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- Boucher, A, et al.
(författare)
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Biochemical mechanism of lipid-induced impairment of glucose-stimulated insulin secretion and reversal with a malate analogue
- 2004
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 279:26, s. 27263-27271
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Tidskriftsartikel (refereegranskat)abstract
- Hyperlipidemia appears to play an integral role in loss of glucose-stimulated insulin secretion (GSIS) in type 2 diabetes. This impairment can be simulated in vitro by chronic culture of 832/13 insulinoma cells with high concentrations of free fatty acids, or by study of lipid-laden islets from Zucker diabetic fatty rats. Here we show that impaired GSIS is not a simple result of saturation of lipid storage pathways, as adenovirus-mediated overexpression of a cytosolically localized variant of malonyl-CoA decarboxylase in either cellular model results in dramatic lowering of cellular triglyceride stores but no improvement in GSIS. Instead, the glucose-induced increment in "pyruvate cycling" activity ( pyruvate exchange with tricarboxylic acid cycle intermediates measured by C-13 NMR), previously shown to play an important role in GSIS, is completely ablated in concert with profound suppression of GSIS in lipid-cultured 832/13 cells, whereas glucose oxidation is unaffected. Moreover, GSIS is partially restored in both lipid-cultured 832/13 cells and islets from Zucker diabetic fatty rats by addition of a membrane permeant ester of a pyruvate cycling intermediate ( dimethyl malate). We conclude that chronic exposure of islet beta-cells to fatty acids grossly alters a mitochondrial pathway of pyruvate metabolism that is important for normal GSIS.
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| 3. |
- Grimm, C. H., et al.
(författare)
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Selective extraction of small proteins from biological samples using a novel restricted access column with cation exchange properties
- 2000
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Ingår i: Chromatographia. - 0009-5893. ; 52:11-12, s. 703-709
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Tidskriftsartikel (refereegranskat)abstract
- The determination of proteins utilising a polymer-based restricted access support material with ion exchange properties (IERAM) is outlined. Solid phase extraction coupled on-line with a microbore reversed phase HPLC system for the quantitation of small marker proteins is demonstrated. The cation-exchange restricted access packings were characterised with respect to their adsorption and desorption kinetics. The IERAM material was also investigated by capacity, selectivity, and biocompatibility determinations when applied to the quantification of small molecular weight proteins such as cytochrome C, Lysozyme, Ribonuclease A, Myoglobin, Insulin, human serum albumin, and a Tryptic inhibitor. The integrated system was coupled to mass identity of selected proteins by MALDI-TOF mass spectrometry. The chromatographic outlet was interfaced to an "Interplate" fractionation collecter that sampled 1 μL volumes directly onto the MALDI target plate. The fully automated coupled column system was run unattended overnight and applied to protein quantitations in human plasma samples. Recovery data for a selected number of proteins varied between 90-96% (n = 10) with a limit of quantification around 2 μM with an injection volume of 100 μL. The RSD data were typically less than 8% at a 50 μM protein level (n = 7).
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