Apolipoprotein E-containing high-density lipoprotein (HDL) modifies the impact of cholesterol-overloaded HDL on incident coronary heart disease risk: A community-based cohort study

Chemically-Induced Lipoprotein Breakdown for Improved Extracellular Vesicle Purification

Extracellular vesicles (EVs) are nanosized biomolecular packages involved in intercellular communication. EVs are released by all cells, making them broadly applicable as therapeutic, diagnostic, and mechanistic components in (patho)physiology. Sample purity is critical for correctly attributing observed effects to EVs and for maximizing therapeutic and diagnostic performance. Lipoprotein contaminants represent a major challenge for sample purity. Lipoproteins are approximately six orders of magnitude more abundant in the blood circulation and overlap in size, shape, and density with EVs. This study represents the first example of an EV purification method based on the chemically-induced breakdown of lipoproteins. Specifically, a styrene-maleic acid (SMA) copolymer is used to selectively breakdown lipoproteins, enabling subsequent size-based separation of the breakdown products from plasma EVs. The use of the polymer followed by tangential flow filtration or size-exclusion chromatography results in improved EV yield, preservation of EV morphology, increased EV markers, and reduced contaminant markers. SMA-based EV purification enables improved fluorescent labeling, reduces interactions with macrophages, and enhances accuracy, sensitivity, and specificity to detect EV biomarkers, indicating benefits for various downstream applications. In conclusion, SMA is a simple and effective method to improve the purity and yield of plasma-derived EVs, which favorably impacts downstream applications.

Cardiometabolic diseases and early cognitive decline: Mitigated by integrated active lifestyle for brain health

BACKGROUND

Cardiometabolic diseases (CMDs) increases the risk of cognitive decline, but the extent to which this can be offset by adherence to an active integrated lifestyle is unknown.

METHODS

This prospective study used the baseline and 2-year follow-up data of 2537 dementia-free elderly ≥60 from PINDEC Project. Lifestyle factors (including physical exercise, social interaction, leisure activities, sleep quality, smoking, and alcohol consumption) were collected and the integrated score was calculated. Participants were divided into three groups based on integrated score tertiles (inactive, ≤3 score; intermediate, 4 score; and active, ≥5). Logistic regression was used in data analysis.

RESULTS

35.2 % participants had 5-6 healthy components, while only 5.4 % had all 6 healthy lifestyles. The multiadjusted odds ratios (ORs, 95 % confidence interval) of early cognitive decline was 1.223 (0.799-1.871) and 1.832 (1.140-2.943) for participants with only one CMD and any two or more CMDs, respectively. An inverse dose-response relationship was found between lifestyle scores and early cognitive decline (Ptrend = 0.017). In participants with active lifestyle, the OR for early cognitive decline comparing the CMDs status of any two or more CMDs vs. CMDs-free was 0.778 (95%CI: 0.302-2.007). Participants with inactive lifestyle and any two or more CMDs had a near 3.4-fold increased risk of early cognitive decline than those without CMDs who had intermediate to active lifestyle (OR = 3.422, 95%CI: 1.764-6.638).

LIMITATIONS

Our research lacks information about nutrition.

CONCLUSIONS

A dose-response relationship exists between CMDs status and risk of early cognitive decline. However, adherence to an active integrated lifestyle may mitigate this risk.

Roles of peripheral lipoproteins and cholesteryl ester transfer protein in the vascular contributions to cognitive impairment and dementia

