Evaluation of an HPLC method for LDL-cholesterol determination in patients with various lipoprotein abnormalities in comparison with beta-quantification

A General Review of Methodologies Used in the Determination of Cholesterol (C27H46O) Levels in Foods

Cholesterol (C27H46O) is a lipid-derived substance found in lipoproteins and cell membranes. It is also one of the main sources for the production of bile acids, vitamin D, and steroid hormones. Today, foods are evaluated by consumers not only according to their taste and nutritional content but also according to their effects on consumer health. For example, many consumers choose foods according to their cholesterol level. The cholesterol in the food can directly affect the blood cholesterol level when consumed, which can lead to cardiovascular diseases. High levels of cholesterol can lead to diet-related human diseases such as cardiac arrest, paralysis, type II diabetes, and cerebral hemorrhage. In societies with high living standards, interest in and consumption of foods that lower or have low cholesterol levels have increased recently. Accordingly, efforts to increase the variety of foods with reduced cholesterol levels are on the rise. This has indirectly led to the accurate measurement of cholesterol levels in blood and food being of great importance. Classical chemical, enzymatic, colorimetric, polarographic, chromatographic, and spectrophotometric methods; enzymatic, nonenzymatic, and electrochemical sensors; and biosensors are used for the determination of cholesterol in foods. The purpose of this review is to reveal and explore current and future trends in cholesterol detection methods in foods. This review will summarize the most appropriate and standard methods for measuring cholesterol in biological components and foods.

First-in-human autologous implantation of genetically modified adipocytes expressing LCAT for the treatment of familial LCAT deficiency

Background

Familial lecithin: cholesterol acyltransferase (LCAT) deficiency (FLD) is a severe inherited disease without effective treatment. Patients with FLD develop severe low HDL, corneal opacity, hemolytic anemia, and renal injury.

Objective

We developed genetically modified adipocytes (GMAC) secreting LCAT (LCAT-GMAC) for ex vivo gene therapy. GMACs were prepared from the patient’s adipocytes to express LCAT by retroviral gene transduction to secrete functional enzymes. This study aimed to evaluate the safety and efficacy of LCAT-GMAC implantation in an FLD patient.

Methods

Proliferative preadipocytes were obtained from a patient using a ceiling culture and retrovirally transduced with LCAT. After obtaining enough cells by expansion culture of the transduced cells, the resulting LCAT-GMACs were implanted into a patient with FLD. To evaluate the safety and efficacy, we analyzed the outcome of the autologous implantation for 24 weeks of observation and subsequent 240 weeks of the follow-up periods.

Results

This first-in-human autologous implantation of LCAT-GMACs was shown to be safe by evaluating adverse events. The LCAT-GMAC implantation increased serum LCAT activity by approximately 50% of the baseline and sustained over three years. Consistent with increased LCAT activity, intermediate-density lipoprotein (IDL) and free cholesterol levels of the small and very small HDL fractions decreased. We found the hemoglobin/haptoglobin complex in the hemolyzed pre-implantation sera of the patient. After one week of the implantation, the hemoglobin/haptoglobin complex almost disappeared. Immediately after the implantation, the patient's proteinuria decreased temporarily to mild levels and gradually increased to the baseline. At 48 weeks after implantation, the patient's proteinuria deteriorated with the development of mild hypertension. By the treatment with antihypertensives, the patient's blood pressure normalized. With the normalization of blood pressure, the proteinuria rapidly decreased to mild proteinuria levels.

Conclusions

LCAT-GMAC implantation in a patient with FLD is shown to be safe and appears to be effective, in part, for treating anemia and proteinuria in FLD.

Distinct Differences in Lipoprotein Particle Number Evaluation between GP-HPLC and NMR: Analysis in Dyslipidemic Patients Administered a Selective PPARα Modulator, Pemafibrate

AIM

We established a method to evaluate the lipid concentrations, size and particle numbers (PNs) of lipoprotein subclasses by gel permeation chromatography (GP-HPLC). Nuclear magnetic resonance (NMR) is widely used to analyze these parameters of lipoprotein subclasses, but differences of the two methods are unknown. Current study compared the PNs of each lipoprotein subclass measured by GP-HPLC and NMR, and assessed the effect of a selective PPARα modulator, pemafibrate.

