Sexual dimorphism in spatial learning and brain metabolism after exposure to a western diet and early life stress in rats

Prolonged daily intake of Western-type diet rich in saturated fats and sugars, and exposure to early life stress have been independently linked to impaired neurodevelopment and behaviour in animal models. However, sex -specific effects of both environmental factors combined on spatial learning and memory, behavioural flexibility, and brain oxidative capacity have still not been addressed. The current study aimed to evaluate the impact of maternal and postnatal exposure to a high-fat and high-sugar diet (HFS), and exposure to early life stress by maternal separation in adult male and female Wistar rats. For this purpose, spatial learning and memory and behavioural flexibility were evaluated in the Morris water maze, and regional brain oxidative capacity and oxidative stress levels were measured in the hippocampus and medial prefrontal cortex. Spatial memory, regional brain oxidative metabolism, and levels of oxidative stress differed between females and males, suggesting sexual dimorphism in the effects of a HFS diet and early life stress. Males fed the HFS diet performed better than all other experimental groups independently of early life stress exposure. However, behavioural flexibility evaluated in the spatial reversal leaning task was impaired in males fed the HFS diet. In addition, exposure to maternal separation or the HFS diet increased the metabolic capacity of the prefrontal cortex and dorsal hippocampus in males and females. Levels of oxidative stress measured in the latter brain regions were also increased in groups fed the HFS diet, but maternal separation seemed to dampen regional brain oxidative stress levels. Therefore, these results suggest a compensatory effect resulting from the interaction between prolonged exposure to a HFS diet and early life stress.

Automated summary

Prolonged intake of a Western-type diet rich in fats and sugars and exposure to early life stress can negatively impact neurodevelopment and behavior. This study investigates the combined effects of a high-fat and high-sugar diet and early life stress in male and female rats, specifically looking at spatial learning and memory, behavioral flexibility, and oxidative capacity in different brain regions. The results show gender-specific effects, with males performing better on the HFS diet but experiencing impaired behavioral flexibility. Both maternal separation and the HFS diet increased the metabolic capacity and oxidative stress levels in the prefrontal cortex and hippocampus, although maternal separation seemed to dampen oxidative stress levels. These findings suggest a compensatory effect resulting from the interaction between prolonged exposure to a HFS diet and early life stress.