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2 Oxoisocaproic Acid

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Brennan L. – One of the best experts on this subject based on the ideXlab platform.

  • Prolonged L-alanine exposure induces changes in metabolism, Ca2+ handling and desensitization of insulin secretion in clonal pancreatic ß-cells
    'Portland Press Ltd.', 2009
    Co-Authors: Mcclenaghan N., Scullion S., Mion B., Hewage C., Malthouse J., Flatt P., Newsholme Philip, Brennan L.

    Abstract:

    Acute insulin-releasing actions of amino Acids have been studied in detail, but comparatively little is known about the ß-cell effects of long-term exposure to amino Acids. The present study examined the effects of prolonged exposure of ß-cells to the metabolizable amino Acid L-alanine. Basal insulin release or cellular insulin content were not significantly altered by alanine culture, but acute alanine-induced insulin secretion was suppressed by 74% (P<0.001). Acute stimulation of insulin secretion with glucose, KCl or KIC (2Oxoisocaproic Acid) following alanine culture was not affected. Acute alanine exposure evoked strong cellular depolarization after control culture, whereas AUC (area under the curve) analysis revealed significant (P<0.01) suppression of this action after culture with alanine. Compared with control cells, prior exposure to alanine also markedly decreased (P < 0.01) the acute elevation of [Ca2+]i (intracellular [Ca2+]) induced by acute alanine exposure. These diminished stimulatory responses were partially restored after 18 h of culture in the absence of alanine, indicating reversible amino-Acid-induced desensitization. 13C NMR spectra revealed that alanine culture increased glutamate labelling at position C4 (by 60 %; P < 0.01), as a result of an increase in the singlet peak, indicating increased flux through pyruvate dehydrogenase. Consistent with this, protein expression of the pyruvate dehydrogenase kinases PDK2 and PDK4 was significantly reduced. This was accompanied by a decrease in cellular ATP (P < 0.05), consistent with diminished insulin-releasing actions of this amino Acid. Collectively, these results illustrate the phenomenon of ß-cell desensitization by amino Acids, indicating that prolonged exposure to alanine can induce reversible alterations to metabolic flux, Ca2+ handling and insulin secretion. © The Authors Journal compilation © 2009 Biochemical Society

Lorraine Brennan – One of the best experts on this subject based on the ideXlab platform.

  • Prolonged L-alanine exposure induces changes in metabolism, Ca2+ handling and desensitization of insulin secretion in clonal pancreatic β-cells
    Clinical science (London England : 1979), 2009
    Co-Authors: Neville H. Mcclenaghan, Siobhan M. Scullion, B. Mion, Chandralal M. Hewage, J. Paul G. Malthouse, Peter R. Flatt, Philip Newsholme, Lorraine Brennan

    Abstract:

    Acute insulin-releasing actions of amino Acids have been studied in detail, but comparatively little is known about the beta-cell effects of long-term exposure to amino Acids. The present study examined the effects of prolonged exposure of beta-cells to the metabolizable amino Acid L-alanine. Basal insulin release or cellular insulin content were not significantly altered by alanine culture, but acute alanine-induced insulin secretion was suppressed by 74% (P < 0.001). Acute stimulation of insulin secretion with glucose, KCI or KIC (2Oxoisocaproic Acid) following alanine culture was not affected. Acute alanine exposure evoked strong cellular depolarization after control culture, whereas AUC (area under the curve) analysis revealed significant (P < 0.01) suppression of this action after culture with alanine. Compared with control cells, prior exposure to alanine also markedly decreased (P < 0.01) the acute elevation of [Ca2+](i), (intracellular [Ca2+]) induced by acute alanine exposure. These diminished stimulatory responses were partially restored after 18 h of culture in the absence of alanine, indicating reversible amino-Acid-induced desensitization. C-13 NMR spectra revealed that alanine culture increased glutamate labelling at position C4 (by 60%; P < 0.01), as a result of an increase in the singlet peak, indicating increased flux through pyruvate dehydrogenase. Consistent with this, protein expression of the pyruvate dehydrogenase kinases PDK2 and PDK4 was significantly reduced. This was accompanied by a decrease in cellular ATP (P < 0.05), consistent with diminished insulin-releasing actions of this amino Acid. Collectively, these results illustrate the phenomenon of beta-cell desensitization by amino Acids, indicating that prolonged exposure to alanine can induce reversible alterations to metabolic flux, Ca2+ handling and insulin secretion.

Claudia Först – One of the best experts on this subject based on the ideXlab platform.

  • Hydroxycarboxylic and oxocarboxylic Acids in urine: products from branched-chain amino Acid degradation and from ketogenesis.
    Journal of Chromatography B: Biomedical Sciences and Applications, 2002
    Co-Authors: H.m. Liebich, Claudia Först

    Abstract:

    Abstract Hydroxy- and oxomonocarboxylic Acids in urine of healthy individuals and of patients with diabetic ketoAcidosis are analysed as methyl esters and methyl esters/O-methyloximes, respectively, by gas chromatography and gas chromatography-mass spectrometry. The derivatives are pre-fractionated by thin-layer chromatography. The Acids originate mainly from ketogenesis and from the metabolism of valine, leucine and isoleucine. The amino Acid metabolites fall into three groups: the 2-oxocarboxylic Acids (2-oxoisovaleric Acid, 2Oxoisocaproic Acid and 2-oxo-3-methylvaleric Acid); the 2-hydroxycarboxylic Acids (2-hydroxyisovaleric Acid, 2-hydroxyisocaproic Acid and 2-hydroxy-3-methylvaleric Acid); and the 3-hydroxycarboxylic Acids (3-hydroxyisobutyric Acid, 3-hydroxyisovaleric Acid, 3-hydroxy-2-ethylpropionic Acid, threo -3-hydroxy-2– methylbutyric Acid and erythro -3-hydroxy-2-methylbutyric Acid). The threo form of 3- hydroxy-2-methylbutyric Acid is the major constituent within the diastereomeric pair. Of the three groups of amino Acid metabolites, the 3-hydroxycarboxylic Acids in particular are elevated during ketoAcidosis. The characteristic general features of the mass spectrometric fragmentation of the derivatives of the identified components are systematically described. The discussion of the fragmentation includes constituents of low concentrations, such as 3-oxocaproic Acid, 4-oxo-butyric Acid and 5-oxocaproic Acid, which can be detected only when the pre-fractionation technique is applied.