METHODS

Lipoprotein profiles of 212 patients with dyslipidemia who participated in the phase 2 clinical trial of a selective PPARα modulator, pemafibrate, were analyzed by two methods, GP-HPLC and NMR, which were performed with LipoSEARCH (Skylight Biotech) and LipoProfile 3 (LabCorp), respectively. GP-HPLC evaluated the PNs of 18 subclasses, consisting of CM, VLDL1-5, LDL1-6, and HDL1-6. NMR evaluated the PNs of 9 subclasses, consisting of large VLDL & CM, medium VLDL, small VLDL, IDL, large LDL, small LDL, large HDL, medium HDL and small HDL.

RESULTS

Three major classes, total CM&VLDL, total LDL and total HDL were obtained by grouping of corresponding subclasses in both methods and PNs of these classes analyzed by GP-HPLC were correlated positively with those by NMR. The correlation coefficients in total CM&VLDL, total LDL and total HDL between GP-HPLC and NMR was 0.658, 0.863 and 0.798 (all p＜0.0001), respectively. The PNs of total CM&VLDL, total LDL and total HDL analyzed by GP-HPLC was 249.5±51.7nM, 1,679±359 nM and 13,273±1,564 nM, respectively, while those by NMR was 124.6±41.8 nM, 1,514±386 nM and 31,161±4,839 nM, respectively. A marked difference in the PNs between the two methods was demonstrated especially in total HDL. The number of apolipoprotein (Apo) B molecule per one ApoB-containing lipoprotein particle, total CM&VLDL plus total LDL, was 1.10±0.05 by GP-HPLC, while 1.32±0.18 by NMR. The number of ApoA-I per one HDL particle was 3.40±0.17 by GP-HPLC, but only 1.46±0.15 by NMR, much less than reported previously.From the phase 2 clinical trial, randomizing 212 patients to pemafibrate 0.025-0.2 mg BID, fenofibrate 100 mg QD, or placebo groups, pemafibrate reduced the PNs of CM, large VLDL1-VLDL3 and medium VLDL4, but not small VLDL5 by GP-HPLC. It significantly decreased the PNs of smaller LDL and larger HDL particles, but increased those of larger LDL and smaller HDL particles. In contrast, NMR showed marked variations in the effect of pemafibrate on lipoprotein PNs, and no significant size-dependent changes.

CONCLUSIONS

GP-HPLC evaluates the lipoprotein PNs more accurately than NMR and can be used for assessing the effects of lipid-lowering drugs on lipoprotein subclasses.

Serum cholesterol and triglyceride reference ranges of twenty lipoprotein subclasses for healthy Japanese men and women

AIM

This epidemiological study was done to generate normal ranges for the cholesterol and triglyceride levels in serum lipoprotein subclasses isolated from healthy adults based on gender and menopausal status.

METHODS

Cholesterol and triglyceride levels in 20 lipoprotein subclasses as separated by high performance liquid chromatography were measured in serum obtained from 825 fasting healthy subjects (267 men, 558 women).

RESULTS

For serum cholesterol, 13.7% was found in very low density lipoprotein (VLDL) subclasses, 55.6% in low density lipoprotein (LDL) subclasses, and 30.4% in high density lipoprotein (HDL) subclasses. For serum triglycerides, these values were 52.1%, 27.9%, and 17.4%, respectively. Levels of cholesterol in some VLDL subclasses were inversely correlated with the levels of some HDL subclasses, while for triglycerides, elevated levels in any one subclass were generally strongly associated with elevated levels in all other subclasses. Men had significantly higher large VLDL-cholesterol levels than women (P < 0.05), while women had significantly higher small VLDL-cholesterol levels than men (P < 0.001). Women had significantly higher large LDL- and large and medium HDL-cholesterol levels than men (P < 0.001). Men had significantly higher chylomicron (CM), large and medium VLDL-, and small LDL-triglyceride levels than women (P < 0.001). Women had significantly higher very large and large HDL-triglyceride levels than men (P < 0.01). Postmenopausal women had significantly higher CM, all VLDL, and large, medium and small LDL-cholesterol levels, and significantly higher all VLDL, LDL, and HDL-triglyceride levels than premenopausal women (P < 0.001).

