchikami et al. 2011). Our findings indicate that methylation of the BDNF exon I promoter could be a biomarker for therapy response to ECT, as it may point to a subgroup of depressed patients sensitive to ECT. Our data do not indicate acute or chronic peripheral methylation changes in the BDNF gene caused by ECT. Though DNA methylation varies between-tissues, it is important to note that some inter-individual variations have been shown to be reflected across brain and blood in humans (Davies et al. 2012). The negative correlation of mean methylation and BDNF serum levels is in line with previously reported data
Fig. 1 a BDNF promoter exon I methylation levels of remitters versus non-remitters a shows the BDNF promoter exon I mean methylation levels of remitters versus non-remitters at the different ECT sessions. Mixed linear modelling showed significantly lower methylation rates in remitters than non-remitters. The p value given in the figure is derived from mixed linear modelling (** p = 0.002). Error bars show the standard error of the mean (SEM). b BDNF serum levels of remitters versus non-remitters b shows BDNF serum levels of remitters versus non-remitters at the different ECT sessions. Mixed linear modelling showed no difference in serum levels between remitters and non-remitters. The p value given in the figure is derived from mixed linear modelling (p = 0.37). Error bars show the standard error of the mean (SEM)
on the epigenetic regulation of the BDNF gene (Boulle et al. 2012). We might have not found a correlation between each promoter and peripheral BDNF levels as we did not differentiate for different BDNF subspecies. We also did not find a change in BDNF expression over time, though a recent meta-analysis reported the increase of BDNF after ECT (Brunoni et al. 2014). The lack of increase in our sample could be related to its small size.
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Second, most patients were treated with antidepressants, which are known to increase BDNF levels (Boulle et al. 2012). Third, previous studies have varied in the time point at which post-treatment BDNF levels were measured. Up to now it is not clear if the increase of peripheral BDNF levels reflects a therapeutic effect of ECT, as Brunoni et al. reported a lack of correlation between BDNF increase and depression improvement after ECT. Taken together our study indicates that BDNF exon I promoter methylation could be a target of particular interest for future studies on predictive biomarkers for therapy response to ECT. The major limitation of our study is the small sample size and the investigation in medicated patients. Therefore, our results have to be regarded as preliminary and replications in larger, preferably unmedicated, populations are necessary to corroborate our result. Acknowledgments This work was supported by in-house research funds of the University of Erlangen and the Hannover Medical School. We gratefully acknowledge the help of Maike Peters in the recruitment of patients. We are thankful to all participants of this study and to our cooperating clinical and research partners. Conflict of interest of interest.
The authors declare that they have no conflict
References Boulle F, van den Hove DL, Jakob SB, Rutten BP, Hamon M, van Os J, Lesch KP, Lanfumey L, Steinbusch HW, Kenis G (2012) Epigenetic regulation of the BDNF gene: implications for psychiatric disorders. Mol Psychiatry 17:584–596 Brunoni AR, Baeken C, Machado-Vieira R, Gattaz WF, Vanderhasselt MA (2014) BDNF blood levels after electroconvulsive
123
therapy in patients with mood disorders: a systematic review and meta-analysis. World J Biol Psychiatry 15:411–418 Davies MN, Volta M, Pidsley R, Lunnon K, Dixit A, Lovestone S, Coarfa C, Harris RA, Milosavljevic A, Troakes C, Al-Sarraj S, Dobson R, Schalkwyk LC, Mill J (2012) Functional annotation of the human brain methylome identifies tissue-specific epigenetic variation across brain and blood. Genome Biol 13(6):R43. doi:10.1186/gb-2012-13-6-r43 Fuchikami M, Morinobu S, Segawa M, Okamoto Y, Yamawaki S, Ozaki N, Inoue T, Kusumi I, Koyama T, Tsuchiyama K, Terao T (2011) DNA methylation profiles of the brain-derived neurotrophic factor (BDNF) gene as a potent diagnostic biomarker in major depression. PLoS One 6:e23881 Gedge L, Beaudoin A, Lazowski L, du Toit R, Jokic R, Milev R (2012) Effects of electroconvulsive therapy and repetitive transcranial magnetic stimulation on serum brain-derived neurotrophic factor levels in patients with depression. Front Psychiatry 3:12 Hautzinger M, Keller F, Ku¨hner C (2006) Beck-Depressions-Inventar BDI-II; manual. Harcourt Test Services, Frankfurt am Main Lisanby SH (2007) Electroconvulsive therapy for depression. N Engl J