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Cromoglicato dissódico protege as fibras musculares de camundongos com distrofia muscular (27/02/2008)

Brasil - o cromoglicato dissódico é uma droga utilizada na prevenção de alergias respiratórias. Neste experimento a droga foi injetada por via intraperitoneal em camundongos com distrofia muscular por 15 dias a partir do 14^o dia de vida. Os animais tratados apresentaram maior quantidade de fibras musculares íntegras, demonstrando um efeito protetor da droga sobre os músculos.

Uso do deflazacort na distrofia muscular de Duchenne: acompanhamento de 8 anos (16/02/08)

Canadá - os autores coletaram as informações de 79 pacientes com Duchenne, 37 dos quais receberão tratamento com deflazacort (com média de duração do tratamento de 66 meses). Os pacientes tratados apresentaram melhores resultados: caminharam por mais tempo, apresentavam melhor função cardíaca e menor incidência de cardiomiopatia. Além disso apresentavam menor incidência de escoliose, sem necessidade de cirurgia de coluna. A incidência de fraturas foi semelhante nos tratados e nos não tratados mas fraturas de coluna só foram observadas nos que receberam deflazacort. Os resultados evidenciam os benefícios do uso de corticóides na distrofia muscular de Duchenne. O resumo em inglês do artigo pode ser lido abaixo:

(Pediatric Neurology, Volume 38, Issue 3, March 2008, Pages 200-206) Deflazacort Use in Duchenne Muscular Dystrophy: An 8-Year Follow-Up

Sylvie Houde, Michèle Filiatrault, Anne Fournier, Julie Dubé, Sylvie D’Arcy, Denis Bérubé, Yves Brousseau, Guy Lapierre and Michel Vanasse - Canada

Data reported here were collected over an 8-year period for 79 Duchenne muscular dystrophy patients, 37 of whom were treated with deflazacort. Mean length of treatment was 66 months. Treated boys stopped walking at 11.5 + 1.9 years, compared with 9.6 + 1.4 years for untreated boys. Cardiac function was better preserved with the use of deflazacort, as shown by a normal shortening fraction in treated (30.8 + 4.5%) vs untreated boys (26.6 + 5.7%, P < 0.05), a higher ejection fraction (52.9 + 6.3% treated vs 46 + 10% untreated), and lower frequency of dilated cardiomyopathy (32% treated vs 58% untreated). Scoliosis was much less severe in treated (14 + 2.5°) than in untreated boys (46 + 24°). No spinal surgery was necessary in treated boys. Limb fractures were similarly frequent in treated (24%) and untreated (26%) boys, but vertebral fractures occurred only in the treated group (7/37) (compared with zero for the untreated group). In both groups, body weight excess tripled between the ages of 8 and 12 years. All untreated patients grew normally (>4 cm/year), as opposed to only 15% of treated boys. Deflazacort improves cardiac function, prolongs walking, and seems to eliminate the need for spinal surgery, although vertebral fractures and stunted growth occur. The overall impact on quality of life appears positive.

Uso de um componente do chá verde desde o nascimento melhora as alterações patológicas e a função muscular de camundongos com distrofia muscular (16/02/08)

Japão - músculos com distrofia sofrem stress oxidativo; chá verde é um antioxidante e reduz as alterações musculares em camundongos com distrofia muscular. Neste experimento os camundongos foram tratados por via subcutânea com epigallocatechin-3-gallate (EGCG), um componente do chá verde, por 8 semanas após o nascimento. Houve redução da CK, melhora das alterações patológicas e aumento da força muscular

Portador de Distrofia Muscular de Duchenne irá lançar seu livro esta semana (11/02/08)

Franca - Fabrício Silva Rodrigues, portador de distrofia muscular de Duchenne, irá lançar seu livro "À Vida", no dia 16 de fevereiro de 2008 às 20:00hs na cidade de Franca, SP no teatro do SESI na Av. Santa Cruz, 2870 Vila Santa Cruz. O livro é composto de poemas e crônicas simples e poéticas onde o autor compartilha experiências belas e mostra a exuberância da Vida.

Redução da fibrose dos músculos e do coração de camundongos com distrofia muscular tratados com halofuginose (08/02/08)

Canadá e Israel - a droga halofuginose tem sido experimentada para reduzir a formação de fibrose em diversas doenças. Pesquisadores utilizaram a droga em camundongos com distrofia muscular e observaram redução da fibrose nos músculos esqueléticos e no coração com aumento da função cardíaca e respiratória. os autores concluiram que a halofuginose demonstrou melhorar as funções vitais candidatando-se como um potencial tratamento das distrofias musculares. O resumo em inglês da pesquisa pode ser lido abaixo:

(Am J Physiol Heart Circ Physiol, Feb 2008) Functional resolution of fibrosis in mdx mouse dystrophic heart and skeletal muscle by halofuginone

Kyla D Huebner, Davinder S Jassal, Orna Halevy, Mark Pines, and Judy E Anderson - Canada and Israel

