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BDNF A196G and C270T gene polymorphisms and susceptibility to multiple sclerosis in the polish population. Gender differences
Journal of Neuroimmunology 193 (2008) 170 – 172 www.elsevier.com/locate/jneuroim
Short communication
BDNF A196G and C270T gene polymorphisms and susceptibility to multiple sclerosis in the polish population. Gender differences Dagmara Mirowska-Guzel a,b , Anna Mach a , Grazyna Gromadzka a,b , Andrzej Czlonkowski b , Anna Czlonkowska a,b,⁎ b
a 2nd Department of Neurology, Institute of Psychiatry and Neurology, Sobieskiego 9, 02-957 Warsaw, Poland Department of Clinical and Experimental Pharmacology, Medical University of Warsaw, Krakowskie Przedmiescie 26/28, 00-297 Warsaw, Poland
Received 19 July 2007; received in revised form 17 October 2007; accepted 17 October 2007
Abstract Two single nucleotide polymorphisms of the human BDNF gene, G196A and C270T, and their impact on the susceptibility to MS and disease progression in the Polish population were investigated. Increased risk of the disease was found for 196G/G carriers (OR — 1.63, p = 0.01) (only females) and 270C/T carriers (OR — 7.76, p b 0.001) (both males and females). The first signs of the disease appeared earlier in 196G/G than 196G/A patients (p = 0.01), but it was limited to males. Our results show that C270T and G196A BDNF polymorphisms may affect susceptibility to and onset of MS, but further verification is needed, with special attention to gender differences. © 2007 Elsevier B.V. All rights reserved. Keywords: Multiple sclerosis; BDNF; Gender differences
1. Introduction
2. Subjects
Multiple sclerosis (MS) pathogenesis is complex and still not fully understood. There is some evidence that disease develops in genetically predisposed individuals concurrent with environmental factors (Oksenberg and Barcellos, 2000). It is suspected that genetic factors may also play an important role in the clinical course of the disease (Mycko et al., 2004). It has recently been proposed that neurodegeneration accompanies autoimmunity in MS subjects (Dhib-Jalbut et al., 2006), thus suggesting potential beneficial effect of neurotrophic factors such as brain-derived neurotrophic factors (BDNF), nerve growth factor (NGF) and neurotrophin-3 (NT-3). These factors are thought to contribute to neuronal survival, axonal and neuronal repair (Hohlfeld et al., 2000, Moalem et al., 2000) and remyelination (Rosenberg et al., 2006) and may serve as attractive candidate genes controlling MS disease characteristics.
230 patients (63 men and 167 women) with MS diagnosed according to the McDonald criteria (McDonald et al., 2001, Polman et al., 2005) and 177 unrelated, sex matched (63 males and 114 females) healthy controls (mean age of 40.09 ± 10.19) were included. Patients with relapsing–remitting (RR) and secondary-progressive (SP) disease courses were evaluated for onset of RRMS. Disease severity was estimated using EDSS (Kurtzke, 1983) and progression index (PI: EDSS/disease duration). Patient demographics are presented in Table 1. A single sample of peripheral blood (2.7 ml) was collected from all subjects after obtaining written informed consent. The study protocol was approved by the Local Hospital Ethics Committee.
⁎ Corresponding author. 2nd Department of Neurology, Institute of Psychiatry and Neurology, Sobieskiego 9, 02-957 Warsaw, Poland. Tel.: +48 22 842 76 83; fax: +48 22 842 40 23. E-mail address: [email protected] (A. Czlonkowska). 0165-5728/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jneuroim.2007.10.013
3. Methods Genomic DNA was isolated with Tri-Reagent (SIGMA, Poland). BDNF C270T and G196A (G758A) genotyping was performed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP), as described previously ( Riemenschneider et al., 2002; Neves-Pereira et al., 2002).