Med 357:1939–1945 Marano CM, Phatak P, Vemulapalli UR, Sasan A, Nalbandyan MR, Ramanujam S, Soekadar S, Demosthenous M, Regenold WT (2007) Increased plasma concentration of brain-derived neurotrophic factor with electroconvulsive therapy: a pilot study in patients with major depression. J Clin Psychiatry 68:512–517 Montgomery SA, Asberg M (1979) A new depression scale designed to be sensitive to change. Br J Psychiatry 134:382–389 Nibuya M, Morinobu S, Duman RS (1995) Regulation of BDNF and trkB mRNA in rat brain by chronic electroconvulsive seizure and antidepressant drug treatments. J Neurosci 15:7539–7547 Tadic A, Muller-Engling L, Schlicht KF, Kotsiari A, Dreimuller N, Kleimann A, Bleich S, Lieb K, Frieling H (2014) Methylation of the promoter of brain-derived neurotrophic factor exon IV and antidepressant response in major depression. Mol Psychiatry 19:281–283 Tsankova NM, Kumar A, Nestler EJ (2004) Histone modifications at gene promoter regions in rat hippocampus after acute and chronic electroconvulsive seizures. J Neurosci 24:5603–5610
PSYCHIATRY AND PRECLINICAL PSYCHIATRIC STUDIES - SHORT COMMUNICATION
BDNF serum levels and promoter methylation of BDNF exon I, IV and VI in depressed patients receiving electroconvulsive therapy Alexandra Kleimann • Alexandra Kotsiari • Wolfgang Sperling • Michael Gro¨schl Annemarie Heberlein • Kai G. Kahl • Thomas Hillemacher • Stefan Bleich • Johannes Kornhuber • Helge Frieling
•
Received: 16 July 2014 / Accepted: 5 November 2014 Ó Springer-Verlag Wien 2014
Abstract We examined potential changes in brainderived neurotrophic factor (BDNF) serum levels and promoter methylation of the BDNF gene in 11 patients with treatment-resistant major depressive disorder during a series of electroconvulsive therapy (ECT). Blood samples were taken before, 1 and 24 h after ECT treatment sessions 1, 4, 7 and 10. Patients remitting under ECT had significantly lower mean promoter methylation rates, especially concerning the exon I promoter, compared to non-remitters (both p \ 0.002). These findings may point to a depression subtype in which ECT is particularly beneficial. Keywords Brain-derived neurotrophic factor Electroconvulsive therapy Treatment-resistant depression DNA methylation Promoter
Electronic supplementary material The online version of this article (doi:10.1007/s00702-014-1336-6) contains supplementary material, which is available to authorized users. A. Kleimann (&) A. Kotsiari A. Heberlein K. G. Kahl T. Hillemacher S. Bleich H. Frieling Laboratory for Molecular Neuroscience, Department of Psychiatry, Social Psychiatry and Psychotherapy, Hannover Medical School (MHH), Carl-Neubergstr. 1, 30625 Hannover, Germany e-mail: [email protected] W. Sperling J. Kornhuber Department of Psychiatry and Psychotherapy, FriedrichAlexander-University Erlangen-Nuremberg, Maximiliansplatz 2, 91054 Erlangen, Germany M. Gro¨schl Bioanalytical Laboratory, Celerion Switzerland AG, Allmendstr. 32, 8320 Fehraltorf, Switzerland
Introduction Electroconvulsive therapy (ECT) belongs to the most effective treatment options for refractory depressed patients, but its mechanisms still remain elusive (Lisanby 2007). In rodents, treatment with electroconvulsive stimulation (ECS) has been shown to increase hippocampal brainderived neurotrophic factor (BDNF) levels (Nibuya et al. 1995). As several lines of evidence have linked BDNF to the pathophysiology and pharmacotherapy of depression, this increase has been interpreted as a possible therapeutic effect of ECT. Nevertheless, studies in humans led to contradicting results concerning peripheral BDNF levels after ECT (Marano et al. 2007; Gedge et al. 2012). The complex regulation of BDNF expression underlies epigenetic mechanisms, such as histone modification and DNA methylation. Fuchikami et al. (2011) were able to distinguish between healthy controls and depressed patients through analysis of BDNF exon I methylation profiles. Furthermore, we could show in our previous study that the methylation status of a single Cytosine–phosphatidyl–Guanine (CpG) site within the promoter region of BDNF exon IV, predicts antidepressant treatment response (Tadic et al. 2014). Regarding epigenetic alterations within the BDNF gene through ECT, the only study published so far indicated that chronic upregulation of BDNF transcription within the rat hippocampus after chronic ECS may be mediated through histone3 acetylation (Tsankova et al. 2004). The purpose of our study was to investigate (1) whether the promoter methylation of BDNF exon I, IV and VI are changed in depressed patients during a series of ECT and (2) whether there is an association between serum levels of BDNF and the investigated changes in the methylation of the CpG sites.
