COMPARISON OF EXCITATORY AND INHIBITORY AMINO ACIDS PLASMA SPECTRUM IN PATIENTS WITH PRIMARY CEREBRAL ISCHEMIC STROKE DEPENDING ON THE POSTAPOPLECTIC SPASTICITY DEVELOPMENT IN THE RECOVERY PERIOD

Post-stroke spasticity is one of the most common post-stroke conditions that survivors face during their recovery. Spasticity can be painful and significantly impact a survivor’s life. The reasons of its phenomenon are not completely understood. We investigated plasma concentrations of the excitatory and inhibitory neuro amino acid’s during first 72 hours of the first-ever ischemic cerebral stroke survivors (45 patients) depending on the development of post-stroke spasticity in those patients on the 6th month after stroke onset. Plasma level of the same neuro amino acids in people with chronic cerebral ischemia served as a control. We have found that the joint characteristic for both groups of stroke survivors (those who developed spasticity and those who did not) was significantly increased level of excitatory neuro amino acids compared to control. In the group of patients without post-stroke spasticity an elevated excitatory neuro amino acid level was accompanied by an increased concentration of inhibitory neuromediators. But there was a distinguishing feature for stroke survivors with spastic limbs which was characterized by decreased or unchanged levels of inhibitory neuro amino acids. Thus, such result suggests that an insufficiency of inhibitory neuro amino acid system activation is some acute ischemic stroke patients who are subsequently prone to an emergence of post-stroke spasticity. This study needs further investigations in order to determine the metabolic or neuro-biochemical reasons of the observed difference between two groups of patients. Besides, we can use obtained results for creating the post-stroke spasticity predictive model for ischemic cerebral stroke survivors.


Ключевые слова: ПЕРВИЧНЫЙ ЦЕРЕБРАЛЬНЫЙ ИШЕМИЧЕСКИЙ ИНСУЛЬТ, ПОСЛЕИН-СУЛЬТНАЯ СПАСТИЧНОСТЬ, ВОЗБУЖДАЮЩИЕ И ТОРМОЗЯЩИЕ НЕЙРОАМИНОКИСЛОТЫ
During the last several years excitatory amino acids appear to be the subject of a great interest in neuroscience as a substance that play role in acute and deferred neuronal damage [1].
Біологія тварин, 2016, т. 18, № 2 We have discovered scarcity of information about plasma levels of neuro amino acids in patients with acute ischemic stroke, and these data are very controversial [7].Some scientists showed decreased plasma level of glutamate which they elucidate by compensatory increase of GABA (gamma-amino butyric acid) and accompanying inceased level of aspartate [2].Other authors have claimed about increased concentrations of glutamic acid and decreased levels of glycine and proline in acute stroke patients [3][4][5].Some other research has revealed permanent decreased plasma levels of glutamic acid and glycine in acute store survivors [6].Butter Th. et al. [6] discovered an increased plasma level of glutamate during the first 24 hours of acute ischemic stroke with subsequent gradual decrease.
Considering divergence of previously presented data regarding the levels of excitatory and inhibitory neuro amino acids in acute stroke survivors and absence the information about its concentration in patients according to development the spasticity subsequently, we found the aim of our study: to determine and to compare the plasma levels of neuro amino acids in stroke survivors during first 72 hours depending the existence of post-stroke spasticity on the 6 th month after cerebral ischemic stroke.

