PGC-1α and exercise intensity dependent adaptations in mouse skeletal muscle

Abstract

The aim of the present study was to examine the role of PGC-1α in intensity dependent exercise and exercise training-induced metabolic adaptations in mouse skeletal muscle. Whole body PGC-1α knockout (KO) and littermate wildtype (WT) mice performed a single treadmill running bout at either low intensity (LI) for 40 min or moderate intensity (MI) for 20 min. Blood and quadriceps muscles were removed either immediately after exercise or at 3h or 6h into recovery from exercise and from resting controls. In addition PGC-1α KO and littermate WT mice were exercise trained at either low intensity (LIT) for 40 min or at moderate intensity (MIT) for 20 min 2 times pr. day for 5 weeks. In the first and the last week of the intervention period, mice performed a graded running endurance test. Quadriceps muscles were removed before and after the training period for analyses. The acute exercise bout elicited intensity dependent increases in LC3I and LC3II protein and intensity independent decrease in p62 protein in skeletal muscle late in recovery and increased LC3II with exercise training independent of exercise intensity and volume in WT mice. Furthermore, acute exercise and exercise training did not increase LC3I and LC3II protein in PGC-1α KO. In addition, exercise-induced mRNA responses of PGC-1α isoforms were intensity dependent. In conclusion, these findings indicate that exercise intensity affected autophagy markers differently in skeletal muscle and suggest that PGC-1α regulates both acute and exercise training-induced autophagy in skeletal muscle potentially in a PGC-1α isoform specific manner.

Fig 1. Fig 1 shows a schematic illustration of the positions of the primers and TaqMan probe sequences used for detection of the mRNA encoding the PGC-1α isoforms.

FL primers and TaqMan probe detect the previously described PGC-1-α1/-a, PGC-1-α-b and PGC-1-α-c. The NT primers and Taqman probe detect the previously described NT-PGC-1-α-a, NT-PGC-1-α-b and PGC-1-α-c. The PGC-1α-A primers detect the previously described PGC-1-α1/-a and NT-PGC-1-α-a. The PGC-1α-B primers detect the previously described PGC-1-α-b, NT-PGC-1-α4/-b and PGC-1-α2. The PGC-1α-C primers detect the previously described PGC-1-α-c, NT-PGC-1-α-c and PGC-1-α3.

Fig 2

A) AMPK^Thr172, B) P38^{Thr180/Tyr182}, C) Creb^Ser133, D) CaMKII^Thr286 E) ULK^ser317 and F) ULK^ser757 phosphorylation in quadriceps from PGC-1α knockout (KO) and littermate wildtype (WT) control mice at rest (REST) or immediately after a single treadmill exercise bout at either low intensity (LI) or moderate intensity (MI). Values are mean ±SE, n = 8. *Significantly different from REST within given genotype (p<0.05). ¤ Significantly different from LI within given genotype (p<0.05). # Significantly different from WT within given group (p<0.05).

Fig 3

A) LC3II B) LC3I protein content, C) LC3II/LC3I Ratio and D) P62 protein content from PGC-1α knockout (KO) and littermate wildtype (WT) control mice at rest (REST), 3h and 6h after a single treadmill exercise bout at either low intensity (LI) or moderate intensity (MI). Values are mean ±SE, n = 8. *Significantly different from REST within given genotype (p<0.05). ¤ Significantly different from LI within given genotype (p<0.05). # Significantly different from WT within given group (p<0.05).

Fig 4

A) Full Length PGC-1α, B) NT PGC-1α, C) PGC-1α A, D) PGC-1α B and E) PGC-1α C mRNA content in quadriceps from WT control mice at rest (REST) or 3h after a single treadmill exercise bout at either low intensity (LI) or moderate intensity (MI). Values are mean ±SE with n = 8. *Significantly different from REST within given genotype (p<0.05). ¤ Significantly different from LI within given genotype (p<0.05).

Fig 5

A) Cytochrome C (Cyt C) and B) HexokinaseII (HKII) mRNA content in quadriceps from PGC-1α knockout KO and littermate wildtype (WT) control mice at rest (REST), 3h and 6h after a single treadmill exercise bout at either low intensity (LI) or moderate intensity (MI). Values are mean ±SE, n = 8. *Significantly different from REST within given genotype (p<0.05). ¤ Significantly different from LI within given genotype (p<0.05). $ Significantly different from 3h within given group and genotype (p<0.05). # Significantly different from WT within given group (p<0.05).

Fig 6

A) Body weight, B) lean percentage (%), C) fat percentage (%) and D) quadriceps glycogen content in PGC-1α knockout (KO) and littermate wildtype (WT) control mice after 5 weeks untrained (CON) or exercise training at either low intensity (LIT) or moderate intensity (MIT). Values are mean ±SE, n = 10. *Significantly different from CON within given genotype (p<0.05). ¤ Significantly different from LIT within given genotype (p<0.05). # Significantly different from WT within given group (p<0.05).

Fig 7

A) Running endurance duration (minutes) during a running test performed in week 1 and 5 of the intervention, and muscle B) Citrate synthase activity (CS), C) Cytochrome C protein, and D) Hexokinase II (HKII) protein content from PGC-1α knockout (KO) and littermate wildtype (WT) control mice after 5 weeks untrained (CON) or exercise training at either low intensity (LIT) or moderate intensity (MIT). Values are mean ±SE, n = 10. *Significantly different from CON within given genotype (p<0.05). ¤ Significantly different from LIT within given genotype (p<0.05). # Significantly different from WT within given group (p<0.05).

Fig 8

A) OXPHOS Complex I protein content (AU), B) OXPHOS Complex II protein content (AU), C) OXPHOS Complex III protein content (AU), D) OXPHOS Complex IV protein content (AU) E) OXPHOS Complex V protein content (AU) and F) representative Blots from PGC-1α knockout (KO) and littermate wildtype (WT) control mice after 5 weeks untrained (CON) or exercise training at either low intensity (LIT) or moderate intensity (MIT). Values are mean ±SE, n = 10. # Significantly different from WT within given group (p<0.05).

Fig 9

A) LC3II B) LC3I protein content, C) LC3II/LC3I Ratio D) and p62 protein content (AU) in quadriceps from PGC-1α knockout KO and littermate wildtype (WT) control mice after 5 weeks untrained (CON) or exercise training at either low intensity (LIT) or moderate intensity (MIT). Values are mean ±SE, n = 10. *Significantly different from CON within given genotype (p<0.05). ¤ Significantly different from LIT within given genotype (p<0.05). # Significantly different from WT within given group (p<0.05).