Chlorogenic Acid Stimulates Glucose Transport in Skeletal Muscle via AMPK Activation: A Contributor to the Beneficial Effects of Coffee on Diabetes

Chlorogenic acid (CGA) has been shown to delay intestinal glucose absorption and inhibit gluconeogenesis. Our aim was to investigate the role of CGA in the regulation of glucose transport in skeletal muscle isolated from db/db mice and L6 skeletal muscle cells. Oral glucose tolerance test was performed on db/db mice treated with CGA and soleus muscle was isolated for 2-deoxyglucose transport study. 2DG transport was also examined in L6 myotubes with or without inhibitors such as wortmannin or compound c. AMPK was knocked down with AMPKα1/2 siRNA to study its effect on CGA-stimulated glucose transport. GLUT 4 translocation, phosphorylation of AMPK and Akt, AMPK activity, and association of IRS-1 and PI3K were investigated in the presence of CGA. In db/db mice, a significant decrease in fasting blood sugar was observed 10 minutes after the intraperitoneal administration of 250 mg/kg CGA and the effect persisted for another 30 minutes after the glucose challenge. Besides, CGA stimulated and enhanced both basal and insulin-mediated 2DG transports in soleus muscle. In L6 myotubes, CGA caused a dose- and time-dependent increase in glucose transport. Compound c and AMPKα1/2 siRNA abrogated the CGA-stimulated glucose transport. Consistent with these results, CGA was found to phosphorylate AMPK and ACC, consistent with the result of increased AMPK activities. CGA did not appear to enhance association of IRS-1 with p85. However, we observed activation of Akt by CGA. These parallel activations in turn increased translocation of GLUT 4 to plasma membrane. At 2 mmol/l, CGA did not cause any significant changes in viability or proliferation of L6 myotubes. Our data demonstrated for the first time that CGA stimulates glucose transport in skeletal muscle via the activation of AMPK. It appears that CGA may contribute to the beneficial effects of coffee on Type 2 diabetes mellitus

Micro‐computed tomography analysis of enamel structure after different bleaching treatments

The aim of this investigation is to assess effect of three different bleaching techniques on structural integrity, mineral density and volume of enamel via micro-computed tomography (micro-CT) and examine color changes by CIELAB and CIEDE2000 formulas. Twenty-four upper premolar teeth were randomly separated into three different groups (n = 8) (group 1, 35% hydrogen peroxide (HP) gel with Er,Cr:YSGG laser activation; group 2, 35% HP gel with diode laser activation; group 3, 35% HP gel with chemically activation). High-resolution micro-CT system (Bruker Skyscan 1275, Kontich, Belgium) was carried out to scan samples. Each tooth was scanned twice before-after application of bleaching with same scanning parameters. Structural thickness, structural separation, fragmentation index, mineral density, and mineral volume of enamel were calculated for each region of interest (ROI). Color changes were measured with spectrophotometer and calculated with CIELAB and CIEDE2000 formulas. Data analysis was made with one-way ANOVA with post-hoc LSD. Micro-CT analysis indicated that statistically significant differences were found in structural thickness, and separation, mineral density, and mineral volume of enamel for different ROIs before and after whitening for whole groups (P .05). All bleaching applications exhibited similar efficiency on the enamel surface. Nevertheless, bleaching process with Er,Cr:YSGG laser had less negative effects on enamel as it showed less change in enamel compared to other bleaching treatments. Micro-CT analysis of histomorphometric parameters can be useful for further mineralization studies of dental hard tissues

Development of a Maximum Energy Extraction Control for the Smart Spring

Peer reviewed: YesNRC publication: Ye