The effect of halofuginone (Halo) on established fibrosis inolder mdx dystrophic muscle was investigated. Mice (8-9-months)treated with Halo (or saline in controls) for 5, 10 or 12 weeks were assessed weekly for grip strength and voluntary running. Echocardiography was performed at 0, 5, and 10 weeks. Respiratory function and exercise-induced muscle damage were tested. Heart, quadriceps, diaphragm and tibialis anterior muscles were collectedto study fibrosis, collagen I and III expression, collagen contentusing a novel collagenase-digestion method, and cell proliferation. Hepatocyte growth factor (HGF) and alpha-smooth muscle actin(SMA) proteins were assayed in quadriceps. Halo decreased fibrosis, collagen I and III expression, collagen protein and SMA contentafter 10 weeks treatment. Muscle-cell proliferation increasedat 5 weeks, and HGF increased by 10 weeks treatment. Halo markedlyimproved cardiac function and respiratory function, and reduceddamage and improved recovery from exercise. The overall impactof already-established dystrophy in cardiac and skeletal muscleswas reduced. Marked improvements in vital-organ functions implicateHalo as a strong candidate drug to reduce morbidity and mortalityin DMD.

N-acetilcisteína melhora as alterações patológicas dos camundongos com distrofia muscular (08/02/08)

Austrália - a N-acetilcisteína é muito utilizada para tratamento de doenças respiratórias. Esta droga tem ação antioxidante. Camundongos com distrofia muscular e tratados com N-acetilcisteína apresentaram menor stress oxidativo, redução de mediadores de agressão muscular e melhora das alterações patológicas dos músculos. O estudo sugere que a N-acetilcisteína pode ter potencial para tratamento da distrofia muscular de Duchenne. O resumo em inglês desta pesquisa pode ser lido abaixo:

(J. Physiol., Feb 2008) N-acetylcysteine ameliorates skeletal muscle pathophysiology in mdx mice

Nicholas Paul Whitehead, Catherine Pham, Othon L Gervasio, and David G. Allen - Australia

Duchenne muscular dystrophy (DMD) is a severe degenerative muscledisease caused by a mutation in the gene encoding dystrophin,a protein linking the cytoskeleton to the extracellular matrix. In this study we investigated whether the antioxidant N-acetylcysteine(NAC) provided protection against dystrophic muscle damage in the mdx mouse, an animal model of DMD. In isolated mdx muscles,NAC prevented the increased membrane permeability and reducedthe force deficit associated with stretch-induced muscle damage.Three week old mdx mice were treated with NAC in the drinkingwater for 6 weeks. Dihydroethidium staining showed that NACtreatment reduced the concentration of reactive oxygen species(ROS) in mdx muscles. This was accompanied by a significantdecrease in centrally nucleated fibres in muscles from NAC-treatedmdx mice. Immunoblotting showed that NAC treatment decreasedthe nuclear protein expression of NF-B, a transcription factorinvolved in pro-inflammatory cytokine expression. Finally,we show that NAC treatment reduced caveolin-3 protein levelsand increased the sarcolemmal expression of -dystroglycan andthe dystrophin homologue, utrophin. Taken together, our findingssuggest that ROS play an important role in the dystrophic pathogenesis,both in terms of activating damage pathways and in regulating the expression of some dystrophin-associated membrane proteins.These results offer the prospect that antioxidants such asNAC could have therapeutic potential for DMD patients.

O uso de corticóides no tratamento da distrofia muscular de Duchenne (08/02/2008)

USA - os autores fazem uma revisão sistemática das publicações a cerca do uso de corticóides na distrofia muscular de Duchenne; as pesquisas selecionadas foram a que preencheram critérios internacionais de confiança, permitindo tirar conclusões sobre este tratamento. Os autores concluem que os corticóides aumentam a força muscular comprovadamente em estudos de curta duração; o esquema de tratamento considerado mais efetico foi a prednisolona na dose de 0,75mg/Kg. Os efeitos colaterais a curto prazo foram frequentes mas não severos. De modo geral as revisões demonstram que os corticóides são efetivos e que devem ser utilizados no tratamento da distrofia muscular de Duchenne apesar dos efeitos colaterais.

Nível sanguíneo de miostatina em doentes com distrofia muscular de Duchenne (02/02/2008)

Japão - nesta carta ao editor este grupo japonês analisou o nível sanguíneo em pacientes com Duchenne. Amiostatina inibe o crescimento muscular. Camundongos com distrofia e tratados com inibidores da miostatina apresentaram melhora. A dosagem de miostatina variou muito entre os 42 pacientes estudados, não se relacionando com o tipo de mutação, nem com outros critérios laboratoriais e clínicos. Os autores sugerem cautela com o uso de inibidores da miostatina em pacientes com a doença em especial nos que apresentam altos níveis sanguíneos desta proteína. O texto completo da carta em inglês pode ser lido abaixo:

(Clinica Chimica Acta, 2008) Wide ranges of serum myostatin concentrations in Duchenne muscular dystrophy patients - Letter to the editor

Hiroyuki Awano, Yasuhiro Takeshima, Yo Okizuka, Kayoko Saiki, Mariko Yagi, Masafumi Matsuo - Japan

