Increased diaphragm expression of GLUT4 in control and streptozotocin-diabetic rats by fish oil-supplemented diets

Dietary fat intake influences plasma glucose concentration through modifyin g glucose uptake and utilization by adipose and skeletal muscle tissues. In this paper, we studied the effects of a low-fat diet on diaphragm GLUT4 ex pression and fatty acid composition in control and streptozotocin-induced d iabetic rats. Control as well as diabetic rats were divided into three diff erent dietary groups each. Either 5% olive oil, 5% sunflower oil, or 5% fis h oil was the only fat supplied by the diet. Feeding these low-fat diets fo r 5 wk induced major changes in fatty acid composition, both in control and in diabetic rats. Arachidonic acid was higher in diabetic olive and sunflo wer oil-fed rats with respect to fish oil-fed, opposite to docosahexaenoic acid which was higher in diabetic fish oil-fed rats with respect to the oth er two groups. Animals receiving a fish oil diet had the lowest plasma gluc ose concentration. GLUT4 expression in diaphragm, as indicated by GLUT4 pro tein and mRNA, is modulated both by diabetes and by diet fatty acid composi tion. Diabetes induced a decrease in expression in all dietary groups. Plas ma glucose levels correlated well with the increased amount of GLUT4 protei n and mRNA found in fish oil-fed groups. Results are discussed in terms of the influence that arachidonic and n-3 polyunsaturated fatty acids may exer t on the transcriptional and translational control of the GLUT4 gene.