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Estrogen-related receptor gamma is a key regulator of muscle mitochondrial activity and oxidative capacity.

Rangwala SM, Wang X, Calvo JA, Lindsley L, Zhang Y, Deyneko G, Beaulieu V, Gao J, Turner G, Markovits J - J. Biol. Chem. (2010)

Bottom Line: Furthermore, peak oxidative capacity was higher in the transgenics as compared with control littermates.Our data indicate that ERRgamma plays an important role in causing a shift toward slow twitch muscle type and, concomitantly, a greater capacity for endurance exercise.Thus, the activation of this nuclear receptor provides a potential node for therapeutic intervention for diseases such as obesity, which is associated with reduced oxidative metabolism and a lower type I fiber content in skeletal muscle.

View Article: PubMed Central - PubMed

Affiliation: Cardiovascular and Metabolism Disease Area, Novartis Institutes for BioMedical Research, Cambridge, Massachusetts 02139, USA. shamina.rangwala@novartis.com

ABSTRACT
Estrogen-related receptor gamma (ERRgamma) regulates the perinatal switch to oxidative metabolism in the myocardium. We wanted to understand the significance of induction of ERRgamma expression in skeletal muscle by exercise. Muscle-specific VP16ERRgamma transgenic mice demonstrated an increase in exercise capacity, mitochondrial enzyme activity, and enlarged mitochondria despite lower muscle weights. Furthermore, peak oxidative capacity was higher in the transgenics as compared with control littermates. In contrast, mice lacking one copy of ERRgamma exhibited decreased exercise capacity and muscle mitochondrial function. Interestingly, we observed that increased ERRgamma in muscle generates a gene expression profile that closely overlays that of red oxidative fiber-type muscle. We further demonstrated that a small molecule agonist of ERRbeta/gamma can increase mitochondrial function in mouse myotubes. Our data indicate that ERRgamma plays an important role in causing a shift toward slow twitch muscle type and, concomitantly, a greater capacity for endurance exercise. Thus, the activation of this nuclear receptor provides a potential node for therapeutic intervention for diseases such as obesity, which is associated with reduced oxidative metabolism and a lower type I fiber content in skeletal muscle.

