Extracellular vesicles shed by macrophages co-cultured with <i>Lactiplantibacillus plantarum</i> No. 14 reduce adipocyte size in mice fed a high-fat diet

Our previous study showed that the intragastric administration of <i>Lactiplantibacillus plantarum</i> No. 14 reduces adipocyte size in white adipose tissue of high-fat diet (HFD)-induced obese mice. We also suggested that the anti-inflammatory effect of <i>L. plantarum</i> No. 14 in white adipose tissues is mediated, at least in part, by circulating exosomes, a type of extracellular vesicle (EV). Therefore, the present study examined whether EVs mediate the adipocyte size-reducing effect of <i>L. plantarum</i> No. 14. Macrophages derived from mouse bone marrow were co-cultured with <i>L. plantarum</i> No. 14, and EVs were isolated from the culture supernatant by ultracentrifugation. C57BL/6J mice fed an HFD were intravenously administered the EVs 5 times a week for 7 weeks. We found that the average adipocyte size was significantly lower in mice administered EVs isolated from the culture supernatant of macrophages co-cultured with <i>L. plantarum</i> No. 14 than in those administered EVs isolated from the culture supernatant of macrophages without co-culture and those administered PBS. In adipocytically differeintiating 3T3-L1 cells, supplementation of EVs isolated from the culture supernatant of macrophages co-cultured with <i>L. plantarum</i> No. 14 reduced adipogenesis, as evidenced by AdipoRed staining. Furthermore, the mRNA levels of adipogenesis-related genes and insulin-induced glucose uptake were also reduced by supplementation with EVs isolated from the culture supernatant of macrophages co-cultured with <i>L. plantarum</i> No. 14. These results suggest that circulating EVs shed by macrophages are involved in the adipocyte size-reducing effect of <i>L. plantarum</i> No. 14 by reducing adipogenesis-related gene expression and glucose uptake in adipocytes.