Thursday-Abstracts

Thursday, May 30, 2013
S230 Vol. 45 No. 5 Supplement
mineral content [BMC], bone mineral density [BMD], and BMD z-score [BMDz]) of
the lumbar spine, hip, and full body minus the head (body).
rEsuLTs: Bivariate correlations showed that SED was negatively associated with
hip BMDz (r=-0.557; p=0.016). LPA was positively associated with hip BMDz
(r=0.484; p=0.042). MPA had positive associations with hip BMD (r=.569, p=.014),
hip BMDz (r=.656, p=.003), and body BMDz (r=.636, p= .005). MVPA had positive
influences on hip BMDz (r= .589, p=.010), hip BMD (r=.566, p=.014), body BMC
(r=.509, p=.031), and body BMDz (r=.539, p=.021). VPA was positively associated
with spine BMC (r=.516; p=.034).
CONCLusIONs: These results show multiple positive associations between MVPA
and bone density in PWS youth. Interestingly, VPA was associated with only one bone
parameter, possibly due to the low amount of VPA in these PWS youth (~10 min).
The negative association between activities that are sedentary and hip BMDz supports
the notion that in addition to insufficient PA, excessive sitting can also negatively
influence BMD. Similar to other youth, PA of moderate plus vigorous intensity must be
encouraged and sedentary activities discouraged in this population despite the inherent
low stamina in PWS.
Supported by USAMRAA Award W81XWH-09-1-0682
C-34 Free Communication/Poster - Gene
Expression and Cell Signaling
May 30, 2013, 7:30 AM - 12:30 PM
Room: Hall C
1208 Board #153 May 30, 9:00 AM - 10:30 AM
Monocarboxylate Transporter-1 Expression at the Onset of
skeletal Muscle regeration
Dameon A. Smith, Tyrone A. Washington. University of Arkansas,
Fayetteville, AR. (Sponsor: Stavros Kavouras, FACSM)
(No relationships reported)
Skeletal muscle is extremely plastic and has the remarkable ability to recover from
injury. In diseases, such as muscular dystrophy, regeneration of skeletal muscle is
impaired. Monocarboxylate transporters, or MCTs, are involved with lactate transport
across the cell membrane. This transport has important implications for the energetic
efficiency of skeletal muscle. MCT expression is known to be affected by skeletal
muscle hypertrophy, chronic electrical stimuli, and voluntary wheel running. However,
the cellular regulation of MCT1 protein expression at the onset of skeletal muscle
regeneration has not been determined.
PurPOsE: To determine the protein and gene expression of MCT1 at the onset of
skeletal muscle regeneration.
METhOds: Twelve male C57/BL6 mice (12 weeks old) were randomly assigned to
either a control (uninjured) or bupivacaine (injured) group. Bupivacaine was injected
into the tibialis anterior (TA) of the injured group, and phosphate buffered saline (PBS)
was injected into the TA of the uninjured group. 3 days post-bupivacaine injection the
TA was extracted. MCT1 protein and gene expression were determined.
rEsuLTs: A 12% decrease in TA muscle mass to tibia length (2.43 ± 0.12 mg/mm vs.
2.14 ± 0.19 mg/mm, p < 0.02) was observed 3 days post-bupivacaine injection. IGF-1
gene expression increased 5.0-fold (p < 0.05) 3 days post-bupivacaine injection. MyoD
gene expression increased 3.5-fold (p < 0.05) 3 days post-bupivacaine injection. MCT-
1 gene expression was not altered 3 days post-bupivacaine injection. However, MCT-1
protein was decreased 32% (p < 0.03) 3 days post-bupivacaine injection.
CONCLusION: In conclusion, at the onset of skeletal muscle regeneration MCT1
protein is decreased and this appears to be regulated at the post-transcriptional level.
1209 Board #154 May 30, 9:00 AM - 10:30 AM
Oxidative stress results In Telomere shortening In Isolated
skeletal Muscle Fibers
Andrew T. Ludlow, Espen E. Spangenburg, Eva R. Chin,
Wen Hsing Cheng, Stephen M. Roth, FACSM. University of
Maryland, College Park, MD.
(No relationships reported)
We have recently provided evidence that long-term voluntary exercise in rodents
results in shorter skeletal muscle telomeres compared to young and age-matched
sedentary animals. The mechanism of telomere shortening induced by long-term
exercise is currently unknown. We hypothesized that reactive oxygen species induced
by muscle contractions could induce oxidative stress and damage telomeres resulting
in non-replicative based telomere shortening.
PurPOsE: The purpose of our investigation was to 1) Determine the response of
skeletal muscle telomeres to oxidative stress, and 2) Determine if basal telomere length
influences telomere dynamics in response to oxidative stress.
