Microbes Extend Healthy Lifespan

24 August 2017


C. elegans


Chemicals released by gut microbes slow down the ageing process in worms, flies and even mice, scientists announced this week.

Within 40 years, scientists are predicting that the elderly populations of developed countries will grow by 350 fold [sic - see below for clarification], placing a significant burden on healthcare. But can we help people to age better and remain more independent into older age?

According to Emory University’s Daniel Kalman, the answer is “yes,” with the help of the right bacteria in the intestine that secrete chemicals called "indoles".

Working initially with microscopic worms called C. elegans, he and his colleagues colonised the worms with either indole-secreting bacteria, or the same bacterial strain but minus the gene needed to produce indoles.

Worms exposed to indoles, the Emory team found, did not live longer but they did age better. The animals, which normally live for only about 21 days and become frail, immobile and moribund as they grow older, instead remained highly active and mobile well into worm old-age.

The worms also normally cease reproduction by the age of 5 days, but the indole-treated animals remained fertile for over twice as long.

The team have found that the worms detect the bacterial indole signal via a chemical receptor called AHR - aryl hydrocarbon receptor. This controls the activity of a spectrum of genes in the worm's cells. 

Gene signatures prepared from both the indole-exposed and the indole-deprived animals showed that indoles reduce changes in gene expression that are normally associated with ageing, producing a gene profile in an elderly worm much more reminiscent of that normally seen in a younger animal.

More complex, so called "higher" animals are also affected in the same way. "Flies climb higher in old age, and aged mice are much more resilient against stressors when they are exposed to indoles," explains Kalman. "They cause animals to retain a youthful gene expression profile."

The team suspect that they are plugging into the chemical conversation that goes on between the microbiome and the immune system. They've yet to confirm whether indoles work the same way in humans, although this is something Kalman says they are actively pursuing.

If it turns out that they do, as the team conclude in their paper in PNAS this week, these chemicals "may represent a new class of therapeutics that improve the way we age as opposed to simply extending how long we live."


Indole-exposed flies age more slowly


"Within 40 years, scientists are predicting that the elderly populations of developed countries will grow by 350 fold..." 350 fold? Really? There are currently about 70 million people over the age of 80 in the world. Are you expecting that group to swell to 24.5 billion people by the year 2057? Wow! I think I'll invest my life savings in the nursing home industry!

You are right. The error is in Daniel Kalman's paper:

"Recent advances in health care have contributed to a significant increase in life expectancy of individuals, especially in developed countries, which predict an expansion of geriatric populations by as much as 350-fold over the next 40 y"

See: http://www.pnas.org/content/early/2017/08/15/1706464114.full

They cite: Bansal A, Zhu LJ, Yen K, Tissenbaum HA (2015), where it says "According to the World Health Organization, the population of people living 85 y and beyond is predicted to increase by 351% globally in the next 40 y"

So 350% has become 350-fold. We should have picked that up; thank you for highlighting it.

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