Bacteria for weight loss? Research reveals gut microbe that boosts metabolism in mice

Scientists have pinpointed a gut bacterium, Turicibacter, which was found to improve metabolic health and reduce weight gain in mice on a high-fat diet. Notably, the gut contains hundreds of different microbial species, which has historically made singling out one beneficial species a “microscopic needle in a haystack.” 

Human patients with obesity tend to have less Turicibacter, suggesting that the microbe may generally promote healthy weight. The researchers say their results could lead to new ways to control weight by adjusting gut bacteria. 

“I didn’t think one microbe would have such a dramatic effect — I thought it would be a mix of three or four,” says senior author June Round, Ph.D., professor of microbiology and immunology at the US University of Utah (U of U) Health.

“So when [Klag] brought me the first experiment with Turicibacter and the mice were staying really lean, I was like, ‘This is so amazing.’ It’s pretty exciting when you see those types of results.”

Isolating beneficial bacteria

The researchers had known from previous work that a large group of approximately 100 bacteria was collectively able to prevent weight gain in mice; however, finding a specific microbe that was key to weight maintenance was a laborious task.

“The microbes that live in our gut don’t like to live outside the gut at all,” explains study first author Kendra Klag, Ph.D., M.D. candidate at the Spencer Fox Eccles School of Medicine at the U of U.

“Many are killed by the presence of oxygen and must be exclusively handled in airtight bubbles.”

However, after years of culturing individual microbes, Klag discovered that a rod-shaped bacterium known as Turicibacter “single-handedly” reduced blood sugar levels, fat in the blood, and weight gain for mice on a high-fat diet.

Turicibacter boosted metabolic health by producing fatty molecules that are absorbed by the small intestine. The researchers added these purified Turicibacter fats to a high-fat mouse diet, which led to the “same weight-controlling effects” as Turicibacter itself.

Turicibacter “single-handedly” reduced blood sugar levels, fat in the blood, and weight gain for mice on a high-fat diet.Scientists still don’t know which fatty molecules are essential because the bacterium produces thousands of different fats in what Klag describes as a “lipid soup.” Potential future therapeutic studies may narrow down the most important molecules.

“Identifying what lipid is having this effect is going to be one of the most important future directions,” says Round.

“Both from a scientific perspective, because we want to understand how it works, and from a therapeutic standpoint. Perhaps we could use this bacterial lipid, which we know really doesn’t have a lot of side effects because people have it in their guts, as a way to keep a healthy weight.”

Fatty feedback loop

The research team observed how Turicibacter boosted metabolic health by impacting how the mice produce ceramides. These fatty molecule levels increase on a high-fat diet.

Typically, high levels of ceramides are associated with many metabolic disorders, including type 2 diabetes and heart disease. However, the scientists found that the fats produced by Turicibacter can maintain low ceramide levels, even in mice on a high-fat diet.

They also note that Turicibacter levels are influenced by the amount of fat the host consumes. The bacterium does not grow if there is too much fat in its environment. Therefore, mice fed a high-fat diet will lose Turicibacter from their gut microbiome unless their diet is regularly supplemented with the microbe.

“The results point to a complex feedback loop, in which a fatty diet inhibits Turicibacter and fats produced by Turicibacter improve how the host responds to dietary fats,” details the study team.

The findings suggest that gut microbes could inspire future metabolic therapies, although their human effects remain unproven.The trial results are published in Cell Metabolism.

Potential human applications?

The team believes that Turicibacter’s effects are unlikely to be unique, noting that many different gut bacteria probably contribute to metabolic health. Moreover, results obtained from animal models may not be applicable to humans.

“We have improved weight gain in mice, but I have no idea if this is actually true in humans,” says Round.

The team is hopeful that Turicibacter could provide a starting point for developing treatments that promote healthy metabolism and prevent excessive weight gain.

“With further investigation of individual microbes, we will be able to make microbes into medicine and find bacteria that are safe to create a consortium of different bugs that people with different diseases might be lacking,” Klag comments.

“Microbes are the ultimate wealth of drug discovery. We just know the very tip of the iceberg of what all these different bacterial products can do.”

In previous research on the gut-weight loss axis, scientists pinpointed a gut bacterium producing natural GLP-1 that may induce fat loss while helping the human body regulate blood sugar.