Diagnosis and treatment of apolipoprotein B dyslipoproteinemias

Apolipoprotein B: Bridging the Gap Between Evidence and Clinical Practice

Despite data suggesting that apolipoprotein B (apoB) measurement outperforms low-density lipoprotein cholesterol level measurement in predicting atherosclerotic cardiovascular disease risk, apoB measurement has not become widely adopted into routine clinical practice. One barrier for use of apoB measurement is lack of consistent guidance for clinicians on how to interpret and apply apoB results in clinical context. Whereas guidelines have often provided clear low-density lipoprotein cholesterol targets or triggers to initiate treatment change, consistent targets for apoB are lacking. In this review, we synthesize existing data regarding the epidemiology of apoB by comparing guideline recommendations regarding use of apoB measurement, describing population percentiles of apoB relative to low-density lipoprotein cholesterol levels, summarizing studies of discordance between low-density lipoprotein cholesterol and apoB levels, and evaluating apoB levels in clinical trials of lipid-lowering therapy to guide potential treatment targets. We propose evidence-guided apoB thresholds for use in cholesterol management and clinical care.

Low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol and apolipoprotein B for cardiovascular care

PURPOSE OF REVIEW

Some experts and consensus groups continue to argue that apolipoprotein B (apoB) should not be introduced broadly into clinical care. But, too often, the present approach to clinical care is not succeeding. An important reason for this failure, we believe, is that the conventional approach limits what the expert clinician can accomplish and is too complex, confusing, and contradictory for primary care physicians to apply effectively in their practise.

RECENT FINDINGS

There are four major reasons that apoB should be measured routinely in clinical care. First, apoB is a more accurate marker of cardiovascular risk than LDL-C or non-HDL-C. Second, the measurement of apoB is standardized whereas the measurements of LDL-C and non-HDL-C are not. Third, with apoB and a conventional lipid panel, all the lipid phenotypes can be simply and accurately distinguished. This will improve the care of the expert. Fourth, apoB, as the single measure to evaluate the success of therapy, would simplify the process of care for primary care physicians.

SUMMARY

By introducing apoB broadly into clinical care, the process of care will be improved for both the expert and the primary care physician, and this will improve the outcomes of care.

Applicability of Diagnostic Criteria and High Prevalence of Familial Dysbetalipoproteinemia in Russia: A Pilot Study

Familial dysbetalipoproteinemia (FD) is a highly atherogenic genetically based lipid disorder with an underestimated actual prevalence. In recent years, several biochemical algorithms have been developed to diagnose FD using available laboratory tests. The practical applicability of FD diagnostic criteria and the prevalence of FD in Russia have not been previously assessed. We demonstrated that the diagnostic algorithms of FD, including the diagnostic apoB levels, require correction, taking into account the distribution of apoB levels in the population. At the same time, a triglycerides cutoff ≥ 1.5 mmol/L may be a useful tool in identifying subjects with FD. In this study, a high prevalence of FD was detected: 0.67% (one in 150) based on the ε2ε2 haplotype and triglycerides levels ≥ 1.5 mmol/L. We also analyzed the presence and pathogenicity of APOE variants associated with autosomal dominant FD in a large research sample.

Hypertriglyceridemic hyperapoB and the development and resolution of nonalcoholic fatty liver disease: a cohort study

Hypertriglyceridemic hyperapoB is an adverse lipoprotein phenotype characterized by low high density lipoprotein (HDL) cholesterol, high triglycerides, high apolipoprotein B (ApoB), and low low density lipoprotein (LDL) cholesterol to ApoB ratio. We investigated whether and to what extent hypertriglyceridemic hyperapoB associates with the incidence and resolution of nonalcoholic fatty liver disease (NAFLD). This prospective cohort study included 9,019 Chinese participants 40 years or older, from 2010 to 2015. Logistic regression models were used to examine the odds ratios (ORs) for the incidence and resolution of NAFLD associated with the hypertriglyceridemic hyperapoB lipoprotein phenotype and individual lipid and lipoprotein parameters. During a median 4.3 years of follow-up, compared with participants with optimal phenotype, the fully adjusted ORs (95% CIs) for participants with hypertriglyceridemic hyperapoB were 2.75 (1.91, 3.95) and 0.57 (0.33, 1.00) for incidence and resolution of NAFLD, respectively. These associations were consistent across subgroup participants with varied demographic, lifestyle, and metabolic status. Individually, each unit increase in HDL cholesterol (OR: 0.98; 95% CI: 0.97, 0.99), natural logarithm-transformed triglycerides (1.89; 1.52, 2.36), and ApoB (1.006; 1.002, 1.011) was independently associated with NAFLD incidence, and only triglycerides (0.77; 0.60, 0.99) was independently associated with NAFLD resolution. Our findings suggest that Chinese adults with hypertriglyceridemic hyperapoB have a higher risk of NAFLD incidence and a lower likelihood of NAFLD resolution. These associations were stable among adults with different demographic, lifestyle, and metabolic status, supporting hypertriglyceridemic hyperapoB as a valuable clinical marker for the prevention and control of NAFLD.

