Ghrelin Hormone Induces Torpor and Lowers Body Temperature During Food Restriction
Background
Ghrelin, often called the "hunger hormone," plays a crucial role in regulating appetite and overall energy balance. While its metabolic functions are well-established, its specific involvement in thermoregulation (the body's ability to maintain its core internal temperature) and the induction of torpor (a state of reduced metabolic activity and body temperature, common in animals facing food scarcity) has been less understood. This study aimed to elucidate the thermoregulatory role of ghrelin in initiating torpor under conditions of restricted feeding.
Results
The study revealed that ghrelin significantly promoted the induction and prolongation of torpor in food-restricted mice. Mice treated with 300 µg/kg ghrelin showed a significant drop in body temperature, reaching a nadir of 28.5°C compared to 34.2°C in saline-treated controls (p<0.001). This ghrelin-induced torpor was characterized by a 45% reduction in metabolic rate and an 80% decrease in activity levels, indicating profound energy conservation. The most striking finding was that ghrelin treatment increased the duration of daily torpor by 2.5-fold, extending periods of low body temperature from an average of 4 hours to 10 hours. Furthermore, ghrelin administration led to a downregulation of key thermogenic genes, such as Ucp1 and Dio2, in brown adipose tissue by 30-50%, providing a molecular mechanism for reduced heat production.
Why It Matters
This research significantly expands our understanding of ghrelin's multifaceted roles, particularly its critical involvement in energy conservation and thermoregulation during periods of nutritional stress. The ability of ghrelin to effectively induce and prolong torpor under food scarcity highlights its potential as a novel therapeutic target. This discovery could pave the way for new strategies to manage metabolic disorders, such as obesity, by modulating energy expenditure, or even for inducing controlled therapeutic hypothermia in clinical settings to protect tissues from damage. Future research should focus on exploring these mechanisms in larger animal models and eventually human trials to assess clinical applicability.