Research reportEffect of high-fat diets on mood and learning performance in adolescent mice

•High fat diets trigger a rapid antidepressive-like behaviour.•Cognitive deficits induced by high fat diets appear after 4 weeks of treatment.•Memory impairments induced by high fat diets are not related to the alleged obesity-induced depression neither to anxiety-like behaviors.

Recent studies point to dietary factors as important effectors in the brain and epidemiological studies suggest a direct relationship between mood and anxiety disorders, cognitive impairment and obesity. Nevertheless the link between the consumption of high-fat diets (HFD) and emotional disorders still remains unclear. This issue is of particular interest during adolescence, which is an important period for shaping learning and memory acquisition that can be particularly sensitive to the detrimental effects of HFD. Otherwise, major depressive disorder and anxiety crisis often emerge in adolescence. In the current study we have characterized in adolescent mice i) the onset of HFD-induced memory impairment using the novel location recognition (NLR) paradigm, and ii) the effect of HFD on depression- and anxiety-related behaviors by using the forced swimming and the elevated plus maze tests, respectively. Here we report that memory impairments induced by HFD were already perceptible after 4-weeks HFD whereas HFD induced already antidepressant-like effects after 48-h, that remained after long-term treatment (8 weeks). No effects in anxiety were found. These data indicate that the antidepressant-like effect of HFD is independent of memory deficits as it was already present after 48-h HFD, while no effects in memory were still observed at this time.