D. Mirowska-Guzel et al. / Journal of Neuroimmunology 193 (2008) 170–172
171
Table 2 BDNF 196 and 270 genotype frequencies in MS and control subjects
4. Statistical analysis Statistical analysis was performed with Statistica PL version 7.1 (StatSoft® Poland, 2006). Genotype and allele frequencies were compared using the chi-square test. p ≤ 0.05 was considered as statistically significant. For multiple comparisons, the Bonferroni correction was used with a significant p value being b0.0125. Continuous data were compared using the Mann Whitney Test. A multiple logistic regression model expressed as an adjusted odds ratio (OR) and a 95% confidence interval (95% CI) was applied for the measurement of strength of association between genetic polymorphisms and MS.
MS patients Controls n (%) n (%)
pa value⁎
Odds ratio (95%CI)
BDNF gene polymorphisms genotypes 196 G/G 139 (60) 83 (47) 0.0065 196 G/A 89 (40) 94 (53) 0.0038 270 C/C 157 (68) 167 (94) b0.0001 270 C/T 73 (32) 10 (6) b0.0001 196 G/A 73 (32) 91 (51) 0.0001 and 270C/C 196 G/G 58 (25) 8 (4.5) b0.0001 and 270 C/T
pb value⁎
1.63 (1.11–2.41) 0.0129 0.61 (0.41–0.90) 0.0129 0.13 (0.06–0.26) b0.0001 7.76 (3.86–15.61) b0.0001 0.14 (0.06–0.30) b0.00001 7.12 (3.29–15.41) b0.00001
pa counted with chi-square test. pb counted with logistic regression analysis. ⁎ p value for significance after Bonferroni correction is 0.0125.
5. Results 5.1. Genotypes and susceptibility to MS We found an increased risk of susceptibility to MS for BDNF 196G/G (OR — 1.63, p = 0.0129) and for BDNF 270C/T (OR — 7.76, p b 0.0001). Combined effects of the 196G/G and 270C/T genotype in carriers significantly increased the risk of MS compared to non-carriers (OR — 7.12, p b 0.00001) (Table 2). 5.2. Gender, genotype and MS risk In males, the 270C/T genotype (C270T BDNF polymorphism) was associated with a significantly increased risk of MS (OR — 4.64, p = 0.0047, Table 3b), whereas the G196A BDNF polymorphism did not confer an increased risk of MS. In females, the same 270C/T genotype conferred a highly significant risk of MS (OR — 10.70, p b 0.00001, Table 3a), whereas the 196G/G genotype was associated with a less pronounced but still significantly increased risk of MS (OR — 1.69, p = 0.0298). 5.3. Genotypes and clinical parameters
This difference in age of onset was also evident in subjects who presented initially with RRMS (25 years of age in the 196G/G group versus 29 years of age in the 196G/A group (p = 0.019). In contrast, no difference in age of onset was noted in PPMS subjects with the C270T polymorphism. In sex-based analysis, disease onset occurred at 22 years of age in RRMS males with the 196G/G polymorphism versus 30 years of age in males with 196G/A (p = 0.012). There was also a border-line difference (p = 0.046) in the rate of progression in this group, with a progression index of 0.4 in males with the 196G/G genotype versus 0.6 in males with the 196G/A genotype. 6. Discussion Previous studies evaluating BDNF polymorphisms in MS focused on the G196A (Val66Met) polymorphism (Lindquist Table 3 BDNF 196 and 270 genotype frequencies in MS and control subjects by gender (a: females; b: males) a) MS females n (%)
In 196G/G subjects, the first signs of MS appeared at the age of 25, versus 30 years of age in 196G/A patients (p = 0.010). Table 1 Demographic and clinical characteristics of MS subjects All MS subjects RR, n = 187 (n = 230) (82%) Female/male Age (mean ± SD)
167/63 38.11 ± 10.94
Age of onset (mean ± SD) Age of diagnosis (mean ± SD) Disease duration (mean ± SD) Median EDSS (range) Progression index (mean ± SD)
29.18 ± 9.98 31.80 ± 10.75 9.04 ± 8.25 3.5 (0.0–8.5) 0.83 ± 0.96
138/49 36.10 ± 9.79
SP, n = 30 (13%)
PP, n = 13 (5%)
21/9 8/5 46.83 ± 12.28 46.61 ± 10.19 28.33 ± 9.63 30.55 ± 9.94 37.54 ± 11.27 31.10 ± 10.71 32.72 ± 9.38 39.54 ± 11.66 7.96 ± 7.06 15.72 ± 11.69 8.70 ± 7.94 3.0 (0.0–8.5) 7.0 (3.0–9.0) 4.0 (1.5–7.0) 0.81 ± 0.97 0.68 ± 0.52 1.29 ± 1.40
