Apolipoprotein profiling as a personalized approach to the diagnosis and treatment of dyslipidaemia

Targeting the vivid facets of apolipoproteins as a cardiovascular risk factor in rheumatoid arthritis

Mostly, cardiovascular diseases are blamed for casualties in rheumatoid arthritis (RA) patients. Customarily, dyslipidemia is probably the most prevalent underlying cause of untimely demise in people suffering from RA as it hastens the expansion of atherosclerosis. The engagement of inflammatory cytokines like tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1), interleukin-6 (IL-6), etc., is crucial in the progression and proliferation of both RA and abnormal lipid parameters. Thus, lipid abnormalities should be monitored frequently in patients with both primary and advanced RA stages. An advanced lipid profile examination, i.e., direct role of apolipoproteins associated with various lipid molecules is a more dependable approach for better understanding of the disease and selecting suitable therapeutic targets. Therefore, studying their apolipoproteins is more relevant than assessing RA patients' altered lipid profile levels. Among the various apolipoprotein classes, Apo A1 and Apo B are primarily being focused. In addition, it also addresses how calculating Apo B:Apo A1 ratio can aid in analyzing the disease's risk. The marketed therapies available to control lipid abnormalities are associated with many other risk factors. Hence, directly targeting Apo A1 and Apo B would provide a better and safer option.

Closing the gaps in patient management of dyslipidemia: stepping into cardiovascular precision diagnostics with apolipoprotein profiling

In persons with dyslipidemia, a high residual risk of cardiovascular disease remains despite lipid lowering therapy. Current cardiovascular risk prediction mainly focuses on low-density lipoprotein cholesterol (LDL-c) levels, neglecting other contributing risk factors. Moreover, the efficacy of LDL-c lowering by statins resulting in reduced cardiovascular risk is only partially effective. Secondly, from a metrological viewpoint LDL-c falls short as a reliable measurand. Both direct and calculated LDL-c tests produce inaccurate test results at the low end under aggressive lipid lowering therapy. As LDL-c tests underperform both clinically and metrologically, there is an urging need for molecularly defined biomarkers. Over the years, apolipoproteins have emerged as promising biomarkers in the context of cardiovascular disease as they are the functional workhorses in lipid metabolism. Among these, apolipoprotein B (ApoB), present on all atherogenic lipoprotein particles, has demonstrated to clinically outperform LDL-c. Other apolipoproteins, such as Apo(a) - the characteristic apolipoprotein of the emerging risk factor lipoprotein(a) -, and ApoC-III - an inhibitor of triglyceride-rich lipoprotein clearance -, have attracted attention as well. To support personalized medicine, we need to move to molecularly defined risk markers, like the apolipoproteins. Molecularly defined diagnosis and molecularly targeted therapy require molecularly measured biomarkers. This review provides a summary of the scientific validity and (patho)physiological role of nine serum apolipoproteins, Apo(a), ApoB, ApoC-I, ApoC-II, ApoC-III, ApoE and its phenotypes, ApoA-I, ApoA-II, and ApoA-IV, in lipid metabolism, their association with cardiovascular disease, and their potential as cardiovascular risk markers when measured in a multiplex apolipoprotein panel.

Developing an SI-traceable Lp(a) reference measurement system: a pilgrimage to selective and accurate apo(a) quantification

