Download Abnormalities in Magnesium (Mg2+) and ATP Levels in Muscle

Abnormalities
in Magnesium
(Mg*+ ) and ATP Levels in
Muscle Disorders:
Dermatomyositis
and Fibromyalgia
Depts.
J.H. Park, K.J. Niermann,
A. Das, B.N. Carr and N.J. Olsen
of Radiology and Medicine, Vanderbilt
Medical School, Nashville, TN,
Introduction
Magnesium
deficiency
is known to produce
neuromuscular
symptoms
of weakness,
fatigue,
and abnormal EMG (1). Magnesium is an important
metabolic
element
because it is required for all
enzyme
reactions
involving
ATP. This includes
enzymes in the glycolytic
and Krebs cycles, which
produce the ATP required for contraction.
Levels of
free and ATP-bound magnesium can be determined
in human muscle using P-31 MRS. We have shown
that patients with dermatomyositis
(DM), a disease
characterized
by a typical rash and severe muscle
weakness,
have decreased magnesium levels (2).
In this report, patients with fibromyalgia
(FM), a
disease with symptoms
of muscle pain, weakness,
specific tender points and sleep disorders,
were
compared to DM patients.
Observed decreases in
magnesium correlated with the degree of weakness
in these two patient groups.
Methods
P-31 MRS spectra of the quadricep muscles
of 12 fibromyalgia
and 6 dermatomyositis
patients,
and 12 controls were obtained using a 1.5 Tesla
magnet. Spectra were acquired during 6 min .of
rest. For exercise,
a weight equivalent
to 50%
maximum
voluntary
contractile
force (MVC) was
secured on the ankle, and the subject raised the
lower leg once every 5 set for 6 min. Levels of Pi,
PCr and ATP were determined
from the resonance
areas under the peaks (3).
Free and ATP-bound
Mg=+ levels were calculated
from the spectra
according to Gupta (41 and Mottet (5).
Results
In the rest period, there were no statistically
significant
differences
in [Mg free1 in the muscles
of patients
and controls.
With the stress
of
ABNORMALITIES
Controls
USA
exercise, levels of [Mg free1 decreased by 30% and
45%
for FM and DM patients,
respectively,
(P<O.O3 and 0.02) while the control values were
unchanged (See Table). The [MgATPl, which is the
enzmatically
active form of ATP, was 12% and
52% lower in FM and DM patients as compared to
normal values (P<O.Ol
and 0.0001).
For FM and
control muscles, 93% of total ATP was complexed
with Mg*+ compared to 85% in DM muscles. FM
patients have less weakness than DM subjects and
accordingly higher Mg *+ and ATP levels.
Conclusions
Since serum levels of Mg*+ correlate poorly
with tissue levels, it is important to determine the
cation levels in the muscles of myopathic patients.
factors in
Mg=+ and ATP levels may be important
the overall clinical status of FM and DM patients.
[Mg free] and [MgATPl levels for the patients were
significantly
below control values and correlated
with symptoms of loss of strength and endurance.
With DM patients,
prednisone
treatment
partially reversed the abnormalities
in Mg*+ levels
(2). This suggests
that Mg*+ may be generally
important
in the recovery
of myopathic
patients
since it is essential for generation and maintenance
of ATP in muscles.
In Summary,
low levels of [Mg free1 and
IMgATPl
correlate
with the severity
of muscle
weakness
in FM and DM. The MRS data indicate
a significant role for magnesium in the pathology of
these diseases.
References
1. Shils ME, Ann. Rev. Nutrition, 8:429, 1988.
2. Park JH, et al., ISMRM, 5:163. 1997.
3. Park JH, et al. Arthritis& Rheum. 37:736, 1994.
4. Gupta RK, et al. J.Biol.Chem. 253: 6172, 1978.
5. Mottet I, et al. J. MAGMA, 2:101, 1994.
IN Mg*+ AND ATP LEVELS (mmollkg
f SE)
(n = 12)
3.05
*FM = fibromyalgia;
DM = dermatomyositis
f
0.21