A novel method for measuring human lipoprotein lipase and hepatic lipase activities in postheparin plasma

The objective of this study was to establish a new lipoprotein lipase (LPL) and hepatic lipase (HL) activity assay method. Seventy normal volunteers were recruited. Lipase activities were assayed by measuring the increase in absorbance at 546 nm due to the quinoneine dye. Reaction mixture-1 (R-1) contained dioleoylglycerol solubilized with lauryldimethylaminobetaine, monoacylglycerol-specific lipase, glycerolkinase, glycerol-3-phosphate oxidase, peroxidase, ascorbic acid oxidase, and apolipoprotein C-II (apoC-II). R-2 contained Tris-HCl (pH 8.7) and 4-aminoantipyrine. Automated assay of lipase activities was performed with an automatic clinical analyzer. In the assay for HL + LPL activity, 160 microl R-1 was incubated at 37 degrees C with 2 microl of sample for 5 min, and 80 microl R-2 was added. HL activities were measured under the same conditions without apoC-II. HL and LPL activities were also measured by the conventional isotope method and for HL mass by ELISA. Lipase activity detected in a 1.6 M NaCl-eluted fraction from a heparin-Sepharose column was enhanced by adding purified apoC-II in a dose-dependent manner, whereas that eluted by 0.8 M NaCl was not. Postheparin plasma-LPL and HL activities measured in the present automated method had high correlations with those measured by conventional activity and mass methods. This automated assay method for LPL and HL activities is simple and reliable and can be applied to an automatic clinical analyzer.

The relationship of serum lipoprotein lipase mass with fasting serum apolipoprotein B-48 and remnant-like particle triglycerides in type 2 diabetic patients

BACKGROUND

There have been no previous reports showing specifically the relation between lipoprotein lipase (LPL) and apolipoprotein (apo) B-48 or remnant metabolism. In this study, we have clarified the relationships of LPL mass in pre-heparin with serum apo B-48 measured by enzyme-linked immunosorbent assay, triglycerides (TG), and remnant-like particle triglycerides (RLP-TG).

MATERIAL AND METHODS

Seventy-nine type 2 diabetic subjects [age, 55+/-13; body mass index (BMI), 25+/-5.0 kg/m2; fasting plasma glucose (FPG), 7.39+/-2.22 mmol/l, HbA1c, 6.5+/-1.3%, total cholesterol (TC), 5.36+/-1.09 mmol/l, TG, 2.32+/-2.53 mmol/l; HDL-C, 1.22+/-0.44 mmol/l; serum LPL mass, 45+/-22 ng/ml; apo B-48, 6.6+/-6.3 microg/ml] were recruited in this study. Fasting serum apo B-48 were measured by ELISA using anti-human apo B-48 monoclonal antibodies (MoAb) and LPL mass by ELISA using anti-bovine milk LPL MoAb. RLP-TG levels were measured using monoclonal antibodies to apo B-100 and apo A-1.

RESULTS

There was no relationship of LPL mass to age, BMI, FPG, and HbA1c. Serum LPL mass was correlated inversely with TG (r=-0.529 p<0.0001) and positively with HDL-C (r=0.576, p<0.0001). Also, LPL mass showed inverse correlations with apo B-48 (r=-0.383 p<0.0001) and RLP-TG (r=-0.422 p<0.0001, n=51). Multiple regression analysis with TG, apo B-48, or RLP-TG as dependent variables, and age, gender, BMI, plasma glucose, and LPL mass as independent variables showed that LPL mass was associated independently with TG, apo B-48, or RLP-TG.

CONCLUSION

The decrease in LPL protein mass could cause an increase in serum apo B-48 and RLP-TG levels, which is related to the retardation of remnant metabolism.