This narrative review focuses on the role of cholesteryl ester transfer protein (CETP) and peripheral lipoproteins in the vascular contributions to cognitive impairment and dementia (VCID). Humans have a peripheral lipoprotein profile where low-density lipoproteins (LDL) represent the dominant lipoprotein fraction and high-density lipoproteins (HDL) represent a minor lipoprotein fraction. Elevated LDL-cholesterol (LDL-C) levels are well-established to cause cardiovascular disease and several LDL-C-lowering therapies are clinically available to manage this vascular risk factor. The efficacy of LDL-C-lowering therapies to reduce risk of all-cause dementia and AD is now important to address as recent studies demonstrate a role for LDL in Alzheimer's Disease (AD) as well as in all-cause dementia. The LDL:HDL ratio in humans is set mainly by CETP activity, which exchanges cholesteryl esters for triglycerides across lipoprotein fractions to raise LDL and lower HDL as CETP activity increases. Genetic and pharmacological studies support the hypothesis that CETP inhibition reduces cardiovascular risk by lowering LDL, which, by extension, may also lower VCID. Unlike humans, wild-type mice do not express catalytically active CETP and have HDL as their major lipoprotein fraction. As HDL has potent beneficial effects on endothelial cells, the naturally high HDL levels in mice protect them from vascular disorders, likely including VCID. Genetic restoration of CETP expression in mice to generate a more human-like lipid profile may increase the relevance of murine models for VCID studies. The therapeutic potential of existing and emerging LDL-lowering therapies for VCID will be discussed. Figure Legend. Cholesteryl Ester Transfer Protein in Alzheimer's Disease. CETP is mainly produced by the liver, and exchanges cholesteryl esters for triglycerides across lipoprotein fractions to raise circulating LDL and lower HDL as CETP activity increases. Low CETP activity is associated with better cardiovascular health, due to decreased LDL and increased HDL, which may also improve brain health. Although most peripheral lipoproteins cannot enter the brain parenchyma due to the BBB, it is increasingly appreciated that direct access to the vascular endothelium may enable peripheral lipoproteins to have indirect effects on brain health. Thus, lipoproteins may affect the cerebrovasculature from both sides of the BBB. Recent studies show an association between elevated plasma LDL, a well-known cardiovascular risk factor, and a higher risk of AD, and considerable evidence suggests that high HDL levels are associated with reduced CAA and lower neuroinflammation. Considering the potential detrimental role of LDL in AD and the importance of HDL's beneficial effects on endothelial cells, high CETP activity may lead to compromised BBB integrity, increased CAA deposits and greater neuroinflammation. Abbreviations: CETP - cholesteryl transfer ester protein; LDL - low-density lipoproteins; HDL - high-density lipoproteins; BBB - blood-brain barrier; CAA - cerebral amyloid angiopathy, SMC - smooth muscle cells, PVM - perivascular macrophages, RBC - red blood cells.

Dalcetrapib and anacetrapib increase apolipoprotein E-containing HDL in rabbits and humans

The large HDL particles generated by administration of cholesteryl ester transfer protein inhibitors (CETPi) remain poorly characterized, despite their potential importance in the routing of cholesterol to the liver for excretion, which is the last step of the reverse cholesterol transport. Thus, the effects of the CETPi dalcetrapib and anacetrapib on HDL particle composition were studied in rabbits and humans. The association of rabbit HDL to the LDL receptor (LDLr) in vitro was also evaluated. New Zealand White rabbits receiving atorvastatin were treated with dalcetrapib or anacetrapib. A subset of patients from the dal-PLAQUE-2 study treated with dalcetrapib or placebo were also studied. In rabbits, dalcetrapib and anacetrapib increased HDL-C by more than 58% (P < 0.01) and in turn raised large apo E-containing HDL by 66% (P < 0.001) and 59% (P < 0.01), respectively. Additionally, HDL from CETPi-treated rabbits competed with human LDL for binding to the LDLr on HepG2 cells more than control HDL (P < 0.01). In humans, dalcetrapib increased concentrations of large HDL particles (+69%, P < 0.001) and apo B-depleted plasma apo E (+24%, P < 0.001), leading to the formation of apo E-containing HDL (+47%, P < 0.001) devoid of apo A-I. Overall, in rabbits and humans, CETPi increased large apo E-containing HDL particle concentration, which can interact with hepatic LDLr. The catabolism of these particles may depend on an adequate level of LDLr to contribute to reverse cholesterol transport.

