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Advanced Stages of Duchenne Muscular Dystrophy Exhibit Mitochondrial Bioenergetic Impairments Linked Specifically to Creatine‐Dependent Energy Exchange
Author(s) -
Hughes Meghan C,
Ramos Sofhia V,
Turnbull Patrick C,
Perry Christopher G R
Publication year - 2019
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2019.33.1_supplement.868.14
Subject(s) - duchenne muscular dystrophy , phosphocreatine , creatine , medicine , endocrinology , chemistry , creatine kinase , ventricle , oxidative phosphorylation , mitochondrion , bioenergetics , diaphragm (acoustics) , biochemistry , energy metabolism , physics , acoustics , loudspeaker
Rationale Our recent findings demonstrate that left ventricle and diaphragm from 4 week old D2. mdx mice with Duchenne Muscular Dystrophy (DMD) exhibit impaired mitochondrial oxidative phosphorylation and elevated H 2 O 2 (mH 2 O 2 ) emission. The present investigation sought to determine the degree of these deficits in advanced stages of DMD. Methods ADP‐dependent mH 2 O 2 emission and respiration were assessed in permeabilized muscle fibre bundles from heart and diaphragm muscle of D2. mdx mice (52 weeks). Mitochondrial assessments were performed in the presence of 20mM creatine (+Cr) to maximally activate mitochondrial creatine kinase (mtCK)‐dependent shuttling of phosphate to the cytoplasm as phosphocreatine, which accelerates matrix ADP/ATP cycling, as well as in the absence of creatine (−Cr) to force mitochondria to rely solely on slower ATP/ADP diffusion. Results State II mH 2 O 2 emission (0 mM ADP, maximal mH 2 O 2 emission) was unchanged in DMD heart and lower in DMD diaphragm in both +Cr (96.0 pmol/sec/mg dry wt in DMD vs 498.0 pmol/sec/mg dry wt in WT, p<0.05) and –Cr (50.2 vs 312.9, p<0.05). 25 mM ADP was added to evaluate the ability of ADP to lower mH 2 O 2 emission (state III). ADP's ability to lower mH 2 O 2 emission was impaired in +Cr (heart: 69% of state II mH 2 O 2 in DMD vs 61% in WT, p=0.06; diaphragm: 75% vs 54%, p<0.05) but improved in −Cr in the heart (69% vs 98%, p<0.05), and unchanged in diaphragm. State III respiration was also evaluated using 25 mM ADP. +Cr, respiration was impaired in the heart (48.0 pmol/sec/mg wet wt in DMD vs 75.6 pmol/sec/mg wet wt in WT, p<0.05) and diaphragm (43.4 vs 47.8, p<0.05). −Cr, respiration was improved in DMD heart (60.0 vs 29.8 pmol/sec/mg wet wt, p<0.05) and unchanged in diaphragm. The greater mH 2 O 2 due to impaired mtCK did not alter heart glutathione in reduced or oxidized forms, total glutathione or GSH/GSSG, but did increase diaphragm glutathione in oxidized, reduced and total forms (117–204%, p<0.001). Conclusion These findings demonstrate that mitochondrial dysfunctions during advanced stages in DMD are attributed specifically to an impaired ability of creatine to enhance ADP's control of respiration and mH 2 O 2 emission. A partial compensation in creatine‐independent control of ADP was observed which may prevent even further detriments to cellular energy and redox homeostasis. These findings suggest that restoration of normal mtCK activity and mitochondrial creatine‐dependent phosphate shuttling may be an effective approach at restoring mitochondrial bioenergetics and countering muscle‐specific weakness in DMD. Support or Funding Information NSERC Discovery Grant, The James H. Cummings Foundation, Canadian Foundation for Innovation, Ontario Research Fund This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .