Vascular endothelial growth factor B inhibits insulin secretion in MIN6 cells and reduces Ca2+ and cyclic adenosine monophosphate levels through PI3K/AKT pathway

Figure 4 Vascular endothelial growth factor B inhibits Ca²⁺ and cyclic adenosine monophosphate levels and phospholipase C gamma 1 protein expression in MIN6 cells. A: Exogenous vascular endothelial growth factor B (VEGF-B, VB) protein reduces cyclic adenosine monophosphate (cAMP) levels in MIN6 cells. ^bP < 0.01 vs VB-0 in the presence of 5.5 mmol/L glucose; ^dP < 0.01 vs VB-0 in the presence of 25 mmol/L glucose; B: cAMP levels in MIN6 cells increase after VEGF-B is knocked down. ^bP < 0.01, ^cP < 0.001 vs Control in the presence of 5.5 mmol/L glucose; ^dP < 0.05 vs Control in the presence of 25 mmol/L glucose; C: Exogenous VEGF-B protein reduces Ca²⁺ levels in MIN6 cells. ^bP < 0.01 vs VB-0 in the presence of 5.5 mmol/L glucose; D: Ca²⁺ levels in MIN6 cells increase after VEGF-B is knocked down. ^cP < 0.001 vs Con in the presence of 5.5 mmol/L glucose; ^dP < 0.01, ^eP < 0.001 vs Con in the presence of 25 mmol/L glucose; E and F: Western blot analysis revealing the relative protein expression of phospholipase C gamma 1 (PLCγ1) and phosphorylated (p)-PLCγ1 in cells stimulated with exogenous VEGF-B and corresponding statistical data. ^aP < 0.05 vs VB-0 for P-PLCγ1; ^bP < 0.05 vs VB-0 for PLCγ1; G: The effect of exogenous VEGF-B protein stimulation on PLCγ1 phosphorylation; H and I: Western blot analysis revealing the relative protein expression of PLCγ1 and p-PLCγ1 in cells transfected with VEGF-B siRNA and corresponding statistical data. ^aP < 0.05 vs Control for p-PLCγ1, ^bP < 0.05 vs Control for PLCγ1; J: Effect of VEGF-B knockdown on PLCγ1 phosphorylation. Student's t-test was performed. VEGF-B: Vascular endothelial growth factor B; VB: VEGF-B; cAMP: Cyclic adenosine monophosphate; Con: Control; Si: Small interfering RNA; MIN6: MIN6 cell; PLCγ1: Phospholipase C gamma 1; p-PLCγ1: Phosphorylated phospholipase C gamma 1.