Ischemic stroke continues to be a serious public health problem worldwide, with a poor prognosis once it occurs. Fast diagnosis and appropriate treatment are of utmost significance to improving the outcome in patients with acute ischemic stroke or convalescent patients with ischemic stroke. Therefore, it is particularly important to investigate the metabolism and find some indicators that can evaluate the prognosis of stroke patients for the optimized care and treatment(Ormstad, Verkerk, & Sandvik, 2016; X. Wang et al., 2020). Many studies have reported amino acid metabolism in acute ischemic stroke. In this study, we compared the amino acid profiles of convalescent patients with ischemic stroke with healthy subjects by HPLC, aiming to find the metabolic differences and prognostic markers between two groups. 24 amino acids were identified in our study, the levels of P-Ser, Glu, Ile, Leu, Phe, Arg, Pro in stroke patients increased significantly, and the levels of Tau, Cys, Met, b-Ala, His lowered in patients compared to controls, which indicated that most amino acids had high diagnostic efficiency in convalescent patients with ischemic stroke and healthy controls. Ile and Leu were reduced in acute ischemic stroke(Kimberly, Wang, Pham, Furie, & Gerszten, 2013), but we observed that they were increased in convalescent patients in our study, which was consistent to reported research(Goulart et al., 2019). Glutamate, as a nerve excitatory amino acid, is an indicator of neural excitation and neurotoxin, and is found to be highly increased in stroke patients as studies demonstrated(Gomi et al., 2000; Meng et al., 2015). These amino acid metabolic differences between convalescent patients and healthy controls could be used as diagnostic markers in two groups. Given the complexity of neurobiological mechanisms of ischemic stroke, it might need a combination, rather than a single metabolite using as the diagnostic marker(D. Wang, Kong, Wu, Wang, & Lai, 2017). So, further studies are needed.
Although advances in medicine have greatly improved the treatment of patients with ischemic stroke in recent years, there is still a high recurrence rate. Therefore, it is particularly important to find indicators that can judge the prognosis of patients. Amino acids are important nutrients in human body, the levels of free amino acids in serum could partially reflect the status of metabolic disorders, which may help to evaluate the status of patients(Xie & Li, 2015). The stroke patients exhibited significantly higher Glu and lower Tau and Tau/Glu than the healthy controls in our study. Glu is the main excitatory neurotransmitter in the central nervous system, impaired uptake or excessive release of Glu lead to the extracellular concentration rising sharply in ischemic stroke patients, and ultimately the excitotoxicity of Glu can induce neuronal death and brain damage(Meng et al., 2015; Y. Wang et al., 2013). Ahlem Zaghmi et al demonstrated that sustained blood glutamate scavenging could enhance the protection in ischemic stroke patients(Zaghmi et al., 2020). Taurine is widely involved in neurological activities leading to neuroprotection; the inhibitory amino acid taurine is a neuromodulator, which can resist the neurotoxic effects of glutamate and mitochondrial disorders, exerting neuroprotective actions in neural tissue(Ghandforoush-Sattari, Mashayekhi, Nemati, & Ayromlou, 2011; Morland, Pettersen, & Hassel, 2016; Sun, Gu, Zhao, & Xu, 2011). we monitored the trend of two amino acid changes continuously to for 5 weeks explore whether Glu, Tau or Tau/Glu can be used as prognosis biomarkers for stroke patients. According to our results, the value of Tau/Glu increased gradually with the prognosis getting better. The value of Tau/Glu in good prognosis group elevated significantly in the 5th week comparing to 1st week, however, the value of Tau/Glu in poor prognosis group didn’t have significant difference in the 5 weeks, and there was significant difference in the 5th week in good and poor prognosis group. The ROC curve comparing Tau/Glu between two sub-groups was analyzed, the AUC was 0.964, and the cut-off value was 0.79. Therefore, Tau/Glu level can be used as a potential prognosis marker and considering convalescent stroke patients have a good prognosis when the ratio > 0.79. Further studies are also needed to investigate the role of Tau/Glu in more patient groups as well.