Luteolin rescues high-fat diet-induced hippocampal mitochondrial oxidative stress and cognitive decline by regulating gut microbiota-kynurenine-aryl hydrocarbon receptor axis.

High-fat diet (HFD)-induced gut dysbiosis precipitates hippocampal mitochondrial oxidative stress, a pivotal driver of synaptic failure and cognitive decline. However, the molecular conduits linking intestinal microbial shifts to cerebral redox imbalance remain poorly defined, limiting therapeutic strategies. Here, we show that luteolin attenuates HFD-induced cognitive impairment in association with modulation of the gut microbiota-kynurenine (Kyn)-aryl hydrocarbon receptor (AhR) axis and improved mitochondrial redox homeostasis. Luteolin treatment ameliorated HFD-induced memory deficits and metabolic abnormalities in mice, effects that were markedly reduced after gut microbiota depletion and were transmissible via fecal microbiota transplantation. Consistent with this pathway, luteolin suppressed HFD-induced expansion of Proteobacteria (e.g., Escherichia coli), diminished intestinal lipopolysaccharide (LPS) leakage, and normalized colonic indoleamine 2,3-dioxygenase 1 (IDO1) expression. Consequently, luteolin reduced peripheral and hippocampal Kyn accumulation, thereby restricting AhR nuclear translocation and preventing the aberrant transcription of AhR-target genes implicated in mitochondrial respiratory chain disruption. Functionally, luteolin restored hippocampal mitochondrial bioenergetics, attenuated pathological reactive oxygen species (ROS) overload, and preserved synaptic long-term potentiation (LTP). The protective efficacy of luteolin against mitochondrial oxidative insult and cognitive decline was phenocopied by AhR inhibition and abrogated by exogenous Kyn supplementation. Collectively, our findings identify the gut Proteobacteria-Kyn-AhR signaling axis as an important contributor to hippocampal mitochondrial oxidative stress in HFD-challenged brains. Luteolin emerges as a promising microbiota-targeted antioxidant intervention that safeguards cognitive function by rectifying this gut-brain redox relay.