A novel method for measuring human hepatic lipase activity in postheparin plasma

The objective of this study was to establish a hepatic lipase (HL) assay method that can be applied to automatic clinical analyzers. Seventy-four hyperlipidemic subjects (men/women 45/29) were recruited. Lipase activity was assayed measuring the increase in absorbance at 546 nm due to quinonediimine dye production. Reaction mixture R-1 contained 50 mM Tris-HCl (pH 9.5), 0.5 mM glycerol-1,2-dioleate, 0.4% (unless otherwise noted) polyoxyethylene-nonylphenylether, 3 mM ATP, 3 mM MgCl(2), 1.5 mM CaCl(2), monoacylglycerol-specific lipase, glycerol kinase, glycerol-3-phosphate oxidase, 0.075% N,N-bis-(4-sulfobutyl)-3-methylaniline-2 Na, peroxidase, ascorbic acid oxidase. Reaction mixture R-2 contained 50 mM Tris-HCl (pH9.5), 0.15% 4-aminoantypirine. Automated assay for activity was performed with a Model 7080 Hitachi analyzer. In the lipase assay, 160 microl of R-1 was incubated at 37 degrees C with 3 microl of samples for 5 min, and 80 microl of R-2 was added. Within-run coefficient of variations was 0.9-1.0%. Calibration curve of lipase activity was linear (r = 0.999) between 0 and 320 U/l. Analytical recoveries of purified HL added to plasma were 96.6-99.8%. HL activity in postheparin plasma measured in this method had a closer correlation with HL mass by a sandwich ELISA (r = 0.888, P < 0.0001) than those in the conventional method using [(14)C-]triolein (r = 0.730, P < 0.0001). This assay method for HL activity can be applied to an automatic clinical analyzer.

Relationship of lipoprotein lipase and hepatic triacylglycerol lipase activity to serum adiponectin levels in Japanese hyperlipidemic men

OBJECTIVE

The aim of this study was to determine how lipoprotein lipase (LPL) and hepatic triacylglycerol lipase (HTGL) activity relate to serum adiponectin levels.

RESEARCH DESIGN AND METHODS

Fifty-five hyperlipidemic Japanese men were recruited for this study. LPL and HTGL activity in post-heparin plasma (PHP) was measured using Triton X-100 emulsified-[14C] triolein. The remaining activity in the presence of 1M NaCl was defined as HTGL activity. Serum adiponectin levels were determined by an enzyme-linked immunosorbent assay system.

RESULT

LPL activity had a positive relationship with HDL2, but had no relation with HDL3, while HTGL had positive relationship with HDL3, but had no relationship with HDL2. LPL activity showed a positive relationship [r = 0.345, p = 0.010] to serum adiponectin levels, while and HTGL activity showed an inverse relationship [r = - 0.365 p = 0.006]. Multiple regression analysis with LPL and HTGL as dependent variables and age, BMI, serum adiponectin and the homeostasis model assessment of insulin resistance (HOMA-IR) as independent variables showed LPL and HTGL's association to adiponectin did not persist after adjustments for these covariants. However, the association of LPL activity to HOMA-IR was found to persist after adjustments of age, BMI, and serum adiponectin.

CONCLUSIONS

There was a co-linearity between insulin sensitivity and adiponectin as well as insulin sensitivity and LPL/HTGL activity.

Carotid artery intima-media thickness and brachial artery flow-mediated vasodilation in asymptomatic Japanese male subjects amongst apolipoprotein E phenotypes

BACKGROUND

Epidemiological studies suggest that apolipoprotein E (apoE) polymorphism influences plasma lipoprotein levels and the development of cardiovascular disease.

OBJECTIVE

To clarify the role of apoE polymorphism as a risk factor for early atherosclerosis.

DESIGN

Using a high-resolution ultrasound method, we investigated the association between apoE phenotypes, carotid intima-media thickness (CCA-IMT), and flow-mediated dilation in the brachial artery (brachial-FMD) in 96 healthy asymptomatic Japanese men (mean +/- SD age, 50 +/- 8 years).

