Response of phenylalanine and leucine kinetics to branched chain-enriched amino acids and insulin in patients with cirrhosis

Gastroenterology. 1996 Jul;111(1):127-37. doi: 10.1053/gast.1996.v111.pm8698191.


Background & aims: We tested the effects of branched chain-enriched, aromatic-deficient amino acids with insulin to correct the altered protein turnover as well as phenylalanine (Phe) and leucine (Leu) rate of appearance in compensated cirrhotics and controls.

Methods: Phe and Leu tracers were infused both before and following intravenous amino acid administration with insulin and euglycemic clamp.

Results: In cirrhosis, fasting whole-body protein synthesis and protein degradation were normal; Phe rate of appearance was greater (P<0.05), whereas Leu rate of appearance/Phe rate of appearance ratio was approximately 35% less than in controls (P<0.001). Following the infusion, protein synthesis did not increase (+1% +/ 5% [NS] vs. +21% +/- 5% [P<0.05] in controls); protein degradation was more suppressed, whereas protein balance increased normally. Total Phe rate of appearance (0.91 +/- 0.13 micromol x kg-1 x min-1) and Leu/Phe disposal ratio (3.53 +/- 0.36) were nearly normalized (fasting controls, 0.68 +/- 0.07 micromol x kg-1 x min-1 and 2.87 +/- 0.14 micromol x kg-1 x min-1, respectively; P>0.05). However, Leu/Phe endogenous rate of appearance ration remained approximately 50% less (1.56 +/- 0.31 vs. 2.87 +/- 0.14; P<0.004) than in controls.

Conclusions: Following this combined infusion in cirrhosis, net protein deposition increased normally despite a blunted response of protein synthesis. Phe and Leu to Phe peripheral disposal were near normalized; however, the exaggerated endogenous Phe production was not corrected entirely.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids, Branched-Chain / administration & dosage
  • Amino Acids, Branched-Chain / therapeutic use*
  • Female
  • Glucose Clamp Technique
  • Humans
  • Infusions, Intravenous
  • Insulin / administration & dosage
  • Insulin / therapeutic use*
  • Kinetics
  • Leucine / blood
  • Leucine / metabolism*
  • Liver Cirrhosis / metabolism
  • Liver Cirrhosis / therapy*
  • Male
  • Middle Aged
  • Parenteral Nutrition
  • Phenylalanine / blood
  • Phenylalanine / metabolism*
  • Protein Biosynthesis
  • Proteins / metabolism


  • Amino Acids, Branched-Chain
  • Insulin
  • Proteins
  • Phenylalanine
  • Leucine