Thermodynamic phase diagram of Fe(Se0.5Te0.5) single crystals in fields up to 28 tesla

International audienceWe report on specific heat Cp , transport, Hall probe, and penetration depth measurements performed on Fe Se0.5Te0.5 single crystals Tc 14 K . The thermodynamic upper critical field Hc2 lines has been deduced from Cp measurements up to 28 T for both H c and H ab, and compared to the lines deduced from transport measurements up to 55 T in pulsed magnetic fields . We show that this thermodynamic Hc2 line presents a very strong downward curvature for T→Tc which is not visible in transport measurements. This temperature dependence associated to an upward curvature of the field dependence of the Sommerfeld coefficient confirms that Hc2 is limited by paramagnetic effects. Surprisingly this paramagnetic limit is visible here up to T/Tc 0.99 for H ab which is the consequence of a very small value of the coherence length c 0 4 Å and ab 0 15 Å , confirming the strong renormalization of the effective mass as compared to DMFT calculations previously observed in ARPES measurements A. Tamai, A. Y. Ganin, E. Rozbicki, J. Bacsa, W. Meevasana, P. D. C. King, M. Caffio, R. Schaub, S. Margadonna, K. Prassides, M. J. Rosseinsky, and F. Baumberger, Phys. Rev. Lett. 104, 097002 2010 . Hc1 measurements lead to ab 0 =430 50 nm and c 0 =1600 200 nm and the corresponding anisotropy is approximatively temperature independent 4 , being close to the anisotropy of Hc2 for T→Tc. The temperature dependence of both T2 and the electronic contribution to the specific heat confirm the nonconventional coupling mechanism in this system

Effect of the isoelectronic substitution of Sb for As on the magnetic and structural properties of LaFe(As1−xSbx)O

International audienceThe antiferromagnetic (AFM) order and structural distortion in the LaFe(As1−xSbx)O system have been investigated by neutron powder diffraction and physical properties measurements. Polycrystalline samples of LaFe(As1−xSbx)O (x < 0.5) were prepared using solid state synthesis at ambient and high pressure. We find that the isoelectronic substitution of Sb for As decreases the structural and magnetic transition temperatures, but, contrary to the effects of phosphorus substitution, superconductivity is not induced. Instead a slight increase in the Fe-magnetic moment is observed

Novel nanostructured lipid carriers dedicated to nucleic acid delivery for RNAi purposes

International audienceThe specific down-regulation triggered through interference RNA (RNAi) provides a means to determine the gene functions and their contributions in an altered phenotype. In this way, high throughput screening (HTS) has emerged as a potent automated tool to study a large number of genes for identification of new biomarkers and therapeutic targets. However, the siRNA-mediated gene knock down requires that siRNA can reach cytoplasm compartment where RNAi occurs. Unfortunately, the siRNA is relatively vulnerable in the extracellular environment due to the presence of degradation enzymes and its high molecular weight associated to its anionic charge limit considerably its cell incorporation across the plasma membrane. Thereby, HTS requires generic carriers with highly efficient siRNA transfection. To overcome these obstacles, multifunctional nanoparticles comprising an imaging contrast agent are emerging as an original and promising approach in the improved, controlled and monitored delivery of siRNA

Intestinal mucosal adherence and translocation of commensal bacteria at the early onset of type 2 diabetes: molecular mechanisms and probiotic treatment

A fat-enriched diet modifies intestinal microbiota and initiates a low-grade inflammation, insulin resistance and type-2 diabetes. Here, we demonstrate that before the onset of diabetes, after only one week of a high-fat diet (HFD), live commensal intestinal bacteria are present in large numbers in the adipose tissue and the blood where they can induce inflammation. This translocation is prevented in mice lacking the microbial pattern recognition receptors Nod1 or CD14, but overtly increased in Myd88 knockout and ob/ob mouse. This ‘metabolic bacteremia’ is characterized by an increased co-localization with dendritic cells from the intestinal lamina propria and by an augmented intestinal mucosal adherence of non-pathogenic Escherichia coli. The bacterial translocation process from intestine towards tissue can be reversed by six weeks of treatment with the probiotic strain Bifidobacterium animalis subsp. lactis 420, which improves the animals' overall inflammatory and metabolic status. Altogether, these data demonstrate that the early onset of HFD-induced hyperglycemia is characterized by an increased bacterial translocation from intestine towards tissues, fuelling a continuous metabolic bacteremia, which could represent new therapeutic targets

