# Brainstem GLP-1 neurons modulate physiological satiation and drive sustained weight loss in obese mice

## TL;DR

Brainstem GLP-1 neurons control how full you feel and can help obese mice lose weight when activated daily.

## Contribution

Chronic activation of brainstem GLP-1 neurons leads to sustained weight loss in obese mice.

## Key findings

- PPG neurons in the NTS and IRT control meal size and satiation.
- Chronic activation of PPG neurons causes sustained weight loss in obese mice.
- PPG neuron number is inversely correlated with body weight in naive mice.

## Abstract

Glucagon-like peptide-1 receptor (GLP-1R) activation in the brain strongly reduces appetite, but most brain GLP-1Rs are not accessible for systemically administered GLP-1R agonists. Acute activation of nucleus tractus solitarius (NTS) GLP-1 neurons, known as preproglucagon (PPG) neurons, strongly suppresses food intake separate from GLP-1R agonists. However, it is unknown if chronic stimulation of PPG neurons is a viable strategy for appetite suppression, or if obesity disrupts their function. Here we demonstrate that PPG neurons in the NTS and intermediate reticular nucleus (IRT) determine meal size, and that their total number is inversely correlated with bodyweight gain. We report that PPGNTS and PPGIRT neurons receive distinct monosynaptic inputs, but have convergent efferent projection targets throughout the brain, and that combined ablation of both populations delays the onset of physiological satiation to a degree sufficient to promote weight gain under ad libitum chow fed conditions. Crucially, chronic daily chemogenetic activation of PPGNTS+IRT neurons drives robust and sustained hypophagia and weight loss in obese mice without notable adverse effects, demonstrating their value as targets for obesity pharmacotherapy.

•Brainstem GLP-1 neurons modulate physiological satiation.•Daily activation of GLP-1 neurons causes sustained weight loss in the obese state.•IRT and NTS GLP-1 neurons have divergent inputs and convergent outputs.•Activity of GLP-1 neurons is upregulated in the obese state.•The number of GLP-1 neurons correlates negatively with body weight in naive mice.

Brainstem GLP-1 neurons modulate physiological satiation.

Daily activation of GLP-1 neurons causes sustained weight loss in the obese state.

IRT and NTS GLP-1 neurons have divergent inputs and convergent outputs.

Activity of GLP-1 neurons is upregulated in the obese state.

The number of GLP-1 neurons correlates negatively with body weight in naive mice.