Effects of Recombinant Human Lecithin Cholesterol Acyltransferase on Lipoprotein Metabolism in Humans

BACKGROUND

LCAT (lecithin cholesterol acyl transferase) catalyzes the conversion of unesterified, or free cholesterol, to cholesteryl ester, which moves from the surface of HDL (high-density lipoprotein) into the neutral lipid core. As this iterative process continues, nascent lipid-poor HDL is converted to a series of larger, spherical cholesteryl ester-enriched HDL particles that can be cleared by the liver in a process that has been termed reverse cholesterol transport.

METHODS

We conducted a randomized, placebocontrolled, crossover study in 5 volunteers with atherosclerotic cardiovascular disease, to examine the effects of an acute increase of recombinant human (rh) LCAT via intravenous administration (300-mg loading dose followed by 150 mg at 48 hours) on the in vivo metabolism of HDL APO (apolipoprotein)A1 and APOA2, and the APOB100-lipoproteins, very low density, intermediate density, and low-density lipoproteins.

RESULTS

As expected, recombinant human LCAT treatment significantly increased HDL-cholesterol (34.9 mg/dL; P≤0.001), and this was mostly due to the increase in cholesteryl ester content (33.0 mg/dL; P=0.014). This change did not affect the fractional clearance or production rates of HDL-APOA1 and HDL-APOA2. There were also no significant changes in the metabolism of APOB100-lipoproteins.

CONCLUSIONS

Our results suggest that an acute increase in LCAT activity drives greater flux of cholesteryl ester through the reverse cholesterol transport pathway without significantly altering the clearance and production of the main HDL proteins and without affecting the metabolism of APOB100-lipoproteins. Long-term elevations of LCAT might, therefore, have beneficial effects on total body cholesterol balance and atherogenesis.

Metabolomic signatures associated with depression and predictors of antidepressant response in humans: A CAN-BIND-1 report

One of the biggest challenges in treating depression is the heterogeneous and qualitative nature of its clinical presentations. This highlights the need to find quantitative molecular markers to tailor existing treatment strategies to the individual's biological system. In this study, high-resolution metabolic phenotyping of urine and plasma samples from the CAN-BIND study collected before treatment with two common pharmacological strategies, escitalopram and aripiprazole, was performed. Here we show that a panel of LDL and HDL subfractions were negatively correlated with depression in males. For treatment response, lower baseline concentrations of apolipoprotein A1 and HDL were predictive of escitalopram response in males, while higher baseline concentrations of apolipoprotein A2, HDL and VLDL subfractions were predictive of aripiprazole response in females. These findings support the potential of metabolomics in precision medicine and the possibility of identifying personalized interventions for depression.

CA19-9 and apolipoprotein-A2 isoforms as detection markers for pancreatic cancer: a prospective evaluation

Recently, we identified unique processing patterns of apolipoprotein A2 (ApoA2) in patients with pancreatic cancer. Our study provides a first prospective evaluation of an ApoA2 isoform ("ApoA2-ATQ/AT"), alone and in combination with carbohydrate antigen 19-9 (CA19-9), as an early detection biomarker for pancreatic cancer. We performed ELISA measurements of CA19-9 and ApoA2-ATQ/AT in 156 patients with pancreatic cancer and 217 matched controls within the European EPIC cohort, using plasma samples collected up to 60 months prior to diagnosis. The detection discrimination statistics were calculated for risk scores by strata of lag-time. For CA19-9, in univariate marker analyses, C-statistics to distinguish future pancreatic cancer patients from cancer-free individuals were 0.80 for plasma taken ≤6 months before diagnosis, and 0.71 for >6-18 months; for ApoA2-ATQ/AT, C-statistics were 0.62, and 0.65, respectively. Joint models based on ApoA2-ATQ/AT plus CA19-9 significantly improved discrimination within >6-18 months (C = 0.74 vs. 0.71 for CA19-9 alone, p = 0.022) and ≤ 18 months (C = 0.75 vs. 0.74, p = 0.022). At 98% specificity, and for lag times of ≤6, >6-18 or ≤ 18 months, sensitivities were 57%, 36% and 43% for CA19-9 combined with ApoA2-ATQ/AT, respectively, vs. 50%, 29% and 36% for CA19-9 alone. Compared to CA19-9 alone, the combination of CA19-9 and ApoA2-ATQ/AT may improve detection of pancreatic cancer up to 18 months prior to diagnosis under usual care, and may provide a useful first measure for pancreatic cancer detection prior to imaging.

Clinical Significance of Plasma Apolipoprotein-AII Isoforms as a Marker of Pancreatic Exocrine Disorder for Patients with Pancreatic Adenocarcinoma Undergoing Chemoradiotherapy, Paying Attention to Pancreatic Morphological Changes

BACKGROUND

Circulating apolipoprotein-AII (apoAII-) ATQ/AT is a potential useful biomarker for early stage pancreatic ductal adenocarcinoma (PDAC), but its clinical significance in PDAC patients remains uncertain. The aim of the current study was to assess the usefulness of apoAII-ATQ/AT as a surrogate for the effect of chemoradiotherapy (CRT) and its association with pancreatic exocrine disorder, paying attention to morphological changes of the pancreas.

METHODS

In the 264 PDAC patients who were enrolled in our CRT protocol, the following parameters were measured at specified time points before and after CRT: serum levels of albumin, total cholesterol, and amylase as indices of pancreatic exocrine function, serum levels of CA19-9, and the pancreatic morphology including tumor size (TS), main pancreatic duct diameter (MPDD), and pancreatic parenchymal volume excluding tumor volume (PPV) by using computed tomography (CT) images. Plasma apoAII-ATQ/AT levels were simultaneously measured with enzyme-linked immunosorbent assay in 4 healthy volunteers and the 44 PDAC patients before and after CRT. Plasma apoAII-ATQ/AT levels after CRT were analyzed according to small/large-MPDD and small/large-PPV groups based on their median values after CRT. Plasma samples after CRT were measured after incubation with human pancreatic juice (PJ) to examine the relevance between apoAII isoforms and circulating pancreatic enzymes.

RESULTS

The serum levels of albumin, amylase, CA19-9, TS, MPDD, and PPV after CRT were significantly lower than those before CRT (median, before vs. after: 3.9 g/dl, 74 U/l, 180.2 U/ml, 58.1 mm, 4.0 mm, and 34.8 ml vs. 3.8, 59, 43.5, 55.6, 3.6, and 25.2). ApoAII-ATQ/AT levels (median, μg/ml) of PDAC patients before CRT were significantly lower than those in healthy volunteers: 32.9 vs. 61.2, and unexpectedly those after CRT significantly decreased: 14.7. The reduction rate of apoAII-ATQ/AT was not correlated with those of CA19-9 and TS, indicating that apoAII-ATQ/AT is not a tumor-specific marker. On the other hand, the patient group with large MPDD and small PV exhibited higher apoAII-ATQ levels than those with small MPDD and large PPV. The incubation of plasma samples after CRT with PJ did not alter apoAII-ATQ/AT and apoAII-AT levels but significantly decreased apoAII-ATQ levels, suggesting that circulating pancreatic enzymes markedly influenced apoAII-ATQ levels.

CONCLUSIONS

ApoAII-ATQ/AT levels are not useful for evaluation of clinical effect of CRT for PDAC, but apoAII isoforms are very useful to assess pancreatic exocrine disorder because pancreatic atrophy and insufficient secretion of circulating pancreatic enzymes are considered likely to influence apoAII-ATQ levels.

Effects of gender, age and menopausal status on serum apolipoprotein concentrations

OBJECTIVE

To undertake a comprehensive evaluation of apolipoprotein risk markers for cardiovascular disease (CVD) according to gender, age and menopausal status.

DESIGN

Cross-sectional analysis of independent associations of gender, age and menopause with serum apolipoproteins.

PARTICIPANTS

Apparently healthy Caucasian premenopausal (n = 109) and postmenopausal (n = 252) women not taking oral contraceptives or hormone replacement, and Caucasian men (n = 307).

MEASUREMENTS

Serum apolipoprotein (apo) B, A-I and A-II concentrations were measured, plus serum total cholesterol, low-density and high-density lipoprotein cholesterol (LDL-C and HDL-C, respectively), triglycerides, cholesterol in HDL subfractions and the apoB/apoA-I, LDL-C/apoB, HDL-C/apoA-I and HDL-C/apoA-II ratios. Analyses were undertaken with and without standardization for confounding characteristics and in 5-year age ranges.

RESULTS

Overall, apoB concentrations were highest in men but in women rose with age and menopause to converge, in the age range of 50-55 years, with concentrations in men. The LDL-C/apoB ratio was generally higher in women than in men. ApoA-I concentrations were highest in postmenopausal women and lowest in men (standardized median (IQR) 144 (130, 158) vs 119 (108, 132) g/l, respectively, P < 0·001). ApoA-II concentrations were also highest in postmenopausal women but were lowest in premenopausal women (40·3 (37·5, 44·5) vs 32·9 (30·5, 35·7) g/l, respectively, P < 0·001). Nevertheless, postmenopausal women had HDL-C/apoA-I and HDL-C/apoA-II ratios approaching the lowest ratios, which were seen in men.

CONCLUSIONS

Consistent with adverse effects on CVD risk, male gender, ageing in women and menopause were associated with increased apoB concentrations, and menopause and male gender were associated with a decreased cholesterol content of HDL particles.

