Whole body leucine, phenylalanine, and tyrosine kinetics in end-stage liver disease before and after hepatic transplantation

High Correlation between Results of the [1-¹³C]-Phenylalanine Breath Test and Phenylalanine Hydroxylase (EC 1.14.16.1) Activity of the Liver in Rats

“…The dilution of administered [1- 13 C]-phenylalanine by endogenous plasma phenylalanine was examined by determining the concentration of plasma phenylalanine before administration of [1- 13 C]-phenylalanine. It has been reported that a higher level of plasma phenylalanine occurs in hepatic disorders [5, 6, 7], and similarly, the plasma phenylalanine concentration in some of the hepatitis rats was increased compared to control rats. There was, however, no significant difference between hepatitis rats and control rats.…”

“…In addition, we should consider the elevated level of plasma phenylalanine. As is well known, the concentration of plasma phenylalanine is increased in liver disease [5, 6, 7]. The dilution of [1- 13 C]-phenylalanine by the elevated level of plasma phenylalanine could be a direct reason for the decrease of 13 CO 2 in patients with end-stage liver disease.…”

Metabolic effects of liver transplantation in cirrhotic patients.

“…Shanbhogue et al studied amino acid kinetics before and after liver transplantation (2-3 d after surgery) and found no effect of liver transplantation on leucine flux and leucine clearance (24). Several studies investigated the amino acid kinetics in liver cirrhosis (the pretransplant condition), showing conflicting results (25): all found a normal basal rate of leucine flux (24,(26)(27)(28), with the exception of Tessari et al (29). In the present study, liver-transplanted patients had reduced basal leucine and BCAA, but normal phenylalanine and ␣-ketoisocaproic acid concentrations 5 mo after the transplant.…”

Nicht-Isotopen Tyrosin-Kinetik mit dem Dipeptid Alanyl-Tyrosin zur Beurteilung der Organfunktion bei Lebertransplantation – eine Pilotstudie

“…Although hepatic elimination of tyrosine is not the only factor determining its plasma levels, it has been shown that plasma clearance rates (i) accurately predict the function and reservoir of hepatocytes and (ii) correlate with outcome after hepatic surgery [5]. Liver transplantation is known to restore plasma tyrosine levels back to normal, depending on the viability of the graft [7][8][9]. This has led to the introduction of tyrosine kinetics as one of the most accurate assessments of liver function; however, the test has failed to find broad application in clinical practice because it is currently based on the use of isotopes, with the associated shortcomings of such tests, and is time consuming and expensive.…”