Introduction
Multiple
sclerosis (MS) is a chronic inflammatory demyelinating disorder of the central
nervous system affecting white and possibly grey matter. MS is characterized by
multiple focal demyelinating lesions affecting the white matter, which is not
infrequently associated with cortical demyelination and which may be preceded
by destruction of oligodendrocytes and apoptosis1,2. Mitochondrial
DNA alterations, abnormal mitochondrial enzyme activities, mitochondrial DNA
repair defects and increased production of free radicals have been reported to
increase in MS patients and animal models3. Impaired mitochondrial
can promote neurodegeneration and cause increased anaerobic metabolism in MS4.
Measurement of serum lactate in MS patients might be relatively an inexpensive
test for monitoring of the assumed hypoxia in MS4. There is an increasing number
of reports on anti-oxidant substances such as uric acid (UA) in MS, in order to
identify reliable disease activity and disability progression markers5-8.
Several studies had showed decreased UA levels serum
in MS
patients, and possible relationships between level of UA and disease outcomes, with
lower levels of UA in patients presenting with higher disease activity, higher
relapse rate and disability scores [5,9-11]. The aim
of our study was to determine whether MS patients had values of circulating
lactate and uric acid different from those of controls and their potential role
as biomarkers for monitoring disease activity and progression.
Subjects and Method
Subjects
This case-control study
was conducted on 89 Egyptian subjects (55 multiple sclerosis patients (patients
group = group I) and 34 normal healthy control (control group = group II)
Inclusion criteria:
We included patients
with multiple sclerosis (RRMS and SPMS) (according to the revised McDonald's
criteria) 12 from both sexes whose age ranged 10-50 years.
Exclusion criteria:
We had excluded patients
with any other medical conditions that may affect the serum lactate level (such
as diabetes mellitus, severe iron-deficiency anemia, liver disease, alcoholic
ketoacidosis, pancreatitis,
malignancy, infection, renal failure and seizures) or the serum UA level (such
as gout and hypertensive patients on diuretics).
Patients in the study
group were recruited from the Multiple Sclerosis Unit, Kasr Al-Aini
Hospitals, and Cairo University
over the period from October 2014 until January 2015.
Methods
All patients in group
(I) were subjected to:
1.
Clinical assessment:
Full history taking, general medical examination and
thorough neurological examination according to the modified multiple sclerosis
sheet officially used in MS unit, Neurology Department, Cairo University.
2.
Expanded disability status scale (EDSS)13:
The degree of disability for all patients was rated
according to the EDSS, that provides overall rating of disabilities based on a
(0) (normal neurological examination) to (10) death due to MS.
All participants in both groups were subjected to:
1. Measurement of
serum lactate and uric acid:
a. Collection of serum and
plasma samples:
5 ml of blood was collected and divided
into two tubes: one containing sodium fluoride-potassium oxalate for plasma
separation and the other one was a plain tube, in which the sample was allowed
to clot for serum separation.
b. Biochemical testing:
Plasma lactate was assayed according to
Trinder method14. All assays were carried out with Bechman Coulter
AU480 autoanalyzer (USA).
Serum uric acid was determined according to the modified Trinder method described
by Fossati et al.15,16.
2. Statistical analysis:
Data were statistically described in terms
of mean ±
standard deviation (± SD) and compared using Student t test for
independent samples. Correlation between various variables was done using
Pearson moment correlation equation for linear relation in normally distributed
variables and Spearman rank correlation equation for non-normal
variables/non-linear monotonic relation. p values less than 0.05 was considered
statistically significant. All statistical calculations were done using
computer program SPSS (Statistical Package for the Social Science; SPSS Inc., Chicago, IL,
USA) release 15
for Microsoft Windows (2006).
ResultS
Characteristics of the study population:
This study included 55
patients with MS and 34 age and sex-matched healthy controls. The mean age of
the patients group was 33.37 ±9.13 while it was
32.6 ±8.31 years in the control group. In the patients group, the
frequency of females and males was 61.8% (n= 34) and 38.2% (n= 21) respectively,
while in the control group, there were 21 females (61.8%) and 13 males (38.2%).