Posttranslational modifications of apolipoprotein A-II proteoforms in type 2 diabetes

BACKGROUND

Apolipoprotein A-II (apoA-II) is the second most abundant protein in high-density lipoprotein particles. However, it exists in plasma in multiple forms. The effect of diabetes on apoA-II proteoforms is not known.

OBJECTIVE

Our objective was to characterize plasma apoA-II proteoforms in participants with and without type 2 diabetes.

METHODS

Using a novel mass spectrometric immunoassay, the relative abundance of apoA-II proteoforms was examined in plasma of 30 participants with type 2 diabetes and 25 participants without diabetes.

RESULTS

Six apoA-II proteoforms (monomer, truncated TQ monomer, truncated Q monomer, dimer, truncated Q dimer, and truncated 2Qs dimer) and their oxidized proteoforms were identified. The ratios of oxidized monomer and all oxidized proteoforms to the native apoA-II were significantly greater in the diabetic group (P = .004 and P = .005, respectively) compared with the nondiabetic group.

CONCLUSION

The relative abundance of oxidized apoA-II is significantly increased in type 2 diabetes.

Interaction of dietary fat intake with APOA2, APOA5 and LEPR polymorphisms and its relationship with obesity and dyslipidemia in young subjects

BACKGROUND

Diet is an important environmental factor that interacts with genes to modulate the likelihood of developing disorders in lipid metabolism and the relationship between diet and genes in the presence of other chronic diseases such as obesity. The objective of this study was to analyze the interaction of a high fat diet with the APOA2 (rs3813627 and rs5082), APOA5 (rs662799 and rs3135506) and LEPR (rs8179183 and rs1137101) polymorphisms and its relationship with obesity and dyslipidemia in young subjects.

METHODS

The study included 200 young subjects aged 18 to 25 years (100 normal-weight and 100 obese subjects). Dietary fat intake was measured using the frequency food consumption questionnaire. Genotyping of polymorphisms was performed by PCR-RFLP.

RESULTS

Individuals carrying the APOA5 56 G/G genotype with a high saturated fatty acid consumption (OR = 2.7, p = 0.006) and/or total fat (OR = 2.4, p = 0.018), associated with an increased risk of obesity. We also found that A/G + G/G genotypes of the 668 A/G polymorphism in the LEPR gene with an intake ≥ 12 g/d of saturated fatty acids, have 2.9 times higher risk of obesity (p = 0.002), 3.8 times higher risk of hypercholesterolemia (p = 0.002) and 2.4 times higher risk of hypertriglyceridemia (p = 0.02), than those with an intake <12 g/d of saturated fatty acids. Similarly, LEPR 668 A/G + G/G carriers with a high fat total intake had 3.0 times higher risk of obesity (p = 0.002) and 4.1 times higher risk of hypercholesterolemia (p = 0.001).

CONCLUSION

Our results suggest that dietary fat intake modifies the effect of APOA5 and LEPR polymorphisms on serum triglycerides, cholesterol levels and obesity in young subjects.

APOA II genotypes frequency and their interaction with saturated fatty acids consumption on lipid profile of patients with type 2 diabetes

BACKGROUND & AIM

Several studies have suggested that APOA II-265T/C polymorphism affect lipid profile. The aim of this study was to investigate the effect of -265T/C APOA II polymorphism and saturated fatty acids (SFA) intake interaction on lipid profile in diabetic population who are at risk for lipid disorders.

METHODS

In this cross sectional study, 697 type 2 diabetic patients participated. Food consumption data were collected using validated semi-quantitative FFQ during the last year. Realtime-PCR was used to determine APOA II-265T/C genotypes. The interaction between the genotypes and SFA intake with lipid profile was tested using analysis of covariance (ANCOVA).

RESULTS

According to APOA II-265T/C (rs5082) genotype distribution results, CC genotype with a frequency of 12.9% and TC with that of 47.7% showed the lowest and highest frequency in our population, respectively. CC genotype subjects had significantly lower total cholesterol, triglyceride, Cholesterol/HDL-c ratio and non-HDL cholesterol than T allele carriers (p = 0.009, p = 0.02, p = 0.02 and p = 0.002, respectively). The interaction between genotype and SFA intake contributed to significant higher levels of LDL-c and LDL/HDL in CCs (p = 0.05 and p = 0.01), suggesting vulnerability of these individuals to high intake of SFA in the diet.

CONCLUSION

APOA II polymorphism may influence the saturated fatty acid intake required to prevent dyslipidemia in the type 2 diabetic population.

Hot spots in apolipoprotein A-II misfolding and amyloidosis in mice and men

ApoA-II is the second-major protein of high-density lipoproteins. C-terminal extension in human apoA-II or point substitutions in murine apoA-II cause amyloidosis. The molecular mechanism of apolipoprotein misfolding, from the native predominantly α-helical conformation to cross-β-sheet in amyloid, is unknown. We used 12 sequence-based prediction algorithms to identify two ten-residue segments in apoA-II that probably initiate β-aggregation. Previous studies of apoA-II fragments experimentally verify this prediction. Together, experimental and bioinformatics studies explain why the C-terminal extension in human apoA-II causes amyloidosis and why, unlike murine apoA-II, human apoA-II normally does not cause amyloidosis despite its unusually high sequence propensity for β-aggregation.

Apolipoprotein A-II influences apolipoprotein E-linked cardiovascular disease risk in women with high levels of HDL cholesterol and C-reactive protein

Background

In a previous report by our group, high levels of apolipoprotein E (apoE) were demonstrated to be associated with risk of incident cardiovascular disease in women with high levels of C-reactive protein (CRP) in the setting of both low (designated as HR1 subjects) and high (designated as HR2 subjects) levels of high-density lipoprotein cholesterol (HDL-C).

To assess whether apolipoprotein A-II (apoA-II) plays a role in apoE-associated risk in the two female groups.

Methodology/Principal

Outcome event mapping, a graphical data exploratory tool; Cox proportional hazards multivariable regression; and curve-fitting modeling were used to examine apoA-II influence on apoE-associated risk focusing on HDL particles with apolipoprotein A-I (apoA-I) without apoA-II (LpA-I) and HDL particles with both apoA-I and apoA-II (LpA-I:A-II). Results of outcome mappings as a function of apoE levels and the ratio of apoA-II to apoA-I revealed within each of the two populations, a high-risk subgroup characterized in each situation by high levels of apoE and additionally: in HR1, by a low value of the apoA-II/apoA-I ratio; and in HR2, by a moderate value of the apoA-II/apoA-I ratio. Furthermore, derived estimates of LpA-I and LpA-I:A-II levels revealed for high-risk versus remaining subjects: in HR1, higher levels of LpA-I and lower levels of LpA-I:A-II; and in HR2 the reverse, lower levels of LpA-I and higher levels of LpA-I:A-II. Results of multivariable risk modeling as a function of LpA-I and LpA-I:A-II (dichotomized as highest quartile versus combined three lower quartiles) revealed association of risk only for high levels of LpA-I:A-II in the HR2 subgroup (hazard ratio 5.31, 95% CI 1.12–25.17, p = 0.036). Furthermore, high LpA-I:A-II levels interacted with high apoE levels in establishing subgroup risk.

Conclusions/Significance

We conclude that apoA-II plays a significant role in apoE-associated risk of incident CVD in women with high levels of HDL-C and CRP.

Discovery and identification of serum biomarkers of Wilms' tumor in mice using proteomics technology

BACKGROUND

Wilms' tumor (nephroblastoma) is a cancer of the kidneys that occurs typically in children and rarely in adults. Early diagnosis is very important for the treatment and prognosis of the disease. The aim of our study was to discover and identify potential non-invasive and convenient biomarkers for the diagnosis of Wilms' tumor.

METHODS

Nude mice were used to construct a Wilms' tumor model by injecting nephroblastoma cells into their bilateral abdomen. We collected 94 serum samples from mice consisting of 45 samples with Wilms' tumor and 49 controls. The serum proteomic profiles of the samples were analyzed via surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. The candidate biomarkers were purified by high-performance liquid chromatography, identified by liquid chromatography-mass spectrometry, and validated using ProteinChip immunoassays.

RESULTS

We finally retrieved two differential proteins (m/z 4509.2; 6207.9), which were identified as apolipoprotein A-II and polyubiquitin, respectively. The expression of apolipoprotein A-II was higher in the Wilms' tumor group than in the control group (P < 0.01). By contrast, the expression of polyubiquitin was lower in the Wilms' tumor group than in the control group.

CONCLUSION

Apolipoprotein A-II and polyubiquitin may be used as potential biomarkers for nephroblastoma in children, and the analysis of apolipoprotein A-II may help diagnose and treat Wilms' tumor.

Validation of serum amyloid α as an independent biomarker for progression-free and overall survival in metastatic renal cell cancer patients

BACKGROUND

We recently identified apolipoprotein A2 (ApoA2) and serum amyloid α (SAA) as independent prognosticators in metastatic renal cell carcinoma (mRCC) patients, thereby improving the accuracy of the Memorial-Sloan Kettering Cancer Center (MSKCC) model.

OBJECTIVE

Validate these results prospectively in a separate cohort of mRCC patients treated with tyrosine kinase inhibitors (TKIs).

DESIGN, SETTING, AND PARTICIPANTS

For training we used 114 interferon-treated mRCC patients (inclusion 2001-2006). For validation we studied 151 TKI-treated mRCC patients (inclusion 2003-2009).

MEASUREMENTS

Using Cox proportional hazards regression analysis, SAA and ApoA2 were associated with progression-free survival (PFS) and overall survival (OS). In 72 TKI-treated patients, SAA levels were analyzed longitudinally as a potential early marker for treatment effect.