Risk Factors of Non-alcoholic Fatty Liver Disease in the Iranian Adult Population: A Systematic Review and Meta-analysis

Context: Non-alcoholic fatty liver disease (NAFLD) is progressing considerably worldwide. Identifying the risk factors of NAFLD is a critical step in preventing its progression. Methods: In November 2022, two independent researchers studied seven databases, including PubMed, ISI/WoS, ProQuest, Scopus, SID, Magiran, and Google Scholar, and reference list of relevant articles, searching studies that assessed NAFLD risk factors in the Iranian adult population. Heterogeneity between studies was assessed by Cochran’s test and its composition using I2 statistics. A random-effects model was used when heterogeneity was observed; otherwise, a fixed-effects model was applied. Egger’s regression test and Trim-and-Fill analysis were used to assess publication bias. Comprehensive Meta-analysis software (version 3) was used for the analyses of the present study. Results: The results of this study showed significant associations between NAFLD with age [n = 15, odds ratio (OR) = 2.12, 95% CI: 1.79 - 2.51], body mass index (n = 46, OR = 5.00, 95% CI: 3.34 - 7.49), waist circumference (n = 20, OR = 6.37, 95% CI: 3.25 - 12.48), waist-to-hip ratio (n = 17, OR = 4.72, 95% CI: 3.93 - 5.66), total cholesterol (n = 39, OR = 1.80, 95% CI: 1.52 - 2.13), high-density lipoprotein (n = 37, OR = 0.53, 95% CI: 0.44 - 0.65), low-density lipoprotein (n = 31, OR = 1.68, 95% CI: 1.38 - 2.05), triglyceride (n = 31, OR = 3.21, 95% CI: 2.67 - 3.87), alanine aminotransferase (n = 26, OR = 4.06, 95% CI: 2.94 - 5.62), aspartate aminotransferase (n = 27, OR = 2.16, 95% CI: 1.50 - 3.12), hypertension (n = 13, OR = 2.53, 95% CI: 2.32 - 2.77), systolic blood pressure (n = 13, OR = 1.83, 95% CI: 1.53 - 2.18), diastolic blood pressure (n = 14, OR = 1.80, 95% CI: 1.48 - 2.20), fasting blood sugar (n = 31,OR = 2.91, 95% CI: 2.11- 4.01), homeostatic model assessment for insulin resistance (n = 5, OR = 1.92, 95% CI: 1.48 - 2.59), diabetes mellitus (n = 15, OR = 3.04, 95% CI: 2.46 - 3.75), metabolic syndrome (n = 10, OR = 3.56, 95% CI: 2.79 - 4.55), and physical activity (n = 11, OR = 0.32, 95% CI: 0.24 - 0.43) (P < 0.05). Conclusions: In conclusion, several factors are significantly associated with NAFLD. However, anthropometric indices had the strongest relationship with NAFLD in the Iranian adult population.

Role of lipoprotein lipase activity measurement in the diagnosis of familial chylomicronemia syndrome

BACKGROUND

Activity assays for lipoprotein lipase (LPL) are not standardised for use in clinical settings.

OBJECTIVE

This study sought to define and validate a cut-off points based on a ROC curve for the diagnosis of patients with familial chylomicronemia syndrome (FCS). We also evaluated the role of LPL activity in a comprehensive FCS diagnostic workflow.

METHODS

A derivation cohort (including an FCS group (n = 9), a multifactorial chylomicronemia syndrome (MCS) group (n = 11)), and an external validation cohort (including an FCS group (n = 5), a MCS group (n = 23) and a normo-triglyceridemic (NTG) group (n = 14)), were studied. FCS patients were previously diagnosed by the presence of biallelic pathogenic genetic variants in the LPL and GPIHBP1 genes. LPL activity was also measured. Clinical and anthropometric data were recorded, and serum lipids and lipoproteins were measured. Sensitivity, specificity and cut-offs for LPL activity were obtained from a ROC curve and externally validated.

RESULTS

All post-heparin plasma LPL activity in the FCS patients were below 25.1 mU/mL, that was cut-off with best performance. There was no overlap in the LPL activity distributions between the FCS and MCS groups, conversely to the FCS and NTG groups.

CONCLUSION

We conclude that, in addition to genetic testing, LPL activity in subjects with severe hypertriglyceridemia is a reliable criterium in the diagnosis of FCS when using a cut-off of 25.1 mU/mL (25% of the mean LPL activity in the validation MCS group). We do not recommend the NTG patient based cut-off values due to low sensitivity.

Management of Patients with Type V Hyperlipoproteinemia: An Uncommon Phenotype of Dyslipidemia with Chylomicronemia and Severe Hypertriglyceridemia

Hypertriglyceridemia (HTG) remains a risk-enhancing factor of atherosclerotic cardiovascular disease. We aimed to report real-world data on the management of patients with type V hyperlipoproteinemia (HLP5), an uncommon phenotype of dyslipidemia characterized by fasting chylomicronemia and severe HTG. Between July 2018 and May 2021, 90 patients with HTG, including 83 patients with type IV hyperlipoproteinemia (HLP4) and 7 patients with HLP5, were identified by plasma apolipoprotein B (apoB) and lipoprotein electrophoresis. Patients with HLP5 were younger, had higher total cholesterol (TC) (264.9 ± 26.7 mg/dL vs. 183.9 ± 26.1 mg/dL; p < 0.01) and higher triglyceride (TG) (1296.7 ± 380.5 mg/dL vs. 247.6 ± 96.1 mg/dL; p < 0.01), and had lower high-density lipoprotein cholesterol (HDL-C) (30.6 ± 4.8 mg/dL vs. 40.5 ± 8.7 mg/dL; p < 0.01) and lower low-density lipoprotein cholesterol (LDL-C) (62.9 ± 16.4 vs. 103.0 ± 21.1 mg/dL; p < 0.01) compared with patients with HLP4. Despite an aggressive use of statin and fenofibrate with greater reductions in TG (-65.9 ± 13.7% vs. -27.9 ± 30.5%; p < 0.01) following 6 months of treatment, patients with HLP5 had persistent HTG (440.1 ± 239.0 mg/dL vs. 173.9 ± 94.8 mg/dL; p < 0.01) and an increase in LDL-C (28.3 ± 57.2% vs. -19.5 ± 32.0%; p < 0.01) compared with patients with HLP4. Our findings highlight that the lack of novel TG-lowering medications and management guidelines remains an unmet medical need in patients with HLP5. Closely monitoring lipid profiles, full assessment of individual’s risk of cardiovascular disease, and emphasis on medication adherence are of clinical importance.

Physiological Bases for the Superiority of Apolipoprotein B Over Low-Density Lipoprotein Cholesterol and Non-High-Density Lipoprotein Cholesterol as a Marker of Cardiovascular Risk

In 2019, the European Society of Cardiology/European Atherosclerosis Society stated that apolipoprotein B (apoB) was a more accurate marker of cardiovascular risk than low-density lipoprotein cholesterol (LDL-C) and non-high-density lipoprotein cholesterol. Since then, the evidence has continued to mount in favor of apoB. This review explicates the physiological mechanisms responsible for the superiority of apoB as a marker of the cardiovascular risk attributable to the atherogenic apoB lipoprotein particles chylomicron remnants, very low-density lipoprotein, and low-density lipoprotein particles. First, the nature and relative numbers of these different apoB particles will be outlined. This will make clear why low-density lipoprotein particles are almost always the major determinants of cardiovascular risk and why the concentrations of triglycerides and LDL-C may obscure this relation. Next, the mechanisms that govern the number of very low-density lipoprotein and low-density lipoprotein particles will be outlined because, except for dysbetalipoproteinemia, the total number of apoB particles determines cardiovascular risk, Then, the mechanisms that govern the cholesterol mass within very low-density lipoprotein and low-density lipoprotein particles will be reviewed because these are responsible for the discordance between the mass of cholesterol within apoB particles, measured either as LDL-C or non-high-density lipoprotein cholesterol, and the number of apoB particles measured as apoB, which creates the superior predictive power of apoB over LDL-C and non-high-density lipoprotein cholesterol. Finally, the major apoB dyslipoproteinemias will be briefly outlined. Our objective is to provide a physiological framework for health care givers to understand why apoB is a more accurate marker of cardiovascular risk than LDL-C or non-high-density lipoprotein cholesterol.

Apolipoprotein B Displays Superior Predictive Value Than Other Lipids for Long-Term Prognosis in Coronary Atherosclerosis Patients and Particular Subpopulations: A Retrospective Study

PURPOSE

Accumulating evidence that apolipoprotein B (apoB) plays a critical role in predicting coronary heart disease (CHD) and future outcomes. The 2019 European Society of Cardiology/European Atherosclerosis Society guidelines suggest that apoB can be an alternative to non-HDL-C or LDL-C in patients with high triglyceride levels, diabetes, obesity, metabolic syndrome, or very low LDL-C levels. This study explores whether apoB can also serve as predictive value for long-term major adverse cardiovascular events (MACEs) in normal people and specific coronary atherosclerosis patients.

METHODS

A total of 826 patients were followed up over 10 years, and the risk factors for MACEs were retrospectively analyzed in patients with CHD and particular subpopulations. All statistical analyses were performed in R software. Cox regressions were performed to assess independent risk factors of long-term MACEs in the atherosclerosis group and CHD subgroups. Kaplan-Meier survival curves were used to evaluate the survival rate for patients in different apoB quartiles, and receiver-operating characteristic curves were used to compare apoB and other lipids in predicting the presence of long-term MACE.

FINDINGS

apoB could be a "risk-enhancing factor" in patients with coronary atherosclerosis disease, whereas in the Normal population, LDL-C still acted as a major risk factor for predicting MACEs. apoB was a good risk predictor for long-term cardiovascular events in coronary atherosclerosis (AS) patients, including the AS group and CHD subpopulations (including CHD + triglyceride ≥2.3 mmol/L, CHD + diabetes mellitus, CHD + body mass index ≥25 kg/m², or CHD + metabolic syndrome). In patients with CHD whose condition was complicated with diabetes, obesity, and metabolic syndrome, apoB performed better than other lipids in predicting the presence of myocardial infarction, hospitalization due to angina, and cardiac death. Despite achieving optimal LDL-C or non-HDL-C levels, patients with CHD are still at risk of worse survival if they are unable to reach a low apoB level (lower cut points such as 65 mg/dL).

IMPLICATIONS

More attention should be paid to special populations with residual elevations of atherogenic particle numbers, and greater focus should be placed on lowering baseline apoB to achieve long-term benefits. However, given that this was an observational study, the association of baseline apoB level and long-term MACEs only was evaluated; it is unclear whether the emergence of MACEs would be influenced by the dynamic changes of apoB. Because this was a retrospective and observational analysis, bias in data analysis was unavoidable; thus, the results cannot be used to generalize implications to broader patient populations, and more large-scale clinical trials are required to verify these findings. (Clin Ther. 2022;44:XXX-XXX) © 2022 Elsevier HS Journals, Inc.

An adverse lipoprotein phenotype-hypertriglyceridaemic hyperapolipoprotein B-and the long-term risk of type 2 diabetes: a prospective, longitudinal, observational cohort study

BACKGROUND

This study examines the risk of new-onset diabetes in patients with hypertriglyceridaemic hyperapolipoprotein B (high triglycerides, high apolipoprotein B [apoB], low LDL cholesterol to apoB ratio, and low HDL cholesterol). The aim was to establish whether this lipoprotein phenotype identified a substantial group at high risk of developing diabetes over the next 20 years.