In the past decade a remarkable rebirth of serum/plasma lipoprotein(a) (Lp(a)) as an independent risk factor of cardiovascular disease (CVD) occurred. Updated evidence for a causal continuous association in different ethnic groups between Lp(a) concentrations and cardiovascular outcomes has been published in the latest European Atherosclerosis Society (EAS) Lp(a) consensus statement. Interest in measuring Lp(a) at least once in a person's lifetime moreover originates from the development of promising new Lp(a) lowering drugs. Accurate and clinically effective Lp(a) tests are of key importance for the timely detection of high-risk individuals and for future evaluation of the therapeutic effects of Lp(a) lowering medication. To this end, it is necessary to improve the performance and standardization of existing Lp(a) tests, as is also noted in the Lp(a) consensus statement. Consequently, a state-of-the-art internationally endorsed reference measurement system (RMS) must be in place that allows for performance evaluation of Lp(a) field tests in order to certify their validity and accuracy. An ELISA-based RMS from Northwest Lipid Research Laboratory (University of Washington, Seattle, USA) has been available since the 1990s. A next-generation apo(a)/Lp(a) RMS is now being developed by a working group from the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). The envisioned apo(a) RMS is based on the direct measurement of selected proteotypic fragments generated after proteolytic digestion using quantitative protein mass spectrometry (MS). The choice for an MS-based RMS enables selective measurement of the proteotypic peptides and is by design apo(a) isoform insensitive. Clearly, the equimolar conversion of apo(a) into the surrogate peptide measurands is required to obtain accurate Lp(a) results. The completeness of proteolysis under reaction conditions from the candidate reference measurement procedure (RMP) has been demonstrated for the quantifying apo(a) peptides. Currently, the candidate apo(a) RMP is endorsed by the IFCC and recommendations for suitable secondary reference materials have been made in a recent commutability study paper. Ongoing efforts toward a complete apo(a) RMS that is listed by the Joint Committee on Traceability in Laboratory Medicine (JCTLM) are focused on the peptide-based calibration and the establishment of a network of calibration laboratories running the apo(a) RMS in a harmonized way. Once completed, it will be the holy grail for evaluation and certification of Lp(a) field methods.

High residual cardiovascular risk after lipid-lowering: prime time for Predictive, Preventive, Personalized, Participatory, and Psycho-cognitive medicine

As time has come to translate trial results into individualized medical diagnosis and therapy, we analyzed how to minimize residual risk of cardiovascular disease (CVD) by reviewing papers on "residual cardiovascular disease risk". During this review process we found 989 papers that started off with residual CVD risk after initiating statin therapy, continued with papers on residual CVD risk after initiating therapy to increase high-density lipoprotein-cholesterol (HDL-C), followed by papers on residual CVD risk after initiating therapy to decrease triglyceride (TG) levels. Later on, papers dealing with elevated levels of lipoprotein remnants and lipoprotein(a) [Lp(a)] reported new risk factors of residual CVD risk. And as new risk factors are being discovered and new therapies are being tested, residual CVD risk will be reduced further. As we move from CVD risk reduction to improvement of patient management, a paradigm shift from a reductionistic approach towards a holistic approach is required. To that purpose, a personalized treatment dependent on the individual's CVD risk factors including lipid profile abnormalities should be configured, along the line of P5 medicine for each individual patient, i.e., with Predictive, Preventive, Personalized, Participatory, and Psycho-cognitive approaches.

Influence of rosuvastatin on apolipoproteins and coagulation factor levels: Results from the STAtin Reduce Thrombophilia trial

Background

The STAtins Reduce Thrombophilia trial showed that, in patients with prior venous thrombosis, rosuvastatin decreased various coagulation factor levels.

Objectives

Here, we investigated the hypothesis that statins decrease coagulation factor levels through shared mechanisms of synthesis or regulatory pathways with apolipoproteins.

Methods

We measured the levels of apolipoprotein (Apo)A-I, A-II, A-IV, (a), B-100, B-total, C-I, C-II, C-III, and E in patients (n = 126) randomized to 28 days of rosuvastatin use. We assessed the association between apolipoproteins and coagulation factors at baseline using linear regression. The mean difference in apolipoprotein levels between baseline and after 28 days of rosuvastatin use was determined through linear regression, adjusting for age, sex, and body mass index. Coagulation factors were added to this model to determine if the lowering of apolipoproteins by rosuvastatin was linked with coagulation factor levels.