RESULTS AND LIMITATIONS

Baseline ApoA2 and SAA levels significantly predicted PFS and OS in the training and validation cohorts. Multivariate analysis identified SAA in both separate patient sets as a robust and independent prognosticator for PFS and OS. In contrast to our previous findings, ApoA2 interacted with SAA in the validation cohort and did not contribute to a better predictive accuracy than SAA alone and was therefore excluded from further analysis. According to the tertiles of SAA levels, patients were categorized in three risk groups, demonstrating accurate risk prognostication. SAA as a single biomarker showed equal prognostic accuracy when compared with the multifactorial MSKCC risk mode. Using receiver operating characteristic analysis, SAA levels >71 ng/ml were designated as the optimal cut-off value in the training cohort, which was confirmed for its significant sensitivity and specificity in the validation cohort. Applying SAA >71 ng/ml as an additional risk factor significantly improved the predictive accuracy of the MSKCC model in both independent cohorts. Changes in SAA levels after 6-8 wk of TKI treatment had no value in predicting treatment outcome.

CONCLUSIONS

SAA but not ApoA2 was shown to be a robust and independent prognosticator for PFS and OS in mRCC patients. When incorporated in the MSKCC model, SAA showed additional prognostic value for patient management.

Determination of myeloperoxidase-induced apoAI-apoAII heterodimers in high-density lipoprotein

Myeloperoxidase secreted by macrophages and neutrophils in atherosclerotic lesions generates a tyrosyl radical in apolipoprotein (apo) AI, a major protein component of high-density lipoprotein (HDL), thus inducing the formation of apoAI-apoAII heterodimers. It can also cause nitration and chlorination of tyrosine residues. Determining the apoAI-apoAII heterodimer could provide useful information as to functional changes in HDL and/or the progression of atherosclerotic lesions. To this end, the apoAI-apoAII heterodimer was identified in normal human serum by immunoblotting; the band intensity was increased by treatment with myeloperoxidase. This apparent increase in heterodimer formation was quantitatively confirmed by ELISA. In normal human serum, a significant correlation between the concentrations of apoAI-apoAII heterodimer and free apoAII (r=0.763), but not free apoAI (r=0.093), was observed, indicating that heterodimer formation is likely induced on HDL particles carrying both apoAI and apoAII (Lp-AI/AII). In preliminary studies, the levels of apoAI-apoAII heterodimer were statistically higher in plasma from subjects with acute myocardial infarction (AMI) as compared to controls. These findings indicate the possibility that the apoAI-apoAII heterodimer, including nitration and chlorination modifications, may serve as an indicator of atherosclerotic lesions.

Mechanism of action of a peroxisome proliferator-activated receptor (PPAR)-delta agonist on lipoprotein metabolism in dyslipidemic subjects with central obesity

CONTEXT

Dyslipidemia increases the risk of cardiovascular disease in obesity. Peroxisome proliferator-activated receptor (PPAR)-δ agonists decrease plasma triglycerides and increase high-density lipoprotein (HDL)-cholesterol in humans.

OBJECTIVE

The aim of the study was to examine the effect of GW501516, a PPAR-δ agonist, on lipoprotein metabolism. Design, Setting, and Intervention: We conducted a randomized, double-blind, crossover trial of 6-wk intervention periods with placebo or GW501516 (2.5 mg/d), with 2-wk placebo washout between treatment periods.

PARTICIPANTS

We recruited 13 dyslipidemic men with central obesity from the general community.

MAIN OUTCOME MEASURES

We measured the kinetics of very low-density lipoprotein (VLDL)-, intermediate-density lipoprotein-, and low-density lipoprotein (LDL)-apolipoprotein (apo) B-100, plasma apoC-III, and high-density lipoprotein (HDL) particles (LpA-I and LpA-I:A-II).

RESULTS

GW501516 decreased plasma triglycerides, fatty acid, apoB-100, and apoB-48 concentrations. GW501516 decreased the concentrations of VLDL-apoB by increasing its fractional catabolism and of apoC-III by decreasing its production rate (P < 0.05). GW501516 reduced VLDL-to-LDL conversion and LDL-apoB production. GW501516 increased HDL-cholesterol, apoA-II, and LpA-I:A-II concentrations by increasing apoA-II and LpA-I:A-II production (P < 0.05). GW501516 decreased cholesteryl ester transfer protein activity, and this was paralleled by falls in the triglyceride content of VLDL, LDL, and HDL and the cholesterol content of VLDL and LDL.

CONCLUSIONS

GW501516 increased the hepatic removal of VLDL particles, which might have resulted from decreased apoC-III concentration. GW501516 increased apoA-II production, resulting in an increased concentration of LpA-I:A-II particles. This study elucidates the mechanism of action of this PPAR-δ agonist on lipoprotein metabolism and supports its potential use in treating dyslipidemia in obesity.

Apolipoprotein A-II and adiponectin as determinants of very low-density lipoprotein apolipoprotein B-100 metabolism in nonobese men

Data from cellular systems and transgenic animal models suggest a role of apolipoprotein (apo) A-II in the regulation of very low-density lipoprotein (VLDL) metabolism. However, the precise mechanism whereby apoA-II regulates VLDL metabolism remains to be elucidated in humans. In this study, we examined the associations between the kinetics of high-density lipoprotein (HDL)-apoA-II and VLDL-apoB-100 kinetics, and plasma adiponectin concentrations. The kinetics of HDL-apoA-II and VLDL-apoB-100 were measured in 37 nonobese men using stable isotope techniques. Plasma adiponectin concentration was measured using immunoassays. Total plasma apoA-II concentration was positively associated with HDL-apoA-II production rate (PR) (r = 0.734, P < .01); both were positively associated with plasma triglyceride concentration (r = 0.360 and 0.369, respectively) and VLDL-apoB-100 PR (r = 0.406 and 0.427, respectively), and inversely associated with plasma adiponectin concentration (r = -0.449 and -0.375, respectively). Plasma adiponectin was inversely associated with plasma triglyceride concentration (r = -0.327), VLDL-apoB-100 concentration (r = -0.337), and VLDL-apoB-100 PR (r = -0.373). In multiple regression models including waist circumference and plasma insulin, plasma adiponectin concentration was an independent determinant of total plasma apoA-II concentration (β-coefficient = -0.508, P = .001) and HDL-apoA-II PR (β-coefficient = -0.374, P = .03). Conversely, total plasma apoA-II concentration (β-coefficient = 0.348, P = .047) and HDL-apoA-II PR (β-coefficient = -0.350, P = .035) were both independent determinants of VLDL-apoB-100 PR. However, these associations were not independent of plasma adiponectin. Variation in HDL apoA-II production, and hence total plasma apoA-II concentration, may exert a major effect on VLDL-apoB-100 production. Plasma adiponectin may also contribute to the variation in VLDL-apoB-100 production partly by regulating apoA-II transport.

Effects of aleglitazar, a balanced dual peroxisome proliferator-activated receptor α/γ agonist on glycemic and lipid parameters in a primate model of the metabolic syndrome

BACKGROUND

Glycemic control and management of dyslipidemia to reduce cardiovascular risk are major therapeutic goals in individuals with type 2 diabetes mellitus (T2DM). This study was performed to evaluate the effects of aleglitazar, a balanced dual peroxisome proliferator-activated receptor α/γ (PPARα/γ) agonist, on both lipid and glycemic parameters in obese, hypertriglyceridemic, insulin-resistant rhesus monkeys.

METHODS

A 135-day efficacy study was performed in six rhesus monkeys. After a 28-day baseline assessment (vehicle only), monkeys received oral aleglitazar 0.03 mg/kg per day for 42 days, followed by a 63-day washout period. Plasma levels of markers of glycemic and lipid regulation were measured at baseline, at the end of the dosing period, and at the end of the washout period.

RESULTS

Compared with baseline values, aleglitazar 0.03 mg/kg per day reduced triglyceride levels by an average of 89% (328 to 36 mg/dL; P = 0.0035 when normalized for baseline levels) and increased high-density lipoprotein cholesterol levels by 125% (46 to 102 mg/dL; P = 0.0007). Furthermore, aleglitazar reduced low-density lipoprotein cholesterol levels (41%) and increased levels of apolipoprotein A-I (17%) and A-II (17%). Aleglitazar also improved insulin sensitivity by 60% (P = 0.001). Mean body weight was reduced by 5.9% from baseline values with aleglitazar at this dose (P = 0.043).

CONCLUSIONS

Aleglitazar, a dual PPARα/γ agonist, has beneficial effects on both lipid and glucose parameters and may have a therapeutic role in modifying cardiovascular risk factors and improving glycemic control in patients with T2DM.

The effect of fenofibrate on HDL cholesterol and HDL particle concentration in postmenopausal women on tibolone therapy

BACKGROUND

Low high-density lipoprotein (HDL) cholesterol and particle concentration are risk factors for coronary heart disease in women. Tibolone lowers HDL cholesterol and HDL particle concentration, an effect that could be reversed by the peroxisome proliferator-activator receptor-α agonist fenofibrate.

OBJECTIVE

To assess the effects of fenofibrate on plasma HDL particles in postmenopausal women taking tibolone therapy.

