Simvastatin does not alleviate muscle pathology in a mouse model of Duchenne muscular dystrophy

Abstract

Background Duchenne muscular dystrophy (DMD) is an incurable disease, caused by the mutations in the DMD gene, encoding dystrophin, an actin-binding cytoskeletal protein. Lack of functional dystrophin results in muscle weakness, degeneration, and as an outcome cardiac and respiratory failure. As there is still no cure for affected individuals, the pharmacological compounds with the potential to treat or at least attenuate the symptoms of the disease are under constant evaluation. The pleiotropic agents, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, known as statins, have been suggested to exert beneficial effects in the mouse model of DMD. On the other hand, they were also reported to induce skeletal-muscle myopathy. Therefore, we decided to verify the hypothesis that simvastatin may be considered a potential therapeutic agent in DMD. Methods Several methods including functional assessment of muscle function via grip strength measurement, treadmill test, and single-muscle force estimation, enzymatic assays, histological analysis of muscle damage, gene expression evaluation, and immunofluorescence staining were conducted to study simvastatin-related alterations in the mdx mouse model of DMD. Results In our study, simvastatin treatment of mdx mice did not result in improved running performance, grip strength, or specific force of the single muscle. Creatine kinase and lactate dehydrogenase activity, markers of muscle injury, were also unaffected by simvastatin delivery in mdx mice. Furthermore, no significant changes in inflammation, fibrosis, and angiogenesis were noted. Despite the decreased percentage of centrally nucleated myofibers in gastrocnemius muscle after simvastatin delivery, no changes were noticed in other regeneration-related parameters. Of note, even an increased rate of necrosis was found in simvastatin-treated mdx mice. Conclusion In conclusion, our study revealed that simvastatin does not ameliorate DMD pathology.

Co-Administration of Simvastatin Does Not Potentiate the Benefit of Gene Therapy in the mdx Mouse Model for Duchenne Muscular Dystrophy

“…Analysis of myofiber damage was assessed by IgG staining, which is nonspecifically attached to necrotic myofibers [19]. In agreement with [14], we detected a significantly increased level of necrotic myofibers in the GA muscle of the mdx simvastatin group, as compared to the untreated mdx mice. In contrast, no effect of simvastatin on GA muscle myofiber necrosis level was detected in mice that were treated by the low titer microdystrophin (Figure 2c,d).…”

“…In (2), the analysis of the simvastatin-only group, we observed a reduced diaphragm fibrosis level (Figure 2a,b) and a trend toward reduced mCK and myom−3 levels (Figure 3a,b) in the simvastatin treated compared to untreated mdx group. The detection of necrotic fibers provided, however, seemingly contradicting results, because we detected (in agreement with [14]) increased necrosis rate by simvastatin treatment in both the GA and the TA muscles. No effect of simvastatin-only was observed in the escape test group, while a slight force drop was recorded in the limb grip test.…”

“…In 2020, two research groups concluded that simvastatin did not ameliorate disease pathology in mdx mice [15]. Similarly, Mucha and colleagues [14] were not able to confirm the positive effect of simvastatin in the mdx model. In a rebuttal letter, Whitehead and coauthors [16] responded that in the Verhaart study [15] the plasma level of simvastatin was below a threshold for therapeutic efficacy.…”

“…This makes the use of statin contra-intuitive, in the context of muscular dystrophy. In this context, the attempts to reproduce these promising results by other independent laboratories had failed, since the treated mdx mice did not present muscle functional improvement [14,15]. These negative results are explained possibly by the relatively low level of simvastatin that was measured in the treated mice [16], yet, the failure to validate the early results, associated with the statins' notorious propensity to cause muscle pain in the general population [13], raised doubt on the therapeutic hopes of simvastatin administration in DMD.…”

miR-378 affects metabolic disturbances in the mdx model of Duchenne muscular dystrophy

“…However, because White et al 59 suggested that the elevation of lipids in DMD dogs progresses with age, it would be of particular importance for future studies to further investigate dyslipidemia features in older dystrophic mice, not only under normal conditions but also when animals are kept on an obesogenic diet. Importantly, lipid-lowering agents such as statins, have already been proposed to exert beneficial effects in DMD 62 , 63 ; however, our 64 and other studies 65 did not confirm the rationale to utilize simvastatin, at least, to ameliorate muscle-related DMD symptoms. Our study indicated reduced hepatic expression of the key lipogenic factors, Scd1 and Fasn , similarly to the results obtained in skeletal muscles of mdx animals 66 .…”