Cholesteryl Ester Transfer Protein Deficiency Research Articles

Cholesteryl ester transfer protein deficiency is correlated with thyroid disease.

We investigated whether cholesteryl ester transfer protein (CETP) deficiency is a risk factor for atherosclerosis or other disease. Ninety-seven individuals with increased levels of high density lipoprotein-cholesterol (HDL-C) (≥85mg/dl) were selected. CETP deficiency was assessed in all 97 subjects by polymerase chain reaction (PCR) and either single stranded conformation polymorphism (SSCP) or restriction fragment length polymorphism (RFLP). Of the 97 subjects, 7 (7%) were heterozygous for the intron 14 splicing defect, which decreases CETP activity, and 9 (9%) were heterozygous for D442G missense mutation, which has no effect on CETP activity. One patient was found to be a compound heterozygote for the intron 14 and D442G mutations. These mutations were found in only 3 atherosclerotic patients; 2 carried the D442G mutation, and 1 had the intron 14 mutation. Although CETP activity was not associated with atherosclerosis, we discovered a novel relation between CETP gene mutations and thyroid gland disorders. Specifically, 5 of 7 subjects with CETP gene intron 14 mutation had thyroid disease. Regarding the D442G mutation, there was no difference between subjects with and without thyroid disease. It is possible that CETP activity affects thyroid function.

Roles of plasma lipid transfer proteins in reverse cholesterol transport.

Plasma lipid transfer proteins include plasma cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP). Plasma CETP facilitates the transfer of cholesteryl ester (CE) from high-density lipoprotein (HDL) to apolipoprotein (apo) B-containing lipoproteins, and is a key protein in reverse cholesterol transport which protects vessel walls from atherosclerosis. The importance of plasma CETP in lipoprotein metabolism was highlighted by the discovery of CETP-deficient subjects with a marked hyperalphalipoproteinemia (HALP). The deficiency of CETP causes various abnormalities in the concentration, composition, and functions of both HDL and low-density lipoprotein (LDL). Although the significance of CETP in terms of atherosclerosis has been controversial, the in vitro evidence showed that large CE-rich HDL particles in CETP deficiency are defective in cholesterol efflux. Recent epidemiological studies in Japanese-Americans and in Omagari area where HALP subjects with the intron 14 splicing defect of CETP gene are markedly frequent, have demonstrated an increased incidence of coronary atherosclerosis in CETP-deficient patients. Similarly, scavenger receptor BI (SR-BI) knockout mice show a marked increase in HDL-cholesterol but accelerated atherosclerosis in atherosclerosis-susceptible mice. Thus, CETP deficiency is a state of impaired reverse cholesterol transport which may possibly lead to the development of atherosclerosis. PLTP transfers phospholipids from triglyceride (TG)-rich lipoproteins to HDL during lipolysis. Human plasma PLTP has a 20% sequence homology to human CETP and human PLTP gene has a marked similarity in the exon-intron organization. Both CETP and PLTP belong to the lipid transfer/lipopolysaccharide binding protein (LBP) gene family, which also includes LBP and bactericidal/permeability-increasing protein (BPI). Although these 4 proteins possess different physiological functions, they share marked biochemical similarities. The current review will also focus on the molecular genetics and function of plasma lipid transfer proteins, including CETP and PLTP.

Pros and cons of inhibiting cholesteryl ester transfer protein.

Whether or not it is desirable to inhibit cholesteryl ester transfer protein (CETP) has been an important question for over fifteen years since genetic CETP deficiency was found. Recently, some epidemiological studies which have been reported in Japan as well as Western countries help to clarify the atherogenicity of human subjects with mutations or polymorphisms in the CETP gene. In addition, some experimental atherosclerosis studies, in which CETP was inhibited in rabbits with different approaches, have been reported. There was a considerable difference in the atherogenicity of human CETP deficiency and CETP-inhibited rabbits. In this review, we summarize the recent advances in this field as well as discussing the significance of CETP in reverse cholesterol transport, a major protective system against atherosclerosis.