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Mice expressing ERRγ in skeletal muscle have “red” muscle, larger mitochondria, and improved oxidative capacity. A, schematic representing the structure of the transgene used to generate the ERRγ transgenic mice. The mouse muscle creatine kinase was used to drive the expression of native ERRγ or VP16ERRγ fusion protein. As shown in the lower left panel, in the VP16ERRγ transgenics, the protein was expressed in the skeletal muscle as observed by Western blot using ERRγ antibody. The endogenous ERRγ band at 50 kDa is indicated. The lower right panel shows a picture of the gastrocnemius-soleus muscle from the wild type (WT) and VP16ERRγ transgenic (TG) mice. n.s., not significant. B, individual muscle weights from the VP16ERRγ (TG) and WT mice (n = 12 mice per group). C, plot showing the size distribution of individual muscle fibers in VP16ERRγ transgenic (red) versus control littermate muscle (WT, black) (n = 5–6 mice per group). D, mitochondrial DNA content from gastrocnemius muscle from WT and VP16ERRγ TG mice (n = 8 mice per group). E, electron micrographs for gastrocnemius muscle from WT (left panels) and VP16ERRγ TG (right panels) mice. The upper panels represent a lower magnification (×5310), and the bottom panels are images taken at a higher magnification (×12,600). The scale for each image is embedded within the image. In the TG images, arrows point to enlarged mitochondria. Images shown are representative from n = 4 per genotype. Exercise capacity determined on a treadmill for the both VP16ERRγ (designated as TG, F–H) and ERRγ (designated as N-TG, I–K) transgenic mice along with their corresponding control WT mice. Data presented are distance run (F and I) and work performed (G and J) (n = 12 mice per group for VP16ERRγ strain and n = 10 for ERRγ strain). Peak oxidative capacity was assessed in WT and TG mice (H) and WT and N-TG mice (K), on a treadmill (n = 10 mice per group for both strains) under a peak VO2 protocol. Statistical significance is indicated as follows: *, p < 0.05; **, p < 0.01; ***, p < 0.005.
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Figure 2: Mice expressing ERRγ in skeletal muscle have “red” muscle, larger mitochondria, and improved oxidative capacity. A, schematic representing the structure of the transgene used to generate the ERRγ transgenic mice. The mouse muscle creatine kinase was used to drive the expression of native ERRγ or VP16ERRγ fusion protein. As shown in the lower left panel, in the VP16ERRγ transgenics, the protein was expressed in the skeletal muscle as observed by Western blot using ERRγ antibody. The endogenous ERRγ band at 50 kDa is indicated. The lower right panel shows a picture of the gastrocnemius-soleus muscle from the wild type (WT) and VP16ERRγ transgenic (TG) mice. n.s., not significant. B, individual muscle weights from the VP16ERRγ (TG) and WT mice (n = 12 mice per group). C, plot showing the size distribution of individual muscle fibers in VP16ERRγ transgenic (red) versus control littermate muscle (WT, black) (n = 5–6 mice per group). D, mitochondrial DNA content from gastrocnemius muscle from WT and VP16ERRγ TG mice (n = 8 mice per group). E, electron micrographs for gastrocnemius muscle from WT (left panels) and VP16ERRγ TG (right panels) mice. The upper panels represent a lower magnification (×5310), and the bottom panels are images taken at a higher magnification (×12,600). The scale for each image is embedded within the image. In the TG images, arrows point to enlarged mitochondria. Images shown are representative from n = 4 per genotype. Exercise capacity determined on a treadmill for the both VP16ERRγ (designated as TG, F–H) and ERRγ (designated as N-TG, I–K) transgenic mice along with their corresponding control WT mice. Data presented are distance run (F and I) and work performed (G and J) (n = 12 mice per group for VP16ERRγ strain and n = 10 for ERRγ strain). Peak oxidative capacity was assessed in WT and TG mice (H) and WT and N-TG mice (K), on a treadmill (n = 10 mice per group for both strains) under a peak VO2 protocol. Statistical significance is indicated as follows: *, p < 0.05; **, p < 0.01; ***, p < 0.005.

Mentions: The muscle creatine kinase promoter was used to generate muscle-specific ERRγ transgenic mice (Fig. 2A, top panel). We analyzed two independent founder lines, one where the ERRγ was expressed as a fusion with the VP16 viral transactivator and the other expressing the “native” version of the protein. Expression of transcriptional factors as VP16 fusions is a strategy often utilized in vivo to ascertain effects elicited by increasing intrinsic activity of the factor beyond that achieved by enhanced protein levels alone (29, 30). Fig. 2A, lower left panel, demonstrates expression of the VP16ERRγ transgenic protein in founder line 431. The transgene was expressed at equal levels in gastrocnemius, soleus, and tibialis anterior muscle but was not expressed in the heart (supplemental Fig. 2A). We observed that VP1ERRγ transgenic muscles were noticeably redder and all hind limb muscles exhibited the same color as the soleus muscle (Fig. 2A, lower right panel). The animals had a similar body weight and body composition as compared with the control littermates (supplemental Fig. 2, B and C). The tibialis anterior (glycolytic type II fiber type muscle) and gastrocnemius (mixed fiber type muscle) muscles were smaller in the transgenics (Fig. 2B), although the mass of an oxidative type I fiber muscle such as soleus was not decreased. The transgenic line 339, expressing increased native ERRγ protein in muscle (supplemental Fig. 3A), exhibited a similar decrease in muscle weight of glycolytic and mixed fiber muscles but no change in soleus muscle, in the absence of any body weight changes (supplemental Fig. 3, B–E).


