Altering Gut Bacteria May Increase Health and Lifespan

Want to live a longer life? Get the right gut bacteria. Scientists have discovered that by altering the symbiotic, or commensal, relationship between bacteria and the absorptive cells lining the intestine, they can increase the lifespan in Drosophila. The findings could provide a way for researchers to help improve the lifespan and health of individuals in the future.

Scientists have long thought that having the right balance of gut bacteria may be key to enjoying a long, healthy life. In fact, previous research has linked the composition of gut flora in humans with diet and health in the elderly. The list of age-related diseases associated with changes in gut bacteria include cancer, diabetes and inflammatory bowel disease. Yet there's no systematic understanding of how we go from having a young, healthy gut to one that is old and decrepit.

"Our study explores age-increased oxidative stress, inflammation, impaired efficiency of the immune response and the over-proliferation of stem cells," said Heinrich Jasper, one of the researchers, in a news release. "It puts these changes into a hierarchical, causal relationship and highlights the points where we can intervene to rescue the negative results of microbial imbalance."

In this case, the scientists found that the bacterial load in fly intestines increases dramatically with age, resulting in an inflammatory condition. The imbalance is drive by chronic activation of the stress response gene FOXO, which happens with age. This gene suppresses the activity of a class of molecules (PGRP-SCs, homologues of PGLYRPs in humans) that regulate the immune response to bacteria.

In fact, PGRP-SC suppression deregulates signaling molecules that are important to mount an effective immune response to gut bacteria. The resulting immune imbalance allows bacterial numbers to expand, triggering an inflammatory response that includes the production of free radicals. Free radicals, in turn, cause over-proliferation of stem cells in the gut. This can result in epithelial dysplasia, a pre-cancerous state.

The findings reveal a little bit more about how gut bacteria is impacted by aging. More specifically, it reveals how by changing gut bacteria, we could help mitigate the side effects.

"If we can understand how aging affects our commensal population--first in the fly and then in humans--our data suggest that we should be able to impact health span and life span quite strongly, because it is the management of the commensal population that is critical to the health of the organism," said Jasper in a news release.

The findings are published in the journal Cell.