RESULTS

Serum cholesterol and LDL-cholesterol levels in subjects with E3E4 were highest and those with E2E3 were lowest (P < 0.05 and P < 0.05, respectively). The CCA-IMT in E3E4 subjects (0.76 +/- 0.17 mm) was greater than that in E2E3 and E3E3 (0.61 +/- 0.15 and 0.64 +/- 0.14 mm, respectively; P < 0.01). In contrast, there was no difference between brachial-FMD and apoE phenotypes (P=0.15). By univariate analysis, CCA-IMT was positively correlated with age (r=0.51, P < 0.01), LDL-chol/HDL-chol ratio (r=0.37, P < 0.01), triglycerides (r=0.23, P < 0.05), and negatively correlated with HDL-cholesterol (r=-0.31, P < 0.01). An association between CCA-IMT and the presence of E4 allele was also found (P < 0.05). Logistic regression analysis revealed that the presence of E4 allele was a higher risk for increased IMT (relative risk of 4.4, 95% CI 1.5-12.5), even after adjustment for age, LDL-cholesterol, blood pressure and other known risk factors. A negative correlation between brachial-FMD and CCA-IMT was also found in all subjects (r=-0.21, P < 0.05), being most apparent in the E3E4 subjects (r=-0.53, P < 0.02).

CONCLUSION

ApoE4 phenotype was independently associated with an increased risk of carotid atherosclerosis and elevated LDL-cholesterol levels in asymptomatic middle-aged Japanese men.

Effects of hepatic lipase gene promoter nucleotide variations on serum HDL cholesterol concentration in the general Japanese population

Genetic factors may play a major role in determining serum high-density lipoprotein (HDL) cholesterol (HDL-C) levels in the general population. Cholesteryl ester transfer protein (CETP) is a strong genetic factor as a determinant of HDL-C levels in Japanese, whereas hepatic lipase (HL) plays a predominant role in Caucasian populations. We investigated the effects of HL gene promoter polymorphisms on HDL-C levels in a general population of Japanese men (n = 299). An HL promoter polymorphism of -514C/T explained a considerable variance of HDL-C (2.9%), as compared with CETP mutations of D442G and IVS14 + 1G > A (3.6% and 1.9%). HL promoter variation of the -514C/C genotype, reported to have high HL activity, had significant effects on decreasing HDL-C levels (-3.8mg/dl), but -514T allele carriers had a weak effect on increasing HDL-C levels. The frequency of the -514T allele was three times higher (0.50) in the Japanese than in Caucasian populations (0.15-0.19). Thus, the higher frequency of the HL -514T allele, along with CETP gene mutations, could explain about 9% of phenotypic variability of HDL-C. These genetic attributes may be among the many factors that contribute to the relatively higher serum HDL-C levels in Japanese subjects.

Hyperhomocysteinemia, diabetes mellitus, and carotid atherosclerosis independently increase atherosclerotic vascular disease outcome in Japanese patients with end-stage renal disease

BACKGROUND

Patients with end-stage renal disease (ESRD) have high mortality from atherosclerotic/atherothrombotic vascular disease (AVD). However, the role of an elevated plasma total homocysteine (tHcy) level as a risk factor is uncertain in ESRD.

METHODS

We enrolled 55 ESRD patients in a prospective follow-up study in order to evaluate the prognostic significance of their tHcy levels, common methylenetetrahydrofolate reductase (MTHFR) gene polymorphism, and other atherosclerotic risk factors, in combination with the results of B mode ultrasound for carotid arteries.