METhOds: Flexor digitorum brevis muscles were dissected from 15 male C57BL/6
(long telomere) and 20 male CAST/Ei (wild-derived, short telomere) mice and
dissociated into single fibers. Fibers were cultured in physiological oxygen (2-5%) for
MEDICINE & SCIENCE IN SPORTS & EXERCISE ®
5 days in the presence or absence of hydrogen peroxide (oxidant), or a combination
of N–acetylcysteine (antioxidant) and hydrogen peroxide. Telomere length, telomerase
activity, and protein content of telomere-repeat binding factors 1 and 2 (TRF1 and
TRF2; important for telomere protection) were determined.
rEsuLTs: In isolated skeletal muscle fibers of both mouse strains, oxidative stress
resulted in significant telomere shortening. Telomerase enzyme activity was not altered
by oxidative stress but was different between strains, with greater telomerase activity
in long-telomere C57BL/6 mice (p < 0.01). TRF1 protein content was increased in
CAST/Ei fibers that were exposed to the combination of hydrogen peroxide and N–
acetylcysteine. In hydrogen peroxide -treated C57BL/6 fibers TRF2 protein content
was increased compared to control fibers but this was attenuated in the presence of
N–acetylcysteine.
CONCLusIONs: Strain-specific telomere length dictates the response of telomere
protective proteins to oxidative stress, with long-telomere mice responding by
increasing expression of TRF2 and short telomere mice up-regulating expression of
TRF1. These data suggest a mechanism by which increased oxidative stress during
exercise induces shorter skeletal muscle telomere lengths.
FuNdING AG000268 and CA124334 A.T. Ludlow.
1210 Board #155 May 30, 9:00 AM - 10:30 AM
Mechanical Modulation Of The Mtor Pathway Is dependent
upon The Magnitude Of Cyclic Compressive Load
Emily H. Brownell, Sarah Abshire, Esther Dupont-Versteegden,
Timothy A. Butterfield. University of Kentucky, Lexington, KY.
(Sponsor: Thomas M. Best, FACSM)
(No relationships reported)
Massage is a therapeutic tool that has been used clinically to facilitate muscle recovery,
decrease soreness, and reduce muscle edema. The underlying mechanisms for its
beneficial effects are not well known, but one effect of massage that has been noted
sporadically and anecdotally in the literature is a potential to decrease atrophy. If
massage can attenuate the loss of muscle mass and associated muscle function, then
manual therapies may prove to be an effective a means to facilitate an earlier return to
normal function.
PurPOsE: To test the hypothesis that p70s6k phosphorylation will increase
following cyclic compressive loading (CCL, a massage-mimetic), and is dependent
upon the magnitude of applied load.
METhOds: Fifteen male Wistar Rats were divided into three groups, and the right
tibialis anterior muscle was subjected to one bout of 30 minutes massage-mimetic
loading. Group 1 (N=6) received CCL of 1.4 N, Group 2 received CCL of 4.5 N, and
Group 3 served as a pure control. Tissues were harvested six hours post CCL.
rEsuLTs: Following massage-mimetic loading, the mTOR pathway was
significantly upregulated compared to controls (p=0.042). Post-hoc analysis revealed
the upregulation of pp70s6k was significantly increased in the 4.5N load compared to
the control group (5.132au +/- 1.528 au compared to 2.898 au +/- 1.145 au., p=0.017).
There was also a trend for greater upregulation of the mTOR pathway following
massage with the 4.5N load compared to massage with the 1.4N load (5.132au +/-
1.528 au compared to 3.909 au +/- 0.511 au., p=0.088). Applied massage of 1.4N load
did not result in a difference in upregulation of pp70s6k when compared to the control
limbs (3.909 a.u +/- 0.511 a.u., compared to 2.898 +/- 1.145 a.u., p=0.2334), indicating
a load dependent response of the mTOR pathway.
CONCLusION: Applying a massage-mimetic to muscle tissue resulted in an increase
in phosphorylation of p70s6k (pp70s6k), a protein marker that directly induces protein
synthesis. Phosphorylation of p70s6k is notably increased in a load dependent manner,
and is significantly upregulated following CCL of 4.5 N in healthy rat muscle. This
indicates that massage may be an effective intervention to attenuate muscle atrophy
through upregulation of mTOR pathway and its downstream targets. Funded by an
NATA Osternig Research Award.
1211 Board #156 May 30, 9:00 AM - 10:30 AM
mTOr Pathway activation Following resistance Exercise
with Vibration in human subjects
Michael G. Leavitt, J. Brent Feland, David M. Thomson, Gary
W. Mack, FACSM, Daniel S. Nelson, Brenda Benson, Allen C.
Parcell, FACSM. Brigham Young University, Provo, UT.
(No relationships reported)
Functional adaptations in human skeletal muscle following a period of resistance
exercise are the result of regular activation of cellular signaling pathways that elevate
muscle protein synthesis. It has been reported that the addition of whole body vibration
(WBV) to a resistance exercise program enhances performance. Such improvements
in muscle function may be the result of increased activation of cellular signaling
pathways associated with muscle growth.
PurPOsE: We have investigated whether an acute bout of resistance exercise in
combination with WBV results in a greater activation of the mTOR signaling pathway
compared to resistance exercise alone.
METhOds: Eight untrained college-age males (23±2 yrs, 179±1 cm, 75±2.5 kg, and
12.6±1.8% body fat) performed unilateral leg press exercises with (Vbx) and without
(RT) vibration. Muscle samples were obtained from the vastus lateralis muscle pre-
ACSM May 28 - June 1, 2013 Indianapolis, Indiana