Estrogen-related receptor gamma is a key regulator of muscle mitochondrial activity and oxidative capacity.

Rangwala SM, Wang X, Calvo JA, Lindsley L, Zhang Y, Deyneko G, Beaulieu V, Gao J, Turner G, Markovits J - J. Biol. Chem. (2010)

Mice expressing ERRγ in skeletal muscle have “red” muscle, larger mitochondria, and improved oxidative capacity. A, schematic representing the structure of the transgene used to generate the ERRγ transgenic mice. The mouse muscle creatine kinase was used to drive the expression of native ERRγ or VP16ERRγ fusion protein. As shown in the lower left panel, in the VP16ERRγ transgenics, the protein was expressed in the skeletal muscle as observed by Western blot using ERRγ antibody. The endogenous ERRγ band at 50 kDa is indicated. The lower right panel shows a picture of the gastrocnemius-soleus muscle from the wild type (WT) and VP16ERRγ transgenic (TG) mice. n.s., not significant. B, individual muscle weights from the VP16ERRγ (TG) and WT mice (n = 12 mice per group). C, plot showing the size distribution of individual muscle fibers in VP16ERRγ transgenic (red) versus control littermate muscle (WT, black) (n = 5–6 mice per group). D, mitochondrial DNA content from gastrocnemius muscle from WT and VP16ERRγ TG mice (n = 8 mice per group). E, electron micrographs for gastrocnemius muscle from WT (left panels) and VP16ERRγ TG (right panels) mice. The upper panels represent a lower magnification (×5310), and the bottom panels are images taken at a higher magnification (×12,600). The scale for each image is embedded within the image. In the TG images, arrows point to enlarged mitochondria. Images shown are representative from n = 4 per genotype. Exercise capacity determined on a treadmill for the both VP16ERRγ (designated as TG, F–H) and ERRγ (designated as N-TG, I–K) transgenic mice along with their corresponding control WT mice. Data presented are distance run (F and I) and work performed (G and J) (n = 12 mice per group for VP16ERRγ strain and n = 10 for ERRγ strain). Peak oxidative capacity was assessed in WT and TG mice (H) and WT and N-TG mice (K), on a treadmill (n = 10 mice per group for both strains) under a peak VO2 protocol. Statistical significance is indicated as follows: *, p < 0.05; **, p < 0.01; ***, p < 0.005.
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Figure 2: Mice expressing ERRγ in skeletal muscle have “red” muscle, larger mitochondria, and improved oxidative capacity. A, schematic representing the structure of the transgene used to generate the ERRγ transgenic mice. The mouse muscle creatine kinase was used to drive the expression of native ERRγ or VP16ERRγ fusion protein. As shown in the lower left panel, in the VP16ERRγ transgenics, the protein was expressed in the skeletal muscle as observed by Western blot using ERRγ antibody. The endogenous ERRγ band at 50 kDa is indicated. The lower right panel shows a picture of the gastrocnemius-soleus muscle from the wild type (WT) and VP16ERRγ transgenic (TG) mice. n.s., not significant. B, individual muscle weights from the VP16ERRγ (TG) and WT mice (n = 12 mice per group). C, plot showing the size distribution of individual muscle fibers in VP16ERRγ transgenic (red) versus control littermate muscle (WT, black) (n = 5–6 mice per group). D, mitochondrial DNA content from gastrocnemius muscle from WT and VP16ERRγ TG mice (n = 8 mice per group). E, electron micrographs for gastrocnemius muscle from WT (left panels) and VP16ERRγ TG (right panels) mice. The upper panels represent a lower magnification (×5310), and the bottom panels are images taken at a higher magnification (×12,600). The scale for each image is embedded within the image. In the TG images, arrows point to enlarged mitochondria. Images shown are representative from n = 4 per genotype. Exercise capacity determined on a treadmill for the both VP16ERRγ (designated as TG, F–H) and ERRγ (designated as N-TG, I–K) transgenic mice along with their corresponding control WT mice. Data presented are distance run (F and I) and work performed (G and J) (n = 12 mice per group for VP16ERRγ strain and n = 10 for ERRγ strain). Peak oxidative capacity was assessed in WT and TG mice (H) and WT and N-TG mice (K), on a treadmill (n = 10 mice per group for both strains) under a peak VO2 protocol. Statistical significance is indicated as follows: *, p < 0.05; **, p < 0.01; ***, p < 0.005.
Mentions: The muscle creatine kinase promoter was used to generate muscle-specific ERRγ transgenic mice (Fig. 2A, top panel). We analyzed two independent founder lines, one where the ERRγ was expressed as a fusion with the VP16 viral transactivator and the other expressing the “native” version of the protein. Expression of transcriptional factors as VP16 fusions is a strategy often utilized in vivo to ascertain effects elicited by increasing intrinsic activity of the factor beyond that achieved by enhanced protein levels alone (29, 30). Fig. 2A, lower left panel, demonstrates expression of the VP16ERRγ transgenic protein in founder line 431. The transgene was expressed at equal levels in gastrocnemius, soleus, and tibialis anterior muscle but was not expressed in the heart (supplemental Fig. 2A). We observed that VP1ERRγ transgenic muscles were noticeably redder and all hind limb muscles exhibited the same color as the soleus muscle (Fig. 2A, lower right panel). The animals had a similar body weight and body composition as compared with the control littermates (supplemental Fig. 2, B and C). The tibialis anterior (glycolytic type II fiber type muscle) and gastrocnemius (mixed fiber type muscle) muscles were smaller in the transgenics (Fig. 2B), although the mass of an oxidative type I fiber muscle such as soleus was not decreased. The transgenic line 339, expressing increased native ERRγ protein in muscle (supplemental Fig. 3A), exhibited a similar decrease in muscle weight of glycolytic and mixed fiber muscles but no change in soleus muscle, in the absence of any body weight changes (supplemental Fig. 3, B–E).