Particle size analysis of high density lipoproteins in patients with genetic cholesteryl ester transfer protein deficiency

We investigated the detailed distribution of high-density lipoproteins (HDL) particle size in patients with cholesteryl ester transfer protein (CETP) deficiency. Serum samples pre-stained with Sudan black B were electrophoresed using 4–30% polyacrylamide gradient gels, and the Stokes diameter of HDL particles was determined in 23 patients with genetic CETP deficiency, nine patients with hyperalphalipoproteinemia and seven subjects with normal HDL cholesterol concentrations. The mean Stokes diameter of HDL particles in CETP deficient patients (11.2±0.6 nm) was significantly greater than hyperalphalipoproteinemia (10.7±0.3 nm, P<0.05) and normal subjects (9.5±0.4 nm, P<0.01). A significant relationship was found between mean HDL size and serum CETP mass concentrations ( P<0.05). When the particle size of all detected HDL bands was investigated, extra-large HDL particles larger than 12 nm were found in 14 of the 23 patients with CETP deficiency, which were not found in any of the hyperalphalipoproteinemia patients or normal subjects. Serum low-density lipoproteins (LDL) cholesterol and total cholesterol concentrations were lower in CETP deficiencies with extra-large HDL particles than those in non-carriers ( P<0.01). These results indicate that extra-large HDL may be an index to clarify the relationship between genetic CETP deficiency and atherosclerosis.

Marked elevation in serum apolipoprotein E in a case of heterozygous cholesteryl ester transfer protein deficiency

The subject was a 57-year-old Japanese woman with a body mass index of 21.2 kg m −2. Her serum total cholesterol (TC), triglycerides (TG) and HDL-cholesterol levels were 7.11 mmol l −1, 0.53 mmol l −1 and 2.05 mmol l −1, respectively. She had a marked increase of serum apolipoprotein (Apo) E concentration of 25 mg dl −1 with normal concentrations of serum Apo A-I, A-II, B, C-II and C-III. Polymerase chain reaction–restriction fragments length polymorphism analysis of the cholesteryl ester transfer protein (CETP) gene from this subject revealed the heterozygous nucleotide change causing a Asp442 to Gly substitution (D442G) in the CETP protein. For comparison, 11 unrelated female subjects with this mutation (age, 57±5.1 years; BMI, 22±1.5 kg m −2; TC, 7.23±1.16 mmol l −1; TG, 1.44±0.80 mmol l −1; HDL-C, 2.47±0.53 mmol l −1) were found to have a serum Apo E concentration of 7±1.5 mg dl −1, about a third of the patient’s concentration. The lipoprotein profile of the proband’s serum analyzed by disk polyacrylamide gel electrophoresis showed a trace amount of VLDL. A vitamin A fat-loading test showed little increase in serum triglycerides and retinyl palmitate levels compared with control subjects at 2, 4 and 6 h after fat loading. Ultracentrifugation analysis of her serum revealed no detectable Apo E in the VLDL fraction but showed a large amount of Apo E in the HDL fraction, in contrast to a normal control, who had Apo E in the VLDL fraction as well as in the HDL fraction. Sequence analysis of the Apo E gene from the subject showed no nucleotide changes in exon 3 and exon 4, which code the mature Apo E protein, indicating there is no structural abnormality in the Apo E protein. Direct sequence analysis of the LDL receptor gene also did not show any nucleotide change. Based on these findings, it was hypothesized that the marked increase of Apo E in the patient’s serum was caused by a decreased transfer of Apo E from HDL particles to TG-rich lipoproteins or impaired uptake of Apo E-containing HDL by LDL receptor or remnant receptor, due presumably to a dysfunction of these receptors in the patient.

