Soluble dietary fibre improves insulin sensitivity by increasing muscle GLUT-4 content in stroke-prone spontaneously hypertensive rats.

1. The effects of soluble dietary fibre (psyllium) on peripheral insulin sensitivity and skeletal muscle GLUT-4 protein expression were studied in 12 male stroke-prone spontaneously hypertensive rats (SHRSP) fed a high-caloric diet from 5 to 9 weeks of age. 2. In the psyllium-supplemented group, fasting plasma glucose was significantly reduced and glucose levels following an oral glucose tolerance test were significantly lower than in the cellulose-supplemented group at 30 (P < 0.05) and 60 min (P < 0.01). However, there was no difference in insulin secretion. 3. In the psyllium-supplemented group, skeletal muscle GLUT-4 content was significantly increased in the plasma membrane (P < 0.001), but not in the intracellular membrane. 4. No significant difference was found in phosphatidylinositol 3 (PI3)-kinase activity between cellulose and psyllium diet not only in the basal state but also when stimulated by insulin. 5. These results demonstrate that psyllium increases blood glucose disposal by increasing skeletal muscle plasma membrane GLUT-4 content without PI3-kinase activation.