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Pharmacogenetic aspects in familial hypercholesterolemia with the special focus on FHMarburg (FH p.W556R)

Pharmacogenetic aspects in familial hypercholesterolemia with the special focus on FHMarburg (FH... Clin Res Cardiol Suppl (2012) 7:2–6 DOI 10.1007/s11789-012-0041-y Pharmacogenetic aspects in familial hypercholesterolemia   with the special focus on FH  (FH p.W556R) Marburg Juergen R. Schaefer · Bilgen Kurt · Alexander Sattler ·  Günter Klaus · Muhidien Soufi Published online: 28 February 2012 © The Author(s) 2012. This article is published with open access at Springerlink.com Abstract spectively. In contrast, two affected homozygote p.W556R  Objective Familial hypercholesterolemia (FH) is an auto- FH patients, in the mean time undergoing LDL apheresis,  somal dominant inherited disorder caused by mutations in  had no response to statin but a 15% LDL cholesterol de- the low density lipoprotein receptor (LDLR) gene. FH is  crease on ezetimibe monotherapy. characterized by elevated plasma LDL cholesterol, prema- Conclusions The LDLR mutation p.W556R is a frequent  ture atherosclerosis, and a high risk of premature myocar- and severe class II defect for FH. The affected homozygote  dial infarction. In general, mutations within LDLR gene  FH patients have a total loss of the functional LDLR and— can cause five  different classes of defects, namely: class I  as expected—do not respond on statin therapy and require  defect: no LDLR synthesis; class II defect: no LDLR trans- LDL apheresis. In contrast, heterozygote FH patients with  port; class III defect: no low density lipoprotein (LDL) to  the same LDLR defect respond exceedingly well to stand- LDLR binding; class IV defect: no LDLR/LDL internaliza- ard lipid-lowering therapy, illustrating that the knowledge  tion; and class V defect: no LDLR recycling. One might  of the primary LDLR defect enables us to foresee the ex- expect that both the class of LDLR defect as well as the  pected drug effects. precise mutation influences  the severity of hypercholeste- Keywords Familial hypercholesterolemia ·  rolemia on one hand and the response on drug treatment  on the other. To clarify this question we studied the ef- Low density lipoprotein receptor (LDLR) ·   Statin treatment · LDL apheresis fect of the LDLR mutation p.W556R in two heterozygote  subjects. Results We found that two heterozygote FH patients with  the LDLR mutation p.W556R causing a class II LDLR de- Introduction fect (transport defective LDLR) respond exceedingly well  to the treatment with simvastatin 40 mg/ezetimibe 10 mg.  The LDL receptor (LDLR) is an essential receptor for the  There was a LDL cholesterol decrease of 55 and 64%, re- uptake of low density lipoprotein (LDL) and accounts for  the clearance of 70% of all plasma-circulating LDL [1].  LDLR/LDL  complexes  are  internalized  by  endocytosis,  J. R. Schaefer ( ) mainly in hepatocytes and ligand dischargement in the aci- Department of Internal Medicine, Cardiology,   Philipps-University, Baldingerstr.1, 35033 Marburg,   dic environment of the endosome enables the recycling of  Germany LDL receptors for another round of LDL binding [1–3]. e-mail: juergen.schaefer@uni-marburg.de The term “familial hypercholesterolemia” (FH) is gene- rally used for LDLR deficiency  which is inherited as an  B. Kurt · A. Sattler · M. Soufi Department of Internal Medicine, Cardiology,   autosomal dominant trait. Homozygous LDLR deficiency  is  Philipps-University, Marburg, Germany rare, with a frequency of 1 per million in the general popu- lation [4, 5]. It is characterized by severely elevated LDL  G. Klaus cholesterol  (> 15.5  mmol/L;  > 600  mg/dL).  The  clinical  Department of General Pediatrics, Philipps-University, Marburg,  Germany symptoms are xanthomas, thickened achilles tendons, caro- 1 3 LDL Pharmacogenetic aspects in familial hypercholesterolemia with the special focus on FH  (FH p.W556R) 3 Marburg tis and coronary artery stenosis, and aortic valve stenosis  binding. Class IV mutations produce LDL receptors with  that develop in the first  decade of life, leading to prema- normal transport and cell surface LDL binding but defective  ture death from stroke or myocardial infarction in child- clustering in clathrin-coated pits for internalization. Finally,  hood. The molecular basis of FH has been elucidated by  class V mutations produce recycling defective receptors that  the fundamental work of Goldstein and Brown and Rader  internalize normally, but are unable to release bound ligand  et al. [6, 7]. They revealed that defects of the LDL receptor  within the acidic environment of the endosome, and thus do  are caused by mutations within the LDL receptor gene. The  not recycle to the cell surface [12] (Fig. 1a). LDLR is located on chromosome 19 [8]. Worldwide, more  than 1,000 FH causing LDLR gene mutations ranging from  single nucleotide substitutions to extended deletions had  Methods been identified  in different ethnic groups [9–11]. According to the nature and location of the mutations  Lipid profiles within the LDLR gene, five  different classes of FH-cau- sing mutations have been defined.  Class I mutations include  Lipid analysis was performed from plasma drawn under fas- null alleles with no detectable LDL receptor protein. Class  ting conditions (fasting period of at least 12 h) without any  II  mutations  produce  transport-defective  LDLR  proteins  lipid-lowering medication and was repeated after 6 weeks  that are either completely (class II a) or partially blocked  treatment with simvastatin 40 mg and ezetimibe 10 mg as a  (class II b or leaky LDLRs) in their transport from the endo- single tablet given once daily. Total cholesterol and trigly- plasmic reticulum to the Golgi apparatus due to impaired  cerides were measured enzymatically (Roche Diagnostics,  glycosylation [12]. Class III mutations encode LDL recep- Mannheim, Germany). High-density lipoprotein (HDL) was  tors with normal intracellular transport but defective LDL  measured after the precipitation of apoB-containing lipo-              Class I - V defects in FH Het. Class I or II defect in FH Note: only normal functioning LDLR appear at the cell surface (at a lesser degree) LDL LDL LDL LDL LDL LDL Class IV Class III LDL No internalization No binding Class II Golgi LDL No transport Golgi Class I http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Clinical Research in Cardiology Supplements Springer Journals