METHODS

In this prospective, longitudinal, observational cohort study, we used data from the Framingham Offspring cohort (recruited in Framingham, MA, USA). Participants were aged 40-69 years and free of diabetes and cardiovascular disease at a baseline examination done between April, 1987, and November, 1991, and were followed up until March, 2014. Cox proportional hazards regression with hierarchical adjustment for age and sex, waist circumference, and fasting blood glucose were used to model the relationship between each lipid marker and incident diabetes, as well as the relationship between hypertriglyceridaemic hyperapoB (defined as values greater than sample medians of triglycerides and apoB, and less than medians of HDL cholesterol and LDL cholesterol to apoB ratio) and incident diabetes.

FINDINGS

Of 3446 individuals aged 40-69 years who completed baseline examination, 2515 participants were eligible and included in all analyses. During median 21·1 years (IQR 11·1-23·1) of follow-up, 402 (16·0%) individuals developed diabetes. Age (p=0·032), waist circumference (p<0·0001), fasting blood glucose (p<0·0001), and natural logarithm-transformed triglycerides (p<0·0001) were associated with new-onset diabetes, as were apoB (p=0·0016), LDL cholesterol to apoB ratio (p=0·0018), and HDL cholesterol (p=0·0016) when added to this model. The age and sex-adjusted incidence of diabetes in the hypertriglyceridaemic hyperapoB group was 32·4% (95% CI 27·8-37·7) versus 5·5% (3·5-8·6) in the optimal lipid phenotype group and 15·5% (13·5-17·7) in the mixed lipid phenotype group. The fully adjusted hazard ratio, including glucose and waist circumference, for individuals with hypertriglyceridaemic hyperapoB was 3·30 (95% CI 2·06-5·30; p=0·0008) and for mixed lipid phenotype was 2·17 (1·38-3·40; p<0·0001) compared with those with the optimal lipid phenotype.

INTERPRETATION

Our findings suggest that individuals with hypertriglyceridaemic hyperapoB are at high risk of new-onset diabetes and might benefit from intensive measures to prevent diabetes. The association between this phenotype and incident diabetes is consistent with a pro-diabetic effect due to increased clearance of apoB particles from plasma, which could injure pancreatic islet cells. This mechanism might explain the increased risk of diabetes with statin therapy.

FUNDING

Doggone Foundation.

Apolipoproteins in vascular biology and atherosclerotic disease

Apolipoproteins are important structural components of plasma lipoproteins that influence vascular biology and atherosclerotic disease pathophysiology by regulating lipoprotein metabolism. Clinically important apolipoproteins related to lipid metabolism and atherogenesis include apolipoprotein B-100, apolipoprotein B-48, apolipoprotein A-I, apolipoprotein C-II, apolipoprotein C-III, apolipoprotein E and apolipoprotein(a). Apolipoprotein B-100 is the major structural component of VLDL, IDL, LDL and lipoprotein(a). Apolipoprotein B-48 is a truncated isoform of apolipoprotein B-100 that forms the backbone of chylomicrons. Apolipoprotein A-I provides the scaffolding for lipidation of HDL and has an important role in reverse cholesterol transport. Apolipoproteins C-II, apolipoprotein C-III and apolipoprotein E are involved in triglyceride-rich lipoprotein metabolism. Apolipoprotein(a) covalently binds to apolipoprotein B-100 to form lipoprotein(a). In this Review, we discuss the mechanisms by which these apolipoproteins regulate lipoprotein metabolism and thereby influence vascular biology and atherosclerotic disease. Advances in the understanding of apolipoprotein biology and their translation into therapeutic agents to reduce the risk of cardiovascular disease are also highlighted.

Biochemical risk factors of atherosclerotic cardiovascular disease: from a narrow and controversial approach to an integral approach and precision medicine

INTRODUCTION

Guidelines of management of dyslipidemias and prevention of cardiovascular disease (CVD) are based on firm scientific evidence obtained by randomized controlled trials (RCTs). However, the role of elevated low-density lipoprotein-cholesterol (LDL-C)as a risk factor of CVD and therapies to lower LDL-C are frequently disputed by colleagues who disagree with the conclusions of the RCTs published. This review focuses on this dispute, and evaluates the current approach of management of dyslipidemias and CVD prevention to find modern alternatives for more precise diagnosis and therapy of dyslipidemic patients.

AREAS COVERED

Recent interest in lipoprotein(a) (Lp(a)) and remnants lipoproteins and in therapies that do not influence LDL-C levels primarily, such as anti-inflammatory drugs and icosapent ethyl, has revitalized our concern to optimize the care for patients with increased CVD risk without focusing simply on reduction of LDL-C by therapy with statins, ezitemibe, and proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors.

EXPERT OPINION

The limited characterization of study populations by measurement of total cholesterol (TC), high-density lipoprotein-cholesterol (HDL-C) and triglycerides (TG) followed by measurement or calculation of LDL-C should be extended by a more integral approach in order to realize precision diagnostics and precision medicine, for the sake of personalized patient care.

Sex-specific associations of adiposity with cardiometabolic traits in the UK: A multi-life stage cohort study with repeat metabolomics

BACKGROUND

Sex differences in cardiometabolic disease risk are commonly observed across the life course but are poorly understood and may be due to different associations of adiposity with cardiometabolic risk in females and males. We examined whether adiposity is differently associated with cardiometabolic trait levels in females and males at 3 different life stages.

