Altered regulation of regional sucrase-isomaltase expression in diabetic rat intestine

Increased sucrase-isomaltase (SI) expression is a prominent feature of adaptive changes observed in the small intestine of streptozocin-treated chronically diabetic (CD) rats. In this study, we examine the cellular and molecular basis of increased SI expression in CD rats by determining SI specific activities and mRNA abundance in sequentially isolated enterocytes along the villus-to-crypt axis of proximal jejunum and distal ileum. In all regions, two- to fourfold increases in sucrase activity in diabetic rat enterocytes were paralleled by increases in SI mRNA. However, analogous to nondiabetic rat intestine, no differences in SI mRNA abundance were observed between corresponding enterocyte fractions from ileum and jejunum of diabetic rat intestine. By nuclear run-on assays, differences in rates of SI gene transcription were not observed in diabetic and nondiabetic intestinal tissues. We conclude that diabetes induces increased total and specific activities and mRNA abundance of intestinal SI, largely through the stabilization of SI mRNA. Furthermore, analogous to nondiabetic small intestine, differences in proximal-to-distal SI expression appear to be determined at the translational or posttranslational level.