Gut-bug enzymes help regulate weight gain

Boosting the levels of enzymes made by bacteria in the gut can hold back weight gain – in mice, at least.

That’s the finding of a research group in Cork that looked at the impact of increasing the activity of enzymes called bile salt hydrolases.

The guts of mice, and humans, are home to billions of bacteria, and researchers at the Alimentary Pharmabiotic Centre (APC) had previously shown that it was common for gut bacteria to produce enzymes that can break down bile salts.

"We wanted to see what impact it would have if bacteria in the gut were to produce very high levels of this enzyme activity," said Dr Cormac Gahan, a lecturer in microbiology at University College Cork and an APC investigator.

The researchers modified bacteria to produce high levels of particular bile salt hydrolase enzymes, and then they colonised the guts of mice with the bacteria. The result?

Fat metabolism
Several genes involved in fat metabolism were affected and these mice gained substantially less weight than mice that did not have such high bile salt hydrolase activity.

“When we started we didn’t know which way this experiment was going to go,” said Dr Gahan.

“But the mice that were expressing high levels of bile salt hydrolase showed reduced weight gain compared with the control mice. These bacterial enzymes seem to be a mechanism in regulating weight gain.”

The results of the study are published in the Proceedings of the National Academy of Sciences. The APC researchers are now investigating whether a similar mechanism could be at work in humans.

“We are looking at bile acid profiles in humans and relating these profiles to body mass to see if there’s a similar correlation to the ones we see in the mice,” said Dr Gahan.

But while he reckons that, in the future, diet may be a route to control the gut bacteria that produce bile salt hydrolases, Dr Gahan is keen to point out that the finding is “not a panacea” to address obesity. “We have to be careful and do the proper science to understand it,” he said.