Tessari P, Inchiostro S, Barazzoni R, Zanetti M, Orlando R, Biolo G, Sergi G, Pino A, Tiengo A
Department of Metabolic Diseases, University of Padua, Italy.
Am J Physiol. 1994 Jul;267(1 Pt 1):E140-9. doi: 10.1152/ajpendo.1994.267.1.E140.
To investigate body protein turnover and the pathogenesis of increased concentration of plasma phenylalanine in liver cirrhosis, we have studied phenylalanine and leucine kinetics in cirrhotic (diabetic and nondiabetic) patients, and in normal subjects, both in the postabsorptive state and during a mixed meal, using combined intravenous and oral isotope infusions. Postabsorptive phenylalanine concentration and whole body rate of appearance (Ra) were approximately 40% greater (P < 0.05) in patients than in controls. Leucine concentrations were comparable, but intracellular leucine Ra was also increased (P < 0.05), suggesting increased whole body protein breakdown. Postprandial phenylalanine Ra was also greater (P < 0.05) in the patients. This difference was due to a diminished fractional splanchnic uptake of the dietary phenylalanine (approximately 40% lower in the cirrhotics vs. controls, P < or = 0.05). Postprandial leucine Ra was also increased in the patients, but splanchnic uptake of dietary leucine was normal. Thus both increased body protein breakdown and decreased splanchnic extraction of dietary phenylalanine can account for the increased phenylalanine concentrations in liver cirrhosis.
为研究肝硬化患者体内蛋白质周转情况以及血浆苯丙氨酸浓度升高的发病机制，我们采用静脉和口服同位素联合输注的方法，对肝硬化患者（糖尿病性和非糖尿病性）以及正常受试者在空腹状态和进食混合餐期间的苯丙氨酸和亮氨酸动力学进行了研究。空腹状态下，患者的苯丙氨酸浓度和全身苯丙氨酸表现率（Ra）比对照组高约40%（P < 0.05）。亮氨酸浓度相当，但细胞内亮氨酸Ra也升高（P < 0.05），提示全身蛋白质分解增加。餐后患者的苯丙氨酸Ra也更高（P < 0.05）。这种差异是由于饮食中苯丙氨酸的内脏摄取分数降低（肝硬化患者比对照组低约40%，P ≤ 0.05）。患者餐后亮氨酸Ra也升高，但饮食中亮氨酸的内脏摄取正常。因此，全身蛋白质分解增加和饮食中苯丙氨酸内脏摄取减少均可解释肝硬化患者苯丙氨酸浓度升高的现象。
