Workouts boost function of insulin-making cells

NEW YORK (Reuters Health) - Sedentary older people at risk of developing diabetes showed significant improvement in the function of their insulin-making beta cells after just one week of exercise, University of Michigan researchers found.

Beta cell function is known to decline with age, although it is not clear why, Drs. Cathie J. Bloem and Annette M. Chang explain in the Journal of Clinical Endocrinology and Metabolism.

As people age, they may also become less sensitive to the blood sugar-regulating effects of insulin and develop impaired insulin secretion, the researchers add. And while short-term exercise boosts insulin sensitivity, it has not been clear how it might affect beta cell function.

To investigate, Bloem and Chang had 12 sedentary individuals aged 60 and older perform an hour-long workout every day for a week. The exercise sessions, consisting of stints on a treadmill, exercise bike and cross-training machine, required study participants to work out at 60 percent to 70 percent of their maximum heart rate capacity.

After the exercise period, study participants' sensitivity to insulin had increased by 53 percent, on average, while a measure of beta cell function called the disposition index had risen by 28 percent. However there were no changes in their fat mass, levels of fat in the blood, or other factors that might explain the effect of exercise on beta cells.

"Longer-term exercise training studies are required and are currently in progress to evaluate further exercise training effects on beta cell function in age-related glucose intolerance," the researchers note.

SOURCE: Journal of Clinical Endocrinology and Metabolism, February 2008.