Suppression of apolipoprotein B production during treatment of cholesteryl ester storage disease with lovastatin. Implications for regulation of apolipoprotein B synthesis

Cholesteryl ester storage disease (CESD) is characterized by the deficient activity of lysosomal cholesteryl ester (CE) hydrolase, accumulation of LDL-derived CE in lysosomes, and hyperlipidemia. We studied the kinetics in VLDL and LDL apolipoprotein B (apoB), using ¹²⁵I-VLDL and ¹³¹I-LDL, in a 9-yr-old female with CESD and elevated total cholesterol (TC) (271.0 ± 4.4 mg/dl), triglyceride (TG) (150.0 ± 7.8 mg/dl), and LDL cholesterol (184.7 ± 3.4 mg/dl). These studies demonstrate a markedly elevated production rate (PR) of apoB, primarily in LDL, with normal fractional catebolism of apoB in VLDL and LDL. Urine mevalonate levels were elevated, indicative of increased synthesis of endogenous cholesterol. Treatment with lovastatin, a competitive inhibitor of hydroxymethylglutaryl coenzyme A reductase, resulted in significant reductions in TC (196.8 ± 7.9 mg/dl), TG (100.8 ± 20.6 mg/dl), and LDL cholesterol (102.0 ± 10.9 mg/dl). Therapy reduced VLDL apoB PR (5.2 vs. 12.2 mg/kg per d pretreatment) and LDL apoB PR (12.7 vs. 24.2 mg/kg per d treatment). Urine mevalonate levels also decreased during therapy. These results indicate that, in CESD, the inability to release free cholesterol from lysosomal CE resulted in elevated synthesis of endogenous cholesterol and increased production of apoB-containing lipoproteins. Lovastatin reduced both the rate of cholesterol synthesis and the secretion of apoB-containing lipoproteins.