Biomaterial Database

Effects of fasting on flux and interconversion of leucine and alpha-ketoisocaproate in vivo. 1981

S Nissen, and M W Haymond

To determine directly the interconversion of circulating leucine and alpha-ketoisocaproate (KIC) in vivo, as well as the effects of fasting on leucine and KIC metabolism, 14- and 96-h fasted dogs were studied during simultaneous infusion of L-[4,5-3H]leucine and [U-14C]KIC. The specific radioactivities of 3H- and 14C-labeled leucine and KIC were determined and transfer rates calculated using a two-pool reversible model. In both groups, approximately 32% of the total leucine carbon entering was converted to KIC, whereas 60% of circulating KIC is converted to leucine. Plasma [3H]KIC specific radioactivity was only half of the circulating [3H]leucine specific activity, suggesting entry of KIC from an unlabeled pool. Fasting decreased the leucine-KIC interconversion, entry of unlabeled KIC, and irreversible loss of KIC. These data demonstrate that interconversion of circulating leucine and KIC is extensive and that fasting decreases the conversion of leucine to KIC in the labeled and unlabeled KIC pools, suggesting that transamination is a major regulator of leucine metabolism in fasting dogs.

UI	MeSH Term	Description	Entries
D007651	Keto Acids	Carboxylic acids that contain a KETONE group.	Oxo Acids,Oxoacids,Acids, Keto,Acids, Oxo
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D007930	Leucine	An essential branched-chain amino acid important for hemoglobin formation.	L-Leucine,Leucine, L-Isomer,L-Isomer Leucine,Leucine, L Isomer
D008297	Male		Males
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D002208	Caproates	Derivatives of caproic acid. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain a carboxy terminated six carbon aliphatic structure.	Hexanoates,Caproic Acid Derivatives,Caproic Acids,Hexanoic Acid Derivatives,Hexanoic Acids,Acid Derivatives, Caproic,Acid Derivatives, Hexanoic,Acids, Caproic,Acids, Hexanoic,Derivatives, Caproic Acid,Derivatives, Hexanoic Acid
D002250	Carbon Radioisotopes	Unstable isotopes of carbon that decay or disintegrate emitting radiation. C atoms with atomic weights 10, 11, and 14-16 are radioactive carbon isotopes.	Radioisotopes, Carbon
D004285	Dogs	The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)	Canis familiaris,Dog
D005215	Fasting	Abstaining from FOOD.	Hunger Strike,Hunger Strikes,Strike, Hunger,Strikes, Hunger
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia