Development of blood collection tubes for glucose measurement using adenosine 3-phosphate and sodium fluoride as glycolytic inhibitors

BACKGROUND

Blood collection tubes with sodium fluoride (NaF) added as a glycolytic inhibitor are widely used for glucose measurement. However, the glycolytic inhibitory effects of NaF are insufficient, and decreases in glucose levels over time after blood collection have become a problem.

METHODS

Blood from a volunteer collected using an NaF tube was used to compare the glycolysis inhibitory abilities of ATP and ADP. Blood samples from 10 volunteers were collected in NaF tubes and NaF tubes with added ATP (NaF-ATP tubes). The stability of glucose and haemoglobin (Hb)A1c after whole-blood storage from immediately after blood collection to 24 h later was compared.

RESULTS

ATP and ADP had similar inhibitory effects on glycolysis, but ATP was selected as an additive for blood collection tubes because ADP was more haemolytic than ATP. We verified the ability of NaF blood collection tubes supplemented with ATP to inhibit glycolysis. Mean (± standard deviation) glucose levels (n=10) after storage for 24 h after blood collection decreased to -9.0 ± 2.7 mg/dL (-0.50 ± 0.15 mmol/L) in conventional NaF tubes. NaF-ATP(20) tubes with 20 mg (0.036 mmol) ATP added showed a reduced decrease, with a mean of -5.8 ± 2.9 mg/dL (-0.32 ± 0.16 mmol/L). NaF-ATP tubes also had no effect on HbA1c measurement.

CONCLUSION

This study reports on a blood collection tube that enables the measurement of glucose and HbA1c. Based on the results of validation, we conclude that NaF-ATP tubes can reduce decreases in glucose over time in stored whole blood compared to conventional NaF tubes.

Measurement of cholesterol levels of lipoprotein subclasses in human serum using anion-exchange high-performance liquid chromatography with a linear concentration gradient of sodium perchlorate

BACKGROUND

Relationships between the subclasses of high-density lipoprotein (HDL) or low-density lipoprotein (LDL) and the risk of atherosclerotic cardiovascular disease have been studied, and using various methods, such as ultracentrifugation, electrophoresis, and nuclear magnetic resonance, for analysing lipoprotein subclasses. We established a method for HDL and LDL subclasses using anion-exchange high-performance liquid chromatography (AEX-HPLC) with a linear concentration gradient of sodium perchlorate (NaClO4).

METHOD

In the AEX-HPLC, the subclasses of HDL and LDL were separated, and detected using a post-column reactor with an enzymatic cholesterol reagent, that contained cholesterol esterase, cholesterol oxidase, and peroxidase as major ingredients. LDL subclasses were divided based on the absolute value of first-derivative chromatogram.

RESULT

Three HDL subclasses, HDL-P1, HDL-P2, and HDL-P3, and three LDL subclasses, LDL-P1, LDL-P2, and LDL-P3, were separated by AEX-HPLC, and detected in order. The major components of HDL-P2 and HDL-P3 were HDL3 and HDL2, respectively. The linearity was determined for each lipoprotein subclass. The coefficients of variation of cholesterol concentration of the subclasses for within-day assay (n = 10) and between-day assay (n = 10) ranged between 3.08-8.94% and 4.52-9.97%, respectively. Cholesterol levels in HDL-P1 of diabetic patients were positively correlated with oxidized LDL levels (r = 0.409, p = 0.002). Moreover, cholesterol levels in LDL-P2 and LDL-P3 were positively correlated with oxidized LDL levels (r = 0.393, p = 0.004 and r = 0.561, p < 0.001, respectively).

CONCLUSION

AEX-HPLC may be highly suitable as an assay to clinically assess lipoprotein subclasses.

Evaluation of the two-point calibration bromocresol green method, showing reduced deviation from the bromocresol purple method in sera from patients with hypoalbuminemia

BACKGROUND

The bromocresol green (BCG) and bromocresol purple (BCP) methods are widely used for albumin measurements in routine testing, but the BCG method is known to react with globulin fractions and to have low specificity for albumin. We evaluated a calibration method using different concentrations of human serum albumin standards (two-point calibration BCG method) with the aim of reducing the effect of globulin fractions on the BCG method in patients with hypoalbuminemia.

METHOD

In the two-point calibration BCG method, two concentrations of standard solutions and their calibration values are set based on the difference in albumin concentrations measured by the BCG method (BCG-HSA method) and the modified BCP (modified BCP-HSA method) calibrated with human serum albumin standard solution (HSA). Albumin concentrations were measured in 136 patient serum samples (healthy group: 52, hypoalbuminemic group: 84) by the two-point calibrated BCG method and compared with those obtained using the modified BCP-HSA method.

RESULTS

The mean albumin concentrations obtained using the two-point calibrated BCG and modified BCP-HSA methods were 39.18 ± 3.42 g/L and 39.37 ± 3.14 g/L (healthy group) and 26.20 ± 6.23 g/L and 26.23 ± 5.67 g/L (hypoalbuminemia group), respectively. The results of the two-point calibration BCG method were in a close agreement over the entire concentration range tested compared to the modified BCP-HSA method.

CONCLUSIONS

Based on these results, this calibration method reduces the influence of the globulin fraction on the BCG method. In the hypoalbuminemic group, the calibration method was shown to provide results consistent with the BCP method, which is highly specific for albumin.

Postprandial Fatty Acid Metabolism with Coconut Oil in Young Females: A Randomized, Single-blind, Cross-over Trial

BACKGROUND

Approximately 84% of fatty acids contained in coconut oil (CO) are saturated fatty acids (SFA), and approximately 47% of the SFA are lauric acid with 12 carbon atoms. Lauric acid carbon chain length is intermediate between medium and long chain fatty acids. We examined how CO acts on lipid-related substances in the blood to determine whether its properties were similar to medium-chain fatty acids (MCFA) or long-chain fatty acids (LCFA).

METHODS

This is a randomized controlled single-blind crossover study. 15 females were enrolled, using three test meals containing 30-g each of three different oils: CO (CO-meal), medium-chain triacylglycerol-oil (MCT-meal), and long-chain triacylglycerol-oil (LCT-meal). Blood samples were collected at fasted baseline and every 2 h for 8 h after the intake of each test meal.

RESULTS

Repeated measure analysis of variance (ANOVA) of the ketone bodies and triglyceride (TG) showed an interaction between time and the test meal (P < 0.01 and P < 0.001, respectively). In subsequent Tukey's honestly significant difference (HSD) test of the ketone bodies, statistically significant differences were observed between the CO-meal and the LCT-meal (P < 0.05) 83.8 (95% CI, 14.7,153.0) and between the MCT-meal and the LCT-meal (P < 0.05) 79.2 (95% CI, 10.0,148.4). The incremental area under the curve (iAUC) and maximum increase in very low-density lipoprotein cholesterol (VLDL-C) and intermediate-density lipoprotein cholesterol (IDL-C) were the lowest for CO-meal intakes.