Phenotypic expression and pathophysiology of genetic cholesteryl ester transfer protein deficiency

Phenotypic expression and pathophysiology of genetic cholesteryl ester transfer protein deficiency

A novel molecular basis for genetic cholesteryl ester transfer protein (CETP) deficiency — G to A mutation in consensus ETS binding site at the promoter region of CETP gene

A novel molecular basis for genetic cholesteryl ester transfer protein (CETP) deficiency — G to A mutation in consensus ETS binding site at the promoter region of CETP gene

Clinical and molecular characteristics of homozygous CETP deficiency

Clinical and molecular characteristics of homozygous CETP deficiency

1999 George Lyman Duff memorial lecture: lipid transfer proteins, HDL metabolism, and atherogenesis.

Plasma high density lipoprotein (HDL) levels show an inverse relationship to atherogenesis, in part reflecting the role of HDL in mediating reverse cholesterol transport. The transfer of HDL cholesterol to the liver involves 3 catabolic pathways: the indirect, cholesteryl ester transfer protein (CETP)-mediated pathway, the selective uptake (scavenger receptor BI) pathway, and a particulate HDL uptake pathway. The functions of the lipid transfer proteins (CETP and phospholipid transfer protein) in HDL metabolism have been elucidated by genetic approaches in humans and mice. Human CETP deficiency is associated with increased HDL levels but appears to increase coronary artery disease risk. Phospholipid transfer protein deficiency, produced by gene knockout in mice, results in decreased HDL levels, reflecting decreased transfer of phospholipids from triglyceride-rich lipoproteins into HDL. Obese (ob/ob) mice have markedly increased HDL levels and represent an interesting model of defective HDL catabolism in the liver. In hepatocytes of wild-type mice, there is extensive uptake and resecretion of HDL and selective uptake of cholesteryl ester from HDL during recycling. In ob/ob mice, these processes are defective, suggesting that HDL recycling plays an important role in holo-HDL catabolism, selective uptake, and the determination of plasma HDL levels.

Secretion of preβ HDL increases with the suppression of cholesteryl ester transfer protein in Hep G2 cells

Preβ HDL are small, protein rich lipoproteins that are predominantly composed of apo A-I, without apo A-II. Preβ HDL are secreted from the liver as nascent HDL and/or are produced in the incubated plasma by cholesteryl ester transfer protein (CETP). However, the role of CETP in the secretion of HDL from the liver has yet to be determined. In the present study, we examined the effect of the suppression of hepatic CETP by antisense oligodeoxynucleotides (ODNs) against CETP targeted to the liver on the secretion of apo A-I using a Hep G2 cell culture. The ODNs against CETP were coupled to asialoglycoprotein (ASOR) carrier molecules, which serve as an important method for the regulation of liver gene expression. Hep G2 cells were cultured in DMEM supplemented with 10% FBS. After 2 days, the medium was changed to DMEM with EGF and the cells were divided into three groups. The control group received saline, while the sense group was mixed with the sense ODNs complex and the antisense group was mixed with the antisense ODNs complex, respectively, for 2 days. Both the hepatic CETP mRNA and the CETP mass in the medium in the antisense group decreased significantly more than in the sense and the control groups (CETP mass: 1.697±0.410 ng/mg cell protein vs. 2.367±0.22 and 2.360±0.139, n=3 in each determination). In contrast, both the hepatic apo A-I mRNA and the apo A-I mass in the medium in the antisense group were significantly higher than those in the sense and the control groups (apo A-I mass; 1.877±0.215 μg/mg cell protein vs. 1.213±0.282 and 1.097±0.144, n=3 in each determination). The increase in apo A-I was mainly due to the increase in preβ apo A-I. These findings may partly explain why HDL and apo A-I increase in patients with CETP deficiency, while also indicating the possibility that the original level of preβ HDL is sufficient in such patients.

