Targeting gut dysbiosis against inflammation and impaired autophagy in Duchenne muscular dystrophy

A growing body of evidence shows that the gut microbiota importantly regulates many body functions also through their interaction with the endocannabinoid system (ECS). Yet, the molecular mechanism through which gut microorganisms control the ECS is not clear and the potential involvement of the microbiota-ECS crosstalk in skeletal muscle disorders remains unknown. Here we show that the faecal microbiota composition is significantly altered in mdx mice, a widely used model of Duchenne muscular dystrophy (DMD). Accordingly, the plasma levels of key gut microbiota-related metabolites, including short-chain fatty acids (SCFAs) and ketone bodies (KBs), are reduced, whereas muscle ECS activity is increased. Treatment of mdx mice with sodium butyrate (NaB) prevented these alterations whilst rescuing the deficit of locomotor activity, and the associated increased inflammation and impaired muscle autophagy, to levels comparable to those observed with deflazacort (DFZ), a drug primarily used to treat DMD patients. In murine C2C12 myoblasts stimulated with lipopolysaccharide (LPS), NaB prevented the up-regulation of pro-inflammatory genes and endocannabinoid signaling at CB1 receptors in a manner dependent on its activation of GPR109A/HCA2 and PPARg receptors. In particular, LPS-induced upregulation of the expression of CB1 was accompanied by downregulation of miRNAs targeting this receptor, and this effect was reversed by NaB via GPR109A/HCA2 and PPARg activation. Finally, NaB exerted anti-inflammatory and pro-autophagic effects also in primary myoblasts isolated from DMD donors. This study reveals a mechanism through which a dysfunctional gut microbiota, by causing aberrant CB1 activity, underlies part of the pathological features of a mouse model of DMD, and may thus contribute to identify novel therapeutic strategies for this rare and untreatable disorder.