123
A. Kleimann et al.
Materials and methods Patients and treatment We conducted a prospective study, including eleven patients suffering from treatment-resistant major depressive disorder (MDD). Diagnoses were established using the German version of the Structured Clinical Interview for DSM IV diagnoses. Depression severity was assessed before and 24 h after ECT treatment session 1, 4, 7 and 10 using the Montgomery Asberg Depression Scale (MADRS) and the German version of the Beck´s Depression Inventory (BDI-II) (Montgomery and Asberg 1979; Hautzinger et al. 2006). A 50 % reduction of the MADRS score was interpreted as response to therapy, a MADRS Score B12 as remission. ECT was applied as common practice in the facility with a customised Thymatron IV brief-pulse device (Somatics; Lake Bluff, IL, USA). Motor and electro-encephalogram seizure duration was monitored and stimulus intensity was adjusted accordingly. Three ECT sessions/week were applied over 3, 5 weeks. The study adhered to the Declaration of Helsinki (1964) and its later amendments. It was approved by the Ethics Committee of the University of Erlangen. Written informed consent was obtained from all patients after the procedures had been fully explained to them and prior to their inclusion in the study. All patients were recruited as in-patients at the Department of Psychiatry and Psychotherapy of the University Hospital Erlangen. BDNF serum levels Fasting blood samples were taken directly before (8–10 a.m.), 1 and 24 h after ECT sessions 1, 4, 7 and 10. All blood samples were stored at -80 °C immediately after collection (and centrifugation in case of serum samples). BDNF serum levels were assessed using the DuoSet enzyme-linked immunosorbent assay Development System (DY248, DY212 E, R&D Systems, Wiesbaden-Nordenstadt, Germany). All the assays were performed according to the manufacturer’s description. The lower limit of determination was 21 pg/mL BDNF. The intraassay and interassay coefficient of variation were 5.0 and 8.7 %. Bisulfite-sequencing of BDNF promoter I, IV and VI Genomic DNA was extracted with the QIAamp DNA Blood Mini Kit (QIAGEN GmbH, Hilden, Germany) from whole EDTA blood according to the manufacturer’s protocol. Genomic DNA was then modified with sodium bisulfite to deaminate unmethylated cytosines to uracils using the
123
EpiTect Bisulfite Kit (QIAGEN). Primers were designed to amplify CpG-rich regions in the promoters of BDNF exon I, IV and VI as shown in Online Resource 1. For amplification of the products semi-nested PCR was performed. After purification of the PCR product using Agencourt AMPure XP (Beckman Coulter GmbH, Krefeld, Germany) each product was visualised on a standard 2.0 % agarose gel. Sequencing in reverse direction was performed with a maximum of 30 ng of purified PCR product using the BigDye Terminator v3.1 Cycle Sequencing Kit (Life Technologies, Foster City, CA, USA) and, after purification with Agencourt CleanSEQ (Beckman Coulter), with the 3500xL Genetic Analyzer (Life Technologies) according to the manufacturer’s instructions. Statistical analysis The methylation of each CpG-site in the CpG-islands of all three BDNF promoters was assessed using the ESME computer program, which compares each methylation site to the original sequence of the promoter. For methylation analysis, mixed linear models for repeated measurements were performed including the factors age and body mass index (BMI), as they had an impact on the mean methylation levels of all three investigated promoters. The same procedure was used for analysis of the BDNF serum levels. For normally distributed parameters (Kolmogorov–Smirnov test) Pearson’s test was used, for not normally distributed data Spearman´s Rho test was used. Results are presented as mean ± SD. P values of less than 0.05 (two tailed) were considered to indicate statistical significance. Data were analysed employing IBM SPSS Statistics for Windows, Version 21.0. (Armonk, NY: IBM Corp.). Data are presented using Graph Pad Prism 5 (Graph Pad Inc., San Diego, CA).
