Effects of branched-chain amino acids on nitrogen metabolism in patients with cirrhosis.
This study was conducted to determine whether an amino acid solution enriched with branched-chain amino acids altered protein catabolic rates and plasma ammonia in patients with cirrhosis. Nine stable subjects were given two peripheral intravenous infusions: a standard amino acid solution (solution A) and a branched-chain-enriched solution containing 97% more leucine (solution B). Each solution was given for separate 9-day (group 1, n = 6) or 3-day (group 2, n = 3) periods. Amino acid solutions delivered 0.7 gm protein.kg-1.day-1. Diets provided an additional 0.3 gm protein plus maintenance calories. Protein turnover was assessed by a primed continuous infusion of [1-14C] leucine in six patients (three patients in group 1 and three patients in group 2). Nitrogen balance and urinary 3-methyl histidine excretion were determined in group 1 patients. Compared with solution A, solution B increased leucine flux and leucine oxidation but had no significant effect on protein synthesis or catabolism based on the plasma specific activity of either leucine or alpha-ketoisocaproic acid. The additional leucine infused with solution B was quantitatively oxidized. Nitrogen balance did not differ with the two solutions and there was also no difference in the urinary excretion of 3-methyl histidine, suggesting that muscle protein catabolism was unchanged. Plasma ammonia concentration decreased significantly during the infusion of solution B and was associated with a slight fall in plasma glucagon concentration. The results indicated that a branched-chain-enriched amino acid solution did not alter protein synthesis or catabolism although it did lower the plasma ammonia when compared with a standard amino acid formula in stable cirrhotic patients.
Department of Medicine, Veterans Administration Medical Center, Cleveland, Ohio.
F L
FL
Weber
B S
BS
Bagby
L
L
Licate
S G
SG
Kelsen
D000596:Amino Acids / Q000097:blood; D000597:Amino Acids, Branched-Chain / Q000494:pharmacology*; D000641:Ammonia / Q000097:blood; D005934:Glucagon / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D007930:Leucine / Q000378:metabolism / Q000494:pharmacology; D008103:Liver Cirrhosis / Q000378:metabolism*; D008762:Methylhistidines / Q000652:urine; D009584:Nitrogen / Q000378:metabolism*
D000596:Amino Acids; D000597:Amino Acids, Branched-Chain; D007328:Insulin; D008762:Methylhistidines; D000641:Ammonia; D005934:Glucagon; D007930:Leucine; C028118:3-methylhistidine; D009584:Nitrogen