Skeletal muscle-targeted Dgat2 knockdown improves systemic energy metabolism and ambulatory function in mice with dysferlin deficiency

Limb-girdle muscular dystrophies (LGMD) are human genetic diseases resulting from defects in dysferlin, a membrane associated protein present in many cell types. LGMDs are characterised by marked deposition of lipids in affected muscles and eventual infiltration of adipocytes between myofibers. We have previously reported significant changes in the muscle lipidome in dysferlin-deficient mice, especially triglycerides, with concomitant increases in Dgat2 , which encodes the protein that condenses diacylglycerol and fatty acyl-CoA to form triglyceride. The aim of this study was to determine the effect of DGAT2 inhibition in skeletal muscle on the progression of muscle wasting and pathology associated with dysferlinopathy. Dgat2 was inhibited in male BLA/J mice using skeletal muscle targeted adeno-associated virus delivery of a short hairpin RNA against Dgat2 (AAV-shRNA- Dgat2 ) prior to onset of myofiber adipose infiltration at 10 months of age. Measures of whole-body metabolism and functional ambulatory assessments were conducted 16–21 weeks after AAV administration, and skeletal muscle metabolism, muscle contractile function in situ and muscle histopathology were assessed at 23–26 weeks after AAV administration. AAV-shRNA- Dgat2 administration in BLA/J mice caused a mild reduction in body weight, whole-body fat mass and adipocyte infiltration within skeletal muscle. Indirect calorimetry analysis of metabolic efficiency revealed increased nighttime energy expenditure and decreased daytime activity in BLA/J mice treated with AAV-shRNA- Dgat2 . Functional assessments showed Dgat2 inhibition in muscle improved balance, coordination and rearing in BLA/J mice. While inhibiting muscle adipocyte formation improved some metabolic parameters, AAV-shRNA- Dgat2 administration did not alter skeletal muscle contractile force generation in situ, muscle fatty acid metabolism, or regeneration after BaCl₂-induced injury. DGAT2 is a determinant of pathological adipocyte infiltration and ambulatory function in dysferlinopathy, thereby expanding the mechanistic framework linking lipid metabolism, muscle composition, and functional decline. Further work is required to understand the mechanistic basis that underpins this relationship.