Liraglutide improves cognitive impairment via the AMPK and PI3K/Akt signaling pathways in type 2 diabetic rats

Liraglutide is a type of glucagon-like-peptide 1 receptor agonist, which has been reported as a novel type of antidiabetic agent with numerous benefits, including cardiovascular and neuroprotective effects. To the best of our knowledge, few studies to date have reported the potential mechanism underlying the neuroprotective effects of liraglutide on rats with type 2 diabetes mellitus (T2DM). The present study aimed to investigate the neuroprotective actions of liraglutide in diabetic rats and to determine the mechanisms underlying these effects. A total of 30 male T2DM Goto-Kakizaki (GK) rats (age, 32 weeks; weight, 300-350 g) and 10 male Wistar rats (age, 32 weeks; weight, 300-350 g) were used in the present study. Wistar rats received vehicle treatment, and GK rats randomly received treatment with vehicle, low dose of liraglutide (75 mu g/kg) or high dose of liraglutide (200 mu g/kg) for 28 days. Cognitive deficits were evaluated using the Morris water maze test. The expression levels of phosphoinositide 3-kinase (PI3K), protein kinase B (Akt), phosphorylated (p)-Akt, AMP-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), Beclin-1, microtubule-associated protein light chain 3 (LC)-3 II, caspase-3, B-cell lymphoma 2 (Bcl-2)-associated X protein and Bcl-2 were assessed by western blot analysis. The results demonstrated that diabetic GK rats exhibited cognitive dysfunction, whereas treatment with liraglutide alleviated the learning and memory deficits, particularly in the high-dose liraglutide group. The expression levels of Beclin-1 and LC-3 II were decreased in GK rats; however, this decrease was alleviated in the presence of liraglutide. Liraglutide also reversed T2DM model-induced increases in mTOR, and decreases in p-AMPK, PI3K and p-Akt expression, and modulated the expression of apoptosis-associated proteins. Furthermore, the administration of liraglutide inhibited apoptosis and exerted a protective effect against cognitive deficits via the activation of autophagy. In conclusion, the protective effects of liraglutide may be associated with increased mTOR expression via activation of the AMPK and PI3K/Akt signaling pathways.