METHODS AND FINDINGS

Data were from 2 generations (offspring, Generation 1 [G1] born in 1991/1992 and their parents, Generation 0 [G0]) of a United Kingdom population-based birth cohort study, the Avon Longitudinal Study of Parents and Children (ALSPAC). Follow-up continues on the cohort; data up to 25 y after recruitment to the study are included in this analysis. Body mass index (BMI) and total fat mass from dual-energy X-ray absorptiometry (DXA) were measured at mean age 9 y, 15 y, and 18 y in G1. Waist circumference was measured at 9 y and 15 y in G1. Concentrations of 148 cardiometabolic traits quantified using nuclear magnetic resonance spectroscopy were measured at 15 y, 18 y, and 25 y in G1. In G0, all 3 adiposity measures and the same 148 traits were available at 50 y. Using linear regression models, sex-specific associations of adiposity measures at each time point (9 y, 15 y, and 18 y) with cardiometabolic traits 3 to 6 y later were examined in G1. In G0, sex-specific associations of adiposity measures and cardiometabolic traits were examined cross-sectionally at 50 y. A total of 3,081 G1 and 4,887 G0 participants contributed to analyses. BMI was more strongly associated with key atherogenic traits in males compared with females at younger ages (15 y to 25 y), and associations were more similar between the sexes or stronger in females at 50 y, particularly for apolipoprotein B-containing lipoprotein particles and lipid concentrations. For example, a 1 standard deviation (SD) (3.8 kg/m2) higher BMI at 18 y was associated with 0.36 SD (95% confidence interval [CI] = 0.20, 0.52) higher concentrations of extremely large very-low-density lipoprotein (VLDL) particles at 25 y in males compared with 0.15 SD (95% CI = 0.09, 0.21) in females, P value for sex difference = 0.02. By contrast, at 50 y, a 1 SD (4.8 kg/m2) higher BMI was associated with 0.33 SD (95% CI = 0.25, 0.42) and 0.30 SD (95% CI = 0.26, 0.33) higher concentrations of extremely large VLDL particles in males and females, respectively, P value for sex difference = 0.42. Sex-specific associations of DXA-measured fat mass and waist circumference with cardiometabolic traits were similar to findings for BMI and cardiometabolic traits at each age. The main limitation of this work is its observational nature, and replication in independent cohorts using methods that can infer causality is required.

CONCLUSIONS

The results of this study suggest that associations of adiposity with adverse cardiometabolic risk begin earlier in the life course among males compared with females and are stronger until midlife, particularly for key atherogenic lipids. Adolescent and young adult males may therefore be high priority targets for obesity prevention efforts.

A new phenotypic classification system for dyslipidemias based on the standard lipid panel

Background

Dyslipoproteinemias can be classified by their distinct lipoprotein patterns, which helps determine atherosclerotic cardiovascular disease (ASCVD) risk and directs lipid management but this has required advanced laboratory testing.

Objective

To develop a new algorithm for classifying lipoprotein disorders that only relies on the standard lipid panel.

Methods

Lipid thresholds for defining the different lipoprotein phenotypes were derived for Non-High-Density Lipoprotein-Cholesterol (NonHDL-C) and Triglycerides (TG) to be concordant when possible with the current US Multi-Society guidelines for blood cholesterol management.

Results

The new classification method categorizes patients into all the classical Fredrickson-like phenotypes except for Type III dysbetalipoproteinemia. In addition, a new hypolipidemic phenotype (Type VI) due to genetic mutations in apoB-metabolism is described. The validity of the new algorithm was confirmed by lipid analysis by NMR (N = 11,365) and by concordance with classification by agarose gel electrophoresis/beta-quantification (N = 5504). Furthermore, based on the Atherosclerosis Risk in Communities (ARIC) cohort (N = 14,742), the lipoprotein phenotypes differ in their association with ASCVD (TypeV>IIb > IVb > IIa > IVa > normolipidemic) and can be used prognostically as risk enhancer conditions in the management of patients.

Conclusions

We describe a clinically useful lipoprotein phenotyping system that is only dependent upon the standard lipid panel. It, therefore, can be easily implemented for increasing compliance with current guidelines and for improving the care of patients at risk for ASCVD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-021-01585-8.

A new algorithm is described for categorizing dyslipidemic patients into Fredrickson-like lipoprotein phenotypes except for Type III.

The new lipoprotein phenotypes were validated by NMR-lipoprotein analysis and by agarose gel electrophoresis/beta-quantification in a large number of subjects.

The new lipoprotein phenotyping system identifies high-risk cardiovascular patients and helps direct clinical management.

A major advance is that the new lipoprotein phenotypes are based on just the standard lipid panel, and thus can be automatically calculated by the clinical laboratory and widely implemented.

Familial dysbetalipoproteinemia: highly atherogenic and underdiagnosed disorder

Familial dysbetalipoproteinemia (FD) is a genetic, highly atherogenic disorder. The penetrance of FD depends on the patient’s lifestyle and concomitant diseases. Despite the fact that FD was described almost half a century ago, it is still insufficiently studied and is extremely rarely diagnosed. In actual clinical practice, physicians do not have clear understanding of clinical course and genetic basis of FD. The aim was to present the most complete, but at the same time a critical review with a modern view on FD. We analyzed Russian and foreign publications from following electronic databases: PubMed, eLIBRARY, Google Scholar. As a result, the phenotypic features and genetic variability of the disease were considered and the main issues of diagnosis and treatment of patients with FD were discussed. The data presented will help the clinician to timely suspect the FD, conduct a full range of investigations and prescribe evidence-based lipid-lowering therapy.

