Study of 4-hydroxybutyric acid produced after death

γ-羟丁酸（GHB）可以在血液中检测到，尿液，和死者的肝脏谁没有服用药物，而活着。为了阐明死后GHB的产生途径，比较了死后小鼠肝脏中GHB和β-羟丁酸（BHB）的产生量。GHB随时间的延长而显著升高，至死亡后7 d，GHB含量分别为<0.1μg/g、1.0 ±0.9 μg/g、4.6 ±0.7 μg/g和45.3±21.0 μg/g。BHB在死亡后第1天显著降低（第0天为2.3±1.3 μg/g，第1天为0.9 ±0.7 μg/g），随后至第7天略有增加（第3天为2.0±0.6 μg/g，第7天为5.4 ±1.8 μg/g）。这些结果表明，GHB的产生机制不同于死后BHB的产生机制。接着，检查了各种化合物的预处理对死亡后24小时小鼠体内肝脏中GHB和BHB浓度的影响。在体外小鼠肝脏中，发现柠檬酸最显著地增加GHB浓度（34.4±23.9 μg/g），并且额外的氨苄青霉素显著地抑制了约74%的增加。这一结果表明，伽马-羟丁酸可能来自柠檬酸，其水平随着死亡后细菌诱导的柠檬酸发酵而增加。另一方面，尽管在死亡后24小时没有化合物显著增加BHB浓度，但在死亡后0小时检测到高浓度的BHB（139.4±113.7 μg/g，对照）。这一结果支持了已知的理论，即当TCA循环因饥饿而被破坏时，肝脏中会合成酮酸，如BHB。本研究结果表明，柠檬酸发酵产生的柠檬酸可能是死后肝脏中产生GHB的主要前体，并且死后GHB的产生途径与BHB的产生途径明显不同。

γ-Hydroxybutyric acid(GHB) can be detected in the blood, urine, and liver of deceased persons who did not take the drug while alive. In order to clarify the pathway of GHB production after death, the amount of GHB produced in mouse liver after death was compared with that of β-hydroxybutyric acid(BHB). GHB significantly increased with time until 7 days after death (<0.1μg/g at day 0,1.0±0.9 μg/g at day 1,4.6±0.7 μg/g at day 3,and 45.3±21.0 μg/g at day 7). BHB significantly decreased at day 1 after death (2.3±1.3 μg/g at day 0,0.9±0.7 μg/g at day 1), and subsequently showed small increases until day 7(2.0±0.6 μg/g at day 3,5.4±1.8 μg/g at day 7). These results indicate that the mechanism of GHB production is different from that of BHB after death. Next, the effects of pretreatment of various chemical compounds on GHB and BHB concentrations in in vivo mouse liver at 24 h after death was examined. Citric acid was found to most significantly increase GHB concentrations (34.4±23.9 μg/g), and additional ampicillin significantly suppressed the increase by approximately 74% in in vitro mouse liver. This result indicates that GHB may arise from citric acid, with levels increasing with bacteria-induced citric acid fermentation after death. On the other hand, although no compounds significantly increased BHB concentrations at 24 h after death, high concentrations of BHB (139.4±113.7 μg/g, control) were detected at 0 h after death. This result supports a known theory that keto acids such as BHB are synthesized in the liver when the TCA cycle is disrupted due to starvation.The present results indicate that citric acid, which produced via citric acid fermentation, might be the main precursor of GHB produced in the liver after death, and the pathway of GHB production after death is clearly different from that of BHB.