DESIGN AND PARTICIPANTS

Randomized crossover study conducted in a women's health clinic. Fourteen postmenopausal women taking tibolone 2.5 mg daily for menopausal symptoms were randomized to either fenofibrate 160 mg daily or no treatment for 8 weeks, followed by a 3-week wash-out for fenofibrate and then crossed over to alternate therapy for another 8 weeks. The main outcome measure was changes in plasma HDL cholesterol concentration, apoA-I and apoA-II, LpA-I and LpA-I-A-II.

RESULTS

After 8 weeks of fenofibrate therapy, there was no change in HDL cholesterol, 1.13 ± 0.06 v 1.16 ± 0.06 mmol/l (P = 0.47) or apoA-I, 1.19 ± 0.05 v 1.20 ± 0.05 g/l (P = 0.23). LpA-I fell significantly 0.35 ± 0.03 v 0.29 ± 0.02 (P = 0.02) but there was a rise in apoA-II, 0.35 ± 0.01 v 0.39 ± 0.01 g/l (P = 0.01). There was a significant fall in total cholesterol, triglycerides, low-density lipoprotein cholesterol and apoB.

CONCLUSION

In women taking tibolone, fenofibrate increases plasma apoA-II concentration and effects a redistribution of HDL subfractions but does not correct tibolone-induced changes in HDL cholesterol or HDL particle concentration. The mechanism and significance of this require further investigation.

Ability of traditional lipid ratios and apolipoprotein ratios to predict cardiovascular risk in people with type 2 diabetes

AIMS/HYPOTHESIS

The apolipoprotein B (ApoB):apolipoprotein A (ApoA)-I ratio may be a better indicator of cardiovascular disease (CVD) risk in people with type 2 diabetes than traditional lipid risk markers (LDL-cholesterol, HDL-cholesterol and triacylglycerol), but whether the ApoB:ApoA-I ratio should be used to indicate lipid-lowering therapy is still debated.

METHODS

The Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study randomised 9,795 patients with type 2 diabetes to fenofibrate (200 mg daily) or placebo and followed them up for a median of 5 years. We compared ApoB, ApoA-I, ApoAII and the ApoB:ApoA-I ratio with traditional lipid variables as predictors of CVD risk. We estimated the HR of the effect of 1 SD difference in baseline concentrations of lipids, apolipoproteins and respective ratios on the risk of CVD events and also used receiver operating characteristic curve analysis.

RESULTS

In the placebo group, the variables best predicting CVD events were non-HDL-cholesterol:HDL-cholesterol, total cholesterol:HDL-cholesterol (HR 1.21, p < 0.001 for both), ApoB:ApoA-I (HR 1.20, p < 0.001), LDL-cholesterol:HDL-cholesterol (HR 1.17, p < 0.001), HDL-cholesterol (HR 0.84, p < 0.001) and ApoA-I (HR 0.85, p < 0.001). In the fenofibrate group, the first four predictors were very similar (but ApoB:ApoA-I was fourth), followed by non-HDL-cholesterol and ApoB. Lipid ratios and ApoB:ApoA-I performed better than any single lipid or apolipoprotein in predicting CVD risk.

CONCLUSIONS/INTERPRETATION

In patients with type 2 diabetes in the FIELD study, traditional lipid ratios were as strong as the ApoB:ApoA-I ratio in predicting CVD risk. The data provide little evidence for replacement of traditional lipids and their ratios with measures of ApoB, ApoA-I and their ratio.

[Gel electrophoresis analysis on plasma differential protein in patients with unstable angina of blood-stasis pattern]

OBJECTIVE

To seek the plasma differential proteins in patients with unstable angina of blood-stasis pattern (UA-BSS) for exploring the proteomic specialty in them by way of two-dimensional difference gel electrophoresis (DIGE) detection on plasma of patients and healthy persons.

METHODS

Using DIGE and tandem mass spectrometry, comparative proteomic study was conducted on the plasma of 12 UA patients of qi-deficiency and blood-stasis pattern (UA-QBS), 12 UA patients of phlegm-stasis cross-blocking pattern (UA-PSS) and 12 healthy volunteers.

RESULTS

Preliminary results showed that Haptoglobin beta chain, DBP, HBB, HBA, Transthyretin, ApoA- I, ApoA-IV were significantly differentially expressed in both patterns, while Haptoglobin alpha1 chain, alpha-1-acid glycoprotein, ApoC-III, ApoA-II, ApoC-II, ApoJ, and Haptoglobin alpha 2 chain were only seen differentially expressed in the UA-PSS patients, alpha1-antitrypsin, Fibrinogen gamma chain, and Fibrin beta were only seen differentially expressed in UA-QBS patients.

CONCLUSION

The common proteomics characteristics of patients of QBS and PSS patterns may be correlated with inflammatory reaction and metabolic disturbance (including blood lipid and blood oxygen).

Lipid abnormalities predict progression of renal disease in patients with type 1 diabetes

AIMS/HYPOTHESIS

We studied the impact of baseline lipid variables on the progression of renal disease in a large nationwide prospective cohort of patients with type 1 diabetes.

METHODS

A total of 2,304 adult patients with type 1 diabetes and available lipid profiles participating in the Finnish Diabetic Nephropathy Study (FinnDiane) were evaluated. Data on progression of renal disease were verified from medical files and patients were followed for 5.4 +/- 2.0 (mean +/- SD) years.

RESULTS

High triacylglycerol, apolipoprotein (Apo) B, ApoA-II and HDL(3)-cholesterol concentrations predicted incident microalbuminuria. Progression to macroalbuminuria was predicted by high triacylglycerol and ApoB. When AER was entered into the model, triacylglycerol was no longer an independent predictor, but when patients with normal AER and microalbuminuria at baseline were pooled, triacylglycerol, HbA(1c), male sex and AER were all independent predictors of renal disease. High total cholesterol, LDL-cholesterol, non-HDL-cholesterol and triacylglycerol as well as low HDL-cholesterol, HDL(2)-cholesterol, ApoA-I and ApoA-II concentrations were predictive of progression to end-stage renal disease. However, when estimated GFR was entered into the model, only total cholesterol remained an independent predictor of progression.

CONCLUSIONS/INTERPRETATION

Lipid abnormalities, particularly high triacylglycerol concentrations, increase the risk of progression of renal disease.

Homologue of mammalian apolipoprotein A-II in non-mammalian vertebrates

Although apolipoprotein with molecular weight 14 kDa (apo-14 kDa) is associated with fish plasma high-density lipoproteins (HDLs), it remains to be determined whether apo-14 kDa is the homologue of mammalian apoA-II. We have obtained the full cDNA sequences that encode Japanese eel and rainbow trout apo-14 kDa. Homologues of Japanese eel apo-14 kDa sequence could be found in 14 fish species deposited in the DDBJ/EMBL/GenBank or TGI database. Fish apo-14 kDa lacks propeptide and contains more internal repeats than mammalian apoA-II. Nevertheless, phylogenetic analysis allowed fish apo-14 kDa to be the homologue of mammalian apoA-II. In addition, in silico cloning of the TGI, Ensembl, or NCBI database revealed apoA-IIs in dog, chicken, green anole lizard, and African clawed frog whose sequences had not so far been available, suggesting both apoA-I and apoA-II as fundamental constituents of vertebrate HDLs.

Influence of cholesteryl ester transfer protein, peroxisome proliferator-activated receptor alpha, apolipoprotein E, and apolipoprotein A-I polymorphisms on high-density lipoprotein cholesterol, apolipoprotein A-I, lipoprotein A-I, and lipoprotein A-I:A-II concentrations: the Prospective Epidemiological Study of Myocardial Infarction study

The plasma level of high-density lipoprotein cholesterol (HDL-C) is known to be inversely associated with cardiovascular risk. However, besides lifestyle, gene polymorphism may influence the HDL-C concentration. The aim of this study was to investigate the possibility of interactions between CETP, PPARA, APOE, and APOAI polymorphisms and HDL-C, apolipoprotein (apo) A-I, lipoprotein (Lp) A-I, and Lp A-I:A-II in a sample selected from the Prospective Epidemiological Study of Myocardial Infarction (PRIME) study population who remained free of cardiovascular events over 5 years of follow-up. Healthy individuals (857) were randomly selected for genotyping the PRIME study subjects. The population was selected so as to provide 25% of subjects in the lowest tertile of HDL-C (< or = 28 mg/dL) in the whole PRIME study sample, 25% of subjects in the highest tertile of HDL-C (> or = 73 mg/dL), and 50% of subjects in the medium tertile of HDL-C (28-73 mg/dL). Genotyping was performed by using a polymerase chain reaction system with predeveloped TaqMan allelic discrimination assay. The CETP A373P rare allele c was less frequent in the group of subjects with high HDL-C, apo A-I, Lp A-I, and Lp A-I:A-II concentrations. Apolipoprotein A-I and Lp A-I were also found to be higher in the presence of the epsilon2 allele coding for APOE. The effect of the CETP A373P rare allele c on HDL-C was independent of all tested parameters except triglycerides. The respective effect of these polymorphisms and triglycerides on cardiovascular risk should be evaluated prospectively.

Dose-dependent regulation of high-density lipoprotein metabolism with rosuvastatin in the metabolic syndrome

BACKGROUND

Low plasma concentration of high-density lipoprotein (HDL) cholesterol is a risk factor for cardiovascular disease and a feature of the metabolic syndrome. Rosuvastatin has been shown to increase HDL cholesterol concentration, but the mechanisms remain unclear.

