Sar1b transgenic male mice are more susceptible to high-fat diet-induced obesity, insulin insensitivity and intestinal chylomicron overproduction

International audienceIn the intracellular secretory network, nascent proteins are shuttled from the endoplasmic reticulum to the Golgi by transport vesicles requiring Sar1b, a small GTPase. Mutations in this key enzyme impair intestinal lipid transport and cause chylomicron retention disease. The main aim of this study was to assess whether Sar1b overexpression under a hypercaloric diet accelerated lipid production and chylomicron (CM) secretion, thereby inducing cardiometabolic abnormalities. To this end, we generated transgenic mice overexpressing human Sar1b (Sar1b(+/+)) using pBROAD3-mcs that features the ubiquitous mouse ROSA26 promoter. In response to a high-fat diet (HFD), Sar1b(+/+) mice displayed significantly increased body weight and adiposity compared with Sar1b(+/+) mice under the same regimen or with wild-type (WT) mice exposed to chow diet or HFD. Furthermore, Sar1b(+/+) mice were prone to liver steatosis as revealed by significantly elevated hepatic triglycerides (TG) and cholesterol in comparison with WT animals. They also exhibited augmented levels of plasma TG along with alterations in fatty acid composition. Concomitantly, they showed susceptibility to develop insulin insensitivity and they responded abnormally to oral glucose tolerance test. Finally, Sar1b(+/+) mice that have been treated with Triton WR-1330 (to inhibit TG catabolism) and orotic acid (to block secretion of very low-density lipoprotein by the liver) responded more efficiently to fat meal tests as reflected by the rise in plasma TG and CM concentrations, indicating exaggerated intestinal fat absorption. These results suggest that Sar1b(+/+) under HFD can elicit cardiometabolic traits as revealed by incremental weight gain, fat deposition, dyslipidemia, hepatic steatosis, insulin insensitivity and intestinal fat absorption

Clay/phosphate-based ceramic materials for thermal energy storage – Part I: Effect of synthetic phosphate content on microstructure, thermo-physical and thermo-mechanical properties

Fired clay ceramics are promising materials for TES, thanks to their thermal stability, availability worldwide, low cost and easy shaping and handling. However, their thermo-physical and thermo-mechanical properties have to be improved. For the first time, clay-phosphate ceramics, with synthetic calcium hydroxyapatite (TCP, Ca10(PO4)6(OH)2) as additive, were developed in view of TES application. A parametric study was carried out for different clay/TCP mixtures, wherein the TCP percentage varies from 0 to 16.7 wt%. The best material containing 4.7 wt% TCP allowed increasing up to 20% of the thermal conductivity and 23% of the mechanical strength. Moreover, it was thermally stable up to 1000 °C. These original results demonstrate the suitability of these new materials for heat storage in energy systems such as in a concentrated solar power (CSP) plant, or in a unit of heat recovery from an industrial waste heat source

A 3.5 Ga granite-gneiss basement in Guinea: further evidence for early archean accretion within the West African Craton

A granite-gneiss formation (Guélémata Orthogneiss) was mapped on the northern and western slopes of the Mount Nimba hill range in Guinea. The original rocks were high-Al, low-Yb, medium to high-K granites similar to most Archean TTG. Analyses of U and

An investigation of the physical, thermal and mechanical properties of fired clay/SiC ceramics for thermal energy storage

International audienceThermal energy storage (TES) has been identified as a breakthrough concept in development of renewable technologies. However, the main challenges are related to the development of competitive heat storage materials. Despite the number of studies on heat storage materials, the determination of new alternatives for next generation technologies is still open. In this regard, this paper presents the results of an experimental study of the physical, thermal and mechanical properties of SiC-doped ceramics as potential materials for TES applications. Two kinds of SiC additives (high and low densities) were incorporated with different percentages into the clay matrix in order to produce ceramics via the extrusion process. The addition of low-density SiC (true density 3.16 g cm−3) led to the increasing of porosity with large pore sizes and the decreasing of bulk density. Therefore, the thermal and mechanical properties are decreased up to − 50% for flexural strength and − 15% for thermal conductivity when 20 mass% of low-density SiC was used. On the other hand, when high-density SiC (true density 3.42 g cm−3) was used, properties of the clay ceramic were strongly improved: i.e., increase in the bulk density, decrease in the porosity, increase in the thermal conductivity and increase in the flexural strength. The best material was found with the addition of 20 mass% of high-density SiC which had a thermal conductivity of 1 W m−1 K−1, a specific heat capacity of 0.62 kJ kg−1 K−1 and a mechanical strength of 19.6 MPa. It also showed a high thermal stability after 20 successive heating/cooling cycles. Hence, this study provided a useful insight into how the SiC modified the microstructure and properties of fired clay ceramics. Thus, the current results suggest that clay ceramics with high-density SiC addition are promising materials for thermal energy storage application