Hypotriglyceridemias/hypolipidemias

Hypolipoproteinemias are characterized by a decrease in the plasma concentration of lipoproteins. Within them, we find two groups: hypobetalipoproteinemias (HBL), due to a decrease in the plasma concentration of lipoproteins containing apolipoprotein B, and hypoalphalipoproteinemias. Hypolipoproteinemias can be classified according to their origin, into primary and secondary. Primary HBLs are rare entities produced by mutations in different genes. So far, more than 140 mutations have been identified in the APOB, PCSK9, ANGPTL3, MTTP, and SAR1 genes. Early diagnosis and treatment are essential to avoid the development of serious complications. In this review we address the diagnosis and treatment of HBL, especially those in which there is hypotriglyceridemia.

Apolipoprotein B: the Rosetta Stone of lipidology

PURPOSE OF REVIEW

This review summarizes the evidence that apolipoprotein B (apoB) integrates the conventional lipid markers - total cholesterol, triglycerides, LDL-cholesterol, and non-HDL-cholesterol - into a single index that accurately and simply quantitates the atherogenic risk due to the apoB lipoprotein particles.

RECENT FINDINGS

Marked hypertriglyceridemia remains the essential signal for hyperchylomicronemia and potential pancreatitis. However, with the exception of Lp(a) and the abnormal cholesterol-enriched remnant particles that are the hallmark of type III hyperlipoproteinemia, recent evidence from discordance analyses and Mendelian randomization indicate that apoB integrates the risk due to the atherogenic lipoprotein particles because all LDL particles are, within the limits of our ability to measure any differences, equally atherogenic and all, except the largest VLDL particles are, within the limits of our ability to measure any differences, equally atherogenic.

SUMMARY

Measuring apoB as well as the conventional lipids is essential for accurate diagnosis. For almost all follow-up, however, apoB is all that need be measured. ApoB is the Rosetta Stone of lipidology because dyslipoproteinemia cannot be understood unless apoB is measured.

Sex differences in systemic metabolites at four life stages: cohort study with repeated metabolomics

BACKGROUND

Males experience higher rates of coronary heart disease (CHD) than females, but the circulating traits underpinning this difference are poorly understood. We examined sex differences in systemic metabolites measured at four life stages, spanning childhood to middle adulthood.

METHODS

Data were from the Avon Longitudinal Study of Parents and Children (7727 offspring, 49% male; and 6500 parents, 29% male). Proton nuclear magnetic resonance (1H-NMR) spectroscopy from a targeted metabolomics platform was performed on EDTA-plasma or serum samples to quantify 229 systemic metabolites (including lipoprotein-subclass-specific lipids, pre-glycaemic factors, and inflammatory glycoprotein acetyls). Metabolites were measured in the same offspring once in childhood (mean age 8 years), twice in adolescence (16 years and 18 years) and once in early adulthood (25 years), and in their parents once in middle adulthood (50 years). Linear regression models estimated differences in metabolites for males versus females on each occasion (serial cross-sectional associations).

RESULTS

At 8 years, total lipids in very-low-density lipoproteins (VLDL) were lower in males; levels were higher in males at 16 years and higher still by 18 years and 50 years (among parents) for medium-or-larger subclasses. Larger sex differences at older ages were most pronounced for VLDL triglycerides-males had 0.19 standard deviations (SD) (95% CI = 0.12, 0.26) higher at 18 years, 0.50 SD (95% CI = 0.42, 0.57) higher at 25 years, and 0.62 SD (95% CI = 0.55, 0.68) higher at 50 years. Low-density lipoprotein (LDL) cholesterol, apolipoprotein-B, and glycoprotein acetyls were generally lower in males across ages. The direction and magnitude of effects were largely unchanged when adjusting for body mass index measured at the time of metabolite assessment on each occasion.

CONCLUSIONS

Our results suggest that males begin to have higher VLDL triglyceride levels in adolescence, with larger sex differences at older ages. Sex differences in other CHD-relevant metabolites, including LDL cholesterol, show the opposite pattern with age, with higher levels among females. Such life course trends may inform causal analyses with clinical endpoints in specifying traits which underpin higher age-adjusted CHD rates commonly seen among males.

Evaluation of the chylomicron-TG to VLDL-TG ratio for type I hyperlipoproteinemia diagnostic

BACKGROUND

The aim of this study is to confirm the diagnostic performance of the Chylomicron to very low-density lipoproteins triglycerides (CM/VLDL-TG) ratio, the triglycerides to cholesterol ratio (TG/TC) and a dichotomic rule including the tryglycerides to apolipoprotein B (TG/APOB) ratio for the presence of Type I hyperlipoproteinemia (HPLI) in patients with severe hypertriglyceridemia (sHTG) that were at high risk for familial chylomicronemia syndrome (FCS).

METHODS

Two cohorts (derivation and validation) of patients with sHTG were included in the study. Anthropometric, clinical, biochemical and genetic data were obtained. The CM/VLDL-TG, TG/TC and TG/APOB ratios were calculated. Finally, a diagnostic performance study was developed to establish sensitivity, specificity and cut-offs by a ROC curve analysis in the derivation cohort as well as agreement and predictive values in the validation cohort.

