Intestinal cells on the left appear to be young and healthy. As the cells age (moving to the right), they degenerate, the intestinal barrier declines, gaps between cells appear and the level of bacteria increases (colorful objects).
Why do some people remain healthy into their 80s and beyond, while others age faster and suffer serious diseases decades earlier? UCLA researchers may have found a possible key to unlock the answer. Analyzing intestinal bacteria (microbiota) could be a promising way to predict health outcomes as we age, they say.
The researchers discovered changes within intestinal microbes that precede and predict the death of fruit flies. “Age-onset decline is very tightly linked to changes within the community of gut microbes,” says David Walker, PhD, professor of integrative biology and physiology. “With age, the number of bacterial cells increases substantially, and the composition of bacterial groups changes.”
The study used fruit flies in part because some live to an age that would be the equivalent of humans in their 80s and 90s, while others age and die much younger. In addition, scientists have identified the fruit-fly genome and know how to switch individual genes on and off.
In a previous study, the UCLA researchers discovered that five or six days before flies died, their intestinal tracts became more permeable and started leaking. In the latest research, the scientists found they were able to detect bacterial changes in the intestine before the leaking began. As part of the study, some fruit flies were given antibiotics that significantly reduce bacterial levels in the intestine; the study found that the antibiotics prevented the age-related increase in bacteria levels and improved intestinal function during aging. The biologists also showed that reducing bacterial levels in old flies can significantly prolong their life spans.
The intestine acts as a barrier to protect organs and tissues from environmental damage, “The health of the intestine — in particular, the maintenance of the barrier protecting the rest of the body from the contents of the gut — is very important and might break down with aging,” says Rebecca Clark, PhD, a postdoctoral scholar when the research was conducted.
Recently, scientists have begun to connect a wide variety of diseases, including diabetes and Parkinson’s, among many others, to changes in the microbiota, but they do not yet know exactly what healthy microbiota look like. “One of the big questions in the biology of aging relates to the large variation in how we age and how long we live,” Dr. Walker says.
When a fruit fly’s intestine begins to leak, its immune response increases substantially and chronically throughout its body. Chronic immune activation is linked with age-related diseases in people as well. Dr. Walker said that the study could lead to realistic ways for scientists to intervene in the aging process and delay the onset of such aging-related diseases as Parkinson’s, Alzheimer’s, cancer and diabetes.
“Distinct Shifts in Microbiota Composition during Drosophila Aging Impair Intestinal Function and Drive Mortality,” Cell Reports, September 8, 2015