The effects of exercise training on metabolic phases. With special reference to intraorganic fat and amino acids in Sprague-Dawley rats with streptozotocin diabetes

Abstract

We attempted to clarify the effects of aging and the difference between heavy and mild exercise training on the fat and amino acid (AA) systems of streptozotocin diabetic Sprague-Dawley rats in vivo. We exercised two groups of rats, both composed of juvenile and aged rats. The first group, however, consisted of diabetic rats only, the second of normal rats only. Both groups underwent mild training, 20 cm/s, or heavy training, 33 cm/s, for an hour a day, five times a week for four weeks. We looked for fat and amino acids in the serum, liver, red skeletal muscles and heart muscles at the pre- and post-training stages. The results were as follows: Although we observed decreased triglyceride (TG) levels in the serum, liver and intraskeletal muscles in the normal control group, similar decreases were also observed in the diabetic group undergoing insulin treatment with mild exercise training. On the other hand, we observed a clear increase in the rats subjected to heavy exercise training. This increase was particularly significant in the aged rats. There was, however, no significant change in the TG levels in the intraheart muscles of either the juvenile or aged rats, including the diabetic ones. Exercise training in the normal control group produced decreases in total AA, glycogenic AA, branched chain AA and ketogenic AA. Although there was no significant decrease in the TG levels in the serum, we could see clear signs of a decrease in the liver and the intraskeletal muscles. By contrast, the more the rats undergoing insulin treatment for diabetes were exercised, the greater the increase in the amount of AA in the livers and intraskeletal muscles. These changes were especially significant in the aged group. Consistent with previous reports, the diabetic groups produced different results for fat and AA in proportion to the intensity of exercise training and age of the rats. We also demonstrated that the differences were very small in the serum, but significant in the organs, livers and skeletal muscles. From the above findings, we have concluded that exercise training should play a major role in the treatment of diabetes in consideration not only of serum, but also transitions of the whole body's metabolic phases, including the intraorganic systems.