Hexosamine pathway activation improves memory but does not extend lifespan in mice.
Glucosamine feeding and genetic activation of the hexosamine biosynthetic pathway (HBP) have been linked to improved protein quality control and lifespan extension in various species. Thus, there is considerable interest in the potential health benefits of dietary supplementation with glucosamine or other HBP metabolites in people. The HBP is a sensor for energy availability and its activation has been implicated in tumor progression and diabetes in higher organisms. As the activation of the HBP has been linked to longevity in lower animals, it is imperative to explore the long-term effects of chronic HBP activation in mammals, which has not been examined so far. To address this issue, we activated the HBP in mice both genetically and through metabolite supplementation, and evaluated metabolism, memory, and survival. GlcNAc supplementation in the drinking water had no adverse effect on weight gain in males but increased weight in young female mice. Glucose or insulin tolerance were not affected up to 20 months of age. Of note, we observed improved memory in the Morris water maze in young male mice supplemented with GlcNAc. Survival was not changed by GlcNAc supplementation. To assess the effects of genetic HBP activation we overexpressed the key enzyme GFAT1 as well as a constitutively activated point mutant form in all mouse tissues. We detected elevated UDP-GlcNAc levels in mouse brains, but did not find any effects on behavior, memory, or survival. Together, while dietary GlcNAc supplementation did not extend survival in mice, it positively affected memory and is generally well tolerated.