Results Patients´ baseline characteristics are shown in Table 1. At the end of the ECT series four patients were in remission and six patients had responded to ECT. Remitters had a significantly lower mean methylation rate compared to nonremitters (p = 0.002). Additionally, also responders had a lower mean promoter methylation rate compared to nonresponders (p = 0.002). Analysis of the individual promoter methylation rates revealed that this effect is mainly driven by the promoter methylation of exon I, which was significantly lower in remitters/responders than in nonremitters/non-responders as shown in Fig. 1a. Patients´ BDNF levels negatively correlated with the mean methylation rate of all promoters (p = 0.03). This correlation could not be found when analysed for each promoter (exon
BDNF serum levels and promoter methylation of BDNF exon I, IV and VI Table 1 Patients´ characteristics at baseline
A
Characteristics, mean (SD) Age, years Women, n (%) Body mass index MADRS BDI
47 (16.5) 5 (45.5) 27 (3.5) 34 (8.3) 35.5 (10.2)
Duration of current depressive episode, weeks
20 (27.3)
Age at initial diagnosis, years
38 (14.1)
Number of previous depressive episodes
5 (2.7)
Psychotic symptoms, n (%)
8 (73)
History of suicide attempt, n (%) Antidepressants, n (%) Atypical antipsychotics, n (%)
2 (18) 10 (91) 9 (82)
I, IV and VI). Furthermore BDNF serum levels correlated with patients´ BDI scores (p = 0.008), but not with patients MADRS scores (p = 0.062). We did not find any correlation between patients´ BDNF serum levels and outcome (p = 0.37). BDNF serum levels are shown in Fig. 1b. There was no significant change in the methylation rates of all investigated BDNF promoters or the BDNF serum levels concerning the different time points (before, 1 and 24 h after ECT) or different ECT sessions (1, 4, 7 and 10).
B
Discussion The aim of the present study was to further investigate the role of BDNF in ECT. We studied acute and chronic effects of ECT on BDNF serum levels and, for the first time, on methylation of BDNF promoter I, IV, VI. The major finding of the study is the difference in the mean methylation between remitters/responders and nonremitters/non-responders, which was present over the whole ECT time course. Interestingly, the observed difference in methylation was mainly driven by the methylation rate of BDNF exon I promoter, which has been suggested as a biomarker able to distinguish between healthy and depressed subjects (Fuchikami et al. 2011). Our findings indicate that methylation of the BDNF exon I promoter could be a biomarker for therapy response to ECT, as it may point to a subgroup of depressed patients sensitive to ECT. Our data do not indicate acute or chronic peripheral methylation changes in the BDNF gene caused by ECT. Though DNA methylation varies between-tissues, it is important to note that some inter-individual variations have been shown to be reflected across brain and blood in humans (Davies et al. 2012). The negative correlation of mean methylation and BDNF serum levels is in line with previously reported data
Fig. 1 a BDNF promoter exon I methylation levels of remitters versus non-remitters a shows the BDNF promoter exon I mean methylation levels of remitters versus non-remitters at the different ECT sessions. Mixed linear modelling showed significantly lower methylation rates in remitters than non-remitters. The p value given in the figure is derived from mixed linear modelling (** p = 0.002). Error bars show the standard error of the mean (SEM). b BDNF serum levels of remitters versus non-remitters b shows BDNF serum levels of remitters versus non-remitters at the different ECT sessions. Mixed linear modelling showed no difference in serum levels between remitters and non-remitters. The p value given in the figure is derived from mixed linear modelling (p = 0.37). Error bars show the standard error of the mean (SEM)
on the epigenetic regulation of the BDNF gene (Boulle et al. 2012). We might have not found a correlation between each promoter and peripheral BDNF levels as we did not differentiate for different BDNF subspecies. We also did not find a change in BDNF expression over time, though a recent meta-analysis reported the increase of BDNF after ECT (Brunoni et al. 2014). The lack of increase in our sample could be related to its small size.
