%0 Journal Article
%T The <i>phka</i>1 deficient I/LnJ mouse exhibits endurance  exercise deficiency with no compensatory changes in  glycolytic gene expression
%A Ashley M. Mefford
%A Claci C. Ayers
%A Naomi S. Rowland
%A Nancy A. Rice
%J Open Journal of Molecular and Integrative Physiology
%P 87-94
%@ 2162-2167
%D 2013
%I Scientific Research Publishing
%R 10.4236/ojmip.2013.32014
%X <b><span style=\"font-size:10.0pt;font-family:;\" \"=\"\">During
exercise, phosphorylase kinase (PhK) is the key regulatory enzyme responsible
for maintaining glycogenolytic flux to sustain muscle contraction. The absence
of PhK in skeletal muscle results in glycogen storage disease (GSD) Type IX
which is characterized by muscle weakness and rapid fatigue upon exercise. In this
study, we have used the <i>phka</i>1 deficient
I/LnJ mouse model of GSD to investigate the physiological and genetic
adaptations that occur in response to voluntary exercise. When quantified over
training periods of either 1, 2, or 5 weeks, I/LnJ mice ran significantly
less time/day and distance/day than agematched C57/Bl6 mice. Cumulatively
after five weeks, adult I/LnJ mice ran ~1/2 the total time and distance of
wild-type mice, 116 ¡À 6 hours and 211 ¡À23 kmversus 194 ¡À 3 hours and 418 ¡À4 km,
respectively. After 5 weeks, C57/Bl6 mice demonstrated an increase in
endurance as a result of aerobic training; this observed physiological
adaptation was not present in I/LnJ mice. The decrease in total distance run
by I/LnJ mice was not due to a reduction in speed; juvenile and adult I/LnJ
mice ran ~75% - 80% as fast as C57/Bl6 mice. When transcription of glycolytic
genes glucose transporter 4 (<i>scla</i>1),
pyruvate dehydrogenase (<i>pdha</i>1), and
phosphofructokinase (<i>pfk</i>) were
quantified at the end of each training period, no significant differences in
expression levels were found between mouse strains, suggesting that
non-glycolytic mechanisms work to maintain the muscle function observed in the
I/LnJ mice.</span></b>
%K Phosphorylase Kinase
%K Glycogen Storage Disease
%K Exercise
%K Skeletal Muscle
%K I/LnJ
%U http://www.scirp.org/journal/PaperInformation.aspx?PaperID=31932