Serum Branched-Chain Amino and Keto Acid Response to a Protein-Rich Meal in Man

Schauder, P.; Schröder, K. E.; Langenbeck, U.

doi:10.1159/000176843

Cited by 12 publications

(6 citation statements)

References 16 publications

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“…The results of this study agree with previous reports (10,11,15,16); protein ingestion results in significant increases in plasma amino acid concentrations. Large standard deviations reported when the changes in plasma amino acid concentrations were calculated reflect both interindividual and intraindividual variations.…”

Section: Effects Of Protein Ingestion On Plasma Amino Acid Concentrat...supporting

confidence: 93%

Plasma Amino Acid Response to Ingestion of L‐Amino Acids and Whole Protein

Gropper,

Acosta

1993

J. pediatr. gastroenterol. nutr.

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SummaryThe effect of whole protein and L‐amino acid ingestion on plasma amino acid concentrations was investigated in 10 men. Each subject ingested equivalent amounts of amino acids as cottage cheese (session 1), an L‐amino acid mixture (session 2), and cottage cheese and L‐amino acids (session 3). Postprandial changes from baseline were larger for essential versus nonessential amino acids in each session. Higher and more rapid rises followed by more rapid declines in individual plasma amino acid concentrations were observed after ingestion of L‐amino acids alone or with whole protein than after ingestion of an equivalent amount of amino acids as whole protein. Individuals receiving the majority of their essential amino acid and nitrogen needs from elemental products may need, for example, to consume them more frequently or after consumption of other foods in an effort to slow down absorption rates.

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Section: Effects Of Protein Ingestion On Plasma Amino Acid Concentrat...supporting

confidence: 93%

Plasma Amino Acid Response to Ingestion of L‐Amino Acids and Whole Protein

Gropper,

Acosta

1993

J. pediatr. gastroenterol. nutr.

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“…The correlation between plasma leucine and muscle BCKAD activity (21) is most simply explained by inhibition of BCKAD kinase by a-ketoisocaproate (12), the transamination product of leucine. In studies of rats it was found that the concentrations of BCKA in muscle paralleled those ofthe BCAA in rats fed low, normal, or high-protein diets (42), and plasma a-KIC was found to increase in man after a protein meal (43) meal (compare Figs. 3 and 4).…”

Section: Discussionmentioning

confidence: 94%

“…Man however is a meal eater; following a protein meal most of the absorbed amino acids (except for the BCAA) are taken up by the liver, while a large fraction of BCAA is taken up by muscle (58). Because BCAA concentrations in muscle generally parallel plasma concentrations (reviewed in 13) and the latter increase two-to three-fold after a protein meal in man (7,43,58), muscle BCKAD may be activated and likely contributes to the postprandial increase in BCAA oxidation (7). Our studies in rats may have practical implications for nutritional therapy in some patients.…”

Section: Discussionmentioning

confidence: 99%

Modulation of rat skeletal muscle branched-chain alpha-keto acid dehydrogenase in vivo. Effects of dietary protein and meal consumption.

Block¹,

Aftring²,

Mehard³

et al. 1987

J. Clin. Invest.

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The effects of dietary protein on the activity of skeletal muscle branched-chain a-keto acid dehydrogenase (BCKAD) were investigated. BCKAD is rate-limiting for branched-chain amino acid (BCAA) catabolism by muscle; its activity is modulated by phosphorylation-dephosphorylation. In rats fed an adequate protein (25% casein) diet, BCKAD was -2% active postabsorptively and increased to 10% or 16% active after a 25% or 50% protein meal, respectively. Prolonged feeding of a 50% protein diet increased postabsorptive BCKAD activity to 7% with further increases to 40% active postprandially. On a low protein (9% casein) diet BCKAD remained -2% active regardless of meal-feeding. Dose-dependent activation of BCKAD by intravenous leucine in postabsorptive rats was blunted by a low protein diet. We conclude that excesses of dietary protein enhance the capacity of skeletal muscle to oxidize BCAA, muscle conserves BCAA when protein intake is inadequate, and skeletal muscle may play an important role in whole-body BCAA homeostasis.

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“…Therefore, two regimens of intravenous phenylalanine administration have been studied during hyperglycaemic clamp conditions. The lower infusion rate resulted in phenylalanine concentrations just above those measured after a meat meal [38] and did not significantly augment insulin secretion. On the other hand, phenylalanine administration (intraduodenally, 20 g over 60 min; intravenously, 12.8 g over 60 min) resulting in supraphysiological plasma levels had an insulinotropic effect.…”

Section: Discussionmentioning

confidence: 71%

“…The plasma phenylalanine concentrations reached with our regimen of intraduodenal administration were far above those observed postprandially [37] and even after a large oral protein load [38]. Therefore, two regimens of intravenous phenylalanine administration have been studied during hyperglycaemic clamp conditions.…”

Section: Discussionmentioning

confidence: 99%

Lack of insulinotropic effect of endogenous and exogenous cholecystokinin in man

Reimers¹,

Nauck²,

Creutzfeldt³

et al. 1988

Diabetologia

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Intraduodenal phenylalanine administration (333 mg/min over 60 min) released endogenous cholecystokinin in healthy young subjects as demonstrated radioimmunologicaily and by intraduodenal bilirubin and pancreatic enzyme output. Concomitantly, there was only a small increase over basal in circulating immunoreactive-insulin and immunoreactive-C-peptide concentrations. In healthy volunteers intraduodenal infusions of saline (10 ml/min), glucose (333 mg/min) or phenylalanine (333 mg/min) were performed for 60 rain when plasma glucose was clamped at approximately 8 mmol/l. Phenylalanine enhanced immunoreactive-insulin and immunoreactive-C-peptide responses three-fold more than did the same amount of glucose. Immuno-reactive gastric inhibitory polypeptide responses were small and not different after glucose and phenylalanine administration, lmmunoreactive cholecystokinin was significantly stimulated to 9.4_+ 1.4 pmol/l only by intraduodenal phenylalanine. Plasma phenylalanine concentrations increased into the supraphysiological range (approximately 1.5 mmol/l). Intravenous infusions of phenylalanine achieving plasma concentrations of 1.2 mmol/l stimulated insulin secretion at elevated plasma glucose concentrations (approximately 8 mmol/l clamp experiments), but had no effect at basal plasma glucose concentrations. A small increase in cholecystokinin also was observed. Intravenous infusions of synthetic sulphated cholecystokinin-8 leading to plasma concentrations in the upper postprandial range (8-12 pmol/l) did not augment the immunoreactive-insulin or immunoreactive-C-peptide levels during hyperglycaemic clamp experiments, in the absence or presence of elevated plasma phenylalanine concentrations. It is concluded that the augmentation of the glucose-induced insulin release by intraduodenal administration of phenylalanine cannot be related to cholecystokinin release, but rather is explained by the combined effects of elevated glucose and phenylalanine concentrations. In man, cholecystokinin does not augment insulin secretion caused by moderate hyperglycaemia, elevations of phenylalanine concentrations, or combinations thereof.

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Serum Branched-Chain Amino and Keto Acid Response to a Protein-Rich Meal in Man

Cited by 12 publications

References 16 publications

Plasma Amino Acid Response to Ingestion of L‐Amino Acids and Whole Protein

Plasma Amino Acid Response to Ingestion of L‐Amino Acids and Whole Protein

Modulation of rat skeletal muscle branched-chain alpha-keto acid dehydrogenase in vivo. Effects of dietary protein and meal consumption.

Lack of insulinotropic effect of endogenous and exogenous cholecystokinin in man

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