To explore relationships between the anti-obesity effect and modulation of gut microbioata by APS in high-fat diet (HFD)-fed mice.Methods:1 A total of 50 male C57bl/6J mice were randomly divided into five groups including control group (Con), HFD group, and three APS groups with low, middle and high dosages (2 %, 4 %, 8 % APS mixed in HFD). All animals were fed with corresponding diet for consecutive eight weeks during which their body weight was measured weekly. At the end of the experiment, fecal samples were collected for analysis of gut microbiota by 16S rDNA sequencing approach. 2 To investigate the contribution of gut microbiota to body weight reduction of APS, two groups of mice (n=5/each group) were transplanted with intestinal bacteria from mice that were fed with or without APS (2 % APS in HFD). The receiver mice were designated as HFD_R and APS_R, respectively. The receiver mice were fed with chow diet for consecutive eight weeks first, and then switched to HFD for another four weeks.Results:APS effectively suppressed the HFD-induced obesity formation, attenuated the hepatic steatosis, decreased hepatic TG level, improved insulin sensitivity, restored the balance of gut microbiota in HFD-fed mice by increasing the relative abundance of Bacteroidetes and Firmicutes, and reducing the abundance of Proteobacteria bacteria. Moreover, the anti-obesity effect of APS could be transferred to mice that were transplanted with intestinal bacteria from APS-fed mice in the context of HFD, but not chow diet.Conclusion:APS could inhibit the HFD-induced obesity formation, at least partially, by modulating gut microbiota.