CONCLUSIONS

The characteristics of lauric acid contained in coconut oil, including the kinetics of β-oxidation and effects on blood TG, were very similar to those of MCFA. Moreover, regarding the iAUC and peak increment, VLDL-C and IDL-C were the lowest with the CO-meal. These results suggest that the intake of CO after fasting does not increase the TG, VLDL-C, and IDL-C, and may help prevent dyslipidemia. This trial was registered at UMIN as UMIN000019959.

Clinical Significance of Intermediate-Density Lipoprotein Cholesterol Determination as a Predictor for Coronary Heart Disease Risk in Middle-Aged Men

Background: Not only low-density lipoprotein (LDL) cholesterol but also non-high-density lipoprotein cholesterol (non-HDL-C), very low-density lipoprotein (VLDL) cholesterol (VLDL-C), and intermediate-density lipoprotein (IDL) cholesterol (IDL-C) are reported to be significant risk markers for coronary heart disease (CHD). We reported the relevance of IDL-C to Framingham risk score (F-score), but the present study addressed the relevance of IDL-C to Suita score (S-score), a risk score for coronary heart disease (CHD) developed for the Japanese individuals in addition to F-score.

Methods: The cholesterol levels of lipoproteins, including triglyceride (TG)-rich lipoproteins (IDL and VLDL), were measured by an anion exchange high-performance liquid chromatography (AEX-HPLC). This study enrolled 476 men, aged mean 51 years and free of CHD and stroke.

Results: Non-HDL-C, IDL-C, and VLDL-C significantly correlated with F-score and S-score. In the multiple stepwise regression analysis, IDL-C as well as body mass index (BMI) significantly correlated with both F-score and S-score in both the total subjects and the subjects without drug therapy. The multivariate logistic analysis with the model composed of BMI and IDL-C as the predictor variables demonstrated that 1 SD increase in IDL-C was an independent predictor for 10-year CHD risk >10% of F-score (OR 1.534, 95% CI 1.266–1.859, p < 0001) and that of S-score (OR 1.372, 95% CI 1.130–1.667, p = 0.0014) in the total subjects. Even in the subjects without the drug therapy, the increased IDL-C, as well as BMI, were significant predictors for 10-year CHD risk >10% of S-score as well as F-score.

Conclusion: These results suggest the significant relevance of the increased IDL-C for CHD risk scores in middle-aged men free of CHD and stroke. Further investigations are needed in women and elderly subjects.

Verification of Low-Density Lipoprotein Cholesterol Levels Measured by Anion-Exchange High-Performance Liquid Chromatography in Comparison with Beta Quantification Reference Measurement Procedure

BACKGROUND

A new lipoprotein testing method based on anion-exchange HPLC (AEX-HPLC) was recently established. We verified the accuracy of LDL-C levels, a primary therapeutic target for the prevention of cardiovascular disease (CVD), measured by AEX-HPLC comparing with LDL-C levels measured by beta quantification-reference measurement procedure (BQ-RMP), homogenous assays, and calculation methods.

METHODS

We compared LDL-C levels measured by AEX-HPLC (adLDL-Ch: LDL-Ch and IDL-Ch) and BQ-RMP using blood samples from 52 volunteers. AdLDL-Ch levels were also compared with those measurements by homogeneous assays and calculation methods (Friedewald equation, Martin equation, and Sampson equation) using blood samples from 411 participants with dyslipidemia and/or type 2 diabetes.

RESULTS

The precision and accuracy of adLDL-Ch were verified by BQ-RMP. The mean percentage bias [bias (%)] for LDL-C was 1.2%, and the correlation was y = 0.990x + 3.361 (r = 0.990). These results met the acceptable range of accuracy prescribed by the National Cholesterol Education Program. Additionally, adLDL-Ch levels were correlated with LDL-C levels measured by the 2 homogeneous assays (r > 0.967) and the calculation methods (r > 0.939), in serum samples from patients with hypertriglyceridemia.

CONCLUSIONS

AEX-HPLC is a reliable method for measuring LDL-C levels for CVD risk in daily clinical laboratory analyses.

Innovatively Established Analysis Method for Lipoprotein Profiles Based on High-Performance Anion-Exchange Liquid Chromatography

Separation analysis of lipoprotein classes have various methods, including ultracentrifugation, electrophoresis, and gel permeation chromatography (GPC). All major lipoprotein classes can be separated via ultracentrifugation, but performing the analysis takes a long time. Low-density lipoprotein (LDL), intermediate-density lipoprotein (IDL), and very low-density lipoprotein (VLDL) in patient samples cannot be sufficiently separated via electrophoresis or GPC. Thus, we established a new method [anion-exchange high-performance liquid chromatography (AEX-HPLC)] by using HPLC with an AEX column containing nonporous gel and an eluent containing chaotropic ions. AEX-HPLC can separate five lipoprotein fractions of high-density lipoprotein (HDL), LDL, IDL, VLDL, and others in human serum, which can be used in substitution for ultracentrifugation method. The method was also approved for clinical use in the public health-care insurance in Japan in 2014. Furthermore, we developed an additional method to measure cholesterol levels of the four leading lipoprotein fractions and two subsequent fractions (i.e., chylomicron and lipoprotein(a)). We evaluated the clinical usefulness of AEX-HPLC in patients with coronary heart disease (CHD), diabetes, and kidney disease and in healthy volunteers. Results indicate that the cholesterol levels in IDL and VLDL measured by AEX-HPLC may be useful risk markers of CHD or diabetes. Furthermore, we developed another new method for the determination of alpha-tocopherol (AT) in lipoprotein classes, and this method is composed of AEX-HPLC for the separation of lipoprotein classes and reverse-phase chromatography to separate AT in each lipoprotein class. The AT levels in LDL were significantly correlated with the lag time to copper ion-induced LDL oxidation, which is an index of oxidation resistance. The application of AEX-HPLC to measure various substances in lipoproteins will be clinically expected in the future.