Bottom Line: Furthermore, peak oxidative capacity was higher in the transgenics as compared with control littermates.Our data indicate that ERRgamma plays an important role in causing a shift toward slow twitch muscle type and, concomitantly, a greater capacity for endurance exercise.Thus, the activation of this nuclear receptor provides a potential node for therapeutic intervention for diseases such as obesity, which is associated with reduced oxidative metabolism and a lower type I fiber content in skeletal muscle.

View Article: PubMed Central - PubMed

Affiliation: Cardiovascular and Metabolism Disease Area, Novartis Institutes for BioMedical Research, Cambridge, Massachusetts 02139, USA. shamina.rangwala@novartis.com

ABSTRACT
Estrogen-related receptor gamma (ERRgamma) regulates the perinatal switch to oxidative metabolism in the myocardium. We wanted to understand the significance of induction of ERRgamma expression in skeletal muscle by exercise. Muscle-specific VP16ERRgamma transgenic mice demonstrated an increase in exercise capacity, mitochondrial enzyme activity, and enlarged mitochondria despite lower muscle weights. Furthermore, peak oxidative capacity was higher in the transgenics as compared with control littermates. In contrast, mice lacking one copy of ERRgamma exhibited decreased exercise capacity and muscle mitochondrial function. Interestingly, we observed that increased ERRgamma in muscle generates a gene expression profile that closely overlays that of red oxidative fiber-type muscle. We further demonstrated that a small molecule agonist of ERRbeta/gamma can increase mitochondrial function in mouse myotubes. Our data indicate that ERRgamma plays an important role in causing a shift toward slow twitch muscle type and, concomitantly, a greater capacity for endurance exercise. Thus, the activation of this nuclear receptor provides a potential node for therapeutic intervention for diseases such as obesity, which is associated with reduced oxidative metabolism and a lower type I fiber content in skeletal muscle.

Show MeSH
Related in: MedlinePlus