Duchenne muscular dystrophy (DMD), a common inherited myopathy that affects approximately 1 in 3,500 males, is characterized by progressive muscle wasting due to a deficiency in muscle dystrophin. DMD progresses with a rather uniform pattern of muscle weakness; i.e., DMD causes affected individuals to lose their ability to walk by the age of 12 y, and patients succumb during their twenties due to either respiratory or cardiac failure. The deficiency in dystrophin is caused by translational reading frame shift or nonsense mutations in the dystrophin gene [1]. However, the existence of a modifying gene has been suggested by the identification of unusually mild DMD phenotypes [2-4]. Although some phenotypic variability may arise due to environmental factors, such as diet or exercise, genetic components are likely to contribute to this variability. Myostatin, also known as growth and differentiation factor 8 (GDF8), is a muscle-specific secreted peptide that limits muscle growth [5,6]. However, genotyping of the myostatin gene failed to disclose any nucleotide changes that behaved as a phenotypic modifier of DMD [7]. Remarkably, blocking endogenous myostatin has been shown to result in anatomic, biochemical, and physiologic improvements in the dystrophic phenotype of mdx mice, a mouse model for DMD, including particularly prominent enlarged fiber diameters and greatly reduced fatty fibrosis [8-10]. These results suggest that blocking endogenous myostatin is a potential strategy to treat DMD [11]. We examined the hypothesis that serum myostatin is increased in DMD, thereby enabling treatment by myostatin blockage. Forty-two DMD patients followed at Kobe University Hospital were enrolled in this study. All but 1 of the mutations in the dystrophin gene were found to introduce premature stop codons in the dystrophin mRNA: 24 cases with mutations that induced a translational reading frame-shift due to exon deletion or duplication; 5 cases with nonsense mutations; 7 cases with exon mutations involving one or a few nucleotides deleted or inserted; 3 cases with intron mutations that induced splicing errors; and one case with an abnormal chromosome (Table 1). The subjects’ ages ranged from 1 to 22 y (average: 8.3 y). Regular clinical checkups, including determination of serum creatine kinase (CK) concentrations, were performed at the outpatient clinic. All protocols were approved by the ethics committee of the Kobe University School of Medicine. Blood samples were taken after written informed consent was obtained from all patients, and serum was separated using a clinical centrifuge. Serum myostatin was measured using the Human Myostatin ELISA (Prodomain Specific) kit purchased from BioVendor Laboratory Medicine, Inc. (Bmo, Czech Republic). The upper limit of determination was 50 ng/ml, and normal adults have serum concentrations of 0.19 to 9.02 ng/ml (BioVendor Laboratory Medicine, Inc.). The Pearson product-moment coefficient was calculated to quantify the relationship. Serum myostatin concentrations in DMD patients ranged from 1.1 to >50 ng/dl (Table 1). Remarkably, 13 samples were >50 ng/ml, and the lowest concentration was 1.1 ng/ml (Table 1). Though age differences were examined in 2 conditions either including or deleting 13 samples with >50 ng/ml, no significant correlationship between age and serum myostatin concentration was found (Fig. 1). We next examined whether concentrations of myostatin were related to the type or location of mutations in the dystrophin gene. Though serum myostatin concentrations were compared based on their mutation types (exon deletion/duplication or others), no clear difference between two groups was revealed (Fig. 1). There found no significant difference in serum myostatin concentration between patients with mutation in the 5’ and 3’ regions of the dystrophin gene (Table 1). Considering that myostatin is an inhibitor of muscle growth, cases with high serum myostatin concentrations were predicted to present rather severe phenotypes. Transgenic overexpression of myostatin in mice was shown to result in cachexia [12]. However, the ages when DMD patients with high myostatin concentrations became wheelchair-bound were not different from those of patients with low myostatin concentrations, and signs of muscle weakness appeared mostly between ages 4 and 5. Furthermore, serum CK concentrations were not significantly lower in DMD cases with high myostatin concentrations than in those with low concentrations (Table 1). This indicates that serum myostatin did not modify the DMD phenotype even though blocking endogenous myostatin has been shown to result in improvements in the dystrophic phenotype of mdx mice [8-10]. In this study, we measured myostatin that reacted with a monoclonal antibody recognizing the prodomain of myostatin. Considering that myostatin is secreted as an inactive propeptide and is cleaved to produce the active form, further studies would be required to measure active or latent myostatin individually. Expression of the myostatin gene has been examined previously in skeletal muscle by measuring mRNA and protein concentrations [13]. Serum myostatin concentration has been determined by the Western blot analysis in a patient with a mutation in the myostatin gene, disclosing an absence of myostatin [14]. Furthermore the Western blot analysis disclosed that serum myostatin concentration was lower than that of rat [14]. But no further study has been conducted on serum myostatin concentrations. Our results disclosed a wide range in serum myostatin concentrations in DMD patients. Though myostatin blockage is attracting attention as a novel target for increasing muscle growth in cases of DMD [11], our results suggest that myostatin blockage therapy would only be effective in DMD cases involving high serum myostatin concentrations. Therefore, myostatin blockage therapy should be applied carefully as a treatment for DMD.

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