Endocrine Abstracts

Introduction: Duchenne Muscular Dystrophy (DMD) is a lethal genetic disease characterised by chronic inflammation and progressive muscle wasting. Potent anti-inflammatory glucocorticoids (GCs) are highly effective in the management of DMD, but their application is limited by severe metabolic side effects. The enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) potently activates and amplifies the actions of GCs and is synergistically upregulated with inflammation, exacerbating GC-induced metabolic side effects. Vamorolone is a novel dissociated anti-inflammatory steroid developed for the treatment of DMD while exhibiting reduced side effects relative to traditional glucocorticoids. We hypothesised that Vamorolone possesses a reduced synergistic capacity to upregulate 11β-HSD1 in DMD inflammation, limiting GC amplification and off-target GC induced side effects.

Methods: LHCN-M2 human skeletal muscle cells were cultured and differentiated for 10 days into multinucleated myotubes. LHCN-M2 myotubes were treated with either TNFα (10 mg/mL), Prednisolone (100nM), Vamorolone (200nM) or at a combination for 4 hours for gene expression (qRT-PCR) or 48 hours for 11β-HSD1 activity (TLC).

Results: While Prednisolone (100nM) and Vamorolone (200nM) did not alter 11β-HSD1 expression or activity alone, both compounds showed a significant synergistic induction of 11β-HSD1 expression and activity when combined with TNFα (10 ng/ml) relative to TNFα alone, with Vamorolone showing a modestly lower response than Prednisolone. In contrast, classic GC induced genes (such as GILZ) that were induced by both Prednisolone and Vamorolone were abrogated following TNFα exposure. Whilst synergy responses were preserved following Vamorolone treatment, skeletal muscle catabolic genes FOXO1 and Trim63 showed a marked reduction in response relative to Prednisolone, both alone and in combination with TNFα.

Conclusions: Vamorolone demonstrates anti-inflammatory activity while limiting 11β-HSD1 activation and downstream muscle catabolic signalling, supporting its potential as a dissociated steroid that limits GCs amplification and associated muscle wasting in DMD.