7. Lipid transfer proteins and receptors in HDL metabolism

Plasma high density lipoprotein (HDL) levels are determined both by intravascular metabolism and by clearance pathways. Recent evidence indicates that plasma lipid transfer proteins play a major role in the intravascular metabolism of HDL, while HDL receptors in tissues are important in HDL catabolism. The role of the plasma lipid transfer proteins, cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP), have been elucidated by genetic deficiency states in humans or mice, or by overexpression experiments in mice. Human CETP deficiency results in increased HDL levels, but also increased coronary heart disease, suggesting an anti-atherogenic function of CETP related to its role in reverse cholesterol transport. PLTP knock-out mice have absent plasma phospholipid transfer activity and markedly reduced HDL cholesterol and apoA-I levels, demonstrating the crucial role that the transfer of surface phospholipid of triglyceride-rich lipoproteins plays in the maintenance of HDL levels. Scavenger receptor BI has recently emerged as an authentic HDL receptor mediating the selective uptake of HDL CE in liver and steroidogenic tissue. Overexpression of SR-BI in transgenic mice results in low HDL levels, and also decreases VLDL and LDL cholesterol and apoB levels, and reduces atherosclerosis in response to a high cholesterol/bile salt diet. Knock-out of SR-BI results in increased HDL levels due to decreased selective uptake in the liver, but the catabolism of HDL proteins is unaltered. Recent studies in obese (ob/ob) mice show a catabolic defect of HDL protein in the liver and suggest a leptin-regulated liver catabolic process for apoA-I and apoA-II. Thus, while CETP, PLTP and SR-BI are important in the turnover of HDL lipids, it appears that distinct receptors are involved in the catabolism of HDL proteins.

A Novel Mutation in the Human Plasma Cholesteryl Ester Transfer Protein (CETP) Gene Leading to CETP-Deficiency in a Nova Scotian Patient: A Review of CETP Deficiency

Human Cholesteryl Ester Transfer Protein (CETP) is a 476-residue hydrophobic plasma glycoprotein which catalyzes the hetero-exchange and net mass transfer of cholesteryl esters and triacylglycerols between plasma High Density Lipoprotein (HDL) and Very Low Density (VLDL) and Low Density Lipoproteins (LDL). CETP, together with the plasma enzyme Lecithin:Cholesterol Acyltransferase (LCAT), form integral parts of the Reverse Cholesterol Transport pathway by which cholesterol is removed from peripheral tissues and transported back to the liver for excretion or reutilization. We have recently identified a novel mutation (CT) at nucleotide 836 in Exon 9 of the Cholesteryl Ester Transfer Protein gene from a Caucasian subject resident in Nova Scotia. The patient is homozygous for the mutation which results in the conversion of 268 Arg into a STOP codon and a truncated, dysfunctional protein. This patient is the first Caucasian North American subject reported to have CETP deficiency. The majority of other subjects are of Japanese ancestry. Biochemically, homozygous CETP deficiency is characterized by a moderate hypercholesterolemia (7±0.8 mmol/L) entirely attributable to an elevated HDL cholesterol (4.2±1.0 mmol/L). LDL cholesterol is usually low (2±0.8 mmol/L). Lipoprotein composition is markedly altered with the HDL much larger, cholesteryl ester enriched and triglyceride poor: the LDL is polydisperse. triglyceride enriched, with a lower proportion of cholesteryl ester per particle. The VLDL is similarly cholesteryl ester poor. Here we review the structure and function of CETP. the consequences of CETP deficiency and hence its diagnosis and discuss the current opinions concerning the atherosclerotic risk associated with CETP deficiency and thus the advisability of treating this disorder with cholesterol lowering drugs. Normal 0 false false false EN-CA X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Normal 0 false false false EN-CA X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Normal 0 false false false EN-CA X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

A Low Prevalence of Coronary Heart Disease among Subjects with Increased High-Density Lipoprotein Cholesterol Levels, Including Those with Plasma Cholesteryl Ester Transfer Protein Deficiency

Background.Use of genetic analysis may improve the predictive value of risk factors for disease. A high plasma level of high-density lipoprotein (HDL) cholesterol is a strong negative risk factor for coronary heart disease (CHD). Cholesteryl ester transfer protein (CETP) deficiency causes increased levels of HDL cholesterol. However, recent studies suggest that CETP deficiency is a risk factor for CHD despite elevated HDL cholesterol levels.Methods.Plasma lipid levels, CHD prevalence, resting electrocardiograms, and common CETP gene mutations were analyzed cross-sectionally in a population of 19,044 male and 29,487 female Japanese subjects (ages 45–79 years).Results.High HDL cholesterol levels (serum HDL cholesterol ≥80 mg/dl, ≥95th percentile) were found in 6 and 5% of Japanese men and women, respectively. In the group with HDL cholesterol ≥80 mg/dl, common CETP gene mutations were identified in 23–24% of men and 31–49% of women. The prevalence of CHD in the group with high HDL cholesterol (≥80 mg/dl) was low among both men (1.0%) and women (1.3%). There was no difference in CHD prevalence between hyper-HDL-cholesterolemic subjects with and without CETP mutations.Conclusions.Subjects with very high HDL levels (HDL cholesterol ≥80 mg/dl) as well as mild-to-moderate HDL elevations (60–79 mg/dl) appear to be protected against CHD, whether or not they have CETP deficiency, a genetic cause of elevated HDL.