Diabetic dyslipidemia: evaluation and mechanism

Diabetes is one of the well-established independent risk factors for cardiovascular diseases. Diabetes induces dyslipidemia which is characterized by elevated fasting triglyceride (TG) and reduced high-density lipoprotein-cholesterol (HDL-C), and such diabetic dyslipidemia is a crucial determinant for atherogenesis and atherosclerotic progression in patients with diabetes. Previous measurement methods of lipoproteins have problems including time-consuming (ultracentrifugation) and inaccurate and impossible measurements of TG-rich lipoproteins such as chylomicron, intermediate-density lipoprotein (IDL) and very low-density lipoprotein (VLDL). Our developed anion-exchange high-performance liquid chromatography (AEX-HPLC) can measure all fractions of lipoproteins accurately. Our studies using AEX-HPLC showed that IDL and VLDL in type 2 diabetes were higher than non-diabetic subjects, and IDL and VLDL were higher in the order of type 2 diabetic patients with obesity, type 2 diabetic patients without obesity, and non-diabetic subjects. Here, we also describe the underlying mechanisms for development of diabetic dyslipidemia.

Cholesterol Levels of Six Fractionated Serum Lipoproteins and its Relevance to Coronary Heart Disease Risk Scores

Aim: Evaluation of serum lipoprotein profiles including triglyceride (TG)-rich lipoprotein, that is, intermediate-density lipoprotein (IDL), very low-density lipoprotein (VLDL), and chylomicron (CM) remnant is important to manage coronary heart disease (CHD) risk. The purpose of this study was to investigate CHD or cardiovascular disease (CVD) risk scores with cholesterol levels of six fractionated lipoprotein classes {high-density lipoprotein [HDL], low-density lipoprotein [LDL], IDL, VLDL, CM including CM remnant, and lipoprotein (a) [Lp (a)]} in Japanese healthy men.

Methods: The present study enrolled 161 healthy men without any medications. Lipoprotein profiles (fractionated lipoprotein cholesterol levels) were measured by anion-exchange high-performance liquid chromatography (AEX-HPLC) method and were compared with age, estimated glomerular filtration rate (eGFR), and three risk scores, that is, NIPPON DATA, Hisayama risk predicting model, and Suita score.

Results: Levels of LDL-cholesterol (C), VLDL-C, and CM-C significantly differed with age, while values of HDL-C, IDL-C, and Lp(a)-C were not different. The eGFR inversely correlated with LDL-C, IDL-C, VLDL-C, and CM-C. In a stepwise multiple logistic regression analysis, VLDL-C only correlated independently with eGFR. Three risk scores significantly correlated with CM-C.

Conclusions: These results suggested that VLDL-C concentration contributes to an increased risk at early stages of renal dysfunction, and CM-C may serve as a marker for estimating CHD risk in Japanese healthy men.

Effect of dietary modification by calorie restriction on cholesterol levels in lipoprotein(a) and other lipoprotein classes

Background Dietary habits are associated with obesity which is a risk factor for coronary heart disease. The objective is to estimate the change of lipoprotein(a) and other lipoprotein classes by calorie restriction with obesity index and Framingham risk score. Methods Sixty females (56 ± 9 years) were recruited. Their caloric intakes were reduced during the six-month period, and the calorie from fat was not more than 30%. Lipoprotein profiles were estimated at baseline and after the six-month period of calorie restriction. Cholesterol levels in six lipoprotein classes (HDL, LDL, IDL, VLDL, chylomicron and lipoprotein(a)) were analysed by anion-exchange liquid chromatography. The other tests were analysed by general methods. Additionally, Framingham risk score for predicting 10-year coronary heart disease risk was calculated. Results Body mass index, waist circumference, insulin resistance, Framingham risk score, total cholesterol, LDL-cholesterol and IDL-cholesterol were significantly decreased by the calorie restriction, and the protein and cholesterol levels of lipoprotein(a) were significantly increased. The change of body mass index was significantly correlated with those of TC, VLDL-cholesterol and chylomicron-cholesterol, and that of waist circumference was significantly correlated with that of chylomicron-cholesterol. The change of Framingham risk score was significantly correlated with the change of IDL-C. Conclusion Obesity indexes and Framingham risk score were reduced by the dietary modification. Lipoprotein profile was improved with the reduction of obesity indexes, but lipoprotein(a) was increased. The changes of obesity indexes and Framingham risk score were related with those of triglyceride-rich lipoproteins, e.g. IDL, VLDL and CM.

[Fundamental Evaluation and Clinical Usefulness of Lipoprotein Analysis System with Anion-Exchange Chromatography]

We established a method for measurement of the cholesterol concentrations of high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), intermediate density lipoprotein cholesterol (IDL-C) and very low density lipoprotein cholesterol (VLDL-C) by using high performance liquid chromatography (HPLC) with anion-exchange column. The HPLC method has been covered by insurance in 2013, and HLC-729LPII (LPII) system constructed by this method has come on the market in 2014. We evaluated the fundamental precision data of lipoprotein cholesterol values measured by HLC-729 LPII. The within-day and between-day assay coefficients of variation of lipoprotein cholesterol values were 1.4-10.7 (%CV). The lipoprotein profiles of patients with type 2 diabetes mellitus (T2DM, n = 60) without dialysis therapy were measured by LPII. HDL-C obtained by LPII was highly correlated with that obtained by direct assay. LDL-C obtained by LPII was highly correlated with those obtained by direct assay and calculated by Friedewald's formula. In addition, IDL-C obtained by LPII was negatively correlated with estimated Glomerular Filtration Ratio (eGFR). These results suggest that the new HPLC method can be applied to estimate lipoprotein profile of T2DM patients. Particularly, IDL cholesterol may be useful for the evaluation of impaired lipid metabolism in T2DM patients without dialysis therapy, but it remains to be cleared.

Blood levels of serotonin are specifically correlated with plasma lysophosphatidylserine among the glycero-lysophospholipids

Backgrounds

Glycero-lysophospholipids (glycero-LPLs), which are known to exert potent biological activities, have been demonstrated to be secreted from activated platelets in vitro; however, their association with platelet activation in vivo has not been yet elucidated. In this study, we investigated the correlations between the blood levels of each glycero-LPL and serotonin, a biomarker of platelet activation, in human subjects to elucidate the involvement of platelet activation in glycero-LPLs in vivo.

Methods and Results

We measured the plasma serotonin levels in 141 consecutive patients undergoing coronary angiography (acute coronary syndrome, n = 38; stable angina pectoris, n = 71; angiographically normal coronary arteries, n = 32) and investigated the correlations between the plasma levels of serotonin and glycero-LPLs. The results revealed the existence of a specific and significant association between the plasma serotonin and plasma lysophosphatidylserine (LysoPS) levels. On the contrary, regular aspirin intake failed to affect the plasma LysoPS levels despite the fact that the plasma lysophosphatidic acid, lysophosphatidylethanolamine, lysophosphatidylglycerol, and lysophosphatidylinositol levels were lower in those who had taken aspirin regularly.

Conclusion

We found a specific positive correlation between the blood levels of serotonin and LysoPS, a new lipid mediator. Thus, LysoPS might be specifically involved in strong platelet activation, which is associated with the release of serotonin.

