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Cooler Hearted Means Longer LifeLower body temperature significantly prolongs lifespan |
By Stefan Anitei, Science Editor
6th of November 2006, 12:25 GMT
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Researchers at The Scripps Research Institute in La Jolla, California, defying conventional scientific knowledge that animals' core temperature cannot be altered without harmful effects, increased substantially lifespan in mice by lowering body temperature through genetic engineering with 0.3 to 0.5 degree Celsius.
Male mice lived 12 % longer than common males, while females lived 20 % longer than normal females. This corresponds in humans to an extended life span by about 15 years, without serious side effects. "The only side effect suffered by the cool mice was some weight gain in the males," Tamas Bartfai, one of the researchers.
"They ate normally, they had normal sized litters, and they lived normally."
"We've demonstrated that a modest but prolonged reduction
of core body temperature can contribute to increased longevity," said Bruno Conti, a biologist and neuroscientist.
Mice' central thermostat is found in the pre-optic area of hypothalamus region of the brain, above the palate, like in all mammals (human included) and is formed by a group of 3,000 neurons. It maintains body temperature within a narrow range, regardless of changes in weather. Neurons genetically engineered from this area overproduced a protein called "uncoupling", hitting up other cells by more than 0.5 degree centigrade, fooling the nearby thermostat to decrease the body temperature. The "uncoupling" protein is used by mitochondria, cells' energy producing organelle, to shift from energy to heat production as the cell needs. "In mitochondria, if you don't need ATP (energy), you generate heat. This is done through this uncoupling." explained Bartfai.
Scientists don't know precisely why lower body temperature prolongs life span, they suspect that fewer free radicals are produced over time. The chemical by-products of metabolism, Free radicals, a by-product of the metabolism, are linked to disease and aging through damage produced in DNA and cell structures.
"Prior to the new findings, the only reliable way to prolong life in several mammal species has been a calorie-restricted diet," Conti says.
Mice fed with 40 % fewer calories live up to 50 % longer than mice feeding on normal diets. But calorie restriction produces nasty side effects: sterility, depression, cold sensitivity and others. Interestingly enough, low calories diet also produces lower body temperatures and delay the onset of age-related diseases. "But such diets are hardly practical," Conti says.
The new findings shed light on understanding the aging process. "The substantial increase of life span raises the question of whether mild hypothermia … might be easier to tolerate than a lifetime of starvation as a way to increase longevity," said Clifford Saper, a Harvard Medical School neuroscientist.
"Gene therapy-possibly delivered by a virus to the same temperature-regulating area of the brain that was altered in the mice-may be available in the future," Saper says.
Bartfai prefigures a heat-producing device about the size of a rice grain, which - injected into a person's palate - would trick his/her neuronal thermostat, without any gene therapy necessary.
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