The mean duration of the disease in patients was 6.1±5.07 years. The mean
duration since the last attack was 16.41±18.1 months. The mean of the total
number of the attacks was 4.07±2.7. The mean number of attacks over the past
two years was 1.45±1.2. The mean EDSS
score was 3.83±2.01. The most frequent MS type was relapsing remitting MS (46
patients =83.6%), followed by the secondary progressive MS (8 patients =14.5%)
and lastly the primary progressive MS in only one patient (1.9%).
Results of the serum lactate and uric acid:
As shown in Table (1),
The mean serum lactate level in the patients group was 15.88±6.42 mg/ dl, while in the control group, it was
12.09(4.08). This difference was highly statistically significant (p=0.005).
Table (2) Shows that serum uric acid level in the patients group was lower than
that in the control group as the mean serum UA was 4.35±1.36 and 5.62±1.87
respectively. This difference was also highly statistically significant
(p=0.001).
Correlation between serum levels of lactate, uric acid and
clinical variables:
Table (3) presents the correlations
between serum levels of lactate and uric acid in the patients group and the
clinical variants like age of patients, the duration of the illness, the
duration since the last attack, the number of attacks and the EDSS score. There
was no significant correlation between the levels of serum lactate, uric acid
and different clinical parameters apart from the statistically significant
positive correlation between age and serum level of uric acid (r=0.306, p=0.029).
Table 1. Serum lactate levels in MS patients and controls.
|
Patients
group
(n=55)
|
Control
group
(n=34)
|
P-value
|
Minimum (mg/dl)
|
5.3
|
6.5
|
|
Maximum (mg/dl)
|
36
|
21
|
|
Mean ±SD (mg/dl)
|
15.88(6.42)
|
12.09(4.08)
|
0.005*
|
*Significant at P<0.01
Table 2. Serum uric acid levels in MS patients and controls.
|
Patients
group
(n=55)
|
Control
group
(n=34)
|
P-value
|
Minimum(mg/dl)
|
2
|
2.9
|
|
Maximum(mg/dl)
|
9.6
|
9.6
|
|
Mean ±SD (mg/dl)
|
4.35(1.36)
|
5.62(1.87)
|
0.001**
|
*Significant at P<0.01
Table 3. Correlation between serum lactate, uric acid and
clinical variables.
|
Serum lactate level
Mean
(SD)
Mg/dl
|
Serum uric acid level
Mean
(SD)
Mg/dl
|
Age
|
r
|
0.047
|
0.306
|
P. value
|
0.764
|
0.029*
|
Duration of illness
|
r
|
-0.161
|
-0.036
|
P. value
|
0.307
|
0.807
|
Duration since the last
attack
|
r
|
0.177
|
-0.067
|
P. value
|
0.256
|
0.640
|
Number of attacks
|
r
|
-0.093
|
-0.246
|
P. value
|
0.554
|
0.082
|
EDSS score
|
r
|
-0.194
|
0.181
|
P. value
|
0.213
|
0.203
|
*Significant at P<0.05
Discussion
The present study
demonstrated the increased serum levels of lactate in the Egyptian MS patients
as compared to controls. This finding may support the hypothesis that
mitochondrial dysfunction has a crucial role in the pathogenesis of MS and of
its particular relevance to the neurodegenerative component of the illness.
These findings are supported
by the results of a recent multicenter study that has been published in 2014 in
which 613 MS patients were recruited, assessed for the clinical disability and
serum lactate level. They found that
levels of serum lactate in patients with MS was three times higher than that of
healthy controls group along with higher levels in cases with a progressive
than with a relapsing-remitting disease course. However, in contrast to our
results, that did not find a significant correlation between lactate and clinical
disability, they found a linear correlation between serum lactate levels and
the expanded disability scale (EDSS) 4. There is paucity of reports
as regard the role of lactate as a potential biomarker for the disease
progression and activity; therefore, further studies should be encouraged for
better exploration of the importance of lactate serum levels and of its
variations in relation to the course of the disease and disability progression.
The present study
demonstrated also statistically significant reduced serum levels of UA in the
Egyptian MS patients as compared to healthy controls. This finding suggests the
reduction of antioxidant reserves during the course of MS. Our results are
supported by Fereshteh et al., who found a significant difference between mean
UA concentration in patients with relapsing MS and controls (p = 0.002)17.
