Can gut bugs keep you healthy for longer?

24 August 2017

Interview with

Daniel Kalman, Emory University

Over the next 40 years, scientists are predicting that the elderly populations in developed countries will increase by 350 fold, 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. He was studying a type of worm called C. elegans, which either did, or did not have gut bacteria producing a class of chemicals called indoles. Worms with the indoles didn’t live any longer but they did age better, as did flies, and even mice, as Chris Smith found…

Daniel - There’s been a long tradition in the worm community for studying aging. These animals live 21 or so days so they can be studied pretty easily, more easily than humans. We can feed them bacteria or bacteria mutants, that is bacteria that lacks certain genes, and then we can understand what their responses are relatively quickly. To measure healthspan we look at how well the worms move; as they get older they move less well. We began to work with bacteria that produced particular molecules and asked, “could these bacteria cause older worms to move better?”.

Chris - So your rationale is, if we knockout a certain factor from the bacteria and the worms show accelerated ageing, or their more frail, that molecule coming from those bugs might be involved in the ageing process?

Daniel - Correct. Though the molecules that we’ve identified don’t actually affect the lifespan of the animals. They do affect the health span: that is their capacity to move, their capacity to reproduce, the capacity to a lot of the things that we associate with health versus ageing.

Chris - What are those molecules?

Daniel - The molecules are in a class of indoles, they’re made by plants that govern root growth in plants. They’re made by lots of different kinds of bacteria, including probiotic bacteria, and affect the way bacteria talk to one another, and they also affect us.

Chris - So if there are bugs that make these indoles in the intestines, the animals are healthier. If the bugs don’t make these indoles, the animals don’t live any longer but the are less healthy, they don’t age as well. Do you know what the indoles are doing to the worm’s bodies to exact that change?

Daniel - We do. We were able to identify particular receptors for these indoles and we think this molecule, which we call AHR, recognises indoles and regulates gene expression to produce this healthy ageing effect.

Chris - That’s worms. What about more complicated creatures like mice or like humans - do you think the same effect is going to happen there?

Daniel - We tested that in the paper and we did look at these effects in higher organisms, that is flies and mice, and we saw the same kinds of things. With indoles, worms moved better, flies climb higher, and mice are better able to tolerate stressors. And geriatric mice, these are mice that are very, very old also move better.

Chris - Did you try the experiment where rather than get bacteria to give these animals, these indole molecules, you just gave them the indole molecules without any bacteria which would prove that the indoles do appear to be doing this - it’s not some other factor coming out of the bacteria that’s doing it?

Daniel - Yes. We also can provide the molecules specifically to animals, which we did, in worms, flies, and mice. And these molecules, by themselves are sufficient to produce these protective or healthspan increasing effects.

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