FIG. 4.

4-HDDE specifically activates PPARδ and downregulates the glucose transport system in VECs. A: VEC cultures that had been maintained at 5.5 mmol/l glucose were transfected with the various hPPAR expression vectors and other plasmids and incubated as described in the legend to Fig. 3B. Cultures received the indicated concentration of 4-HDDE during the last 24 h of incubation. The cells were then lysed, and the relative luciferase activity was determined and standardized to the untreated control. *P < 0.05, for differences from the untreated cells (n = 4). B–D: Confluent VEC cultures were incubated for 48 h with 5.5 or 25 mmol/l glucose in the absence or presence of 4-HDDE (50 nmol/l). Baicalein (80 μmol/l) was added to cultures for the last 10 h of incubation. The cells were then washed, lysed, and taken for the standard [³H]dGlc uptake assay (B), real-time PCR analysis of GLUT-1 mRNA (C), or Western blot analysis of total GLUT-1 (D). The rate of dGlc uptake at 5.5 mmol/l glucose (79 ± 3 pmol dGlc/10⁶ cells/min) was taken as 100%. *P < 0.05, for differences from the respective controls (n = 4). E: Confluent VEC cultures were incubated at 5.5 or 25 mmol/l glucose for 48 h in the absence or presence of 4-HDDE (50 nmol/l) and or GSK0660 (1 μmol/l), as indicated. At the end of incubation the cells were washed and taken for the standard [³H]dGlc uptake assay. The rate of dGlc uptake at 5.5 mmol/l glucose (65 ± 8 pmol/10⁶ cells/min) was taken as 100%. *P < 0.05, for differences from the respective controls (n = 4).