title: Hyperhomocysteinemia associated skeletal muscle weakness involves mitochondrial dysfunction and epigenetic modifications.
abstract: HHcy has been implicated in elderly frailty, but the underlying mechanisms are poorly understood. Using C57 and CBS+/- mice and C2C12 cell line, we investigated mechanisms behind HHcy induced skeletal muscle weakness and fatigability. Possible alterations in metabolic capacity (levels of LDH, CS, MM-CK and COX-IV), in structural proteins (levels of dystrophin) and in mitochondrial function (ATP production) were examined. An exercise regimen was employed to reverse HHcy induced changes. CBS+/- mice exhibited more fatigability, and generated less contraction force. No significant changes in muscle morphology were observed. However, there is a corresponding reduction in large muscle fiber number in CBS+/- mice. Excess fatigability was not due to changes in key enzymes involved in metabolism, but was due to reduced ATP levels. A marginal reduction in dystrophin levels along with a decrease in mitochondrial transcription factor A (mtTFA) were observed. There was also an increase in the mir-31, and mir-494 quantities that were implicated in dystrophin and mtTFA regulation respectively. The molecular changes elevated during HHcy, with the exception of dystrophin levels, were reversed after exercise. In addition, the amount of NRF-1, one of the transcriptional regulators of mtTFA, was significantly decreased. Furthermore, there was enhancement in mir-494 levels and a concomitant decline in mtTFA protein quantity in homocysteine treated cells. These changes in C2C12 cells were also accompanied by an increase in DNMT3a and DNMT3b proteins and global DNA methylation levels. Together, these results suggest that HHcy plays a causal role in enhanced fatigability through mitochondrial dysfunction which involves epigenetic changes.
authors.affiliation: Department of Physiology & Biophysics, University of Louisville, Louisville, KY 40202, USA. Electronic address: s0veer02@louisville.edu.
authors.forename: Sudhakar
authors.initials: S
authors.lastname: Veeranki
authors.affiliation: Department of Physiology & Biophysics, University of Louisville, Louisville, KY 40202, USA.
authors.forename: Lee J
authors.initials: LJ
authors.lastname: Winchester
authors.affiliation: Department of Physiology & Biophysics, University of Louisville, Louisville, KY 40202, USA.
authors.forename: Suresh C
authors.initials: SC
authors.lastname: Tyagi
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D052283:Creatine Kinase, MM Form / Q000235:genetics; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism; D019175:DNA Methylation; D000090205:DNA Methyltransferase 3A; D004268:DNA-Binding Proteins / Q000378:metabolism; D044127:Epigenesis, Genetic; D005260:Female; D015870:Gene Expression; D020138:Hyperhomocysteinemia / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D035683:MicroRNAs / Q000235:genetics; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D009119:Muscle Contraction / Q000235:genetics / Q000502:physiology; D018908:Muscle Weakness / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D051266:Nuclear Respiratory Factor 1 / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013550:Swimming; D014157:Transcription Factors / Q000378:metabolism; D000097584:DNA Methyltransferase 3B
chemical_list: D000255:Adenosine Triphosphate; D052283:Creatine Kinase, MM Form; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D004268:DNA-Binding Proteins; D035683:MicroRNAs; D024101:Mitochondrial Proteins; D051266:Nuclear Respiratory Factor 1; D014157:Transcription Factors; D000097584:DNA Methyltransferase 3B; C000715535:Dnmt3a protein, mouse; C550178:Mirn494 microRNA, mouse; C422562:mitochondrial transcription factor A
keywords: Dystrophin; Epigenetics; Exercise; MicroRNA; NRF-1; mtTFA