Restricting mammals' caloric intake has prolonged life in previous studies, but scientists are not sure why. The associated lowering of core body temperature may be the reason, said lead study author Bruno Conti, associate professor at Scripps Research Institute in California.
The mice were bioengineered to produce large quantities of uncoupling protein 2, which subsequently tricked the hypothalamus -- the thermostat of mammals' bodies -- into believing the outside temperature was high, and subsequently cooling the mice by 32.54 to 32.9 degrees Fahrenheit to compensate.
When allowed to eat as much food as they wanted, the female bioengineered mice lived 20 percent longer than controls, and were about the same weight. The male bioengineered mice's lifespan was increased by 12 percent when compared to controls, although their weight increased by about 10 percent. The researchers theorized that they need less energy to maintain body temperature.
Dr. John O. Holloszy, a professor of medicine at Washington University in St. Louis and a calorie restriction expert, said the study was "ingenious and original," but had some flaws.
He pointed out that, while calorie restriction actually extends life span, this study only showed that lowering body temperature allows mice to reach old age. He added that, "the paper gave no information about what the animals died from, so there is no way of knowing what aspect of aging is affected by lower body temperature."
Conti did not take the results of the study lightly, noting future researchers should proceed carefully.
"This study is showing a way of life extension that is independent of calorie restriction," he said. "It has not elucidated the actual methods of body temperature control. The reduction (in temperature) was very small, so we do not know what the effect would be if it were larger."
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