CONCLUSIONS

Our data document important gender and menopausal status differences in cholesterol and triglyceride subclass levels, as well as significant correlations between values in the various serum lipoprotein subclasses.

Ten-year evaluation of homogeneous low-density lipoprotein cholesterol methods developed by Japanese manufacturers. Application of the Centers for Disease Control and Prevention/Cholesterol Reference Method Laboratory Network lipid standardization protocol

AIM

The risk index for atherosclerotic cardiovascular diseases in the Japanese metabolic syndrome-focused health checkup program was changed from total cholesterol (TC) to low-density lipoprotein cholesterol (LDL-C). We discuss the validity of this change with respect to standardization.

METHODS

The beta-quantification procedure of the Centers for Disease Control and Prevention (CDC) uses the LDL-C reference value as a target. Clinical laboratories and commercial manufacturers use homogeneous LDL-C methods for standardization. (A) For clinical laboratories, LDL-C in 648 samples requested from 108 hospitals was analyzed. (B) Manufacturers participated in the CDC/Cholesterol Reference Method Laboratory Network LDL-C standardization protocol. The standardization was conducted with a performance follow-up for the 10-year period from 1998 to 2008 at 2-year intervals, 6 times.

RESULTS

(A) In clinical laboratories, acceptable LDL-C levels within ±4% of the CDC's criteria remained 70.4%, 456 of 648 subjects. Negative maximum bias deviating from the LDL-C target value was -35.8%, -52.5 mg/dL, and positive maximum bias was +24.5%, +32.3 mg/dL. (B) For manufacturers, the standardization achievement rate of the analytical reagent/instrument/calibrator system in the last four standardizations from 2002 to 2008 remained on average 66.6%, far lower than the level required.

CONCLUSIONS

The standardization achievement rate of homogeneous LDL-C methods was much low-er than that of TC. TC should still be used as a risk index for atherosclerotic cardiovascular diseases. The standardization achievement rate of homogeneous LDL-C should be maintained at 100%, at least using samples with normal lipoprotein profiles. The accuracy and specificity of LDL-C should be further improved before practical and clinical use.

Enhancement on the Europium emission band of Europium chlortetracycline complex in the presence of LDL

Low-density lipoprotein (LDL) particles are the major cholesterol-carrying lipoprotein in the human circulation from the liver to peripheral tissues. High levels of LDL-Cholesterol (LDL-C) are known risk factor for the development of coronary artery disease (CAD). The most common approach to determine the LDL-C in the clinical laboratory involves the Friedewald formula. However, in certain situations, this approach is inadequate. In this paper we report on the enhancement on the Europium emission band of Europium chlortetracycline complex (CTEu) in the presence of LDL. The emission intensity at 615 nm of the CTEu increases with increasing amounts of LDL. This phenomenon allowed us to propose a method to determine the LDL concentration in a sample composed by an aqueous solution of LDL. With this result we obtained LDL calibration curve, LOD (limit of detection) of 0.49 mg/mL and SD (standard deviation) of 0.003. We observed that CTEu complex provides a wider dynamic concentration-range for LDL determination than that from Eu-tetracycline previously. The averaged emission lifetimes of the CTEu and CTEu with LDL (1.5 mg/mL) complexes were measured as 15 and 46 micros, respectively. Study with some metallic interferents is presented.

Measurement performance of reagent manufacturers by Centers for Disease Control and Prevention/Cholesterol Reference Method Laboratory Network lipid standardization specified for metabolic syndrome-focused health checkups program in Japan

AIM

This study was designed to clarify the current measurement performance of 7 reagent manufacturers for high-density lipoprotein cholesterol (HDLC), low-density lipoprotein cholesterol (LDLC) and triglycerides (TG) specified for the metabolic syndrome (MetS)-focused health checkups program in Japan.

