Reduced mitochondrial respiration and increased calcium deposits in the EDL muscle, but not in soleus, from 12-week-old dystrophic mdx mice

Rhayanna B Gaglianone,Tania Maria Ortiga-Carvalho,Thereza Quirico-Santos,Anderson Teixeira Santos,Claudia Mermelstein,Wagner Seixas Da Silva,Flavia Fonseca Bloise,Manoel Luis Costa

doi:10.1038/s41598-019-38609-4

Rhayanna B Gaglianone, Tania Maria Ortiga-Carvalho + Show 6 more

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https://doi.org/10.1038/s41598-019-38609-4

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Journal: Scientific Reports	Publication Date: Feb 13, 2019
Citations: 19	License type: open-access

Affiliation: Universidade Federal do Rio de Janeiro

Abstract

Mitochondria play an important role in providing ATP for muscle contraction. Muscle physiology is compromised in Duchenne muscular dystrophy (DMD) and several studies have shown the involvement of bioenergetics. In this work we investigated the mitochondrial physiology in fibers from fast-twitch muscle (EDL) and slow-twitch muscle (soleus) in the mdx mouse model for DMD and in control C57BL/10J mice. In our study, multiple mitochondrial respiratory parameters were investigated in permeabilized muscle fibers from 12-week-old animals, a critical age where muscle regeneration is observed in the mdx mouse. Using substrates of complex I and complex II from the electron transport chain, ADP and mitochondrial inhibitors, we found in the mdx EDL, but not in the mdx soleus, a reduction in coupled respiration suggesting that ATP synthesis is affected. In addition, the oxygen consumption after addition of complex II substrate is reduced in mdx EDL; the maximal consumption rate (measured in the presence of uncoupler) also seems to be reduced. Mitochondria are involved in calcium regulation and we observed, using alizarin stain, calcium deposits in mdx muscles but not in control muscles. Interestingly, more calcium deposits were found in mdx EDL than in mdx soleus. These data provide evidence that in 12-week-old mdx mice, calcium is accumulated and mitochondrial function is disturbed in the fast-twitch muscle EDL, but not in the slow-twitch muscle soleus.

Highlights

Duchenne muscular dystrophy (DMD) is a fatal muscular disorder caused by nonsense mutations, large deletions or duplications in the dystrophin gene
extensor digitorum longus (EDL) from mdx at 4 wks showed ~1% increase compared to EDL from control at 4 wks, and soleus at 4 and 12 wks showed ~1% and ~6% increase, respectively, compared to soleus controls (Fig. 1)
Wada and colleagues (2014) described ~5% increase in calcium deposits in tibialis anterior muscle from mdx[20]. These results show that a high accumulation of calcium deposits may be specific to EDL from mdx at 12 wks

Summary

Introduction

Duchenne muscular dystrophy (DMD) is a fatal muscular disorder caused by nonsense mutations, large deletions or duplications in the dystrophin gene. The mdx mouse with defective dystrophin expression is one of the most widely used animal models for DMD research These animals present a mild phenotype and a less severe disease course compared to humans, which is most likely due to the high regenerative capacity of mouse muscles[3,4,5]. The studies often used a pool of different muscle samples to analyze mitochondrial physiology[14]. It is important to assess mitochondrial respiration in skeletal muscles with distinct fiber-type specialization in mdx mice at 12 wks. To address this point, we used permeabilized fibers from fast-twitch extensor digitorum longus (EDL), and slow-twitch soleus from mdx mice at 12 wks. We analyzed the presence of calcium deposits in these muscles (EDL and soleus) in an effort to correlate the deposits with alterations in mitochondrial function

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