Intestinal dual-specificity phosphatase 6 regulates the cold-induced gut microbiota remodeling to promote white adipose browning.

Gut microbiota rearrangement induced by cold temperature is crucial for browning in murine white adipose tissue. This study provides evidence that DUSP6, a host factor, plays a critical role in regulating cold-induced gut microbiota rearrangement. When exposed to cold, the downregulation of intestinal DUSP6 increased the capacity of gut microbiota to produce ursodeoxycholic acid (UDCA). The DUSP6-UDCA axis is essential for driving Lachnospiraceae expansion in the cold microbiota. In mice experiencing cold-room temperature (CR) transitions, prolonged DUSP6 inhibition via the DUSP6 inhibitor (E/Z)-BCI maintained increased cecal UDCA levels and cold-like microbiota networks. By analyzing DUSP6-regulated microbiota dynamics in cold-exposed mice, we identified Marvinbryantia as a genus whose abundance increased in response to cold exposure. When inoculated with human-origin Marvinbryantia formatexigens, germ-free recipient mice exhibited significantly enhanced browning phenotypes in white adipose tissue. Moreover, M. formatexigens secreted the methylated amino acid Nε-methyl-L-lysine, an enriched cecal metabolite in Dusp6 knockout mice that reduces adiposity and ameliorates nonalcoholic steatohepatitis in mice. Our work revealed that host-microbiota coadaptation to cold environments is essential for regulating the browning-promoting gut microbiome.

High-pressure combinatorial screening of homogeneous catalysts: hydrogenation of carbon dioxide.

A simple method for high-pressure combinatorial catalyst discovery with visual (dye-based) assay is described. With this method, the first highly active catalyst, incorporating metals outside the platinum group, has been identified for CO(2) hydrogenation.

Low-temperature synthesis of tetraalkylureas from secondary amines and carbon dioxide.

The reaction of dialkylamines with CO(2) giving tetraalkylureas can be performed at 60 degrees C. The reaction requires CCl(4), is weakly promoted by DMAN or PPh(3), and is not promoted by a Pd catalyst. A two-step procedure, in which dialkylammonium dialkylcarbamate is produced in situ and then reacted with CCl(4) and free dialkylamine, gave greater yields of urea than a simple single-stage procedure.

Hydrogenation of carbon dioxide catalyzed by ruthenium trimethylphosphine complexes: the accelerating effect of certain alcohols and amines.

A trace amount of alcohol cocatalyst and a stoichiometric amount of base are required during the hydrogenation of CO(2) to formic acid catalyzed by ruthenium trimethylphosphine complexes. Variation of the choice of alcohol and base causes wide variation in the rate of reaction. Acidic, nonbulky alcohols and triflic acid increase the rate of hydrogenation an order of magnitude above that which can be obtained with traditionally used methanol or water. Similarly, use of DBU rather than NEt(3) increases the rate of reaction by an order of magnitude. Turnover frequencies up to 95,000 h(-1) have now been obtained, and even higher rates should be possible using the cocatalyst and amine combinations identified herein. Preliminary in situ NMR spectroscopic observations are described, and the possible roles of the alcohol and base are discussed.

In situ formation of ruthenium catalysts for the homogeneous hydrogenation of carbon dioxide.

A total of 44 different phosphines were tested, in combination with [RuCl(2)(C(6)H(6))](2) and three other Ru(II) precursors, for their ability to form active catalysts for the hydrogenation of CO(2) to formic acid. Half (22) of the ligands formed catalysts of significant activity, and only 6 resulted in very high rates of production of formic acid. These were PMe(3), PPhMe(2), dppm, dppe, and cis- and trans-Ph(2)PCH=CHPPh(2). The in situ catalysts prepared from [RuCl(2)(C(6)H(6))](2) and any of these 6 phosphine ligands were found to be at least as efficient as the isolated catalyst RuCl(O(2)CMe)(PMe(3))(4). There was no correlation between the basicity of monophosphines (PR(3)) and the activity of the catalysts formed from them. However, weakly basic diphosphines formed highly active catalysts only if their bite angles were small, while more strongly basic diphosphines had the opposite trend. In situ (31)P NMR spectroscopy showed that trans-Ru(H)(2)(dppm)(2), trans-RuCl(2)(dppm)(2), trans-RuHCl(dppm)(2), cis-Ru(H)(O(2)CH)(dppm)(2), and cis-Ru(O(2)CH)(2)(dppm)(2) are produced as the major metal-containing species in reactions of dppm with [RuCl(2)(C(6)H(6))](2) under catalytic conditions at 50 degrees C.