Mitochondrial bioenergetic dysfunction in the D2.mdx model of Duchenne muscular dystrophy is associated with microtubule disorganization in skeletal muscle

Abstract

In Duchenne muscular dystrophy, a lack of dystrophin leads to extensive muscle weakness and atrophy that is linked to cellular metabolic dysfunction and oxidative stress. This dystrophinopathy results in a loss of tethering between microtubules and the sarcolemma. Microtubules are also believed to regulate mitochondrial bioenergetics potentially by binding the outer mitochondrial membrane voltage dependent anion channel (VDAC) and influencing permeability to ADP/ATP cycling. The objective of this investigation was to determine if a lack of dystrophin causes microtubule disorganization concurrent with mitochondrial dysfunction in skeletal muscle, and whether this relationship is linked to altered binding of tubulin to VDAC. In extensor digitorum longus (EDL) muscle from 4-week old D2.mdx mice, microtubule disorganization was observed when probing for α-tubulin. This cytoskeletal disorder was associated with a reduced ability of ADP to stimulate respiration and attenuate H 2 O 2 emission relative to wildtype controls. However, this was not associated with altered α-tubulin-VDAC2 interactions. These findings reveal that microtubule disorganization in dystrophin-deficient EDL is associated with impaired ADP control of mitochondrial bioenergetics, and suggests that mechanisms alternative to α-tubulin's regulation of VDAC2 should be examined to understand how cytoskeletal disruption in the absence of dystrophin may cause metabolic dysfunctions in skeletal muscle.

Muscle weakness precedes atrophy during cancer cachexia and is associated with muscle-specific mitochondrial stress

“…Similar assay design considerations have been essential for identifying precise mitochondrial bioenergetic contributions to cellular function in our previous research (17)(18)(19)(20). Using the C26 tumour-bearing mouse model, we reveal muscle weakness precedes atrophy in quadriceps and diaphragm.…”

“…Preparation of Permeabilized Muscle Fibres . The assessment of mitochondrial bioenergetics was performed as described previously in our publications (17,19,32). Briefly, the quadriceps and diaphragm from the mouse was removed and placed in BIOPS.…”

“…MiRO5 contained 20 mM Cr to saturate mitochondrial creatine kinase (mtCK) and promote phosphate shuttling through mtCK or was kept void of Cr to prevent the activation of mtCK (33) as described in Figure 5. For ADPstimulated respiratory kinetics, our previously published procedures to stimulate complexes I and II-supported respiration were employed (17)(18)(19). 5 mM pyruvate and 2 mM malate were added as complex I-specific substrates (via generation of NADH to saturate electron entry into complex I) followed by a titration of sub-maximal ADP (25, 100 and 500 μM) and maximal ADP (up to 5000 μM in the presence of Cr or 30000 μM in the absence of Cr).…”

The Failed Clinical Story of Myostatin Inhibitors against Duchenne Muscular Dystrophy: Exploring the Biology behind the Battle

“…Mitochondrial dysfunction and metabolic stress are well characterised pathogenic features of dystrophin deficient muscles from mice ( mdx and D2 mdx ) and humans, as extensively documented by us [ 55 , 56 , 57 ] and others [ 98 , 99 , 100 , 101 , 102 , 103 ] (for a review, please see [ 54 ]). In DMD patients, and even in female carriers of the dystrophin gene mutation [ 104 , 105 ], muscle fatigue and exercise intolerance are reported.…”

GSK3 inhibition improves skeletal muscle function and whole-body metabolism in the severe DBA/2Jmdxmouse model

“…In 2016, Coley and colleagues 16 reported a worsened dystrophic phenotype in mdx mice that were backcrossed onto a DBA/2J (D2) strain compared with the C57 strain. With early onset muscle pathology and weakness [16][17][18] , the D2 mdx mouse has emerged as a viable preclinical model for DMD [17][18][19][20][21][22] . In this study, we first compared GSK3β content and activation status (Ser9 phosphorylation) in muscles from age-matched C57 and D2 mdx mice.…”