INSULIN STIMULATES COLLAGEN-SYNTHESIS IN VASCULAR SMOOTH-MUSCLE CELLSFROM ELDERLY PATIENTS

The process of aging results in an increase in collagen in arterial wa lls, but the blood levels of insulin-like growth factor 1 (IGF-1) decr ease remarkably as adults age. There is an almost simultaneous increas e in insulin secretion, particularly in obese individuals. It is not k nown if, under these hormonal conditions, the enrichment of collagen i n the arterial wall is due to insulin. We studied the effect of insuli n on the production of collagen in vascular smooth muscle cells (VSMC) from elderly persons with high levels of insulin secretion after bloc king the insulin receptors with a monoclonal antibody. Results were co mpared to those without insulin receptor blockage and to those with IG F-1. Despite the inhibition of C-14-glucose uptake, insulin clearly st imulated the release of procollagen III, and increased the collagen sy nthesis. The hydroxyproline labelling rate from H-3-proline increased to more than twice the control values, IGF-1 is a more potent effector than insulin, but the effect of insulin on the rate of collagen produ ction became similar to IGF-1 when the specific receptors were blocked . The results indicate that under special conditions that occur with a ging, insulin interacts with nonspecific receptors in VSMC, especially IGF-1, stimulating these cells to produce collagen.