transforming-growth-factor-beta and Sarcopenia

Myostatin is a protein belonging to the myokine class, the family of transforming growth factors β (TGF-β). The review article, based on the analysis of literature data, shows the key role of myostatin in the development of senile sarcopenia and cachexia in various pathological conditions, such as cancer, chronic heart failure, chronic renal failure, COPD, etc. The article discusses the structure of myostatin, provides a detailed diagram of the synthesis and activation of myostatin, the ways of implementing the mechanism of action as a negative regulator of muscle growth and differentiation in these pathological conditions. The main physiological properties and clinical significance are highlighted. Exogenous and endogenous factors regulating myostatin expression and possible mechanisms of their action are considered.. Миостатин — белок, принадлежащий к классу миокинов, семейству трансформирующих факторов роста β (TGF-β). В обзорной статье, анализирующей литературные данные, показана ключевая роль миостатина в развитии старческой саркопении и кахексии при различных патологических состояниях, таких как рак, ХСН, ХБП, ХОБЛ и др. В статье рассматривается структура миостатина, подробная схема синтеза и его активации, механизм действия как негативного регулятора роста и дифференцировки мышц при этих патологических состояниях. Выделены основные физиологические свойства и клиническое значение. Рассмотрены экзогенные и эндогенные факторы, регулирующие экспрессию миостатина, и возможные механизмы их действия.

Topics: Cachexia; Cell Differentiation; Humans; Muscle, Skeletal; Myostatin; Sarcopenia; Transforming Growth Factor beta

Skeletal muscle possesses remarkable ability to change its size and force-producing capacity in response to physiological stimuli. Impairment of the cellular processes that govern these attributes also affects muscle mass and function in pathological conditions. Myostatin, a member of the TGF-β family, has been identified as a key regulator of muscle development, and adaptation in adulthood. In muscle, myostatin binds to its type I (ALK4/5) and type II (ActRIIA/B) receptors to initiate Smad2/3 signalling and the regulation of target genes that co-ordinate the balance between protein synthesis and degradation. Interestingly, evidence is emerging that other TGF-β proteins act in concert with myostatin to regulate the growth and remodelling of skeletal muscle. Consequently, dysregulation of TGF-β proteins and their associated signalling components is increasingly being implicated in muscle wasting associated with chronic illness, ageing, and inactivity. The growing understanding of TGF-β biology in muscle, and its potential to advance the development of therapeutics for muscle-related conditions is reviewed here.

Topics: Adaptation, Physiological; Animals; Cachexia; Homeostasis; Humans; Marfan Syndrome; Muscle Development; Muscular Dystrophies; Regeneration; Sarcopenia; Signal Transduction; Transforming Growth Factor beta

Modifiers of TGFβ signaling have been investigated as treatment options for several types of muscle diseases. The purpose of this review is to focus on the most recent studies that have used this treatment strategy for pathological muscle disorders. We also review the recent insight into the mechanistic processes by which TGFβ signaling contributes to these pathologies by promoting fibrosis formation.. Recent research has shed light on the role of TGFβ signaling in the regulation of microRNAs associated with fibrosis formation. Inhibition of TGFβ signaling by Losartan treatment greatly improved the phenotype of myopathies associated with laminin-α2-deficient congenital muscular dystrophy. Caveolin 3 deficiency was also ameliorated by the use of several different types of TGFβ signaling inhibitors. Use of Losartan had dramatically beneficial effects on sarcopenic muscle by improving the regeneration after injury. Pharmacological manipulation to increase muscle mass is an emerging trend in obesity treatment research. New advances in the use of potent myostatin inhibitors have made this an attractive approach for future studies.. An increasing number of skeletal myopathies are demonstrating favorable responses to alterations of the TGFβ signaling pathway. However, future research is needed to fully understand the downstream molecular signature associated with this pathway in order to develop more specific targeted therapies.

Topics: Animals; Caveolin 3; Disease Models, Animal; Fibrosis; Humans; Losartan; MicroRNAs; Muscle, Skeletal; Muscular Diseases; Muscular Dystrophies; Sarcopenia; Signal Transduction; Transforming Growth Factor beta