General Significance

Our present results suggest the possible involvement of LysoPS in the pathogenesis of atherosclerotic diseases.

•

A significant positive correlation between the plasma serotonin and lysophosphatidylserine was observed.

•

Regular intake of aspirin had no influence on plasma lysophosphatidylserine.

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PS-PLA1 was correlated with lysophosphatidylserine only in acute coronary syndrome.

A rapid anion-exchange chromatography for measurement of cholesterol concentrations in five lipoprotein classes and estimation of lipoprotein profiles in male volunteers without overt diseases

BACKGROUND

Analysis of lipoprotein profile gives important clinical information for lipid-lowering therapy which prevents atherosclerotic diseases. The lipoprotein classes can be isolated from serum with ultracentrifugation, which inevitably consumes a long time and needs large serum volume. We have established a method with anion-exchange chromatography with 1.0 µL of the injected volume in 5.2 min for assay of one sample.

METHODS

One-hundred-forty-one male volunteers without overt diseases were divided three groups (Group 1, non-dyslipidemia with LDL-cholesterol [LDL-C] <120 mg/dL and HDL-cholesterol (HDL-C) ≥40 mg/dL; Group 2, borderline dyslipidemia with 120 ≤ LDL-C < 140 mg/dL and HDL-C ≥40 mg/dL; Group 3, dyslipidemia with LDL-C ≥ 140 mg/dL or HDL-C < 40 mg/dL). Their lipoprotein profiles were evaluated by rapid anion-exchange chromatography, which measured concentrations of HDL-C, LDL-C, IDL-cholesterol, VLDL-cholesterol, and other fraction (chylomicron + lipoprotein [a])-cholesterol (other-C).

RESULTS

The within-day and between-day assay coefficients of variation of lipoprotein cholesterol values were 0.33-4.31% and 2.37-9.19%, respectively. The correlation coefficients between values of HDL-C, LDL-C, IDL-C and VLDL-C by the anion-exchange chromatography and those by ultracentrifugal method were 0.97, 0.92, 0.58 and 0.94, respectively. Group 3 had significantly lower HDL-C and higher concentrations of IDL-C, VLDL-C and other-C than did Group 1. Group 2, borderline dyslipidemia, had significantly higher concentrations of IDL-C and VLDL-C than did Group 1.

CONCLUSION

The rapid anion-exchange chromatography assay may be sufficiently applied to the assessment of borderline dyslipidemia.

[Differences in Measured Values among Homogenous Assay Reagents of LDL-C in LP-X Positive Serum Samples]

The LDL-C level measures with homogeneous (direct) assays in almost of clinical laboratories. Several reports however showed differences in measured values among the assay reagents. We investigated the differences in LDL-C values among direct assays and Friedewald formula (F-f) in 58 LP-X positive serum samples from jaundice patients by comparing LDL-C values measured by anion-exchange chromatography (AEX-HPLC), largely comparable to ultracentrifugation method. Changes in LDL-C values during the treatment of 8 patients were also investigated. Direct assay reagents from Sekisui Medical (S-r), Denka-Seiken (D-r), Wako Chemical (W-r), and Kyowa Medics (K-r) were used for comparison. F-f, S-r, and D-r correlated with AEX-HPLC with r values < 0.6 while W-r and K-r correlated with AEX-HPLC with r-vales > 0.6. Two samples in which F-f values provided 500 mg/dL plus bias to AEX-HPLC (LDL-C value of 220 mg/dL) demonstrated increased levels of IDL-C before treatment. LDL-C values (S-r and D-r) of the 2 samples were relatively high and near to F-f data while LDL-C values (W-r and K-r) were relatively low and close to AEX-HPLC data. The jaundice treatment decreased LDL-C values (S-r and D-r) and converged to 220 mg/dL, indicating that S-r and D-r might react markedly to IDL. These changes were consistent with decreases in serum free cholesterol and phospholipid in support of LP-X. By contrast, W-r and K-r data showed upward tendency and also converged to 220 mg/dL. These results suggest that LDL-C direct assay reagents would be classified into 2 groups with respect to the reagent reactivity to LP-X.

Automated measurement method for the determination of vitamin E in plasma lipoprotein classes

In a subendothelial space of atherosclerotic arteries, apolipoprotein B-containing lipoproteins are accumulated and oxidized, and the oxidized lipoproteins promote macrophage foam cell formation. Therefore, the analysis of vitamin E, a major antioxidant in lipoproteins, is important for understanding atherosclerotic pathogenesis. A new method for the automated measurement of vitamin-E (γ- and α-tocopherols) in plasma HDL, LDL, and VLDL was established by using anion-exchange-chromatography for separation of lipoproteins, reverse-phase-chromatography for separation of γ- and α-tocopherols in each of lipoproteins, and fluorescent detection. The within-day assay and between-day assay coefficients of variation for lipoprotein tocopherol levels were 4.73–12.84% and 7.00–14.73%, respectively. The γ- and α-tocopherol/cholesterol ratios of VLDL were higher in healthy plasma than in plasma of untreated patients with dyslipidemia, but the ratios of LDL and HDL were not different. This new estimated method can provide the reliable data of lipoprotein vitamin-E and would be useful for the clinical settings.

Increase of electronegative-LDL-fraction ratio and IDL-cholesterol in chronic kidney disease patients with hemodialysis treatment

Background

It is known that the increased level of IDL and oxidized LDL are associated with risk of cardiovascular disease, and the lipoprotein abnormalities accelerate atherosclerosis. Cardiovascular disease is a major cause of mortality in chronic kidney disease patients with hemodialysis treatment (HD-Ps). Therefore, the estimation of lipoprotein profiles is important for prevention of cardiovascular disease in HD-Ps. We previously established an anion-exchange chromatographic method for measurement of cholesterol level in subclasses of HDL and LDL, IDL, VLDL, and chylomicron. An electronegative-LDL-fraction contained minimally oxidized-LDL. Lipoprotein profile can be accurately and conveniently determined by the new method.

Finding

In this study, lipoprotein profiles in HD-Ps and age-matched healthy subjects were estimated by using our established anion-exchange chromatographic method. The ratio of electronegative-LDL-cholesterol to total LDL-cholesterol and IDL-cholesterol in HD-Ps were significant higher than those in healthy subjects.

Conclusions

The results suggest that the ratio of electronegative-LDL-cholesterol to total LDL-cholesterol and IDL-cholesterol obtained by the new method may serve as useful markers for risk of cardiovascular disease in HD-Ps.

