IS EXERCISE TRAINING EFFECTIVE IN PREVENTING DIABETES-MELLITUS IN THE OTSUKA-LONG-EVANS-TOKUSHIMA FATTY RAT, A MODEL OF SPONTANEOUS NON-INSULIN-DEPENDENT DIABETES-MELLITUS

We determined whether exercise training is effective in preventing the development of diabetes mellitus in a model rat (Otsuka-Long-Evans-Tokushima Fatty [OLETF]) with non-insulin-dependent diabetes mellitus (NIDDM). Thirty male OLETF rats aged 5 weeks were assigned to one of the following three groups: trained rats placed individually in an exercise wheel (EW) cage, EW-control rats housed in the same cages equipped with a fixed rotatory wheel, and sedentary rats maintained two or three to a conventional cage. Eight male diabetes-resistant Long-Evans rats were used as nondiabetic controls. At 24 weeks of age, the trained, EW-control, sedentary, and nondiabetic control rats weighed an average of 445, 559, 621 and 513 g and had abdominal fat deposits of 16, 55, 67, and 23 g, respectively. The mean amount of exercise of trained rats was 5,243 m/d. At 24 weeks of age, the cumulative incidences of diabetes mellitus in sedentary and EW-control rats were 78% and 50%, respectively, while neither trained nor nondiabetic control rats became diabetic. Fasting and 120-minute plasma immunoreactive insulin (IRI) levels after oral glucose administration were significantly lower in the trained group than in the other groups. In vivo insulin-stimulated glucose uptake as measured with a euglycemic clamp was reduced 37% in sedentary rats and increased 35% in trained rats compared with that in nondiabetic control rats. Morphological studies on the pancreas of sedentary and EW-control rats showed enlarged multilobulated fibrotic islets, whereas sections of islets from trained rats appeared normal but slightly enlarged. These results demonstrate that increased physical activity is effective in preventing NIDDM in diabetes-prone rats, probably as a result of increased insulin sensitivity. © 1993.