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GLP-1s May Be Working in an Entirely Different Way Than We Thought
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New research suggests that popular weight-loss drugs like Ozempic and Wegovy may work in a more complex way than previously thought. A study published in PNAS found that semaglutide's full weight-lowering effects require functional "hunger neurons" in the brain, challenging the simple notion that these drugs merely suppress appetite. The findings could reshape how scientists understand GLP-1 medications and their metabolic impact.
These neurons, scientifically known as AgRP neurons, are typically associated with promoting hunger. However, researchers from Yale University led by Mateus d'Ávila explain that these cells coordinate a broader response to energy deficit, including mobilizing stored fat. D'Ávila told ScienceAlert that calling them simply "hunger neurons" is an oversimplification.
In experiments with female mice, the researchers disrupted AgRP neuron function using multiple methods. Despite continued appetite suppression from semaglutide, the mice regained lost weight within 15 days, while mice with intact neurons maintained their loss. Notably, the weight-regaining mice were eating the same amount or slightly less, indicating that reduced food intake alone was insufficient.
The findings suggest that semaglutide depends on AgRP neurons to produce its full metabolic benefits, including fat mobilization. When these neurons are disrupted, the body's ability to use stored energy diminishes. This reveals a dual mechanism: appetite reduction plus energy expenditure coordination.
D'Ávila cautioned that this is a preclinical mechanistic study, not guidance for human use. He emphasized that the results should not change how people take semaglutide. The study also found sex differences, as male mice did not show the same effects, and diet affected outcomes.
Previous research had shown that GLP-1 drugs rapidly inhibit AgRP neurons, with stronger inhibition linked to reduced food intake. Another study identified brainstem neurons necessary for the drugs' appetite effects. The new work does not overturn those findings but adds complexity to the picture.
More research is needed to determine whether this mechanism explains why semaglutide may produce more sustained weight loss than older appetite suppressants. The researchers did not directly compare the drug with other treatments. Future studies should explore human relevance and potential therapeutic targets.