METHODS AND RESULTS

Twelve men with the metabolic syndrome were studied in a randomized, double-blind, crossover trial of 5-wk therapeutic periods with placebo, 10 mg/d rosuvastatin, or 40 mg/d rosuvastatin, with 2-wk placebo washout between each period. Compared with placebo, there was a significant dose-dependent increase in HDL cholesterol, HDL particle size, and concentration of HDL particles that contain apolipoprotein A-I (LpA-I). The increase in LpA-I concentration was associated with significant dose-dependent reductions in triglyceride concentration and LpA-I fractional catabolic rate, with no changes in LpA-I production rate. There was a significant dose-dependent reduction in the fractional catabolic rate of HDL particles containing both apolipoprotein A-I and A-II (LpA-I:A-II), with concomitant reduction in LpA-I:A-II production rate, and hence no change in LpA-I:A-II concentration.

CONCLUSIONS

Rosuvastatin dose-dependently increased plasma HDL cholesterol and LpA-I concentrations in the metabolic syndrome. This could relate to reduction in plasma triglycerides with remodeling of HDL particles and reduction in LpA-I fractional catabolism. The findings contribute to understanding mechanisms for the HDL-raising effect of rosuvastatin in the metabolic syndrome with implications for reduction in cardiovascular disease.

Detection of specifically oxidized apolipoproteins in oxidized HDL

Atherosclerosis is associated with dysfunctional HDL, and oxidation of HDL is thought to give rise to HDL becoming dysfunctional. Lipoprotein oxidation represents a complex series of processes that can be assessed by various methods. In general, oxidation mediated by 1-electron or radical oxidants gives rise to lipid hydroperoxides (LOOHs) as the primary product. These LOOHs may then undergo further reactions giving rise to secondary lipid oxidation products and/or oxidation of lipoprotein-associated proteins. Thus, LOOHs specifically oxidize Met residues of apolipoprotein (apo) A-I and A-II (the major proteins of HDL) to MetO. Here we describe an HPLC-based method to detect oxidized HDL containing specifically oxidized forms of apoA-I and apoA-II. This method may be useful to assess the early stages of HDL oxidation in biological samples.

Apolipoprotein-AII concentrations are associated with liver steatosis in patients with chronic hepatitis C

It has been shown that the hepatitis C virus (HCV) core protein reduces the activity of the microsomal triglyceride transfer protein (MTP) and could lead to steatosis in HCV-infected patients. Experimentally, apolipoprotein-AII (apoAII), which restores triglyceride secretion altered by the HCV core protein, could be protective against HCV steatosis. On the other hand, increasing plasma concentrations of mouse apoAII in transgenic mice produced several aspects of insulin-resistance syndrome, which also is implicated in the pathogenesis of HCV steatosis. This study was designed to investigate the role of apoAII in HCV-related steatosis in humans. Sixty-five hospitalized patients with chronic HCV were included in this study to assess the effects of apoAII, body mass index (BMI), age, insulin sensibility (HOMA), and leptin level on steatosis. Steatosis was observed in 55.3% of patients. Apo-AII was significantly associated with HOMA and with leptin concentrations. In univariate analyses, age, BMI, increased leptin level, increased HOMA, and increased apoAII concentration were associated with steatosis. In multivariate analysis, steatosis was associated with apoAII concentration, age, gender, and BMI. Contrary to previous hypotheses, apoAII is not a protective factor against HCV steatosis but is significantly associated with the development of liver steatosis. The fact that the plasma levels of apoAII correlate with HOMA and leptin levels in HCV-infected patients suggests that apoAII may contribute to hepatic steatosis progression in relationship to visceral obesity, insulin resistance, and metabolism of triglyceride-rich lipoproteins.

Apolipoprotein A-II is catabolized in the kidney as a function of its plasma concentration

We investigated in vivo catabolism of apolipoprotein A-II (apo A-II), a major determinant of plasma HDL levels. Like apoA-I, murine apoA-II (mapoA-II) and human apoA-II (hapoA-II) were reabsorbed in the first segment of kidney proximal tubules of control and hapoA-II-transgenic mice, respectively. ApoA-II colocalized in brush border membranes with cubilin and megalin (the apoA-I receptor and coreceptor, respectively), with mapoA-I in intracellular vesicles of tubular epithelial cells, and was targeted to lysosomes, suggestive of degradation. By use of three transgenic lines with plasma hapoA-II concentrations ranging from normal to three times higher, we established an association between plasma concentration and renal catabolism of hapoA-II. HapoA-II was rapidly internalized in yolk sac epithelial cells expressing high levels of cubilin and megalin, colocalized with cubilin and megalin on the cell surface, and effectively competed with apoA-I for uptake, which was inhibitable by anti-cubilin antibodies. Kidney cortical cells that only express megalin internalized LDL but not apoA-II, apoA-I, or HDL, suggesting that megalin is not an apoA-II receptor. We show that apoA-II is efficiently reabsorbed in kidney proximal tubules in relation to its plasma concentration.

Speciation of Human Plasma High-Density Lipoprotein (HDL): HDL Stability and Apolipoprotein A-I Partitioning

The distribution of apolipoprotein (apo) A-I between human high-density lipoproteins (HDL) and water is an important component of reverse cholesterol transport and the atheroprotective effects of HDL. Chaotropic perturbation (CP) with guanidinium chloride (Gdm-Cl) reveals HDL instability by inducing the unfolding and transfer of apo A-I but not apo A-II into the aqueous phase while forming larger apo A-I deficient HDL-like particles and small amounts of cholesteryl ester-rich microemulsions (CERMs). Our kinetic and hydrodynamic studies of the CP of HDL species separated according to size and density show that (1) CP mediated an increase in HDL size, which involves quasi-fusion of surface and core lipids, and release of lipid-free apo A-I (these processes correlate linearly), (2) >94% of the HDL lipids remain with an apo A-I deficient particle, (3) apo A-II remains associated with a very stable HDL-like particle even at high levels of Gdm-Cl, and (4) apo A-I unfolding and transfer from HDL to water vary among HDL subfractions with the larger and more buoyant species exhibiting greater stability. Our data indicate that apo A-I's on small HDL (HDL-S) are highly dynamic and, relative to apo A-I on the larger more mature HDL, partition more readily into the aqueous phase, where they initiate the formation of new HDL species. Our data suggest that the greater instability of HDL-S generates free apo A-I and an apo A-I deficient HDL-S that readily fuses with the more stable HDL-L. Thus, the presence of HDL-L drives the CP remodeling of HDL to an equilibrium with even larger HDL-L and more lipid-free apo A-I than with either HDL-L or HDL-S alone. Moreover, according to dilution studies of HDL in 3 M Gdm-Cl, CP of HDL fits a model of apo A-I partitioning between HDL phospholipids and water that is controlled by the principal of opposing forces. These findings suggest that the size and relative amount of HDL lipid determine the HDL stability and the fraction of apo A-I that partitions into the aqueous phase where it is destined for interaction with ABCA1 transporters, thereby initiating reverse cholesterol transport or, alternatively, renal clearance.

Association of serum apolipoprotein A-II concentration with combined hyperlipidemia and impaired glucose tolerance

We studied the relationship of serum apolipoprotein A-II concentration with biochemical parameters of lipid and carbohydrate metabolism, type of hyperlipidemia, and insulin sensitivity in male patients with hyperlipidemia. High concentration of apolipoprotein A-II was associated with increased indices of atherogenic lipoproteins and high-density lipoprotein-mediated reverse cholesterol transport, combined hyperlipidemia, and decreased insulin sensitivity calculated with consideration for glucose and insulin levels in glucose tolerance test and body weight.

Cholesteryl ester transfer protein and hyperalphalipoproteinemia in Caucasians

It is unclear whether cholesteryl ester transfer protein (CETP) contributes to high density lipoprotein cholesterol (HDL-C) levels in hyperalphalipoproteinemia (HALP) in Caucasians. Moreover, even less is known about the effects of hereditary CETP deficiency in non-Japanese. We studied 95 unrelated Caucasian individuals with HALP. No correlations between CETP concentration or activity and HDL-C were identified. Screening for CETP gene defects led to the identification of heterozygosity for a novel splice site mutation in one individual. Twenty-five heterozygotes for this mutation showed reduced CETP concentration (-40%) and activity (-50%) and a 35% increase of HDL-C compared with family controls. The heterozygotes presented with an isolated high HDL-C, whereas the remaining subjects exhibited a typical high HDL-C/low-triglyceride phenotype. The increase of HDL-C in the CETP-deficient heterozygotes was primarily attributable to increased high density lipoprotein containing apolipoprotein A-I and A-II (LpAI:AII) levels, contrasting with an increase in both high density lipoprotein containing apolipoprotein A-I only and LpAI:AII in the other group. This study suggests the absence of a relationship between CETP and HDL-C levels in Caucasians with HALP. The data furthermore indicate that genetic CETP deficiency is rare among Caucasians and that this disorder presents with a phenotype that is different from that of subjects with HALP who have no mutation in the CETP gene.

Identification of potential markers for the detection of pancreatic cancer through comparative serum protein expression profiling

OBJECTIVE

Early detection is the only promising approach to significantly improve the survival of patients with pancreatic cancer (PCa). Noninvasive tools for the diagnosis, prognosis, and monitoring of this disease are of urgent need. The purpose of this study was to identify and validate new biomarkers in PCa patient serum samples.

METHODS

Surface-enhanced laser desorption/ionization time-of-flight mass spectrometry has been applied to analyze serum protein alterations associated with PCa and to identify sets of potential biomarkers indicative for this disease. A cohort of 96 serum samples from patients undergoing PCa surgery was compared with sera from 96 healthy volunteers as controls. The sera were fractionated by anion exchange chromatography, and 3 of 6 fractions were analyzed onto 2 different chromatographic arrays.

