A scientific team has managed to safely and non-invasively induce a state similar to hibernation using ultrasound (or torpor) reversible in mice and rats, which opens the door, in the event that the technique could be applied in the future in humans, to use it in space travel or in medicine.
The research was led by experts from the University of Washington in Saint Louis (United States) and represents a further step in the goal, still distant, of achieving a kind of hibernation for humans, which has been proposed for more than six decades.
The new ultrasound method can help achieve the “long-sought formula for non-invasively and safely inducing the state of torpor that the scientific community pursues, at least since the 1960s”, summarizes the main researcher, Hong Chen.
Online now! Induction of a torpor-like hypothermic and hypometabolic state in rodents by ultrasound https://t.co/1NsDAOjmTO
— Nature Metabolism (@NatMetabolism) May 25, 2023
The research is published in the journal Nature Metabolismand describes a method that temporarily activates nerve cells in the brain that lower body temperature and slow metabolism.
Some mammals and birds intelligently conserve energy and heat by entering a state of torpor, during which their body temperature and metabolic rate drop to allow them to survive life-threatening environmental conditions, such as extreme cold or lack of food.
A useful state for astronauts, if it weren’t for the risks
Although a similar status was proposed in the 1960s for astronauts on spaceflight or for patients with life-threatening health problemsit remains difficult to induce it safely, recalls a statement from the university.
The multidisciplinary team induced a torpor-like state in mice using ultrasound to stimulate the preoptic area of the hypothalamus in the brain, which helps regulate body temperature and metabolism. In addition to the mouse, which goes into torpor naturally, they provoked it in a rat, which does not.
To make it, the team developed a portable ultrasound transducer -device- to stimulate neurons in the preoptic area of the hypothalamus.
When stimulated, the mice showed a drop in body temperature of about 3 degrees Celsius for about an hour. In addition, their metabolism switched from using carbohydrates and fat for energy to using only fat, a key characteristic of torpor, and their heart rate dropped by 47%, all at room temperature.
The team also found that as the acoustic pressure and duration of ultrasound increased, so did the depth of decreased body temperature and slowed metabolism, known as ultrasound-induced hypothermia and hypometabolism ( UIH).
The UIH maintained the mouse’s body temperature at 32.95 degrees for about 24 hours, which returned to normal once the ultrasound was turned off, adds the researcher.
The key is in the hypothalamus
To learn how ultrasound-induced hypothermia and hypometabolism are activated, the team studied the dynamics of activity in neurons in the preoptic area of the hypothalamus. They observed a steady increase in neural activity in response to each ultrasound pulse, which coincided with changes in the mice’s body temperatures.
Chen and his team also studied the molecule that allowed these neurons to activate under ultrasound. Using genetic sequencing, they found that ultrasound activated the TRPM2 ion channel in neurons in the preoptic area of the hypothalamus.
In various experiments, they demonstrated that this is an ultrasound-sensitive ion channel and that it contributes to the induction of HUI.
In the rat, which does not naturally go into torpor or hibernation, The team administered ultrasound to the preoptic area of the hypothalamus and observed a decrease in skin temperature, particularly in the region of brown adipose tissue, as well as a decrease of approximately 1 degree in core body temperature. similar to natural torpor.
This method could have future applications in medicine or in long-distance space flights, summarizes the magazine.
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