Protein tolerance to standard and high protein meals in patients with liver cirrhosis

Abstract

Aim: To investigate the plasma amino acid response and tolerance to normal or high protein meals in patients with cirrhosis.

Methods: The plasma amino acid response to a 20 g mixed protein meal was compared in 8 biopsy-proven compensated cirrhotic patients and 6 healthy subjects. In addition the response to a high protein meal (1 g/kg body weight) was studied in 6 decompensated biopsy-proven cirrhotics in order to evaluate their protein tolerance and the likelihood of developing hepatic encephalopathy (HE) following a porto-caval shunt procedure. To test for covert HE, the "number connection test" (NCT) was done on all patients, and an electroencephalogram was recorded in patients considered to be at Child-Pugh C stage.

Results: The changes in plasma amino acids after a 20 g protein meal were similar in healthy subjects and in cirrhotics except for a significantly greater increase (P < 0.05) in isoleucine, leucine and tyrosine concentrations in the cirrhotics. The baseline branched chain amino acids/aromatic amino acids (BCAA/AAA) ratio was higher in the healthy persons and remained stable-but it decreased significantly after the meal in the cirrhotic group. After the high protein meal there was a marked increase in the levels of most amino acids, but only small changes occurred in the levels of taurine, citrulline, cysteine and histidine.The BCAA/AAA ratio was significantly higher 180 and 240 min after the meal. Slightly elevated basal plasma ammonia levels showed no particular pattern. Overt HE was not observed in any patients.

Conclusion: Patients with stable liver disease tolerate natural mixed meals with a standard protein content. The response to a high protein meal in decompensated cirrhotics suggests accumulation of some amino acids but it did not precipitate HE. These results support current nutritional guidelines that recommend a protein intake of 1.2-1.5 g/kg body weight/day for patients with cirrhosis.

Keywords: Amino acids; Branched chain amino acids; Cirrhosis; Diet; Fischer’s ratio; Liver; Nutrition; Protein; Tolerance.

Figure 1

Plasma alpha-amino nitrogen concentration in response to a 20 g protein meal. Cirrhotic patients (n = 6), (closed circles); healthy subjects (n = 6), (asterix) (mean ± SEM).

Figure 2

Plasma leucine (A), isoleucine (B) and valine (C) concentrations in response to protein meals. Twenty grams protein meal, cirrhotics (n = 8), (closed circles); 20 g protein meal, healthy subjects (n = 6), (asterix) (mean ± SEM); 1 g/kg body weight protein meal, cirrhotics (n = 6), (open squares).

Figure 3

Plasma ammonia concentrations in cirrhotic patients. Blood ammonia after a 20-g protein meal. Cirrhotic patients (n = 6), (closed circles); healthy subjects (n = 6), (asterix) (mean ± SEM).

Figure 4

Plasma tyrosine (A), cysteine (B) and methionine (C) concentrations in response to protein meals. Twenty grams protein meal, cirrhotics (n = 8), (closed circles); 20 g protein meal, healthy subjects (n = 6), (asterix) (mean ± SEM); 1 g/kg body weight protein meal, cirrhotics (n = 6), (open squares).

Figure 5

Plasma ammonia concentrations in cirrhotic patients. Individual results after a 1g/kg per body weight protein meal.