RESULTS

Data analysis revealed 24 differentially expressed protein peaks (P < 0.001), of which 21 were downregulated in the PCa samples. The best single marker can predict 92% of the controls and 89% of the cancer samples correctly. In addition, multivariate pattern analysis was performed. The best pattern model using a set of 3 markers was obtained using fraction 6 on immobilized metal affinity capture, loaded with Cu-Cu arrays. With this pattern model, a sensitivity of 100% and a specificity of 98% for the training data set and a sensitivity of 83% and specificity of 77% for the test data set were achieved with the PCa group set as true positive. Several of protein peaks, including the best single marker at 17.27 kd and other proteins from the pattern models, were purified and identified by peptide mapping and postsource decay-matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. Apolipoprotein A-II, transthyretin, and apolipoprotein A-I were identified as markers, and these identified proteins were decreased at least 2-fold in PCa serum when compared with the control group.

CONCLUSIONS

PCa is associated with a specific decrease of distinct serum proteins, which allows a reliable differentiation between pancreatic cancer and healthy controls.

Role of LCAT in HDL remodeling: investigation of LCAT deficiency states

To better understand the role of LCAT in HDL metabolism, we compared HDL subpopulations in subjects with homozygous (n = 11) and heterozygous (n = 11) LCAT deficiency with controls (n = 22). Distribution and concentrations of apolipoprotein A-I (apoA-I)-, apoA-II-, apoA-IV-, apoC-I-, apoC-III-, and apoE-containing HDL subpopulations were assessed. Compared with controls, homozygotes and heterozygotes had lower LCAT masses (-77% and -13%), and LCAT activities (-99% and -39%), respectively. In homozygotes, the majority of apoA-I was found in small, disc-shaped, poorly lipidated prebeta-1 and alpha-4 HDL particles, and some apoA-I was found in larger, lipid-poor, discoidal HDL particles with alpha-mobility. No apoC-I-containing HDL was noted, and all apoA-II and apoC-III was detected in lipid-poor, prebeta-mobility particles. ApoE-containing particles were more disperse than normal. ApoA-IV-containing particles were normal. Heterozygotes had profiles similar to controls, except that apoC-III was found only in small HDL with prebeta-mobility. Our data are consistent with the concepts that LCAT activity: 1) is essential for developing large, spherical, apoA-I-containing HDL and for the formation of normal-sized apoC-I and apoC-III HDL; and 2) has little affect on the conversion of prebeta-1 into alpha-4 HDL, only slight effects on apoE HDL, and no effect on apoA-IV HDL particles.

Human apolipoprotein A-II associates with triglyceride-rich lipoproteins in plasma and impairs their catabolism

Postprandial hypertriglyceridemia and low plasma HDL levels, which are principal features of the metabolic syndrome, are displayed by transgenic mice expressing human apolipoprotein A-II (hapoA-II). In these mice, hypertriglyceridemia results from the inhibition of lipoprotein lipase and hepatic lipase activities by hapoA-II carried on VLDL. This study aimed to determine whether the association of hapoA-II with triglyceride-rich lipoproteins (TRLs) is sufficient to impair their catabolism. To measure plasma TRL residence time, intestinal TRL production was induced by a radioactive oral lipid bolus. Radioactive and total triglyceride (TG) were rapidly cleared in control mice but accumulated in plasma of transgenic mice, in relation to hapoA-II concentration. Similar plasma TG accumulations were measured in transgenic mice with or without endogenous apoA-II expression. HapoA-II (synthesized in liver) was detected in chylomicrons (produced by intestine). The association of hapoA-II with TRL in plasma was further confirmed by the absence of hapoA-II in chylomicrons and VLDL of transgenic mice injected with Triton WR 1339, which prevents apolipoprotein exchanges. We show that the association of hapoA-II with TRL occurs in the circulation and induces postprandial hypertriglyceridemia.

Lipoprotein (a) as a determinant of arterial stiffness in elderly patients with type 2 diabetes mellitus

BACKGROUND

Lipoprotein (a) [Lp(a)] is known to be a risk factor for atherosclerotic disease. However, the relationship between Lp(a) and arterial stiffness has not been clarified. We investigated whether atherosclerotic risk factors, including serum Lp(a), are associated with aortic stiffness in elderly patients with type 2 diabetes mellitus.

METHODS

Aortic stiffness, evaluated by using aortic pulse wave velocity, and major atherosclerotic risk factors were measured in elderly (> or =65 years) patients with type 2 diabetes mellitus. Relationships between aortic pulse wave velocity, Lp(a) and other atherosclerotic risk factors were analyzed.

RESULTS

Among the atherosclerotic risk factors measured, age, pulse pressure, hemoglobin A1c (HbA1c), uric acid, fibrinogen, sialic acid and Lp(a) showed significant positive correlations with aortic pulse wave velocity. Lp(a) also showed significant positive correlations with pulse pressure, fibrinogen, sialic acid, apolipoprotein B and apolipoprotein B/apolipoprotein A-I ratio. The correlation between Lp(a) and aortic pulse wave velocity was independent of age, sex, blood hemoglobin A1c, uric acid and fibrinogen, history of diabetic nephropathy and therapy with lipid-lowering drugs. Apolipoprotein A-II showed a significant negative correlation with both aortic pulse wave velocity and Lp(a). The median level of Lp(a) in the highest tertile group of subjects divided by aortic pulse wave velocity was significantly higher than the median Lp(a) level in the lowest tertile. The middle and highest tertile groups of subjects divided by aortic pulse wave velocity showed significantly high odds ratios of high Lp(a) levels (> or =30 mg/dl) vs the lowest tertile.

CONCLUSIONS

Lp(a) is an independent determinant of aortic stiffness in elderly patients with type 2 diabetes mellitus.

Proteomic identification of lower apolipoprotein A-I in Alzheimer's disease

Many researches have been trying to find the potential biomarkers for Alzheimer's disease (AD). We hereby used the proteomics method to search for protein expression differences in the serum between AD patients and controls. We enrolled 59 AD patients and 74 age- and sex-matched controls in this study. Ten AD patients and 10 controls were selected for proteomic analysis. Apolipoprotein A-I (ApoA-I) was found to have a lower expression in the AD group by a proteomics two-dimensional gel electrophoresis study. We further measured the serum ApoA-I level which was significantly lower in the AD patients (112.29 +/- 21.33 mg/dl) in comparison to the controls (144.53 +/- 19.91 mg/dl; p < 0.0002). Lower serum ApoA-I levels might be a potential biomarker for AD.

Factorial study of the effect of n-3 fatty acid supplementation and atorvastatin on the kinetics of HDL apolipoproteins A-I and A-II in men with abdominal obesity

BACKGROUND

Disturbed HDL metabolism in insulin-resistant, obese subjects may account for an increased risk of cardiovascular disease. Fish oils and atorvastatin increase plasma HDL cholesterol, but the underlying mechanisms responsible for this change are not fully understood.

OBJECTIVE

We studied the independent and combined effects of fish oils and atorvastatin on the metabolism of HDL apolipoprotein A-I (apo A-I) and HDL apo A-II in obese men.

DESIGN

We conducted a 6-wk randomized, placebo-controlled, 2 x 2 factorial intervention study of the effects of fish oils (4 g/d) and atorvastatin (40 mg/d) on the kinetics of HDL apo A-I and HDL apo A-II in 48 obese men with dyslipidemia with intravenous administration of [d3]-leucine. Isotopic enrichments of apo A-I and apo A-II were measured with gas chromatography-mass spectrometry with kinetic parameters derived from a multicompartmental model (SAAM II).

RESULTS

Fish oils and atorvastatin significantly decreased plasma triacylglycerols and increased HDL cholesterol and HDL2 cholesterol (P < 0.05 for main effects). A significant (P < 0.02) main effect of fish oils was observed in decreasing the fractional catabolic rate of HDL apo A-I and HDL apo A-II. This was coupled with a significant decrease in the corresponding production rates, accounting for a lack of treatment effect on plasma concentrations of apo A-I and apo A-II. Atorvastatin did not significantly alter the concentrations or kinetic parameters of HDL apo A-I and HDL apo A-II. None of the treatments altered insulin resistance.

CONCLUSIONS

Fish oils, but not atorvastatin, influence HDL metabolism chiefly by decreasing both the catabolism and production of HDL apo A-I and HDL apo A-II in insulin-resistant obese men. Addition of atorvastatin to treatment with fish oils had no additional effect on HDL kinetics compared with fish oils alone.

Plasma phospholipid transfer protein activity is decreased in type 2 diabetes during treatment with atorvastatin: a role for apolipoprotein E?

Plasma phospholipid transfer protein (PLTP) plays an important role in lipoprotein metabolism. PLTP activity is elevated in patients with diabetes, a condition with strongly elevated risk for coronary heart disease. The aim of this study was to test the hypothesis that statins reduce PLTP activity and to examine the potential role of apolipoprotein E (apoE). PLTP activity and apoE were measured in patients with type 2 diabetes from the DALI (Diabetes Atorvastatin Lipid Intervention) Study, a 30-week randomized double-blind placebo-controlled trial with atorvastatin (10 and 80 mg daily). At baseline, PLTP activity was positively correlated with waist circumference, HbA(1c), glucose, and apoE (all P < 0.05). Atorvastatin treatment resulted in decreased PLTP activity (10 mg atorvastatin: -8.3%, P < 0.05; 80 mg atorvastatin: -12.1%, P < 0.002). Plasma apoE decreased by 28 and 36%, respectively (P < 0.001). The decrease in apoE was strongly related to the decrease in PLTP activity (r = 0.565, P < 0.001). The change in apoE remained the sole determinant of the change in PLTP activity in a multivariate model. The activity of PLTP in type 2 diabetes is decreased by atorvastatin. The association between the decrease in PLTP activity and apoE during statin treatment supports the hypothesis that apoE may prevent PLTP inactivation.

