Lacticaseibacillus paracasei CM6 postbiotics alleviate SO/SP-induced hepatic lipotoxicity in HepG2 cells: Insights into lipid-redox homeostasis, glutamate metabolism and PLA2G4A-dependent lysophospholipid remodeling.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by metabolic imbalances and lipid-induced cellular toxicity. Although postbiotics are emerging as reliable functional food ingredients for metabolic disorder management, molecular mechanisms underlying their hepatoprotective effects remain incompletely elucidated. In this study, we integrated microbial whole-genome sequencing with paired intracellular and extracellular metabolomic profiling to explore the regulatory effects of the Lacticaseibacillus paracasei CM6 postbiotic against sodium oleate/sodium palmitate (SO/SP)-induced lipotoxicity in HepG2 cells. Our results showed that CM6 postbiotic intervention significantly reduced intracellular triglyceride (TG) levels. Genomic analysis pinpointed key genes responsible for lipid regulation (bsh and ohyA) and involved in antioxidant defense and amino acid metabolism (gadC, gshA, proB/A) in the CM6 strain, suggesting its inherent potential to produce bioactive effectors. The CM6 postbiotic treatment significantly suppressed SREBF1-driven de novo lipogenesis (particularly ACACA) and enhanced fatty acid β-oxidation (marked by PPAR-α and CPT1A), in parallel with altered expression of key molecules in the FXR/AMPK signaling pathway. Furthermore, CM6 treatment significantly reduced the accumulation of lysophospholipids (LPCs, LysoPE), which was associated with downregulated PLA2G4A expression. Importantly, HepG2 cells treated with the CM6 postbiotic exhibited enhanced uptake of extracellular glutamate to support intracellular glutathione (GSH) biosynthesis, contributing to the clearance of reactive oxygen species (ROS) associated with lipotoxicity. Collectively, our findings suggest that the CM6 postbiotic alleviates SO/SP-induced hepatic lipotoxicity and steatosis-like phenotypes via concurrent modulation of lipid metabolism, cell membrane defense, and redox homeostasis, representing its potential as a novel bioactive dietary candidate and targeted nutritional strategy for MASLD management.