Effect of genetic diabetes on enzymes of mouse intestinal brush-border membrane

Activities of intestinal enzymes were measured in genetically diabetic mouse of strain C57BL/KsJ-dbm to determine the long-term effects of genetic and uncontrolled diabetes on intestinal digestive function. Specific activities of enzymes were measured in intestinal homogenates, brush-border membrane fractions, and everted sacs from diabetic mice and their littermate controls. Sucrase, maltase, trehalase, alkaline phosphatase, and leucylnaphthylamidase activities were elevated in diabetes; lactase did not show any changes. The increases in disaccharidase activities in diabetes were in homogenates from both proximal and distal intestine but the increases in distal were more pronounced than in the proximal. Measurement of enzyme activities in brush-border membrane fractions showed a pattern similar to that observed in homogenates. Hydrolysis of sucrose and trehalose by everted sacs was markedly higher in the diabetic mice. It is therefore concluded that in genetic diabetes the digestive function of the intestine is stimulated, that the increased enzymes were incorporated into the brush-border membrane, and that the additional enzymes are accessible to the substrates in the intestinal lumen and so of physiological significance.