We all know what aging looks like – wrinkles, gray hair, arched back – but what's going on internally in the human body? A new study from The Buck Institute of Research on Aging is probing the answer that goes hand-in-hand with senior wellness, specifically focusing in on the stomach.
Lead author Dr. Heinrich Jasper altered the symbiotic relationship between bacteria and the absorptive cells lining the intestine to promote and lengthened lifespan in drosophila, or fruit flies.
"Our study explores age-related changes in the gut that include increased oxidative stress, inflammation, impaired efficiency of the immune response, and the over-proliferation of stem cells," Jasper told Buck Institute for Research on Aging. "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."
Previous research in humans made a three-way bridge connecting the composition of gut flora with diet and health in the elderly and a range of age-related diseases associated with alterations in gut bacteria, including diabetes, cancer and inflammatory bowel disease. However, as Jasper points out, there is no systemic understanding of how the stomach ages from a young, healthy gut to being old and decrepit.
As the fly ages, the bacterial load in its intestines increase dramatically, which is part of a chain reaction that first leads to an inflammatory condition. This imbalance is caused by chronic activation of the stress response gene FOXO – a naturally occurring reaction with age – which inhibits the activity of a class of molecules called PGRP-SCs (an equivalent in humans) that monitor the immune response to bacteria. As a consequence, the immune imbalance allows the bacteria to expand, producing the inflammatory response that promotes the production of free radicals, which are infamous for an array of chronic diseases, namely, cancer, arthritis, diabetes and Alzheimer's. In turn, the free radicals trigger an increase in stem cells that result in a precancerous rate.
Sure, the level of complexity between fruit flies and humans is nearly immeasurable, yet the scientists emphasize that the tiny bugs serve as fascinating templates for which they can better understand human-scale problems dealing with senior wellness.
"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," Jasper told the source.
The shining discovery? The researchers increased the expression of PGRP-SC molecules, which restored the microbial balance and limited the dangerous amount of stem cells to stable levels. In short, they increased the lifespan of the flies.