Branched-chain amino acid supplementation in patients with liver diseases.

Because of their peculiar role in whole-body nitrogen metabolism and the competitive action on amino acid transport across the blood-brain barrier, branched-chain amino acids (BCAAs) have been extensively used in subjects with liver disease to preserve or to restore muscle mass and to improve hepatic encephalopathy. There are no data regarding safe limits of BCAA administration; the results appear to be better when BCAA-enriched formulas or BCAA-supplemented diets are preferred to pure BCAA formulas. Improved nitrogen retention might ameliorate the nutritional status, a prognostic index of long-term survival in cirrhosis and of short-term survival in patients undergoing surgical procedures. The effects on nutrition and ultimately on prognosis of patients with advanced cirrhosis were confirmed in a large multicenter, long-term trial where oral BCAA supplements were compared with equicaloric or equinitrogenous-equicaloric supplements (maltodextrin or lactoalbumin). Similarly, BCAA treatment improved the prognosis of patients with hepatocellular carcinoma, treated by surgical resection or chemoembolization, and of liver transplant patients. The mechanism(s) for the beneficial effects of BCAAs might be mediated by their stimulating activity on hepatocyte growth factor, favoring liver regeneration. The debate regarding the potential effectiveness of BCAAs dates back to the early 1980s. The number of patients who cannot tolerate dietary proteins in amounts sufficient to meet the higher catabolism of advanced liver disease is probably low, but BCAAs remain the sole treatment of proved efficacy in this specific setting.