Similar Efficacy from Specific and Non-Specific Mineralocorticoid Receptor Antagonist Treatment of Muscular Dystrophy Mice

Abstract

Background Combined treatment with an angiotensin-converting enzyme inhibitor and a mineralocorticoid receptor (MR) antagonist improved cardiac and skeletal muscle function and pathology in a mouse model of Duchenne muscular dystrophy. MR is present in limb and respiratory skeletal muscles and functions as a steroid hormone receptor. Objective The goals of the current study were to compare the efficacy of the specific MR antagonist eplerenone with the non-specific MR antagonist spironolactone, both in combination with the angiotensin-converting enzyme inhibitor lisinopril. Methods Three groups of n=18 dystrophin-deficient, utrophin-haploinsufficient male mice were given chow containing: lisinopril plus spironolactone, lisinopril plus eplerenone, or no drug, from four to 20 weeks-of-age. Eighteen C57BL/10 male mice were used as wild-type controls. In vivo measurements included cardiac magnetic resonance imaging, conscious electrocardiography, and grip strength. From each mouse in the study, diaphragm, extensor digitorum longus, and cardiac papillary muscle force was measured ex vivo, followed by histological quantification of muscle damage in heart, diaphragm, quadriceps, and abdominal muscles. MR protein levels were also verified in treated muscles. Results Treatment with specific and non-specific MR antagonists did not result in any adverse effects to dystrophic skeletal muscles or heart. Both treatments resulted in similar functional and pathological improvements across a wide array of parameters. MR protein levels were not reduced by treatment. Conclusions These data suggest that spironolactone and eplerenone show similar effects in dystrophic mice and support the clinical development of MR antagonists for treating skeletal muscles in Duchenne muscular dystrophy.

Mineralocorticoid receptor antagonists improve membrane integrity independent of muscle force in muscular dystrophy

“…2A). MRcko/mdx diaphragm-specific force reached 78% of the specific force of wild-type controls (185.9 ± 17.2 mN/mm 2 ) measured separately as an independent cohort, consistent with the ∼80% of normal wild-type force obtained with MR antagonists in 20-week-old dystrophic mice (6,7). The Cre−/mdx diaphragm-specific force was 64% of the specific force in the wild-type controls.…”

“…We have now demonstrated that the MR is present in normal and dystrophic skeletal muscles, that the MR functions in regulation of gene expression in normal human myotubes and that MR antagonist treatment of dystrophic mice leads to conserved in vivo gene expression changes (19,20). We have also shown that MR antagonists prevent ongoing dystrophic muscle damage in vivo and in vitro, supporting these drugs act at an early stage of the pathogenic process (6,7,20). We have previously demonstrated that inflammatory cells present in damaged muscles contain high levels of the enzyme required for aldosterone synthesis and that local levels of aldosterone are increased in dystrophic muscles and therefore may contribute to chronic muscle damage (21).…”

“…Angiotensinconverting enzyme inhibitors act upstream of the MR to inhibit aldosterone production and have been shown to delay cardiac dysfunction in Duchenne muscular dystrophy (DMD) patients (4,5). We have repeatedly demonstrated that treatment with an MR antagonist plus an angiotensin-converting enzyme inhibitor results in therapeutic benefits on both heart and skeletal muscles in mouse models of DMD, although a role for MR in skeletal muscles has not been previously investigated (6)(7)(8).…”

Eplerenone Implantation Improved Adipose Dysfunction Averting RAAS Activation and Cell Division

“…We used AK Scientific, Inc., NX-999 Eplerenone (60 mg/pellet) 90day release, which delivers 0.67 mg/day of the drug. On the other hand, the protocols used by Lowea et al (37), they expect that the animals consume an Eplerenone estimated dose of 200 mg/kg × day which corresponds to 0.42 mg/day. Thus, in an animal model of diet-induced obesity, the administration of eplerenone via a subcutaneous pellet to modulate adipocyte dysfunction might be a suitable strategy.…”

Muscle Twitch Kinetics Are Dependent on Muscle Group, Disease State, and Age in Duchenne Muscular Dystrophy Mouse Models

“…The specific goal of this study was to determine if disease state impacts the kinetics of skeletal muscle twitch contractions, in different models, in different muscle groups, and at different ages, using Duchenne muscular dystrophy as the disease model. The mice used in this retrospective studies were 10 weeks (Lowe et al, 2015), 20 weeks (Lowe et al, 2016) and 52 weeks of age (Lowe et al, 2018). The genotypes of the mice were wild-type C57BL/10 (C57), utrophin haplo-insufficient "het, " and dystrophin-deficient mdx.…”