Control females n (%)
pa value⁎
BDNF gene polymorphisms genotypes 196 G/G 101 (60) 53 (46) 0.0207 196 G/A 65 (40) 61 (54) 0.0158 270 C/C 112 (67) 109 (96) b0.0001 270 C/T 55 (33) 5 (4) b0.0001
Odds ratio (95%CI)
pb value⁎
1.69 (1.05–2.72) 0.59 (0.37–0.95) 0.09 (0.03–0.24) 10.70 (4.11–27.88)
0.0298 0.0298 b0.00001 b0.00001
b) MS males n (%)
Control males n (%)
pa value⁎
BDNF gene polymorphisms genotypes 196 G/G 38 (60) 30 (48) 0.1528 196 G/A 24 (40) 33 (52) 0.1072 270 C/C 45 (71) 58 (92) 0.0027 270 C/T 18 (29) 5 (8) 0.0027
Odds ratio (95%CI)
pb value⁎
0.65 (0.32–1.31) 1.52 (0.76–3.04) 0.21 (0.07–0.63) 4.64 (1.58–13.60)
0.2270 0.2269 0.0047 0.0047
pacounted with chi-square test. pbcounted with logistic regression analysis. ⁎ p value for significance after Bonferroni correction is 0.0125.
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et al., 2005, Blanco et al., 2006), but these studies did not establish an association with MS susceptibility or clinical course. However, Liguori et al. determined that presence of the Met-allele correlated with a lower volume of cerebral grey matter, although no correlation was found between global neuropsychological function and any studied allele (Liguori et al., 2007). The genotype distribution of the G196A polymorphism presented here was similar to that reported before (Lindquist et al., 2005). However, a new finding from our study is that the G/ G and C/T genotypes were statistically more frequent in MS subjects than in healthy controls, thus providing the association with increased MS risk. This result was also demonstrated in some previous reports in other neurological diseases such as schizophrenia (Szekeres et al., 2003) and Alzheimer's disease (Matsushita et al., 2005). Interestingly, our study revealed gender differences in susceptibility to MS within these genotypes that were not reported in any of the previous studies. BDNF 196G/G genotype was found to be responsible for increased incidence of MS in the total patient group, but when gender was considered, this genotype was significantly elevated only in females. Moreover, the BDNF 270C/T genotype was found to be responsible for MS risk, independent of gender (Tables 2, 3a, b). The G196A polymorphism was found to be correlated with MS disease characteristics, namely the age when the first signs of the disease appeared and also the rate of disease progression in males. Since functional alterations of BDNF might be responsible for impaired axonal repair following inflammation, our finding may be important in predicting clinical outcome parameters such as accumulation of disability. These results raise new questions concerning how gender differences actually contribute to increased disease susceptibility and clinical progression, according to different polymorphic genotypes. In this vein, a recent study on estrogen–BDNF interactions by Sohrabij and Lewis (2006) was the first to demonstrate that BDNF-synthesizing neurons co-localized with estrogen receptors in the forebrain, thus suggesting regulation of this gene by a gonadal hormone. Although ours is the first report to show an association of both BDNF gene polymorphisms with MS in a homogenous and stable Polish MS population, the small number of patients and controls does not provide enough power to determine an exact genetic effect. Thus, additional studies will be needed to validate our results, with special attention to gender effects. References Blanco, Y., Gomez-Choco, M., Arostegui, J.L., Casanova, B., MartinezRodriguez, J.E., Bosca, I., Munteis, E., Yagüe, J., Graus, F., Saiz, A., 2006. No association of the Val66Met polymorphism of brain-derived neurotrophic factor (BDNF) to multiple sclerosis. Neurosci. Lett. 217–219.
