Relativistically rotating dust

Dust configurations play an important role in astrophysics and are the simplest models for rotating bodies. The physical properties of the general--relativistic global solution for the rigidly rotating disk of dust, which has been found recently as the solution of a boundary value problem, are discussed.Comment: 18 pages, 11 figure

High levels of dietary stearate promote adiposity and deteriorate hepatic insulin sensitivity

<p>Abstract</p> <p>Background</p> <p>Relatively little is known about the role of specific saturated fatty acids in the development of high fat diet induced obesity and insulin resistance. Here, we have studied the effect of stearate in high fat diets (45% energy as fat) on whole body energy metabolism and tissue specific insulin sensitivity.</p> <p>Methods</p> <p>C57Bl/6 mice were fed a low stearate diet based on palm oil or one of two stearate rich diets, one diet based on lard and one diet based on palm oil supplemented with tristearin (to the stearate level of the lard based diet), for a period of 5 weeks. <it>Ad libitum </it>fed Oxidative metabolism was assessed by indirect calorimetry at week 5. Changes in body mass and composition was assessed by DEXA scan analysis. Tissue specific insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp analysis and Western blot at the end of week 5.</p> <p>Results</p> <p>Indirect calorimetry analysis revealed that high levels of dietary stearate resulted in lower caloric energy expenditure characterized by lower oxidation of fatty acids. In agreement with this metabolic phenotype, mice on the stearate rich diets gained more adipose tissue mass. Whole body and tissue specific insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp and analysis of insulin induced PKB^ser473phosphorylation. Whole body insulin sensitivity was decreased by all high fat diets. However, while insulin-stimulated glucose uptake by peripheral tissues was impaired by all high fat diets, hepatic insulin sensitivity was affected only by the stearate rich diets. This tissue-specific pattern of reduced insulin sensitivity was confirmed by similar impairment in insulin-induced phosphorylation of PKB^ser473in both liver and skeletal muscle.</p> <p>Conclusion</p> <p>In C57Bl/6 mice, 5 weeks of a high fat diet rich in stearate induces a metabolic state favoring low oxidative metabolism, increased adiposity and whole body insulin resistance characterized by severe hepatic insulin resistance. These results indicate that dietary fatty acid composition <it>per sé </it>rather than dietary fat content determines insulin sensitivity in liver of high fat fed C57Bl/6 mice.</p

Antibody-based arrays in disease proteomics

In this review, we will describe the opportunities and challenges in proteomics as an approach to understand disease at the molecular level. The focus will be on why we require ‘open’ and ‘closed’ proteomics approaches and the important role protein arrays can play in a field that is leaning so heavily on mass spectrometry

Class I and IIa Histone Deacetylases Have Opposite Effects on Sclerostin Gene Regulation

Background: Gene regulation of the bone repressor sclerostin (SOST) is only poorly understood. Results: SOST gene suppression by PTH is partially mediated by HDAC5 inhibiting MEF2 and SOST gene expression requires class I HDAC activity. Conclusions: SOST gene expression is negatively regulated by HDAC5 and positively by class I HDACs. Significance: Class I HDAC inhibitors represent a novel approach for bone forming osteoporosis therapies

Activation of IGF1R/p110β/AKT/mTOR confers resistance to α-specific PI3K inhibition

The PI3K pathway is hyperactivated in many cancers, including 70% of breast cancers. Pan- and isoform-specific inhibitors of the PI3K pathway are currently being evaluated in clinical trials. However, the clinical responses to PI3K inhibitors when used as single agents are not as efficient as expected. In order to anticipate potential molecular mechanisms of resistance to the p110α isoform-selective inhibitor BYL719, we developed resistant breast cancer cell lines and assessed the concomitant changes in cellular signaling pathways using unbiased phosphotyrosine proteomics. We found an increase in IGF1R, IRS1/IRS2 and p85 phosphorylation in the resistant lines. Co-immunoprecipitation experiments identified an IGF1R/IRS/p85/p110β complex that causes the activation of AKT/mTOR/S6K and stifles the effects of BYL719. Pharmacological inhibition of members of this complex reduced mTOR/S6K activation and restored sensitivity to BYL719. Our study demonstrates that p110β confers resistance to BYL719 in PIK3CA mutant breast cancers. This provides a rationale for the combined targeting of p110α with IGF1R or p110β in patients with breast tumors harboring PIK3CA mutations

ANO1/TMEM16A interacts with EGFR and correlates with sensitivity to EGFR-targeting therapy in head and neck cancer

