A simplified method for the preparation of 14C-labelled branched-chain α-oxo acids

Rüdiger, H. W.; Langenbeck, U.; Goedde, H. W.

doi:10.1042/bj1260445

Cited by 150 publications

(24 citation statements)

References 5 publications

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“…The specific activity for muscle was similar to that of rat. The body distribution in the monkey was 48-71% hepatic, 13 (Tables I and II) showed specific entration up to activities similar to those of the 2-4-h postmortem n 0.5 and 8 mM samples. Distribution of body content BCKA dehydrogenase in man was estimated as 60-62% muscular, he findings of 28-32% hepatic, 2% renal, and about 8% in other cytes and fibro-tissues.…”

Section: Resultsmentioning

confidence: 95%

Distribution of branched-chain alpha-keto acid dehydrogenases in primate tissues.

Khatra¹,

Chawla²,

Sewell³

et al. 1977

J. Clin. Invest.

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Section: Resultsmentioning

confidence: 95%

Distribution of branched-chain alpha-keto acid dehydrogenases in primate tissues.

Khatra¹,

Chawla²,

Sewell³

et al. 1977

J. Clin. Invest.

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“…L- [4,5- (17) with final purification by high performance liquid chromatography (HPLC) (18). Na['4C]HCO3 (66 mCi/mmol) was obtained from New England Nuclear, Boston, MA.…”

Section: Methodsmentioning

confidence: 99%

Inverse relationship of leucine flux and oxidation to free fatty acid availability in vivo.

Tessari

Nissen

Miles³

et al. 1986

J. Clin. Invest.

106

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To determine the effect of fatty acid availability on leucine metabolism, 14-h fasted dogs were infused with either glycerol or triglyceride plus heparin, and 46-h fasted dogs were infused with either nicotinic acid or nicotinic acid plus triglyceride and heparin. Leucine metabolism was assessed using a simultaneous infusion of L-14,5-3H]leucine and a-[1-'4Cjketoisocaproate. Leucine, a-ketoisocaproate (KIC), and totalleucine carbon (leucine plus KIC) flux and oxidation rates were calculated at steady state. In 14-h fasted animals, infusion of triglyceride and heparin increased plasma free fatty acids (FFA) by 0.7 mM (P < 0.01) and decreased leucine (P < 0.01), total leucine carbon flux (P < 0.02), and oxidation (P < 0.05). The estimated rate of leucine utilization not accounted for by oxidation and KIC flux decreased, but the changes were not significant. During glycerol infusion, leucine and KIC flux and oxidation did not change.In 46-h fasted dogs, nicotinic acid decreased FFA by 1.0 mM (P < 0.01) and increased (P < 0.05) the rate of leucine and total leucine carbon flux, but did not affect KIC flux. Leucine oxidation increased (P < 0.01) by nearly threefold, whereas nonoxidized leucine utilization decreased. Infusion of triglyceride plus heparin together with nicotinic acid blunted some of the responses observed with nicotinic acid alone.In that changes in oxidation under steady state condition reflect changes in net leucine balance, these data suggest that FFA availability may positively affect the sparing of at least one essential amino acid and may influence whole body protein metabolism.

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“…14 C]leucine as described previously (32), and the KIC purity was examined by ascending TLC chromatography in a butan-1-ol/methanol/water (2:2:1) solvent system and visualized using a GE Typhoon instrument.…”

Section: Islet Isolation and Evaluations Of Insulin Secretion Using Smentioning

confidence: 99%

Transamination Is Required for α-Ketoisocaproate but Not Leucine to Stimulate Insulin Secretion*

Zhou

Jetton

Goshorn

et al. 2010

Journal of Biological Chemistry

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It remains unclear how ␣-ketoisocaproate (KIC) and leucine are metabolized to stimulate insulin secretion. Mitochondrial BCATm (branched-chain aminotransferase) catalyzes reversible transamination of leucine and ␣-ketoglutarate to KIC and glutamate, the first step of leucine catabolism. We investigated the biochemical mechanisms of KIC and leucine-stimulated insulin secretion (KICSIS and LSIS, respectively) using Although leucine oxidation and KIC transamination were blocked in BCATm ؊/؊ islets, KIC oxidation was unaltered.These data indicate that KICSIS requires transamination of KIC and glutamate to leucine and ␣-ketoglutarate, respectively. LSIS does not require leucine catabolism and may be through leucine activation of glutamate dehydrogenase. Thus, KICSIS and LSIS occur by enhancing the metabolism of glutamine/glutamate to ␣-ketoglutarate, which, in turn, is metabolized to produce the intracellular signals such as ATP and NADPH for insulin secretion.To maintain glucose homeostasis in response to a meal, insulin secretion is precisely stimulated by nutrients such as glucose, amino acids, and free fatty acids as well as incretin hormones such as glucagon-like peptide-1. Nutrients are thought to stimulate insulin secretion through metabolic secretion coupling to generate metabolic signals, i.e. second messengers or coupling factors. Extensive research has been conducted to determine how nutrients are metabolized to generate these coupling factors, e.g. ATP and NADPH. Although leucine and ␣-ketoisocaproate (KIC) 3 are potent insulin secretagogues (1), the underlying mechanisms of leucine and KIC-stimulated insulin secretion (LSIS and KICSIS, respectively) remain elusive. A key question is whether their oxidative decarboxylation is required for induction of insulin secretion.

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A simplified method for the preparation of 14C-labelled branched-chain α-oxo acids

Cited by 150 publications

References 5 publications

Distribution of branched-chain alpha-keto acid dehydrogenases in primate tissues.

Distribution of branched-chain alpha-keto acid dehydrogenases in primate tissues.

Inverse relationship of leucine flux and oxidation to free fatty acid availability in vivo.

Transamination Is Required for α-Ketoisocaproate but Not Leucine to Stimulate Insulin Secretion*

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