Pravastatin in Heterozygous Familial Hypercholesterolemia: Low-Density Lipoprotein (LDL) Cholesterol-Lowering Effect and LDL Receptor Activity Skin FibrobIasts A. Gaddi, M. Arca, A. Ciarrocchi,
S. Fazio, G. D’Alb, R. Tiozzo, G.C. Descovich,
on
and S. Calandra
The cholesterol-lowering effect of pravastatin, a new competitive inhibitor of 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase, was studied in 10 patients with heterozygous familial hypercholesterolemia (FH). Residual low-density lipoprotein receptor (LDL-R) activity was also evaluated in cultured skin fibroblasts prior to treatment, and showed a wide range of reduction from 30% to 70% of the normal value. Treatment with pravastatin 40 mg once daily reduced total and LDL cholesterol (LDL-C) after 6 months by 19.7% and X4%, respectively (P < .OOl). Serum apolipoprotein (apo) B levels decreased significantly by 29.1% (P < .OOl). No significant changes were observed in mean serum total triglycerides or high-density lipoprotein cholesterol (HDL-C) levels. A positive correlation between residual LDL-R activity and maximum percent reduction of LDL-C levels was observed (r = .676, P i .05J. No clinically important side effects were recorded and the treatment was well tolerated. Thus, pravastatin effectively reduces LDL in heterozygous FH, and this effect appears to be related to LDL-R status. Copyright 0 1991 by W.B. Saunders Company
F
AMILIAL hypercholesterolemia (FH) is an autosomaldominant lipid disorder characterized by elevated levels of low-density lipoprotein cholesterol (LDL-C) in plasma, tendon xanthomas, and premature coronary artery disease (CAD).’ The underlying defect is a reduced number of functional cellular LDL receptors (LDL-R).’ Lowering LDL-C levels is the main goal in the treatment of these patients, since epidemiological studies and intervention trials indicate that a reduction of LDL-C is associated with a decreased incidence of CAD.’ The treatment of heterozygous FH patients is often complex, as many cases respond poorly to dietary treatment and only moderately to hypolipidemic drugs.‘,’ Over the last few years, the introduction of a new class of choiesterollowering drugs has offered new promise for the treatment of FH. These drugs, which inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme of cholesterol biosynthesis,5 lower total cholesterol and LDL-C not only by reducing cholesterol synthesis in the body,6 but also by increasing the receptor-dependent uptake of LDL.’ It is generally accepted that, by interfering with the synthesis of cholesterol in the liver, HMG-CoA reductase inhibitors would lower the intracellular concentration of cholesterol and thereby stimulate the synthesis of LDL receptors.Z.4 In animals treated with HMG-CoA reductase inhibitors, there is an increased level of LDL-R mRNA in the liver’ and an enhanced number of receptors on liver cell membranes.’ HMG-CoA reductase inhibitors were proved to be effective in lowering LDL-C in heterozygous FH,‘,” but not in
From the Cattedra di Medicina Interna e Centro Aterosclerosi. Universirtidi Boiogna, Bologna; Istitufo di Terapia Medica Sistematica, Universitcidi Roma. Roma; Squibb SPA, Roma; and rhe Istituto Patologia Generale, Vniversitri di Modena. Modena, Ita[y. Supported in part by grants of the Emilia Romagna Region (Health Research Finalized Programmes) and by the Universities of Bologna and Modena. Address reprint requests to G. D’AU, MD, Squibb SPA. Via Paolo di Dono 73, Rome, Italy. Copyright 0 1991 by W.B. Saunders Company 0086-0495191 IlOIO-0014$03.00/O 1074
receptor-negative homozygous patients.” This would suggest that the efficacy of the HMG-CoA reductase inhibitors largely depends on the presence of one functional allele at the LDL-R locus. Since many different mutations can cause defects in LDL-R protein,“.” the severity of the LDL-R defects in heterozygous FH may vary over a wide range.” If this is the case, one could presume that the variable response of FH heteroqgotes to HMG-CoA reductase inhibitors”’ is related to the receptor status of the patient (ie, residual receptor activity under basal conditions), even though other factors (apolipoprotein [apo] E phenotype, apo B structure, intestinal cholesterol absorption, etc) may play an important role. In this study, we have attempted to evaluate the possible relationship in heterozygous FH between the degree of LDL-R defect (measured in cultured skin fibroblasts) and the cholesterol-lowering effect of pravastatin, a new tissueselective HMG-CoA reductase inhibitor.”
