Brown adipose tissue activity controls triglyceride clearance

Brown adipose tissue (BAT) burns fatty acids for heat production to defend the body against cold and has recently been shown to be present in humans. Triglyceride-rich lipoproteins (TRLs) transport lipids in the bloodstream, where the fatty acid moieties are liberated by the action of lipoprotein lipase (LPL). Peripheral organs such as muscle and adipose tissue take up the fatty acids, whereas the remaining cholesterol-rich remnant particles are cleared by the liver. Elevated plasma triglyceride concentrations and prolonged circulation of cholesterol-rich remnants, especially in diabetic dyslipidemia, are risk factors for cardiovascular disease. However, the precise biological role of BAT for TRL clearance remains unclear. Here we show that increased BAT activity induced by short-term cold exposure controls TRL metabolism in mice. Cold exposure drastically accelerated plasma clearance of triglycerides as a result of increased uptake into BAT, a process crucially dependent on local LPL activity and transmembrane receptor CD36. In pathophysiological settings, cold exposure corrected hyperlipidemia and improved deleterious effects of insulin resistance. In conclusion, BAT activity controls vascular lipoprotein homeostasis by inducing a metabolic program that boosts TRL turnover and channels lipids into BAT. Activation of BAT might be a therapeutic approach to reduce elevated triglyceride concentrations and combat obesity in humans.     

Report from the second cytomegalovirus and immunosenescence workshop

The Second International Workshop on CMV & Immunosenescence was held in Cambridge, UK, 2-4th December, 2010. The presentations covered four separate sessions: cytomegalovirus and T cell phenotypes; T cell memory frequency, inflation and immunosenescence; cytomegalovirus in aging, mortality and disease states; and the immunobiology of cytomegalovirus-specific T cells and effects of the virus on vaccination. This commentary summarizes the major findings of these presentations and references subsequently published work from the presenter laboratory where appropriate and draws together major themes that were subsequently discussed along with new areas of interest that were highlighted by this discussion.     

Unbiased screening of polymer libraries to define novel substrates for functional hepatocytes with inducible drug metabolism

Maintaining stable differentiated somatic cell function in culture is essential to a range of biological endeavors. However, current technologies, employing, for example, primary hepatic cell culture (essential to the development of a bio-artificial liver and improved drug and toxicology testing), are limited by supply, expense, and functional instability even on biological cell culture substrata. As such, novel biologically active substrates manufacturable to GMP standards have the potential to improve cell culture-based assay applications. Currently hepatic endoderm (HE) generated from pluripotent stem cells is a genotypically diverse, cheap, and stable source of "hepatocytes"; however, HE routine applications are limited due to phenotypic instability in culture. Therefore a manufacturable subcellular matrix capable of supporting long-term differentiated cell function would represent a step forward in developing scalable and phenotypically stable hESC-derived hepatocytes. Adopting an unbiased approach we screened polymer microarrays and identified a polyurethane matrix which promoted HE viability, hepatocellular gene expression, drug-inducible metabolism, and function. Moreover, the polyurethane supported, when coated on a clinically approved bio-artificial liver matrix, long-term hepatocyte function and growth. In conclusion, our data suggest that an unbiased screening approach can identify cell culture substrate(s) that enhance the phenotypic stability of primary and stem cell-derived cell resources.     

Fabrication of synthetic polymer coatings and their use in feeder-free culture of human embryonic stem cells

The culture of human embryonic stem (hES) cells in defined and xenogeneic-free conditions will contribute substantially to future biotechnological and medical applications. To achieve this goal, we developed the first fully defined synthetic polymer coating poly[2-(methacryloyloxy)ethyl dimethyl-(3-sulfopropyl)ammonium hydroxide] (PMEDSAH) that sustains long-term growth of hES cells in different culture media. Here we describe a detailed protocol for the reproducible fabrication of PMEDSAH coating on tissue culture polystyrene dishes, and for the feeder-free culture of hES cells on PMEDSAH coating in defined culture medium. This culture system represents a key step toward the fully defined and xenogeneic-free culture of hES cells.     

Plasma beta carotene in Alzheimer's disease. Association with cerebrospinal fluid beta-amyloid 1-40, (Abeta40), beta-amyloid 1-42 (Abeta42) and total Tau

We studied the plasma beta carotene concentrations in 40 Alzheimer's disease patients and the association with cerebrospinal fluid beta-amyloid 1-40, (Abeta40), cerebrospinal fluid beta-amyloid 1-42 (Abeta42) and cerebrospinal fluid total Tau. We found that patients with plasma beta carotene levels below the 25th percentile had 55% reduced ratios of Abeta40/Tau and 51% reduced ratios of Abeta 40/Abeta 42 compared with patients in the highest quartile. Mean Tau concentrations in the lowest quartile of plasma beta-carotene levels were 74% higher compared with the highest quartile of plasma beta-carotene levels. Thus, we could demonstrate an statistically significant association between beta carotene levels in plasma and neurochemical markers in the cerebrospinal fluid of Alzheimer's disease patients.     

Poly(oxazoline)s with telechelic antimicrobial functions

Poly(2-alkyl-1,3-oxazoline)s (alkyl = methyl, ethyl) with terminal quarternary ammonium groups were synthesized. It could be shown by NMR and ESI-MS that the termination of the living polymerization with N,N-dimethylalkyl(butyl to hexadecyl)amines was quantitative. The novel functions were investigated regarding their antimicrobial potential toward the bacterium Staphylococcus aureus revealing that only quarternary ammonium functions with 12 and more carbons are antibacterial. Using a novel bifunctional initiator, 3-[(tert-butoxycarbonyl)amino]benzyl-p-toluenesulfonate, poly(oxazoline) with a primary amino group at the starting end and an antimicrobial function at the terminal could be synthesized, as confirmed by NMR and ESI-MS measurements. Comparing the bioactivity of polymers with different functions at the starting end and terminated with dimethyldodecylamine revealed that the starting group has a great effect on the antibacterial properties of the distant terminal. The minimal inhibitory concentrations varied from 0.1 mM for polymer derivatives with a BOC-NH-phenyl starting group to 4 mM for poly(oxazoline)s with a free primary amine at the starting end.     

State-of-the-art in phosphoproteomics

Presently, phosphorylation of proteins is the most studied and best understood PTM. However, the analysis of phosphoproteins and phosphopeptides is still one of the most challenging tasks in contemporary proteome research. Since not every phosphoprotein is accessible by a certain method and identification of the phosphorylated amino acid residue is required in the majority of cases, various strategies for the detection and localization of phosphorylations have been developed. Identification and localization of protein phosphorylations is mostly done by MS nowadays but phosphoproteins and -peptides are often suppressed in comparison to the unphosphorylated species if measured in complex mixtures. Thus, the isolation of pure phosphopeptide samples is a main task. This review gives an overview over the most frequently used methods in isolation and detection of phosphoproteins and -peptides such as specific enrichment or separation strategies as well as the localization of the phosphorylated residues by various mass spectrometric techniques.