Study of 4-hydroxybutyric acid produced after death

γ-羟丁酸(GHb)可在生前未服用该药物的死者的血液、尿液和肝脏中检测到。为了弄清小鼠死后GHB的产生途径，比较了小鼠死后肝脏中GHB的产生量与β-羟丁酸的产生量。死亡后第7天，GHb显著增加(第0天为0.1μg/g，第1天为1.0±0.9μg/g，第3天为4.6±0.7μg/g，第7天为45.3±21.0μg/g)。BHb在死亡后第1天显著下降(第0天为2.3±1.3μg/g，第1天为0.9±0.7μg/g)，至第7天略有上升(第3天为2.0±0.6μg/g，第7天为5.4±1.8μg/g)。这些结果表明，死后GHB的产生机制与BHB的不同。其次，研究了不同化合物的预处理对小鼠死后24小时体内肝脏中GHB和BHB浓度的影响。柠檬酸可显著增加体外小鼠肝脏中的羟丁酸浓度(34.4±2 3.9μg/g)，添加氨苄西林可显著抑制这一增加约74%。这一结果表明，GHB可能是由柠檬酸产生的，死亡后随着细菌诱导柠檬酸发酵水平的增加。另一方面，虽然在死亡后24小时没有任何化合物能显著增加BHb的浓度，但在死亡后0小时仍可检测到高浓度的BHb(139.4±113.7μg/g，对照)。这一结果支持了一种已知的理论，即当饥饿破坏TCA循环时，肝脏中会合成BHB等酮酸。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产生GHB的主要前体，死亡后GHB的产生途径与BHB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.