Extension of the lifespan of the host by polyamine derived from gut bacteria.

Metabolites produced by gut bacteria are taken up by the host body and have a direct impact on host health. Despite the importance of the metabolites of gut bacteria has attracted much attention, there has been no study clearly analyzing the effects of the metabolites of gut microbes on the lifespan of the host using gnotobiotic animals colonized with gut bacteria deficient in biosynthetic genes involved in the production of the specific metabolite. Polyamines are among the most important metabolites of gut bacteria, with putrescine and spermidine being representative examples. Previous studies showed that increasing polyamines in the colon of mice extends lifespan and improves cognitive function. In this study, we produced gnotobiotic flies colonized with Escherichia coli where the polyamine biosynthetic genes were deleted or complemented. By feeding the gnotobiotic flies with a polyamine-free diet, we analyzed the effect of metabolites derived solely from intestinal bacteria on the lifespan of the host. The results showed that polyamines derived from gut bacteria significantly prolonged the host's lifespan. Furthermore, in the host, the expression of TotM and Halo was suppressed in the group of flies that were monocolonized with E. coli capable of producing polyamines compared to those with E. coli incapable of producing polyamines.