Monosodium glutamate induces hypothalamic–pituitary–adrenal axis hyperactivation, glucocorticoid receptors down-regulation, and systemic inflammatory response in young male rats: Impact on miR-155 and miR-218

Abstract

Young children are attracted to flavored foods with enhancers, particularly monosodium glutamate (MSG). Experimental studies have proven that MSG can alter the hypothalamic–pituitary–adrenal (HPA) axis response in neonates. We, therefore, investigated the modulation of microRNAs (miRNAs) by dietary MSG and its association with the stimulation of the HPA axis and inflammatory response in young male rats. One-month-old male rats were fed chow enriched with MSG (3 g/kg) for 16 weeks. Feeding MSG to rats markedly up-regulated hypothalamic miR-218, Toll-like receptors-4, and nuclear factor-kB but down-regulated miR-155 and glucocorticoid receptors (GR). In addition, it triggered a remarkable elevation in adrenocortical lipid peroxidation and depletion of antioxidants. These changes were coupled with increased plasma levels of the HPA axis hormones, comprising corticotropin-releasing hormone, adrenocorticotropic hormone, corticosterone levels, and serum pro-inflammatory cytokines. Taken together, current findings indicated that MSG caused an activation of the HPA axis, a down-regulation of GRs, and a systemic inflammatory response. These disturbances were associated with modulating hypothalamic miRNAs, encompassing miR-218 and 155.