Restraint-Induced Glucocorticoid Receptor Downregulation is Dysregulated in High Fat Diet-Fed Rats Likely from Impairment of miR-142-3p Expression in the Hypothalamus and Hippocampus

Abstract

High fat diet (HFD) induces dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis function. The HPA axis is controlled by the feedback of glucocortioids on the hypothalamus, hippocampus and pituitary. At least three miRNAs (miR-101a, miR-124, miR-142-3p) have been reported to suppress glucocorticoid receptor (GR) translation. Because their relation to stress-induced downregulation of GR expression and dysregulation of its expression in HFD feeding are unclear, we studied to identify which miRNAs are involved in restraint-induced downregulation of GR expression in the hypothalamus and hippocampus, and to compare the basal and restraint-modified miRNA expressions in these tissues in HFD-fed rats. Rats exposed to HFD were divided into two groups, HFD-induced obese (HFD-ob) and obesity resistant (HFD-obR) rats. Basal plasma corticosterone concentrations were higher in HFD-ob than in standard chow-fed (SC) rats and in HFD-obR. Restraint-induced elevation of plasma corticosterone was higher in HFD-obR than in the other groups. Restraint decreased GR expressions and increased miR-142-3p expression in the hypothalamus and hippocampus without affecting others expressions. miR-142-3p expressions in both areas were increased by dexamethasone and restraint-induced miR-142-3p expression was blocked in adrenalectomy. The basal expression of GR or miR-142-3p expression in both areas of HFD-fed rats did not differ from those of SC, and restraint induced no changes in GR or miR-142-3p expression in both areas in HFD-ob and HFD-obR. These results suggest that impairment of glucocorticoid-induced increase in miR-142-3p may be involved in dysregulation of stress-induced downregulation of GR expression in the hypothalamus and hippocampus of HFD-fed rats.