Prenatal N-acetyl-cysteine prevents social anxiety and modulates hippocampal inflammatory-and plasticity-related genes in adolescent mice prenatally exposed to a high-fat diet

High-fat diet (HFD) consumption during pregnancy is associated with increased oxidative stress (OS) and low-grade chronic inflammation, and may affect fetal brain development, setting the stage for increased vulnerability to mood disorders later in life [1,2]. However, the biological mechanisms underlying the negative long-term effects of maternal HFD are poorly understood. N-acetyl-cysteine (NAC) is a promising antioxidant compound [3] that has revealed beneficial effects in the treatment of psychopathology. The aim of this study was to investigate inflammation, OS and hypothalamic-pituitary-adrenal (HPA) axis reactivity in a mouse model of maternal HFD as potential mechanisms affecting brain development and emotional behavior in the offspring. The prenatal NAC treatment was tested to prevent the negative effects of maternal HFD on adolescent offspring, an age of main vulnerability for the onset of psychopathologies. Female C57BL/6N mice were fed either HFD (energy 5.56 kcal/g, fat 58%, carbohydrate 25.5% and protein 16.4%) or control diet (CD, energy 4.07 kcal/g, fat 10.5%, carbohydrate 73.1% and protein 16.4%) before and during pregnancy (13 weeks); after 5 weeks on diets, half of them received NAC (1g/kg) for 8 weeks, until delivery. Emotionality and social behavior of male and female adolescent offspring (35-45 days) were assessed through the elevated plus maze (EPM) and the social interaction test (SIT); HPA axis functionality was assessed measuring plasma corticosterone levels by ELISA under basal conditions and following an acute stress. Gene expression levels of CD68, Bdnf and Nrf2 were measured in hippocampus as markers of microglial activation, brain plasticity and antioxidant capacity respectively by RealTime PCR. Data were analyzed using parametric analysis of variance (ANOVA) with diet (HFD vs. CD), treatment (NAC vs. WATER), sex (females vs. males) as between subjects factors. Post hoc comparisons were performed using the Tukey’s test. Prenatal exposure to HFD affected sociability reducing social behaviors (p<0.01, post hoc HFD-WATER vs. CD-WATER p<0.05) in the SIT and reduced exploration in the EPM (frequency of crossings p<0.01; head dipping p=0.0292; wall-rearing p=0.0255). As for the HPA axis functionality, reduced levels of basal corticosterone were found in HFD males (p<0.01, post hoc HFD-WATER vs. CD-WATER p<0.05). Moreover, prenatal HFD decreased hippocampal Bdnf levels in females (p<0.01, post hoc HFD-WATER vs. CD-WATER p<0.05), while males showed increased CD68 expression (p<0.01). Prenatal NAC administration prevented social anxiety, restored HPA axis basal activity in males and Bdnf levels in females (p<0.01, post hoc HFD-WATER vs. HFD-NAC p<0.05). In addition, hippocampal levels of Nrf2 resulted increased in both males and females (p<0.01), suggesting that NAC may act, at least in part, through an upregulation of this important regulator of brain antioxidant defenses. Overall, these data showed that maternal HFD induces long-term negative effects on the adolescent offspring, affecting brain, neuroendocrine system and emotional/social behavior. These effects are partially prevented by prenatal administration of NAC suggesting that immune and OS pathways may play an important role in fetal programming of mental disorders. Funding: ERANET-NEURON-JTC-2018 Project EMBED