123
A. Kleimann et al.
Second, most patients were treated with antidepressants, which are known to increase BDNF levels (Boulle et al. 2012). Third, previous studies have varied in the time point at which post-treatment BDNF levels were measured. Up to now it is not clear if the increase of peripheral BDNF levels reflects a therapeutic effect of ECT, as Brunoni et al. reported a lack of correlation between BDNF increase and depression improvement after ECT. Taken together our study indicates that BDNF exon I promoter methylation could be a target of particular interest for future studies on predictive biomarkers for therapy response to ECT. The major limitation of our study is the small sample size and the investigation in medicated patients. Therefore, our results have to be regarded as preliminary and replications in larger, preferably unmedicated, populations are necessary to corroborate our result. Acknowledgments This work was supported by in-house research funds of the University of Erlangen and the Hannover Medical School. We gratefully acknowledge the help of Maike Peters in the recruitment of patients. We are thankful to all participants of this study and to our cooperating clinical and research partners. Conflict of interest of interest.
The authors declare that they have no conflict
References Boulle F, van den Hove DL, Jakob SB, Rutten BP, Hamon M, van Os J, Lesch KP, Lanfumey L, Steinbusch HW, Kenis G (2012) Epigenetic regulation of the BDNF gene: implications for psychiatric disorders. Mol Psychiatry 17:584–596 Brunoni AR, Baeken C, Machado-Vieira R, Gattaz WF, Vanderhasselt MA (2014) BDNF blood levels after electroconvulsive
123
therapy in patients with mood disorders: a systematic review and meta-analysis. World J Biol Psychiatry 15:411–418 Davies MN, Volta M, Pidsley R, Lunnon K, Dixit A, Lovestone S, Coarfa C, Harris RA, Milosavljevic A, Troakes C, Al-Sarraj S, Dobson R, Schalkwyk LC, Mill J (2012) Functional annotation of the human brain methylome identifies tissue-specific epigenetic variation across brain and blood. Genome Biol 13(6):R43. doi:10.1186/gb-2012-13-6-r43 Fuchikami M, Morinobu S, Segawa M, Okamoto Y, Yamawaki S, Ozaki N, Inoue T, Kusumi I, Koyama T, Tsuchiyama K, Terao T (2011) DNA methylation profiles of the brain-derived neurotrophic factor (BDNF) gene as a potent diagnostic biomarker in major depression. PLoS One 6:e23881 Gedge L, Beaudoin A, Lazowski L, du Toit R, Jokic R, Milev R (2012) Effects of electroconvulsive therapy and repetitive transcranial magnetic stimulation on serum brain-derived neurotrophic factor levels in patients with depression. Front Psychiatry 3:12 Hautzinger M, Keller F, Ku¨hner C (2006) Beck-Depressions-Inventar BDI-II; manual. Harcourt Test Services, Frankfurt am Main Lisanby SH (2007) Electroconvulsive therapy for depression. N Engl J Med 357:1939–1945 Marano CM, Phatak P, Vemulapalli UR, Sasan A, Nalbandyan MR, Ramanujam S, Soekadar S, Demosthenous M, Regenold WT (2007) Increased plasma concentration of brain-derived neurotrophic factor with electroconvulsive therapy: a pilot study in patients with major depression. J Clin Psychiatry 68:512–517 Montgomery SA, Asberg M (1979) A new depression scale designed to be sensitive to change. Br J Psychiatry 134:382–389 Nibuya M, Morinobu S, Duman RS (1995) Regulation of BDNF and trkB mRNA in rat brain by chronic electroconvulsive seizure and antidepressant drug treatments. J Neurosci 15:7539–7547 Tadic A, Muller-Engling L, Schlicht KF, Kotsiari A, Dreimuller N, Kleimann A, Bleich S, Lieb K, Frieling H (2014) Methylation of the promoter of brain-derived neurotrophic factor exon IV and antidepressant response in major depression. Mol Psychiatry 19:281–283 Tsankova NM, Kumar A, Nestler EJ (2004) Histone modifications at gene promoter regions in rat hippocampus after acute and chronic electroconvulsive seizures. J Neurosci 24:5603–5610
