Effects of membrane lipid unsaturation on the interactions of insulin and multiplication stimulating activity with endothelial cells.

Modification of plasma membrane fatty acyl composition has resulted in major changes in insulin binding and insulin action in several cell types. In the present study, endothelial cells, which in vivo are directly bathed by the changing fatty acid and insulin environment of the bloodstream, were grown in media enriched in specific saturated, monounsaturated and polyunsaturated fatty acids. These media conditions resulted in major and specific alteration in fatty acyl unsaturation of both neutral lipids and phospholipids of the endothelial cells. Despite the extensive fatty acyl changes, the lipid-modified cells demonstrated no change in the binding of insulin or the insulin-like growth factor, multiplication stimulating activity, and little alteration in insulin-induced down-regulation of the insulin receptor, or in cell processing of insulin. We suggest that the insulin receptor of the endothelial cell responds in a different manner than other cell types to similar alterations of membrane fatty acyl composition.