Exercise in the Elderly: BDNF and Executive Function

Exercise promotes cognitive function in children, adults and elderly individuals.

The mechanism for this effect is unclear. Some of the effect may be due to a general improvement in vascular function and health.

Another potential mechanism is via increased neuroplasticity mediated by neurotrophic factors.

Brain-derived neurotrophic factor (BNDF) is a known contributor to brain neuroplasticity. Levels of BNDF can be determined with serum assays.

RL Leckie and colleagues recently found support for BNDF mediation in an exercise in an interventional study with an elderly population.

The key elements of the design for their study included the following elements.

• Participants: Adults between the ages of 55 and 80
• Exercise intervention: Daily supervised walking sessions beginning with 10 minutes increasing to 40 minutes. Control intervention included stretching and toning sessions lead by an exercise professional
• Cognitive assessment: Task-switching paradigm commonly used to assess executive function
• Blood assay: Serum brain-derived neurotropic factor (BNDF) levels and BDNF genotype
• Statistical analysis: Multivariate linear regression analysis with key dependent variable being cognitive performance after one year of intervention

The main findings from the study included:

• Serum BDNF increased in the exercise group
• This effect was limited to primarily the participants over 70 years of age
• Enhanced executive function following exercise was demonstrated in those over 70
• BDNF level increases in the over 70 age group correlated with cognitive performance

The authors note their does not mean exercise is not important for cognitive function in the younger age group (55-70 years of age). Their study only highlights the age interaction with BDNF in moderating a single executive function task.

BDNF levels decrease with age and the level of decrease in BDNF correlates with reduction in volume of the brain hippocampus. The hippocampus plays a key role in memory function and in decline in memory associated with aging.

It is quite possible that regular exercise after age 70 reduces the age related effect on cognition moderated by BDNF.

Readers with more interest in this study can access the free full text manuscript by clicking on the PMID link in the citation below.

Photo of ring kingfisher is from the author's files.

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Leckie RL, Oberlin LE, Voss MW, Prakash RS, Szabo-Reed A, Chaddock-Heyman L, Phillips SM, Gothe NP, Mailey E, Vieira-Potter VJ, Martin SA, Pence BD, Lin M, Parasuraman R, Greenwood PM, Fryxell KJ, Woods JA, McAuley E, Kramer AF, & Erickson KI (2014). BDNF mediates improvements in executive function following a 1-year exercise intervention. Frontiers in human neuroscience, 8 PMID: 25566019

Hoarding Linked to BDNF Gene in OCD

In two previous posts on hoarding, I have reviewed some the pathway and profile of animal hoarding as well as the common mental health problems found with hoarding.

Today I will review a study that provides some insight into potential genetic contributions to hoarding behavior.  Of interest, this genetic link also appears to carry some increased risk for obesity.

Timpano from the University of Miama along with colleagues at Florida State University and the National Institute of Mental Health Intramural programs have recently published a study of 301 subjects with obsessive compulsive disorder (OCD).

In previous posts it was noted that hoarding can occur in the context of OCD but that not all hoarders will meet criteria for OCD.  In the Timpano et al study, subjects started with a diagnosis of OCD and then were grouped into those with hoarding and those without hoarding behaviors.

The hoarding classification status was assigned based upon the subject response to two items found on the Yale Brown Obsessive Compulsive Scale (YBOCS).  One item queried about tending to save objects and second item queried about difficulty discarding objects.  Hoarding subjects were required to endorse both items.

The research team then looked at the subjects and the brain-derived neurotrophic factor (BDNF) status.  BDNF has been a genetic region of interest in a variety of clinical neuroscience conditions including schizophrenia, anxiety and aggression.  Additionally it appears to be involved in memory function and variants of BDNF have been linked to higher rates of obesity.

BDNF appears to serve a role as a central neurological system plasticity factor and modulates both serotonin and glutamatergic neurotransmitter systems.  The BDNF gene codes for a protein that can vary in an region in status of two amino acids valine and methionine.  At this regions, individuals can be assigned one of three genetic types: Val/val, val/met or met/met.

The Timpano et al team found the following key findings:

• About 25% of those with OCD met criteria for being hoarders

• The BDNF val/val genotype was found in 77% of the hoarding group versus only 60% of the non-hoarding OCD group
• The BDNF val/val genotype correlated with increased hoarding symptom severity and BMI
• 45% of the hoarding group met criteria for obesity (BMI >30) versus only 21% of the OCD only group

The authors note that there are animal models of hoarding where hoarding behaviors have been linked to dysregulation of feeding behaviors.  When humans begin to hoard objects, there may also be a overlapping drive to hoard (and consume) food.  The authors note there may be a complex gene mechanism whereby individuals display hoarding, increased body weight and psychopathology as evidence of a "thrifty gene" strategy that may have survival and evolutionary manifestations.

It would be informative to examine the BDNF gene status of hoarders without a diagnosis of OCD.  The authors note that interaction between BDNF and serotonergic function may partially explain some other the BDNF-hoarding-obesity triad.

There role of serotonin in OCD has received significant research attention. In the next post, I will look at the potential for selective serotonergic antidepressants pharmocotherapy in the treatment of hoarding behaviors.

The molecular model of BDNF above is in the public domain from a Creative Commons Attribution-ShareAlike 3.0 file (Wikepedia) authored by Microswitch.

Timpano, K., Schmidt, N., Wheaton, M., Wendland, J., & Murphy, D. (2011). Consideration of the BDNF gene in relation to two phenotypes: hoarding and obesity. Journal of Abnormal Psychology DOI: 10.1037/a0024159