Apo-AII is an elevated biomarker of chronic non-human primate ethanol self-administration

AIMS

Serum protein profiles were examined in naïve, ethanol self-administering and ethanol abstinent cynomolgus monkeys (Macaca fasicularis) to search for differences in protein expression which could possibly serve as biomarkers of heavy ethanol consumption.

METHODS

Surface-enhanced laser desorption ionization time-of-flight (SELDI-ToF) mass spectrometry was used for proteomic profiling of serum.

RESULTS

Two proteins were identified by SELDI-ToF to be increased in ethanol self-administering compared with abstinent animals. These proteins were identified to be apolipoprotein AI (Apo-AI) and apolipoprotein AII (Apo-AII) by peptide mass fingerprinting and comparison with spectra of purified human Apo-AI and AII proteins. Immunoblot analysis of Apo-AI and Apo-AII was performed on a separate group of animals (within-animal ethanol-naïve and self-administering) and confirmed a statistically significant increase in Apo-AII, while Apo-AI was unchanged.

CONCLUSIONS

An open proteomic screen of serum and confirmation in a separate set of animals found Apo-AII to be increased in the serum of ethanol self-administering monkeys. These results are consistent with previous clinical studies of human ethanol consumption and serum apolipoprotein expression. Moreover, these results validate the use of non-human primates as a model organism for proteomic analysis of ethanol self-administration biomarkers.

High-density lipoprotein (HDL) transport in the metabolic syndrome: application of a new model for HDL particle kinetics

CONTEXT

Reduced high density lipoprotein (HDL) concentration in the metabolic syndrome (MetS) is associated with increased risk of diabetes and cardiovascular disease and is related to defects in the kinetics of HDL apolipoprotein (apo) A-I and A-II.

OBJECTIVE

The objective of the study was to investigate HDL apoA-I and apoA-II kinetics in nondiabetic men with MetS and lean controls by developing a model that describes the kinetics of lipoprotein (Lp)A-I and LpA-I:A-II particles.

DESIGN

Twenty-three MetS men and 10 age-matched lean controls were investigated. ApoA-I and apoA-II tracer/tracee ratios were studied after iv d3-leucine administration using gas chromatography mass spectrometry.

RESULTS

Compared with lean subjects, MetS subjects had accelerated catabolism of LpA-I (P < 0.001), LpA-I:A-II (P = 0.005), and apoA-II (P = 0.005); the production rate of LpA-I was also significantly elevated in MetS, so that the dominant changes in plasma concentrations were reduction in LpA-I:A-II (P < 0.001) and apoA-II (P < 0.05). Increased catabolism of LpA-I and LpA-I:A-II was directly related to increased waist circumference, hypertriglyceridemia, low HDL-cholesterol, small HDL particle size, hyperinsulinemia, and low phospholipid transfer protein (PLTP) activity; overproduction of LpA-I was significantly associated with increased waist circumference, insulin resistance, and low PLTP activity.

CONCLUSIONS

MetS men exhibit hypercatabolism of the two major HDL lipoprotein particles, LpA-I and LpA-I:A-II, but selective overproduction of LpA-I maintains a normal plasma concentration of LpA-I. These kinetic perturbations are probably related to central obesity, insulin resistance, hypertriglyceridemia, and low plasma PLTP activity.

Effect of Fenofibrate on Plasma Lipoprotein Composition and Kinetics in Patients With Complete Hepatic Lipase Deficiency

Objective— The goal of this study was to characterize the effect of microcoated fenofibrate (160 mg/day for 6 months) on plasma lipoprotein composition and kinetics in 2 patients with complete hepatic lipase (HL) deficiency.

Methods and Results— Fenofibrate treatment normalized the plasma lipoprotein profile of patients with complete HL deficiency, as evidenced by significant reductions in the plasma concentration of cholesterol (−49%) and triglycerides (−82%) and a significant increase in low-density lipoprotein (LDL) size (251.5±1.8 versus 263.5±0.7 Å). The in vivo kinetics of very low–density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and LDL apolipoprotein (apo)B-100 and plasma apoA-I and apoA-II were studied using a primed-constant infusion of L-[5,5,5-D 3 ]-leucine for 12 hours in the fasted state. Fenofibrate treatment in complete HL-deficient patients substantially decreased plasma concentrations of VLDL, IDL, and LDL apoB-100 attributable to important increases in VLDL (+325%), IDL (+129%), and LDL (+218%) apoB-100 fractional catabolic rates (FCR). IDL apoB-100 FCR nevertheless remained 60% lower after treatment compared with values obtained in controls (n=5). The kinetics of plasma apoA-I and apoA-II as well as the capacity of total plasma and of high-density lipoprotein particles to efflux cellular cholesterol from normal human skin fibroblasts was not altered by fenofibrate.

Conclusion— Fenofibrate therapy exerts a pronounced antiatherogenic effect on triglyceride-rich lipoproteins even in the complete absence of HL.

Mass spectral analysis of domestic and wild equine apoA-I and A-II: Detection of unique dimeric forms of apoA-II

In pigs, humans, chimpanzees and probably other great apes, a cysteine at residue 6 enables apolipoprotein A-II to form a homodimer. However, the apoA-IIs of other primates, lacking a cysteine residue, are monomeric. We have already reported that horse apoA-IIs form homodimers due also to a cysteine at residue 6. In this study, we wanted to determine whether other equine apoA-IIs might be monomeric. The high density lipoproteins were ultracentrifugally isolated from the plasmas of a horse (Equus caballus), a donkey (Equus asinus) and five wild equines: two types of zebras (Equus zebra hartmannae and Equus zebra quagga boehmi), a Przewalski's horse (Equus przewalskii), a Somali ass (Equus africanus somalicus) and a kiang (Equus kiang holdereri). Using liquid chromatography with electrospray-ionization mass spectrometry, we were able to obtain accurate values for the molecular masses of apoA-I and apoA-II. Homodimeric apoA-IIs were observed in each of the animals studied. The donkey had unique dimers, consisting of the proapolipoprotein A-II linked by a disulfide bond either to a mature apoA-II monomer or another proapoA-II. In addition, our data indicate that small amounts of apoA-I and apoA-II apparently are acylated.

Formation of high density lipoproteins containing both apolipoprotein A-I and A-II in the rabbit

Human plasma HDLs are classified on the basis of apolipoprotein composition into those that contain apolipoprotein A-I (apoA-I) without apoA-II [(A-I)HDL] and those containing apoA-I and apoA-II [(A-I/A-II)HDL]. ApoA-I enters the plasma as a component of discoidal particles, which are remodeled into spherical (A-I)HDL by LCAT. ApoA-II is secreted into the plasma either in the lipid-free form or as a component of discoidal high density lipoproteins containing apoA-II without apoA-I [(A-II)HDL]. As discoidal (A-II)HDL are poor substrates for LCAT, they are not converted into spherical (A-II)HDL. This study investigates the fate of apoA-II when it enters the plasma. Lipid-free apoA-II and apoA-II-containing discoidal reconstituted HDL [(A-II)rHDL] were injected intravenously into New Zealand White rabbits, a species that is deficient in apoA-II. In both cases, the apoA-II was rapidly and quantitatively incorporated into spherical (A-I)HDL to form spherical (A-I/A-II)HDL. These particles were comparable in size and composition to the (A-I/A-II)HDL in human plasma. Injection of lipid-free apoA-II and discoidal (A-II)rHDL was also accompanied by triglyceride enrichment of the endogenous (A-I)HDL and VLDL as well as the newly formed (A-I/A-II)HDL. We conclude that, irrespective of the form in which apoA-II enters the plasma, it is rapidly incorporated into spherical HDLs that also contain apoA-I to form (A-I/A-II)HDL.

Antiandrogenic therapy can cause coronary arterial disease

AIM

To study the change of lipid metabolism by antiandrogen therapy in patients with prostate cancer.

MATERIALS AND METHODS

We studied with a 2.5 years follow-up the changes in plasma cholesterols (C), triglycerides (TG), lipoproteins (LP), and apolipoproteins (Apo) B-100, A-I, and A-II pro fi les in 24 patients of mean age 60 years with low risk prostate cancer (stage: T1cN0M0, Gleason score: 2-5) during treatment with cyproterone acetate (CPA) without surgical management or radiation therapy.

RESULTS

Significant decreases of HDL-C, Apo A-I and Apo A-II and an increase of triglyceride levels in VLDL were induced by CPA. After a period of 2.5 years on CPA treatment, four patients out of twenty-four were found to be affected by coronary heart disease.

CONCLUSIONS

Ischaemic coronary arteriosclerosis with an incidence rate of 16.6% as caused by prolonged CPA therapy is mediated through changes in HDL cholesterol, Apo A-I and Apo A-II pro fi les, other than the well-known hyperglyceridemic effect caused by estrogen.

