The impact of BDNF Val66Met on cognitive skills in veterans with posttraumatic stress disorder

A pilot study examining BDNF Val66Met polymorphism and biological sex: Relationships with baseline cognitive functioning in adolescent athletes

The purpose of this exploratory study was to examine interactive relationships between a common brain-derived neurotrophic factor (BDNF) polymorphism (Val66Met) and biological sex on cognitive functioning in a sample of healthy adolescent athletes. Participants included 82 student athletes (age: M = 12.85 years, SD = 1.13) who were involved in a clinically-based sports-concussion management program. Athletes completed the ImPACT computerized battery at baseline and provided buccal samples for determination of their BDNF genotype. Two-way ANOVAs were used to evaluate the effect of BDNF genotype (Met+ vs. Met-) and sex (male vs. female) on cognitive functioning (subgroup n's: Female/Met+ = 12, Female/Met- = 26, Male/Met+ = 12, Male/Met- = 32). ANOVAs revealed non-significant main effects for both BDNF genotype and sex across all four cognitive composites. However, there was a significant BDNF genotype by sex interaction for the visual-motor speed composite (p = .015; ηp2 = .073), such that female Met carriers demonstrated better performance than male Met carriers. In contrast, no differences were found on visual-motor speed performance between females and males without a Met allele. Although these results will need to be replicated using larger samples, our preliminary findings lend support to the view that the Met allele may be somewhat neuroprotective in healthy adolescent females.

Prominent genetic variants and epigenetic changes in post-traumatic stress disorder among combat veterans

Post-traumatic stress disorder (PTSD) is one of the most widespread and disabling psychiatric disorders among combat veterans. Substantial interindividual variability in susceptibility to PTSD suggests the presence of different risk factors for this disorder. Twin and family studies confirm genetic factors as important risk factors for PTSD. In addition to genetic factors, epigenetic factors, especially DNA methylation, can be considered as a potential mechanism in changing the risk of PTSD. So far, many genetic and epigenetic association studies have been conducted in relation to PTSD. In genetic studies, many single nucleotide polymorphisms have been identified as PTSD risk factors. Meanwhile, the variations in catecholamines-related genes, serotonin transporter and receptors, brain-derived neurotrophic factor, inflammatory factors, and apolipoprotein E are the most prominent candidates. CpG methylation in the upstream regions of many genes is also considered a PTSD risk factor. Accurate identification of genetic and epigenetic changes associated with PTSD can lead to the presentation of suitable biomarkers for susceptible individuals to this disorder. This study aimed to delineate prominent genetic variations and epigenetic changes associated with post-traumatic stress disorder in military veterans who have experienced combat, focusing on genetic and epigenetic association studies.

Brain-derived neurotrophic factor gene polymorphism affects cognitive function and neurofilament light chain level in patients with subcortical ischaemic vascular dementia

Objective

To investigate the effects of brain-derived neurotrophic factor (BDNF) gene polymorphism on cognitive function, neuroimaging and blood biological markers in patients with subcortical ischaemic vascular dementia (SIVD).

Methods

A total of 81 patients with SIVD were included. According to their BDNF gene polymorphism, the participants were divided into the Val/Val (n = 26), Val/Met (n = 35), and Met/Met (n = 20) groups. A comprehensive neuropsychological evaluation and multimodal brain MRI scan were performed. MRI markers for small vessel disease were visually rated or quantitatively analysed. Moreover, 52 patients were further evaluated with blood marker assays, including amyloid beta (Aβ), phosphorylated tau at threonine-181 (P-tau181), glial fibrillary acidic protein (GFAP), total tau (T-tau) and neurofilament light chain (NfL).

Results

There were no significant differences in demographics, disease duration or MRI markers of small vessel disease between the three groups. Compared with the Val/Val and Val/Met groups, the Met/Met group showed worse performance in the verbal fluency test and higher levels of plasma NfL.

Conclusion

The rs6265 polymorphism of the BDNF gene is associated with semantic language fluency in patients with SIVD. The Met genotype may be a risk factor for cognitive impairment and neuronal injury.

The influence of the BDNF Val66Met genotype on emotional recognition memory in post-traumatic stress disorder

Dysregulated consolidation of emotional memories is a core feature of posttraumatic stress disorder (PTSD). Brain Derived Neurotrophic Factor (BDNF) influences synaptic plasticity and emotional memory consolidation. The BDNF Val66Met polymorphism has been associated with PTSD risk and memory deficits respectively, although findings have been inconsistent, potentially due to a failure to control for important confounds such as sex, ethnicity, and the timing/extent of previous trauma experiences. Furthermore, very little research has examined the impact of BDNF genotypes on emotional memory in PTSD populations. This study investigated the interaction effects of Val66Met and PTSD symptomatology in an emotional recognition memory task in 234 participants divided into healthy control (n = 85), trauma exposed (TE: n = 105) and PTSD (n = 44) groups. Key findings revealed impaired negative recognition memory in PTSD compared to control and TE groups and in participants with the Val/Met compared to the Val/Val genotype. There was a group × genotype interaction showing no Met effect in the TE group despite significant effects in PTSD and controls. Results suggest that people previously exposed to trauma who do not develop PTSD may be protected from the BDNF Met effect, however more research is needed to replicate findings and to explore the epigenetic and neural processes involved.