Alterations of HDL's to piHDL's Proteome in Patients with Chronic Inflammatory Diseases, and HDL-Targeted Therapies

Chronic inflammatory diseases, such as rheumatoid arthritis, steatohepatitis, periodontitis, chronic kidney disease, and others are associated with an increased risk of atherosclerotic cardiovascular disease, which persists even after accounting for traditional cardiac risk factors. The common factor linking these diseases to accelerated atherosclerosis is chronic systemic low-grade inflammation triggering changes in lipoprotein structure and metabolism. HDL, an independent marker of cardiovascular risk, is a lipoprotein particle with numerous important anti-atherogenic properties. Besides the essential role in reverse cholesterol transport, HDL possesses antioxidative, anti-inflammatory, antiapoptotic, and antithrombotic properties. Inflammation and inflammation-associated pathologies can cause modifications in HDL's proteome and lipidome, transforming HDL from atheroprotective into a pro-atherosclerotic lipoprotein. Therefore, a simple increase in HDL concentration in patients with inflammatory diseases has not led to the desired anti-atherogenic outcome. In this review, the functions of individual protein components of HDL, rendering them either anti-inflammatory or pro-inflammatory are described in detail. Alterations of HDL proteome (such as replacing atheroprotective proteins by pro-inflammatory proteins, or posttranslational modifications) in patients with chronic inflammatory diseases and their impact on cardiovascular health are discussed. Finally, molecular, and clinical aspects of HDL-targeted therapies, including those used in therapeutical practice, drugs in clinical trials, and experimental drugs are comprehensively summarised.

Paradoxical Long-Term Impact Between Serum Apolipoprotein E and High-Density Lipoprotein Cholesterol in Patients Undergoing Percutaneous Coronary Intervention

AIM

Apolipoprotein E (ApoE) strongly affects arteriosclerosis but has atheroprotective effects in combination with high-density lipoprotein cholesterol (HDL-C). The impact of the quantitative relationship between serum ApoE and HDL-C levels in patients with coronary artery disease (CAD) remains unclear.

METHODS

A total of 3632 consecutive patients who underwent their first intervention between 2000 and 2016 were included. They were categorized into normal and abnormal HDL-C groups based on the normal HDL-C value, and each group was subdivided into high and low ApoE subgroups based on the group-specific median ApoE value. We evaluated the incidence of major adverse cardiac and cerebrovascular events (MACCE), including cardiovascular death, non-fatal myocardial infarction, non-fatal stroke, and all-cause death Results: During a 6.4-year follow-up, 419 patients developed MACCE and 570 patients died. The interaction term between ApoE levels and HDL-C status in MACCE and all-cause death proved to be statistically significant. Kaplan-Meier analysis revealed that the cumulative incidence of MACCE was significantly higher for elevated pre-procedural ApoE levels than for reduced preprocedural ApoE levels in the normal HDL-C group. Conversely, the cumulative incidence of MACCE was significantly higher for reduced pre-procedural ApoE levels than for elevated pre-procedural ApoE levels in the abnormal HDL-C group. After adjustment for important covariates, multivariable Cox hazard analysis revealed that the serum ApoE level was a strongly independent predictor of MACCE; this was inversely related in both groups.

CONCLUSIONS

Serum ApoE levels may have a paradoxical impact on the future cardiovascular risk depending on the HDL-C status in patients with CAD.

Complex association of apolipoprotein E-containing HDL with coronary artery disease burden in cardiovascular disease

Background

Although traditional lipid parameters and coronary imaging techniques are valuable for cardiovascular disease (CVD) risk prediction, better diagnostic tests are still needed.

Methods

In a prospective, observational study, 795 individuals had extensive cardiometabolic profiling, including emerging biomarkers, such as apolipoprotein E–containing HDL-cholesterol (ApoE-HDL-C). Coronary artery calcium (CAC) score was assessed in the entire cohort, and quantitative coronary computed tomography angiography (CCTA) characterization of total burden, noncalcified burden (NCB), and fibrous plaque burden (FB) was performed in a subcohort (n = 300) of patients stratified by concentration of ApoE-HDL-C. Total and HDL-containing apolipoprotein C-III (ApoC-III) were also measured.

Results

Most patients had a clinical diagnosis of coronary artery disease (CAD) (n = 80.4% of 795), with mean age of 59 years, a majority being male (57%), and about half on statin treatment. The low ApoE-HDL-C group had more severe stenosis (11% vs. 2%, overall P < 0.001), with higher CAC as compared with high ApoE-HDL-C. On quantitative CCTA, the high ApoE-HDL-C group had lower NCB (β = –0.24, P = 0.0001), which tended to be significant in a fully adjusted model (β = –0.32, P = 0.001) and altered by ApoC-III in HDL levels. Low ApoE-HDL-C was significantly associated with LDL particle number (β = 0.31; P = 0.0001). Finally, when stratified by FB, ApoC-III in HDL showed a more robust predictive value of CAD over ApoE-HDL-C (AUC: 0.705, P = 0.0001) in a fully adjusted model.

