Short-term electrical stimulation alters tongue muscle fibre type composition.
OBJECTIVE
To examine whether short-term exogenous activation of a tongue muscle induced a phenotypic shift from a fast to a slow fibre-type, and thus assess a potential therapeutic avenue to protect against obstructive sleep apnoea (OSA).


METHODS
New Zealand White rabbit genioglossus (GG) muscle, characteristically a fast muscle, was continuously stimulated at a frequency attributed to slow muscle (10Hz, 3V DC pulses) using an implanted micro-circuit for 7 days. Changes in muscle fibre types and aerobic capacity were assessed between stimulated and un-stimulated (control) groups using immunohistochemistry and electrophoresis for myosin heavy chain (MHC) and assayed for citrate synthase.


RESULTS
Compared to the un-stimulated control group, stimulated GG muscles had more (approximately 13%) type I MHC (slow-twitch) content; a proportional decrease in type II MHC (fast-twitch) isoform also occurred in the stimulated GG muscle (P<0.05). Electrophoresis analysis on whole muscle and single fibre MHC showed an increased type I expression in the stimulated GG muscle (P<0.01). A commensurate rise in citrate synthase activity, indicating a change in aerobic capacity, was also observed in the stimulated GG muscles.


CONCLUSIONS
Together, these results demonstrate a successful alteration in tongue muscle characteristics using exogenous electrical stimulation and perhaps a potential therapeutic application for OSA.
Pae
Eung-Kwon
EK
UCLA School of Dentistry, Los Angeles, CA 90095-1668, USA. epae@dent.ucla.edu
Hyatt
Jon-Philippe K
JP
Wu
Jennifer
J
Chien
Patricia
P
D000818:Animals; D002950:Citrate (si)-Synthase / Q000032:analysis; D004558:Electric Stimulation / Q000295:instrumentation; D004567:Electrodes, Implanted; D007150:Immunohistochemistry; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000648:ultrastructure; D018485:Muscle Fibers, Skeletal / Q000648:ultrastructure*; D018657:Muscle Fibers, Slow-Twitch / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000648:ultrastructure*; D018995:Myosin Heavy Chains / Q000032:analysis; D024461:Myosin Type I / Q000032:analysis; D024462:Myosin Type II / Q000032:analysis; D010101:Oxygen Consumption / Q000502:physiology; D010641:Phenotype; D020033:Protein Isoforms / Q000032:analysis; D011817:Rabbits; D024744:Skeletal Muscle Myosins / Q000032:analysis; D014059:Tongue / Q000648:ultrastructure*
D020033:Protein Isoforms; D002950:Citrate (si)-Synthase; D024461:Myosin Type I; D024462:Myosin Type II; D024744:Skeletal Muscle Myosins; D018995:Myosin Heavy Chains