Anticatabolic properties of branched chain amino-acids in post-operative patients. A prospective study

The effect of infusion of branched chain amino-acids (BCAA) on post-operative protein metabolism was analysed in 19 elective surgical patients treated for the first 5 post-operative days with a nutritional regimen of 30 kcal kg(-1) day(-1) and 2 g of amino-acids kg(-1) day(-1). The patients were divided into three groups whose only difference was the amount of BCAA delivered. Our results showed that an increased BCAA input improved nitrogen balance and reduced protein catabolism as estimated by the excretion of 3-methyl-histidine. Since nitrogen retention was maximal during the first 3 post-operative days and the reduction in 3-methylhistidine excretion was observed only on post-operative days 4 and 5, a dual action of BCAA on improving protein synthesis and reducing catabolism is postulated, even though the reduction in catabolism seems to be the main action. This dual action may reflect the unique role of BCAA, which is both 'nutritional' (as they constitute 40% of total amino-acid daily requirements of the healthy subject) and 'pharmacological (as they reduce protein catabolism and improve synthesis in muscle and liver with a dose-dependent effect). Of the three BCAA, isoleucine and leucine seemed to have an 'anticatabolic' effect, whereas an analysis of literature data showed that valine probably has none.