Biology - Hibernation

Scientists have discovered genes for hibernation in humans.

February 8, 2000 - London Times

The discovery could pave the way for human hibernation of the kind foreshadowed for astronauts in the 30-year-old film 2001: A Space Odyssey.

Human hibernation would make ultralong-haul space travel feasible, with crews effectively put to sleep for months, or even years, by triggering the hibernation genes that man's distant ancestors used millions of years ago to sleep through hostile winters.

The American army, which has been funding the research, is interested in the concept of inducing protective hibernation in battlefield casualties to keep them alive when medical help is not at hand.

Researchers in Britain are also investigating the role of genes in the mini-hibernation of Siberian hamsters, with the aim of triggering similar genes in humans to help people lose weight.

But the first use of hibernation technology is likely to be in transplant surgery, where donor organs would be preserved on shelves for weeks or months by putting them into a state of deep sleep.

After a five-year project, Matthew Andrews, associate professor of genetics at North Carolina State University has identified two genes - PL and PDK-4 - which appear to mastermind hibernation.

One stops carbohydrate me-tabolism, which ensures that the glucose that animals have stored in their body from their last meal is preserved for use by the brain and central nervous system. The second gene controls the production of an en-zyme that breaks up stored fatty acids, and converts them into usable fats for fuel. As a result, the animal can tick over on its stored fat.

Hibernation in animals is characterised by huge drops in heart rate, body temperature and metabolism, resulting in long-term dormancy. In this state, body temperature is only a few degrees above freezing, oxygen consumption is down to 2% of normal, and the heart rate drops from up to 300 beats a minute to just three or four.

Researchers found the genes can be made to work in similar ways in humans. The PDK-4 gene, for example, is switched on by starvation, when its job is to conserve glucose.

The next target is to track down the triggers which start the genetic process that leads to the seasonal shutdown. One theory is that melatonin, the hormone whose production responds to light, may be involved.

At the Rowett Institute in Aberdeen, director Dr Peter Morgan and his team have been working on the role of melatonin in the mini-hibernation of the Siberian hamster.

"We think that the central mechanisms which regulate body weight are finely tuned by melatonin, that they respond to the changes in the length of day, the photo period, and make the changes that control food intake, body weight, and energy expenditure," he says.

The research aims to identify what genes are involved in triggering the loss of body fat, and to find a way of kick-starting the same genes in humans as a way of losing weight.