MATEAlALS
AND METHODS
Subjects and Study Design
Ten unrelated outpatients (eight men and two women: mean age, 48.2 years) with heterozygous FH were studied. Diagnosis was based on the following criteria’: (1) in the propositus: presence of primary stable hypercholesterolemia (phenotype Ila) with LDL-C levels greater than 90th percentile of the control population (230 mg/dL) and very-low-density lipoprotein triglyceride (VLDL-TG) greater than 120 mg/dL. and presence of a reduced LDL-R activity (175%) with respect to the control value; (2) in the famirv: presence of approximately 50%, of the relatives with primary hypercholesterolemia (1Ia phenotype. as per point I); evident vertical transmission of the hypercholesterolemia. presence of family history of premature CAD and/or xanthomata. and exclusion of families in which even only one member presented IIb or IV phenotypes. according to Goldstein and Brown.’ Moreover. in each patient. the presence of defective apo B-100 (mutation at position 3500) was excluded by testing probands’ DNA with specific oligonucleotides.” The study design was as follows: (1) withdrawal of all drugs for a 4-week period; (2) wash-out period of 8 weeks during which patients were placed on low cholesterol, low saturated fat diet (cholesterol
S. Fazio, G. D’Alb, R. Tiozzo, G.C. Descovich,
on
and S. Calandra
The cholesterol-lowering effect of pravastatin, a new competitive inhibitor of 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase, was studied in 10 patients with heterozygous familial hypercholesterolemia (FH). Residual low-density lipoprotein receptor (LDL-R) activity was also evaluated in cultured skin fibroblasts prior to treatment, and showed a wide range of reduction from 30% to 70% of the normal value. Treatment with pravastatin 40 mg once daily reduced total and LDL cholesterol (LDL-C) after 6 months by 19.7% and X4%, respectively (P < .OOl). Serum apolipoprotein (apo) B levels decreased significantly by 29.1% (P < .OOl). No significant changes were observed in mean serum total triglycerides or high-density lipoprotein cholesterol (HDL-C) levels. A positive correlation between residual LDL-R activity and maximum percent reduction of LDL-C levels was observed (r = .676, P i .05J. No clinically important side effects were recorded and the treatment was well tolerated. Thus, pravastatin effectively reduces LDL in heterozygous FH, and this effect appears to be related to LDL-R status. Copyright 0 1991 by W.B. Saunders Company
F
AMILIAL hypercholesterolemia (FH) is an autosomaldominant lipid disorder characterized by elevated levels of low-density lipoprotein cholesterol (LDL-C) in plasma, tendon xanthomas, and premature coronary artery disease (CAD).’ The underlying defect is a reduced number of functional cellular LDL receptors (LDL-R).’ Lowering LDL-C levels is the main goal in the treatment of these patients, since epidemiological studies and intervention trials indicate that a reduction of LDL-C is associated with a decreased incidence of CAD.’ The treatment of heterozygous FH patients is often complex, as many cases respond poorly to dietary treatment and only moderately to hypolipidemic drugs.‘,’ Over the last few years, the introduction of a new class of choiesterollowering drugs has offered new promise for the treatment of FH. These drugs, which inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme of cholesterol biosynthesis,5 lower total cholesterol and LDL-C not only by reducing cholesterol synthesis in the body,6 but also by increasing the receptor-dependent uptake of LDL.’ It is generally accepted that, by interfering with the synthesis of cholesterol in the liver, HMG-CoA reductase inhibitors would lower the intracellular concentration of cholesterol and thereby stimulate the synthesis of LDL receptors.Z.4 In animals treated with HMG-CoA reductase inhibitors, there is an increased level of LDL-R mRNA in the liver’ and an enhanced number of receptors on liver cell membranes.’ HMG-CoA reductase inhibitors were proved to be effective in lowering LDL-C in heterozygous FH,‘,” but not in
From the Cattedra di Medicina Interna e Centro Aterosclerosi. Universirtidi Boiogna, Bologna; Istitufo di Terapia Medica Sistematica, Universitcidi Roma. Roma; Squibb SPA, Roma; and rhe Istituto Patologia Generale, Vniversitri di Modena. Modena, Ita[y. Supported in part by grants of the Emilia Romagna Region (Health Research Finalized Programmes) and by the Universities of Bologna and Modena. Address reprint requests to G. D’AU, MD, Squibb SPA. Via Paolo di Dono 73, Rome, Italy. Copyright 0 1991 by W.B. Saunders Company 0086-0495191 IlOIO-0014$03.00/O 1074
receptor-negative homozygous patients.” This would suggest that the efficacy of the HMG-CoA reductase inhibitors largely depends on the presence of one functional allele at the LDL-R locus. Since many different mutations can cause defects in LDL-R protein,“.” the severity of the LDL-R defects in heterozygous FH may vary over a wide range.” If this is the case, one could presume that the variable response of FH heteroqgotes to HMG-CoA reductase inhibitors”’ is related to the receptor status of the patient (ie, residual receptor activity under basal conditions), even though other factors (apolipoprotein [apo] E phenotype, apo B structure, intestinal cholesterol absorption, etc) may play an important role. In this study, we have attempted to evaluate the possible relationship in heterozygous FH between the degree of LDL-R defect (measured in cultured skin fibroblasts) and the cholesterol-lowering effect of pravastatin, a new tissueselective HMG-CoA reductase inhibitor.”
MATEAlALS
AND METHODS
Subjects and Study Design
Ten unrelated outpatients (eight men and two women: mean age, 48.2 years) with heterozygous FH were studied. Diagnosis was based on the following criteria’: (1) in the propositus: presence of primary stable hypercholesterolemia (phenotype Ila) with LDL-C levels greater than 90th percentile of the control population (230 mg/dL) and very-low-density lipoprotein triglyceride (VLDL-TG) greater than 120 mg/dL. and presence of a reduced LDL-R activity (175%) with respect to the control value; (2) in the famirv: presence of approximately 50%, of the relatives with primary hypercholesterolemia (1Ia phenotype. as per point I); evident vertical transmission of the hypercholesterolemia. presence of family history of premature CAD and/or xanthomata. and exclusion of families in which even only one member presented IIb or IV phenotypes. according to Goldstein and Brown.’ Moreover. in each patient. the presence of defective apo B-100 (mutation at position 3500) was excluded by testing probands’ DNA with specific oligonucleotides.” The study design was as follows: (1) withdrawal of all drugs for a 4-week period; (2) wash-out period of 8 weeks during which patients were placed on low cholesterol, low saturated fat diet (cholesterol