Hyperalphalipoproteinemia: Characterization of a cardioprotective profile associating increased high-density lipoprotein 2 levels and decreased hepatic lipase activity

The aim of the present study was to investigate the high-density lipoprotein (HDL) strucutral characteristics and metabolism in hyperalphalipoproteinemic (HALP) patients (HDL-cholesterol) [HDL-C], 92 ± 14 mg/dL) with combined elevated low-density lipoprotein-cholesterol (LDL-C) levels (LDL-C, 181 ± 33 mg/dL). Patients were subjected to a complete cardiovascular examination, including ultrasonographic investigation of carotid arteries. Two HALP profiles were identified according to the HDL 2 HDL 3 ratio. HALP profile A was characterized in 28 patients by increased HDL 2 HDL 3 ratio, HDL 2b, and lipoprotein (Lp)A-I levels compared with normolipidemic subjects, and HALP profile B, including the 12 remaining patients, was characterized by a HDL 2 HDL 3 ratio within the normal range and by the increase of all HDL subclasses (HDL 2b,2a,3a,3b,3c). LPA-I, and LpA-I:A-II levels. With regard to the exploration of carotid arteries, in HALP profile A, 20 patients were free from lesions and eight had only intimal wall thickening. In HALP profile B, only one patient was free from lesions, four had intimal wall thickening, and seven displayed plaques, but none had stenosis. Taking into account the number of patients with plaques within each group, HALP profile A was associated with a low prevalence of atherosclerotic lesions, whereas HALP profile B was less cardioprotective (odds ratio, 77.7 [95% confidence interval, 3.7 to 1,569.7]; P < .0001). For both HALP profiles, cholesteryl ester transfer protein (CETP) deficiency was discarded and activities of phospholipid transfer protein (PLTP) and lipoprotein lipase (LPL) were normal. However, hepatic lipase (HL) activity was significantly decreased in HALP profile A, but within the normal range for HALP profile B. In conclusion, an HALP profile A with a low prevalence of atherosclerosis was characterized by an increased HDL 2 HDL 3 , HDL 2b, and LpA-I levels associated with decreased HL activity.

Plasma lipid transfer proteins, high-density lipoproteins, and reverse cholesterol transport.

Cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP) are members of the lipid transfer/lipopolysaccharide binding protein gene family. Recently, the crystal structure of one of the members of the gene family, bactericidal permeability increasing protein, was solved, providing potential insights into the mechanisms of action of CETP and PLTP. These molecules contain intrinsic lipid binding sites and appear to act as carrier proteins that shuttle between lipoproteins to redistribute lipids. The phenotype of human CETP genetic deficiency states and CETP transgenic mice indicates that CETP plays a major role in the catabolism of high-density lipoprotein (HDL) cholesteryl esters and thereby influences the concentration, apolipoprotein content, and size of HDL particles in plasma. PLTP also appears to have an important role in determining HDL levels and speciation. Recent data indicate that genetic CETP deficiency is associates with an excess of coronary heart disease in humans, despite increased HDL levels. Also, CETP expression is anti-atherogenic in many mouse models, even while lowering HDL. These data tend to support the reverse cholesterol transport hypothesis, i.e., that anti-atherogenic properties of HDL are related to its role in reverse cholesterol transport. Recently, another key molecule involved in this pathway was identified, scavenger receptor BI; this mediates the selective uptake of HDL cholesteryl esters in the liver and thus constitutes a pathway of reverse cholesterol transport parallel to that mediated by CETP. Reflecting its role in reverse cholesterol transport, the CETP gene is up-regulated in peripheral tissues and liver in responses to dietary or endogenous hypercholesterolemia. An analysis of the CETP proximal promoter indicates that it contains sterol regulatory elements highly homologous to those present in 3-hydroxy-3-methylglutaryl-coenzyme A reductase; the CETP gene is transactivated by the binding of SREBP-1 to these elements. A challenge for the future will be the manipulation of components of the reverse cholesterol transport pathway, such as CETP, PLTP, or scavenger receptor BI for therapeutic benefit.