Moreover, In 2012, a multicenter study The serum UA levels were lower in
patients with MS than in healthy controls Similarly, the serum UA levels
decreased in MS patients with clinical activity when compared to MS with
clinical inactivity patients with relapse in comparison to RRMS patients with
remission10. This finding is also matching with many other studies
that reported the significantly lower serum level of UA in MS patients9-11.
Our results did not find
a significant correlation between the serum uric acid levels and the disease duration,
number of the attacks and EDDS scores.
These negative results
are supported by the results of Liu et al who
suggested that serum UA levels did not correlate with higher (or lower)
expanded disability status scale and magnetic resonance imaging (MRI) activity10.
However, in contrast to our data, a cross-sectional study, found an inverse relationship
between UA levels and disease duration18.
Our study suggests that
both serum lactate and UA are relevant to MS. Their potential use as biomarkers
for monitoring disease activity and progression is doubtful.
[Disclosure: Authors report no conflict
of interest]
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الملخص العربي
اللبنات وحامض البوليك بالدم كمؤشرين حيويين
لنشاط وتقدم مرض التصلب المتعدد
يعد مرض
التصلب المتعدد من الأمراض التي شاعت مؤخرا وهو ينشأ نتيجة خلل بالجهاز المناعي
يؤدي إلي التهاب الغلاف الدهني لأعصاب الجهاز العصبي المركزي.ولمرض التصلب المتعدد
أعراض كثيرة مثل: اختلال الجهاز الحركي أو الجهاز الحسي. يهدف هذا البحث إلى دراسة مستوي اللبنات وحامض البوليك بالدم كمؤشرين
حيويين لنشاط وتقدم مرض التصلب المتعدد وماذا إذا كان يختلف عن مستوياتهما في الأصحاء.
أُجريت
الدراسة على 55 مريضا مصريا مصابين بالتصلب المتعدد حسب مواصفات ماكدونالد للتصلب
المتعدد لعام 2010. وقد تم اختيار العينة من وحدة التصلب المتعدد – مستشفي قصر
العيني – جامعه القاهرة طبقا للمواصفات التالية:
1-
العمر يتراوح من 10-50 سنه من كلا الجنسين.
2-
تم استبعاد المرضى الذين يعانون من أي مرض آخر
يؤثر على مستوي اللبنات وحامض البوليك بالدم
وتم
اختيار 34 متطوعا من الأصحاء كمجموعه ضابطه.
وقد خضع المرضى للفحوص والاختبارات التالية:
1-
فحص إكلينيكي وعصبي.
2-
مقياس كيرتزك لقياس الإعاقة الجسدية.
وخضع جميع المشاركين بالخث من المرضي والأصحاء لدراسة
معمليه لمستوي اللبنات وحامض البوليك بالدم.
وكانت نتائج البحث كما يلي:
1- وجود زيادة
ذات دلاله احصائيه عالية في مستوي اللبنات بالدم في مجموعه الدراسة مقارنه بالمجموعة
الضابطة
2- وجود
نقص ذو دلاله احصائيه في مستوي حامض البوليك بالدم في مجموعه الدراسة مقارنه بالمجموعة
الضابطة
3- عدم
وجود علاقة طرديه ذات دلاله احصائيه بين مستوي اللبنات بالدم ومدة المرض، عدد الانتكاسات،
الفترة منذ أخر انتكاسه، درجه الاعاقه حسب مقياس كيرتزك لقياس الإعاقة الجسدية.
4- عدم
وجود علاقة عكسية ذات دلاله احصائيه بين مستوي حامض البوليك بالدم ومدة المرض، عدد
الانتكاسات، الفترة منذ أخر انتكاسه، درجه الاعاقه حسب مقياس كيرتزك لقياس الإعاقة
الجسدية.
ويستنتج
من هذا أن مستوي اللبنات وحامض البوليك بالدم مرتبط بمرض التصلب المتعدد ولكن
استخدامهما كمؤشرين حيويين للاستدلال على مدي تقدم المرض ودرجه شده الاعاقه يحتاج إلى
المزيد من البحث.