METHODS

Twenty HDLC, 21 LDLC and 9 TG analytical reagent/instrument/calibrator systems (system), and combinations of reagent lots, instrument models and calibrator lots, underwent Centers for Disease Control and Prevention (CDC)/Cholesterol Reference Method Laboratory Network (CRMLN) lipid standardization. Eighty and 100% systems were requested to achieve an accuracy of within +/-1% and +/-2% of the reference value, so that a clinical laboratory can meet the CDC criteria.

RESULTS

The CDC performance criteria of HDLC, LDLC and TG require an accuracy of within +/-5%, +/-4% and +/-5%, respectively. For HDLC, all 20 systems met the criteria. Fourteen (70.0%) and 18 (90.0%) systems were within +/-1% and +/-2%, respectively. For LDLC, 14 (66.7%) of 21 systems met the criteria, but 7 (33.3%) failed. Five (23.8%) and 17 (81.0%) systems were within +/-1% and +/-2%, respectively. For TG, 8 of 9 systems met the criteria. Two (22.2%) and 4 (44.4%) systems were within +/-1% and +/-2%, respectively. The minimum and maximum differences of a specified sample among manufacturers were 1.6 and 11.0 mg/dL for HDLC, 7.8 and 33.0 mg/dL for LDLC, and 2.8 and 27.4 mg/dL for TG, respectively.

CONCLUSION

Homogeneous HDLC methods are acceptable for MetS, but further accuracy improvement of homogeneous LDLC and TG methods will be needed because of their poor performance.

Evaluation of a gel-permeation high-performance liquid chromatography for determining triglyceride levels in serum major lipoproteins, compared with the ultracentrifugation/precipitation method

OBJECTIVES

To evaluate the gel permeation high-performance liquid chromatography (GP-HPLC) method for determination of triglyceride (TG) levels in low-density lipoprotein (LDL) and high-density lipoprotein (HDL).

DESIGN AND METHODS

The GP-HPLC and the ultracentrifugation (UC)/precipitation methods were used and compared.

RESULTS

There was no significant difference in measured levels of LDL-triglyceride between the two methods, but the HDL-triglyceride levels measured by the GP-HPLC technique were significantly higher than the UC/precipitation one (145+/-47 mg/L and 121+/-45 mg/L respectively, n=38, p<0.0001).

CONCLUSIONS

A GP-HPLC technique provides LDL-TG levels comparable to those obtained by the UC/precipitation method.

Higher frequency of abnormal serum angiopoietin-like protein 3 than abnormal cholesteryl ester transfer protein in Japanese hyperalphalipoproteinemic subjects

BACKGROUND

Either a decrease of cholesteryl ester transfer protein (CETP) or an increase of angiopoietin-like protein 3 (ANGPTL3) in plasma has been shown to increase HDL-cholesterol (HDL-C) levels. However, as yet, it is not known which protein is more strongly associated with the modulation of HDL in the Japanese hyperalphalipoproteinemic (HALT) subjects.

METHODS

The serum concentration of ANGPTL3 and CETP, together with total cholesterol (TC), triglycerides (TG), adiponectin and ApoE phenotypes were determined in three groups with different HDL-C concentrations: low, <40 mg/dl (n=51); normal, 40-90 mg/dl (n=126) and high, >90 mg/dl (n=89) in the average Japanese population.

RESULTS

The normal range (mean+/-2SD) of serum ANGPTL3 (218+/-144 ng/ml) and CETP (1.29+/-0.90 microg/ml) were determined in cases with 40-90 mg/dl HDL-C concentration. The frequency of abnormally high ANGPTL3 cases (>362 ng/ml) were found to be significantly greater (44%) compared with those of low CETP cases (<0.39 microg/ml, 4.5%) in HALT cases (>90 mg/dl). ANGPTL3 showed a high correlation with HDL-C (r=0.67, P<0.0001) and adiponectin (r=0.57, P<0.0001), but not with CETP.

CONCLUSION

In average Japanese population, abnormally higher frequency of increased ANGPTL3 prevail in HALT cases as compared with cases with low CETP. These findings suggest that ANGPTL3, the inhibitor of endothelial lipase, may be more strongly associated with increased HDL-C rather than CETP in plasma. Accordingly, ANGPTL3 seems to be a better target for the modulation of HDL-C.