Gut microbiota alterations are associated with the onset of depression; however, the underlying mechanisms remain unclear. Activation of hippocampal AMP-activated protein kinase (AMPK) in ulcerative c Show more
Gut microbiota alterations are associated with the onset of depression; however, the underlying mechanisms remain unclear. Activation of hippocampal AMP-activated protein kinase (AMPK) in ulcerative colitis mice with disrupted gut microbiota balance produces antidepressant effects. However, the relationship between hippocampal AMPK and antibiotic treatment (ABX)-induced depression-like behavior remains unclear. Therefore, we aimed to investigate whether 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR), an AMPK activator, is associated with the prevention of ABX-induced depression-like behaviors. ABX mice exhibited depression-like behaviors, as evidenced by prolonged immobility and reduced sucrose preference. In the hippocampus of the ABX mice, Iba1 and pro-inflammatory microglial markers were upregulated, whereas brain-derived neurotrophic factor (BDNF), CD206, arginase-1, and interleukin-10 were downregulated. Additionally, levels of AMPK phosphorylation, cAMP response element binding protein (CREB), and tropomyosin-related kinase B (TrkB) were decreased. AICAR administration attenuated these behavioral and molecular alterations. Phosphorylated AMPK was colocalized with the neuronal marker-NeuN-and microglial marker-Iba1. AICAR ameliorated the reduction in hippocampal neuron proliferation and survival and reduced microglial activation-associated morphological changes in the hippocampus. These findings suggest that AICAR administration is associated with antidepressant-like effects, potentially involving enhanced neurogenesis and attenuation of neuroinflammation in the hippocampus of ABX mice. Together, this study highlights the significance of hippocampal AMPK phosphorylation in depression associated with gut microbiota alterations, and suggests a potential target for therapeutic interventions. Show less
Depression is a major global health burden, and current treatments are limited by delayed onset and incomplete efficacy, highlighting the need for novel, mechanism-based therapies. Chronic restraint s Show more
Depression is a major global health burden, and current treatments are limited by delayed onset and incomplete efficacy, highlighting the need for novel, mechanism-based therapies. Chronic restraint stress (CRS) induces behavioral, hormonal, and synaptic changes relevant to depression, but the role of adiponectin signaling remains unclear. Here, we examined whether the adiponectin receptor agonist AdipoRon exerts antidepressant-like effects via brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) signaling in mice subjected to 14 days of CRS. CRS produced anxiety- and depression-like behaviors, elevated plasma corticosterone, reduced circulating adiponectin, and selectively decreased hippocampal adiponectin and adiponectin receptor 2 (AdipoR2), accompanied by reduced PSD-95 and GluA1 in CA3 and the dentate gyrus (DG). AdipoRon treatment (20 mg/kg, days 8-14) prevented behavioral deficits, normalized corticosterone and adiponectin levels, and restored hippocampal AdipoR2, PSD-95, and GluA1 expression in CA3 and DG. AdipoRon also reversed CRS-induced decreases in hippocampal phosphorylated AMPK (p-AMPK), PPARα, BDNF, and phosphorylated TrkB (p-TrkB), with p-AMPK/AMPK and PPARα levels positively correlating with BDNF. Immunofluorescence confirmed BDNF recovery in CA3 and DG. Importantly, pretreatment with the TrkB antagonist ANA-12 abolished the behavioral, hormonal, and molecular effects of AdipoRon, indicating that its actions require BDNF-TrkB activation. These findings suggest that AdipoRon mitigates CRS-induced deficits via hippocampal AdipoR2-AMPK-PPARα-BDNF-TrkB signaling and highlight AdipoR2 as a promising target for depression therapy under chronic stress. Show less