DECREASED GLUCOSE-TRANSPORTER PROTEIN (GLUT4) IN SKELETAL-MUSCLE OF HYPERTRIGLYCERIDEMIC INSULIN-RESISTANT RAT

Protein levels (Western blot) of the major glucose transporter isoform (GLUT4) were measured in skeletal muscles (quadriceps femoris) of an animal model of human metabolic syndrome X, i.e. the hereditary hypert riglyceridaemic (HTG) insulin-resistant rats fed various diets. The re sults were compared with the data obtained in normal Wistar rats which underwent the identical protocol. In HTG rats fed the basal diet (B) or high-sucrose diet (HS) (known to induce hypertriglyceridaemia and t o impair insulin action), a decrease of GLUT4 protein levels (B: Contr ol 100+/-3 vs HTG 46+/-5 %, p<0.005; HS: Control 80+/-9 vs HTG 49+/-3 %, p<0.005) was observed. Furthermore, marine fish oil (FO) rich in n- 3 polyunsaturated fatty acids (PUFA), added to the basal diet (30 wt % of n-3 PUFA) reduced the GLUT4 protein levels (B: 100+/-3 vs B+FO: 42 +/-4 %, p<0.005) in control rats to values similar to those found in H TG rats (B: 46+/-4 %). However, dietary FO did not have any effect in HTG rats (49+/-3 %). Feeding the high-sucrose diet supplemented with F O to both the control and HTG rats was followed by a further decrement of GLUT4 protein (Control 15+/-5 vs HTG 14+/-4 %). In conclusions, a) the hereditary HTG rats had by about 50 % lower GLUT4 protein levels in the quadriceps femoris muscle in comparison to normal Wistar rats; b) high-sucrose diet or raised dietary intake of n-3 PUFA did not furt her alter the number of glucose carriers in quadriceps femoris muscle in HTG rats and c) feeding the high-sucrose diet with higher proportio n of n-3 PUFA was associated with an additional reduction of the GLUT4 protein level in this muscle.