WASHINGTON — Exercise as simple as climbing stairs can help at-risk children of diabetics process sugar better and avoid their parents' disease.
Moderate aerobics helps their muscle cells accept sugar and either use it or store it as the muscle fuel glycogen, according to the report in the New England Journal of Medicine.
"The bottom line is, with exercise we can improve significantly or reverse this abnormality," said Dr. Gerald I. Shulman, professor of medicine and cellular and molecular physiology at Yale University.
Shulman and his colleagues looked at 10 sedentary adult children of diabetics. None were overweight, so any changes due to exercise could not be traced to reducing fat, which is a major risk factor for diabetes.
All were insulin-resistant, meaning they had impaired ability to use their own insulin to break down and use the sugar glucose. Glucose is the main fuel for muscle cells.
In children of diabetics, insulin resistance is the best predictor of who will develop diabetes, the report said.
The 10 worked out four times a week for six weeks. Each time, they did three 15-minute workouts on a stair-climbing machine at moderate intensities.
The researchers had the subjects use a stair climber partly because it worked the body's largest muscles--those in the legs--and partly because it would be easy for other people to follow in their footsteps, Shulman said.
"Stairs are wonderful; there are stairs everywhere," Shulman said. People who don't want to climb story after story can reach the same exercise level by such activities as jogging, biking or swimming, he said.
To see how well the subjects processed glucose, researchers gave them glucose intravenously and took blood samples.
After just one workout, the muscle cells' ability to store glucose had improved by 69%, the study found. And after six weeks, the improvement was 102%, it said. Insulin sensitivity, the ability to use the body's own insulin, was 43% better after the training program.
The study also used sophisticated chemical analysis to try to tease out where the improvement was occurring. But those results left some unanswered questions. The tests showed glucose could be crossing the cell membrane more easily. Or glucose could be transformed more easily by insulin into glycogen, the form in which glucose is stored in the muscle. Or both could be happening, Shulman said.
Previous studies have found that exercisers, including those who are insulin-resistant, are less likely to develop diabetes. But this is the first to watch the change take place, Shulman said.
The study "puts it all together, shows the mechanics and shows that it [insulin resistance] can be reversed by exercise," said Dr. Philip E. Cryer of Washington University. "That's why people like me are enthused," said Cryer, who is president of the American Diabetes Assn.
Exercise doesn't fix the insulin resistance problem, however; it only makes things less bad, the study found.
People without insulin resistance who underwent the same training regimen did even better in using or storing glucose. The best the insulin-resistant exercisers could do after six weeks of exercise was to raise themselves to the levels at which their nonresistant colleagues were without exercise, Shulman said.