Changes in leucine kinetics during meal absorption: effects of dietary leucine availability

Journal Article · Sun Jun 01 04:00:00 EDT 1986 · Am. J. Physiol.; (United States)

OSTI ID:7118481

Nissen, S; Haymond, M W

Whole-body leucine and ..cap alpha../-ketoisocaproate (KIC) metabolism were estimated in mature dogs fed a complete meal, a meal devoid of branched-chain amino acids, and a meal devoid of all amino acids. Using a constant infusion of (4,5-/sup 3/H)leucine and ..cap alpha..-(1-/sup 14/C)ketoisocaproate (KIC), combined with dietary (5,5,5-/sup 2/H/sub 3/)leucine, the rate of whole-body proteolysis, protein synthesis, leucine oxidation, and interconversion leucine and KIC were estimated along with the rate of leucine absorption. Digestion of the complete meal resulted in a decrease in the rate of endogenous proteolysis, a small increase in the estimated rate of leucine entering protein, and a twofold increase in the rate of leucine oxidation. Ingestion of either the meal devoid of branched-chain amino acids or devoid of all amino acids resulted in a decrease in estimates of whole-body rates of proteolysis and protein synthesis, decreased leucine oxidation, and a decrease in the interconversion of leucine and KIC. The decrease in whole-body proteolysis was closely associated with the rise in plasma insulin concentrations following meal ingestion. Together these data suggest that the transition from tissue metabolism to anabolism is the result, at least in part, of decreased whole-body proteolysis. This meal-related decrease in proteolysis is independent of the dietary amino acid composition or content. In contrast, the rate of protein synthesis was sustained only when the meal complete in all amino acids was provided, indicating an overriding control of protein synthesis by amino acid availability.

• Research Organization: Mayo Medical School, Rochester, MI
• OSTI ID: 7118481
• Journal Information: Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 250:6; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ABSORPTION
AMINO ACIDS
ANIMALS
BIOSYNTHESIS
CARBON 14 COMPOUNDS
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DECOMPOSITION
DIET
DOGS
INTESTINAL ABSORPTION
LABELLED COMPOUNDS
LEUCINE
MAMMALS
METABOLISM
NUTRITIONAL DEFICIENCY
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDATION
PHYSIOLOGY
PROTEINS
PROTEOLYSIS
SYNTHESIS
TRITIUM COMPOUNDS
UPTAKE
VERTEBRATES