The Stink in Farts Controls Blood Pressure

A smelly rotten-egg gas in farts controls blood pressure in mice, a new study finds.

The unpleasant aroma of the gas, called hydrogen sulfide (H2S), can be a little too familiar, as it is expelled by bacteria living in the human colon and eventually makes its way, well, out.

The new research found that cells lining mice’s blood vessels naturally make the gas and this action can help keep the rodents’ blood pressure low by relaxing the blood vessels to prevent hypertension (high blood pressure). This gas is “no doubt” produced in cells lining human blood vessels too, the researchers said.

“Now that we know hydrogen sulfide’s role in regulating blood pressure, it may be possible to design drug therapies that enhance its formation as an alternative to the current methods of treatment for hypertension,” said Johns Hopkins neuroscientist Solomon H. Snyder, M.D., a co-author of the study detailed in the Oct. 24th issue of the journal Science.

Snyder and his colleagues compared normal mice to mice that were missing a gene for an enzyme known as CSE, long suspected as being responsible for making hydrogen sulfide. As they measured hydrogen sulfide levels taken from tissues of the CSE-deficient mice, the scientists found that the gas was depleted in the cardiovascular systems of the altered mice. By contrast, normal mice had higher levels of the gas, thereby showing that hydrogen sulfide is naturally made by mammalian tissues using CSE.

Next, the mice were subjected to higher blood pressures comparable to serious hypertension in humans. Scientists had them respond to a chemical called methacholine that relaxes normal blood vessels. The blood vessels of the CSE-lacking mice hardly relaxed, indicating that hydrogen sulfide is a huge contender for regulating blood pressure.

Hydrogen sulfide is the most recently discovered member of a family of gasotransmitters, small molecules inside our bodies with important physiological functions.

This study is the first to reveal that the CSE enzyme that triggers hydrogen sulfide is activated itself in the same way as other enzymes when they trigger their respective gasotransmitter, such as a nitric oxide-forming enzyme that also regulates blood pressure, Dr. Snyder said.

Because gasotransmitters are common in mammals all over the evolutionary tree, these findings on the importance of hydrogen sulfide are thought to have broad applications to human diseases, such as diabetes and neurodegenerative diseases.

The research was supported by grants from the U.S. Public Health Service and the Canadian Institutes of Health Research as well as a Research Scientist Award.

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