Summary: Researchers have mapped a specific neural pathway that controls how the body responds to dietary protein changes. The study focuses on the liver-derived hormone FGF21 and identifies a hindbrain circuit that directs food choice, appetite and energy expenditure during protein restriction.
This research overturns the long-standing assumption that metabolic adaptations are driven mainly by higher brain centers such as the hypothalamus. Instead, a defined group of neurons in the hindbrain—the nucleus of the solitary tract (NTS)—acts as a primary command center for FGF21, sensing low dietary protein and coordinating rapid behavioral and metabolic responses to preserve energy balance.
Key Facts
- Protein sensor: FGF21 is a hormone produced by the liver that signals the brain when dietary protein is insufficient.
- Hindbrain role: The study shows that NTS neurons expressing the KLB co-receptor are both necessary and sufficient to produce the metabolic and behavioral changes that occur during protein restriction.
- Integrated control: These results challenge the notion of strictly “top-down” metabolic control from the hypothalamus and point to an integrated network with a leading role for the hindbrain.
- Therapeutic potential: Since FGF21-based drugs are already in clinical development for obesity and diabetes, this circuitry insight could help refine therapies to more precisely influence eating behavior and metabolic rate.
Source: Pennington Biomedical Research Center
Overview of the findings
Led by Dr. Christopher Morrison and colleagues at Pennington Biomedical Research Center, the study “FGF21 signals through hindbrain neurons to alter food intake and energy expenditure during dietary protein restriction,” published in Cell Reports, identifies the neural relay that transmits FGF21 signals to change feeding and metabolism. Using genetic tools in mice, the researchers traced FGF21 action to a discrete population of glutamatergic, KLB-expressing neurons in the nucleus of the solitary tract (NTS) of the hindbrain.
The team demonstrated that these NTS-KLB neurons are directly activated by FGF21 and that their activity determines how animals respond to low-protein diets. Ablation of these neurons blocked the usual shifts in food intake, macronutrient preference and energy expenditure that follow protein restriction. Conversely, activating the same neurons produced those metabolic adaptations even without dietary protein deprivation. The result: NTS-KLB neurons form the essential neural link between hepatic nutrient signals and whole-body metabolic responses.
Importantly, the authors evaluated other brain areas previously implicated in FGF21 signaling—such as the suprachiasmatic nucleus (SCN), paraventricular nucleus (PVN) and ventromedial hypothalamus (VMH)—and found that these regions are not required for the adaptive responses to protein restriction. This positions the NTS as the crucial site for FGF21-driven regulation of appetite, food choice and basal energy expenditure.
Dr. Morrison commented that these results highlight how tightly nutrition and brain function are linked: the body constantly monitors dietary composition and immediately adjusts behavior and metabolism. Mapping the precise neural pathway for FGF21 clarifies where and how future therapies might act, and suggests clinical outcomes beyond liver fat—such as eating behavior and metabolic rate—should be considered when testing FGF21-related drugs.
Obesity, diabetes and related metabolic disorders arise in part from disrupted energy balance. By revealing how a liver hormone communicates with a specific hindbrain circuit to regulate that balance, this research provides a clearer foundation for targeted interventions that could improve metabolic health with fewer off-target effects.
The study was supported by the National Institutes of Health. The authors thank the Pennington Biomedical Comparative Biology Core and the Animal Metabolism and Behavior Core for technical assistance.
Key contributors from Pennington Biomedical include Redin Spann, Sora Kim, Shahjalal Khan, Diana Albarado, Sun Fernandez-Kim, Hans-Rudolf Berthoud, David McDougal, Heike Münzberg-Gruening, Yanlin He, Sangho Yu and Christopher D. Morrison.
Key Questions Answered:
A: Protein is essential for maintaining body tissues and function. When protein intake drops, the liver releases FGF21, which activates NTS neurons in the hindbrain. That circuit shifts behavior—driving cravings for protein-rich foods—and adjusts energy expenditure to compensate for the dietary change.
A: FGF21-based therapies are already under clinical investigation. Knowing that FGF21 acts through a defined hindbrain circuit suggests drug development could focus on engaging those pathways to boost metabolism and reduce cravings while limiting effects in other brain areas.
A: Historically the hindbrain was seen mainly as a center for autonomic reflexes. These results show it also serves as a sophisticated metabolic regulator that senses blood-borne signals and orchestrates complex behaviors like food choice and changes in energy use.
Editorial Notes:
- Edited by a Neuroscience News editor.
- Journal paper was reviewed in full by staff.
- Additional context added by editorial staff to clarify implications for metabolic health and therapy development.
About this research
Author: Ernie Ballard
Source: Pennington Biomedical Research Center
Contact: Ernie Ballard, Pennington Biomedical Research Center
Image: Image credit: Neuroscience News
Original Research: Closed access. Title: FGF21 signals through hindbrain neurons to alter food intake and energy expenditure during dietary protein restriction. Authors: Redin A. Spann, Sora Q. Kim, Md Shahjalal H. Khan, Diana A. Albarado, Sun O. Fernandez-Kim, Hans-Rudolf Berthoud, David H. McDougal, Heike Münzberg, Yanlin He, Sangho Yu, Christopher D. Morrison. DOI: 10.1016/j.celrep.2026.117218
Abstract
FGF21 signals through hindbrain neurons to alter food intake and energy expenditure during dietary protein restriction
FGF21 is essential for adaptive responses to dietary protein restriction, but the exact neural circuit mediating these effects was unclear. The study demonstrates that a defined population of glutamatergic, KLB-expressing neurons in the nucleus of the solitary tract (NTS) directly responds to FGF21. Using intersectional genetics in a Klb-Flp mouse line, the researchers show NTS-KLB neurons are activated by FGF21 and are required for the behavioral and metabolic adaptations to protein restriction. Regions previously implicated in FGF21 responses—the suprachiasmatic nucleus (SCN), paraventricular nucleus (PVN), and ventromedial hypothalamus (VMH)—were found not to be necessary. Selective ablation of NTS-KLB neurons blocked changes in food intake, choice and energy expenditure, while chemogenetic activation of these neurons reproduced those adaptations. These findings identify the NTS-KLB circuit as the neural link between liver-derived protein sensing and whole-body metabolic adjustment.