GV-971 Ameliorates Chronic Restraint Stress-Induced Depression-like Phenotypes Accompanied by Reshaping of the Microbiota-Gut-Brain Axis

Depression is increasingly linked to microbiota-gut-brain axis dysfunction, yet current monoaminergic antidepressants show limited efficacy. This study investigated the therapeutic potential and underlying mechanisms of GV-971, a marine-derived oligosaccharide, in a chronic restraint stress (CRS) mouse model. We first established that 8 h of daily restraint for 4-8 weeks induces a stable depression-like phenotype characterized by behavioral despair and significant reduction in peripheral monoamine neurotransmitters (5-HT and norepinephrine). GV-971 treatment robustly attenuated CRS-induced depression- and anxiety-like behaviors, restored hippocampal serotonin levels, reduced elevated plasma corticosterone concentrations, and ameliorated CRS-induced adrenal cortical hyperplasia. Mechanistically, GV-971 significantly suppressed neuroinflammation by inhibiting microglial hyperactivation in the prefrontal cortex and hippocampus. Concurrently, it repaired intestinal barrier dysfunction, evidenced by reduced permeability, restored mucosal integrity, and recovered goblet cell numbers. Crucially, integrated shot-gun metagenomics and plasma metabolomics revealed that GV-971 not only reshaped microbial taxonomy but also functionally recalibrated the gut ecosystem. It enriched beneficial taxa (e.g., Bifidobacterium pseudolongum, Bacteroides uniformis) and specific metabolic pathways, leading to increased short-chain fatty acids (valeric and caproic acids) and a significant reduction in plasma levels of tryptophan-kynurenine pathway metabolites, specifically the neurotoxic compounds kynurenine and quinolinic acid. Fecal microbiota transplantation (FMT) from GV-971-treated donors partially recapitulated the antidepressant and gut-protective effects in CRS recipients, confirming a causal role for the remodeled microbiota. Collectively, GV-971 exerts antidepressant effects by coordinately remodeling the gut microbiota, normalizing tryptophan and SCFA metabolism, restoring gut barrier integrity, and dampening central neuroinflammation, supporting its potential as a novel gut-brain axis-targeted therapy for depression.