RESULTS

Mean intima-media thickness of the common carotid artery (CCA-IMT) in ESRD patients was thicker than that in 102 age- and sex-matched healthy controls. Carotid plaque was more frequently present in patients compared with controls, as was calcified plaque more common in patients (p < 0.001). Plasma tHcy levels (mean +/- SD) in patients (39.1 +/- 27.2 nmol/ml) were higher than that (8.8 +/- 2.7 nmol/ml) in controls (p < 0.001). Folic acid was the major determinant of elevated tHcy levels in ESRD patients. During the follow-up period of 31 +/- 3 months, 14 patients had one or more AVD complications, and 10 consequently died from AVD causes. Proportional hazards modeling showed that 5-year intervals of age (relative risk of 2.95, 95% CI 1.62 - 5.37), 10 nmol/ml intervals of tHcy levels (relative risk of 2.31, 95% CI 1.31 - 4.08), and presence of diabetes mellitus (relative risk of 6.62, 95% CI 1.07 +/- 40.8) were independent predictors of future AVD events, and tHcy levels (relative risk of 2.67, 95% CI 1.29 - 5.52) and age (relative risk of 2.10, 95% CI 1.15 - 3.83) were those of AVD mortality. We also found a significant association between carotid plaque prevalence and AVD events (X(2) = 11.6, p = 0.001).

CONCLUSION

Hyperhomocysteinemia, diabetes mellitus, and carotid atherosclerosis appeared to contribute independently to increase the risk of AVD outcome in Japanese patients with ESRD.

Circulating matrix metalloproteinases and their inhibitors in premature coronary atherosclerosis

To investigate the clinical significance of circulating matrix metalloproteinases (MMPs) and their tissue inhibitos (TIMPs) in patients with premature coronary atheroscrelosis, we studied 53 consecutive male patients with angiographically defined premature (<65 years) and stable coronary artery disease. Plasma levels of MMP-2, MMP-3, MMP-9, TIMP-1, and TIMP-2 were determined in peripheral blood by a sandwich enzyme immunoassay, and the results were compared with those from 133 age-matched control males. There were significant differences in all the MMPs and TIMPs (p<0.001) between patients and controls. In the patient group, the levels of MMP-9 (mean +/- SD (ng/ml) 27.2 +/- 15.2/21.8 +/- 15.2) and TIMP-1 (130.4 +/- 55.7/94.5 +/- 26.3) were significantly higher, and the levels of MMP-2 (632.5 +/- 191.6/727.6 +/- 171.4), MMP-3 (53.1 +/- 31.2/79.6 +/- 29.9), and TIMP-2 (24.7 +/- 15.2/35.4 +/- 16.4) were significantly lower than those of controls. We found significant positive correlation between plasma MMP-9 levels and low-density lipoprotein (LDL)-cholesterol levels (Rs = 0.168, p = 0.022), and significant negative correlation between plasma MMP-9 levels and high-density lipoprotein (HDL)-cholesterol levels (Rs = -0.164, p = 0.026) by Spearman rank correlation test. In contrast, plasma MMP-2 (Rs = 0.181, p = 0.014) and MMP-3 (Rs = 0.260, p = 0.0004) levels were positively correlated with HDL-cholesterol levels. TIMP-2 levels were negatively correlated with total cholesterol (Rs = -0.197, p = 0.007) and LDL-cholesterol (Rs = -0.168, p=0.022) levels. These results suggest that the circulating levels of MMPs and TIMPs are altered in patients with premature coronary atherosclerosis and that plasma lipoprotein cholesterol levels correlate with these, possibly as a result of the lipoprotein-vessel wall interactions.

