Friday, November 03, 2006

Body Temperature and Life Expectancy

Want to live longer? Maybe you just need to "chill out", literally! This news report from Nature notes that a recent study found that mice cooled by half a degree below normal had a life expectancy 20% longer. That is the equivalent of 7-8 additional human years. Here is a snippet from the report [and what is truly fascinating is how they lowered the temperature of the mice]:

The result implies that chilling human blood could also stretch out our lifespan, if a safe way can be found to do it. "Maybe from the point of view of survival, 37 is not exactly optimal," says lead researcher Bruno Conti of the Scripps Research Institute in La Jolla, California.

....Conti's team managed to cool down mice using genetic engineering. They used a gene called uncoupling protein 2, which diverts the cells' mitochondria from their usual task of making chemical energy, and instead prompts them to release energy as heat.

They inserted this gene into a group of brain cells in the animals' hypothalamus and near to the region that senses and controls body temperature, much like a thermostat. The gene effectively heated up the thermostat and, as a result, tricked the rest of the body into cooling down by 0.3 to 0.5 °C.

....So if 36.5 °C helps animals to live longer, why wasn't it selected for through evolution? The cooler temperature probably has no selective advantage because it stretches out life after reproduction, and does not affect the ability of animals to have children and pass on their genes. And although Conti's mice appeared normal, it's possible that the lower body temperature actually causes subtle health problems.