Low density lipoprotein receptor activity in cultured skin fibroblasts from octa- and nonagenarians

Low density lipoprotein (LDL) receptor activity determined as association or degradation of 125I-LDL at 37 degrees C, was measured in cultured skin fibroblasts from 48 elderly, independent subjects (84-95 years old). Data concerning these subjects were compared with those from a reference group of 27 younger, healthy subjects (5-64 years old) and 23 heterozygotes for familial hypercholesterolemia (9-67 years old). The median (10th-90th percentile) association and degradation value for the older subjects were 294 (172-535) ng 125I-LDL/mg protein/6h and 191 (99-376) ng 125I-LDL/mg protein/6h, respectively. These values did not differ significantly from the corresponding values in the normal subjects (296 (60-491) ng 125I-LDL/mg protein/6h and 171 (99-275) ng 125I-LDL/mg protein/6h, respectively). Thus, maximal LDL receptor activity in fibroblasts from the older subjects seems to be comparable to that of younger, healthy controls. However, the elderly subjects had markedly higher values for total serum cholesterol and LDL cholesterol than the normal controls. There was a significant increase in LDL receptor activity with age in the normal controls. Such an increase was not found in heterozygotes for familial hypercholesterolemia.