Tectorigenin alleviates diabetic lung injury by restoring gut microbiota and metabolic homeostasis

Diabetes mellitus (DM) significantly increases susceptibility to lung injury, and the lung is increasingly recognized as a target organ in diabetes. Given the critical role of gut dysbiosis in metabolic diseases, this study investigated whether Tectorigenin (TG) could alleviate streptozotocin (STZ)-induced diabetic lung injury through restoration of gut microbial and metabolic homeostasis. We comprehensively assessed lung histopathology, systemic inflammation, gut microbiome, and microbe-associated metabolites. TG treatment significantly reduced lung histopathological damage and suppressed inflammatory infiltration, as shown by decreased TNF-α, IL-1β and IL-6 levels. TG also restored expression of lung tight junction proteins (ZO-1/Occludin). Crucially, TG effectively corrected gut dysbiosis by restoring the Firmicutes/Bacteroidetes ratio, enriching beneficial bacteria including Lactobacillus and Limosilactobacillus (short-chain fatty acid, SCFA producers), while suppressing pathogens such as Enterobacteriaceae and Helicobacter. Metabolomics revealed that TG restored major disrupted microbial metabolic pathways including energy, amino acid and lipid metabolism. TG treatment suppressed pro-inflammatory signaling and reduced cytotoxic metabolites including prostaglandin E2 (PGE2) and 15-hydroxyeicosatetraenoic acid (15-HETE). Consequently, TG effectively inhibited pulmonary oxidative stress through reduced reactive oxygen species (ROS) and elevated Nrf2/GPX1 expression, suppressed macrophage M1 polarization (lower CD86/CD206 ratio), and ameliorated mitochondrial dysfunction (higher PGC-1α and SIRT-1) and ferroptosis. Integrated correlation analysis linked gut microbiota abundance with metabolite profiles and lung injury markers, revealing that TG reversed diabetes-induced Anaerostipes expansion and associated metabolic disturbances. We demonstrate that TG mitigates diabetic lung injury by targeting the gut-lung axis and maintaining metabolic homeostasis, providing a novel intervention strategy for diabetic pulmonary complications.