Insulin Induces Production of New Elastin in Cultures of Human Aortic Smooth Muscle Cells

Diabetes mellitus accelerates atherosclerotic progression, peripheral angiopathy development, and arterial hypertension, all of which are associated with elastic fiber disease. However, the potential mechanistic links between insulin deficiency and impaired elastogenesis in diabetes have not been explored. Results of the present study reveal that insulin administered in therapeutically relevant concentrations (0.5 to 10 nmol/L) selectively stimulates formation of new elastic fibers in cultures of human aortic smooth muscle cells. These concentrations of insulin neither upregulate collagen type I and fibronectin deposition nor stimulate cellular proliferation. Further, the elastogenic effect of insulin occurs after insulin receptor activation, which triggers the PI3K downstream signaling pathway and activates elastin gene transcription. In addition, the promoter region of the human elastin gene contains the CAAATAA sequence, consistent with the FoxO-recognized element, and the genomic effects of insulin occur after removal of the FoxO1 transcriptional inhibitor from the FoxO-recognized element in the elastin gene promoter. In addition, insulin signaling facilitates the association of tropoekistin with its specific 67-kDa elastin-binding protein/spliced form of beta-galactosidase chaperone, enhancing secretion. These results are crucial to understanding of the molecular and cellular mechanisms of diabetes-associated vascular disease, and, in particular, endorse use of insulin therapy for treatment of atherosclerotic lesions in patients with type 1 diabetes, in which induction of new elastic fibers would mechanically stabilize the developing plaques and prevent arterial occlusions. (Am J Pathol 2012, 180: 715-72 DOI: 10.1016/j.ajpath.2011.10.022)