Effect of common methylenetetrahydrofolate reductase gene mutation on coronary artery disease in familial hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant disorder characterized by primary hypercholesterolemia and premature coronary artery disease (CAD). However, the development of CAD in FH shows considerable interindividual variations. Elevated levels of plasma homocysteine have been recognized as independent risk factors for CAD. A 5,10-methylenetetrahydrofolate reductase (MTHFR) gene mutation (valine [V] was substituted for alanine [A]) has been reported to be associated with elevated levels of plasma homocysteine in mutant homozygotes (i.e., VV). We studied 199 consecutive male heterozygous FH patients, 99 with and 100 without CAD. In the CAD group, genotype VV and V alleles were significantly more frequent than in the non-CAD group (15% vs 7% in genotypes [p = 0.035] and 0.41 vs 0.30 in alleles [p = 0.017]). The mean ages at onset in the CAD group were 50, 51, and 43 years for genotypes AA, AV, and VV, respectively (p <0.05); the age of onset of CAD in genotype VV was significantly lower than in the other 2 genotypes. Kaplan-Meier survivor curves indicated that the development of CAD was significantly accelerated by MTHFR mutation, probably in a gene dose-dependent manner. Furthermore, only MTHFR genotype VV was shown to be an independent predictor of the early onset of CAD in a stepwise multiple regression analysis. The mean plasma homocysteine levels of genotype VV were significantly higher than those of the other 2 genotypes. Thus, the MTHFR mutation appears to accelerate the onset of CAD through elevation of plasma homocysteine levels in male heterozygous patients with FH.

Cholesteryl ester transfer protein and atherosclerosis

Plasma cholesteryl ester transfer protein facilitates the transfer of cholesteryl ester from HDL to apolipoprotein B-containing lipoproteins. Its significance in atherosclerosis has been debated in studies of human population genetics and transgenic mice. The current review will focus on human plasma cholesteryl ester transfer protein research, including TaqIB, 1405V, and D442G polymorphisms. Plasma cholesteryl ester transfer protein has a dual effect on atherosclerosis, depending on the metabolic background. In hypercholesterolaemia or combined hyperlipidaemia, plasma cholesteryl ester transfer protein may be pro-atherogenic and could be a therapeutic target.

Plasma homocysteine level and development of coronary artery disease

BACKGROUND

The plasma level of homocysteine is an independent risk factor for atherosclerotic vascular disease. The relationship between plasma homocysteine level and the onset of coronary artery disease (CAD) has not been established.

OBJECTIVE

To investigate the relationship between plasma homocysteine level and the age at which CAD was diagnosed.

METHODS

Fifty-seven male patients aged < or = 65 years (mean age 53 years) with angiographically proven symptomatic CAD seen consecutively and 138 age-matched male control subjects (mean age 52 years) free from atherosclerotic vascular disease were studied. They were divided into two subgroups, a group of younger subjects (aged < or = 55 years) and a group of older subjects (aged 56-65 years).

RESULTS

Plasma homocysteine levels in CAD patients significantly exceeded those of control subjects (means 13.4 versus 10.6 nmol/ml, P = 0.0002). Plasma homocysteine level of subjects in younger CAD group was significantly higher than that of subjects in older CAD group (15.0 versus 11.3 nmol/ml, P = 0.03), and age and logarithmically transformed plasma homocysteine level exhibited a significant negative correlation (r = -0.28, P = 0.03) for subjects in CAD group. Among control subjects, members of our two age subgroups had similar plasma homocysteine levels. Younger CAD patients had significantly higher plasma homocysteine levels than did younger controls (15.0 versus 10.4 nmol/ml, P < 0.0001). However, for older groups there was no significant difference between plasma homocysteine levels in CAD patients and controls (11.3 versus 10.9 nmol/ml). Multiple regression analysis showed that only logarithmically transformed plasma homocysteine level was a significant predictor for age of onset of CAD.

CONCLUSION

An elevated level of plasma homocysteine is more important in the development of premature CAD than it is in that of late-onset CAD among men.