RESULTS

Patients with FCS in both cohorts showed an earlier presence in pancreatitis, greater number of acute pancreatitis episodes and lower BMI. FCS patients also showed higher ratios of CM/VLDL-TG, TG/TC and TG/APOB ratios, whereas their HDL-C, LDL-C and APOB levels were lower than in non-FCS patients. Sensitivity and agreement were low for both the TG/TC and TG/APOB ratios, although predictive values were good. The CM/VLDL-TG ratio showed greatest sensitivity, specificity, agreement and predictive values for cut-off of 3.8 and 4.5.

CONCLUSIONS

Our results suggest that in subjects at high risk of FCS a total serum TG/TC ratio or TG/APOB ratio are feasible to initially screen for HLPI; however, a CM/VLDL-TG ratio ≥4.5 is a better diagnostic criterion for HPLI.

Importance of the triglyceride level in identifying patients with a Type III Hyperlipoproteinemia phenotype using the ApoB algorithm

BACKGROUND

Hyperlipoproteinemia Type III (HLP3), also known as dysbetalipoproteinemia, is defined by cholesterol and triglyceride (TG) enriched remnant lipoprotein particles (RLP). The gold standard for diagnosis requires demonstration of high remnant lipoprotein particle cholesterol (RLP-C) by serum ultracentrifugation (UC), which is not readily available in daily practice. The apoB algorithm can identify HLP3 using total cholesterol (TC), plasma triglyceride (TG), and apoB. However, the optimal TG cutoff is unknown.

OBJECTIVE

We analyzed apoB algorithm defined HLP3 at different TG levels to optimize the TG cutoff for the algorithm.

METHODS

128,485 UC lipid profiles in the Very Large Database of Lipids (VLDbL) were analyzed. RLP-C was assessed at TG ≥ 133 mg/dL, ≥175 mg/dL, ≥200 mg/dL, and ≥ 250 mg/dL. Sensitivity (Sn), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV), and prevalence adjusted and bias-adjusted kappa (PABAK) were calculated against UC Criterion (VLDL-C/TG ≥ 0.25) for HLP3.

RESULTS

The median age (IQR) was 57 years (46-68). 45% were men, 20.1% had diabetes, and 25.5% had hypertension. The median RLP-C level for the TG cutoffs (mg/dL) of ≥ 133, ≥ 175, ≥ 200, and ≥ 250 were 34, 43, 50, and 62 mg/dL, respectively, compared to 67 mg/dL in UC defined HLP3. TG ≥ 133 mg/dL yielded optimal results (Sn 29.5%, Sp 98.5%, PABAK 0.96, PPV 13.6%, NPV 99.4%).

CONCLUSION

TG ≥ 133 mg/dL allows for high sensitivity in screening for HLP3. Higher TG cutoffs may identify more severe HLP3 phenotypes, but with a large loss in sensitivity for HLP3.

Modern prevalence of the Fredrickson-Levy-Lees dyslipidemias: findings from the Very Large Database of Lipids and National Health and Nutrition Examination Survey

INTRODUCTION

Five decades ago, Fredrickson, Levy, and Lees (FLL) qualitatively characterized clinical dyslipidemias with specific implications for cardiovascular and non-cardiovascular morbidity and mortality. They separated disorders of elevated cholesterol and triglycerides into five phenotypes (types I-V) based on their lipoprotein profile. Although clinicians generally consider them rare entities, modern FLL prevalence may be greater than previously reported.

MATERIAL AND METHODS

We performed a cross-sectional analysis in 5,272 participants from the 2011-2014 National Health and Nutrition Examination Survey and 128,506 participants from the Very Large Database of Lipids study with complete, fasting lipid profiles. We used a validated algorithm to define FLL phenotypes employing apolipoprotein B, total cholesterol, and triglycerides.

RESULTS

Overall prevalence of FLL phenotypes was 33.9%. FLL prevalence in the general population versus clinical lipid database was: type I (0.05 vs. 0.02%), type IIa (3.2 vs. 3.9%), type IIb (8.0 vs. 10.3%), type III (2.0 vs. 1.7%), type IV (20.5 vs. 24.1%), and type V (0.15 vs. 0.13%). Those aged 40-74 years had a higher overall prevalence compared to other age groups (p < 0.001) and men had overall higher prevalence than women (p < 0.001). Those with diabetes (51.6%) or obese BMI (49.0%) had higher prevalence of FLL phenotypes compared to those without diabetes (31.3%; p < 0.001) and normal BMI (18.3%; p < 0.001).

CONCLUSIONS

FLL phenotypes are likely far more prevalent than appreciated in clinical practice, in part due to diabetes and obesity epidemics. Given the prognostic and therapeutic importance of these phenotypes, their identification becomes increasingly important in the era of precision medicine.

Modern prevalence of dysbetalipoproteinemia (Fredrickson-Levy-Lees type III hyperlipoproteinemia)

INTRODUCTION

Dysbetalipoproteinaemia (HLP3) is a disorder characterized by excess cholesterol-enriched, triglyceride-rich lipoprotein remnants in genetically predisposed individuals that powerfully promote premature cardiovascular disease if untreated. The current prevalence of HLP3 is largely unknown.

MATERIAL AND METHODS

We performed cross-sectional analysis of 128,485 U.S. adults from the Very Large Database of Lipids (VLDbL), using four algorithms to diagnose HLP3 employing three Vertical Auto Profile ultracentrifugation (UC) criteria and a previously described apolipoprotein B (apoB) method. We evaluated 4,926 participants from the 2011-2014 National Health and Nutrition Examination Survey (NHANES) with the apoB method. We examined demographic and lipid characteristics stratified by presence of HLP3 and evaluated lipid characteristics in those with HLP3 phenotype discordance and concordance as determined by apoB and originally defined UC criteria 1.

