Alanine, arginine, and proline but not glutamine are the feed-back regulators in the liver-alpha cell axis in mice

Abstract

AbstractAimTo identify the amino acids that stimulate glucagon secretion in mice and whether the metabolism of these relies on glucagon receptor signaling.MethodsPancreata of female C57BL/6JRj mice were perfused with 19 individual amino acids (1 mM) and secretion of glucagon was assessed using a specific glucagon radioimmunoassay. Separately, a glucagon receptor antagonist (GRA; 25-2648, 100 mg/kg) or vehicle was administered to female C57BL/6JRj mice three hours prior to an intraperitoneal injection of four different isomolar (in total 7 µmol/g body weight) amino acid mixtures; mixture 1: alanine, arginine, cysteine, and proline; mixture 2: asparatate, glutamate, histidine, and lysine; mixture 3: citrulline, methionine, serine, and threonine; and mixture 4: glutamine, leucine, isoleucine, and valine. Blood glucose, plasma glucagon, amino acid, and insulin concentrations were measured using well characterized methodologies.ResultsAlanine (P=0.03), arginine (P<0.001), and proline (P=0.03) but not glutamine (P=0.2) stimulated glucagon secretion from the perfused mouse pancreas. Cysteine had the numerically largest effect on glucagon secretion but did not reach statistical significance (P=0.08). However, when the four isomolar amino acid mixtures were administered there were no significant difference (P>0.5) in plasma concentrations of glucagon across mixture 1-4. Plasma concentrations of total amino acids were higher after administration of GRA when mixture 1 (P=0.004) or mixture 3 (P=0.04) were injected.ConclusionOur data suggest that alanine, arginine, and proline but not glutamine are involved in the liver-alpha cell axis in mice as they all increased glucagon secretion and their disappearance rate was altered by GRA.Graphical abstract