The effect of elevated levels of the gut metabolite TMAO on glucose metabolism after sleeve gastrectomy.

Purpose：Bariatric surgery can effectively alleviate obesity and diabetes by regulation of the gut microbiota. This study aimed to investigate the change in the gut microbiota metabolite TMAO and to explore its effect on glucose metabolism after sleeve gastrectomy (SG).

Materials and methods：Diet-induced obesity mouse models were established, and the mice were randomly divided into four groups: an SG group, a sham-operated group pair-fed with the SG group (PF), a sham-operated group fed ad libitum (AL), and a lean control group (C). At 10 weeks post-surgery, the changes in glycogen content of liver, gut microbiota and the level of FMO3 in the liver were evaluated, and their correlation with TMAO production was analysed. The expression levels of the TMAO/PERK/FOXO1 pathway and the gluconeogenic genes G6PC and PCK1 were measured.

Results：At 10 weeks post-surgery, hepatocyte glycogen levels were restored, and serum TMA and TMAO levels were significantly increased. Faecal metagenomic sequencing results showed that the abundances of Ruminococcaceae and Lachnospiraceae, which were positively correlated with TMAO production, were significantly increased after surgery. While the changes in FMO3, the key enzyme producing TMAO in the liver was found decreased significantly after SG. The expression levels of the TMAO/PERK/FOXO1 pathway and the gluconeogenic genes G6PC and PCK1 were measured. Inconsistent with the changing trend of TMAO, the expression of PERK, FOXO1, PCK, and G6PC significantly decreased after SG.

Conclusions：SG can significantly reduce obesity and restore glucose metabolism. After surgery, TMAO metabolites increased in a microbiota-dependent manner.