Dhib-Jalbut, S., Arnold, D.L., Cleveland, D.W., Fisher, M., Friendlander, R.M., Mouradian, M.M., Przedborski, S., Trapp, B.D., Wyss-Coray, T., Yong, V.W., 2006. Neurodegeneration and neuroprotection in multiple sclerosis and other neurodegenerative diseases. J. Neuroimmunol. 176, 198–215. Hohlfeld, R., Kerschensteiner, M., Stadelmann, Ch., Lassmann, H., Weckerle, H., 2000. The neuroprotective effect of inflammation: implications for the therapy of multiple sclerosis. J. Neuroimmunol. 107, 161–166. Kurtzke, J.F., 1983. Rating neurologic impairment in multiple sclerosis: an expanded disability status scale (EDSS). Neurology 33, 1444–1452. Liguori, M., Fera, F., Gioia, M.C., Valentino, P., Manna, I., Condino, F., Cerasa, A., LaRussa, A., Clodomiro, A., Paolillo, A., Nistico, R., Vercillo, L., Cittadella, R., Quattrone, A., 2007. Investigating the role of brain-derived neurotrophic factor in relapsing–remitting multiple sclerosis. Genes Brain Behav. 6, 177–183. Lindquist, S., Schott, B.H., Ban, M., Compston, D.A.S., Sawcer, S., Sailer, M., 2005. The BDNF-Val66Met polymorphism: implication for susceptibility to multiple sclerosis and severity of disease. J. Neuroimmunol. 167, 183–185. Matsushita, S., Arai, H., Matsui, T., Yuzuriha, T., Urakami, K., Masaki, T., Higueni, S., 2005. Brain-derived neurotrophic factor gene polymorphisms and Alzheimer's disease. J. Neural Transm. 112, 703–711. McDonald, W.I., Compston, A., Edan, G., Goodkin, D., Hartung, H.P., Lublin, F.D., McFarland, H.F., Paty, D.W., Polman, C.H., Reingold, S.C., SandbergWollheim, M., Sibley, W., Thompson, A., van den Noort, S., Weinshenker, B.Y., Wolinsky, J.S., 2001. Recommended diagnostic criteria for multiple sclerosis: guidelines from the International Panel on the diagnosis of multiple sclerosis. Ann. Neurol. 121–127. Moalem, G., Gdalyahu, A., Shani, Y., Otten, U., Lazarovici, Ph., Cohen, I.R., Schwarz, M., 2000. Production of neurotrophins by activated T cells: implications for neuroprotective autoimmunity. J. Autoimmun. 15, 331–345. Mycko, M., Papoian, R., Boschert, U., Raine, C.S., Selmaj, K.W., 2004. Microarray gene expression profiling of chronic active and inactive lesions in multiple sclerosis. Clin. Neurol. Neurosurg. 106, 223–229. Neves-Pereira, M., Mundo, E., Muglia, P., King, N., Macciardi, F., Kennedy, J.L., 2002. The brain-derived neurotrophic factor gene confers susceptibility to bipolar disorder: evidence from family-based association study. Am. J. Hum. Genet. 71, 651–655. Oksenberg, J.R., Barcellos, L.F., 2000. The complex genetic aetiology for multiple sclerosis. J. NeuroVirol. 6, 10–14. Polman, Ch.H., Reingold, S.C., Edan, G., Filippi, M., Hartung, H.-P., Kappos, L., Lublin, F.D., Metz, L.M., McFarland, H.F., O'Connor, P.W., SandbergWollheim, M., Thompson, A.J., Weinshenker, B.G., Wolinsky, J.S., 2005. Diagnostic criteria for multiple Sclerosis: 2005 revisions to the „McDonald Criteria“. Ann. Neurol. 58, 840–846. Riemenschneider, M., Schwarz, S., Wagenpfeil, S., Diehl, J., Müller, U., Förstl, H., Kurz, A., 2002. A polymorphism of the brain-derived neurotrophic factor (BDNF) is associated with Alzheimer's disease in patients lacking the apolipoprotein E ɛ4 allele. Mol. Psychiatry 7, 782–785. Rosenberg, S.S., Ng, B.K., Chan, J.R., 2006. The quest for remyelination: a new role for neurotrophins and their receptors. Brain Pathol. 16, 288–294. Sohrabij, F., Lewis, D., 2006. Estrogen–BDNF interactions: implications for neurodegenerative diseases. Front. Neuroendocrinol. 274, 404–414. Szekeres, G., Juhasz, A., Rimanoczy, A., Keri, S., Janka, Z., 2003. The C720T polymorphism of the brain-derived neurotrophic factor gene is associated with schizophrenia. Schizophr. Res. 65, 15–18.