Pharmacogenetic aspects in familial hypercholesterolemia with the special focus on FHMarburg (FH p.W556R)

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Publisher
Springer Journals
Copyright
Copyright © 2012 by The Author(s)
Subject
Medicine & Public Health; Diagnostic Radiology; Angiology; Internal Medicine; Cardiac Surgery; Cardiology
ISSN
1861-0706
eISSN
1861-0714
DOI
10.1007/s11789-012-0041-y
pmid
22528129
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Abstract

Clin Res Cardiol Suppl (2012) 7:2–6 DOI 10.1007/s11789-012-0041-y Pharmacogenetic aspects in familial hypercholesterolemia   with the special focus on FH  (FH p.W556R) Marburg Juergen R. Schaefer · Bilgen Kurt · Alexander Sattler ·  Günter Klaus · Muhidien Soufi Published online: 28 February 2012 © The Author(s) 2012. This article is published with open access at Springerlink.com Abstract spectively. In contrast, two affected homozygote p.W556R  Objective Familial hypercholesterolemia (FH) is an auto- FH patients, in the mean time undergoing LDL apheresis,  somal dominant inherited disorder caused by mutations in  had no response to statin but a 15% LDL cholesterol de- the low density lipoprotein receptor (LDLR) gene. FH is  crease on ezetimibe monotherapy. characterized by elevated plasma LDL cholesterol, prema- Conclusions The LDLR mutation p.W556R is a frequent  ture atherosclerosis, and a high risk of premature myocar- and severe class II defect for FH. The affected homozygote  dial infarction. In general, mutations within LDLR gene  FH patients have a total loss of the functional LDLR and— can cause five  different classes of defects, namely: class I  as expected—do not respond on statin therapy and require  defect: no LDLR synthesis; class II defect: no LDLR trans- LDL apheresis. In contrast, heterozygote FH patients with  port; class III defect: no low density lipoprotein (LDL) to  the same LDLR defect respond exceedingly well to stand- LDLR binding; class IV defect: no LDLR/LDL internaliza- ard lipid-lowering therapy, illustrating that the knowledge  tion; and class V defect: no LDLR recycling. One might  of the primary LDLR defect enables us to foresee the ex- expect that both the class of LDLR defect as well as the  pected drug effects. precise mutation influences  the severity of hypercholeste- Keywords Familial hypercholesterolemia ·  rolemia on one hand and the response on drug treatment  on the other. To clarify this question we studied the ef- Low density lipoprotein receptor (LDLR) ·   Statin treatment · LDL apheresis fect of the LDLR mutation p.W556R in two heterozygote  subjects. Results We found that two heterozygote FH patients with  the LDLR mutation p.W556R causing a class II LDLR de- Introduction fect (transport defective LDLR) respond exceedingly well  to the treatment with simvastatin 40 mg/ezetimibe 10 mg.  The LDL receptor (LDLR) is an essential receptor for the  There was a LDL cholesterol decrease of 55 and 64%, re- uptake of low density lipoprotein (LDL) and accounts for  the clearance of 70% of all plasma-circulating LDL [1].  