Results

At baseline, levels of all apolipoproteins, except Apo(a), were positively associated with FVII, FIX, and FXI. Apolipoproteins levels, except for ApoA-I, A-IV, and Apo(a), were decreased after 28 days of rosuvastatin. ApoB-100 showed the largest mean decrease of -0.43 g/L (95% CI = -0.46 to -0.40). The decrease in ApoC-I and C-III levels was associated with a decrease in FVII, whereas the decrease in apoA-II, B-100, and B-total was associated with a decrease in FXI. The decrease in apolipoproteins was neither associated with FVIII or vWF decrease nor with endogenous thrombin potential changes.

Conclusions

Rosuvastatin decreases the level of several apolipoproteins, but this decrease was associated only with a decrease in FVII and XI and not with FVIII/vWF.

Correlation between Lpa, APO-A, APO-B, and Stenosis of Middle Cerebral Artery in Patients with Cerebral Ischemic Stroke

Ischemic stroke (CIS) is characterized by a high incidence, disability, and mortality. Numerous studies have demonstrated that intracranial arterial stenosis is an important pathological basis of CIS, and its main cause is atherosclerosis. Dyslipidemia is an important risk factor for atherosclerosis. Lysophosphatidic acid (Lpa), apolipoprotein -A(APO-A), and apolipoprotein -B(APO-B) proved to be significantly correlated with the severity of coronary artery disease. This study retrospectively collected the case data of 186 patients with CIS treated from May 2020 to May 2022 and explored the correlation between Lpa, APO-A, APO-B, and middle cerebral artery (MCA) stenosis in CIS patients.

The known unknowns of apolipoprotein glycosylation in health and disease

Apolipoproteins, the protein component of lipoproteins, play an important role in lipid transport, lipoprotein assembly, and receptor recognition. Apolipoproteins are glycosylated and the glycan moieties play an integral role in apolipoprotein function. Changes in apolipoprotein glycosylation correlate with several diseases manifesting in dyslipidemias. Despite their relevance in apolipoprotein function and diseases, the total glycan repertoire of most apolipoproteins remains undefined. This review summarizes the current knowledge and knowledge gaps regarding human apolipoprotein glycan composition, structure, glycosylation site, and functions. Given the relevance of glycosylation to apolipoprotein function, we expect that future studies of apolipoprotein glycosylation will contribute new understanding of disease processes and uncover relevant biomarkers and therapeutic targets. Considering these future efforts, we also provide a brief overview of current mass spectrometry based technologies that can be applied to define detailed glycan structures, site-specific compositions, and the role of emerging approaches for clinical applications in biomarker discovery and personalized medicine.

Role of apolipoprotein O in autophagy via the p38 mitogen-activated protein kinase signaling pathway in myocardial infarction

OBJECTIVE

To explore the role and possible mechanisms of action of apolipoprotein O (APOO) in autophagy in Myocardial Infarction (MI) in vivo and in vitro.

METHODS

Differential gene expression and single Gene Set Enrichment Analysis (GSEA) were used to evaluate MI-related candidate genes. Animal and cell MI models were established. Sh-APOO, si-APOO, and SB203580 were used to inhibit the expression of APOO or p38MAPK. Western blot and qRT-PCR were used to analyze the expression levels of the target protein or mRNA. Apoptosis was observed using the TUNEL assay. The plasma concentrations of CK-MB and cTn-I in humans and mice were determined.

RESULTS

In the GSE23294 dataset, APOO mRNA was highly expressed in the left ventricle of mice with MI; GSEA revealed that APOO was positively correlated with p38MAPK, autophagy, and apoptosis. The plasma concentration of APOO in patients with MI was significantly higher than that in healthy subjects. The expression of APOO, Beclin-1, LC3, and Bax in mouse and AC16 cell MI models increased, while the level of Bcl-2 decreased. After silencing the APOO gene, the expression of APOO was downregulated; meanwhile, changes in autophagy, apoptosis and myocardial cell injury were reversed in vivo and in vitro. Furthermore, autophagy was alleviated after AC16 cells were treated with SB203580.

