The Circadian Rhythms of Grizzly Bears: A Genetic Study
WASHINGTON — A genetic study led by researchers at Washington State University (WSU) has revealed that the internal clocks of grizzly bears continue to function during hibernation, shedding light on the significant role of circadian rhythms in the metabolism of various organisms, including humans.
The circadian rhythm, a 24-hour cycle integral to an organism’s internal clock, influences physical, mental, and behavioral changes. It responds to sunlight and darkness and plays a crucial role in the function of most living things.
The WSU study found that despite hibernating for several months without eating, bears still exhibit a daily energy production pattern, but with reduced amplitude during hibernation. Additionally, researchers observed that the peak energy production occurred later in the day during hibernation, compared to the active season, yet the daily fluctuation persisted.
Professor Heiko Jansen, a senior author on the study, emphasized the significance of circadian rhythms, stating, “This underscores the importance of the circadian rhythms themselves—that they give organisms the flexibility to still function in a state as extreme as a hibernating bear.”
The WSU article highlighted that circadian rhythms have been linked to metabolic health in humans, with disruptions to these patterns associated with issues such as weight gain and a higher prevalence of diabetes.
To understand how grizzly bears maintain their metabolic health while hibernating, researchers analyzed cellular samples from bears during active and hibernating seasons. Genetic analyses revealed that thousands of genes were expressed rhythmically in hibernating bear cells, demonstrating a circadian rhythm in energy production even during hibernation.
Ultimately, researchers believe that alterations in the circadian rhythm during hibernation enable bears to conserve energy and survive without food for months. Professor Jansen likened this process to “setting a thermostat,” highlighting the bears’ unconventional yet effective method of fine-tuning their metabolic processes and energy expenditure.