The Underlying Mechanisms for Olanzapine-induced Hypertriglyceridemia

Olanzapine is an efficacious antipsychotic drug often used in the treatment for schizophrenia or bipolar disorder, however, sometimes induces metabolic disorders. We will introduce a patient with bipolar disorder, who has been treated by olanzapine and showed severe hypertriglyceridemia. As a result of measurements of parameters associated with lipid metabolism, very-low density lipoprotein was most important lipoprotein for olanzapin-induced hypertriglyceridemia. The cessation of olanzapine significantly decreased high-sensitivity C-reactive protein and increased adiponectin, proposing that inflammation and reduced adiponectin level may be associated with olanzapin-induced hypertriglyceridemia.

Therapeutic Application of Diacylglycerol Oil for Obesity: Serotonin Hypothesis

Characteristics for the serum lipid abnormalities in the obesity/metabolic syndrome are elevated fasting, postprandial triglyceride (TG), and decreased high-density lipoprotein-cholesterol (HDL-C). Diacylglycerol (DAG) oil ingestion has been reported to ameliorate postprandial hyperlipidemia and prevent obesity by increasing energy expenditure, due to the intestinal physiochemical dynamics that differ from triacylglycerol (TAG). Our study demonstrated that DAG suppresses postprandial increase in TG-rich lipoprotein, very low-density lipoprotein (VLDL), and insulin, as compared with TAG in young, healthy individuals. Interestingly, our study also presented that DAG significantly increases plasma serotonin, which is mostly present in the intestine, and mediates thermogenesis, proposing a possible mechanism for a postprandial increase in energy expenditure by DAG. Our other study demonstrated that DAG suppresses postprandial increase in TG, VLDL-C, and remnant-like particle-cholesterol, in comparison with TAG in an apolipoprotein C-II deficient subject, suggesting that DAG suppresses postprandial TG-rich lipoprotein independently of lipoprotein lipase. Further, to understand the molecular mechanisms for DAG-mediated increase in serotonin and energy expenditure, we studied the effects of 1-monoacylglycerol and 2-monoacylglycerol, distinct digestive products of DAG and TAG, respectively, on serotonin release from the Caco-2 cells, the human intestinal cell line. We also studied effects of 1- and 2-monoacylglycerol, and serotonin on the expression of mRNA associated with β-oxidation, fatty acids metabolism, and thermogenesis, in the Caco-2 cells. 1-monoacylglycerol significantly increased serotonin release from the Caco-2 cells, compared with 2-monoacylglycerol by approximately 40%. The expression of mRNA of acyl-CoA oxidase (ACO), fatty acid translocase (FAT), and uncoupling protein-2 (UCP-2), was significantly higher in 1-MOG-treated Caco-2 cells, than 2-MOG-treated cells. The expression of mRNA of ACO, medium-chain acyl-CoA dehydrogenase, FAT, and UCP-2, was significantly elevated in serotonin-treated Caco-2 cells, compared to cells incubated without serotonin. In conclusion, our clinical and in vitro studies suggested a possible therapeutic application of DAG for obesity, and obesity-related metabolic disorders.Key words: Diacylglycerol, intestine, obesity, serotonin, thermogenesis

Serotonin levels in platelet-poor plasma and whole blood in people with type 2 diabetes with chronic kidney disease

AIMS

Patients with diabetes mellitus (DM) are prone to atherosclerosis. Atherosclerosis activates platelets; activated platelets release serotonin, and therefore, evaluation of serotonin levels in blood could be a valuable biomarker for future risk of cardiovascular events.

METHODS

Plasma serotonin levels obtained from patients with DM complicated with chronic kidney disease were measured using HPLC and were compared to serotonin levels of healthy control subjects. Patients with DM were classified into 2 subgroups of mildly (group 1) and moderately/severely (group 2) impaired renal function.

RESULTS

Serotonin concentration in platelet-poor plasma for group 1 was significantly higher than that of healthy control subjects (p < 0.01), and was significantly higher than that of patients from group 2 (p < 0.05). The concentration of serotonin in whole blood for group 2 patients was significantly lower than that measured from healthy control subjects (p < 0.01). The ratio of the plasma to whole blood level was significantly elevated in both groups 1 and 2 compared with healthy controls (p < 0.01).

CONCLUSIONS

Our results indicate that platelets are activated to release serotonin into plasma in diabetic patients with mildly impaired renal function. When renal damage is advanced, platelets are over-activated to release serotonin.

Release reaction of brain-derived neurotrophic factor (BDNF) through PAR1 activation and its two distinct pools in human platelets

Brain-derived neurotrophic factor (BDNF) is a cytokine that plays important roles in the survival, development, and plasticity of neurons. BDNF is also expressed in peripheral tissues and cells. In this article, we report the BDNF release reaction through thrombin stimulation and its localization in human platelets. Platelets from healthy volunteers were subjected to PAR1-AP or PAR4-AP stimulation. Release of BDNF was measured by ELISA. Localization of BDNF in resting and thrombin-activated platelets was examined by immunoelectron microscopy and sucrose gradient ultracentrifugation following western blotting. BDNF was released dose-dependently with PAR1-AP concentrations with drastic release at low PAR1-AP concentrations and gently release at high PAR1-AP concentrations. Maximum BDNF release was approximately 37% at 132 μM PAR1-AP. In contrast, 3.8% BDNF was released with 1.13 mM PAR4-AP stimulation. In immunoelectron microscopy and sucrose gradient ultracentrifugation analyses, BDNF was detected not only in α-granules but also cytoplasm in of the resting platelets, and it was distributed in the swollen open canalicular system fused to α-granules at 1 min and disappeared at 5 min after stimulation by thrombin. However, BDNF in cytoplasm remained throughout platelet activation. In conclusions, we demonstrate that BDNF is released from platelets through predominately PAR1 regulation. Furthermore, we identified two pools of BDNF in the α-granules and cytoplasm of human platelets, and only BDNF in α-granules is released through platelet activation.

Profiles of inflammatory markers and lipoprotein subclasses in patients undergoing continuous ambulatory peritoneal dialysis

BACKGROUND

Patients undergoing continuous ambulatory peritoneal dialysis (CAPD) often have inflammation and dyslipidemia that accelerate to atherosclerosis. This study aimed to evaluate chronic inflammation and dyslipidemia in CAPD patients.

METHODS

We measured inflammatory markers and lipoprotein subclasses in 20 CAPD patients (12 men and 8 women, aged 59.5 ± 9.9 y) and 20 gender-matched controls. Lipoproteins were separated by high-performance liquid chromatography (HPLC) using an anion-exchange column.

