Apigenin promotes neuronal norepinephrine release via GPR30/PLCβ1-Ca2+-Syt1 signaling to enhance astrocytic lactate and exert neuroprotection in D-galactose-induced cognitive impairment

Objective AD, a prevalent neurodegenerative disorder clinically defined by progressive cognitive impairment, is pathologically featured by early dysfunction of the locus coeruleus, depletion of noradrenergic (NE) neurons, and dysregulated astrocytic glycogen metabolism, which collectively compromise patients’ daily functioning. Although Api, a common phytoestrogen, has shown therapeutic efficacy in diverse diseases, its role and mechanism in AD remain unexplored. Methods To address this gap, we evaluated the protective effects of Api against D-gal-induced cognitive deficits through behavioral and histomorphological assessments. Untargeted metabolomics was performed to profile metabolic alterations in the locus coeruleus (LC), complemented by targeted metabolomics focusing on specific pathways. Putative targets were predicted by molecular docking and verified via cellular thermal shift assay (CETSA), while molecular biology approaches were adopted to elucidate the underlying signaling cascades. Results Api significantly ameliorated D-gal-induced cognitive impairment and increased hippocampal NE and lactate levels with enhanced neuronal activity. Metabolomics indicated that Api regulates energy metabolism pathways including TCA cycle, amino acid metabolism, glycolysis/gluconeogenesis, and glutathione metabolism. Specifically, Api elevated NE and lactate in the LC. GPR30 was identified and validated as the key target via molecular docking and CETSA, showing strong binding affinity. Mechanistically, Api activates GPR30 on noradrenergic neurons to regulate PLCβ1-Ca 2+ -Syt1 signaling, promoting NE release, which in turn drives astrocytic glycogenolysis and lactate production, thereby relieving neuronal energy deficits. Conclusion Collectively, this study not only clarifies the PLCβ1-Ca 2+ -Syt1-dependent mechanism of Api in aging-related cognitive impairment, but also highlights NE and lactate elevation as a promising therapeutic approach.