α-Klotho is a longevity-related protein. Its deficiency shortens lifespan with prominent senescent phenotypes, including muscle atrophy and weakness in mice. α-Klotho has two forms: membrane α-Klotho and circulating α-Klotho (c-α-Klotho). Loss of membrane α-Klotho impairs a phosphaturic effect, thereby accelerating phosphate-induced aging. However, the mechanisms of senescence on c-α-Klotho loss remain largely unknown. Herein, with the aging of wild-type mice, c-α-Klotho declined, whereas Smad2, an intracellular transforming growth factor (TGF)-β effector, became activated in skeletal muscle. Moreover, c-α-Klotho suppressed muscle-wasting TGF-β molecules, including myostatin, growth and differentiation factor 11, activin, and TGF-β1, through binding to ligands as well as type I and type II serine/threonine kinase receptors. Indeed, c-α-Klotho reversed impaired in vitro myogenesis caused by these TGF-βs. Oral administration of Ki26894, a small-molecule inhibitor of type I receptors for these TGF-βs, restored muscle atrophy and weakness in α-Klotho (-/-) mice and in elderly wild-type mice by suppression of activated Smad2 and up-regulated Cdkn1a (p21) transcript, a target of phosphorylated Smad2. Ki26894 also induced the slow to fast myofiber switch. These findings show c-α-Klotho's potential as a circulating inhibitor counteracting TGF-β-induced sarcopenia. These data highlight the potential of a novel therapy involving TGF-β blockade to prevent sarcopenia.

Topics: Animals; Mice; Protein Serine-Threonine Kinases; Receptors, Transforming Growth Factor beta; Sarcopenia; Transforming Growth Factor beta; Transforming Growth Factor beta1; Transforming Growth Factors

Topics: Animals; Cardiovascular Diseases; Humans; Inflammation; Kidney Failure, Chronic; Muscle, Skeletal; Myostatin; Renal Insufficiency, Chronic; Sarcopenia; Signal Transduction; Transforming Growth Factor beta

It has been identified that skeletal muscle is an endocrine tissue. Since skeletal muscle aging affects not only to muscle strength and function but to systemic aging and lifespan, myokines secreted from skeletal muscle may be crucial factors for intertissue communication during aging. In the present study, we investigated the expression of myokines associated with skeletal muscle aging in taurine transporter knockout (TauTKO) mice, which exhibit the accelerated skeletal muscle aging. Among transforming growth factor (TGF)-beta family genes, only growth and differentiation factor 15 (GDF15) was markedly higher (>3-fold) in skeletal muscle of old TauTKO mice compared with that of either young TauTKO mice or old wild-type mice. Circulating levels of GDF15 were also elevated in old TauTKO mice. An elevation in circulating GDF15 was also observed in very old (30-month-old) wild-type mice, while skeletal GDF15 levels were normal. The treatment of cultured mouse C2C12 myotubular cells with aging-related factors that mediate cellular stresses, such as oxidative stress (hydrogen peroxide) and endoplasmic reticulum stress (tunicamycin and thapsigargin), leads to an increase in GDF15 secretion. In conclusion, GDF15 is a myokine secreted by aging-related stress and may control aging phenotype.

Topics: Aging; Animals; Cells, Cultured; Enzyme-Linked Immunosorbent Assay; Growth Differentiation Factor 15; Male; Membrane Glycoproteins; Membrane Transport Proteins; Mice; Mice, Knockout; Muscle, Skeletal; Myoblasts; Oxidative Stress; Real-Time Polymerase Chain Reaction; Sarcopenia; Transforming Growth Factor beta

First line treatment for recurrent and metastatic prostate cancer is androgen deprivation therapy (ADT). Use of ADT has been increasing in frequency and duration, such that side effects increasingly impact patient quality of life. One of the most significant side effects of ADT is sarcopenia, which leads to a loss of skeletal muscle mass and function, resulting in a clinical disability syndrome known as obese frailty. Using aged mice, we developed a mouse model of ADT-induced sarcopenia that closely resembles the phenotype seen in patients, including loss of skeletal muscle strength, reduced lean muscle mass, and increased adipose tissue. Sarcopenia onset occurred about 6 weeks after castration and was blocked by a soluble receptor (ActRIIB-Fc) that binds multiple TGFβ superfamily members, including myostatin, growth differentiation factor 11, activin A, activin B, and activin AB. Analysis of ligand expression in both gastrocnemius and triceps brachii muscles demonstrates that each of these proteins is induced in response to ADT, in 1 of 3 temporal patterns. Specifically, activin A and activin AB levels increase and decline before onset of strength loss at 6 weeks after castration, and myostatin levels increase coincident with the onset of strength loss and then decline. In contrast, activin B and growth differentiation factor 11 levels increase after the onset of strength loss, 8-10 weeks after castration. The observed patterns of ligand induction may represent differential contributions to the development and/or maintenance of sarcopenia. We hypothesize that some or all of these ligands are targets for therapy to ameliorate ADT-induced sarcopenia in prostate cancer patients.