RESULTS

High-sensitivity C-reactive protein and serum amyloid A protein (SAA) were higher among CAPD patients vs. controls (1.6 ± 2.2 vs. 0.8 ± 1.2 mg/l, p<0.05; 11.9 ± 12.8 vs. 4.5 ± 2.4 mg/l). HPLC analysis revealed that chylomicron, VLDL, and IDL cholesterol levels were higher among CAPD vs. controls. In contrast, HDL cholesterol was lower among CAPD patients vs. controls. In the subgroup analysis, SAA levels were significantly lower among patients receiving CAPD for >3 y than among controls. However, IDL cholesterol was consistently higher among CAPD patients vs. controls.

CONCLUSIONS

CAPD patients have chronic inflammation and dyslipidemia. IDL cholesterol is the only lipoprotein subclass that is consistently elevated regardless of CAPD duration. More attention should be paid to dyslipidemia in the management of the CAPD patients.

A molecular mechanism for diacylglycerol-mediated promotion of negative caloric balance

AIMS

A substitution of diacylglycerol (DAG) oil for triacylglycerol (TAG) oil in diet has been reported to reduce body fat and body weight, possibly by increasing postprandial energy expenditure (EE). We have previously studied plasma serotonin, which increases EE and exists in the small intestine, in individuals who ingested TAG and DAG oil, and found that DAG ingestion elevates plasma serotonin levels by about 50% compared with TAG ingestion. We studied the molecular mechanisms for DAG-mediated increase in serotonin and EE.

METHODS

We studied effects of 1-monoacylglycerol and 2-monoacylglycerol, distinct digestive products of DAG and TAG, respectively, on serotonin release from the Caco-2 cells (the human intestinal cell line, n = 8). Further, we studied effects of 1- and 2-monoacylglycerol, and serotonin on expression of mRNA associated with β-oxidation, FA metabolism, and thermogenesis, in the Caco-2 cells (n = 5).

RESULTS

1-monoacylglycerol (100 μM 1-monooleyl glycerol [1-MOG]) significantly increased serotonin release from the Caco-2 cells compared with 2-monoacylglycerol (100 μM 2-MOG) by 36.6%. Expression of mRNA of acyl-CoA oxidase (ACO), fatty acid translocase (FAT), and uncoupling protein-2 (UCP-2) were significantly higher in 100 μM 1-MOG-treated Caco-2 cells than 100 μM 2-MOG-treated cells by 12.8%, 23.7%, and 35.1%, respectively. Further, expression of mRNA of ACO, medium-chain acyl-CoA dehydrogenase, FAT, and UCP-2 were significantly elevated in serotonin (400 nM)-treated Caco-2 cells compared with cells incubated without serotonin by 28.7%, 30.1%, and 39.2%, respectively.

CONCLUSIONS

Our study demonstrated that 1-monoacylglycerol, a digestive product of DAG, increases serotonin release from the Caco-2 cells, and enhances expression of genes associated with β-oxidation, FA metabolism, and thermogenesis, and that serotonin increases expression of these genes, proposing a novel molecular mechanism for DAG-mediated promotion of negative caloric balance.

Analysis of cholesterol levels in lipoprotein(a) with anion-exchange chromatography

We previously established an analysis method for determining the cholesterol levels of five major lipoprotein classes [HDL, LDL, intermediate density lipoprotein (IDL), VLDL, and chylomicrons] in serum by an anion-exchange (AEX)-HPLC method, but lipoprotein(a) [Lp(a)], a well-known risk factor for atherosclerotic diseases, was not determinable. Therefore, we established new AEX-HPLC separation conditions for analyzing the cholesterol levels of six lipoprotein classes, including Lp(a). Serum lipoproteins were separated by HPLC with a diethylaminoethyl-ligand nonporous polymer-based column by elution with a stepwise gradient of the sodium perchlorate concentration. In this improved method, HDL, LDL, IDL, VLDL, chylomicrons, and Lp(a) were each eluted from the column. The cholesterol levels of the eluted lipoproteins were measured enzymatically by a postcolumn reaction. The within-day assay and between-day assay coefficients of variation for the lipoprotein cholesterol levels were in the ranges of 0.29-11.86% and 0.57-11.99%, respectively. The Lp(a) cholesterol levels determined by AEX-HPLC were significantly correlated with the amounts of Lp(a) protein measured by an immunoturbidimetry method available commercially (r = 0.9503, P < 0.0001). Taken together, this AEX-HPLC method may be effectively applied to the analysis of serum lipoproteins with high levels of Lp(a).

Measurement of cholesterol concentrations of major serum lipoprotein classes in haemodialysis patients by anion-exchange chromatography

BACKGROUND

Increased triglyceride (TG)-rich lipoproteins and decreased HDL that are implicated in the progression of atherosclerotic vascular diseases, are present in serum samples of patients undergoing haemodialysis (HD) therapy. Therefore, it is important to measure serum TG-rich lipoprotein concentrations to prevent the diseases.

METHODS

The cholesterol concentrations of lipoprotein classes in serum samples from the HD patients (n = 18) and healthy subjects (n = 18) were analysed by our recently developed method of high-performance liquid chromatography (HPLC), in which the lipoprotein classes were separated using an anion-exchange column, and the cholesterol concentrations of each of those were measured enzymatically using a post-column reaction. The ability of fractionated lipoprotein cholesterol determination by this HPLC method is mostly equivalent to the determination ability of an ultracentrifugation (UC).

RESULTS

HDL, LDL, and TG-rich lipoproteins, i.e. IDL, VLDL and chylomicrons, were well separated in the chromatograms. HDL cholesterol concentrations in the HD patients were significantly lower than in the healthy subjects (P < 0.0001), and IDL cholesterol concentrations and VLDL cholesterol concentrations in the HD patients were significantly higher than in the healthy subjects (P < 0.05). Profiles of these measured lipoprotein values were consistent with the previously reported lipoprotein values, measured ultracentrifugally characteristic of HD patients.

CONCLUSION

These results suggest that the HPLC method may be sufficiently applied to the assessment of serum lipoprotein profile in HD patients in place of the other method including an UC.

Characteristic comparison of triglyceride-rich remnant lipoprotein measurement between a new homogenous assay (RemL-C) and a conventional immunoseparation method (RLP-C)

BACKGROUND

Increased serum remnant lipoproteins are supposed to predict cardiovascular disease in addition to increased LDL. A new homogenous assay for remnant lipoprotein-cholesterol (RemL-C) has been developed as an alternative to remnant-like particle-cholesterol (RLP-C), an immunoseparation assay, widely used for the measurement of remnant lipoprotein cholesterol.

METHODS

We evaluated the correlations and data validation between the 2 assays in 83 subjects (49 men and 34 women) without diabetes, hypertension and medications for hyperlipidemia, diabetes, and hypertension, and investigated the characteristics of remnant lipoproteins obtained by the two methods (RLP-C and RemL-C) and their relationships with IDL-cholesterol determined by our developed HPLC method.