The epidermal growth factor receptor (EGFR) contributes to the pathogenesis of head&neck squamous cell carcinoma (HNSCC). However, only a subset of HNSCC patients benefit from anti-EGFR targeted therapy. By performing an unbiased proteomics screen, we found that the calcium-activated chloride channel ANO1 interacts with EGFR and facilitates EGFR-signaling in HNSCC. Using structural mutants of EGFR and ANO1 we identified the trans/juxtamembrane domain of EGFR to be critical for the interaction with ANO1. Our results show that ANO1 and EGFR form a functional complex that jointly regulates HNSCC cell proliferation. Expression of ANO1 affected EGFR stability, while EGFR-signaling elevated ANO1 protein levels, establishing a functional and regulatory link between ANO1 and EGFR. Co-inhibition of EGFR and ANO1 had an additive effect on HNSCC cell proliferation, suggesting that co-targeting of ANO1 and EGFR could enhance the clinical potential of EGFR-targeted therapy in HNSCC and might circumvent the development of resistance to single agent therapy. HNSCC cell lines with amplification and high expression of ANO1 showed enhanced sensitivity to Gefitinib, suggesting ANO1 overexpression as a predictive marker for the response to EGFR-targeting agents in HNSCC therapy. Taken together, our results introduce ANO1 as a promising target and/ or biomarker for EGFR-directed therapy in HNSCC

Apolipoprotein C3 deficiency results in diet-induced obesity and aggravated insulin resistance in mice

Our aim was to study whether the absence of apolipoprotein (apo) C3, a strong inhibitor of lipoprotein lipase (LPL), accelerates the development of obesity and consequently insulin resistance. Apoc3(-/-) mice and wild-type littermates were fed a high-fat (46 energy %) diet for 20 weeks. After 20 weeks of high-fat feeding, apoc3(-/-) mice showed decreased plasma triglyceride levels (0.11 +/- 0.02 vs. 0.29 +/- 0.04 mmol, P <0.05) and were more obese (42.8 +/- 3.2 vs. 35.2 +/- 3.3 g; P <0.05) compared with wild-type littermates. This increase in body weight was entirely explained by increased body lipid mass (16.2 +/- 5.9 vs. 10.0 +/- 1.8 g; P <0.05). LPL-dependent uptake of triglyceride-derived fatty acids by adipose tissue was significantly higher in apoc3(-/-) mice. LPL-independent uptake of albumin-bound fatty acids did not differ. It is interesting that whole-body insulin sensitivity using hyperinsulinemic-euglycemic clamps was decreased by 43% and that suppression of endogenous glucose production was decreased by 25% in apoc3(-/-) mice compared with control mice. Absence of apoC3, the natural LPL inhibitor, enhances fatty acid uptake from plasma triglycerides in adipose tissue, which leads to higher susceptibility to diet-induced obesity followed by more severe development of insulin resistance. Therefore, apoC3 is a potential target for treatment of obesity and insulin resistanc

Scalable production of full-length normal and mutant huntingtin in human cells and its biochemical characterization

Huntingtin (Htt) is a 350 kD intracellular protein, ubiquitously expressed and mainly localized in the cytoplasm. Huntington’s disease (HD) is caused by a CAG triplet amplification in exon 1 of the corresponding gene resulting in a polyglutamine (polyQ) expansion at the N-terminus of Htt. Production of full-length Htt has been difficult in the past and so far a scalable system or process has not been established for recombinant production of Htt in human cells. The ability to produce Htt in milligram quantities would be a prerequisite for many biochemical and biophysical studies aiming in a better understanding of Htt function under physiological conditions and in case of mutation and disease. For scalable production of full-length normal (17Q) and mutant (46Q and 128Q) Htt we have established two different systems, the first based on doxycycline-inducible Htt expression in stable cell lines, the second on “gutless” adenovirus mediated gene transfer. Purified material has then been used for biochemical characterization of full-length Htt. Posttranslational modifications (PTMs) were determined and several new phosphorylation sites were identified. Nearly all PTMs in full-length Htt localized to areas outside of predicted alpha-solenoid protein regions. In all detected N-terminal peptides methionine as the first amino acid was missing and the second, alanine, was found to be acetylated. Differences in secondary structure between normal and mutant Htt, a helix-rich protein, were not observed in our study. Purified Htt tends to form dimers and higher order oligomers, thus resembling the situation observed with N-terminal fragments, although the mechanism of oligomer formation may be different