CONCLUSIONS

The increased APOO expression in mouse and cell MI models may activate autophagy and apoptosis by regulating the p38MAPK signaling pathway, thus aggravating the myocardial injury.

Levels of Angiotensin-Converting Enzyme and Apolipoproteins Are Associated with Alzheimer’s Disease and Cardiovascular Diseases

Angiotensin-converting enzyme-1 (ACE1) and apolipoproteins (APOs) may play important roles in the development of Alzheimer’s disease (AD) and cardiovascular diseases (CVDs). This study aimed to examine the associations of AD, CVD, and endocrine-metabolic diseases (EMDs) with the levels of ACE1 and 9 APO proteins (ApoAI, ApoAII, ApoAIV, ApoB, ApoCI, ApoCIII, ApoD, ApoE, and ApoH). Non-Hispanic white individuals including 109 patients with AD, 356 mild cognitive impairment (MCI), 373 CVD, 198 EMD and controls were selected from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) dataset. Multivariable general linear model (GLM) was used to examine the associations. ApoE ε4 allele was associated with AD, as well as ApoAIV, ApoB and ApoE proteins, but not associated with CVD and EMD. Both AD and CVD were associated with levels of ACE1, ApoB, and ApoH proteins. AD, MCI and EMD were associated with levels of ACE1, ApoAII, and ApoE proteins. This is the first study to report associations of ACE1 and several APO proteins with AD, MCI, CVD and EMD, respectively, including upregulated and downregulated protein levels. In conclusion, as specific or shared biomarkers, the levels of ACE1 and APO proteins are implicated for AD, CVD, EMD and ApoE ε4 allele. Further studies are required for validation to establish reliable biomarkers for these health conditions.

Second-trimester maternal lipid profiles rather than glucose levels predict the occurrence of neonatal macrosomia regardless of glucose tolerance status: A matched cohort study in Beijing

AIMS

The mechanism underlying fetal overgrowth during pregnancy remains elusive. We aimed to establish a predictive model to identify the high-risk individuals with macrosomia in the second trimester of pregnancy.

DESIGN

A total of 2577 pregnant women with a routine 75-g oral glucose tolerance test during 24-28 gestational weeks were screened in a prospective cohort. Gestational diabetes mellitus (GDM) cases were 1:1 matching with age (±2 years) in normal glucose tolerance (NGT) ones from the same region. Multivariate logistic regression analysis and receiver operating characteristic (ROC) curve were performed to determine the index and its inflection point for predicting macrosomia occurrence.

RESULTS

The data of perinatal outcomes of 565 GDM and 549 NGT who had given birth to single live babies at term were analyzed. Notably, we found serum apolipoprotein B (ApoB) level higher than 4.04 g/L combined with triglycerides (TG)/high-density lipoprotein cholesterol (HDLC) ratio above 1.36 formed the predictive model in both groups. The area under the ROC curve of this predictive model included ApoB and TG/HDL-C reached 0.807 (95% CI: 0.771-0.873) with a sensitivity of 71.9% and a specificity of 78.6%. Mediation analysis revealed that ApoB and TG/HDL-C ratio mediated the harmful effect of FBG on the risk of macrosomia.

CONCLUSION

Maternal ApoB levels and TG/HDL-C ratio could predict macrosomia occurrence in pregnancy, which might be a new target for early intervention to prevent excess fetal growth.

Quantifying atherogenic lipoproteins for lipid-lowering strategies: consensus-based recommendations from EAS and EFLM

