Environmental Enrichment May Mitigate Dexamethasone-Induced Changes in the Glycemic Curve

Abstract

Previously, we demonstrated that administration of dexamethasone (Dex) at a dose of 1 mg/kg, 24 h before an ulcerogenic stimulus exerts a pro-ulcerogenic effect, accompanied by disturbances in carbohydrate metabolism. In the present study, we examined the influence of housing conditions – standard conditions (SC), social isolation (SI), and environmental enrichment (EE) conditions – on the Dex-induced changes in carbohydrate metabolism, as well as on hematological parameters. Experiments were conducted with male rats during the winter period. Starting from the age of 30 days, the animals were housed for 6 weeks under SC, SI, or EE conditions. Dex (1 mg/kg, intraperitoneal) or its vehicle (control) was administered 24 h prior to the glucose tolerance test (GTT), after which food was removed. Following the GTT, indomethacin (IM) was administered at an ulcerogenic dose; 4 h later, the rats were decapitated, and blood samples were collected to assess corticosterone levels and hematological parameters, including calculation of the neutrophil-to-lymphocyte ratio (NLR). Alongside the IM administration experiment, a control experiment including vehicle administration was performed according to the same protocol, in which the vehicle of IM was administered instead of IM itself. Administration of glucose during the GTT led to the increase in the blood glucose levels, reaching maximum (peak) at 30 min in all control, previously fasted animals (SC, SI, EE groups). Beginning at 60 min, the glucose levels gradually declined in all control groups, returning to the baseline only in the control rats from the EE group. In the rats maintained under SC conditions, pretreatment with Dex resulted in the reduction in the peak of the glycemic curve, accompanied by the corresponding decrease in the area under the curve (AUC) and reduced rate of decline in the blood glucose levels compared with the respective control group. In the rats housed under EE condition, resistance to the effects of Dex was observed, as evidenced by the absence of changes in the glycemic curve peak, AUC, or rate of decline in the blood glucose levels relative to the corresponding control group. The control rats from the SI group exhibited lower values of the glycemic curve peak, AUC, and rate of decline in the blood glucose levels than the rats from the SC and EE groups. Administration of Dex did not produce any further changes in these parameters. Dex administration induced a marked increase in the NLR in all groups (SC, SI, and EE), both in the rats treated with IM and in the animals receiving its vehicle. Taken together, these findings indicate that a single administration of Dex (1 mg/kg; 24 h after injection) to the rats from the SC group could alter glycemic response and increase NLR. Housing under EE conditions prevents the Dex-induced changes in the glycemic curve.