High fat diet-induced modifications in membrane lipid and mitochondrial-membrane protein signatures precede the development of hepatic insulin resistance in mice.

OBJECTIVE: Excess lipid intake has been implicated in the pathophysiology of hepatosteatosis and hepatic insulin resistance. Lipids constitute approximately 50% of the cell membrane mass, define membrane properties, and create microenvironments for membrane-proteins. In this study we aimed to resolve temporal alterations in membrane metabolite and protein signatures during high-fat diet (HF)-mediated development of hepatic insulin resistance. METHODS: We induced hepatosteatosis by feeding C3HeB/FeJ male mice an HF enriched with long-chain polyunsaturated C18:2n6 fatty acids for 7, 14, or 21 days. Longitudinal changes in hepatic insulin sensitivity were assessed via the euglycemic-hyperinsulinemic clamp, in membrane lipids via t-metabolomics- and membrane proteins via quantitative proteomics-analyses, and in hepatocyte morphology via electron microscopy. Data were compared to those of age- and litter-matched controls maintained on a low-fat diet. RESULTS: Excess long-chain polyunsaturated C18:2n6 intake for 7 days did not compromise hepatic insulin sensitivity, however, induced hepatosteatosis and modified major membrane lipid constituent signatures in liver, e.g. increased total unsaturated, long-chain fatty acid-containing acyl-carnitine or membrane-associated diacylglycerol moieties and decreased total short-chain acyl-carnitines, glycerophosphocholines, lysophosphatidylcholines, or sphingolipids. Hepatic insulin sensitivity tended to decrease within 14 days HF-exposure. Overt hepatic insulin resistance developed until day 21 of HF-intervention and was accompanied by morphological mitochondrial abnormalities and indications for oxidative stress in liver. HF-feeding progressively decreased the abundance of protein-components of all mitochondrial respiratory chain complexes, inner and outer mitochondrial membrane substrate transporters independent from the hepatocellular mitochondrial volume in liver. CONCLUSIONS: We assume HF-induced modifications in membrane lipid- and protein-signatures prior to and during changes in hepatic insulin action in liver alter membrane properties - in particular those of mitochondria which are highly abundant in hepatocytes. In turn, a progressive decrease in the abundance of mitochondrial membrane proteins throughout HF-exposure likely impacts on mitochondrial energy metabolism, substrate exchange across mitochondrial membranes, contributes to oxidative stress, mitochondrial damage, and the development of insulin resistance in liver.

Mesenchymal stem cell (MSC) and endothelial progenitor cell (EPC) growth and adhesion in six different bone graft substitutes.

INTRODUCTION: Several different synthetic and allograft bone graft substitutes are used clinically to treat large bone defects. In contrast to the "gold standard" of autologous bone grafts, these do not contain bone-forming (MSC) or vessel-forming (EPC) cells. In order to achieve the same level of success enjoyed by autologous bone grafts, they must be compatible with mesenchymal stem cells (MSC) and endothelial progenitor cells (EPC). In a previous study, we seeded MSC onto six different bone graft substitutes and then measured the cell adhesion, viability, differentiation, and morphology. In the present study, we seeded both MSC and EPC onto the same six bone graft substitutes and measured the same parameters. METHODS: In vitro, 125,000 MSC and 125,000 EPC were seeded onto Chronos(®), Vitoss(®), Actifuse(®), Biobase(®), Cerabone(®), and Tutoplast(®). Cell adhesion (fluorescence microscopy) and viability (MTT assay) were measured on days 2, 6, and 10. Osteogenic (cbfa-1, alkaline phosphatase [ALP], osteocalcin, collagen-1 alpha [Col1A]) and endothelial (von Willebrand factor [vWF], vascular endothelial growth factor [VEGF], kinase domain receptor [KDR]) gene expression were analyzed by reverse transcriptase polymerase chain reaction (RT-PCR). Morphology was described by scanning electron microscopy (SEM) at day 2. RESULTS: MSC adhered significantly better to Tutoplast(®), Chronos(®), Actifuse(®), and Biobase(®). EPC adhered better to Actifuse(®), Chronos(®), Biobase(®), and Tutoplast(®). Viability increased over time when seeded on Tutoplast(®) and Chronos(®). Osteogenic and endothelial gene expression were detectable at day 10 in cells seeded on Chronos(®), Actifuse(®), and Tutoplast(®). The best morphology of MSC and EPC was found on Tutoplast(®), Chronos(®), Actifuse(®), and Biobase(®). CONCLUSION: When bone graft substitutes are used to help fill large defects, it is important that their interaction with these cells be supportive of bone healing.

Determination of aldehydes in food by high-performance liquid chromatography with biosensor coupling and micromembrane suppressors.

A high-performance liquid chromatography system for the determination of aldehydes in food was developed incorporating an Cation MicroMembrane Suppressor (CMMS) and enzyme reactors packed with VA-Epoxy on which aldehyde dehydrogenase from bakers yeast and NADH oxidase from Bacillus licheniformis were immobilized. The method was based on the principle that the separation efficiency of HPLC is combined with the sensitivity of electrochemical detection and the specificity of enzymes. Main attention was directed to the determination of 5-hydroxymethyl-2-furaldehyde and 2-furaldehyde, the occurrence of which is an indication of quality deterioration in several food products. The efficiency of the method has been shown by the analysis of honey, coffee and related beverages, refreshments, sherry, port, dry fruits and breakfast cereals.

Solution structure of the DNA-binding domain of the tomato heat-stress transcription factor HSF24.

Two-dimensional-NMR and three-dimensional-NMR experiments were performed to determine the solution structure of the DNA-binding domain of the tomato heat-stress transcription factor HSF24. Samples of uniformly 15N-labeled and 15N, 13C-labeled recombinant proteins were used in the investigation. A near-complete assignment of the backbone 1H, 15N, and 13C resonances was obtained by three-dimensional triple-resonance experiments, whereas three-dimensional 15N-TOCSY-heteronuclear-single-quantum-correlation-spectroscopy, HCCH-COSY and HCCH-TOCSY spectra were recorded for side-chain assignments, 885 non-redundant distance constraints from two-dimensional-homonuclear and three-dimensional-15N-edited and 13C-edited NOESY spectra and 40 hydrogen-bond constraints from exchange experiments were used for structure calculations. The resulting three-dimensional structure contains a three-helix bundle and a small four-stranded antiparallel beta-sheet that forms a hydrophobic core. The two C-terminal helices are parts of a highly conserved helix-turn-helix motif that is probably involved in DNA recognition and binding. In contrast to heat-stress factors from yeast and animals, the plant heat-stress factors lack a loop of 11 amino acid residues inserted between beta3 and beta4. This leads to a tight turn between these beta-strands.