The joint consensus panel of the European Atherosclerosis Society (EAS) and the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) recently addressed present and future challenges in the laboratory diagnostics of atherogenic lipoproteins. Total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDLC), LDL cholesterol (LDLC), and calculated non-HDLC (=total - HDLC) constitute the primary lipid panel for estimating risk of atherosclerotic cardiovascular disease (ASCVD) and can be measured in the nonfasting state. LDLC is the primary target of lipid-lowering therapies. For on-treatment follow-up, LDLC shall be measured or calculated by the same method to attenuate errors in treatment decisions due to marked between-method variations. Lipoprotein(a) [Lp(a)]-cholesterol is part of measured or calculated LDLC and should be estimated at least once in all patients at risk of ASCVD, especially in those whose LDLC declines poorly upon statin treatment. Residual risk of ASCVD even under optimal LDL-lowering treatment should be also assessed by non-HDLC or apolipoprotein B (apoB), especially in patients with mild-to-moderate hypertriglyceridemia (2-10 mmol/L). Non-HDLC includes the assessment of remnant lipoprotein cholesterol and shall be reported in all standard lipid panels. Additional apoB measurement can detect elevated LDL particle (LDLP) numbers often unidentified on the basis of LDLC alone. Reference intervals of lipids, lipoproteins, and apolipoproteins are reported for European men and women aged 20-100 years. However, laboratories shall flag abnormal lipid values with reference to therapeutic decision thresholds.

Association of Early Renal Dysfunction with Lipid Profile Parameters among Hypertensives in Kazakhstan

Dyslipidemia plays an essential role in chronic kidney disease (CKD). The role of lipids and lipoproteins in the early pre-disease state of CKD in hypertensive patients is still unclear. The study aimed to evaluate the relationship between early renal dysfunction and lipid profile parameters among hypertensive patients in Kazakhstan. From April 2015 to December 2016, 800 Kazakh males and females with primary hypertension who met the inclusion criteria were included in this cross-sectional study. Data were collected on socio-demographics, lifestyle parameters, family history of cardiovascular disease, and hypertension. Additionally, Dietary Quality Score (DQS), anthropometric data, and blood pressure were recorded. Laboratory blood measurements included eGFR (estimated glomerular filtration rate), lipid profile parameters such as Apolipoprotein B, A1, HDL-C, LDL-C, and TG. We found a linear relationship between early renal dysfunction and LDL-C, Apolipoprotein B, and Apolipoprotein B/A1 ratio, which was in all cases negative and small (r = -0.27, -0.23 and -0.16, respectively). Apolipoprotein A1, HDL-C and TG have not revealed a linear relationship with GFR (r = -0.06, r = -0.06, and ρ = -0.045, respectively). The multicollinearity test restricted the linear model to Apolipoprotein B only. Further linear regression analysis confirmed an inverse significant linear association between eGFR and Apolipoprotein B. Age, DQS, and income appear to be positive confounding factors, significantly fitted the final model. ROC analysis had proven the predictive power of Apolipoprotein B in pre-CKD eGFR decline before and after adjustment for age, DQS and income (AUC = 0.62 and AUC = 0.77, respectively). For differentiating non-diabetic subjects with and without pre-CKD eGFR decrease, 1.05 g/L and 0.98 g/L are likely to be optimal cutoff points in males and females, respectively. These findings will help early prediction of renal dysfunction and contribute to a more accurate estimation of CVD risk.

Apolipoprotein E and Atherosclerosis

PURPOSE OF REVIEW

The functions, genetic variations and impact of apolipoprotein E on lipoprotein metabolism in general are placed in the context of clinical practice dealing with moderate dyslipidaemia as well as dysbetalipoproteinemia, a highly atherogenic disorder and lipoprotein glomerulopathy.

RECENT FINDINGS

Additional variants of apolipoprotein E and participation of apolipoprotein E in inflammation are of interest. The mostly favourable effects of apolipoprotein E2 as well as the atherogenic nature of apolipoproteinE4, which has an association with cognitive impairment, are confirmed. The contribution of remnant lipoproteins of triglyceride-rich lipoproteins, of which dysbetalipoproteinemia represents an extreme, is explored in atherosclerosis. Mimetic peptides may present new therapeutic approaches. Apolipoprotein E is an important determinant of the lipid profile and cardiovascular health in the population at large and can precipitate dysbetalipoproteinemia and glomerulopathy. Awareness of apolipoprotein E polymorphisms should improve medical care.

