Gut bacteria could help improve aging

Scientists believe that chemicals made by gut bacteria could be used to produce drugs that keep humans healthier in old age.

The compounds, known as "indoles", in laboratory tests helped worms, flies and mice remain active and stress-resistant for more of their lifespans.

Researchers believe medicines derived from indoles could do the same for humans.

This is a direct avenue to a drug that could make people live better for longer, said Lead scientist Professor Daniel Kalman, from Emory University School of Medicine in the US.

The researchers adopted the term "healthspan" to describe the length of time an ageing human or animal can stay active and resist stress. The focus was not on living longer, but remaining healthier.

We need a better understanding of healthspan," said Prof Kalman.

With medical advances, people are living longer; but you might not really want to live longer if it means spending those extra years frail and infirm.

Indoles are produced by many types of gut bacteria through the breakdown of the amino acid tryptophan.

The compounds and their chemical relatives are also found in plants, especially brassica vegetables such as broccoli and kale. One indole relative is auxin, the growth hormone plants use to bend towards sunlight and set down roots.

In the tests, dietary indole was found to more than double the reproductive life of a tiny laboratory worm, increasing its fertility time from five to 12 days.

Indoles also improved mobility and resistance to heat in ageing fruit flies.

And in very old mice, the chemicals helped the animals maintain their weight, mobility and activity levels. In younger mice, they extended survival time after exposure to lethal radiation.

Closer study revealed a distinct set of genes, different from those involved in longevity, that were affected by indoles.

It's like the Picture of Dorian Gray, in terms of the genes involved, said Prof Kalman.

Indoles make old animals look more like the young ones.

The scientists believe that the chemicals may help to keep the intestinal barrier intact or limit systematic inflammatory effects.

Indole is such an ancient messenger. It's how plants steer their growth, how bacteria talk to each other, and it is how plants and bacteria talk with us and ensure proper homeostasis with our immune system. It is perhaps not so surprising that these molecules help maintain our vitality, added Prof Kalman.

The research is reported in the journal Proceedings of the National Academy of Sciences.