Elsevier

Neuroscience

Volume 155, Issue 3, 26 August 2008, Pages 751-759
Neuroscience

Cellular neuroscience
Docosahexaenoic acid dietary supplementation enhances the effects of exercise on synaptic plasticity and cognition

https://doi.org/10.1016/j.neuroscience.2008.05.061Get rights and content

Abstract

Omega-3 fatty acids (i.e. docosahexaenoic acid; DHA), similar to exercise, improve cognitive function, promote neuroplasticity, and protect against neurological lesion. In this study, we investigated a possible synergistic action between DHA dietary supplementation and voluntary exercise on modulating synaptic plasticity and cognition. Rats received DHA dietary supplementation (1.25% DHA) with or without voluntary exercise for 12 days. We found that the DHA-enriched diet significantly increased spatial learning ability, and these effects were enhanced by exercise. The DHA-enriched diet increased levels of pro–brain-derived neurotrophic factor (BDNF) and mature BDNF, whereas the additional application of exercise boosted the levels of both. Furthermore, the levels of the activated forms of CREB and synapsin I were incremented by the DHA-enriched diet with greater elevation by the concurrent application of exercise. While the DHA diet reduced hippocampal oxidized protein levels, a combination of a DHA diet and exercise resulted in a greater reduction rate. The levels of activated forms of hippocampal Akt and CaMKII were increased by the DHA-enriched diet, and with even greater elevation by a combination of diet and exercise. Akt and CaMKII signaling are crucial step by which BDNF exerts its action on synaptic plasticity and learning and memory. These results indicate that the DHA diet enhanced the effects of exercise on cognition and BDNF-related synaptic plasticity, a capacity that may be used to promote mental health and reduce risk of neurological disorders.

Section snippets

Experimental designs and tissue preparation

Sprague–Dawley rats (Charles River Laboratories, Inc., Wilmington, MA, USA) weighing between 200 and 240 g were housed in cages and maintained in environmentally controlled rooms (22–24 °C) with a 12-h light/dark cycle. After acclimatization for 1 week on standard rat chow, one set of rats was exposed to a DHA-enriched diet (1.25% DHA), while another set was exposed to regular diet (RD). The rats were then maintained on the diets with or without voluntary exercise for 1 week. The rats were

Cognitive testing

It has been shown that both DHA dietary supplementation and exercise have beneficial effects on cognitive function. We have embarked in studies to determine a possible synergistic effect of a DHA-enriched diet and exercise on cognition. Rats were exposed to a regular or DHA-enriched diet, with or without exercise for 7 days, followed by a learning test using the Morris water maze for 5 days. The results demonstrated that the DHA-enriched diet-fed rats performed better as evidenced by lower

Discussion

We have found that a short 12-day exposure to a DHA-enriched diet significantly increases learning ability, and these effects are enhanced by the concurrent application of voluntary exercise. The effects of the DHA diet and exercise on cognitive enhancement were paralleled by elevations in BDNF, and the activated forms of the synaptic proteins CREB, synapsin I, and CaMKII, important for hippocampal learning. Levels of the Akt signaling system were also elevated in proportion to BDNF levels

Acknowledgments

This study was supported by NIH award NS50465.

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      Citation Excerpt :

      DHA is a major modulator of synaptic membrane fluidity and function, which is fundamental for supporting cell signaling 36,37 and synaptic plasticity33,38 that are crucial for brain function and plasticity. We have found that a short 12-day exposure to a DHA-enriched diet significantly increases learning ability, and these effects are enhanced by the concurrent application of voluntary exercise.38 The effects of the DHA diet and exercise on cognitive enhancement were paralleled by elevations in BDNF, and the activated forms of the synaptic proteins CREB, synapsin I, and CaMKII, important for hippocampal learning.

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