Conclusion

ApoE-containing HDL-C showed a significant association with early coronary plaque characteristics and is affected by the presence of ApoC-III, indicating that low ApoE-HDL-C and high ApoC-III may be important markers of CVD severity.

Trial Registration

ClinicalTrials.gov: NCT01621594.

Funding

This work was supported by the NHLBI at the NIH Intramural Research Program.

Evaluation of the apolipoprotein E (apoE)-HDL-associated risk factors for coronary heart disease using duo-functional electrochemical aptasensor

Apolipoprotein E containing high-density lipoprotein (apoE-HDL) and apoE-HDL cholesterol (apoE-HDL-C) are recently recognized as potential biomarkers for coronary heart disease (CHD). We herein developed a two-stage, enzyme-assisted, dual-signal aptasensor that enables a useful electrochemical sensing platform for simultaneous determination of apoE-HDL, apoE-HDL-C, and total HDL-C presented in the sample. The detection scheme consists of two subsystems. In subsystem (I), the level of apoE-HDL is evaluated upon the binding of apoE-specific aptamer and subsequently methylene blue (MB)-labeled DNA displacement occurs on the electrode surface, resulting in electrochemical reduction of methylene blue. In subsystem (II), two kinds of cholesterol levels (apoE-HDL-C and total HDL-C) can be measured. For apoE-HDL-C, the amount of cholesterol in apoE-HDL captured by the aptamer in the first step can be further determined with the aid of surfactant, cholesterol esterase, cholesterol oxidase, and p-aminophenol-mediated electrochemical signal amplification. As for total HDL-C, the amount of cholesterol is determined by the same approach as that used for apoE-HDL-C determination, but without washing (separation). The linear dynamic range for apoE-HDL determination is from 1 to 100 mg/dL (R² = 1.00). For cholesterol standards, the linear dynamic range is determined to be 0-250 mg/dL (R² = 0.98). Finally, serial dilutions of purified human HDL preparations were examined using the newly developed aptasensor; the percentage of apoE-HDL-C to HDL-C was found to be ~10%, which correlated well with previously reported values. In conclusion, we successfully developed an electrochemical aptasensor that allows concurrent quantification of apoE-HDL, apoE-HDL-C, and HDL-C on the same platform, offering an efficient, convenient, and purification-free sensing strategy for predictive CHD biomarkers.

Hepatic paraoxonase 1 ameliorates dysfunctional high-density lipoprotein and atherosclerosis in scavenger receptor class B type I deficient mice

Background

High-density lipoprotein (HDL) plays an antiatherogenic role by mediating reverse cholesterol transport (RCT), antioxidation, anti-inflammation, and endothelial cell protection. Recently, series of evidence have shown that HDL can also convert to proatherogenic HDL under certain circumstances. Plasma paraoxonase 1 (PON1) as an HDL-bound esterase, is responsible for most of the antioxidant properties of HDL. However, whether PON1 can serve as a therapeutic target of dysfunctional HDL-related atherosclerosis remains unclear.

Methods

In this study, scavenger receptor class B type I deficient (Scarb1^−/−) mice were used as the animal model with dysfunctional HDL and increased atherosclerotic susceptibility. Hepatic PON1 overexpression and secretion into circulation were achieved by lentivirus injection through the tail vein. We monitored plasma lipids levels and lipoprotein profiles in Scarb1^−/− mice, and measured the levels and activities of proteins associated with HDL function. Meanwhile, lipid deposition in the liver and atherosclerotic lesions was quantified. Hepatic genes relevant to HDL metabolism and inflammation were analyzed.

