Article

Gene expression profiling of skeletal muscles treated with a soluble activin type IIB receptor.

Program in Genomics, Division of Genetics, Children's Hospital Boston, Harvard Medical School, Boston, USA.
Physiological Genomics (Impact Factor: 2.81). 04/2011; 43(8):398-407. DOI: 10.1152/physiolgenomics.00223.2010
Source: PubMed

ABSTRACT Inhibition of the myostatin signaling pathway is emerging as a promising therapeutic means to treat muscle wasting and degenerative disorders. Activin type IIB receptor (ActRIIB) is the putative myostatin receptor, and a soluble activin receptor (ActRIIB-Fc) has been demonstrated to potently inhibit a subset of transforming growth factor (TGF)-β family members including myostatin. To determine reliable and valid biomarkers for ActRIIB-Fc treatment, we assessed gene expression profiles for quadriceps muscles from mice treated with ActRIIB-Fc compared with mice genetically lacking myostatin and control mice. Expression of 134 genes was significantly altered in mice treated with ActRIIB-Fc over a 2-wk period relative to control mice (fold change > 1.5, P < 0.001), whereas the number of significantly altered genes in mice treated for 2 days was 38, demonstrating a time-dependent response to ActRIIB-Fc in overall muscle gene expression. The number of significantly altered genes in Mstn(-/-) mice relative to control mice was substantially higher (360), but for most of these genes the expression levels in the 2-wk treated mice were closer to the levels in the Mstn(-/-) mice than in control mice (P < 10⁻³⁰). Expression levels of 30 selected genes were further validated with quantitative real-time polymerase chain reaction (qPCR), and a correlation of ≥ 0.89 was observed between the fold changes from the microarray analysis and the qPCR analysis. These data suggest that treatment with ActRIIB-Fc results in overlapping but distinct gene expression signatures compared with myostatin genetic mutation. Differentially expressed genes identified in this study can be used as potential biomarkers for ActRIIB-Fc treatment, which is currently in clinical trials as a therapeutic agent for muscle wasting and degenerative disorders.

0 Bookmarks
 · 
125 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Myostatin regulates skeletal muscle size via the activin receptor IIB (ActRIIB). However, its effect on muscle energy metabolism and energy dependent muscle function remains largely unexplored. This question needs to be solved urgently since various therapies for neuromuscular diseases based on blockade of ActRIIB signaling are being developed. Here we show in mice that four months of pharmacological abrogation of ActRIIB signaling by treatment with soluble ActRIIB-Fc triggers extreme muscle fatigability. This is associated with elevated serum lactate levels and a severe metabolic myopathy in the mdx mouse, an animal model of Duchenne muscular dystrophy. Blockade of ActRIIB signaling down-regulates Porin, a crucial ADP/ATP shuttle between cytosol and mitochondrial matrix leading to a consecutive deficiency of oxidative phosphorylation as measured by in vivo Phophorus Magnetic Resonance Spectroscopy ((31)P-MRS). Further, ActRIIB blockade reduces muscle capillarization, which further compounds the metabolic stress. We show that ActRIIB regulates key determinants of muscle metabolism, such as Pparß, Pgc1a, and Pdk4 thereby optimizing different components of muscle energy metabolism. In conclusion, ActRIIB signaling endows skeletal muscle with high oxidative capacity and low fatigability. The severe metabolic side effects following ActRIIB blockade caution against deploying this strategy, at least in isolation, for treatment of neuromuscular disorders.Molecular Therapy (2014); doi:10.1038/mt.2014.90.
    Molecular Therapy 05/2014; · 6.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Previously, we identified family with sequence similarity 65, member B (Fam65b), as a protein transiently up-regulated during differentiation and fusion of human myogenic cells. Silencing of Fam65b expression results in severe reduction of myogenin expression and consequent lack of myoblast fusion. The molecular function of Fam65b and whether misregulation of its expression could be causative of muscle diseases are unknown. Protein pulldowns were used to identify Fam65b-interacting proteins in differentiating human muscle cells and regenerating muscle tissue. In vitro, human muscle cells were treated with histone-deacetylase (HDAC) inhibitors, and expression of Fam65b and interacting proteins was studied. Nontreated cells were used as controls. In vivo, expression of Fam65b was down-regulated in developing zebrafish to determine the effects on muscle development. Fam65b binds to HDAC6 and dysferlin, the protein mutated in limb girdle muscular dystrophy 2B. The tricomplex Fam65b-HDAC6-dysferlin is transient, and Fam65b expression is necessary for the complex to form. Treatment of myogenic cells with pan-HDAC or HDAC6-specific inhibitors alters Fam65b expression, while dysferlin expression does not change. Inhibition of Fam65b expression in developing zebrafish results in abnormal muscle, with low birefringence, tears at the myosepta, and increased embryo lethality. Fam65b is an essential component of the HDAC6-dysferlin complex. Down-regulation of Fam65b in developing muscle causes changes consistent with muscle disease.-Balasubramanian, A., Kawahara, G., Gupta, V. A., Rozkalne, A., Beauvais, A., Kunkel, L. M., Gussoni, E. Fam65b is important for formation of the HDAC6-dysferlin protein complex during myogenic cell differentiation.
    The FASEB Journal 03/2014; · 5.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Myostatin (Mstn) participates in the regulation of skeletal muscle size and emerges as a reg-ulator of muscle metabolism. We here hypothesized that lack of myostatin profoundly de-presses oxidative phosphorylation dependent muscle function. For this extent, we explored Mstn-/- mice as a model for the constitutive absence of myostatin and AAV-mediated over-expression of myostatin propeptide as a model of myostatin blockade in adult wildtype mice. We show that muscles from Mstn-/- mice, although larger and stronger, fatigue ex-tremely rapidly. Myostatin deficiency shifts muscle from aerobic towards anaerobic energy metabolism as evidenced by decreased mitochondrial respiration, reduced expression of PPAR transcriptional regulators, increased enolase activity, and exercise induced lactic acido-sis. In consequence, constitutively reduced myostatin signaling diminishes exercise capacity, while the hypermuscular state of Mstn-/- mice increases oxygen consumption and the energy cost of running. We wondered whether these results are the mere consequence of the con-genital fiber-type switch towards a glycolytic phenotype of constitutive Mstn-/- mice. Hence we over-expressed myostatin propeptide in adult mice, which did not affect fiber-type dis-tribution, while nonetheless causing increased muscle fatigability, diminished exercise ca-pacity and decreased Pparb/d and Pgc1a expression. In conclusion, our results suggest that myostatin endows skeletal muscle with high oxidative capacity and low fatigability, thus reg-ulating the delicate balance between muscle mass, muscle force, energy metabolism and endurance capacity.
    AJP Regulatory Integrative and Comparative Physiology 06/2014; · 3.53 Impact Factor

Full-text

Download
22 Downloads
Available from
Sep 18, 2014