Dietary Exchange of an Olive Oil and Sunflower Oil Blend for Extra Virgin Olive Oil Decreases the Estimate Cardiovascular Risk and LDL and Apolipoprotein AII Concentrations in Postmenopausal Women

BACKGROUND

Dietary supplementation with Virgin olive oil is considered cardioprotective. Decreasing LDL and apolipoprotein (apo) AII-lipoproteins is also appropriate for CHD protection and treatment.

AIM

To study the effects of an 8%En dietary exchange of linoleic acid for oleic acid on serum and lipoprotein levels and serum and LDL-TBARS in postmenopausal women consuming a diet rich in fat (46%En; saturated/monounsaturated/polyunsaturated profile: 1.1/1.9/1).

EXPERIMENTAL DESIGN

14 postmenopausal women (63 +/- 11 years) were assigned to exchange during 28-day dietary period the culinary oil used for years consisting in a blend of olive oil plus sunflower oil (SO) for extra virgin olive oil (EVOO). SO and EVOO represented 62% of the total lipid intake. DETERMINATIONS: Dietary intakes, serum Lp(a), and cholesterol, triglycerides, phospholipids, protein, apolipoproteins AI, AII, B were determined in serum and lipoproteins.

RESULTS

The dietary intervention decreased serum total cholesterol (TC), phospholipids, apo AII (all, p < 0.001) and apo B (p < 0.01). Except for triglycerides, all components of the LDL fraction decreased (at least, p < 0.05). HDL-cholesterol was not affected but HDL-phospholipids and HDL-lipids decreased (at least, p < 0.01). VLDL-apo B and VLDL-proteins decreased (all, p < 0.001). Serum Lp(a), TBARS and LDL-TBARS were not affected by the dietary exchange. The estimate of 10-year cardiovascular risk decreased (p < 0.05). Apo AII (p = 0.061) and LDL-cholesterol (p < 0.05) underwent greater modifications in normocholesterolemics, while LDL-phospholipids (p = 0.094), experienced greater alterations in hypercholesterolemics. No significant interaction was observed between dietary exchange and age (> or <65 yrs).

CONCLUSIONS

These findings suggest that the dietary exchange of an olive oil and sunflower oil blend for extra virgin olive decreases LDL and apo AII levels, and the estimate of 10-year cardiovascular risk.

Serum lipids concentration in women with benign and malignant ovarian tumours

Early diagnosis can improve clinical effects of ovarian carcinoma treatment. Until now, a satisfying screening method has not been found. Serum lipid and lipoprotein association with neoplasm is already established. In our study, we have examined concentration of total cholesterol, free cholesterol, HDL cholesterol, HDL3 and HDL free cholesterol fraction, triglycerides, and apolipoproteins: AI, AII and B and aimed to prepare the most likely model of lipid profile in women suffering from ovarian neoplasm. The serum lipid parameters were analysed in 91 operated patients: 64 with ovarian malignant tumour, 27 with benign ovarian cysts and 44 apparently healthy age-matching pair women as a control group.

THE RESULTS

concentration of two parameters: apolipoprotein AI and free cholesterol allows for excluding ovarian neoplasm in 95.5%; examination of six parameters: apolipoprotein AI, free cholesterol, HDL-free cholesterol, HDL total cholesterol, apolipoprotein B and HDL3 fraction allows for diagnosing ovarian malignancy with 97% probability. This probability does not depend on staging of cancer, patient's age, nor BMI. No statistically significant difference between malignant and benign ovarian tumour has been confirmed.

Mass spectral analysis of pig (Sus scrofa) apo HDL: Identification of pig apoA-II, a dimeric apolipoprotein

Comparative studies of mammalian high density lipoproteins have clearly indicated that the major apolipoprotein is apoA-I and in some mammals apoA-II is the second major apolipoprotein. However, in pigs, apoA-II has been considered to be either present in trace amounts or absent. Recently, cDNA sequences for pigs A-II have been entered into the database. Translation of these sequences revealed that pig A-II consisted of 77 amino acids and that a cysteine residue was at residue 6. The A-II of three other mammals, chimpanzees, horses and humans, also has a cysteine residue at this position. As a result of a disulfide bond formed between monomers, the A-II in each of these cases circulates as a homodimer. Using electrospray-ionization mass spectrometry (ESI-MS), we obtained molecular mass data demonstrating that dimeric apoA-II is also present in pig plasma. In addition to being the first to report on the presence of apoA-II in pig plasma, we also obtained values for the molecular masses of apoA-I, apoC-III, apoD and serum amyloid A protein.

Serum levels of an isoform of apolipoprotein A-II as a potential marker for prostate cancer

PURPOSE

We recently showed that protein expression profiling of serum using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) has potential as a diagnostic approach for detection of prostate cancer. As a parallel effort, we have been pursuing the identification of the protein(s) comprising the individual discriminatory "peaks" and evaluating their utility as potential biomarkers for prostate disease.

EXPERIMENTAL DESIGN

We employed liquid chromatography, gel electrophoresis and tandem mass spectroscopy to isolate and identify a protein that correlates with observed SELDI-TOF MS mass/charge (m/z) values. Immunodepletion, immunoassay, and Western analysis were used to verify that the identified protein generated the observed SELDI peak. Subsequent immunohistochemistry was used to examine the expression of the proteins in prostate tumors.

RESULTS

An 8,946 m/z SELDI-TOF MS peak was found to retain discriminatory value in each of two separate data sets with an increased expression in the diseased state. Sequence identification by liquid chromatography-MS/MS and subsequent immunoassays verified that an isoform of apolipoprotein A-II (ApoA-II) is the observed 8,946 m/z SELDI peak. Immunohistochemistry revealed that ApoA-II is overexpressed in prostate tumors. SELDI-based immunoassay revealed that an 8.9-kDa isoform of ApoA-II is specifically overexpressed in serum from individuals with prostate cancer. ApoA-II was also overexpressed in the serum of individuals with prostate cancer who have normal prostate-specific antigen (0-4.0 ng/mL).

CONCLUSIONS

We have identified an isoform of ApoA-II giving rise to an 8.9K m/z SELDI "peak" that is specifically overexpressed in prostate disease. The ability of ApoA-II to detect disease in patients with normal prostate-specific antigen suggests potential utility of the marker in identifying indolent disease.

Plasma factors required for human apolipoprotein A-II dimerization

Although plasma high-density lipoproteins (HDL) have been implicated in several cardioprotective pathways, the physiologic role of apolipoprotein (apo) A-II, the second most abundant of the HDL proteins, remains ambiguous. Human apo A-II is distinguished from most other species by a single cysteine (Cys6), which forms a disulfide bond with other cysteine-containing apos. In human plasma, nearly all apo A-II occurs as disulfide-linked homodimers of 17.4 kDa. Although dimerization is an important determinant of human apo A-II metabolism, its mechanism and the plasma and/or cellular sites of its dimerization are not known. Using SDS-PAGE and densitometry we investigated the kinetics of apo A-II dimerization and observed a slow (t(1/2) = approximately 10 days), second-order process in Tris-buffered saline. In 3 M guanidine hydrochloride, which disrupts apo A-II secondary structure and self-association, the rate was 3-fold slower. In contrast, lipid surfaces that promote apo A-II alpha-helix formation and lipophilic interaction profoundly enhanced the rate. Reassembled HDL increased the second-order rate constant k(2) by 7500-fold, unilamellar 1-palmitoyl-2-oleoylphosphatidylcholine vesicles increased k(2) 850-fold, and physiological concentrations of human serum albumin increased k(2) 220-fold. Thus, while dimerization of apo A-II in aqueous buffer is too slow to account for the high fraction of dimer found in plasma, lipids and proteins "catalyze" dimer formation, a process that could occur either intracellularly prior to secretion or in the plasma compartment following secretion. These data suggest that formation of disulfide links within or between polypeptide chains can be controlled, in part, by coexisting lipids and proteins.

Correlation of high density lipoprotein (HDL)-associated sphingosine 1-phosphate with serum levels of HDL-cholesterol and apolipoproteins

BACKGROUND

Extracellular sphingosine 1-phosphate (S1P) has been shown to contribute to the action of high density lipoprotein (HDL) on endothelial and smooth muscle cells. We examined the relationship of lipoprotein-associated S1P concentrations with cholesterol (C) and apolipoprotein (apo) contents of lipoprotein and lipoprotein subfractions characterized by capillary isotachophoresis (cITP).

METHODS

Blood samples were drawn from 16 volunteers. S1P concentrations were quantified by bioassay based on the ability of S1P to stimulate its receptor. cITP was performed using plasma that had been prestained with NBD-ceramide.

RESULTS

In plasma, S1P was concentrated in HDL and associated with LDL at a much lower concentration. HDL-S1P was the major determinant of the plasma S1P concentration. HDL-S1P was strongly and positively (p<0.001) correlated with serum levels of HDL-C (r=0.82), apo A-I (r=0.91) and apo A-II (r=0.92). HDL-S1P was strongly and positively (p<0.01) correlated with the apo A-I- and apo A-I/apo A-II-containing cITP HDL subfractions [fast HDL-C (r=0.66) and intermediate HDL-C (r=0.80)], but was not significantly correlated with apo E-containing slow HDL, suggesting that S1P is associated with both apo A-I HDL and apo A-I/A-II HDL. LDL-S1P was positively correlated (p<0.01) with levels of LDL-C (r=0.65) and apo B (r=0.85).

CONCLUSION

Lipoprotein-associated S1P was related to the lipoprotein composition of cholesterol and apolipoproteins, suggesting that extracellular S1P may play different roles depending on the particles with which it is associated.