Abstract
Unsaturated fatty acids (UFAs), including omega-3, omega-6 polyunsaturated and omega-9 monounsaturated fatty acids, are essential components and modulators of neuromembranes and may affect various aspects of physiology and cognition. UFAs are suggested to positively affect spatial learning and memory and also to diminish the negative consequences of physiological stress on cognitive abilities. Due to pronounced sex differences in neurophysiological functions, we hypothesize that these UFA-related effects might differ between male and female individuals. We therefore determined the effects of dietary UFAs on cognitive performances in a radial-Y-maze in male and female guinea pigs in relation to saliva cortisol concentrations, a marker for physiological stress. Animals were assigned to four treatment groups and maintained on diets enriched in either chia seeds (omega-3), walnuts (omega-6), or peanuts (omega-9), or a control diet. Female learning abilities throughout a three-day learning phase were positively affected by omega-3 and omega-9, as determined by a decreasing latency to pass the test and the number of conducted errors, while males generally showed distinct learning abilities, irrespective of the diet. A sex difference in learning performances was found in the control group, with males outperforming females, which was not detected in the UFA-supplemented groups. This was paralleled by significantly increased saliva cortisol concentrations in males throughout the cognition test compared to females. Three days after this learning phase, UFA-supplemented males and all females showed unchanged performances, while control males showed an increased latency and therefore an impaired performance. These results were corroborated by pronounced differences in the plasma UFA-status, corresponding to the different dietary treatments. Our findings indicate sex-specific effects of dietary UFAs, apparently enhancing spatial learning abilities only in females and protecting males from long-term memory impairment, while male learning abilities seem to be more strongly affected by an acute physiological stress response to the maze task.
Highlights
Unsaturated fatty acids (UFAs) are important components of neuronal cell membranes and promote several brain-mediated functions by influencing the membrane fluidity and myelinization
The conversion of plasma-derived ALA and LA to the respective LC-PUFAs in the brain is very low, relatively little amounts of the dietary precursors are required for a sufficient metabolic synthesis of the important LC-PUFAs [7]
The three cognitive parameters during the learning phase were analyzed by applying linear mixed effect models (LMEs) with ‘group’, ‘sex’, and ‘day’ as fixed factors and single individuals as random factors to control for the repeated measurements
Summary
Unsaturated fatty acids (UFAs) are important components of neuronal cell membranes and promote several brain-mediated functions by influencing the membrane fluidity and myelinization. The impact of n-6 fatty acids on cognitive functions is less studied They seem to evoke opposite effects, namely impaired learning abilities associated with higher n-6 LC-PUFA concentrations in the brain [15]. In socially confronted guinea pigs, diets high in ALA and LA were effective in keeping cortisol concentrations at lower levels and increasing locomotive activity compared to untreated control animals [21] These effects were the same in males and females. We determined and compared the effects of diets high in n-3, n-6, and n-9 UFAs on cognitive performances in a radial-Y-maze in relation to saliva cortisol concentrations in male and female guinea pigs
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