Low Density Lipoprotein Receptor Activity in Fibroblasts Cultured from Diabetic Donors

Abstract

Low density lipoprotein (LDL) receptor activity was evaluated in cultured skin fibroblasts from diabetics and nondiabetic controls to evaluate whether intrinsic abnormalities of the LDL pathway exist, which might account for the premature atherosclerosis associated with diabetes mellitus. LDL receptors did not differ between cells grown from 16 diabetics (7 insulin-dependent, 9 non-insulin-dependent) or from 16 nondiabetic controls. An inverse relationship between LDL receptor activity and cell density was observed (y = 1.35 × −1.22, r = 0.90, P < 0.001), which appeared the same for diabetic and nondiabetic cells. Normalized values for LDL degradation by diabetic and nondiabetic cell strains were 1.52 ± 0.42% of added LDL/106 cells and 1.34 ± 0.28, respectively (P = NS). The kinetics of the LDL receptor also appeared to be the same in cells derived from a diabetic and a nondiabetic donor. LDL receptor activity in diabetic cells increased appropriately in response to physiologic concentrations of insulin in the incubation medium. Thus, LDL receptor activity appears to be normal in diabetic cell strains. Therefore, these results do not support the possibility that alterations in the LDL pathway contribute to the accelerated atherosclerosis associated with diabetes.