Exendin-4 improves behaviorial deficits via GLP-1/GLP-1R signaling following partial hepatectomy

Abstract

Recent studies indicate that glucagon-like peptide 1 (GLP-1) receptor (GLP-1R) agonists exhibit neurotrophic and neuroprotective effects. The aim of this study was to explore whether the GLP-1R agonist exendin-4 can alter surgery-induced behavioral deficits and exert neuroprotective effects via the activation of the hippocampal GLP-1/GLP-1R pathway. 120 male Sprague-Dawley rats (aged 18–20 months old) were randomly divided into four groups: control group, exendin-4 group, surgery group, and surgery + exendin-4 group. The animals received either exendin-4 (5 µg/kg/day) or saline intra-peritoneally for 14 days, and then were subjected to partial hepatectomy 24 h after the last injection. Behavioral changes were evaluated with Morris Water Maze and Open field testing on postoperative days 7 and 14. The levels of IL-1β, NF-κB, Iba-1, Synaptophysin, GLP-1/GLP-1R, GSK-3β, p-GSK-3β (Ser9), p-Tau (Ser396), and p-Tau (Ser202/199) in the hippocampus were measured at the same time point. Surgical trauma induced an exacerbated spatial learning and memory impairment, increased the levels of depressive performance, and enhanced hippocampal NF-κB and IL-1β expression in the aged rats on postoperative day 7. A corresponding decline in GLP-1R was also found following surgical challenge on postoperative day 7. Exendin-4 treatment partly reversed surgery-induced postoperative behavioral impairment, downregulated the levels of NF-κB and IL-1β, ameliorated tau hyperphosphorylation and enhanced the activity of p-GSK-3β (Ser9). Together, the downregulation of GLP-1R exacerbated surgery-induced behavior deficits. Exendin-4 treatment attenuated these effects by inhibiting neuroinflammation and tau hyperphosphorylation. These findings suggest that pretreatment with exendin-4 is a potential adjuvant for preventing surgery-induced behavioral deficits.