Results

The results showed the relative levels of PON1 in liver and plasma were increased by 1.1-fold and 1.6-fold, respectively, and mean plasma PON1 activity was increased by 63%. High-level PON1 increased the antioxidative and anti-inflammatory properties, promoted HDL maturation and macrophage cholesterol efflux through increasing HDL functional proteins components apolipoprotein A1 (APOA1), apolipoprotein E (APOE), and lecithin-cholesterol acyltransferase (LCAT), while decreased inflammatory protein markers, such as serum amyloid A (SAA), apolipoprotein A4 (APOA4) and alpha 1 antitrypsin (A1AT). Furthermore, hepatic PON1 overexpression linked the effects of antioxidation and anti-inflammation with HDL metabolism regulation mainly through up-regulating liver X receptor alpha (LXRα) and its downstream genes. The pleiotropic effects involved promoting HDL biogenesis by raising the level of APOA1, increasing cholesterol uptake by the liver through the APOE-low density lipoprotein receptor (LDLR) pathway, and increasing cholesterol excretion into the bile, thereby reducing hepatic steatosis and aorta atherosclerosis in Western diet-fed mice.

Conclusions

Our study reveals that high-level PON1 improved dysfunctional HDL and alleviated the development of atherosclerosis in Scarb1^−/− mice. It is suggested that PON1 represents a promising target of HDL-based therapeutic strategy for HDL-related atherosclerotic cardiovascular disease.

Cerebrovascular amyloid Angiopathy in bioengineered vessels is reduced by high-density lipoprotein particles enriched in Apolipoprotein E

Background

Several lines of evidence suggest that high-density lipoprotein (HDL) reduces Alzheimer’s disease (AD) risk by decreasing vascular beta-amyloid (Aβ) deposition and inflammation, however, the mechanisms by which HDL improve cerebrovascular functions relevant to AD remain poorly understood.

Methods

Here we use a human bioengineered model of cerebral amyloid angiopathy (CAA) to define several mechanisms by which HDL reduces Aβ deposition within the vasculature and attenuates endothelial inflammation as measured by monocyte binding.

Results

We demonstrate that HDL reduces vascular Aβ accumulation independently of its principal binding protein, scavenger receptor (SR)-BI, in contrast to the SR-BI-dependent mechanism by which HDL prevents Aβ-induced vascular inflammation. We describe multiple novel mechanisms by which HDL acts to reduce CAA, namely: i) altering Aβ binding to collagen-I, ii) forming a complex with Aβ that maintains its solubility, iii) lowering collagen-I protein levels produced by smooth-muscle cells (SMC), and iv) attenuating Aβ uptake into SMC that associates with reduced low density lipoprotein related protein 1 (LRP1) levels. Furthermore, we show that HDL particles enriched in apolipoprotein (apo)E appear to be the major drivers of these effects, providing new insights into the peripheral role of apoE in AD, in particular, the fraction of HDL that contains apoE.

Conclusion

The findings in this study identify new mechanisms by which circulating HDL, particularly HDL particles enriched in apoE, may provide vascular resilience to Aβ and shed new light on a potential role of peripherally-acting apoE in AD.

Methionine sulfoxide reductase A attenuates atherosclerosis via repairing dysfunctional HDL in scavenger receptor class B type I deficient mice

High-density lipoprotein (HDL), a well-known atheroprotective factor, can be converted to proatherogenic particles in chronic inflammation. HDL-targeted therapeutic strategy for atherosclerotic cardiovascular disease (CVD) is currently under development. This study aims to assess the role of methionine sulfoxide reductase A (MsrA) in abnormal HDL and its related disorders in scavenger receptor class B type I deficient (SR-BI^-/- ) mice. First, we demonstrated that MsrA overexpression attenuated ROS level and inflammation in HepG2 cells. For the in vivo study, SR-BI^-/- mice were intravenously injected with lentivirus to achieve hepatic MsrA overexpression. High-level hepatic MsrA significantly reduced the plasma free cholesterol contents, improved HDL functional proteins apolipoprotein A-I (apoAI), apoE, paraoxonase1 (PON1), and lecithin:cholesterol acyltransferase (LCAT), while decreased the pro-inflammatory property of dysfunctional HDL, contributing to reduced atherosclerosis and hepatic steatosis in Western diet-fed mice. Furthermore, the study revealed that hepatic MsrA altered the expression of several genes controlling HDL biogenesis, cholesterol esterification, cholesterol uptake mediated by low-density lipoprotein receptor (LDLR) and biliary excretion, as well as suppressed nuclear factor κB (NF-κB) signaling pathway, which largely relied on liver X receptor alpha (LXRα)-upregulation. These results provide original evidence that MsrA may be a promising target for the therapy of dysfunctional HDL-related CVD.

