Oral amino acid administration in patients with diabetes mellitus: supplementation or metabolic therapy?

Amino acids are essential for body protein synthesis. Moreover, they can be used to produce energy within the cells. For protein turnover, normal plasma amino acid concentration enhances proteolytic suppression by insulin; furthermore, hyperaminoacidemia can stimulate protein synthesis both in the presence of baseline insulin and in hyperinsulinemic subjects with type 1 diabetes. In humans, the availability of amino acids represents a factor more important than insulin in maintaining protein synthesis in skeletal muscle. Among amino acids, branched-chain amino acids exert an anabolic effect on heart protein metabolism, and their uptake by the myocardium is increased by increasing their circulating concentrations. An important aspect of branched-chain amino acid metabolism in the heart (mainly in the ischemic heart) is that branch-chain amino acid infusion can diminish myocardial lactate; in this way, the inhibition of anaerobic energy phosphate caused by accumulation of lactate can be overridden. Plasma amino acid availability plays an important role in promoting protein synthesis and in energy production, both in peripheral skeletal muscle and in the myocardium.