Abetalipoproteinemia caused by maternal isodisomy of chromosome 4q containing an intron 9 splice acceptor mutation in the microsomal triglyceride transfer protein gene

Uniparental disomy (UPD), a rare inheritance of 2 copies of a single chromosome homolog or a region of a chromosome from one parent, can result in various autosomal recessive diseases. Abetalipoproteinemia (ABL) is a rare autosomal recessive deficiency of apoB-containing lipoproteins caused by a microsomal triglyceride transfer protein (MTP) deficiency. In this study, we describe a patient with ABL inherited as a homozygous intron 9 splice acceptor G(-1)-to-A mutation of the transfer protein gene. This mutation alters the splicing of the mRNA, resulting in a 36 amino acids, in-frame deletion of sequence encoded by exon 10. We analyzed chromosome 4, including MTP gene (4q22-24), using short tandem repeat markers. The proband has only his mother's genes in chromosome 4q spanning a 150-centimorgan region; ie, segmental maternal isodisomy 4q21-35, probably due to mitotic recombination. Nonpaternity between the proband and his father was excluded using 6 polymorphic markers from different chromosomes (paternity probability, 0.999). Maternal isodisomy (maternal UPD 4q) was the basis for homozygosity of the MTP gene mutation in this patient.

Opposite effects on serum cholesteryl ester transfer protein levels between long-term treatments with pravastatin and probucol in patients with primary hypercholesterolemia and xanthoma

Long-term effects of pravastatin and probucol on serum cholesteryl ester transfer protein (CETP) and xanthoma/xanthelasma size were compared. Twenty-three patients with primary hypercholesterolemia and xanthoma/xanthelasma, including 11 patients with heterozygous familial hypercholesterolemia, were treated with pravastatin (20 mg/day) or probucol (1000 mg/day) for 24 months. Serum CETP levels were measured by sandwich ELISA. In 11 patients (six men and five women, 55 +/- 2 [SE] yr) treated with pravastatin, serum cholesterol levels decreased from 262 +/- 13 to 229 +/- 13 mg/dl during the 24-month treatment period (P = 0.05). Serum HDL cholesterol levels were not changed. Serum CETP levels decreased from 2.5 +/- 0.2 to 2.0 +/- 0.2 microg/ml (-21%, P = 0.002). By contrast, in 12 patients (four men and eight women, 57 +/- 4 year) treated with probucol, serum cholesterol levels did not significantly decrease from 236 +/- 11 to 207 +/- 13 mg/dl. Serum HDL cholesterol levels decreased from 44 +/- 2 to 30 +/- 2 mg/dl (P = 0.009). Serum CETP levels increased from 2.3 +/- 0.1 to 2.8 +/- 0.2 microg/ml (+23%, P = 0.02). Xanthelasma regression was found in two of four patients (50%) each treated with pravastatin and probucol, respectively. In contrast, Achilles' tendon xanthoma regressed in four of five patients (80%) treated with pravastatin, but only in two of five patients (40%) treated with probucol. Patients with xanthoma/xanthelasma regression after 2 years treatment had higher baseline levels of serum CETP than those without regression (2.7 +/- 0.2 microg/ml [n = 9] versus 2.1 +/- 0.2 microg/ml [n = 7], P = 0.05). Serial changes in serum CETP levels during treatment with pravastatin and probucol were discordant, but not related to the degree of xanthoma regression. However, higher level of serum HDL3 cholesterol was an independent factor in the smaller size of Achilles' tendon xanthoma at baseline. In addition, higher levels of serum HDL3 triglyceride on lipid-lowering therapy (6 months) appear to be a common predictor of regression of Achilles' tendon xanthoma in the treatment with either pravastatin or probucol.

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.

Low-density lipoprotein receptor genotype-dependent response to cholesterol lowering by combined pravastatin and cholestyramine in familial hypercholesterolemia

We compared the effects of cholesterol-lowering therapy on 2 patient groups genetically defined as heterozygous for familial hypercholesterolemia (FH), 5 with a deletion of exon 15 (FH(Tonami-1)), and 7 with a point mutation at codon 664 (FH(Kanazawa-2)). There were significant differences in both serum and low-density lipoprotein cholesterol reductions between the 2 groups after combination therapy with pravastatin and cholestyramine, and the overall effect of genotype on serial changes in both was significant.

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 microg/ml (mean+/-S.D.) and that of 37 females was 2.0+/-0.5 microg/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.