Objective: We recently demonstrated a potent anti-inflammatory and thus a potential antiatherogenic effect of insulin in human aortic endothelial cells and mononuclear cells at physiologically relevant concentrations. We have now further investigated the anti-inflammatory suppressive action of insulin on vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP)-9. VEGF and MMP-9 play a central regulatory role in angiogenesis, contribute to the pathogenesis of proliferative retinopathy, and have also been found to accelerate atherosclerosis.
Research design and methods: Insulin was infused (2 IU/h) in 5% dextrose (100 ml/h) and KCl (8 mmol/h) into 10 fasting, obese, nondiabetic subjects for 4 h. Subjects were also infused with 5% dextrose without insulin and with saline on two separate occasions. Blood samples were obtained at 0, 2, 4, and 6 h.
Results: Plasma insulin concentrations increased from a basal level of 12.5 +/- 2.2 to 28.2 +/- 3.3 micro U/ml at 2 h and 24.4 +/- 3.7 micro U/ml at 4 h after insulin infusion. VEGF concentration decreased from 307.2 +/- 163.8 pg/ml (100%) at 0 h to 73.5 +/- 20.9% of the basal level at 2 h and 67.1 +/- 23.2% at 4h. Plasma MMP-9 concentrations decreased from 375 +/- 196.3 ng/ml (100%) at 0 h to 83 +/- 22% of the basal level at 2 h and to 82 +/- 21% of the basal level at 4 h (P < 0.05). Dextrose infusion alone did not change plasma VEGF concentration. However, plasma MMP-9 concentration increased significantly at 4 h following dextrose infusion alone (P < 0.05). Saline infusions without insulin caused no alteration in glucose, insulin, VEGF, or MMP-9.
Conclusions: These observations may have implications for a potential antiretinopathic and antiatherosclerotic effect of insulin in the long term.