Application of branched-chain amino acids in human pathological states: renal failure.

During renal failure, abnormalities of BCAA and branched-chain keto acid (BCKA) metabolism are due to both the lack of renal contribution to amino acid metabolism and the impact of renal failure and acidosis on whole-body nitrogen metabolism. Abnormal BCAA and BCKA metabolism result in BCAA depletion as reflected by low plasma BCAAs and cellular valine. BCAA metabolic disturbances can alter tissue activities, particularly brain function, and nutritional status. In dialysis patients, BCAA oral supplementation can induce an improvement of appetite and nutritional status. During chronic renal failure, the aims of nutritional interventions are to minimize uremic toxicity, avoid malnutrition and delay progression of kidney disease. BCAA and BCKA supplements have been proposed to decrease further protein intake while maintaining satisfactory nutritional status. In this setting, BCAAs or BCKAs have not been administrated solely but in association with other essential AA or keto analogs. Therefore, the proper effects of BCAAs and/or BCKAs have not been studied separately. Protein restriction together with keto acids and/or essential AAs has been reported to improve insulin sensitivity and hyperparathyroidism and to be compatible with a preservation of nutritional status. Nonetheless, a careful monitoring of protein-calorie intake and nutritional status is needed. A recent meta-analysis concluded that reducing protein intake in patients with chronic renal failure reduces the occurrence of renal death by approximately 40% as compared with larger or unrestricted protein intake. The additional effect of essential amino acids and keto acids on retardation of progression of renal failure has not been demonstrated.