11β-HSD1 determines the extent of muscle atrophy in a model of acute exacerbation of COPD

Abstract

Muscle atrophy is an extra-pulmonary complication of acute exacerbations (AE) in chronic obstructive pulmonary disease (COPD). The endogenous production and therapeutic application of glucocorticoids (GCs) have been implicated as drivers of muscle loss in AE-COPD. The enzyme 11 beta-hydroxysteroid dehydrogenase 1 (11β-HSD1) activates GCs and contributes towards GC-induced muscle wasting. To explore the potential of 11βHSD1 inhibition to prevent muscle wasting here, the objective of this study was to ascertain the contribution of endogenous GC activation and amplification by 11βHSD1 in skeletal muscle wasting during AE-COPD. Emphysema was induced by intra-tracheal (IT) instillation of elastase to model COPD in WT and 11βHSD1/KO mice, followed by vehicle or IT-LPS administration to mimic AE. µCT scans were obtained prior and at study endpoint 48h following IT-LPS, to assess emphysema development and muscle mass changes, respectively. Plasma cytokine and GC profiles were determined by ELISA. In vitro myonuclear accretion and cellular response to plasma and GCs were determined in C2C12 and human primary myotubes. Muscle wasting was exacerbated in LPS-11βHSD1/KO animals compared to WT controls. RT-qPCR and western blot analysis showed elevated catabolic and suppressed anabolic pathways in muscle of LPS-11βHSD1/KO animals relative to WTs. Plasma corticosterone levels were higher in LPS-11βHSD1/KO animals, whilst C2C12 myotubes treated with LPS-11βHSD1/KO plasma or exogenous GCs displayed reduced myonuclear accretion relative to WT counterparts. This study reveals that 11β-HSD1 inhibition aggravates muscle wasting in a model of AE-COPD, suggesting that therapeutic inhibition of 11β-HSD1 may not be appropriate to prevent muscle wasting in this setting.

Possible Mechanisms Linking Obesity, Steroidogenesis, and Skeletal Muscle Dysfunction

“…The regulation of muscle atrophy induced by chronic GC exposure appears to be associated with the activity of enzyme 11-beta hydroxysteroid dehydrogenase 1 (11β-HSD1), which converts cortisone to cortisol. This enzyme is also involved in the development of GC-induced insulin resistance, a factor possibly contributing to muscle atrophy [ 109 , 110 ]. The effect of GCs on fast- and slow-twitch skeletal muscles is not similar: fast-twitch skeletal muscles are more susceptible to the negative impact of GCs ( Figure 3 ).…”