GLP-1 and forskolin but not high glucose nor insulin mimics the Akt
kinase stimulatory effects of GIP. A, INS-1 cells were pretreated
with DMSO (control) or 15 μm LY294002 for 30 min and then
treated ± 10 nm GIP, 10 nm GLP-1, or 500
pm insulin (all with 3 mm glucose) or 16 mm
glucose for 15 min, and Western analysis was performed on Akt KA assays with
indicated antibodies. IP, immunoprecipitate. B, shown is the
mean change ± S.E. in Akt activity (P-GST-GSK3/Akt) relative to DMSO
(n = 4). #, p < 0.05 versus control without
LY294002. C, INS-1 cells were pretreated with DMSO (control) or
PI3K/Akt signaling inhibitors (15 μm LY294002 or 5
μm Akt VIII) for 1 h and then treated with ±1
μm forskolin for 15 min, and Western analysis was performed on
cell lysates or Akt KA assays with indicated antibodies. D, shown is
the mean change ± S.E. in Akt activity (P-GST-GSK3/Akt) relative to
DMSO control (n = 4). #, p < 0.05 versus DMSO
control. Anti-β-actin and anti-GST (GST-GSK3) blots were internal
controls.