Evidence for the regulation of small intestinal Na+/glucose cotransporter by insulin.

The small intestinal sodium dependent absorption of D-glucose has been known to be increased by diabetes mellitus. Furthermore, we previously showed that the enhanced activity of Na+/glucose cotransporter (SGLT1) was restored by the treatment with insulin. The present study was designed to investigate the mechanism by which diabetes mellitus and insulin regulated the activity of the small intestinal SGLT1. The acute diabetes at 2 weeks after the injection of streptozotocin increased the expression of SGLT1 protein in rat small intestinal brush border membrane vesicles without changing the mRNA level for SGLT1. In addition, we showed that the increased content of SGLT1 protein was restored by the subcutaneous treatment with insulin. In contrast, there was no change of the mRNA level for SGLT1 in diabetic and insulin-treated diabetic rats. These results suggest that rat intestinal SGLT1 activity is under the translational or posttranslational controls by insulin.