LDLR/LDL  complexes  are  internalized  by  endocytosis,  J. R. Schaefer ( ) mainly in hepatocytes and ligand dischargement in the aci- Department of Internal Medicine, Cardiology,   Philipps-University, Baldingerstr.1, 35033 Marburg,   dic environment of the endosome enables the recycling of  Germany LDL receptors for another round of LDL binding [1–3]. e-mail: juergen.schaefer@uni-marburg.de The term “familial hypercholesterolemia” (FH) is gene- rally used for LDLR deficiency  which is inherited as an  B. Kurt · A. Sattler · M. Soufi Department of Internal Medicine, Cardiology,   autosomal dominant trait. Homozygous LDLR deficiency  is  Philipps-University, Marburg, Germany rare, with a frequency of 1 per million in the general popu- lation [4, 5]. It is characterized by severely elevated LDL  G. Klaus cholesterol  (> 15.5  mmol/L;  > 600  mg/dL).  The  clinical  Department of General Pediatrics, Philipps-University, Marburg,  Germany symptoms are xanthomas, thickened achilles tendons, caro- 1 3 LDL Pharmacogenetic aspects in familial hypercholesterolemia with the special focus on FH  (FH p.W556R) 3 Marburg tis and coronary artery stenosis, and aortic valve stenosis  binding. Class IV mutations produce LDL receptors with  that develop in the first  decade of life, leading to prema- normal transport and cell surface LDL binding but defective  ture death from stroke or myocardial infarction in child- clustering in clathrin-coated pits for internalization. Finally,  hood. The molecular basis of FH has been elucidated by  class V mutations produce recycling defective receptors that  the fundamental work of Goldstein and Brown and Rader  internalize normally, but are unable to release bound ligand  et al. [6, 7]. They revealed that defects of the LDL receptor  within the acidic environment of the endosome, and thus do  are caused by mutations within the LDL receptor gene. The  not recycle to the cell surface [12] (Fig. 1a). LDLR is located on chromosome 19 [8]. Worldwide, more  than 1,000 FH causing LDLR gene mutations ranging from  single nucleotide substitutions to extended deletions had  Methods been identified  in different ethnic groups [9–11]. According to the nature and location of the mutations  Lipid profiles within the LDLR gene, five  different classes of FH-cau- sing mutations have been defined.  Class I mutations include  Lipid analysis was performed from plasma drawn under fas- null alleles with no detectable LDL receptor protein. Class  ting conditions (fasting period of at least 12 h) without any  II  mutations  produce  transport-defective  LDLR  proteins  lipid-lowering medication and was repeated after 6 weeks  that are either completely (class II a) or partially blocked  treatment with simvastatin 40 mg and ezetimibe 10 mg as a  (class II b or leaky LDLRs) in their transport from the endo- single tablet given once daily. Total cholesterol and trigly- plasmic reticulum to the Golgi apparatus due to impaired  cerides were measured enzymatically (Roche Diagnostics,  glycosylation [12]. Class III mutations encode LDL recep- Mannheim, Germany). High-density lipoprotein (HDL) was  tors with normal intracellular transport but defective LDL  measured after the precipitation of apoB-containing lipo-              Class I - V defects in FH Het. Class I or II defect in FH Note: only normal functioning LDLR appear at the cell surface (at a lesser degree) LDL LDL LDL LDL LDL LDL Class IV Class III LDL No internalization No binding Class II Golgi LDL No transport Golgi Class I

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Clinical Research in Cardiology Supplements – Springer Journals

Published: Feb 28, 2012

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