Effect of semaglutide and empagliflozin on cognitive function and hippocampal phosphoproteomic in obese mice

Abstract

Objective: Based on the 4D label-free phosphoproteomic technique, we examined the differences in cognitive function and hippocampal phosphorylated protein expression in high-fat diet-induced obese mice after the intervention of semaglutide and empagliflozin.Methods: Thirty-two C57BL /6JC male mice were assigned randomly to control group (group C), high-fat diet group (group H), high-fat diet + semaglutide group (group S) and high-fat diet + empagliflozin group (group E). group S received 30 nmol/kg/d bodyweight of semaglutide intraperitoneally, group E received 10 mg/kg/d bodyweight of empagliflozin via gavage, and groups C and H received equal amounts of saline intraperitoneally. At the end of treatment, the mice were assessed for cognitive function using the Morris water maze (MWM), and serum fasting glucose, lipids, and inflammatory parameters were measured. The 4D label-free phosphoproteomics method was used to screen the differentially phosphorylated proteins and loci in hippocampal tissues of mice in different treatment groups, and bioinformatics was used to analyze the biological processes, signaling pathways, and related PPI network analysis of these differentially phosphorylated proteins.Results: high-fat diet-induced obese mice showed a prolonged escape latency, reduced percentage of swimming time in the target quadrant, and decreased number of crosses, whereas the above indicators were restored after treatment with semaglutide and empagliflozin. Empagliflozin outperformed semaglutide in terms of improving cognitive function, however, have similar effects on glucolipid metabolism and anti-inflammation. The phosphoproteomic results showed 20,493 unique phosphorylated peptides, representing 21,239 phosphorylation sites and 4,290 phosphorylated proteins. The 442 differentially expressed phosphoproteins were up-regulated in the H/C group, whereas 402 were down-regulated. In the S/H group, 686 differentially expressed phosphorylated proteins were up-regulated while 398 were down-regulated. While in the E/H group, 955 differentially expressed phosphorylated proteins were up-regulated while 597 were down-regulated. Further analysis revealed that these differentially phosphorylated proteins are jointly distributed in signaling pathways such as dopaminergic synapses and axon guidance and that they were involved in biological processes like neuronal projection development, synaptic plasticity, and axonogenesis. Notably, the key factors CACNA1D, CACNA1A, and CACNA1B were all found to be involved in the dopaminergic synapse pathway, and their expression was up-regulated by semaglutide and empagliflozin.