2023-05-26 08:00:00
MADRID (EFE).— A scientific team was able to safely and non-invasively induce a state similar to reversible hibernation (or torpor) in mice and rats using ultrasound, which opens the door, if the technique can be applied in the future in humans, to use it in space travel or in medicine.
The research is led by experts from Washington University in St. Louis and represents a further step towards the still distant goal of achieving a kind of hibernation in humans, which has been proposed for more than six decades.
The new ultrasound method may help achieve the “long-sought formula for non-invasively and safely inducing the state of torpor that has been pursued by the scientific community since at least the 1960s,” says lead researcher Hong Chen.
The results are published in the journal “Nature Metabolism” and describe 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. This state can be daily, as in hummingbirds or bats, or seasonal, as in bears.
Although a similar state was proposed in the 1960s for spaceflight astronauts and for people with life-threatening health problems, it remains difficult to safely induce it, recalls a statement from the University of Washington.
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 accomplish this, the team developed a portable ultrasound transducer—device—to stimulate neurons in the preoptic area of the hypothalamus.
In doing so, the mice experienced a drop in body temperature of about three degrees Celsius for about an hour. In addition, his metabolism went from using carbohydrates and fat for energy to just fat, a key feature of torpor, and his heart rate dropped 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. Normal temperature was recovered once the ultrasound was turned off.
To learn how ultrasound-induced hypothermia and hypometabolism are activated, the team studied the activity of neurons in the preoptic area. They observed a constant 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.
In various experiments, they demonstrated that this is an ion channel sensitive to ultrasound and that it contributes to the induction of HUI.
In the rat, which does not naturally go into hibernation, the team administered ultrasound to the preoptic area and observed a drop in skin temperature, particularly in the region of brown adipose tissue, as well as a one-degree drop in body temperature. central, similar to natural torpor. This method could have applications in medicine and long-distance spaceflight.
“This is a significant advance (…). This will open up exciting new fields of research. The experiments are well conceived, since tests are carried out both in a hibernating animal (mouse) and in a non-hibernating animal (rat)”, explains Matteo Cerri, from the University of Bologna, who was not involved in the article.
However, “the limited effects in rats, although significant, also suggest that more work remains to be done for suitable human applications.”
“Given the degree of hypometabolism achieved, I believe this technology will be useful in specific conditions where even modest hypothermia can already be highly beneficial, rather than for interplanetary travel.”
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