Short communication
BDNF A196G and C270T gene polymorphisms and susceptibility to multiple sclerosis in the polish population. Gender differences Dagmara Mirowska-Guzel a,b , Anna Mach a , Grazyna Gromadzka a,b , Andrzej Czlonkowski b , Anna Czlonkowska a,b,⁎ b
a 2nd Department of Neurology, Institute of Psychiatry and Neurology, Sobieskiego 9, 02-957 Warsaw, Poland Department of Clinical and Experimental Pharmacology, Medical University of Warsaw, Krakowskie Przedmiescie 26/28, 00-297 Warsaw, Poland
Received 19 July 2007; received in revised form 17 October 2007; accepted 17 October 2007
Abstract Two single nucleotide polymorphisms of the human BDNF gene, G196A and C270T, and their impact on the susceptibility to MS and disease progression in the Polish population were investigated. Increased risk of the disease was found for 196G/G carriers (OR — 1.63, p = 0.01) (only females) and 270C/T carriers (OR — 7.76, p b 0.001) (both males and females). The first signs of the disease appeared earlier in 196G/G than 196G/A patients (p = 0.01), but it was limited to males. Our results show that C270T and G196A BDNF polymorphisms may affect susceptibility to and onset of MS, but further verification is needed, with special attention to gender differences. © 2007 Elsevier B.V. All rights reserved. Keywords: Multiple sclerosis; BDNF; Gender differences
1. Introduction
2. Subjects
Multiple sclerosis (MS) pathogenesis is complex and still not fully understood. There is some evidence that disease develops in genetically predisposed individuals concurrent with environmental factors (Oksenberg and Barcellos, 2000). It is suspected that genetic factors may also play an important role in the clinical course of the disease (Mycko et al., 2004). It has recently been proposed that neurodegeneration accompanies autoimmunity in MS subjects (Dhib-Jalbut et al., 2006), thus suggesting potential beneficial effect of neurotrophic factors such as brain-derived neurotrophic factors (BDNF), nerve growth factor (NGF) and neurotrophin-3 (NT-3). These factors are thought to contribute to neuronal survival, axonal and neuronal repair (Hohlfeld et al., 2000, Moalem et al., 2000) and remyelination (Rosenberg et al., 2006) and may serve as attractive candidate genes controlling MS disease characteristics.
230 patients (63 men and 167 women) with MS diagnosed according to the McDonald criteria (McDonald et al., 2001, Polman et al., 2005) and 177 unrelated, sex matched (63 males and 114 females) healthy controls (mean age of 40.09 ± 10.19) were included. Patients with relapsing–remitting (RR) and secondary-progressive (SP) disease courses were evaluated for onset of RRMS. Disease severity was estimated using EDSS (Kurtzke, 1983) and progression index (PI: EDSS/disease duration). Patient demographics are presented in Table 1. A single sample of peripheral blood (2.7 ml) was collected from all subjects after obtaining written informed consent. The study protocol was approved by the Local Hospital Ethics Committee.
⁎ Corresponding author. 2nd Department of Neurology, Institute of Psychiatry and Neurology, Sobieskiego 9, 02-957 Warsaw, Poland. Tel.: +48 22 842 76 83; fax: +48 22 842 40 23. E-mail address: [email protected] (A. Czlonkowska). 0165-5728/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jneuroim.2007.10.013
3. Methods Genomic DNA was isolated with Tri-Reagent (SIGMA, Poland). BDNF C270T and G196A (G758A) genotyping was performed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP), as described previously ( Riemenschneider et al., 2002; Neves-Pereira et al., 2002).
