But over the past couple of decades, autophagy has also been shown to be involved in things as diverse as fighting bacterial infections and slowing the onset of neurological conditions like Alzheimer's and Huntington's diseases.Most intriguingly of all, it seems that it can slow the process of ageing.
The team's next step is to test whether boosted autophagy can indeed explain the life-extending effects of exercise.
Autophagy presumably arose long ago as a way of helping cells survive lean times.
Dr Levine was a member of the team which showed that an increased level of autophagy, brought on by the stress of living in a constant state of near-starvation, was the mechanism responsible for this life extension.The theory is that what are being disposed of in particular are worn-out mitochondria.
But when the team fed their second group of modified mice a diet designed to induce diabetes, they found that exercise gave no protection at all.Dr Levine and her team reckon their results suggest that manipulating autophagy may offer a new approach to treating diabetes.
After these mice had spent half an hour on a treadmill, she found that the number of autophagosomes in their muscles had increased, and it went on increasing until they had been running for 80 minutes.To find out what, if anything, this exercise-boosted autophagy was doing for mice, the team engineered a second strain that was unable to respond this way.
Experiments in rats themselves showed similar results.Hamartin, which is also known as a tumour suppressant, encourages a cellular recycling mechanism called autophagy.
But a paper just published in Nature by Beth Levine of the University of Texas Southwestern Medical Centre and her colleagues sheds some light on the matter.In this section Worth all the sweat A Rotary engine Ignorance is bliss Flower power The Richard Casement internship ReprintsDr Levine and her team were testing a theory that exercise works its magic, at least in part, by promoting autophagy.
According to an experiment carried out by scientists from John Hopkins University School of Medicine in the US, taking large amounts of the drug sparks an out-of-control version of autophagy, which causes cells to digest their insides.
Scientists tested an experimental drug called CGP3466B and found it protected cells from cocaine-induced autophagy.
Dr Solomon Snyder, from the university, said autopsies were performed on the animals, which showed that their brain cells died as a result of autophagy.
