Combined effect of AMPK/PPAR agonists and exercise training in mdx mice functional performance

Abstract

The present investigation was undertaken to test whether exercise training (ET) associated with AMPK/PPAR agonists (EM) would improve skeletal muscle function in mdx mice. These drugs have the potential to improve oxidative metabolism. This is of particular interest because oxidative muscle fibers are less affected in the course of the disease than glycolitic counterparts. Therefore, a cohort of 34 male congenic C57Bl/10J mdx mice included in this study was randomly assigned into four groups: vehicle solution (V), EM [AICAR (AMPK agonist, 50 mg/Kg-1.day-1, ip) and GW 1516 (PPARδ agonist, 2.5 mg/Kg-1.day-1, gavage)], ET (voluntary running on activity wheel) and EM+ET. Functional performance (grip meter and rotarod), aerobic capacity (running test), muscle histopathology, serum creatine kinase (CK), levels of ubiquitined proteins, oxidative metabolism protein expression (AMPK, PPAR, myoglobin and SCD) and intracellular calcium handling (DHPR, SERCA and NCX) protein expression were analyzed. Treatments started when the animals were two months old and were maintained for one month. A significant functional improvement (p<0.05) was observed in animals submitted to the combination of ET and EM. CK levels were decreased and the expression of proteins related to oxidative metabolism was increased in this group. There were no differences among the groups in the intracellular calcium handling protein expression. To our knowledge, this is the first study that tested the association of ET with EM in an experimental model of muscular dystrophy. Our results suggest that the association of ET and EM should be further tested as a potential therapeutic approach in muscular dystrophies.

Figure 1. Exercise training associated with its mimetics causes the best improvements on functional capacity in mdx mice.

Grip force (A), time until fall in the Rotarod evaluation (B) and time until exhaustion in the treadmill test (C) after one month of vehicle solution (V), exercise mimetics (EM), exercise training (ET) and EM+ET. The number of animals in each group is shown in parentheses and the data are presented as mean ± SE. *P<0.05 versus vehicle group (V) after two-way ANOVA and Duncan post-hoc test.

Figure 2. When associated with its mimetics, exercise training does not impair skeletal muscle structure in mdx mice.

Cross sectional area (A), intersticium (B), percentage of type I muscle fibers (C), blood creatine kinase (D) and ubiquitined proteins (E) after one month of vehicle solution (V), exercise mimetics (EM), exercise training (ET) and EM+ET. The number of animals in each group is shown in parentheses and the data are presented as mean ± SE. *P<0.05 versus vehicle group (V) after two-way ANOVA and Duncan post-hoc test.

Figure 3. Exercise training associated with its mimetics improves protein expression related to the oxidative metabolism.

Muscular protein expression of AMPKα (A), p-AMPKα(Thr172) (B), p-ACC/ACC ratio (C), PPARδ (D), Myoglobin (E) and SCD (F) after one month of vehicle solution (V), exercise mimetics (EM), exercise training (ET) and EM+ET. The number of animals in each group is shown in parentheses and the data are presented as mean ± SE. *P<0.05 versus vehicle group (V) after two-way ANOVA and Duncan post-hoc test.

Figure 4. Exercise training and its mimetics do not change calcium handling protein expression.

DHPRα1 (A), SERCA 1 (B) and NCX (C) protein expression after one month of vehicle solution (V), exercise mimetics (EM), exercise training (ET) and EM+ET. The number of animals in each group is shown in parentheses and the data are presented as mean ± SE. *P<0.05 versus vehicle group (V) after two-way ANOVA and Duncan post-hoc test.

Figure 5. Exercise training associated with its mimetics does not impair renal function and reduces fat in the carcass.

Creatinine clearance (A) and fat in the carcass (B) after one month of vehicle solution (V), exercise mimetics (EM), exercise training (ET) and EM+ET. The number of animals in each group is shown in parentheses and the data are presented as mean ± SE. *P<0.05 versus vehicle group (V) after two-way ANOVA and Duncan post-hoc test. ^$P<0.05 versus EM and ET groups.