The Time Has Come for Quantitative Protein Mass Spectrometry Tests That Target Unmet Clinical Needs

Protein mass spectrometry (MS) is an enabling technology that is ideally suited for precision diagnostics. In contrast to immunoassays with indirect readouts, MS quantifications are multiplexed and include identification of proteoforms in a direct manner. Although widely used for routine measurements of drugs and metabolites, the number of clinical MS-based protein applications is limited. In this paper, we share our experience and aim to take away the concerns that have kept laboratory medicine from implementing quantitative protein MS. To ensure added value of new medical tests and guarantee accurate test results, five key elements of test evaluation have been established by a working group within the European Federation for Clinical Chemistry and Laboratory Medicine. Moreover, it is emphasized to identify clinical gaps in the contemporary clinical pathways before test development is started. We demonstrate that quantitative protein MS tests that provide an additional layer of clinical information have robust performance and meet long-term desirable analytical performance specifications as exemplified by our own experience. Yet, the adoption of quantitative protein MS tests into medical laboratories is seriously hampered due to its complexity, lack of robotization and high initial investment costs. Successful and widespread implementation in medical laboratories requires uptake and automation of this next generation protein technology by the In-Vitro Diagnostics industry. Also, training curricula of lab workers and lab specialists should include education on enabling technologies for transitioning to precision medicine by quantitative protein MS tests.

Towards an SI-Traceable Reference Measurement System for Seven Serum Apolipoproteins Using Bottom-Up Quantitative Proteomics: Conceptual Approach Enabled by Cross-Disciplinary/Cross-Sector Collaboration

Current dyslipidemia management in patients with atherosclerotic cardiovascular disease (ASCVD) is based on traditional serum lipids. Yet, there is some indication from basic research that serum apolipoproteins A-I, (a), B, C-I, C-II, C-III, and E may give better pathophysiological insight into the root causes of dyslipidemia. To facilitate the future adoption of clinical serum apolipoprotein (apo) profiling for precision medicine, strategies for accurate testing should be developed in advance. Recent discoveries in basic science and translational medicine set the stage for the IFCC Working Group on Apolipoproteins by Mass Spectrometry. Main drivers were the convergence of unmet clinical needs in cardiovascular disease (CVD) patients with enabling technology and metrology. First, the residual cardiovascular risk after accounting for established risk factors demonstrates that the current lipid panel is too limited to capture the full complexity of lipid metabolism in patients. Second, there is a need for accurate test results in highly polymorphic and atherogenic apolipoproteins such as apo(a). Third, sufficient robustness of mass spectrometry technology allows reproducible protein quantification at the molecular level. Fourth, several calibration hierarchies in the revised ISO 17511:2020 guideline facilitate metrological traceability of test results, the highest achievable standard being traceability to SI. This article outlines the conceptual approach aimed at achieving a novel, multiplexed Reference Measurement System (RMS) for seven apolipoproteins based on isotope dilution mass spectrometry and peptide-based calibration. This RMS should enable standardization of existing and emerging apolipoprotein assays to SI, within allowable limits of measurement uncertainty, through a sustainable network of Reference Laboratories.

Omega-3 polyunsaturated fatty acids: anti-inflammatory and anti-hypertriglyceridemia mechanisms in cardiovascular disease

Cardiovascular disease (CVD) is the world's most recognized and notorious cause of death. It is known that increased triglyceride-rich lipoproteins (TRLs) and remnants of triglyceride-rich lipoproteins (RLP) are the major risk factor for CVD. Furthermore, hypertriglyceridemia commonly leads to a reduction in HDL and an increase in atherogenic small dense low-density lipoprotein (sdLDL or LDL-III) levels. Thus, the evidence shows that Ω-3 fatty acids (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have a beneficial effect on CVD through reprogramming of TRL metabolism, reducing inflammatory mediators (cytokines and leukotrienes), and modulation of cell adhesion molecules. Therefore, the purpose of this review is to provide the molecular mechanism related to the beneficial effect of Ω-3 PUFA on the lowering of plasma TAG levels and other atherogenic lipoproteins. Taking this into account, this study also provides the TRL lowering and anti-inflammatory mechanism of Ω-3 PUFA metabolites such as RvE1 and RvD2 as a cardioprotective function.

