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

Abstract

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. (Gastroenterology 1996 Jul;111(1):127-37)