Valine metabolism in vivo: Effects of high dietary levels of leucine and isoleucine

Block, Kevin P.; Harper, Alfred E.

doi:10.1016/0026-0495(84)90012-x

Cited by 72 publications

(39 citation statements)

References 42 publications

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“…4). The fraction of isoleucine flux used for oxidation was similar during the saline and the amino acid infusion periods with median values of 30% (range 28-42) and 24% (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34), respectively (p > 0.05). Consequently, the nonoxidative portion of isoleucine flux, representing protein synthesis decreased similarly between the two periods, from a median of 206 nmol/kg bw/min (range 119-425) during the saline infusion to a median of 80 nmol/kg bw/min (range 56-120, p < 0.05) during the amino acid infusion, respectively.…”

Section: Resultsmentioning

confidence: 91%

Protein synthesis is severely diminished following a simulated upper GI bleed in patients with cirrhosis

Damink

Jalan

Deutz

et al. 2008

Journal of Hepatology

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Section: Resultsmentioning

confidence: 91%

Protein synthesis is severely diminished following a simulated upper GI bleed in patients with cirrhosis

Damink

Jalan

Deutz

et al. 2008

Journal of Hepatology

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“…It appears well established that leucine activates BCKA dehydrogenase (12). For example, oral administration of leucine in rats is followed by prompt activation of BCKA dehydrogenase and enhancement of valine oxidation (24). The mechanism of enzyme activation appears to be inhibition of phosphorylation of BCKA dehydrogenase by leucine (25,26).…”

Section: Resultsmentioning

confidence: 99%

Effect of dietary fat, carbohydrate, and protein on branched-chain amino acid catabolism during caloric restriction.

Vazquez¹,

Morse²,

Adibi³

1985

J. Clin. Invest.

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To assess the effect of each dietary caloric source on the catabolism of branched-chain amino acids, we investigated the rate of leucine oxidation before and after obese volunteers consumed one of the following diets for one week: (a) starvation, Starvation significantly increased the rate of leucine oxidation (1.4±0.11 vs. 1.8±0.16 mmol/h, P < 0.01). The same occurred with the fat and protein diets. In sharp contrast, the 500-cal carbohydrate diet significantly decreased the rate of leucine oxidation (13±0.13 vs. 0.6±0.09 mmol/h, P < 0.01). The same occurred when a portion of the carbohydrate diet was isocalorically replaced with either fat or protein. The cumulative nitrogen excretion during the fat diet and starvation was not significantly different. As compared with the fat diets, the carbohydrate diets on the average reduced the urinary nitrogen excretion by 12 g/wk. Nitrogen balance was positive during the consumption of the 500-cal protein diet, but negative during the consumption of carbohydrate-protein diet. The fat diets, like the protein diets and starvation, greatly increased plasma leucine (119±13 vs. 222±15 uM, P < 0.01) and 0-hydroxybutyrate (0.12+0.02 vs. 4.08±0A3 mM, P < 0.01) concentrations, and significantly decreased plasma glucose (96±4 vs. 66±3 mg/dl, P < 0.01) and insulin (18±4 vs. 9±1 MU/nl, P < 0.05) concentrations. These changes did not occur, or were greatly attenuated, when subjects consumed carbohydrate alone or in combination with fat or protein.We conclude that (a) during brief caloric restriction, dietary lipid and protein, unlike carbohydrate, do not diminish the catabolism of branched-chain amino acids and (b) the decrease in branched-chain amino acid oxidation is associated with protein sparing.

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“…26,27 Therefore, the high plasma leucine concentration that results from an upper GI bleed may stimulate BCAA oxidation, irrespective of the level of isoleucine, resulting in a further depression of plasma and tissue isoleucine concentrations. 6,28 The administration of the simulated bleed did not result in a positive NB in any of the organs studied. This supports our hypothesis that the limited availability of isoleucine prevents the normal stimulatory effect of hyperaminoacidemia on protein synthesis that follows an amino acid meal.…”

Section: Discussionmentioning

confidence: 99%

Isoleucine infusion during “simulated” upper gastrointestinal bleeding improves liver and muscle protein synthesis in cirrhotic patients

et al. 2007

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Upper gastrointestinal (GI) bleeding in cirrhotic patients has a high incidence of mortality and morbidity. Postbleeding catabolism has been hypothesized to be partly due to the low biological value of hemoglobin, which lacks the essential amino acid isoleucine. The aims were to study the metabolic consequences of a "simulated" upper GI bleed in patients with cirrhosis of the liver and the effects of intravenous infusion of isoleucine. Portal drained viscera, liver, muscle, and kidney protein kinetics were quantified using a multicatheterization technique during routine portography. Sixteen overnight-fasted, metabolically stable patients who received an intragastric infusion of an amino acid solution mimicking hemoglobin every 4 hours were randomized to saline or isoleucine infusion and received a mixture of stable isotopes (L-[ring-2 H 5 ]phenylalanine, L-[ring-2 H 4 ]tyrosine, and L-[ring-2 H 2 ]tyrosine) to determine organ protein kinetics. This simulated bleed resulted in hypoisoleucinemia that was attenuated by isoleucine infusion. Isoleucine infusion during the bleed resulted in a positive net balance of phenylalanine across liver and muscle, whereas renal and portal drained viscera protein kinetics were unaffected. In the control group, no significant effect was shown. Conclusion: The present study investigated hepatic and portal drained viscera protein metabolism selectively in humans. The data show that hepatic and muscle protein synthesis is stimulated by improving the amino acid composition of the upper GI bleed by simultaneous intravenous isoleucine administration. (HEPATOLOGY 2007;45:560-568.)

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Valine metabolism in vivo: Effects of high dietary levels of leucine and isoleucine

Cited by 72 publications

References 42 publications

Protein synthesis is severely diminished following a simulated upper GI bleed in patients with cirrhosis

Protein synthesis is severely diminished following a simulated upper GI bleed in patients with cirrhosis

Effect of dietary fat, carbohydrate, and protein on branched-chain amino acid catabolism during caloric restriction.

Isoleucine infusion during “simulated” upper gastrointestinal bleeding improves liver and muscle protein synthesis in cirrhotic patients

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