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IntroductionSkeletal muscle fiber composition andwholesale nfl jerseys muscle energetics are not static and change in muscle disease. This study was performed to determine if a mitochondrial myopathy is associated with adjustments in skeletal muscle fiber type composition. 

Methods: Ten rats were treated with zidovudine2012 nfl jerseys an antiretroviral nucleoside reverse transcriptase inhibitor that induces a myopathy by interfering with mitochondrial functions.

Soleus muscles were examined after 21 weeks of treatment. Ten untreated rats served as controls. 

Results: Zidovudine induced a myopathy with mitochondrial DNA depletion, abnormalities in mitochondrial ultrastructure and reduced cytochrome c oxidase activity.

Mitochondrial DNA was disproportionally more diminished in type I compared to type II fibers, whereas atrophy predominated in type II fibers. Compared with controls, zidovudine exposed soleus muscles contained an increased proportion (256%) of type II fibers, whereas neonatal myosin heavy chains remained repressed, indicating fiber type transformation in the absence of regeneration.

Microarray gene expression analysis confirmed enhanced fast fiber isoforms, repressed slow fiber transcripts, and reduced neonatal fiber transcripts in the mitochondrial myopathy. Respiratory chain transcripts were diminished, while the enzymes of glycolysis and glycogenolysis were enhanced, indicating a metabolic adjustment from oxidative to glycolytic capacities.

There was a coordinated regulation of http://www.2012wholesalejerseysfoyou.comtranscription factors known to orchestrate type II fiber formation (upregulation of MyoD, Six1, Six2, Eya1, and Sox6; downregulation of myogenin and ERRgamma). 

Conclusions: The type I to type II fiber transformation in mitochondrial myopathy implicates mitochondrial function as a new regulator of skeletal muscle fiber type.

Author: Nils VenhoffDirk LebrechtDietmar PfeiferAna C VenhoffEmmanuel BisseJanbernd KirschnerUlrich A Walker
Credits/Source: Arthritis Research &Therapy 2012, 14:R233