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Metabolic Precursor (metabolic + precursor)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Phytanic Acid Accumulation Is Associated with Conduction Delay and Sudden Cardiac Death in Sterol Carrier Protein-2/Sterol Carrier Protein-x Deficient Mice

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2004
GEROLD MÖNNIG M.D.
Introduction: The sterol carrier protein-2 gene encodes two functionally distinct proteins: sterol carrier protein-2 (SCP2, a peroxisomal lipid carrier) and sterol carrier protein-x (SCPx, a peroxisomal thiolase known as peroxisomal thiolase-2), which is involved in peroxisomal metabolism of bile acids and branched-chain fatty acids. We show in this study that mice deficient in SCP2 and SCPx (SCP2null) develop a cardiac phenotype leading to a high sudden cardiac death rate if mice are maintained on diets enriched for phytol (a metabolic precursor of branched-chain fatty acids). Methods and Results: In 210 surface and 305 telemetric ECGs recorded in wild-type (C57BL/6; wt; n = 40) and SCP2 null mice (n = 40), no difference was observed at baseline. However, on diet, cycle lengths were prolonged in SCP2 null mice (262.9 ± 190 vs 146.3 ± 43 msec), AV conduction was prolonged (58.3 ± 17 vs 42.6 ± 4 ms), and QRS complexes were wider (19.1 ± 5 vs 14.0 ± 4 ms). In 11 gene-targeted Langendorff-perfused hearts isolated from SCP2 null mice after dietary challenge, complete AV blocks (n = 5/11) or impaired AV conduction (Wenckebach point 132 ± 27 vs 92 ± 10 msec; P < 0.05) could be confirmed. Monophasic action potentials were not different between the two genotypes. Left ventricular function studied by echocardiography was similar in both strains. Phytanic acid but not pristanic acid accumulated in the phospholipid fraction of myocardial membranes isolated from SCP2 null mice. Conclusion: Accumulation of phytanic acid in myocardial phospholipid membranes is associated with bradycardia and impaired AV nodal and intraventricular impulse conduction, which could provide an explanation for sudden cardiac death in this model. [source]

Profiling human gut bacterial metabolism and its kinetics using [U- 13C]glucose and NMR

NMR IN BIOMEDICINE, Issue 1 2010
Albert A. de Graaf
Abstract This study introduces a stable-isotope metabolic approach employing [U- 13C]glucose that, as a novelty, allows selective profiling of the human intestinal microbial metabolic products of carbohydrate food components, as well as the measurement of the kinetics of their formation pathways, in a single experiment. A well-established, validated in vitro model of human intestinal fermentation was inoculated with standardized gastrointestinal microbiota from volunteers. After culture stabilization, [U- 13C]glucose was added as an isotopically labeled metabolic precursor. System lumen and dialysate samples were taken at regular intervals. Metabolite concentrations and isotopic labeling were determined by NMR, GC, and enzymatic methods. The main microbial metabolites were lactate, acetate, butyrate, formate, ethanol, and glycerol. They together accounted for a 13C recovery rate as high as 91.2%. Using an NMR chemical shift prediction approach, several minor products that showed 13C incorporation were identified as organic acids, amino acids, and various alcohols. Using computer modeling of the 12C contents and 13C labeling kinetics, the metabolic fluxes in the gut microbial pathways for synthesis of lactate, formate, acetate, and butyrate were determined separately for glucose and unlabeled background substrates. This novel approach enables the study of the modulation of human intestinal function by single nutrients, providing a new rational basis for achieving control of the short-chain fatty acids profile by manipulating substrate and microbiota composition in a purposeful manner. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Tailoring 13C labeling for triple-resonance solid-state NMR experiments on aligned samples of proteins

MAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2007
Neeraj Sinha
Abstract In order to develop triple-resonance solid-state NMR spectroscopy of membrane proteins, we have implemented several different 13C labeling schemes with the purpose of overcoming the interfering effects of 13C13C dipole,dipole couplings in stationary samples. The membrane-bound form of the major coat protein of the filamentous bacteriophage Pf1 was used as an example of a well-characterized helical membrane protein. Aligned protein samples randomly enriched to 35% 13C in all sites and metabolically labeled from bacterial growth on media containing [2- 13C]-glycerol or [1,3- 13C]-glycerol enables direct 13C detection in solid-state NMR experiments without the need for homonuclear 13C13C dipole,dipole decoupling. The 13C-detected NMR spectra of Pf1 coat protein show a substantial increase in sensitivity compared to the equivalent 15N-detected spectra. The isotopic labeling pattern was analyzed for [2- 13C]-glycerol and [1,3- 13C]-glycerol as metabolic precursors by solution-state NMR of micelle samples. Polarization inversion spin exchange at the magic angle (PISEMA) and other solid-state NMR experiments work well on 35% random fractionally and metabolically tailored 13C-labeled samples, in contrast to their failure with conventional 100% uniformly 13C-labeled samples. Copyright © 2007 John Wiley & Sons, Ltd. [source]

A noninvasive technique for the measurement of the energetic state of free-suspension mammalian cells

BIOTECHNOLOGY PROGRESS, Issue 2 2010
M. Ben-Tchavtchavadze
Abstract A perfusion small-scale bioreactor allowing on-line monitoring of the cell energetic state was developed for free-suspension mammalian cells. The bioreactor was designed to perform in vivo nuclear magnetic resonance (NMR) spectroscopy, which is a noninvasive and nondestructive method that permits the monitoring of intracellular nutrient concentrations, metabolic precursors and intermediates, as well as metabolites and energy shuttles, such as ATP, ADP, and NADPH. The bioreactor was made of a 10-mm NMR tube following a fluidized bed design. Perfusion flow rate allowing for adequate oxygen supply was found to be above 0.79 mL min,1 for high-density cell suspensions (108 cells). Chinese hamster ovary (CHO) cells were studied here as model system. Hydrodynamic studies using coloration/decoloration and residence time distribution measurements were realized to perfect bioreactor design as well as to determine operating conditions bestowing adequate homogeneous mixing and cell retention in the NMR reading zone. In vivo 31P NMR was performed and demonstrated the small-scale bioreactor platform ability to monitor the cell physiological behavior for 30-min experiments. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source]