Myostatin inhibition increases muscle mass

Soluble activin receptor type IIB increases forward pulling tension in the mdx mouse

George Carlson C, Bruemmer K, Sesti J, Stefanski C, Curtis H, Ucran J, Lachey J, Seehra JS.

Source

Department of Physiology, Kirksville College Osteopathic Medicine, AT Still University, Kirksville, Missouri 63501, USA. ccarlson@atsu.edu

Abstract

INTRODUCTION:

In this study we investigated the action of RAP-031, a soluble activin receptor type IIB (ActRIIB) comprised of a form of the ActRIIB extracellular domain linked to a murine Fc, and the NF-κB inhibitor, ursodeoxycholic acid (UDCA), on the whole body strength of mdx mice.

METHODS:

The whole body tension (WBT) method of assessing the forward pulling tension (FPT) exerted by dystrophic (mdx) mice was used.

RESULTS:

RAP-031 produced a 41% increase in body mass and a 42.5% increase in FPT without altering the FPT normalized for body mass (WBT). Coadministration of RAP-031 with UDCA produced increases in FPT that were associated with an increase in WBT.

CONCLUSIONS:

Myostatin inhibition increases muscle mass without altering the fundamental weakness characteristic of dystrophic muscle. Cotreatment with an NF-κB inhibitor potentiates the effects of myostatin inhibition in improving FPT in mdx mice.

Copyright © 2011 Wiley Periodicals, Inc.

PMID:

21462203

[PubMed – indexed for MEDLINE]

PMCID: PMC3075386

[Available on 2012/5/1]

Myostatin: a novel insight into its role in metabolism, signal pathways, and expression regulation.

Huang Z, Chen X, Chen D.

Source

Institute of Animal Nutrition, Sichuan Agricultural University, Yaan, Sichuan 625014, PR China.

Abstract

Myostatin, a member of the transforming growth factor-β (TGF-β) superfamily, is a critical autocrine/paracrine inhibitor of skeletal muscle growth. Since the first observed double-muscling phenotype was reported in myostatin-null animals, a functional role of myostatin has been demonstrated in the control of skeletal muscle development. However, beyond the confines of its traditional role in muscle growth inhibition, myostatin has recently been shown to play an important role in metabolism. During the past several years, it has been well established that Smads are canonical mediators of signals for myostatin from the receptors to the nucleus. However, growing evidence supports the notion that Non-Smad signal pathways also participate in myostatin signaling. Myostatin expression is increased in muscle atrophy and metabolic disorders, suggesting that changes in endogenous expression of myostatin may provide therapeutic benefit for these diseases. MicroRNAs (miRNAs) are a class of non-coding RNAs that negatively regulate gene expression and recent evidence has accumulated supporting a role for miRNAs in the regulation of myostatin expression. This review highlights some of these areas in myostatin research: a novel role in metabolism, signal pathways, and miRNA-mediated expression regulation.

Copyright © 2011 Elsevier Inc. All rights reserved.

PMID:

21609762

[PubMed – in process]

Myostatin propeptide (GDF-8) enhances the repair and regeneration of both muscle and bone in a model of deep penetrant musculoskeletal injury

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Recombinant myostatin (GDF-8) propeptide enhances the repair and regeneration of both muscle and bone in a model of deep penetrant musculoskeletal injury

Hamrick MW, Arounleut P, Kellum E, Cain M, Immel D, Liang LF.

Source

Department of Cellular Biology and Anatomy, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912, USA. mhamrick@mail.mcg.edu

Abstract

BACKGROUND:

Myostatin (GDF-8) is known as a potent inhibitor of muscle growth and development, and myostatin is also expressed early in the fracture healing process. The purpose of this study was to test the hypothesis that a new myostatin inhibitor, a recombinant myostatin propeptide, can enhance the repair and regeneration of both muscle and bone in cases of deep penetrant injury.

METHODS:

We used a fibula osteotomy model with associated damage to lateral compartment muscles (fibularis longus and brevis) in mice to test the hypothesis that blocking active myostatin with systemic injections of a recombinant myostatin propeptide would improve muscle and bone repair. Mice were assigned to two treatment groups after undergoing a fibula osteotomy: those receiving either vehicle (saline) or recombinant myostatin propeptide (20 mg/kg). Mice received one injection on the day of surgery, another injection 5 days after surgery, and a third injection 10 days after surgery. Mice were killed 15 days after the osteotomy procedure. Bone repair was assessed using microcomputed tomography (micro-CT) and histologic evaluation of the fracture callus. Muscle healing was assessed using Masson trichrome staining of the injury site, and image analysis was used to quantify the degree of fibrosis and muscle regeneration.

RESULTS:

Three propeptide injections over a period of 15 days increased body mass by 7% and increased muscle mass by almost 20% (p < 0.001). Micro-CT analysis of the osteotomy site shows that by 15 days postosteotomy, bony callus tissue was observed bridging the osteotomy gap in 80% of the propeptide-treated mice but only 40% of the control (vehicle)-treated mice (p < 0.01). Micro-CT quantification shows that bone volume of the fracture callus was increased by ∼ 30% (p < 0.05) with propeptide treatment, and the increase in bone volume was accompanied by a significant increase in cartilage area (p = 0.01). Propeptide treatment significantly decreased the fraction of fibrous tissue in the wound site and increased the fraction of muscle relative to fibrous tissue by 20% (p < 0.01).

CONCLUSIONS:

Blocking myostatin signaling in the injured limb improves fracture healing and enhances muscle regeneration. These data suggest that myostatin inhibitors may be effective for improving wound repair in cases of orthopaedic trauma and extremity injury.

PMID:

20173658

[PubMed – indexed for MEDLINE]

Too much vitamin D causes muscular atrophy

Effects of alfacalcidol on circulating cytokines and growth factors in rat skeletal muscle

Testerink J, Jaspers RT, Rittweger J, de Haan A, Degens H.

Source

Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, John Dalton Building, Oxford Road, Manchester, M5 1GD, UK.

Abstract

Supra-physiological levels of vitamin D induce skeletal muscle atrophy, which may be particularly detrimental in already sarcopaenic elderly. Neither the cause nor whether the atrophy is fibre type specific are known. To obtain supraphysiological levels of circulating vitamin D (1,25(OH)(2)D(3)) 27.5-month-old female Fischer(344) × Brown Norway F1 rats were orally treated for 6 weeks with vehicle or the vitamin D analogue alfacalcidol. Alfacalcidol treatment induced a 22% decrease in body mass and 17% muscle atrophy. Fibre atrophy was restricted to type IIb fibres in the low-oxidative part of the gastrocnemius medialis only (-22%; P < 0.05). There was a concomitant 1.6-fold increase in mRNA expression of the ubiquitin ligase MuRF-1 (P < 0.001), whereas those of insulin-like growth factor 1 and myostatin were not affected. Circulating IL-6 was unaltered, but leptin and adiponectin were decreased (-39%) and increased (64%), respectively. The treated rats also exhibited a reduced food intake. In conclusion, supraphysiological levels of circulating 1,25(OH)(2)D(3) cause preferential atrophy of type IIb fibres, which is associated with an increased expression of MuRF-1 without evidence of systemic inflammation. The atrophy and loss of body mass in the presence of supra-physiological levels of vitamin D are primarily due to a reduced food intake.

PMID:

21909988

[PubMed – as supplied by publisher]