Effect of fasting and fasting-refeeding on conversion of leucine into CO 2 and lipids in rats

Meikle, A.W.; Klain, GJ

doi:10.1152/ajplegacy.1972.222.5.1246

Cited by 60 publications

(23 citation statements)

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“…The effect of glutamate. The data in Table IV demonstrate that isolated hemidiaphragms can discriminate between two leucine concentrations (0.1 and 0.5 mM) that are within the range of leucine concentrations found in rat serum (2,4,17) and furthermore that the enhancement of…”

Section: Resultsmentioning

confidence: 53%

“…Re-cently, several laboratories reported that the rate of oxidation of the branched-chain amino acids by muscles is under metabolic and hormonal regulation (2,3,(5)(6)(7)(8)(9). It is stimulated by fasting (2,6,7), severe stress (8), and uncontrolled diabetes (9), conditions that are associated with wasting of muscle protein and negative nitrogen balance.…”

Section: Introductionmentioning

confidence: 99%

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Leucine. A possible regulator of protein turnover in muscle.

Buse¹,

Reid²

1975

J. Clin. Invest.

695

250

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Section: Resultsmentioning

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Leucine. A possible regulator of protein turnover in muscle.

Buse¹,

Reid²

1975

J. Clin. Invest.

695

250

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“…At all substrate concentrations tested 4-methyl-2-oxopentanoate was oxidized faster by hemidiaphragms than leucine, and this difference was also observed at relatively high substrate concentrations (1 mM), which exceeded the physiological range of leucine concentration in rat plasma (Scharff & Wool, 1966;Meikle & Klain, 1972). One oftwo explanations appears likely: (1) the transport of 4-methyl-2-oxopentanoate into muscle cells, or into a specific compartment of muscle cells, is faster than the transport of leucine; (2) under our conditions in vitro transamination was limiting the rate of leucine oxidation by hemidiaphragms.…”

Section: Discussionmentioning

confidence: 93%

“…The circulating concentrations of branched-chain amino acids are increased during fasting (Felig et al, 1969;Adibi, 1971;Meikle & Klain, 1972) and insulin deficiency (Carlsten et al, 1966;Scharff & Wool, 1966) in humans and rats. Isolated hemi-diaphragms and sciatic nerves from diabetic rats appear to oxidize [L1-4C]leucine faster thanthosefrom controls (Herlong et al, 1974).…”

mentioning

confidence: 99%

Regulation of branched-chain amino acid oxidation in isolated muscles, nerves and aortas of rats

Buse¹,

Jursinic²,

Reid³

1975

Biochemical Journal

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1. The oxidation of the three branched-chain amino acids was regulated in parallel fashion in rat tissues studied in vitro. 2. With 0.1 mM-[1-14C]isoleucine as substrate in the presence of 5.5 mM-glucose, 14CO2 production was 0.6 mumol/2 h per g in the aorta, 0.3 in peripheral nerve, 0.2 in muscle and 0.13 in spinal cord. 3. The ratio 14C oxidized/14C incorporated into proteins with 0.1 mM-[1-14C]leucine was 1.3 in hemidiaphragms, 3.3 in sciatic nerve and 1.0 in nerves undergoing Wallerian degeneration. Leucine oxidation decreased only slightly during degeneration, but protein synthesis doubled. 4. Hemidiaphragms incubated with [1-14C]leucine or 4-methyl-2-oxo[1-14C]pentanoate increased 14CO2 production 7-9-fold as substrate concentration was increased from 0.1 to 0.5 mM; under the same conditions 14CO2 production by nerves increased only 2-3-fold. 5. 2-Oxoglutarate stimulated the oxidation of the branched-chain amino acids by muscles and peripheral nerves and the oxidation of 4-methyl-2-oxopentanoate by hemidiaphragms but not by nerves. 6. Octanoate (0.1-1.0 mM) markedly stimulated the oxidation of branched-chain amino acids and of 4-methyl-2-oxopentanoate in hemidiaphragms, but inhibited oxidation of both by peripheral nerves and spinal cord. In aortas, oxidation of isoleucine (the only substance tested) was inhibited by octanoate. 7. The effects of octanoate and 2-oxoglutarate on leucine oxidation by hemidiaphragms were additive at low concentrations. When maximally stimulating concentrations of either agent were used, addition of the other was ineffective. 8. Pyruvate inhibited the oxidation of branched-chain amino acids and 4-methyl-2-oxopentanoate in all tissues tested. 9. Insulin did not affect the oxidation of 4-methyl-2-oxopentanoate by muscles or nerves. 10. The oxidative decarboxylation of the branched-chain alpha-oxo acids is suggested as a regulatory site of branched-chain amino acid oxidation. Differences in regulation between muscle on the one hand, and nerve and aorta on the other, are discussed.

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“…Patients with hereditarv disorders such as mlaple syrup urine disease and isovaleric acidemia, in which the oxidationi of these aminio acids is impaired, often have life-threateninig metabolic derangemenits (1). Unlike other aminlo acids, which are oxidized mostly in the liver, the oxidationi of branched-chain amino acids is accomiiplislhed principally in the skeletal muscle (2)(3)(4)(5).…”

Section: Introductionmentioning

confidence: 99%

Leucine Oxidation and Protein Turnover in Clofibrate-induced Muscle Protein Degradation in Rats

Paul¹,

Adibi²

1980

J. Clin. Invest.

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A B S T R A C T Treatment of hvperlipidemia withclofibrate may result in development of a muscular svndrome. Our previous investigation (1979. J. ClitG. Ivce.st. 64: 405.) showed that chronic administration of clofibrate to rats causes mvotonia and decreases glucose and fatty acid oxidation and total protein of skeletal muscle. In the present experimiients we have investigated amino acid and protein metabolism in these rats. Clofibrate administratioin decreased the concenitration of all three branched-chain amino acids without affecting those of others in muscle. Studies to examine the mechanism of decreases in muscle concenitrationis of branched-chain amiiino acids showed the followiing: (a)

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Effect of fasting and fasting-refeeding on conversion of leucine into CO 2 and lipids in rats

Cited by 60 publications

References 0 publications

Leucine. A possible regulator of protein turnover in muscle.

Leucine. A possible regulator of protein turnover in muscle.

Regulation of branched-chain amino acid oxidation in isolated muscles, nerves and aortas of rats

Leucine Oxidation and Protein Turnover in Clofibrate-induced Muscle Protein Degradation in Rats

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