Topics: Activin Receptors, Type II; Activins; Animals; Bone Morphogenetic Proteins; Castration; Growth Differentiation Factors; Male; Mice; Mice, Inbred C57BL; Muscle Strength; Myostatin; Obesity; Sarcopenia; Transforming Growth Factor beta

Sarcopenia, a critical loss of muscle mass and function because of the physiological process of aging, contributes to disability and mortality in older adults. It increases the incidence of pathologic fractures, causing prolonged periods of hospitalization and rehabilitation. The molecular mechanisms underlying sarcopenia are poorly understood, but recent evidence suggests that increased transforming growth factor-β (TGF-β) signaling contributes to impaired satellite cell function and muscle repair in aged skeletal muscle. We therefore evaluated whether antagonism of TGF-β signaling via losartan, an angiotensin II receptor antagonist commonly used to treat high blood pressure, had a beneficial impact on the muscle remodeling process of sarcopenic mice. We demonstrated that mice treated with losartan developed significantly less fibrosis and exhibited improved in vivo muscle function after cardiotoxin-induced injury. We found that losartan not only blunted the canonical TGF-β signaling cascade but also modulated the noncanonical TGF-β mitogen-activated protein kinase pathway. We next assessed whether losartan was able to combat disuse atrophy in aged mice that were subjected to hindlimb immobilization. We showed that immobilized mice treated with losartan were protected against loss of muscle mass. Unexpectedly, this protective mechanism was not mediated by TGF-β signaling but was due to an increased activation of the insulin-like growth factor 1 (IGF-1)/Akt/mammalian target of rapamycin (mTOR) pathway. Thus, blockade of the AT1 (angiotensin II type I) receptor improved muscle remodeling and protected against disuse atrophy by differentially regulating the TGF-β and IGF-1/Akt/mTOR signaling cascades, two pathways critical for skeletal muscle homeostasis. Thus, losartan, a Food and Drug Administration-approved drug, may prove to have clinical benefits to combat injury-related muscle remodeling and provide protection against disuse atrophy in humans with sarcopenia.

Topics: Angiotensin Receptor Antagonists; Animals; Insulin-Like Growth Factor I; Losartan; Male; Mice; Mice, Inbred C57BL; Muscle, Skeletal; Muscular Disorders, Atrophic; Proto-Oncogene Proteins c-akt; Receptor, Angiotensin, Type 1; Sarcopenia; Signal Transduction; TOR Serine-Threonine Kinases; Transforming Growth Factor beta

Abnormal levels of reactive oxygen species (ROS) and inflammatory cytokines have been observed in the skeletal muscle during muscle wasting including sarcopenia. However, the mechanisms that signal ROS production and prolonged maintenance of ROS levels during muscle wasting are not fully understood. Here, we show that myostatin (Mstn) is a pro-oxidant and signals the generation of ROS in muscle cells. Myostatin, a transforming growth factor-β (TGF-β) family member, has been shown to play an important role in skeletal muscle wasting by increasing protein degradation. Our results here show that Mstn induces oxidative stress by producing ROS in skeletal muscle cells through tumor necrosis factor-α (TNF-α) signaling via NF-κB and NADPH oxidase. Aged Mstn null (Mstn(-/-) ) muscles, which display reduced sarcopenia, also show an increased basal antioxidant enzyme (AOE) levels and lower NF-κB levels indicating efficient scavenging of excess ROS. Additionally, our results indicate that both TNF-α and hydrogen peroxide (H(2) O(2) ) are potent inducers of Mstn and require NF-κB signaling for Mstn induction. These results demonstrate that Mstn and TNF-α are components of a feed forward loop in which Mstn triggers the generation of second messenger ROS, mediated by TNF-α and NADPH oxidase, and the elevated TNF-α in turn stimulates Mstn expression. Higher levels of Mstn in turn induce muscle wasting by activating proteasomal-mediated catabolism of intracellular proteins. Thus, we propose that inhibition of ROS induced by Mstn could lead to reduced muscle wasting during sarcopenia.

Topics: Aging; Animals; Antioxidants; Cell Proliferation; Humans; Hydrogen Peroxide; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle, Skeletal; Myostatin; NADPH Oxidases; NF-kappa B; Oxidative Stress; Primary Cell Culture; Proteasome Endopeptidase Complex; Proteolysis; Reactive Oxygen Species; Sarcopenia; Signal Transduction; Transforming Growth Factor beta; Tumor Necrosis Factor-alpha