Control of sterol synthesis and of hydroxymethylglutaryl CoA reductase in skin fibroblasts grown from patients with homozygous type II hyperlipoproteinemia

In skin fibroblasts grown from four children with a homozygous form of type II hyperlipoproteinemia, the feedback control of sterol synthesis and the inhibitory effect on hydroxymethylglutaryl (HMG) CoA reductase activity by serum or low density lipoprotein were present, though diminished compared with the effects in normal fibroblasts. Stimulation of HMG CoA reductase by insulin and inhibition of acetyl CoA carboxylase by serum lipids were not impaired in these type II cells, indicating a degree of specificity in the abnormal response of the reductase. A rapid and convenient method for isolation of mevalonolactone in the course of the assay of HMG CoA reductase is described.