Splanchnic sequestration of amino acids during aging: arginine or glutamine, who is the culprit?

Abstract

Background Splanchnic sequestration of amino acids (SSAA) may be involved in of age-related modifications of nitrogen homeostasis. An alteration of arginine and/or glutamine metabolism could participate to SSAA since both AA control nitrogen homeostasis. Objectives To gain further insight into SSAA by characterizing the effect of aging on interorgan exchanges of arginine and glutamine. Methods male adult or old rats were studied in the postprandial state under anesthesia. After one hour of infusion of nutrition into the duodenum, samples were taken from the carotid artery, portal vein, hepatic vein, renal vein and vena cava to measure glutamine and arginine levels (HPLC). Results Flux in nmol/100g carcass weight/min = ([vein]-[artery]) x blood flow Discussion Arginine and glutamine are major activators of ureagenesis, promoting their own catabolism but also the catabolism of other AA. Our results show that aging is associated with a preferential use of glutamine over arginine in the liver. In fact, the whole body homeostasis of glutamine is modified with aging, with in particular a significant reduction in muscular glutamine release. In conclusion, glutamine and not arginine appears to be the AA of interest in SSAA. It is now important to identify the molecular targets involved in this process.