Transcript Effects of Glutamine Supplementation on Muscle

Effects of Glutamine Supplementation on Muscle Function
in a Mouse Model of Spinal Cord Injury
Abstract: Spinal cord injury (SCI) results in loss of muscle function due to the
rapid breakdown of muscle contractile proteins and high incidence of
inflammation that directly hinder rehabilitation. Glutamine is an amino acid that
plays a critical role in muscle integrity and in reducing inflammation, however,
impaired glutamine synthesis occurs under stressful conditions. Glutamine
supplementation can improve clinical outcomes from acute infection to sepsis,
but its effects on skeletal muscle function in the early stages after a SCI are
unknown. Based on glutamine’s benefits and clinical applicability these
experiments tested the hypothesis that glutamine treatment can preserve muscle
mass, strength, and fatigue resistance in a mouse model of SCI. Changes in
muscle mass, maximal isometric force, and fatigability will be measured 7 days
after sham or spinal cord transection (ST) surgery in mice receiving either
placebo or glutamine (n=3-5/group). ST significantly reduced gastrocnemius
mass independent of saline or glutamine treatment. Maximal isometric force
normalized to body or muscle mass was not different among groups. Fatigue
resistance was reduced with ST + saline, however, glutamine supplementation
prevented the loss of fatigue resistance (38±9 vs. 57±5% of max force,
respectively). Preliminary results suggest that 7 days after a SCI significant
reductions in muscle fatigue resistance can be reversed by glutamine
supplementation. Additional studies can continue to establish the protective
effects of glutamine on muscle endurance with SCI, underscoring the importance
of glutamine as a therapeutic intervention to accelerate the recovery of muscle
function after a SCI.
BACKGROUND AND HYPOTHESIS
 Spinal Cord Transection (ST) is a well-established
rodent model for studying the effects of spinal cord
injury.
 Glutamine supplementation can improve clinical
outcomes under stressful conditions (Novak et al.),
but its direct influence on skeletal muscle function
after a spinal cord injury are unknown.
 Glutamine was shown to prevent muscle force loss
following an acute inflammatory insult (Meador and
Huey)
 Skeletal muscle is the largest contributor to plasma
glutamine levels (Darmaun et al.),
therefore
providing an exogenous source of glutamine may
reduce the necessity for muscle protein breakdown
to maintain adequate levels of this essential amino
acid.
Compared to non-injured subjects, plasma
glutamine levels were reduced 54% in spinal cord
injury patients (Rogeri and Costa Rosa)
 Accelerated
recovery
from
glutamine
supplementation has been directly related to
increase in expression of protective heat shock
proteins (Wischmeyer et al.).
 Primary Hypothesis: These experiments will test
the hypothesis that glutamine supplementation can
attenuate losses of muscle force and endurance in
a mouse model of spinal cord injury.
Carissa Chamney, Ethan Garrigan, Kimberly Huey
Drake University, College of Pharmacy and Health Sciences
METHODS
Adult C57 mice were divided into 4 groups (n=35/group):
1) Placebo/Sham
2) Glutamine/Sham
3) Placebo/Spinal Cord Transection
4) Glutamine/Spinal Cord Transection
Complete spinal cord transection or sham surgery was
performed and followed by daily glutamine or placebo
(saline) supplementation for 7 days.
Glutamine groups received intraperitoneal injections of
1g/kg glutamine in saline suspension and placebo groups
received saline alone.
Maximal isometric plantar flexor force and fatigability
was measured at 7 days post-injury in anesthetized mice
with a dual-mode footplate system.
10 contractions were evoked every 5 seconds by
sciatic nerve stimulation
 Fatigue calculated as % maximum force after 10th
repetition
Figure 1. Dual mode
footplate
system
to
measure in vivo muscle
force production.
Isometric Force
Table 1. Initial and Final Body Weights (BW) in Sham and
Spinal Transected Mice Receiving Daily Saline or Glutamine
Initial BW (g)
Final BW (g)
Sham
Saline
Glutamine
24.3 ± 0.8
24.2 ± 0.6
24.3 ± 1.1
24.5 ± 0.4
Spinal Transection
Saline
Glutamine
22.7 ± 1.8
23.7 ± 1.4
20.0 ± 1.5
20.8 ± 0.8
Values are mean ± SE 3-5/group
Muscle Mass
Figure 3. Muscle force production
significantly reduced seven days aft
cord injury (SCI). Average maximal isom
relative to body weight in sham and
supplemented with glutamine or saline. M
n=3-5/group.
Fatigue Resistance
Figure 2. Muscle mass is decreased seven days after spinal
cord injury (SCI). Average right gastrocnemius mass (mg) for
sham and SCI groups supplemented with glutamine or saline.
Means ± SE, * significantly less than sham (p<0.05)
KEY FINDINGS
Glutamine prevented decreases in muscle fatigue resistance after spinal
cord injury.
Maximal isometric force production relative to body weight is not reduced
seven days following spinal cord injury.
Physiological Implications: These results help establish the effectiveness of
a safe, clinical intervention for humans in a mouse model of spinal cord
injury.
Simple dietary intervention with glutamine may help preserve muscle
integrity and endurance in spinal cord injury patients, thereby reducing early
loss of muscle function and accelerating recovery.
Future Studies: Quantify Hsp25 and Hsp70 protein expression in muscle
 Heat shock proteins protect muscle from numerous stressors including
inflammation, oxidative stress, and muscle wasting.
REFERENCES
 Darmaun D, Matthews DE, and Bier DM. Glutamine and
glutamate kinetics in humans. Am J Physiol 251: E117-126,
1986.
 Meador BM, and Huey KA. Glutamine preserves skeletal
muscle force during an inflammatory insult. Muscle Nerve 40:
1000-1007, 2009.
 Novak F, Heyland DK, Crit Care Med 30: 2022-2029, 2002.
 Rogeri PS, and Costa Rosa LF. Avenell A, Drover JW, and Su
X. Glutamine supplementation in serious illness: a systematic
review of the evidence. Plasma glutamine concentration in
spinal cord injured patients. Life Sci 77: 2351-2360, 2005.
 Tanhoffer RA, Yamazaki RK, Nunes EA, Pchevozniki AI,
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 Wischmeyer PE, Kahana M, Wolfson R, Ren H, Musch MM,
and Chang EB. Glutamine induces heat shock protein and
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2403-2410, 2001.
Figure 4. Glutamine prevents decre
muscle fatigue resistance after spinal co
(SCI). Fatigue calculated as % max force
repetition in sham and SCI mice suppleme
glutamine or saline. (n = 3-5/group, Me
*significant effect of glutamine (p<0.05)