Skeletal muscle PGC-1α controls whole-body lactate homeostasis through estrogen-related receptor α-dependent activation of LDH B and repression of LDH A

Abstract

The peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) controls metabolic adaptations. We now show that PGC-1α in skeletal muscle drives the expression of lactate dehydrogenase (LDH) B in an estrogen-related receptor-α-dependent manner. Concomitantly, PGC-1α reduces the expression of LDH A and one of its regulators, the transcription factor myelocytomatosis oncogene. PGC-1α thereby coordinately alters the composition of the LDH complex and prevents the increase in blood lactate during exercise. Our results show how PGC-1α actively coordinates lactate homeostasis and provide a unique molecular explanation for PGC-1α-mediated muscle adaptations to training that ultimately enhance exercise performance and improve metabolic health.

Keywords: metabolic reprogramming; mitochondria; muscle plasticity; oxidative metabolism; transcriptional regulation.

Fig. 1.

Muscle PGC-1α controls blood lactate levels by shifting LDH composition. (A and B) Blood lactate excursion curves of WT (black dotted line) and MPGC-1α TG (black continuous line) animals during maximal endurance test (A) and corresponding area under the curve (B). Arrows indicate the time point of exhaustion. (C and D) LDH A mRNA levels (C) and activity (D) in tibialis anterior muscle. (E and F) Lactate tolerance test excursion curves of WT (dotted line) and MPGC-1α TG (continuous line) animals and (E) corresponding area under the curve (F). (G and H) LDH B mRNA levels (G) and activity (H) in tibialis anterior muscle. (I) LDH isoenzyme composition in tibialis anterior of MPGC-1α TG and control littermates. (J) Quantification of the LDH isoenzyme composition. (K) Relative mRNA levels of MCT1, MCT4, and CD147 in MPGC-1α TG and control littermates. All values are expressed as means ± SE (n = 8 per group; *P < 0.05, **P < 0.01, and ***P < 0.001).

Fig. 2.

PGC-1α interacts with ERRα on the LDH B promoter. (A) Venn diagram with red circle denoting the number of transcription factors from MARA of microarray data from C2C12 myotubes following adenoviral overexpression of GFP or bicistronic PGC-1α-GFP. Only transcription factors with Z-scores set above a cutoff of 2 were considered. The 18 transcription factors predicted to bind to LDH B are shown in the blue circle. Two predicted transcription factors were simultaneously found by MARA. (B) Relative mRNA levels of LDH B in C2C12 myotubes following adenoviral overexpression of GFP or bicistronic PGC-1α-GFP and in the absence or presence of XCT-790 or HX-531. All values are expressed as means ± SE (n = 6 per group). @, Effect of PGC-1α (GFP vs. PGC-1α–GFP); #, effect of treatment (DMSO vs. XCT-790 or HX-531); x, interaction. Triple symbols indicate P < 0.001. Symbols at left refer to the comparison of XCT-790–treated C2C12 myotubes vs. controls. Symbols at right refer to the comparison of HX-531–treated C2C12 myotubes vs. controls (*Results from post hoc analysis; ***P < 0.001 vs. GFP-PGC-α untreated). (C) ChIP assay on mouse skeletal muscle. Recruiting of PGC-lα to the ERRα and RXR or to the MEF2 binding site in the LDH B promoter of MPGC-1α TG mice and control animals. (D) Relative mRNA expression levels of Myc and Hif-1α. (E and F) Representative Western blot of Myc (E) and corresponding quantification (F). (G and H) Relative mRNA levels of Myc (G) and LDH A (H) in muscle cells following adenoviral overexpression of GFP or bicistronic PGC-1α–GFP and in the absence or presence of HX-531. All values are expressed as means ± SE (n = 6 per group). @, Effect of PGC-1α (GFP vs. PGC-1α-GFP); #, effect of treatment (DMSO vs. HX-531); x, interaction. Single symbols, P < 0.05; double symbols, P < 0.01; triple symbols, P < 0.001 (*Results from post hoc analysis; **P < 0.01 vs. GFP-PGC-α untreated).

Fig. 3.

PGC-1α is important for the regulation of LDH B transcription. (A and B) Blood lactate excursion curves of WT (dotted line) and MPGC-1α KO (continuous gray line) animals during maximal endurance test (A) and corresponding area under the curve (B). Arrows indicate the time point of exhaustion. (C) LDH A mRNA levels in tibialis anterior muscle of WT and KO mice. (D and E) Lactate tolerance test excursion curves of WT (dotted line) and MPGC-1α KO (continuous gray line) animals (D) and corresponding area under the curve (E). (F) LDH B mRNA levels in tibialis anterior muscle of WT and KO mice. (G) LDH isoenzyme composition in tibialis anterior from MPGC-1α KO and control littermates with 50 μg (Left) and 100 μg (Right) of protein extract. (H and I) Quantification of LDH isoenzyme composition. All values are expressed as means ± SE (n = 6 per group; *P < 0.05, **P < 0.01, and ***P < 0.001).

Fig. 4.

Blood lactate levels are not controlled by heart or liver lactate metabolism following elevated PGC-1α expression. (A) Relative mRNA expression of LDH A, LDH B, MCT1, MCT4, and CD147 in the heart of MPGC-1α TG and control littermates. (B) Relative mRNA expression of LDH A, LDH B, MCT1, MCT4, and CD147 in the liver of MPGC-1α TG and control littermates. (C and D) Conversion of pyruvate to lactate (C) and reverse reaction (D) in the heart of MPGC-1α TG and control littermates. (E and F) Conversion of pyruvate to lactate (E) and reverse reaction (F) in the liver of MPGC-1α TG and control littermates. (G and H) LDH isoenzyme composition (G) and quantification (H) in the heart of MPGC-1α TG and control littermates. (I and J) LDH isoenzyme composition of 20 μg (Left) and 100 μg (Right) of protein extract (I) and quantification (J) in the liver of MPGC-1α TG and control littermates. All values are expressed as means ± SE (n = 8 per group; *P < 0.05, **P < 0.01, and ***P < 0.001).

Fig. 5.

PGC-1α promotes rapid energy provision by lactate oxidation. (A) Scheme illustrating the action of PGC-1α on the LDH B promoter. PGC-1α promotes the transcription of ERRα, which then binds to an ERRα-responsive element (ERRE) in the LDH B promoter. The subsequent activation of ERRα is enhanced by PGC-1α. (B) PGC-1α promotes the expression of RXRs, which, then, by unknown mechanisms, diminish Myc and thereby LDH A expression. (C) Scheme integrating the coordinate actions of PGC-1α on genes regulating lactate homeostasis. The enhanced transcription of MCT1 drives lactate import into skeletal muscle. Lactate is then converted to pyruvate through the action of LDH B. This process is further facilitated by the concomitant reduction in LDH A. NADH is then generated and serves as substrate for the electron transport chain. PGC-1α thereby promotes a lactate oxidizing phenotype, which is associated with improved endurance capacity and metabolic health.