术前禁食对机体和肝脏代谢的影响

The effect of perioperative fasting on the metabolism of liver and human body

目的探讨术前短期和长期禁食状态对机体和肝脏代谢的影响。方法建立实验兔的短期禁食动物模型,比较饱食和禁食状态下,血激素水平、血生化指标和肝脏糖原含量的差异。进一步基于肝良性肿瘤患者和肝移植配型失败肝源的临床检查结果和肝糖原含量分析,比较术前短期和长期禁食对代谢的影响。结果在短期禁食动物模型中,过夜禁食后,兔血清中甲状腺素T4、皮质醇和多巴胺的水平增加约4倍,而肾上腺素水平降低约2.6倍,其余激素如胰高血糖素在禁食后略升高,而肾上腺素略有下降,血糖水平下降8.2倍,丙酮酸水平增加了15.6倍。而择期手术患者术后长期禁食比起术前短期禁食,血总胆固醇和总胆酸水平显著降低。兔肝和人肝样本均表现为禁食后肝糖原含量的显著下降。结论禁食是一种正常的生理状态,机体和肝脏的代谢改变源于体内和肝脏内大量代谢相关转录因子、酶表达水平和活性的改变。因此在临床工作和科研实践中应充分考虑并排除禁食对化验指标和基因表达的影响。

Objective To investigate the effect of short-term and long-term fasting on the metabolic characteristics of liver and whole body. Methods A fasting animal model was established, and the hormone levels, as well as biochemical parameters in blood were compared under both fed and fasting conditions. Meanwhile, the liver glycogen of the animal model was analyzed using periodic acid leucofuchsin method（PAS） staining. In addition, to further verify the physiological metabolic characteristics in human,the changes of some available clinical examination indexes, such as blood glucose, total cholesterol and bile acid levels and normal liver tissues from both the donors who had satiation feeding and the patients with liver benign neoplasms undergoingperioperative fasting, were analyzed. Results In our animal model, after overnight fasting, blood glucagons was slightly increased; thyroid hormones, dopamine and cortisol significantly roused, whereas epinephrine was substantially declined. In response to the alterations of hormone levels, metabolic pathways in the body also changed including the levels of glucose was decreased, whereas pyruvic acid was strongly increased. For patients undergoing elective surgery, the post-operative long-term fasting significantly lowered the total cholesterol and bile acid levels compared with pre-operative overnight fasting. Furthermore, the liver glycogen of animal models and normal liver donors was almost disappeared at the fasting condition. Conclusions Fasting is a kind of normal physiological condition. The metabolic alternations reflect the changes of expression and activity of thousands of genes in liver and the other organs, such as transcription factors and metabolism-related enzymes. Therefore, the effect of fasting must be fully considered and excluded when we performed clinical and research studies.