A Gut Bacterium Called Turicibacter Reduces Weight Gain in Mice on High-Fat Diets
A gut bacterium from the genus Turicibacter is responsible for reducing weight gain in mice fed a high-fat diet. Turicibacter is a genus of beneficial gut bacteria common in animals and humans and has been found to help control weight gain and improve metabolic health by producing fats that reduce ceramide levels—even on high-fat diets—though high fat content can also inhibit its growth, creating a complex feedback loop. This microorganism also lowers blood sugar and blood fat levels. High-fat diets prevent Turicibacter from thriving in the gut. If these findings apply to humans, compounds derived from Turicibacter could serve as effective therapeutics to promote metabolic health and a healthy weight.
The gut microbiome is intimately linked to human health and weight. Differences in the gut microbiome—the bacteria and fungi in the intestines—are associated with obesity and weight gain, raising the possibility that altering the microbiome could improve health. However, the human gut contains hundreds of different microbial species, making it difficult to determine which might be helpful. Now, research from the University of Utah has identified a specific type of gut bacteria, called Turicibacter, that improves metabolic health and reduces weight gain in mice on high-fat diets. People with obesity tend to have less Turicibacter, suggesting the microbe may also promote a healthy weight in humans. The findings could lead to new ways to manage weight by adjusting gut bacteria.
Researchers already knew from previous work that a large group of about 100 bacteria could collectively prevent weight gain in mice, but identifying a single key microbe for maintaining weight was a laborious task. "The microbes living in our gut don’t want to live outside the gut at all," explains Kendra Klag, MD, PhD, at the University of Utah’s Spencer Fox Eccles School of Medicine and the study’s first author. Many die from oxygen exposure and must be handled exclusively in sealed bubbles. But after years of cultivating individual microbes, Klag discovered that a rod-shaped bacterium called Turicibacter could, on its own, reduce blood sugar, blood fat levels, and weight gain in mice on high-fat diets.
"I didn’t think a single microbe would have such a dramatic effect—I thought it would be a mix of three or four," says June Round, PhD, professor of microbiology and immunology at U of U Health and the study’s senior author. "So when Klag brought me the first experiment with Turicibacter and the mice staying very lean, I thought, 'This is incredible.' It’s pretty exciting when you see that kind of result."
Turicibacter appears to promote metabolic health by producing fatty molecules absorbed by the small intestine. When researchers added purified fats from Turicibacter to a high-fat diet, they achieved the same weight-control effects as Turicibacter itself. They still don’t know which fatty molecules are key—the bacterium produces thousands of different fats, described by Klag as a "soup of lipids"—but they hope to narrow down the most important ones in future work for potential therapeutic use.
A Fatty Feedback Loop
Turicibacter seems to improve metabolic health by affecting how the host produces a fatty molecule called ceramide, the researchers found. Ceramide levels rise on high-fat diets, and high ceramide levels are linked to many metabolic disorders, including type 2 diabetes and heart disease. But the fats produced by Turicibacter can keep ceramide levels low, even in mice on high-fat diets.
The researchers discovered that Turicibacter levels are affected by how much fat the host consumes. The bacterium won’t grow if there’s too much fat in its environment, so mice fed a high-fat diet will lose Turicibacter from their gut microbiome unless their diet is regularly supplemented with the microbe. The findings point to a complex feedback loop, where a fatty diet inhibits Turicibacter, and the fats produced by Turicibacter improve the host’s response to dietary fats.
The researchers say Turicibacter’s effects are likely not unique. Many different gut bacteria probably contribute to metabolic health. And results from animal models may not apply to humans. "We’ve improved weight gain in mice, but I have no idea if this is actually true in humans," Round commented. But she hopes Turicibacter could be a starting point for developing treatments that promote a healthy metabolism and prevent excessive weight gain.
"Identifying which lipids are having this effect is going to be one of the most important future directions," Round said, "both from a scientific perspective because we want to understand how it works, and from a therapeutic standpoint. Maybe we could use this bacterial lipid, which we know doesn’t have many side effects because people already have it in their gut, as a way to maintain a healthy weight."
"With deeper research into individual microbes, we can turn microbes into medicine and find safe bacteria to create a consortium of different bugs that people with different diseases might be lacking," Klag commented.
Source: Klag K, Ott D, Tippetts TS, et al. Dietary fat disrupts a commensal-host lipid network that promotes metabolic health. Cell Metab. 2025 Nov 5:S1550-4131(25)00441-3.
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