Fructooligosaccharides-driven metabolism of a defined Lactobacillus probiotic consortium modulates hepatic lipid accumulation in a reductionist in vitro gut microbiota–liver interaction model

Introduction: Metabolic dysfunction-associated steatotic liver disease may be influenced by human gut microbiota-derived metabolites. Fructooligosaccharides (FOS) and probiotic Lactobacillus species have been reported to be associated with metabolic improvements. However, the strain-specific contribution of defined probiotic consortia and the interplay between substrate-driven microbial metabolites and hepatic lipid regulation remain insufficiently characterized. This study aims to investigate whether FOS-driven metabolism of a three-strain Lactobacillus consortium (L. plantarum PBS067, L. acidophilus PBS066, and L. reuteri PBS072) modulates hepatocyte lipid accumulation in steatotic HepG2 cells within a reconstructed reductionist in vitro human gut microbiota model.Methods: A previously validated minimal core community, representing metabolic functions of the human gut microbiota, was supplemented with the probiotic consortium and cultured in the presence of FOS with an average degree of polymerization ~10. Lactobacillus strain growth and modulation, transcriptional activation of FOS-related genes, and short-chain fatty acid (SCFA) metabolic profiles were characterized. Microbiota-derived metabolites were then tested on palmitate-induced steatotic HepG2 cells.Results and discussion: FOS supported growth of both probiotic and minimal core members in a strain-dependent manner within the community, with higher growth levels of L. plantarum PBS067 and L. reuteri PBS072. RT-qPCR analyses of sacA, scrB, and sacK1 genes revealed species-specific transcriptional activation and context-dependent regulation of FOS utilization pathways. Microbial metabolic profiling showed production of SCFAs and organic acids typical of carbohydrate fermentation. Treatment of steatotic HepG2 cells with these metabolites significantly reduced intracellular lipid accumulation and down-regulated Cd36 gene encoding a key fatty acid transporter involved in palmitic acid-induced steatosis. These findings suggest that FOS-driven microbial metabolism within a defined Lactobacillus consortium could be associated with hepatocyte lipid uptake under controlled in vitro conditions, highlighting the interplay among microbial transcriptional activation and their metabolic profiles.