D. Mirowska-Guzel et al. / Journal of Neuroimmunology 193 (2008) 170–172
171
Table 2 BDNF 196 and 270 genotype frequencies in MS and control subjects
4. Statistical analysis Statistical analysis was performed with Statistica PL version 7.1 (StatSoft® Poland, 2006). Genotype and allele frequencies were compared using the chi-square test. p ≤ 0.05 was considered as statistically significant. For multiple comparisons, the Bonferroni correction was used with a significant p value being b0.0125. Continuous data were compared using the Mann Whitney Test. A multiple logistic regression model expressed as an adjusted odds ratio (OR) and a 95% confidence interval (95% CI) was applied for the measurement of strength of association between genetic polymorphisms and MS.
MS patients Controls n (%) n (%)
pa value⁎
Odds ratio (95%CI)
BDNF gene polymorphisms genotypes 196 G/G 139 (60) 83 (47) 0.0065 196 G/A 89 (40) 94 (53) 0.0038 270 C/C 157 (68) 167 (94) b0.0001 270 C/T 73 (32) 10 (6) b0.0001 196 G/A 73 (32) 91 (51) 0.0001 and 270C/C 196 G/G 58 (25) 8 (4.5) b0.0001 and 270 C/T
pb value⁎
1.63 (1.11–2.41) 0.0129 0.61 (0.41–0.90) 0.0129 0.13 (0.06–0.26) b0.0001 7.76 (3.86–15.61) b0.0001 0.14 (0.06–0.30) b0.00001 7.12 (3.29–15.41) b0.00001
pa counted with chi-square test. pb counted with logistic regression analysis. ⁎ p value for significance after Bonferroni correction is 0.0125.
5. Results 5.1. Genotypes and susceptibility to MS We found an increased risk of susceptibility to MS for BDNF 196G/G (OR — 1.63, p = 0.0129) and for BDNF 270C/T (OR — 7.76, p b 0.0001). Combined effects of the 196G/G and 270C/T genotype in carriers significantly increased the risk of MS compared to non-carriers (OR — 7.12, p b 0.00001) (Table 2). 5.2. Gender, genotype and MS risk In males, the 270C/T genotype (C270T BDNF polymorphism) was associated with a significantly increased risk of MS (OR — 4.64, p = 0.0047, Table 3b), whereas the G196A BDNF polymorphism did not confer an increased risk of MS. In females, the same 270C/T genotype conferred a highly significant risk of MS (OR — 10.70, p b 0.00001, Table 3a), whereas the 196G/G genotype was associated with a less pronounced but still significantly increased risk of MS (OR — 1.69, p = 0.0298). 5.3. Genotypes and clinical parameters
This difference in age of onset was also evident in subjects who presented initially with RRMS (25 years of age in the 196G/G group versus 29 years of age in the 196G/A group (p = 0.019). In contrast, no difference in age of onset was noted in PPMS subjects with the C270T polymorphism. In sex-based analysis, disease onset occurred at 22 years of age in RRMS males with the 196G/G polymorphism versus 30 years of age in males with 196G/A (p = 0.012). There was also a border-line difference (p = 0.046) in the rate of progression in this group, with a progression index of 0.4 in males with the 196G/G genotype versus 0.6 in males with the 196G/A genotype. 6. Discussion Previous studies evaluating BDNF polymorphisms in MS focused on the G196A (Val66Met) polymorphism (Lindquist Table 3 BDNF 196 and 270 genotype frequencies in MS and control subjects by gender (a: females; b: males) a) MS females n (%)
In 196G/G subjects, the first signs of MS appeared at the age of 25, versus 30 years of age in 196G/A patients (p = 0.010). Table 1 Demographic and clinical characteristics of MS subjects All MS subjects RR, n = 187 (n = 230) (82%) Female/male Age (mean ± SD)
167/63 38.11 ± 10.94
Age of onset (mean ± SD) Age of diagnosis (mean ± SD) Disease duration (mean ± SD) Median EDSS (range) Progression index (mean ± SD)
29.18 ± 9.98 31.80 ± 10.75 9.04 ± 8.25 3.5 (0.0–8.5) 0.83 ± 0.96
138/49 36.10 ± 9.79
SP, n = 30 (13%)
PP, n = 13 (5%)
21/9 8/5 46.83 ± 12.28 46.61 ± 10.19 28.33 ± 9.63 30.55 ± 9.94 37.54 ± 11.27 31.10 ± 10.71 32.72 ± 9.38 39.54 ± 11.66 7.96 ± 7.06 15.72 ± 11.69 8.70 ± 7.94 3.0 (0.0–8.5) 7.0 (3.0–9.0) 4.0 (1.5–7.0) 0.81 ± 0.97 0.68 ± 0.52 1.29 ± 1.40
