Effects of low intensity exercise therapy on early phase insulin secretion in overweight subjects with impaired glucose tolerance and type 2 diabetes mellitus

This study was designed to evaluate effects of exercise therapy on early phase insulin secretion in overweight subjects with impaired glucose tolerance (IGT) and type 2 diabetes mellitus (DM). The subjects consisted of overweight subjects with normal glucose tolerance (NGT, n=10), IGT (n=10) and DM (n=10) (age: 51.1+/-8.2, 56.3+/-8.8 and 58.5+/-6.2 years, respectively). All of these patients performed exercise therapy at lactate threshold intensity for 12 weeks. Before intervention, area under the glucose curve (AUC(PG)) was higher in DM, IGT and NGT groups, and area under the insulin curve (AUC(IRI)) and the early phase insulin secretion as calculated by insulinogenic index was higher in the NGT group than in either the IGT or DM groups (p<0.05). After exercise therapy, the insulin sensitivity, AUC(PG) and AUC(IRI) improved in three groups (p<0.05, respectively). The insulinogenic index increased in IGT and DM groups (p<0.05, respectively), but the changes in the insulinogenic index showed no significant differences between IGT and DM groups. These results suggest that the ss-cell function in subjects with IGT and DM could therefore improve after exercise therapy. Moreover, AUC(PG), AUC(IRI) and insulin sensitivity were also improved no relation to NGT, IGT and DM.