Metabolism

Background: Cardiovascular disease is the leading cause of deaths in nonalcoholic steatohepatitis (NASH) patients. Mouse models, while widely used for drug development, do not fully replicate human NASH nor integrate the associated cardiac dysfunction, i.e. heart failure with preserved ejection fraction (HFpEF). To overcome these limitations, we established a nutritional hamster model developing both NASH and HFpEF. We then evaluated the effects of the dual peroxisome proliferator activated receptor alpha/delta agonist elafibranor developed for the treatment of NASH patients. Methods: Male Golden Syrian hamsters were fed for 10 to 20 weeks with a free choice diet, which presents hamsters with a choice between control chow diet with normal drinking water or a high fat/high cholesterol diet with 10% fructose enriched drinking water. Biochemistry, histology and echocardiography analysis were performed to characterize NASH and HFpEF. Once the model was validated, elafibranor was evaluated at 15 mg/kg/day orally QD for 5 weeks. Results: Hamsters fed a free choice diet for up to 20 weeks developed NASH, including hepatocyte ballooning (as confirmed with cytokeratin-18 immunostaining), bridging fibrosis, and a severe diastolic dysfunction with restrictive profile, but preserved ejection fraction. Elafibranor resolved NASH, with significant reduction in ballooning and fibrosis scores, and improved diastolic dysfunction with significant reduction in E/A and E/E' ratios. Conclusion: Our data demonstrate that the free choice diet induced NASH hamster model replicates the human phenotype and will be useful for validating novel drug candidates for the treatment of NASH and associated HfpEF

The Hepatic Compensatory Response to Elevated Systemic Sulfide Promotes Diabetes

Impaired hepatic glucose and lipid metabolism are hallmarks of type 2 diabetes. Increased sulfide production or sulfide donor compounds may beneficially regulate hepatic metabolism. Disposal of sulfide through the sulfide oxidation pathway (SOP) is critical for maintaining sulfide within a safe physiological range. We show that mice lacking the liver- enriched mitochondrial SOP enzyme thiosulfate sulfurtransferase (Tst−/− mice) exhibit high circulating sulfide, increased gluconeogenesis, hypertriglyceridemia, and fatty liver. Unexpectedly, hepatic sulfide levels are normal in Tst−/− mice because of exaggerated induction of sulfide disposal, with associated suppression of global protein persulfidation and nuclear respiratory factor 2 target protein levels. Hepatic proteomic and persulfidomic profiles converge on gluconeogenesis and lipid metabolism, revealing a selective deficit in medium-chain fatty acid oxidation in Tst−/− mice. We reveal a critical role of TST in hepatic metabolism that has implications for sulfide donor strategies in the context of metabolic disease

Dendritic cells are defective in breast cancer patients: a potential role for polyamine in this immunodeficiency

INTRODUCTION: Dendritic cells (DCs) are antigen-presenting cells that are currently employed in cancer clinical trials. However, it is not clear whether their ability to induce tumour-specific immune responses when they are isolated from cancer patients is reduced relative to their ability in vivo. We determined the phenotype and functional activity of DCs from cancer patients and investigated the effect of putrescine, a polyamine molecule that is released in large amounts by cancer cells and has been implicated in metastatic invasion, on DCs. METHODS: The IL-4/GM-CSF (granulocyte–macrophage colony-stimulating factor) procedure for culturing blood monocyte-derived DCs was applied to cells from healthy donors and patients (17 with breast, 7 with colorectal and 10 with renal cell carcinoma). The same peroxide-treated tumour cells (M74 cell line) were used for DC pulsing. We investigated the effects of stimulation of autologous lymphocytes by DCs pulsed with treated tumour cells (DC-Tu), and cytolytic activity of T cells was determined in the same target cells. RESULTS: Certain differences were observed between donors and breast cancer patients. The yield of DCs was dramatically weaker, and expression of MHC class II was lower and the percentage of HLA-DR(-)Lin(- )cells higher in patients. Whatever combination of maturating agents was used, expression of markers of mature DCs was significantly lower in patients. Also, DCs from patients exhibited reduced ability to stimulate cytotoxic T lymphocytes. After DC-Tu stimulation, specific cytolytic activity was enhanced by up to 40% when DCs were from donors but only up to 10% when they were from patients. IFN-γ production was repeatedly found to be enhanced in donors but not in patients. By adding putrescine to DCs from donors, it was possible to enhance the HLA-DR(-)Lin(- )cell percentage and to reduce the final cytolytic activity of lymphocytes after DC-Tu stimulation, mimicking defective DC function. These putrescine-induced deficiencies were reversed by treating DCs with all-trans retinoic acid. CONCLUSION: These data are consistent with blockade of antigen-presenting cells at an early stage of differentiation in patients with breast cancer. Putrescine released in the microenvironmement of DCs could be involved in this blockade. Use of all-trans retinoic acid treatment to reverse this blockade and favour ex vivo expansion of antigen-specific T lymphocytes is of real interest

