Brain-produced GLP-1 from PPG neurons, not gut-derived, is the physiological activator of brain GLP-1 receptors | Research

The takeaway

Brain-derived GLP-1 from preproglucagon (PPG) neurons—not gut-derived GLP-1—is the physiological agonist for brain GLP-1 receptors, with PPG neuron activation associated with both eating suppression and stress responses.

Brain makes its own GLP-1
Brain-derived GLP-1 from PPG neurons—not gut GLP-1—is the physiological activator of brain appetite receptors, reframing how we understand GLP-1 drug mechanisms

What the researchers found

Brain-derived GLP-1 (from PPG neurons) is the physiological brain GLP-1R agonist. PPG neurons: brainstem location, multiple populations. Dual function: eating suppression + stress association. Drug target: promising but stress effects need consideration. Different PPG populations may serve different functions.

Why it matters

Understanding that brain GLP-1—not gut GLP-1—drives appetite suppression fundamentally reframes how we think about GLP-1 drug mechanisms. The stress connection raises important safety and efficacy questions.

How the study worked

Critical narrative review of PPG neuron biology, GLP-1 production, brain GLP-1R pharmacology, and translational implications.

What this study cannot tell us

Review format. PPG neuron stress association complicates therapeutic development. Species differences in PPG neuron populations. Human PPG neuron data limited.

How to read the evidence

Critical narrative review synthesizing established and emerging neuroscience.

When this study was published

Published in 2025.

The bigger picture

If brain-made GLP-1 (not gut-made) is what actually suppresses appetite, then GLP-1 drugs work by mimicking a brain signal—not a gut signal. This changes our understanding of obesity pharmacology.

Questions still open

Could drugs targeting specific PPG neuron populations suppress appetite without stress?
Does the stress association explain some GLP-1 drug side effects (nausea, anxiety)?
Would brain-penetrant GLP-1 drugs be more effective than peripherally acting ones?

Common questions

Does the brain make its own GLP-1?

Yes. While GLP-1 is famous as a gut hormone, the brain also produces it through specialized neurons called PPG neurons. This review argues that brain-made GLP-1—not gut-made GLP-1—is what actually activates the brain appetite receptors that GLP-1 drugs target. GLP-1 drugs essentially mimic a brain signal.

Why is the stress connection important?

PPG neurons that produce brain GLP-1 are strongly activated by stress—not just by eating. This means GLP-1 drug-induced appetite suppression and the stress/nausea side effects may come from the same neural system. Understanding this could help design drugs that suppress appetite without causing stress-related side effects.

Read the original research

Brain-Derived GLP-1-Understanding the Physiological Function and Anti-obesity Potential of Preproglucagon Neurons.

Endocrinology, 166(12)

View on PubMed ↗Publisher’s paper ↗

Citation

Trapp, Stefan; Skoug, Cecilia. (2025). Brain-Derived GLP-1-Understanding the Physiological Function and Anti-obesity Potential of Preproglucagon Neurons.. Endocrinology, 166(12). https://doi.org/10.1210/endocr/bqaf169