Gut bugs help regulate blood pressure

Gut bacteria play a key role in maintaining a stable blood pressure, scientists claim.
Researchers at The Johns Hopkins University and Yale University have discovered that a specialised receptor, normally found in the nose, is also in blood vessels throughout the body, sensing small molecules created by microbes that line mammalian intestines, and responding to these molecules by increasing blood pressure.
The study suggested that gut bacteria are an integral part of the body's complex system for maintaining a stable blood pressure.
"The contribution that gut microbes apparently make to blood pressure regulation and human health is a surprise," said Jennifer Pluznick, assistant professor of physiology at the Johns Hopkins University School of Medicine.

"There is still much to learn about this mechanism, but we now know some of the players and how they interact," she said.
Pluznick said that several years ago, thanks to a "happy coincidence", she found - in the kidney - some of the same odour-sensing proteins that give the nose its powers.

Focusing on one of those proteins, olfactory receptor 78 (Olfr78), her team specifically located it in the major branches of the kidney's artery and in the smaller arterioles that lead into the kidney's filtering structures.
By adding different cocktails of molecules to the cells and measuring the light the cells produced, they homed in on a single mixture that activated Olfr78.

They then tested each component in that mix and found that only acetic acid (aka vinegar) bound Olfr78 and caused the reaction.
Acetic acid and its alter ego, acetate, are part of a group of molecules known as short chain fatty acids (SCFAs).
In the body of mammals, including humans, SCFAs are made when zillions of bacteria lining the gut digest starch and cellulose from plant-based foods.
The SCFAs are absorbed by the intestines into the blood stream, where they can interact with Olfr78.
Scientists gave SCFAs to mice missing the Olfr78 gene and found that the rodents' blood pressure decreased, suggesting that SCFAs normally induce Olfr78 to elevate blood pressure.

However, when they gave SCFAs to normal mice with intact Olfr78, they did not see the expected increase in blood pressure, but rather a decrease.
"We don't have the full story yet. There are many players involved in the maintenance of stable levels of blood pressure, and these are just a few of them," Pluznick said.
"We don't know why it would be beneficial for blood pressure to decrease after eating or why gut microbes would play a part in signalling that change," she said.
"But our work opens the door for exploring the effects of antibiotic treatments, probiotics and other dietary changes on blood pressure levels in mice, and perhaps eventually people," she added.