Effects of acarbose on the relationship between changes in GIP and insulin responses to meals in normal subjects

The relationship between changes in gastric inhibitory polypeptide (GIP), C-peptide and insulin responses to meals was studied in 8 normal subjects after 2 weeks of Acarbose treatment. Acarbose caused a significant reduction of GIP and insulin responses (P less than 0.05). The decrease in insulin response could not be explained by changes in the glycaemic stimulus of insulin secretion, as Acarbose did not significantly change the plasma glucose response to meals during the study. The reduced insulin response was seen without a concomitant reduction in the C-peptide response to the meals, thus resulting in a decreased insulin/C-peptide ratio after Acarbose treatment (P less than 0.05). The changes in GIP response after Acarbose correlated positively with the change in insulin/C-peptide ratio (r = 0.69; P less than 0.05). Our data thus challenge the concept that Acarbose therapy affects the secretion of insulin. The positive relationship between changes in GIP response and changes in the insulin/C-peptide ratio rather suggests that GIP affects the metabolism of insulin or C-peptide.