Impact of enriched environment on production of tau, amyloid precursor protein and, amyloid-ß peptide in high-fat and high-sucrose-fed rats.

OBJECTIVE: The Western-type diet is associated with an elevated risk of Alzheimer's disease and other milder forms of cognitive impairment. The aim of the present study was to investigate the effects of the environmental enrichment on amyloid and tau pathology in high-fat and high-sucrose-fed rats. METHODS: In total, 40 adult male rats were categorised into two main groups according to their housing conditions: enriched environment (EE, n=16) and standard housing condition (n=24). The groups were further divided into five subgroups that received standard diet, high-fat diet, and high-sucrose diet. We performed the analysis of amyloid ß-peptide (Aß) (1-40), Aß(1-42), amyloid precursor protein (APP), and tau levels in the hippocampus of rats that were maintained under standard housing conditions or exposed to an EE. RESULTS: The EE decreased the Aß(1-40), Aß(1-42), APP, and tau levels in high-fat and high-sucrose-fed rats. CONCLUSION: This observation shows that EE may rescue diet-induced amyloid and tau pathology.

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 the HFD-induced cognitive deficits, but the exact mechanism is 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: Male Wistar 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 chow for 4weeks. We used 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-pituitary-adrenal axis and hippocampal corticosteroid receptor levels.

Role of calcium in contractile responses of calf cardiac vein during cooling.

The effects of cooling (to 28 °C) were studied on the responses induced by carbachol (10(-9) - 3 × 10(-4) M) and serotonin (5-HT, 10(-8) - 3 × 10(-4) M) in calf cardiac vein preparations and the role of calcium ions in these effects were analyzed. Ring preparations of veins obtained from calf hearts were suspended in organ baths containing 25 mL of Krebs-Henseleit solution, maintained at 37 °C and continuously gassed with 95%O(2)-5%CO(2). After a resting period, preparations were contracted with carbachol (10(-9) - 3 times; 10(-4) M) and 5-HT (10(-8) - 3 times; 10(-4) M) at 37 °C. The same protocol was repeated at 28 °C after the preparations were allowed to equilibrate at this temperature for 60 min. In order to analyze the role of calcium ions (Ca(2+)) in the cooling-induced vascular response, concentration-response curves to carbachol and 5-HT were obtained in the presence of verapamil (10(-6) M), caffeine (3 times; 10(-4) M), and Ca(2+ )free medium in the presence of EGTA at 28 °C. During cooling to 28 °C, the EC(50) values, to carbachol and 5-HT were significantly higher than at 37 °C. Cooling to 28 °C in the presence of verapamil, caffeine or Ca(2+ )free medium in the presence of EGTA increased the EC(50) values, to both carbachol and 5-HT. These results suggest that Ca(2+) plays an essential role in the cooling-induced changes of calf cardiac vein preparations treated with carbachol and 5-HT.