Abstract:The effects of live and heat-inactivated Bifidobacterium longum subsp. infantis B79 on the immune pathways that mediate adipogenesis and lipid metabolism of 3T3-L1 preadipocytes were studied. The experimental groups were treated with appropriate concentrations of live and heat-inactivated B79 suspensions，with peptidoglycan as the positive control and RPMI1640 medium as the blank control. After co-culture with RAW264.7 cells，the cytokine expression and secretion were measured. The supernatant of the co-culture system was centrifuged and then used to intervene in 3T3-L1 cells at appropriate ratios，and the expression levels of lipid metabolism-related genes and the secretion of adiponectin were determined. After Oil Red staining，the adipogenesis of 3T3-L1 cells was observed under a microscope and the OD490 value of Oil Red O extraction was measured. The results showed that compared with the blank control group，the live and heat-inactivated B79 groups showed significantly activated immune function of RAW264.7 cells and significantly increased expression and secretion of interleukin-6（IL-6），interleukin-10（IL-10），tumor necrosis factor-α（TNF-α），and interleukin-1β（IL-1β）. After intervention with the co-culture supernatant，the expression of genes involved in adipogenesis and lipid accumulation in the experimental group was significantly inhibited，and the secretion of adiponectin was significantly reduced. The secretion of adiponectin and the OD490 value were the lowest in the heat-inactivated B79 group. The live and heat-inactivated cells of B. longum subsp. infantis B79 significantly activated the immune regulatory function of macrophages，thereby inhibiting the adipogenesis and lipid metabolism of preadipocytes. Moreover，heat-inactivated B79 demonstrated more stable effect，outperforming live B79 in inhibiting adipogenesis.