Are branched chain amino-acids beneficial for nutrition of severe surgical patients with sepsis?

Mechanism of liver tyrosine aminotransferase increase in ethanol-treated mice and its effect on serum tyrosine level

Liver tyrosine aminotransferase (TAT) activity is known to increase with ethanol treatment; however, the mechanism of this increase is unclear. Upon investigation we found that TAT activity and mRNA levels started to increase 2 h after ethanol administration and continued to increase until 6 h after ethanol administration. The increase in ethanol-induced TAT activity could not be explained by calorie loading after fasting, since ethanol loading increased TAT expression, while glucose loading decreased TAT expression. In addition, liver TAT activity was not related to serum tyrosine levels. TAT activity increased when an adenosine A2 agonist, 5'-N-ethylcarboxamide adenosine, was given. Since TAT activity is increased by cAMP, and ethanol increases cAMP production via an adenosine receptor-dependent mechanism, this increase in ethanol-induced TAT activity may occur via an adenosine receptor-dependent mechanism.

Therapeutic use of branched-chain amino acids in burn, trauma, and sepsis

Various experimental studies conducted in the 1970s demonstrated, at least in the physiological situation, the anabolic and/or anticatabolic properties of branched-chain amino acids (leucine, valine, isoleucine) or their ketoacid derivatives. This led to several clinical studies in the late 1970s and early 1980s that aimed to evaluate the potential benefits of BCAA supplementation in nutritional support of the critically ill. The data on burn, trauma, and sepsis are, however, far from convincing. Besides significant discrepancies in their results and the fact that most of these studies involved very small populations of patients, few of them meet the current standards of therapeutic evaluation. However, some positive results in specific studies suggest that the underlying concept may be correct but that interpretation has been faulty. Indeed, we know now that while the BCAAs possess regulatory properties on protein metabolism, leucine is by far the most potent, while isoleucine and valine are inefficient. However, in the above-mentioned studies, BCAA-supplemented nutrition very frequently supplied almost equivalent amounts of all 3 BCAAs. Moreover, several studies were performed without adequate basal nutritional support, which most probably hampered the correct metabolic utilization of these amino acids. Taken together, these factors mean that the demonstrations of BCAA efficacy were fortunate in the least. In contrast, more recently, leucine was demonstrated to positively affect protein synthesis in an experimental model of sepsis or burn. In parallel, 2 prospective controlled trials of BCAA supplementation in septic patients also demonstrated an improvement in patients' nutritional status and outcome. Thus, we should abandon the concept of BCAA-supplemented nutrition for a more promising leucine-supplemented nutrition that requires further evaluation.

The impact of leucine infusion on skeletal muscle amino acid and energy metabolism in severely traumatized patients

The response to trauma is associated with increased energy requirements and net protein breakdown. The branched chain aminoacids, especially leucine, are considered to act by serving as a fuel for muscle tissue and by stimulating synthesis of proteins and controlling protein breakdown. Such results have been obtained mainly from in vitro studies. The present study was designed to evaluate the pharmacological effect of leucine infusion on muscle energy/amino acid metabolism in man after severe multiple trauma. 16 patients were studied and randomly allocated into 2 groups. Group 1 was given fat and 20% glucose while group 2 received 6 g N in form of leucine dissolved in 10% glucose solution and fat. The patients received 40 kcal/kg/24 h over an 8 day period after trauma. Biochemical analyses, muscle biopsies (energy substrates, electrolytes, amino acids), nitrogen balance and 3-methyl histidine excretion in urine were evaluated. Biochemical data revealed a significant increase (p < 0.05) of serum urea in group 2 day 4 and 8 after trauma. Muscle intracellular electrolytes (K(+), Mg(2+)) and energy substrates (ATP, phosphocreatine) showed a similar decrease in both groups. The intracellular muscle amino acids displayed a pattern known to be related to trauma without differences between the groups. The cumulative nitrogen balance 8 days after the injury was -93.5 g N +/- 10.1 (SEM) in group 1 and -73 g N +/- 7.5 in group 2. The 3-methylhistidine excretion was markedly increased similar in both groups. The present study demonstrated no significant pharmacological effect of leucine administration on muscle metabolism, nitrogen balance or 3-methylhistidine excretion in severely traumatized patients. Conventional balanced amino acid solutions are probably optimal to meet the patients actual requirements.

Prospective randomized double-blind trial of branched chain amino acid enriched versus standard parenteral nutrition solutions in traumatized and septic patients

The addition of branched chain amino acids (BCAA) to total parenteral nutrition (TPN) solutions of balanced aminoacid composition has been reported to result in improved nitrogen balance, preservation of plasma protein levels, and improved immune function; however, only a few large clinical studies have been performed, yielding conflicting results. We, therefore, studied in a prospective, randomized double blind trial, the effects of BCAA enrichment of an otherwise isonitrogenous and isocaloric TPN solution on plasma protein levels in 101 traumatized and septic patients. TPN-derived nitrogen intake was similar in both study groups. Nitrogen balances in the BCAA group (n = 49) were not different from those in the standard group (n = 52). Plasma total protein levels increased significantly in the standard group resulting in a significant difference between study groups on day 7. Pre-albumin levels increased significantly in the BCAA group and in the standard group. The number of neutrophils (rods) was significantly lower in the standard group compared to the BCAA group on day 7. Lymphocytes increased significantly in the standard group as did the number of platelets, resulting in a significant difference between study groups on day 7. We conclude that BCAA enrichment of standard TPN solutions does not result in more efficient nitrogen metabolism in septic or traumatized patients.