Reduced plasma BDNF concentration and cognitive decline in veterans with PTSD

Post-traumatic stress disorder (PTSD) is a trauma and stress related disorder frequently associated with cognitive decline. War veterans with PTSD have a higher risk of developing dementia than healthy subjects. Brain derived neurotrophic factor (BDNF) is an important protein that modulates plasticity, memory consolidation and cognitive processes. Lower circulating BDNF levels were related to memory impairment and cognitive deterioration. The aim of this study was to evaluate cognitive deterioration and plasma BDNF concentration in 120 veterans with combat related PTSD, 120 healthy controls, 47 subjects with mild cognitive impairment (MCI) and 76 patients with Alzheimer's disease (AD), and to assess if plasma BDNF concentration might be used as biomarker of cognitive deterioration. Veterans with PTSD had significantly decreased plasma BDNF concentration and worse cognitive performances (assessed using the Mini Mental State Examination, Clock Drawing test and Montreal Cognitive Assessment scores/categories) than healthy subjects, and similarly reduced plasma BDNF and cognitive decline as MCI subjects. Reduced plasma BDNF was found in cognitively impaired subjects. These results suggest that veterans with PTSD should be closely monitored in order to early detect and predict cognitive worsening and promote interventions that might help restore blood BDNF levels and cognitive functions.

Interactive effects of the BDNF Val66Met polymorphism and posttraumatic stress disorder on cognition in U.S. military veterans

Posttraumatic stress disorder (PTSD) is associated with mild-to-moderate deficits in cognition. The Met allele of the brain-derived neurotrophic factor (BDNF) Val66Met gene may also be associated with deficits in cognition. However, findings are inconsistent and may be sensitive to moderating variables such as psychopathology. While emerging research suggests that PTSD and the Met allele may interact, few studies have replicated this effect or examined the interactive effect of PTSD and the Met allele on subjective cognition. To address this gap, the current study analyzed data from European-American (EA) U.S. military veterans (n = 1244) who participated in the National Health and Resilience in Veterans Study (NHRVS) to examine the main and interactive effects of BDNF Val66Met genotype and probable PTSD on objective and subjective cognition. Results revealed significant (p's < 0.001) interactions between Met allele carrier status and probable PTSD in objective and subjective cognition. Among individuals with probable PTSD (n = 131), the Met allele was associated with poorer objective (p < .001, d = 0.62) and subjective cognition (p = .001, d = 0.53). Among individuals without PTSD (n = 1113), the Met allele was not significantly associated with objective or subjective cognition. These findings suggest that PTSD may moderate the association between Met allele carrier status and cognition. Implications of these results for the mitigation of cognitive dysfunction in older veterans are discussed.

The association between BDNF C270T genetic variants and smoking in patients with mental disorders and in healthy controls

Studies investigating the association between smoking and the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism have reported inconclusive results, while the studies on the association of smoking status with BDNF C270T polymorphism are missing. We aimed to determine the association of smoking and BDNF Val66Met and C270T genetic variants in control subjects and patients with mental disorders. This study included 3502 Caucasian subjects: 918 healthy controls and 2584 patients with mental disorders (519 individuals with posttraumatic stress disorder (PTSD), 419 patients with depression, 996 patients with schizophrenia, and 650 patients with alcohol dependence). The frequency of the BDNF Val66Met and C270T variants were presented in codominant, dominant and recessive models. BDNF C270T, but not BDNF Val66Met polymorphism, was significantly associated with smoking in all groups, since the presence of the C270T T allele was more frequently found in smokers compared to non-smokers. Significant predictors of smoking were sex, age and BDNF C270T genetic variants. However, after detailed analysis of the separate diagnostic entities, the significant association of BDNF C270T polymorphism was confirmed only in healthy subjects, but not in patients with mental disorders; and was not related to number of cigarettes smoked per day. In patients with alcohol dependence, the severity of smoking was significantly associated with BDNF Val66Met variants. This is a first report of the significant association between the BDNF C270T polymorphism and smoking status in the large groups of Caucasian cases/controls.

Moderating Effects of BDNF Genetic Variants and Smoking on Cognition in PTSD Veterans

Posttraumatic stress disorder (PTSD) is frequently associated with cognitive disturbances and high prevalence of smoking. This study evaluated cognition in war veterans with PTSD and control subjects, controlled for the effect of smoking and brain derived neurotrophic factor (BDNF) rs6265 and rs56164415 genotypes/alleles. Study included 643 male war veterans with combat related PTSD and 120 healthy controls. Genotyping was done by real time PCR. Cognitive disturbances were evaluated using the Positive and Negative Syndrome Scale (PANSS) cognition subscale and the Rey-Osterrieth Complex Figure (ROCF) test scores. Diagnosis (p < 0.001), BDNF rs56164415 (p = 0.011) and smoking (p = 0.028) were significant predictors of the cognitive decline in subjects with PTSD. BDNF rs56164415 T alleles were more frequently found in subjects with PTSD, smokers and non-smokers, with impaired cognition, i.e., with the higher PANSS cognition subscale scores and with the lower ROCF immediate recall test scores. Presence of one or two BDNF rs56164415 T alleles was related to cognitive decline in PTSD. The T allele carriers with PTSD had advanced cognitive deterioration in smokers and nonsmokers with PTSD, and worse short-term visual memory function. Our findings emphasize the role of the BDNF rs56164415 T allele and smoking in cognitive dysfunction in war veterans with PTSD.