Oxandrolone enhances skeletal muscle myosin synthesis and alters global gene expression profile in Duchenne muscular dystrophy

Abstract

(DMD) involves an imbalance between the rates of synthesis and degradation of muscle proteins. Although previous studies have suggested that oxandrolone may be beneficial in DMD, the mechanism of action of oxandrolone on muscle in DMD remains unclear. To address these issues, we combined stable isotope studies and gene expression analysis to measure the fractional synthesis rate of myosin heavy chain (MHC), the key muscle contractile protein, the transcript levels of the isoforms of MHC, and global gene expression profiles in four children with DMD before and after 3 mo of treatment with oxandrolone. Gastrocnemius muscle biopsies and blood samples were collected during the course of a primed 6-h continuous infusion of L-[U-13 C]leucine on two separate occasions, before and after the 3-mo treatment with oxandrolone (0.1 mg ⅐ kg Ϫ1 ⅐ day Ϫ1 ). Gene expression analysis was done with microarrays and RT-qPCR. In response to the treatment, MHC synthesis rate increased 42%, and this rise was accounted for, at least in part, by an upregulation of the transcript for MHC8 (perinatal MHC). Gene expression data suggested a decrease in muscle regeneration as a consequence of oxandrolone therapy, presumably because of a decrease in muscle degeneration. These findings suggest that 1) oxandrolone has a powerful protein anabolic effect on a key contractile protein and 2) larger and longer-term studies are warranted to determine whether these changes translate into meaningful therapy for these patients. microarray; stable isotope; mass spectrometry DUCHENNE MUSCULAR DYSTROPHY (DMD) is a severe and progressive form of human muscular dystrophy with a lethal outcome. Although the absence of the protein dystrophin, which is part of a glycoprotein complex located on the intracellular surface of the cellular membrane, was identified as the molecular basis of the disease (25, 28), and despite advances in our understanding of dystrophin function, the precise pathogenesis of the severe muscle damage remains unclear. The most striking manifestations of this disorder are loss of skeletal muscle mass and strength, resulting in severe disability. Previous studies in DMD have suggested that the loss of muscle is likely the result of an imbalance between muscle protein synthesis and degradation (18,42). In DMD, dystrophin deficiency is present in muscle from fetal life onward. However, the loss of muscle is progressive. The progressive nature of the muscle loss implies that there are crucial secondary factors that compound the problems caused by dystrophin deficiency. The gradual loss of regenerating capacity of muscle, which depends on protein synthesis, may be an important factor in this pathogenetic process (18,41,42).The absence of a cure for DMD underscores the importance of adjunctive therapeutic strategies. A recent study by Fenichel et al. (13) suggested an ameliorative effect of oxandrolone, an oral synthetic analog of testosterone, on muscle strength in DMD. Although a subsequent study by the same group did not find a significant ch...

Role of response gene to complement 32 in diseases

“…In contrast, oxandrolone, an anabolic steroid that reacts mainly with the androgen receptor, was found to down-regulate the expression of RGC-32 in gastrocnemius muscle samples from Duchenne muscular dystrophy patients [5].…”

Continuous mild heat stress induces differentiation of mammalian myoblasts, shifting fiber type from fast to slow

“…After DNase treatment, cDNAs were obtained by reverse transcription of 2 g of total RNA (Ready-to-Go T-primed first-strand kit; Amersham Biosciences, Piscataway, NJ). The primer sequences are listed in Table 1 (3,6,9,18,23,50). The level of mRNA expression was determined by quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) in a fluorescent temperature cycler (ABI Prism 7000; Applied Biosystems, Darmstadt, Germany).…”

Nanolipodendrosome-loaded glatiramer acetate and myogenic differentiation 1 as augmentation therapeutic strategy approaches in muscular dystrophy

“…Myopathies are muscular diseases causing pain and reducing muscular efficiency. [5][6][7][8][9][10][11] Muscular dystrophy (MD) as a myopathy relates to progressive (gradual) muscular weakness, degeneration and generation of muscular fibers, and probable substitution of muscular fibers for connective and adipose tissues, without nervous system interference. and respiratory failure.…”

“…So far, the mechanism of the drug effect, the age of the patient to be treated, and its optimal period have not been determined. 2,11,24,[27][28][29][30][31][32][33][34] Glatiramer acetate (GA), a synthetic drug with an average molecular mass of 6.4 KD and available on the market as Copaxone ® (Teva Pharmaceuticals, Petah Tikva, Israel), is used to treat multiple sclerosis (MS). This drug is a peptide combined with four amino acids (L-Alanin, L-Lysine, L-Glutamic acid, and L-Tyrosine) which reduces the progression of MS and the disability caused by it and its recurrence.…”

“…34 Recently, genetic researchers have been trying to find gene therapy and exon skipping methods to treat this disease, but the effect of these methods has not been proved yet. 11,16,24,34 Previous studies on this subject have documented the effectiveness of GA as a modulator of the immune system in MS. [9][10][11][27][28][29] According to the currently available data, GA displays a wide range of anti-inflammatory activities: immune modulation induced by Th2 cells and an increase in anti-inflammatory cytokines. 9,29 Also, using GA in parallel to the MyoD factor that plays a role in the determination and induction of satellite cells to myoblasts, muscular proliferation/ differentiation has been improved.…”