This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: For decades, scientists believed most animals relied on a steady supply of glucose, the body's primary fuel source, to power their brains. When glucose runs out, neural activity begins to fail, potentially leading to lasting brain damage.
Now, researchers at the University of Missouri's College of Arts and Science have discovered that bullfrogs don't follow that rule. Instead, when glucose becomes scarce, their brains can produce an alternative energy source known as ketone bodies, allowing critical neural functions to continue. In most animals, ketone bodies are produced in the liver when glucose levels drop during conditions such as fasting, starvation or prolonged exercise.
The liver breaks down fatty acids into these energy molecules, which then travel through the bloodstream to organs, including the brain, where they are used as fuel. But Mizzou's team discovered that bullfrogs can bypass that process. Instead of relying entirely on the liver, their brains can generate ketones locally, creating an emergency energy reserve where it's needed most.
The findings are published in the Proceedings of the National Academy of Sciences. "Scientists generally believe ketones are delivered to the brain from elsewhere in the body," said Joseph Santin, an associate professor of biological sciences and lead author of the study. "That's what makes this discovery so exciting.
It's like finding a backup generator inside a building that everyone assumed had only one power source." The finding helps explain how bullfrogs survive one of the most challenging periods of their year. Each winter, they enter a hibernation-like state that slows their metabolism and depletes energy reserves. By spring, when oxygen and energy stores are running low, the animals must immediately reactivate essential brain circuits that control bodily functions.
The newly discovered metabolic backup system may be one reason they can make that transition so quickly and successfully. The research builds on years of work in Santin's lab exploring how frogs endure conditions that would severely damage or even kill most animals. Previous studies revealed that this hibernation-like state helps protect neural circuits during extreme oxygen deprivation.
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