Cholesterol metabolism is a potential therapeutic target in Duchenne Muscular Dystrophy

Abstract

Background: Duchenne Muscular Dystrophy (DMD) is a lethal muscle disease detected in approximately 1:5000 male births. DMD is caused by mutations in the DMD gene, encoding a critical protein that link the cytoskeleton and the extracellular matrix in skeletal and cardiac muscles. The primary consequence of the disrupted link between the extracellular matrix and the myofiber actin cytoskeleton is thought to involve sarcolemma destabilization, perturbation of Ca+2 homeostasis, activation of proteases, mitochondrial damage and tissue degeneration. A recently emphasized secondary aspect of the dystrophic process is a progressive metabolic change of the dystrophic tissue; however, the mechanism and nature of the metabolic dysregulation is yet poorly understood. In this study, we characterized a molecular mechanism of metabolic perturbation in DMD. Methods: We sequenced plasma miRNA in a DMD cohort, comprising of 54 DMD patients treated or not by glucocorticoid, compared to 27 healthy controls, in three age groups. We developed an original approach for the biological interpretation of miRNA dysregulation, and produced a novel hypothesis concerning metabolic perturbation in DMD. We then used the mdx mouse model for DMD for the investigation of this hypothesis. Results: We identified 96 dysregulated miRNAs, of which 74 were up- and 22 down-regulated in DMD. We confirmed the dysregulation in DMD of Dystro-miRs, Cardio-miRs and a large number of the DLK1-DIO3 miRNAs. We also identified numerous dysregulated miRNAs, yet unreported in DMD. Bioinformatics analysis of both target and host genes for dysregulated miRNAs predicted that lipid metabolism might be a critical metabolic perturbation in DMD. Investigation of skeletal muscles of the mdx mouse uncovered dysregulation of transcription factors of cholesterol and fatty acid metabolism (SREBP1 and SREBP2), perturbation of the mevalonate pathway, and accumulation of cholesterol. Elevated cholesterol level was also found in muscle biopsies of DMD patients. Treatment of mdx mice with Simvastatin, a cholesterol-reducing agent, normalized these perturbations and partially restored the dystrophic parameters. Conclusion: This investigation supports that cholesterol metabolism and the mevalonate pathway are potential therapeutic targets in DMD.

Rebuttal to: Simvastatin Treatment Does Not Ameliorate Muscle Pathophysiology in a Mouse Model for Duchenne Muscular Dystrophy, Verhaart et al. 2020

“…More recently, we have shown that cardiac function in the mdx mouse is also improved by simvastatin, due in part to the prevention of fibrosis [3]. In strong support of our findings, two recent studies have independently validated our results by showing positive effects of simvastatin treatment in mdx mice [4,5]. In one of these studies, significant improvements in muscle function (force and fatigue resistance), as well as reduced inflammation, fibrosis and plasma CK were comparable to those in our original paper [5].…”

“…In one of these studies, significant improvements in muscle function (force and fatigue resistance), as well as reduced inflammation, fibrosis and plasma CK were comparable to those in our original paper [5]. In the other paper, widespread perturbations in muscle cholesterol metabolism were discovered in DMD and mdx muscles, and these changes were normalized by simvastatin treatment in dystrophic mice along with reduced plasma CK [4]. Together, our findings and those from two independent research groups provide robust evidence that cholesterol metabolism is abnormal in dystrophic muscles and that simvastatin could provide a novel, inexpensive, and widely used treatment for DMD.…”

Complexity of skeletal muscle degeneration: multi-systems pathophysiology and organ crosstalk in dystrophinopathy

“…New treatment approaches to ameliorate the dystrophic phenotype include (i) pharmacological interventions using drugs that modulate the immune response and inflammation, abnormal ion homeostasis, impaired excitation-contraction coupling, cellular growth patterns, abnormal metabolic pathways, cholesterol metabolism, oxidative stress and cardio-respiratory complications [8,132,155,209,214];…”

Author’s Response to: Rebuttal to: Simvastatin Treatment Does Not Ameliorate Muscle Pathophysiology in a Mouse Model for Duchenne Muscular Dystrophy, Verhaart et al. 2020

“…Whitehead et al cite [1] two recent papers that confirm the therapeutic effects of simvastatin treatment in the mdx mouse model [4,5]. However, the first citation does not mention a dose [4], while the second used delivery via oral gavage of 20 mg/kg simvastatin [5], which would amount to a higher dose of simvastatin than the one we or Whitehead et al used.…”

“…Whitehead et al cite [1] two recent papers that confirm the therapeutic effects of simvastatin treatment in the mdx mouse model [4,5]. However, the first citation does not mention a dose [4], while the second used delivery via oral gavage of 20 mg/kg simvastatin [5], which would amount to a higher dose of simvastatin than the one we or Whitehead et al used. While these studies confirm the therapeutic effect of simvastatin treatment in mdx mice, they do not confirm that this can be achieved at doses that are in the range of what humans use.…”