Sitagliptin promotes macrophage-to-faeces reverse cholesterol transport through reduced intestinal cholesterol absorption in obese insulin resistant CETP-apoB100 transgenic mice.

International audienceDipeptidyl peptidase-4 inhibitors (DPP-4i) improve glycaemic control in type 2 diabetes, but their benefits on reverse cholesterol transport (RCT) remain unknown. We evaluated the effects of DPP-4i sitagliptin 500 mg/kg/day on RCT in obese insulin-resistant CETP-apoB100 transgenic mice. Metformin 300 mg/kg/day orally was used as a reference compound. Both metformin and sitagliptin showed the expected effects on glucose parameters. Although no significant effect was observed on total cholesterol and high-density lipoprotein (HDL) cholesterol levels, sitagliptin, but not metformin, increased faecal cholesterol mass excretion by 132% (p < 0.001 vs. vehicle), suggesting a potent effect on cholesterol metabolism. Mice were then injected i.p. with (3) H-cholesterol labelled macrophages to measure RCT over 48 h. Compared with vehicle, sitagliptin significantly increased macrophage-derived (3) H-cholesterol faecal excretion by 39%. Administration of (14) C-cholesterol labelled olive oil orally showed a significant reduction of (14) C-tracer plasma appearance over time with sitagliptin, indicating that this drug promotes RCT through reduced intestinal cholesterol absorption

Deletion of apoptosis signal-regulating kinase 1 (ASK1) protects pancreatic beta-cells from stress-induced death but not from glucose homeostasis alterations under pro-inflammatory conditions.

BACKGROUND:Type 2 diabetes is characterized by pancreatic beta-cell dysfunction and is associated with low-grade inflammation. Recent observations suggest that apoptosis signal-regulating kinase 1 (ASK1) is involved in beta-cell death in response to different stressors. In this study, we tested whether ASK1 deficiency protects beta-cells from glucolipotoxic conditions and cytokines treatment or from glucose homeostasis alteration induced by endotoxemia. METHODOLOGY/PRINCIPAL FINDINGS:Insulin secretion was neither affected upon shRNA-mediated downregulation of ASK1 in MIN6 cells nor in islets from ASK1-deficient mice. ASK1 silencing in MIN6 cells and deletion in islets did not prevent the deleterious effect of glucolipotoxic conditions or cytokines on insulin secretion. However, it protected MIN6 cells from death induced by ER stress or palmitate and islets from short term caspase activation in response to cytokines. Moreover, endotoxemia induced by LPS infusion increased insulin secretion during hyperglycemic clamps but the response was similar in wild-type and ASK1-deficient mice. Finally, insulin sensitivity in the presence of LPS was not affected by ASK1-deficiency. CONCLUSIONS/SIGNIFICANCE:Our study demonstrates that ASK1 is not involved in beta-cell function and dysfunction but controls stress-induced beta-cell death

A Bayesian implementation of quality-by-design for the development of cationic nano-lipid for siRNA transfection

International audienceUnlike Quality by Testing approach, where products were tested only after drug manufacturing, Quality by Design (QbD) is a proactive control quality paradigm, which handles risks from the early development steps. In QbD, regression models built from experimental data are used to predict a risk mapping called Design Space in which the developers can identify values of critical input factors leading to acceptable probabilities to meet the efficacy and safety specifications for the expected product. These empirical models are often limited to quantitative responses. Moreover, in practice the smallness and incompleteness of datasets degrade the quality of predictions. In this study, a Bayesian approach including variable selection, parameter estimation and model quality assessment is proposed and assessed using a real case study devoted to the development of a Cationic Nano-Lipid Structures for siRNA Transfection. Two original model structures are also included to describe both binary and percentage response variables. The results confirm the practical relevance and applicability of the Bayesian implementation of the QbD analysis