Summary:
Researchers at the University of Missouri report that bullfrog brains can manufacture ketone bodies locally when glucose becomes scarce, rather than relying solely on liver-produced ketones circulating in the blood. This on-site ketogenesis acts as an emergency metabolic reserve that sustains essential neural circuits during prolonged winter hibernation and low-oxygen conditions, and it points to new cellular strategies that could inform treatments for human brain disorders involving energy failure.
Key Facts:
- Localized Ketone Synthesis: Bullfrog brains are capable of producing ketone bodies within neural tissue, a departure from the standard view that ketones are supplied exclusively by the liver during glucose scarcity.
- Winter Survival Mechanism: This internal energy source enables bullfrogs to rapidly restart critical brainstem circuits after months of underwater dormancy when oxygen and glucose are nearly depleted.
- Relevance to Human Neurodegeneration: Because many core metabolic pathways are conserved across vertebrates, understanding brain-derived ketogenesis could reveal protective targets for human conditions where neurons face chronic energy shortages, such as Alzheimer’s disease, ALS, stroke, and certain psychiatric disorders.
Source: University of Missouri
For decades, neurobiology taught that the vertebrate brain depends on a continuous supply of glucose delivered by the bloodstream. If circulating glucose falls or blood flow is compromised, neural activity declines rapidly and can trigger irreversible neuronal damage within minutes. When systemic glucose is low—during starvation, fasted exercise, or ketogenic diets—most vertebrates turn to ketone bodies for fuel, but textbook physiology assigns ketone production to the liver, which breaks down fatty acids and releases acetoacetate and beta-hydroxybutyrate into circulation for uptake by the brain.
The new study from the College of Arts and Science at the University of Missouri (Mizzou) challenges that model. Working with North American bullfrogs (Lithobates catesbeianus), investigators found that when glucose runs out during overwintering, the brain itself produces ketone bodies and uses them to power neurons and synapses without waiting for ketones to arrive from peripheral organs.
An On-Demand Backup Generator for Neurons
“Scientists generally believe ketones are delivered to the brain from elsewhere in the body,” said Joseph Santin, Ph.D., associate professor of biological sciences at Mizzou and lead author of the study. “That’s what makes this discovery so exciting. It’s like discovering a backup generator inside a building everyone assumed had only one power supply.”
The mechanism helps explain how bullfrogs survive extreme metabolic stress during winter. To withstand freezing temperatures, these amphibians remain submerged beneath ice, entering a hibernation-like torpor that suppresses systemic metabolism. By late winter, environmental oxygen and the frogs’ systemic glucose stores can be nearly exhausted. Yet upon thawing they must instantly reactivate brainstem circuits that control breathing and movement. Local ketone production provides immediate, local fuel to restart those life-sustaining processes without relying on slow recovery of peripheral organs.
Translating Amphibian Resilience to Human Neuropathology
This work builds on earlier studies from the Santin lab showing that cold-induced metabolic dormancy preserves fragile synapses against anoxia. The discovery of brain-derived ketone bodies identifies a specific metabolic engine that powers that resilience. The brain’s ability to produce ketones appears transient and activated under extreme stress, which raises important questions about the molecular signals that trigger this emergency program and which cell types—astrocytes, neurons, or both—are responsible for synthesis and transport.
Because the biochemical machinery for cellular respiration and energy metabolism is highly conserved across vertebrates, decoding the enzymatic switches and transport systems that enable intrinsic ketogenesis could suggest therapeutic strategies to protect the human brain. Many neurological and psychiatric diseases show early breakdowns in cerebral glucose metabolism, leaving neurons energy-starved. If researchers can learn how to safely mimic or induce a similar, localized metabolic backup in humans, it may be possible to reduce damage from ischemia, neurodegeneration, or metabolic crisis.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full.
- Additional context was added by editorial staff.
About this Neuroscience Research:
- Media Contact: Eric Stann
- Source: University of Missouri-Columbia
- Image Credit: Image credited to Neuroscience News
- Original Research (Open Access): PNAS (Sept 2, 2026). “Transforming neural activity to operate without glucose metabolism using brain-derived ketone bodies.” Authors: Hafsa Yaseen, Karissa Cisneros, Rebecca Wright, Nikolaus Bueschke, and Joseph M. Santin.
- DOI: 10.1073/pnas.2613981123
Abstract
Transforming neural activity to operate without glucose metabolism using brain-derived ketone bodies
The vertebrate brain is highly sensitive to interruptions in glucose metabolism, and insufficient glucose delivery causes neurological dysfunction. In this study, we identify an animal that can partially defy that limitation: after emergence from hibernation, bullfrog neural circuits can shift away from glucose metabolism and instead use ketone bodies synthesized within the brain.
This process entails ketone body synthesis in glial cells, transport from astrocytes to neurons to sustain synaptic transmission, and coordinated upregulation of genes controlling fatty acid breakdown and ketone transport. Brain-derived ketones also reduce activity losses that occur during hypoxia. These findings explain how frogs restart neural circuits following months underwater when severe hypoxia and hypoglycemia would otherwise compromise performance in most vertebrates.
More broadly, the results show that the vertebrate brain can serve as its own local fuel reserve during acute cessation of glucose metabolism, switching to internally sourced ketone bodies while preserving neural activity. This reframes glucose dependence in the brain as a flexible trait rather than an absolute requirement in all situations.