Advances in HDL: Much More than Lipid Transporters

High Density Lipoprotein (HDL) particles, beyond serving as lipid transporters and playing a key role in reverse cholesterol transport, carry a highly variable number of proteins, micro-RNAs, vitamins, and hormones, which endow them with the ability to mediate a plethora of cellular and molecular mechanisms that promote cardiovascular health. It is becoming increasingly evident, however, that the presence of cardiovascular risk factors and co-morbidities alters HDLs cargo and protective functions. This concept has led to the notion that metrics other than HDL-cholesterol levels, such as HDL functionality and composition, may better capture HDL cardiovascular protection. On the other hand, the potential of HDL as natural delivery carriers has also fostered the design of engineered HDL-mimetics aiming to improve HDL efficacy or as drug-delivery agents with therapeutic potential. In this paper, we first provide an overview of the molecules known to be transported by HDL particles and mainly discuss their functions in the cardiovascular system. Second, we describe the impact of cardiovascular risk factors and co-morbidities on HDL remodeling. Finally, we review the currently developed HDL-based approaches.

Bovine HDL and Dual Domain HDL-Mimetic Peptides Inhibit Tumor Development in Mice

A growing body of literature supports the role of apolipoproteins present in HDL in the treatment of pro-inflammatory diseases including cancer. We examined whether bovine HDL (bHDL) and three dual-domain peptides, namely AEM-28 and its analog AEM-28-2, and HM-10/10, affect tumor growth and development in mouse models of ovarian and colon cancer. We demonstrate that bHDL inhibits mouse colorectal cancer cell line CT26-mediated lung tumor development, and mouse ovarian cancer cell line ID8-mediated tumor burden. We also demonstrate that, although to different degrees, dual-domain peptides inhibit cell viability of mouse and human ovarian and colon cancer cell lines, but not that of normal human colonic epithelial cells or NIH3T3 mouse fibroblasts. Dual-domain peptides administered subcutaneously or in a chow diet decrease CT26 cell-mediated tumor burden, tumor growth, and tumor dissemination in BALB/c mice. Plasma levels of lysophosphatidic acid (LPA) are significantly reduced in mice that received bHDL and the dual-domain peptides, suggesting that reduction by effecting accumulation and/or synthesis of pro-inflammatory lipids may be one of the mechanisms for the inhibition of tumor development by bHDL and the dual-domain peptides. Our studies suggest that therapeutics based on apolipoproteins present in HDL may be novel agents for the treatment of epithelial adenocarcinomas of the ovary and colon.

High sdLDL Cholesterol can be Used to Reclassify Individuals with Low Cardiovascular Risk for Early Intervention: Findings from the Chinese Multi-Provincial Cohort Study

Aim: A high-risk strategy has been implemented for lipid-lowering therapy in the primary prevention of cardiovascular disease. However, atherosclerosis and cardiovascular events are common among individuals with low cardiovascular risk. This study aimed to determine whether the small dense low-density lipoprotein cholesterol (sdLDLC) level can predict carotid atherosclerosis progression and identify high-risk individuals.

Methods: Baseline sdLDLC and low-density lipoprotein cholesterol (LDLC) were measured in 808 particip ants from the Chinese Multi-provincial Cohort Study, aged 45–74 years. Adjusted relative risk was calculated using a modified Poisson regression model to assess the relationship between sdLDLC and 5-year atherosclerosis progression, as indicated by the progression, incidence, and multi-territorial extent of carotid plaque.

Results: The 5-year atherosclerosis progression increased significantly with increased sdLDLC. Baseline sdLDLC was significantly associated with the short-term risk of plaque progression after multivariable adjustment, even in participants with low LDLC or a 10-year estimated cardiovascular risk. sdLDLC predicted plaque progression (relative risk 2.05; 95% confidence interval 1.43–2.93) in participants with LDLC < 130 mg/dL. Furthermore, participants with the highest sdLDLC but intermediate or low cardiovascular risk (accounting for 16% of the cohort) had double the risk of plaque progression, which was comparable to those with the same sdLDLC and high cardiovascular risk, relative to those with the lowest sdLDLC levels and low cardiovascular risk.

