title: Dissociation of the effects of epinephrine and insulin on glucose and protein metabolism.
abstract: The separate and combined effects of insulin and epinephrine on leucine metabolism were examined in healthy young volunteers. Subjects participated in four experimental protocols: 1) euglycemic insulin clamp (+80 microU/ml), 2) epinephrine infusion (50 ng.kg-1.min-1) plus somatostatin with basal replacement of insulin and glucagon, 3) combined epinephrine (50 ng.kg-1.min-1) plus insulin (+80 microU/ml) infusion, and 4) epinephrine and somatostatin as in study 2 plus basal amino acid replacement. Studies were performed with a prime-continuous infusion of [1-14C]leucine and indirect calorimetry. Our results indicate that 1) hyperinsulinemia causes a generalized decrease in plasma amino acid concentrations, including leucine; 2) the reduction in plasma leucine concentration is primarily due to an inhibition of endogenous leucine flux; nonoxidative leucine disposal decreases after insulin infusion; 3) epinephrine, without change in plasma insulin concentration, reduces plasma amino acid levels; 4) combined epinephrine-insulin infusion causes a greater decrease in plasma amino levels than observed with either hormone alone; this is because of a greater inhibition of endogenous leucine flux; and 5) when basal amino acid concentrations are maintained constant with a balanced amino acid infusion, epinephrine inhibits the endogenous leucine flux. In conclusion, the present results do not provide support for the concept that epinephrine is a catabolic hormone with respect to amino acid-protein metabolism. In contrast, epinephrine markedly inhibits insulin-mediated glucose metabolism.
authors.affiliation: Diabetes Division, University of Texas Health Science Center, San Antonio 78284.
authors.forename: P
authors.initials: P
authors.lastname: Castellino
authors.forename: L
authors.initials: L
authors.lastname: Luzi
authors.forename: S
authors.initials: S
authors.lastname: Del Prato
authors.forename: R A
authors.initials: RA
authors.lastname: DeFronzo
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000097:blood; D001639:Bicarbonates / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism*; D002096:C-Peptide / Q000097:blood; D002245:Carbon Dioxide / Q000032:analysis; D002250:Carbon Radioisotopes; D004837:Epinephrine / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D005934:Glucagon / Q000097:blood; D015309:Glucose Clamp Technique; D006801:Humans; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D007332:Insulin Infusion Systems; D007930:Leucine / Q000097:blood / Q000378:metabolism*; D010084:Oxidation-Reduction; D011506:Proteins / Q000378:metabolism*; D011865:Radioisotope Dilution Technique; D012119:Respiration
chemical_list: D000596:Amino Acids; D001639:Bicarbonates; D001786:Blood Glucose; D002096:C-Peptide; D002250:Carbon Radioisotopes; D007328:Insulin; D011506:Proteins; D002245:Carbon Dioxide; D005934:Glucagon; D007930:Leucine; D004837:Epinephrine