The methods
We examined 45 patients (21 women and 25 men) during 72 hours after the first-ever ischemic stroke and 11 patients (6 women and 5 men) with chronic cerebral ischemia who served as a control group.Mean age for patients was 60.13±0.92years (60.62±1.38 years for men and 59.58±1.21years for women).Mean age of people from control group was 60.23±1.82years.Diagnosis of acute ischemic stroke was confirmed using Computed Tomography.All patients were examined on the 6 th month after stroke using Modified Ashworth Scale (MAS) to determine whether or not they had developed spasticity, MAS≥1 was considered as a spastic muscle tone.We found increased muscle tone in 24 patients (53 %), 17 of them had spastic hemiparesis and 7 -focal spasticity only in the hand.We drew 5 ml of blood from patients who have been ad-mitted to the Lviv City Emergency Hospital, 1 st and 2 nd neurological departments, during first 72 hours after stroke onset.Plasma levels of excitatory (glutamate, aspartate, gtutamic acid, aspartic acid, tyrosine) and inhibitory (GABA, glycine, taurine) neuro amino acids were determined at the Institute of Animal Biology, Department of molecular biology and clinical biochemistry (Lviv) by automatic aminoacid analyzer LC 6001 Biotronic (Germany).
The data are presented as median, upper and lower quartiles Me [UQ; LQ].Nonparametric Mann-Whitney U test was used to define significant differences between the groups.P<0.05 was determined as a considerable level.We used Statistica 10.0 software for all analyses.

The results
After comparison of plasma levels of neuro amino acids we detected common feature for both groups (patients with spasticity and without it) was significantly increase in glutamate (P<0.01) and aspartate (P<0.01)concentrations in relation to the control group.Furthermore, in acute period of stroke, patients who suffered from spasticity on the 6 th month, in comparison with those who did not, had higher levels of previously mentioned aminoacids: glutamate concentration exceed 32 % and aspartate -33 %.Conjoint characteristic for both groups also was significant decrease in tyrosine's level (P<0.01) in relation to control group.Distinquinshing feature of patients from the group with post-stroke spasticity was much higher level of glutamine and unlike patients with normal muscle tone it was significantly different from the control group (P<0.01).An interesting distinction was found in a group of patients without spasticity who had higher plasma concentration of asparagine that was significantly different from the control group (P<0.05).
It should be noted that in the acute phase of the first-ever ischemic stroke between patients who suffered from spasticity on the 6 th month and those who did not was divergence also between inhibitory amino acid levels.Hence, GABA concentration in plasma of patients without poststroke spasticity was 2.9 times higher comparing to the control group (P<0.01),while in the group without spasticity it exceeded control's group level only in 1.3 times, which had no statistical significance (P>0.05).An interesting finding was difference in glycine concentration between groups.So, glycine level was observed to be 49 % higher in group with spasticity comparing to the control group (P>0.05),but in patients without spasticity it's concentration decreased and was significantly lower comparing to the control group (P<0.01).During the first 72 hours of acute ischemia stroke taurine's concentration was observed to be significantly lower comparing to the control level in both groups of patients (P<0.05).
Thus, analysis of the obtained data showed activation of the excitatory amino acid system in both groups of patients (those who have developed a post-stroke spasticity untill the 6 th month after stroke onset and those who have not) and accompanying decrease in inhibitory amino acid's sytem in group of patients who have got spastic increase of the muscle tone.In patients who did not show increased muscle tone we observed an increase in both inhibitory aminoacid's levels in response to an excessive amount of excitatory neuro amino acids.Taking into consideration our findings and biochemical features of GABAshunt (Fig. 1) [8] we can presume the existence of some compensatory mechanisms of biotransformation of excess glutamate into GABA in some group of patients and somehow this mechanism protects them from post-stroke spasticity.Thus, if we calculate the ratio glutamate/GABA we have got 30.0 [21.9; 34.1] in control group, and 74.5 [55.7; 102.7], 17. 1 [14.7; 19.9] in group of patients with spasticity and without, respectively.

Conclusions
The found insufficiency of inhibitory amino acid system in acute phase of ischemic stroke in some group of patients, who are prone to post-stroke spasticity subsequently, can be used for screening such patients for their early rehabilitation.This study needs more attention in order to find possibility for pharmaceutical correction of the poor inhibitory amino acid pool.
Perspectives for further research.Further investigations need to be done in order to determine the metabolic or neuro-biochemical reasons of the observed difference between two groups of patients.Besides, we can use study results for creating the post-stroke spasticity predictive model for ischemic cerebral stroke survivors.