Apolipoprotein B/A1 Ratio as a Diagnostic Alternative to Triglycerides and HDL-Cholesterol for the Prediction of Metabolic Syndrome among Hypertensives in Kazakhstan

Apolipoproteins (Apo) are known atherogenic factors that play important roles in many mechanisms related to coronary heart disease. The ApoB/ApoA1 ratio is a promising diagnostic tool for metabolic syndrome (MS) in different populations, though its use is not established in Kazakhstan. This study aimed to assess the relationship between MS and the ApoB/ApoA1 ratio among hypertensive patients and to evaluate its diagnostic use for identifying MS as an alternative to triglycerides (TG) and high-density lipoprotein cholesterol (HDL-C). A cross-sectional study was conducted in 800 eligible men and women with primary hypertension from April 2015 to December 2016. Data were collected on socio-demographics, lifestyle parameters, family history of cardiovascular disease, and hypertension. Dietary Quality Score (DQS), anthropometric data, and blood pressure were recorded; ApoA1 and ApoB levels were measured in blood samples. We found a significant positive association between MS and the ApoB/ApoA1 ratio by multiple logistic regression, as shown by a linear trend of increase of the odds ratio (OR) for MS across the quartiles of ApoB/ApoA1 (p < 0.0001). ROC analysis revealed diagnostic significance of the ApoB/ApoA1 ratio for MS, and comparative ROC analysis demonstrated equal diagnostic value of ApoB/ApoA1 ratio and TG levels (AUC = 0.71 (95% CI 0.69; 0.74) and 0.72 (95% CI 0.69, 0.76), respectively), which was significantly higher than those of HDL, ApoA1, ApoB (AUC = 0.27 (95% CI 0.23; 0.31), AUC = 0.37 (95% CI 0.33; 0.41), AUC = 0.67, (95% CI 0.63; 0.71), respectively). The diagnostic value of the ApoB/ApoA1 ratio in Kazakhs with MS appeared to equal that of TG and was significantly higher than that of HDL-C. Adjusting for gender, smoking, and DQS significantly strengthened the association between MS and the ApoB/ApoA1 ratio in the Kazakh population.

Non-HDL Cholesterol or apoB: Which to Prefer as a Target for the Prevention of Atherosclerotic Cardiovascular Disease?

PURPOSE OF REVIEW

Guidelines propose using non-HDL cholesterol or apolipoprotein (apo) B as a secondary treatment target to reduce residual cardiovascular risk of LDL-targeted therapies. This review summarizes the strengths, weaknesses, opportunities, and threats (SWOT) of using apoB compared with non-HDL cholesterol.

RECENT FINDINGS

Non-HDL cholesterol, calculated as total-HDL cholesterol, includes the assessment of remnant lipoprotein cholesterol, an additional risk factor independent of LDL cholesterol. ApoB is a direct measure of circulating numbers of atherogenic lipoproteins, and its measurement can be standardized across laboratories worldwide. Discordance analysis of non-HDL cholesterol versus apoB demonstrates that apoB is the more accurate marker of cardiovascular risk. Baseline and on-treatment apoB can identify elevated numbers of small cholesterol-depleted LDL particles that are not reflected by LDL and non-HDL cholesterol. ApoB is superior to non-HDL cholesterol as a secondary target in patients with mild-to-moderate hypertriglyceridemia (175-880 mg/dL), diabetes, obesity or metabolic syndrome, or very low LDL cholesterol < 70 mg/dL. When apoB is not available, non-HDL cholesterol should be used to supplement LDLC.