Conclusions: sdLDLC is independently associated with the progression of carotid atherosclerosis, which may provide a basis for clinicians to reclassify individuals believed to be at low cardiovascular risk into the high-risk category, and those with high sdLDLC may benefit from more aggressive cholesterol-lowering treatment.

Lipoprotein Subfractions and Glucose Homeostasis in Prediabetes and Diabetes in Taiwan

AIMS

Prediabetes and diabetes are associated with increased insulin resistance and decreased insulin production, dyslipidemia, and increased cardiovascular disease (CVD) risk. Our goals were to assess lipoprotein subfractions using novel assays in such subjects.

METHODS

Fasting normal, prediabetic, and diabetic Taiwanese men and women (n=2,049) had their serum glucose, glycosylated hemoglobin, insulin, total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), HDL3-C, apolipoprotein E-HDL-C, direct low-density lipoprotein cholesterol (LDL-C), small dense LDL-C (sdLDL-C), LDL-TG, and remnant lipoprotein cholesterol (RLP-C) levels measured using novel assays. HDL2-C, LDL-C, and large-buoyant LDL-C (lbLDL-C) were calculated.

RESULTS

Prediabetic male and female subjects had significantly higher levels of TG, RLP-C, sdLDL-C, the sdLDL-C/LDL-C ratio, and LDL-TG than normal subjects, and statin treatment abolished this effect in men, but not in women. Diabetic male and female subjects had significantly higher TG and sdLDL-C/LDL-C ratios, and significantly lower levels of HDL-C, HDL2-C, HDL3-C, and apoE HDL-C than normal subjects, as did prediabetic women. Median direct LDL-C levels were ＞100 mg/dL in all groups, even in those receiving statin therapy. Calculated LDL-C significantly underestimated direct LDL-C by ＞10% in diabetic subjects.

CONCLUSIONS

Our data indicate that prediabetic subjects were more likely to have significantly elevated RLP-C, sdLDL-C, and LDL-TG, while diabetic subjects were more likely to have significantly decreased HDL-C, HDL2-C, HDL3-C, and apoE HDL-C than normal subjects, and calculated LDL-C significantly underestimated their direct LDL-C. In our view, direct LDL-C and sdLDL-C should be measured and optimized in both diabetic and prediabetic subjects to reduce CVD risk.

A two-step homogeneous assay for apolipoprotein E-containing high-density lipoprotein-cholesterol

BACKGROUND

Apolipoprotein E-containing high-density lipoprotein shows antiatherogenic properties in vitro. There is a need for a homogeneous assay to determine the concentration of apolipoprotein E-containing high-density lipoprotein for in vivo studies.

METHODS

In the proposed homogeneous assay, lipoproteins other than apolipoprotein E-containing high-density lipoprotein were eliminated in the first step. Apolipoprotein E-containing high-density lipoprotein-cholesterol was measured in the second step. The control study used a 13% polyethylene glycol precipitation assay (control assay).

RESULTS

The homogeneous assay showed good performance in validation studies. In subjects with normal liver function ( n = 78), a significant correlation was found between the control assay and the homogeneous assay ( r = 0.824). Serum apolipoprotein E-containing high-density lipoprotein cholesterol concentrations, determined by the control assay and the homogeneous assay, respectively, were 0.05 (0.04-0.10) (median [25th-75th percentile]) mmol/L and 0.10 (0.06-0.13) mmol/L for healthy individuals ( n = 12), and 0.03 (0.01-0.13) mmol/L and 0.02 (0.01-0.02) mmol/L for patients with cholestasis ( n = 6). The results indicate that the homogeneous assay recovers cholesterol contained in physiological apolipoprotein E-containing high-density lipoprotein, but not in pathological apolipoprotein E-containing high-density lipoprotein from cholestatic patients.

CONCLUSIONS

The proposed two-step homogeneous assay enables selective measurement of physiological apolipoprotein E-containing high-density lipoprotein cholesterol in common autoanalysers. This assay might uncover a role for apolipoprotein E-containing high-density lipoprotein in physiological conditions.