Environmental enrichment reverses cognitive impairments provoked by Western diet in rats: Role of corticosteroid receptors

Aims: Previous studies demonstrated that the Western diet (WD), which is rich in saturated fat (HFD) and refined sugar (HSU), is related to the impairments of hippocampus-dependent learning and memory and forebrain synaptic plasticity in rodents. The environmental enrichment (EE) has been shown to enhance learning and memory in theHFD-induced cognitive deficits, but the exact mechanismis still not clearly understood. Therefore, the present study aimed to clarify the effects of the EE on spatial memory in WD-fed rats, and to analyze the potential role of corticosteroid receptors in the EE conditioning. Main methods: MaleWistar albino rats were housed in either an enriched or standard environment and fed with the HFD (35% of energy as fat), HSU (100% of carbohydrate as sucrose) or standard rat chowfor 4 weeks. Weused the Morris' water maze test (MWM) to assess the learning and memory performance, and measured plasma levels of corticosterone (CORT) and adrenocorticotropic hormone (ACTH), as well as glucocorticoid (GR) and mineralocorticoid receptor (MR) levels in the hippocampus. Key findings: The results showed that HFD-fed rats displayed poorer learning and memory performance evaluated with MWM than controls. The EE reversed the cognitive deficits caused by the HFD. In addition, the EE resulted in an increase of GR and MR levels without affecting plasma CORT and ACTH concentrations. Significance: Based on these findings, it could be suggested that the EE plays an important role in amelioration of the HFD-induced cognitive impairments, but this intervention is independent of the hypothalamic-pituitaryadrenal axis and hippocampal corticosteroid receptor levels. (C) 2016 Elsevier Inc. All rights reserved.