[Alanine as a nitrogen sparing and gluconeogenetic substrate in the postoperative state (author's transl)]

An alanine infusion (90 mg/kg/h) for eight hours was administered to seven patients after cholecystectomy in order to investigate the influence of elevated plasma alanine levels on the postoperative metabolism. The following metabolites and hormone concentrations were analysed in plasma: glucose, urea, free fatty acids, ketone bodies, amino acids, insulin and glucagon. Compared to the pre-infusion values on the 1. postoperative day after an overnight fasting, the following changes were monitored. The plasma glucose concentrations reached a maximum after four hours of infusion (p less than 0.05). Of the amino acids, significant elevated levels were found for alanine (300%, p less than 0.001), glutamine (36%, p less than 0.05), and alpha-aminobutyrate (61%, p less than 0.01). The free fatty acids and ketone bodies concentrations decreased immediately after the onset of the infusion of alanine (p less than 0.05), the increased again during the last four hours of infusion. The secretion of insulin and also the secretion of glucagon were stimulated by the increased alanine levels. The stimulation of insulin reached a maximum after only five minutes, but the glucagon levels increased continuously until the end of the infusion. During the administration of alanine a nitrogen homeostasis was achieved, which was a significant improvement (p less than 0.001) when compared to saline infusions before and after the alanine infusion.

(1) Postoperative increased plasma levels of alanine stimulate gluconeogenesis and reduce the plasma levels of lipolytic metabolites. The induced stimulation of insulin and glucagon is dependent on the duration of the alanine infusion for during extended infusion of alanine the insulin stimulation diminishes while the glucagon secretion continuously increases. (2) Alanine is a potent anabolic substrate in the immediate postoperative situation.