RESULTS

A positive correlation was significantly found between the two methods (r = 0.853, 95%CI 0.781-0.903, p < 0.0001). Bland & Altman analysis revealed that RemL-C values were likely to be significantly higher than RLP-C values, particularly in samples with high levels of remnant lipoproteins. Several data dissociations between the RemL-C and RLP-C were also observed. The HPLC chromatograms show high concentrations of chylomicron cholesterol in serum samples with RemL-C level < RLP-C level, but high concentrations of IDL-cholesterol in samples with RemL-C level > RLP-C level. RemL-C (r = 0.339, 95%CI 0.152-0.903; p = 0.0005) significantly correlated with IDL-cholesterol, but not RLP-C (r = 0.17, 95%CI -0.047-0.372; p = 0.1237) in all the samples (n = 83).

CONCLUSION

These results suggest that there is generally a significant correlation between RemL-C and RLP-C. However, RemL-C assay is likely to reflect IDL more closely than RLP-C.

Effects of diacylglycerol on glucose, lipid metabolism, and plasma serotonin levels in lean Japanese

OBJECTIVE

Diacylglycerol (DAG)-rich oil has been suggested to suppress postprandial hyperlipidemia and promote negative caloric balance by increasing energy expenditure (EE), due to small intestine physiochemical dynamics that differ from triacylglycerol (TAG). We studied the effect of DAG on postprandial glucose/insulin metabolism by loading of carbohydrate with oil. Further, to reveal the mechanism for increased EE by DAG, we measured plasma serotonin, which is mostly present in the small intestine and mediates peripheral sympathetic thermogenesis.

METHODS AND PROCEDURES

Randomized crossover study with 2-week wash-out interval between differing fat ingestion. Seven male, lean, Japanese students ingested DAG or TAG oil with 40 g of carbohydrate. Measurements of metabolic parameters were performed before and at 2, 4, and 6 h after fat ingestion. Plasma serotonin levels and cholesterol concentration in each lipoprotein were measured using high-performance liquid chromatography (HPLC).

RESULTS

The substitution of DAG for TAG decreased very-low-density lipoprotein-cholesterol (VLDL-C) by 45.6% at 2 h, and decreased serum insulin by 41.3% at 4 h after ingestion. The incremental area under the curve (IAUC) for VLDL-C was positively correlated with the IAUC for insulin. Concurrently, DAG elevated plasma serotonin levels by 47.3% at 2 h, while TAG did not influence.

DISCUSSION

This study indicates that the substitution of DAG for TAG suppresses the postprandial increase in serum VLDL-C and insulin. This study also demonstrates that DAG ingestion increases plasma serotonin, proposing a possible mechanism for a postprandial increase in EE by DAG.

Comparative study between anion-exchange HPLC and homogeneous assay methods in regard to the accuracy of high- and low-density lipoprotein cholesterol measurement

OBJECTIVES

A convenient method based on anion-exchange HPLC was recently developed to determine cholesterol levels of lipoproteins (HDL, LDL, IDL, VLDL, and chylomicron). The present study was performed to compare this HPLC method to homogenous assay in regard to measurement accuracy of HDL and LDL cholesterol.

DESIGN AND METHODS

Serum samples (n=105), including three samples from cholestasis patients, were measured by homogenous assay with Cholestest-LDL and CholestestN-HDL (Daiichi Chemicals, Tokyo) and by HPLC as reported previously (J Lipid Res 2003; 44: 1404-12).

RESULTS

The homogenous assay for HDL cholesterol correlated strongly with the HPLC method for HDL cholesterol (r=0.976). Two samples from cholestasis patients could not be measured by homogenous assay but were measured by HPLC. The homogenous assay for LDL cholesterol correlated modestly with the HPLC method for LDL cholesterol (r=0.823). Three outlier samples, from cholestasis patients with serum cholesterol levels >17 mmol/L, were observed in this correlation analysis. Homogenous assay data showed that these LDL cholesterol levels were 15.2-34.7 mmol/L. However, HPLC data showed that these LDL cholesterol levels were 3.6-8.2 mmol/L, and that the major lipoprotein fractions were VLDL and IDL. The difference in LDL cholesterol levels (homogenous assay data minus HPLC data) was positively correlated with VLDL cholesterol levels.

CONCLUSIONS

When measuring samples from cholestasis patients, homogenous assay may give inaccurate results. In contrast, the HPLC method is likely to be capable of accurately measuring HDL and LDL cholesterol levels without the involving VLDL.

Platelet release of β-thromboglobulin and platelet factor 4 and serotonin in plasma samples

OBJECTIVES

Platelet release of alpha granule-derived CXC chemokines and dense granule-derived serotonin in plasma samples was evaluated.

METHODS

Concentrations of the CXC chemokines beta-TG and PF4 were assayed by an enzyme immunoassay; serotonin was measured by an HPLC method.

RESULTS

Beta-TG and PF4 were more easily released than serotonin by in vitro procedures. Use of the anti-platelet cocktail CTAD and preservation of the samples at 4 degrees C were necessary to accurately measure beta-TG and PF4, but not serotonin.

CONCLUSIONS

Assaying serotonin may be useful for assessing platelet activation in vivo as a laboratory test because of facile preparation of plasma samples.

Implications of decreased serum adiponectin for type IIb hyperlipidaemia and increased cholesterol levels of very-low-density lipoprotein in type II diabetic patients

The present study was performed to investigate the relevance of cholesterol levels of plasma lipoproteins [HDL (high-density lipoprotein), LDL (low-density lipoprotein), IDL (immediate-density lipoprotein), VLDL (very-LDL) and chylomicrons] determined by a novel HPLC method, with adiponectin, which is decreased in Type II diabetes and assumed to be involved in dysregulated metabolism and atherogenesis. Type II diabetic patients who were not treated with insulin, statins and fibrates were enrolled. Study subjects included Type II diabetic patients with normolipidaemia (DM-NL; n=15), type 4 hyperlipidaemia (DM-T4HL; n=13), Type IIa hyperlipidaemia (DM-T2aHL; n=15) and Type IIb hyperlipidaemia (DM-T2bHL; n=13). Fasting blood samples were collected. The serum adiponectin level was lower in DM-T2bHL than in any of the other groups. Cholesterol levels of each lipoprotein fraction, serum triacylglycerol (triglyceride), remnant-like particle-cholesterol, fasting plasma glucose, HbA1c (glycated haemoglobin), age, gender difference and BMI (body mass index) were incorporated into a stepwise regression analysis as independent variables. VLDL-cholesterol correlated inversely with adiponectin independently of age, BMI, gender difference and glycaemic control. Although the mechanisms remain to be explored, serum adiponectin was reduced particularly in Type II diabetics with type IIb hyperlipidaemia and correlated inversely with VLDL-cholesterol. Measuring VLDL-cholesterol may be helpful for understanding the pathological features of diabetic dyslipidaemia.

