Insulin as a growth regulator of arterial smooth muscle cells: effect of insulin of I.G.F.I.

The proliferation of smooth muscle cells in the vessel wall plays an important role in the development of an atherosclerosis. The insulin-like growth factor I (I.G.F.I) is an important growth factor for cultivated arterial smooth muscle cells. The plasma I.G.F.I level is controlled by growth hormone and insulin--both factors seem to be important for the development of a diabetic macroangiopathy. In order to evaluate whether I.G.F.I is associated with the development of a macroangiopathy we measured the serum I.G.F.I level in type 2 diabetics with and without macroangiopathy and in non diabetic patients with atherosclerosis and in healthy controls. The range of the individual I.G.F.I levels was wide and the I.G.F.I level between the various groups was not statistically significant. However, our studies with cultured cells show that modulation of the cellular responsiveness to I.G.F.I is as important in the growth control as are changes in the plasma I.G.F.I level. We observed that cultured smooth muscle cells were able to produce an I.G.F.I-like factor. The synthesis and secretion of this factor was dependent on insulin. These findings explain one mechanism by which insulin may influence the growth of smooth muscle cells in the vessel wall.