determine the relative contributions of gut microbiota in modulating the chronotoxicity of APAP

Acetaminophen (APAP) induced hepatotoxicity is a leading cause of acute liver failure worldwide. It is well established that the liver damage induced by acetaminophen exhibits diurnal variation. However, the detailed mechanism for the hepatotoxic variation is not clear. Here we aimed to determine the relative contributions of gut microbiota in modulating the chronotoxicity of APAP. Male Balb/C mice were treated with or without antibiotics and orally administrated a single dose of APAP (300 mg/kg) at ZT0 (8:00 AM) and ZT12 (8:00 PM). In agreement with previous findings, hepatic injury was markedly enhanced at ZT12 compared with ZT0. Interestingly, upon antibiotics treatment, ZT12 displayed protection against APAP hepatotoxicity similar to ZT0, which could not be explained by food intake. Moreover, mice that received the cecal content from ZT12 showed more severe liver damage than mice that received the cecal content from ZT0. 16S sequencing data revealed significant differences in the cecal content between ZT0 and ZT12 in the compositional level. Furthermore, metabolomics analysis showed that the gut microbial metabolites were also different between ZT0 and ZT12. Specifically, the level of 1-phenyl-1,2-propanedione (PPD) was significantly higher at ZT12 than ZT0. Treatment with PPD alone did not cause obvious liver damage. However, by decreasing hepatic GSH, PPD synergistically enhanced APAP induced hepatic injury in vivo and in vitro. Finally, we found Saccharomyces cerevisiae, which could reduce intestinal PPD levels, was able to markedly alleviate APAP induced liver damage at ZT12. In conclusion, the gut microbial metabolite, 1-phenyl-1,2-propanedione was responsible, at least in part, for the diurnal variation of hepatotoxicity induced by APAP by decreasing GSH levels.