RESUMEN
As the beneficial effects of the Mediterranean diet on human health are well established, the phenolic compounds in olive oil have been gaining interest. Oleuropein, a major phenolic compound in olives, is known to reduce the blood glucose levels in alloxan-induced diabetic rats and rabbits, however, its effect on type 2 diabetes caused by obesity is not clear. The purpose of this study is clarifying the effect of oleuropein on the glucose tolerance in skeletal muscle under the condition of lipotoxicity caused by type 2 diabetes. Oleuropein enhanced glucose uptake in C2C12 cells without insulin. Translocation of glucose transporter 4 (GLUT4) into the cell membrane was promoted by activation of adenosine monophosphate-activated protein kinase (AMPK) but not protein kinase B (Akt). Physiological concentration of oleuropein (10 µM) was sufficient to express beneficial effects on C2C12 cells. Oleuropein prevented palmitic acid-induced myocellular insulin resistance. Furthermore, in gastrocnemius muscles of mice fed a high fat diet, oleuropein also induced the GLUT4 localization into cell membrane. These results suggest the possibility of oleuropein to be effective for type 2 diabetes by reducing insulin resistance in skeletal muscles.
RESUMEN
We developed a new-type rapid polychlorinated biphenyl (PCB) analysis technology on the basis of a liquid chromatographic clean-up system combined with a large-volume injection GC-LRMS. Among 18 kinds of materials such as polymer gels, normal-phase silica gels, reversed-phase silica gels, carbon material and ion-exchange material, polyvinyl alcohol (PVA) gel and poly (hydroxylmethacrylate) gel were found to give rather good separation performance for insulating oil. Especially, PVA gel was confirmed to be the most suitable for rapid PCB analysis because of its least required quantity of fraction liquid as well as the highest resolution. Then, we confirmed elution characteristics of all PCB isomers and removal efficiency of insulating oil on PVA gel under an optimized condition, and established high-performance clean-up system using a combination of octadecyl silica gel (ODS), porous graphite carbon (PGC) and PVA gel. In this system, we applied newly valve-switching method that could remove other impurities. In addition, it was demonstrated that the proposed clean-up system could become highly sensitive and rapid PCB analysis technology with 2-h analysis time, lower measurement limit of less than 0.05 mg/kg, and a variation coefficient of less than 5%, by coupling with a large-volume injection type GC-LRMS. Thus, we can conclude that this rapid PCB analysis technology has not only good correlativity (R2>0.999) with standard analysis method but also high durability and can be fully applied to actual PCB-treatment plants.