Aerobic exercise training induces metabolic benefits in rats with metabolic syndrome independent of dietary changes

Abstract

Objectives: We evaluated the effects of aerobic exercise training without dietary changes on cardiovascular and metabolic variables and on the expression of glucose transporter Type 4 in rats with metabolic syndrome.

Methods: Twenty male spontaneously hypertensive rats received monosodium glutamate during the neonatal period. The animals were allocated to the following groups: MS (sedentary metabolic syndrome), MS-T (trained on a treadmill for 1 hour/day, 5 days/week for 10 weeks), H (sedentary spontaneously hypertensive rats) and H-T (trained spontaneously hypertensive rats). The Lee index, blood pressure (tail-cuff system), insulin sensitivity (insulin tolerance test) and functional capacity were evaluated before and after 10 weeks of training. Glucose transporter Type 4 expression was analyzed using Western blotting. The data were compared using analysis of variance (ANOVA) (p<0.05).

Results: At baseline, the MS rats exhibited lower insulin sensitivity and increased Lee index compared with the H rats. Training decreased the body weight and Lee index of the MS rats (MS-T vs. MS), but not of the H rats (H-T vs. H). There were no differences in food intake between the groups. At the end of the experiments, the systolic blood pressure was lower in the two trained groups than in their sedentary controls. Whole-body insulin sensitivity increased in the trained groups. Glucose transporter Type 4 content increased in the heart, white adipose tissue and gastrocnemius muscle of the trained groups relative to their respective untrained groups.

Conclusion: In conclusion, the present study shows that an isolated aerobic exercise training intervention is an efficient means of improving several components of metabolic syndrome, that is, training reduces obesity and hypertension and increases insulin sensitivity.

Figure 1

Smooth curve of relative food intake (chow [g]/body weight [g]). H (n = 5): sedentary spontaneously hypertensive rats; H-T (n = 5): trained spontaneously hypertensive rats; MS (n = 5): sedentary metabolic syndrome rats; MS-T (n = 5): trained metabolic syndrome rats. The detailed view shows the area under the curve (AUC). One-way ANOVA was used to compare the AUCs. There were no differences in food intake between the groups (p>0.05).

Figure 2

Effect of 10-week aerobic exercise training on systolic blood pressure. H (n = 5): sedentary spontaneously hypertensive rats; H-T (n = 5): trained spontaneously hypertensive rats; MS (n = 5): sedentary metabolic syndrome rats; MS-T (n = 5): trained metabolic syndrome rats. Repeated measures ANOVA: p(group)<0.001; p(time) = 0.344; p(interaction)<0.001. Bonferroni's post-hoc test group: * p = 0.010 vs. H; † p<0.001 vs. MS.

Figure 3

GLUT4 protein content in the heart, gastrocnemius muscle and epididymal white adipose tissue. The top shows representative images of GLUT4 and the respective loading controls. The loading controls are the total proteins in the 35- to 130-kDa range of Ponceau-stained membranes, as described in the Methods section. The graphs on the bottom show the means±SEM. H (n = 5): sedentary spontaneously hypertensive rats; H-T (n = 5): trained spontaneously hypertensive rats; MS (n = 5): sedentary metabolic syndrome rats; MS-T (n = 5): trained metabolic syndrome rats. Two-way ANOVA (Bonferroni's post-hoc test). * p<0.05 vs. H; † p<0.05 vs. MS; ‡ p<0.05 vs. H-T.

Figure 4

Panel A: Scattergram plot of the GLUT4 protein content in the plasma membrane and the Lee index; Panel B: Scattergram plot of the GLUT4 protein content in the plasma membrane and the insulin sensitivity, evaluated by kITT, for all studied rats.

Figure 5

Scattergram plot of the GLUT4 protein content in the plasma membrane and the maximal velocity exercise test results for all studied rats.