Functional and Molecular Effects of Arginine Butyrate and Prednisone on Muscle and Heart in the mdx Mouse Model of Duchenne Muscular Dystrophy

Abstract

BackgroundThe number of promising therapeutic interventions for Duchenne Muscular Dystrophy (DMD) is increasing rapidly. One of the proposed strategies is to use drugs that are known to act by multiple different mechanisms including inducing of homologous fetal form of adult genes, for example utrophin in place of dystrophin.Methodology/Principal FindingsIn this study, we have treated mdx mice with arginine butyrate, prednisone, or a combination of arginine butyrate and prednisone for 6 months, beginning at 3 months of age, and have comprehensively evaluated the functional, biochemical, histological, and molecular effects of the treatments in this DMD model. Arginine butyrate treatment improved grip strength and decreased fibrosis in the gastrocnemius muscle, but did not produce significant improvement in muscle and cardiac histology, heart function, behavioral measurements, or serum creatine kinase levels. In contrast, 6 months of chronic continuous prednisone treatment resulted in deterioration in functional, histological, and biochemical measures. Arginine butyrate-treated mice gene expression profiling experiments revealed that several genes that control cell proliferation, growth and differentiation are differentially expressed consistent with its histone deacetylase inhibitory activity when compared to control (saline-treated) mdx mice. Prednisone and combination treated groups showed alterations in the expression of genes that control fibrosis, inflammation, myogenesis and atrophy.Conclusions/SignificanceThese data indicate that 6 months treatment with arginine butyrate can produce modest beneficial effects on dystrophic pathology in mdx mice by reducing fibrosis and promoting muscle function while chronic continuous treatment with prednisone showed deleterious effects to skeletal and cardiac muscle. Our results clearly indicate the usefulness of multiple assays systems to monitor both beneficial and toxic effects of drugs with broad range of in vivo activity.

Intermittent glucocorticoid steroid dosing enhances muscle repair without eliciting muscle atrophy

“…An 8-week study of prednisolone in mdx mice improved specific force and decreased the number of centrally nucleated myofibers (9). However, 3 months of daily prednisone in mdx mice resulted in weight loss, reduced strength, and increased fibrosis in the heart, suggesting that longer, chronic administration may be problematic (10). Recently, it has been shown that GC steroids rely on Krüppel-like factor 15 (Klf15), a Krüppel like transcription factor, to mediate ergogenic muscle performance effects (11).…”

Examination of effects of corticosteroids on skeletal muscles of boys with DMD using MRI and MRS

“…8,9 MRI, in particular T2-weighted MRI, is sensitive to alterations in muscle chemistry and structure induced by processes like damage/inflammation and fat infiltration, [10][11][12][13][14][15][16][17] and therefore may have the potential to detect the effects of corticosteroid treatment on dystrophic muscles. Magnetic resonance spectroscopy (MRS) allows quantification of chemical compounds and can separate lipid and water components, allowing a more targeted investigation of skeletal muscles in DMD.…”

Pharmacologically Targeting the Primary Defect and Downstream Pathology in Duchenne Muscular Dystrophy

“…These can in part be attributed to reduced ROS-mediated activation of NF-B and its downstream targets, MMP-2 and -9 [133] (see section 3.3.1) Similar beneficial effects were observed using molsidomine (Corvasal ® ), the established drug for the treatment of coronary disease and pulmonary fibrosis which is metabolised into a NO donor in the liver [131]. However there have been subsequent reports that long term arginine supplementation reduces/abolishes these beneficial effects [134] and actually promotes fibrosis [135]. Furthermore, no improvement in cardiac disease has been observed following treatment designed to enhance arginine metabolism [134,136].…”

“…However there have been subsequent reports that long term arginine supplementation reduces/abolishes these beneficial effects [134] and actually promotes fibrosis [135]. Furthermore, no improvement in cardiac disease has been observed following treatment designed to enhance arginine metabolism [134,136]. It is therefore unlikely that pharmacological activators of the NO pathway constitute a realistic treatment for DMD.…”