A high-throughput mass spectrometry-based assay for large-scale profiling of circulating human apolipoproteins

Apolipoproteins govern lipoprotein metabolism and are promising biomarkers of metabolic and cardiovascular diseases. Unlike immunoassays, MS enables the quantification and phenotyping of multiple apolipoproteins. Hence, here, we aimed to develop a LC-MS/MS assay that can simultaneously quantitate 18 human apolipoproteins [A-I, A-II, A-IV, A-V, B48, B100, C-I, C-II, C-III, C-IV, D, E, F, H, J, L1, M, and (a)] and determined apoE, apoL1, and apo(a) phenotypes in human plasma and serum samples. The plasma and serum apolipoproteins were trypsin digested through an optimized procedure and peptides were extracted and analyzed by LC-MS/MS. The method was validated according to standard guidelines in samples spiked with known peptide amounts. The LC-MS/MS results were compared with those obtained with other techniques, and reproducibility, dilution effects, and stabilities were also assessed. Peptide markers were successfully selected for targeted apolipoprotein quantification and phenotyping. After optimization, the assay was validated for linearity, lower limits of quantification, accuracy (biases: -14.8% to 12.1%), intra-assay variability [coefficients of variation (CVs): 1.5-14.2%], and inter-assay repeatability (CVs: 4.1-14.3%). Bland-Altman plots indicated no major statistically significant differences between LC-MS/MS and other techniques. The LC-MS/MS results were reproducible over five repeated experiments (CVs: 1.8-13.7%), and we identified marked differences among the plasma and serum samples. The LC-MS/MS assay developed here is rapid, requires only small sampling volumes, and incurs reasonable costs, thus making it amenable for a wide range of studies of apolipoprotein metabolism. We also highlight how this assay can be implemented in laboratories.

After another decade: LC-MS/MS became routine in clinical diagnostics

Tandem mass spectrometry - especially in combination with liquid chromatography (LC-MS/MS) - is applied in a multitude of important diagnostic niches of laboratory medicine. It is unquestioned in its routine use and is often unreplaceable by alternative technologies. This overview illustrates the development in the past decade (2009-2019) and intends to provide insight into the current standing and future directions of the field. The instrumentation matured significantly, the applications are well understood, and the in vitro diagnostics (IVD) industry is shaping the market by providing assay kits, certified instruments, and the first laboratory automated LC-MS/MS instruments as an analytical core. In many settings the application of LC-MS/MS is still burdensome with locally lab developed test (LDT) designs relying on highly specialized staff. The current routine applications cover a wide range of analytes in therapeutic drug monitoring, endocrinology including newborn screening, and toxicology. The tasks that remain to be mastered are, for example, the quantification of proteins by means of LC-MS/MS and the transition from targeted to untargeted omics approaches relying on pattern recognition/pattern discrimination as a key technology for the establishment of diagnostic decisions.

Human apolipoprotein CIII levels; evaluation of three assay methods

Apolipoprotein CIII (apoCIII) is associated with triglyceride (TG)-rich particles like VLDL and exerts an inhibitory effect of lipoprotein lipase. Increased levels are related to cardiovascular diseases and diabetes and therefore apoCIII has been proposed as a useful biomarker. Even if several commercial assays for measuring apoCIII in human plasma/serum are available, data is scarce concerning their reliability and none is used clinically. In the present study a comparative investigation has been done. Two ELISA-based methods (Cusabio Biotech and Assay Pro) and one nephelometric assay (Siemens Healthcare) were investigated. Serum and plasma samples were obtained from healthy volunteers and from samples sent to the Laboratory of Clinical Chemistry, preferably with higher levels of TGs. The Cusabio Biotech assay did not yield any valid results. However, both the methods from Assay Pro and Siemens Healthcare showed good performance with similar dynamic ranges. The latter assay had lower CV and required less work. In healthy individuals, apoCIII levels were not affected by fasting, freezing or thawing, nor did we find any gender differences. Individuals with elevated levels of TG displayed higher apoCIII values. Females with oral intake of contraceptives had higher levels. In conclusion, the nephelometric assay showed the best performance with the lowest CV, was less labor intensive than an assay based on ELISA and could therefore be suitable for clinical use.