Sterol Synthesis and HMG CoA Reductase Activity in Cultured Skin Fibroblasts from Heterozygous Familial Hypercholesterolemic Patients with Abnormally Thick Achilles Tendon

Abstract

In the previous paper, we reported that radiological examination of the Achilles tendon thickness is useful for diagnosis of familial hypercholesterolemia. To validate Achilles tendon thickness in diagnosing familial hypercholesterolemia, we examined sterol synthesis from [¹⁴C] acetate and HMG CoA Reductase activity in cultured skin fibroblasts derived from one fetus, two normal subjects and six heterozygous familial hypercholesterolemic patients.
The Achilles tendon thickness (14.3±2.1mm, mean±SD) in the heterozygotes were significantly thicker than those of the normal subjects (6.3±1.2mm).
Cells were grown in dishes containing 10% fetal calf serum. On Day 6, the medium was replaced with 3ml of fresh medium containing 10% human lipoprotein deficient serum (LPDS). Twenty-four hr later, human serum was added to obtain an appropriate concentration of cholesterol.
The results were as follows.
1. Cholesterol synthesis from [¹⁴C] acetate in normal cells decreased by 90.8±5.2% (mean±SEM) when the medium concentration of cholesterol changed from zero to 12μg/ml. While cholesterol synthesis in heterozygous cells decreased by 59.6±4.0%, homozygous cell (GM-486) showed no response at 12μg/ml of cholesterol.
2. HMG CoA Reductase activity in normal cells decreased by 87.4±7.9% when the medium concentration of cholesterol was changed from zero to 20μg/ml. The Reductase activity in heteroxygous cells decreased by 40.6±4.7%. The homozygous cell showed 88% activity at cholesterol concentration of 120μg/ml.
3. From these data, it is concluded that all six hypercholesterolemic patients with abnormally thick tendon are familial and radiological examination of Achilles tendon is very useful for diagnosis.