A 1H nuclear magnetic resonance-based metabonomic approach for grading hepatic encephalopathy and monitoring the effects of therapeutic hypothermia in rats

Background: There are no good biomarkers for grading hepatic encephalopathy (HE) and monitoring the effectiveness of therapeutic measures. Methods: We applied (1)H nuclear magnetic resonance (NMR)-based metabonomics of brain samples obtained from acute liver failure rats sacrificed after ligation of the hepatic artery (at 6 h, precoma and coma stages), sham-operated controls and mild hypothermia (35 degrees C) for 6 or 15 h as a therapeutic measure. Results: Partial least square discriminant analysis established a classification model that scored the severity of encephalopathy. Animals treated with hypothermia did not develop manifestations of encephalopathy and were graded accordingly using the NMR-based metabonomic approach. Hypothermic animals showed lower levels of alanine and lactate as well as higher levels of N-acetylaspartate and myo-inositol compared with normothermic animals. The course of metabolic deterioration was more rapid in the brainstem than in the cortex. Conclusion: Metabonomic analysis is capable of grading HE, detecting regional differences and monitoring the protective effects of hypothermia. This approach elucidates differences of brain energetic metabolism and compensatory osmotic response to explain the effects of hypothermia.