Characterization of two HDL subfractions and LpA-I, LpA-I:A-II distribution profiles and clinical characteristics of hyperalphalipoproteinemic subjects without cholesterol ester transfer protein deficiency.

The aims of the present study were (i) to characterize the HDL2, HDL3 and the LpA-I, LpA-I:A-II distribution, (ii) to investigate the prevalence of atherosclerotic lesions and (iii) to assess the activity of cholesteryl ester transfer protein (CETP) in 29 hyperalphalipoproteinemic (HALP) patients (HDL-C=90+/-11 mg/dl) with combined hypercholesterolemia (LDL-C=180+/-16 mg/dl). According to the HDL2/HDL3 and LpA-I/LpA-I:A-II ratios, two HALP profiles (A and B) were defined: in 22 patients (HALP profile A) these ratios were increased compared to the normolipidemic control subjects (1.19+/-0.11 versus 0.53+/-0.19, P < 0.001 and 1.01+/-0.2 versus 0.51+/-0.25, P < 0.001, respectively) and in seven patients (HALP profile B) these ratios were within the normal range (0.64+/-0.20 and 0.69+/-0.2, respectively). The atherosclerotic lesions were assessed by ultrasonography of the carotid arteries. Amongst patients with HALP profile A, 17 were free from lesions, five had intimal wall thickening and none displayed plaques, whereas for patients within the HALP profile B, only one was free from lesions, two had intimal wall thickening and four displayed plaques. CETP activities (348+/-116 versus 371+/-75%/ml/h) and CETP concentrations (2.4+/-0.5 versus 2.5+/-0.6 microg/ml) were similar in HALP profiles A and B, however these values were both higher than in control subjects (190+/-40%/ml/h, P < 0.001 and 1.8+/-0.3 microg/ml, P < 0.001, respectively). Hence the hyperalphalipoproteinemic profiles (A and B) described here were not related to CETP deficiency. In conclusion, the HALP profile A was characterized by both increased HDL2/HDL3 and LpA-I/LpA-I:A-II ratios and was associated with a low prevalence of atherosclerosis, whereas the HALP profile B, characterized by HDL2/HDL3 and LpA-I/LpA-I:A-II ratios within the normal range, was less cardioprotective.

Enzyme immunoassay for cholesteryl ester transfer protein in human serum

We developed a new simple sandwich-type enzyme immunoassay to measure cholesteryl ester transfer protein (CETP) mass in human serum. In assay validation, Intra- and Inter-assay coefficients of variation were 2.7 to 5.7% and 2.2 to 12.2%, respectively. There was no cross-reactivity with various lipoproteins (apo A-I, apo A-II, apo B, apo C-III). A good correlation between CETP mass and CETP activity (n=46, correlation coefficient=0.88) was observed. This assay provided a specific and reproducible method for measuring CETP mass in samples. The average value of CETP in the normal sera of 41 males was 1.8±0.6 μg/ml (mean±S.D.) and that of 37 females was 2.0±0.5 μg/ml. In the study of patients with the CETP gene mutation (Int 14A and D442G), our results on the value of plasma CETP mass reflected to genetic CETP deficiency. In conclusion, this assay for CETP mass in human serum may be a useful tool for clinical investigations involving lipid metabolism related to disease.

