Hunger and Fullness Receptors Rarely Share the Same Brain Cells — but When They Do, They Talk to Each Other | Research

The takeaway

The ghrelin receptor (GHSR) and the GLP-1 receptor are mostly found on separate brain neurons, but in the small subset where they overlap — primarily in the hypothalamus — activating one receptor dampens the other's signaling.

15-20% overlap in arcuate nucleus
Only a small fraction of ghrelin receptor-positive neurons in the hypothalamic arcuate nucleus also express GLP-1 receptors, but in those cells the two receptors directly modulate each other's signaling

What the researchers found

Using GHSR-eGFP reporter mice, fluorescent ghrelin, and anti-GLP-1R antibodies, the team mapped receptor co-expression across the mouse brain. GHSR+ and GLP-1R+ neurons were largely segregated, with the highest overlap in the arcuate nucleus of the hypothalamus, where 15-20% of GHSR+ cells also expressed GLP-1R. RNA-sequencing data from both mouse and human brains confirmed that double-positive cells represent less than 10% of all GHSR+ or GLP-1R+ neurons.

In patch-clamp experiments, the researchers made the first demonstration that liraglutide-activated GLP-1R inhibits presynaptic calcium channels. Critically, when both receptors were present on the same cell, activating one attenuated the inhibitory effect of the other — showing direct molecular crosstalk between the ghrelin and GLP-1 signaling pathways.

Why it matters

GLP-1 receptor agonists like semaglutide and liraglutide are blockbuster drugs for obesity and diabetes, while ghrelin signaling is a major target for appetite research. Understanding how these two opposing systems interact at the cellular level could reveal why some patients respond better to GLP-1 drugs and may open the door to combination therapies that target both pathways simultaneously.

How the study worked

The study combined three approaches: (1) anatomical mapping using GHSR-eGFP reporter mice and fluorescent ghrelin paired with anti-GLP-1R antibodies to visualize receptor co-localization; (2) analysis of single-cell RNA-sequencing datasets from mouse and human brains; and (3) patch-clamp electrophysiology in a heterologous expression system to measure how each receptor's activation affects presynaptic calcium channel function.

What this study cannot tell us

The co-localization mapping was performed primarily in mice, and while human RNA-seq data was also analyzed, direct protein-level co-localization in human brain tissue was not confirmed. The functional crosstalk experiments used a heterologous expression system rather than native neurons, so the magnitude of crosstalk in vivo may differ. The study focused on calcium channel regulation and did not examine downstream effects on feeding behavior.

How to read the evidence

This is a preclinical study combining anatomical mapping in mice, bioinformatic analysis of human and mouse RNA-seq data, and electrophysiology in a heterologous expression system. It provides strong mechanistic evidence but lacks in vivo behavioral validation.

When this study was published

Published in 2024, this is a very recent study that reflects the current surge of interest in GLP-1 receptor biology driven by the success of semaglutide and similar drugs.

The bigger picture

This study adds nuance to the simple model of ghrelin = hunger, GLP-1 = fullness. By showing that these receptors mostly work independently but can cross-talk in a specific hypothalamic subset, it suggests the brain's appetite circuitry is more compartmentalized than previously assumed — a finding relevant to designing next-generation obesity drugs that target multiple peptide pathways.

Questions still open

Does the crosstalk between GHSR and GLP-1R in the arcuate nucleus directly influence food intake or body weight regulation in vivo?
Could dual-targeting drugs that simultaneously modulate ghrelin and GLP-1 signaling be more effective than GLP-1 agonists alone for obesity treatment?
Does the proportion of double-positive neurons change with obesity, fasting, or chronic GLP-1 agonist treatment?

Common questions

What does it mean that ghrelin and GLP-1 receptors 'cross-talk'?

When both receptors sit on the same neuron, activating one (e.g., with a GLP-1 drug like liraglutide) partially blocks the signaling effect of the other (ghrelin). This means the two appetite-regulating systems aren't fully independent — they can modulate each other at the cellular level.

Does this study explain why GLP-1 drugs reduce appetite?

Partly. It shows that GLP-1 receptor activation can inhibit presynaptic calcium channels and dampen ghrelin receptor signaling in neurons where both receptors coexist. However, since this overlap is limited to a small fraction of neurons, the appetite-suppressing effects of GLP-1 drugs likely involve additional mechanisms beyond this crosstalk.

Read the original research

Selective Colocalization of GHSR and GLP-1R in a Subset of Hypothalamic Neurons and Their Functional Interaction.

Endocrinology, 166(1)

View on PubMed ↗Publisher’s paper ↗

Citation

Aguggia, Julieta; Fernandez, Gimena; Cassano, Daniela; Mustafá, Emilio R; Rodríguez, Silvia S; Cantel, Sonia; Fehrentz, Jean-Alain; Raingo, Jesica; Schiöth, Helgi B; Habib, Abdella M; De Francesco, Pablo N; Perello, Mario. (2024). Selective Colocalization of GHSR and GLP-1R in a Subset of Hypothalamic Neurons and Their Functional Interaction.. Endocrinology, 166(1). https://doi.org/10.1210/endocr/bqae160