Nitric oxide, the versatile gas that helps increase blood flow and regulate immune function, also prolongs the life of an organism strengthening it against environmental stress, according to a new study.

The study found that a roundworm called Caenorhabditis elegans, an animal widely used in laboratory studies of ageing, lives significantly longer when fed bacteria capable of manufacturing nitric oxide.

The observation points to one of the mechanisms by which the microbiome, the trillions of microbial cells inhabiting our bodies, may play a vital role in our health.

“Our own nitric oxide levels decrease as we get older, a decline that may contribute to normal ageing,” said Evgeny Nudler, the Julie Wilson Anderson Professor of Biochemistry at New York University Langone Medical Center, who led the new study.

Supplemental bacteria, he speculated, might provide a healthy boost by supplying humans with some of the missing compound.

“In worms, we now know that bacteria can use nitric oxide not only to their own advantage but also to provide their host with a beneficial response, and the same thing could be true in a human gut,” said Nudler.

“It may well be the case that our commensal bacteria control some of our genes, at least in the gut, to protect those cells against stress and age-related decline,” he said.

Although humans and many other organisms have the enzyme needed to produce nitric oxide, C elegans does not. Instead, the worm can “hijack” the compound from the soil-dwelling Bacillus subtilis bacterium that is not only a favoured food but also a common colonist within its gut.

This resourcefulness, Nudler said, partially explains why worms fed B subtilis live roughly 50 per cent longer than counterparts fed Escherichia coli, which does not produce the compound.

In the new study, the average C elegans lifespan increased by nearly 15 per cent, to about two weeks, when researchers fed the worms nitric oxide-producing B subtilis bacteria, compared to worms fed mutant B subtilis with a deleted nitric oxide production gene.

The research group also used fluorescent sensors to show that C elegans does not make its own nitric oxide gas. When the worms were fed normal B subtilis bacteria, however, the fluorescent signal appeared in their guts.

“What we found is that nitric oxide gas produced in bacteria inside the worms diffuses into the worm tissue and activates a very specific set of genes acting through two master regulators, hsf-1 and daf-16, resulting in a high resistance to stress and a longer life,” Nudler said in a statement.

The study was published in the journal Cell.

(This article was published on February 15, 2013)
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