Increased serum iron may contribute to enhanced oxidation of low-density lipoprotein in smokers in part through changes in lipoxygenase and catalase

BACKGROUND

Increased oxidative stress is considered to be causative for cardiovascular disease (CVD) in smokers, but its mechanisms are still unclear. We compared oxidative stress markers between male smokers and male nonsmokers.

METHODS

Twenty-three healthy men (11 nonsmokers and 12 smokers) were enrolled, and blood samples after 12 h of fasting were collected to assess plasma lipids and oxidative stress markers. The effects of iron loading on 12-lipoxygenase (12-LO) expression and activity in human umbilical vein endothelial cells (HUVECs) were tested in vitro to investigate the relevance of iron to oxidation potential in vivo.

RESULTS

Higher levels of plasma-oxidized low-density lipoprotein (LDL) and lipid peroxide (LPO), and higher oxidizability of LDL were observed in smokers than in nonsmokers. Higher levels of serum iron and lower levels of plasma vitamin E were observed in smokers than in nonsmokers. Stepwise multiple regression analysis showed that serum iron was an independent determinant for both plasma-oxidized LDL and lag time of LDL oxidation. Iron loading enhanced 12-LO expression threefold and its activity 1.5-fold. Moreover, iron loading decreased catalase expression by 50% and significantly reduced its activity by 75%.

CONCLUSIONS

Enhanced oxidative stress in smokers may be due to increased iron levels. Iron-induced modulation of expression and activity of 12-LO and catalase may be relevant to increased iron-related oxidative stress as observed in smokers.

[Relevance of lipoprotein cholesterol levels measured by HPLC method to appearance midband on electrophoresis and remnant-like particle (RLP)-cholesterol levels]

We have recently developed an HPLC method able to separate five lipoproteins (HDL, LDL, IDL, VLDL and chylomicron) followed by cholesterol measurement on each lipoprotein. As an application of this method, this study focused on analyses of triglyceride (TG)-rich lipoproteins, one of risk factor for atherosclerosis. The appearance of midband on electrophoresis is conceivably implicated in atherogenesis. The present study revealed that cholesterol levels in VLDL, IDL and LDL were significantly higher in midband-positive sera than negative sera. Cholesterol levels in remnant-like proteins, another atherogenic indicator, were significantly related to those in VLDL and Chylomicron measured by the present HPLC method. In conclusion, this novel HPLC method can provide valuable information for analyses on TG-rich lipoproteins.

[Serotonin: a novel marker for atherosclerotic vascular disease]

Serotonin is released from nerve terminals distributed at the intestinal chromaffin cells, which are taken up into platelets. The serotonin is released at the site where platelets are activated in such situations as atherosclerotic vascular lesions. Therefore, we assumed that the serotonin level could be a suitable marker for atherosclerosis. We developed a new high-performance liquid chromatographic (HPLC) method, including a column-switching system and a post-column reaction with benzylamine, for measurement of serotonin levels in samples from patients with coronary heart disease. The vacuum tubes containing the 3mg/ml (7.4mmol/l) of ethylenediaminetetraacetic acid dipotassium (EDTA2K) were used for collecting the samples of platelet-poor plasma (PPP) because the concentration of anticoagulant in the commercially available vacuum tube containing the 1-2mg/ml (2.5-5.0mmol/l) of EDTA2K was not enough. The serotonin levels in PPP and whole blood of healthy subjects and 4 groups of patients with effort angina pectoris (e-AP), unstable angina (u-AP), old myocardial infarction (OMI), and vasospstic angina pectoris (VSAP), were determined by using the developed method. The serotonin levels in PPP from patients of u-AP, OMI, and VSAP were significantly higher than those of healthy subjects(p<0.001, p<0.005, and p<0.001). The ratio of PPP to whole blood of all disease groups were significantly higher than those of healthy subjects (p<0.001). From these findings, we propose that serotonin is useful as a novel marker for atherosclerotic vascular disease.

The ratio of plasma to whole-blood serotonin may be a novel marker of atherosclerotic cardiovascular disease

Because atherosclerotic vascular lesions stimulate platelets, the platelets release serotonin (5-hydroxytryptamine, aka 5-HT). We therefore measured 5-HT concentrations not only in platelet-poor plasma but also in whole blood as a means of assessing vascular lesions. The plasma concentration of 5-HT tended to increase with age, whereas that in whole blood decreases. Therefore the ratio of the plasma to the whole-blood concentration of 5-HT (P/WB) increases with age. This may be a result of the activation of platelets in older subjects with atherosclerotic vascular damage. Patients who underwent coronary angiography (CAG) were classified into 4 groups according to diagnosis: effort-induced angina pectoris (eAP), old myocardial infarction (OMI), vasospastic angina pectoris (VSAP), and unstable angina (uAP). The mean plasma 5-HT concentration was significantly (P <.01) greater in patients with eAP, uAP, OMI, and VSAP than in healthy controls, whereas the concentration in whole blood was lower in patients with eAP than in healthy controls. When the P/WB ratios were calculated, the mean levels in all disease groups were significantly higher than that in the healthy controls. These findings suggested that 5-HT is released into the plasma from the platelets and that the concentration in the platelets decreases in patients with atherosclerosis.

High-performance liquid chromatographic method with column-switching and post-column reaction for determination of serotonin levels in platelet-poor plasma

OBJECTIVES

Measurement of serotonin concentrations in blood is considered to be important for the clinical studies of diseases involving vascular endothelial injury. We have developed a high-performance liquid chromatographic (HPLC) method for measurement of serotonin level in platelet-poor plasma (PPP).

METHODS

Venous blood samples were collected using vacuum tubes containing ethylenediaminetetraacetic acid (EDTA) dipotassium salt; the optimum concentration in blood was 7.4 mmol/l. Serotonin in samples was separated by HPLC with a column-switching system, and was specifically converted into a fluorescent derivative with benzylamine for convenient detection.

RESULTS

The between-day assay coefficient of variation for a serotonin level (5.1 nmol/l) in PPP was 6.2%. The mean concentration of serotonin in PPP in healthy subjects was 5.7 +/- 3.0 nmol/l. The serotonin levels in PPP in patients with ischemic heart disease were significantly higher than those in healthy subjects (P = 0.001).

CONCLUSIONS

The developed method had sufficient performance to determine serotonin levels in PPP from patients with ischemic heart disease.