Human plasma CETP deficiency: identification of a novel mutation in exon 9 of the CETP gene in a Caucasian subject from North America

Human plasma cholesteryl ester transfer protein (CETP) is a 476-residue hydrophobic glycoprotein that catalyzes the heterotransfer of cholesteryl esters and triacylglycerols among lipoproteins: Mutations in the CETP gene have been identified, mostly in the Japanese population. These mutations result in hypercholesterolemia due to the presence of large cholesteryl ester-rich HDL particles, elevated plasma apoA-I and apoE, and reduced apoB levels. Here we report the plasma lipoprotein phenotype and molecular defect in a 57-year-old female Nova Scotian subject lacking Japanese ancestry who is homozygous for a novel mutation in the CETP gene. Her total plasma cholesterol was 7.3 mmol/l with an LDL cholesterol of 2.9 mmol/l and HDL cholesterol of 4.4 mmol/l. She was mildly hypertriglyceridemic (1.6 mmol/l) and had markedly elevated apoA-I (256 mg/dl) and apoE (14.4 mg/dl) with only slightly reduced apo/B levels (94 mg/dl). Her VLDL and LDL were cholesteryl ester-poor (1.8 and 37.2% of lipids, respectively) and triacylglycerol-rich (67.3 and 18.9% of lipids, respectively) while her HDL was cholesteryl ester-rich (40.2–45.7% of lipids) and triacylglycerol-poor (3.3–2.5% of lipids). No plasma CETP activity or mass was detected. Bi-directional DNA sequence analysis of PCR products from all 16 exons showed a single base substitution (C→T at nucleotide 836 in exon 9 resulting in 268 Arg→STOP) in both alleles. No other mutation was detected. A single base mismatched, 26 bp reverse PCR primer that produced a single Mae III RFLP site upon amplification of the mutated DNA sequence was designed for rapid population screening. This subject is, we believe, the first Caucasian North American patient reported to have CETP deficiency.—Teh, E. M., P. J. Dolphin, W. C. Breckenridge, and M–H. Tan. Human plasma CETP deficiency: identification of a novel mutation in exon 9 of the CETP gene in a Caucasian subject from North America.

CETPと動脈硬化

Heterozygous CETP deficiency is found in ∼10% of the general Japanese population, and is an important genetic factor of increased HDL levels. A crosssectional epidemiologic survey in Kochi prefecture showed that subjects with very high HDL cholesterol levels≥80mg/dl exhibit a low CHD prevalence, irrespective of the CETP genotype. The cholesterol esterification rate was decreased in both homo- and heterozygous CETP deficiency. Increased levels of HDL itself, along with low non-HDL cholesterol levels, manifest anti-atherogenicity in subjects with very high HDL levels and CETP deficiency, possibly through direct effects of HDL on the arterial wall or an antioxidative mechanism. However, normolipidemic elderly men with low-to-intermediate HDL-C levels (<60mg/dl) and a D442G mutation, demonstrated ischemic ST-T change 3times more frequently. Thus, antiatherogenicity of CETP deficiency is dependent on serum HDL-C levels, and CETP genotyping/serum CETP measurement may be useful to identify a high-risk grop in subjects with serum HDL-C<60mg/dl.

Deficiency of Cholesteryl Ester Transfer Protein

A patient is described who exhibited, despite excessively high postprandial triglyceride levels, high levels of HDL cholesterol. Measurement of CETP activity and mass in the patient's plasma showed values of less than 5% and 2%, respectively, of a normolipidemic plasma pool. The CETP cDNA of the patient exhibited a mutation (T-->G), turning codon 57 (TAT) of exon 2 into a stop codon (TAG) and abolishing a, XcmI restriction site. Digestion of directly amplified CETP cDNA from the patient with XcmI indicated the exclusive presence of CETP cDNA containing the mutation. Analysis of the corresponding region of the CETP gene indicated the patient to be heterozygous for the nonsense mutation at codon 57, a finding that can only be explained by the presence of a null allele in addition to the allele with the nonsense mutation. The combination of TG intolerance of uncertain cause, together with CETP deficiency due to a novel mutation, produced the paradoxical constellation--high levels of HDL cholesterol (172 mg/dL) associated with a high post-prandial lipemia of 1460 mg triglycerides/dL.8 hours--and provided further insight into the role of CETP as mediator between pools of triglycerides and cholesteryl esters in plasma.