Control females n (%)
pa value⁎
BDNF gene polymorphisms genotypes 196 G/G 101 (60) 53 (46) 0.0207 196 G/A 65 (40) 61 (54) 0.0158 270 C/C 112 (67) 109 (96) b0.0001 270 C/T 55 (33) 5 (4) b0.0001
Odds ratio (95%CI)
pb value⁎
1.69 (1.05–2.72) 0.59 (0.37–0.95) 0.09 (0.03–0.24) 10.70 (4.11–27.88)
0.0298 0.0298 b0.00001 b0.00001
b) MS males n (%)
Control males n (%)
pa value⁎
BDNF gene polymorphisms genotypes 196 G/G 38 (60) 30 (48) 0.1528 196 G/A 24 (40) 33 (52) 0.1072 270 C/C 45 (71) 58 (92) 0.0027 270 C/T 18 (29) 5 (8) 0.0027
Odds ratio (95%CI)
pb value⁎
0.65 (0.32–1.31) 1.52 (0.76–3.04) 0.21 (0.07–0.63) 4.64 (1.58–13.60)
0.2270 0.2269 0.0047 0.0047
pacounted with chi-square test. pbcounted with logistic regression analysis. ⁎ p value for significance after Bonferroni correction is 0.0125.
172
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et al., 2005, Blanco et al., 2006), but these studies did not establish an association with MS susceptibility or clinical course. However, Liguori et al. determined that presence of the Met-allele correlated with a lower volume of cerebral grey matter, although no correlation was found between global neuropsychological function and any studied allele (Liguori et al., 2007). The genotype distribution of the G196A polymorphism presented here was similar to that reported before (Lindquist et al., 2005). However, a new finding from our study is that the G/ G and C/T genotypes were statistically more frequent in MS subjects than in healthy controls, thus providing the association with increased MS risk. This result was also demonstrated in some previous reports in other neurological diseases such as schizophrenia (Szekeres et al., 2003) and Alzheimer's disease (Matsushita et al., 2005). Interestingly, our study revealed gender differences in susceptibility to MS within these genotypes that were not reported in any of the previous studies. BDNF 196G/G genotype was found to be responsible for increased incidence of MS in the total patient group, but when gender was considered, this genotype was significantly elevated only in females. Moreover, the BDNF 270C/T genotype was found to be responsible for MS risk, independent of gender (Tables 2, 3a, b). The G196A polymorphism was found to be correlated with MS disease characteristics, namely the age when the first signs of the disease appeared and also the rate of disease progression in males. Since functional alterations of BDNF might be responsible for impaired axonal repair following inflammation, our finding may be important in predicting clinical outcome parameters such as accumulation of disability. These results raise new questions concerning how gender differences actually contribute to increased disease susceptibility and clinical progression, according to different polymorphic genotypes. In this vein, a recent study on estrogen–BDNF interactions by Sohrabij and Lewis (2006) was the first to demonstrate that BDNF-synthesizing neurons co-localized with estrogen receptors in the forebrain, thus suggesting regulation of this gene by a gonadal hormone. Although ours is the first report to show an association of both BDNF gene polymorphisms with MS in a homogenous and stable Polish MS population, the small number of patients and controls does not provide enough power to determine an exact genetic effect. Thus, additional studies will be needed to validate our results, with special attention to gender effects. References Blanco, Y., Gomez-Choco, M., Arostegui, J.L., Casanova, B., MartinezRodriguez, J.E., Bosca, I., Munteis, E., Yagüe, J., Graus, F., Saiz, A., 2006. No association of the Val66Met polymorphism of brain-derived neurotrophic factor (BDNF) to multiple sclerosis. Neurosci. Lett. 217–219.
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