P300 evoked potential and serum BDNF level are related to conversion of MCI to Alzheimer's dementia, regarding genetic background.

Abstract

Individuals with mild cognitive impairment (MCI) have increased risk to convert to Alzheimer's dementia (AD). Our aim was to evaluate the role of auditory evoked potential N200 and P300 and serum level of BDNF in predicting conversion from MCI patients to AD, considering APOE and BDNF genetic background. 32 MCI patients were prospectively evaluated. They underwent annual geriatric evaluation and neuropsychological assessment. Cognitive and functional status were established considering both neuropsychology and geriatrics evaluation. AD was diagnosed based on McKhann criteria. Genotyping of APOE alleles and BDNF (Val66Met) was performed by real time PCR. Participants were divided in carriers of APOE ε-4 allele (APOE4+) and non-carriers (APOE4-). At baseline, BDNF concentration was assessed by ELISA methodology and, the participants were also submitted to evoked potential tests (N200 and P300) by means of auditory stimuli based on the auditory oddball paradigm. APOE+ were compared with APOE-. Anova statistical methods, Bonferroni post-hoc analysis, Mann Whitney and Student T tests were used, in addition to the evaluation of median, mean and standard deviation. At baseline, participants had a mean age of 74.78 ± 8.35 years, 4.61 ± 3.96 years of formal education. 60.9% were female. The follow-up mean time was 4.02 ± 1.93 years. During the follow-up period, 11 MCI participants converted to AD (MCI-c) and 22 remained stable (MCI-nc). 34.9% of total sample were APOE+. We did not observe any statistical difference in N200 latency (p = 0.715), P300 latency (p = 0.993) and P300 amplitude (p = 0.574) between MCI-c and MCI-nc. However, among APOE+ MCI patients who converted to AD, a significant difference was observed in P300 latency in relation to MCI-nc (419.63 ± 29.74 versus 349.85 ± 35.82ms, p value: 0.023). We did not observe a relationship between BDNF serum level and conversion to AD (p: 0.061). Nevertheless, in Val/Val BDNF genotype, higher BDNF was associated with conversion to AD (10093.03 ± 3055.49pg / ml versus 5755, 85 ± 1873.20pg / ml, p-value: 0.017). P300 latency and serum BDNF level in APOE+ and Val/Val BDNF genotype patients are related to conversion of MCI to AD.