Tirzepatide has become an important treatment for obesity and related conditions such as diabetes, but scientists are still working to understand exactly how it affects the body. A study in mice now suggests that the drug may improve metabolism directly by activating brown adipose tissue, a form of fat that specializes in using energy. According to the researchers, the findings provide new clues about how tirzepatide works and could help guide the development of broader treatments for obesity and other metabolic disorders.
The research was led by Marion Peyrou, Ramón y Cajal researcher at the Faculty of Biology and the Institute of Biomedicine of the University of Barcelona (IBUB), the Sant Joan de Déu Research Institute (IRSJD) and the CIBER in Physiopathology of Obesity and Nutrition (CIBEROBN). Tirzepatide Targets Two Hormone Receptors Tirzepatide (generic name of the drug Mounjaro) is approved for weight management in adults with obesity or overweight with comorbidities, as well as for treating poorly controlled type 2 diabetes mellitus. Unlike some other obesity medications, tirzepatide targets the receptors for two hormonal factors at the same time: GIP and GLP-1.
This dual mechanism can produce substantial weight loss, largely because the drug reduces food intake. Researchers wanted to determine whether tirzepatide also produces metabolic changes that cannot be explained simply by eating less. To investigate, the team examined how the drug affected different fat deposits in an experimental mouse model, since this kind of detailed tissue analysis cannot readily be performed in humans.
Obese mice -- fed a high-fat diet -- were treated with tirzepatide. The researchers then compared those animals with mice that did not receive the drug but were given the same amount of food. By controlling food intake this way, the scientists could distinguish changes caused directly by tirzepatide from those resulting from reduced calorie consumption.
Mounjaro Activates Calorie-Burning Brown Fat The analysis showed that tirzepatide activated brown adipose tissue. Unlike white adipose tissue, which primarily stores fat and tends to accumulate in obesity, brown fat specializes in using energy and 'burning' calories from food. "This activation is associated with an increased capacity to burn metabolic energy and with the production of batokines by brown adipose tissue, molecules that are beneficial for metabolism," says Marion Peyrou.
The finding suggests that tirzepatide may influence metabolism in ways that extend beyond the weight loss caused by appetite suppression and reduced food intake. "This drug not only reduces body weight, but also has beneficial effects on metabolism. Active brown adipose tissue 'burns' glucose and fat within the body, which would contribute to its positive effect not only in reducing body weight, but also in lowering blood glucose and fat levels, and improving metabolism," the researcher points out.
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