No abstract

Triggering receptor expressed on myeloid cells 2 (TREM2) is known to be involved in the anti-inflammatory response and osteoclast development. However, the role of TREM2 in adipogenesis or obesity has not yet been defined. The effect of TREM2 on adipogenesis and obesity was investigated in TREM2 transgenic (TG) mice on a high-fat diet (HFD). To block TREM2 signaling, a neutralizing fusion protein specific for TREM2 (TREM2-Ig) was used. TG mice were much more obese than wild-type mice after feeding with an HFD, independent of the quantity of food intake. These HFD-fed TG mice manifested adipocyte hypertrophy, glucose and insulin resistance, and hepatic steatosis. The expression of adipogenic regulator genes, such as peroxisome proliferator-activated receptor g and CCAAT/enhancerbinding protein a, was markedly increased in HFD-fed TG mice. Additionally, HFD-fed TG mice exhibited decreased Wnt10b expression and increased GSK-3b (glycogen synthase kinase-3b)-mediated b-catenin phosphorylation. In contrast, the blockade of TREM2 signaling using TREM2-Ig resulted in the inhibition of adipocyte differentiation in vitro and a reduction in body weight in vivo by downregulating the expression of adipogenic regulators. Our data demonstrate that TREM2 promotes adipogenesis and diet-induced obesity by upregulating adipogenic regulators in conjunction with inhibiting the Wnt10b/b-catenin signaling pathway.

Charge transfer through thin layers of water between a Pt/Ir tip and a gold surface has been investigated by using a scanning tunneling microscopy (STM) technique at the temperature of 21 ( 1 °C. The amount of the water layer inside the STM or an atomic force microscopy (AFM) junction was controlled by relative humidity. It was found from STM, AFM, and quartz crystal microbalance experiments that the thin water film was formed on the gold sample when relative humidity was in the range up to 80%. Charge transfer across the interfacial water layer was found to originate mostly from electron tunneling. The value of the barrier height of the electron tunneling was determined to be 0.95 eV from the current vs distance curve, which was independent of the tip-sample distance and the bias voltage. At relative humidity above 90%, the surface was covered with a thick water layer. In such a case the decay for charge transfer was strongly dependent on the bias voltage. For a low bias of 0.03 V charge transfer was similar to that at low relative humidity. On the contrary, the current was found to decay nonexponentially in the bias range of |0.1|-|0.5| V, where the plateau currents were observed in the long distance. The plateau current at 0.5 V was observed to flow up to several hundred nanometers. The magnitude of the plateau currents depended on the applied electrode potential as well as its polarity. The results were rationalized by means of electron tunneling and electrochemical process through the thick water layer.

No abstract

Single hop diffusion of CO from bridge to top sites on Pt(111)Ultraviolet photodesorption of CO and CO ϩ from Pt͑111͒ at 80 K is investigated by ͑2ϩ1͒ resonance-enhanced multiphoton ionization and reflection absorption infrared spectroscopy. Desorption of CO and CO ϩ occurs at the on-top site as single-photon and three-photon processes, respectively. The rotational, vibrational, and translational temperatures of desorbed CO are approximately 130, 3700, and 2000 K, which are considerably higher than the sample temperature. The threshold energy of neutral CO desorption lies between 2.3 and 3.5 eV suggesting that an unoccupied 2 state is responsible for the desorption.