RESULTS

In U.S. adults in VLDbL and NHANES, a 1.7-2.0% prevalence is observed for HLP3 with the novel apoB method as compared to 0.2-0.8% prevalence in VLDbL via UC criteria 1-3. Participants who were both apoB and UC criteria HLP3 positive had higher remnant particles as well as more elevated triglyceride/apoB and total cholesterol/apoB ratios (all p < 0.001) than those who were apoB method positive and UC criteria 1 negative.

CONCLUSIONS

HLP3 may be more prevalent than historically and clinically appreciated. The apoB method increases HLP3 identification via inclusion of milder phenotypes. Further work should evaluate the clinical implications of HLP3 diagnosis at various lipid algorithm cut-points to evaluate the ideal standard in the modern era.

Genetic risk scores to predict the prognosis of chronic heart failure patients in Chinese Han

Chronic heart failure (CHF) has poor prognosis and polygenic heritability, and the genetic risk score (GRS) to predict CHF outcome has not yet been researched comprehensively. In this study, we sought to establish GRS to predict the outcomes of CHF. We re-analysed the proteomics data of failing human heart and combined them to filter the data of high-throughput sequencing in 1000 Chinese CHF cohort. Cox hazards models were used based on single nucleotide polymorphisms (SNPs) to estimate the association of GRS with the prognosis of CHF, and to analyse the difference between individual SNPs and tertiles of genetic risk. In the cohort study, GRS encompassing eight SNPs harboured in seven genes were significantly associated with the prognosis of CHF (P = 2.19 × 10^-10 after adjustment). GRS was used in stratifying individuals into significantly different CHF risk, with those in the top tertiles of GRS distribution having HR of 3.68 (95% CI: 2.40-5.65 P = 2.47 × 10^-10 ) compared with those in the bottom. We developed GRS and demonstrated its association with first event of heart failure endpoint. GRS might be used to stratify individuals for CHF prognostic risk and to predict the outcomes of genomic screening as a complement to conventional risk and NT-proBNP.

Characterization of lipoprotein profiles in patients with hypertriglyceridemic Fredrickson-Levy and Lees dyslipidemia phenotypes: the Very Large Database of Lipids Studies 6 and 7

INTRODUCTION

The association between triglycerides (TG) and cardiovascular diseases is complex. The classification of hypertriglyceridemic (HTG) phenotypes proposed by Fredrickson, Levy and Lees (FLL) helps inform treatment strategies. We aimed to describe levels of several lipoprotein variables from individuals with HTG FLL phenotypes from the Very Large Database of Lipids.

MATERIAL AND METHODS

We included fasting samples from 979,539 individuals from a contemporary large study population of US adults. Lipids were directly measured by density-gradient ultracentrifugation using the Vertical Auto Profile test while TG levels were measured in whole plasma using the Abbott ARCHITECT C-8000 system. Hyperchylomicronemic (Hyper-CM) and non-chylomicronemic (non-CM) phenotypes were defined using computationally derived models. Individuals with FLL type IIa phenotype were excluded. Distributions of lipid variables were compared using medians and Kruskal-Wallis test.

RESULTS

A total of 11.9% (n = 116,925) of individuals met criteria for HTG FLL phenotypes. Those with hyper-CM phenotypes (n = 5, < 0.1% of population) had two-fold higher TG levels compared with non-chylomicronemic (non-CM) individuals (11.9% of population) (p < 0.001). Type IIb individuals had the highest non-HDL-C levels (median 242 mg/dl). Cholesterol in large VLDL₁₊₂ particles was higher than in small VLDL₃ particles in all phenotypes except FLL type III. Hyper-CM phenotypes had significantly lower HDL-C levels but greater HDL₂/HDL₃-C ratio compared to non-CM phenotypes. Cholesterol content of the lipoprotein (a) peak was significantly higher in the hyper-CM groups compared to non-CM phenotypes (p < 0.0001).

CONCLUSIONS

This observational hypothesis-generating study provides insight into the complexity of lipid metabolism in HTG phenotypes, including less traditional lipid measures such as LDL density, HDL subclasses and Lp(a)-C.

Comparative quantitative systems pharmacology modeling of anti-PCSK9 therapeutic modalities in hypercholesterolemia

Since the discovery of proprotein convertase subtilisin/kexin type 9 (PCSK9) as an attractive target in the treatment of hypercholesterolemia, multiple anti-PCSK9 therapeutic modalities have been pursued in drug development. The objective of this research is to set the stage for the quantitative benchmarking of two anti-PCSK9 pharmacological modality classes, monoclonal antibodies (mAbs) and small interfering RNA (siRNA). To this end, we developed an integrative mathematical model of lipoprotein homeostasis describing the dynamic interplay between PCSK9, LDL-cholesterol (LDL-C), VLDL-cholesterol, HDL-cholesterol (HDL-C), apoB, lipoprotein a [Lp(a)], and triglycerides (TGs). We demonstrate that LDL-C decreased proportionally to PCSK9 reduction for both mAb and siRNA modalities. At marketed doses, however, treatment with mAbs resulted in an additional ∼20% LDL-C reduction compared with siRNA. We further used the model as an evaluation tool and determined that no quantitative differences were observed in HDL-C, Lp(a), TG, or apoB responses, suggesting that the disruption of PCSK9 synthesis would provide no additional effects on lipoprotein-related biomarkers in the patient segment investigated. Predictive model simulations further indicate that siRNA therapies may reach reductions in LDL-C levels comparable to those achieved with mAbs if the current threshold of 80% PCSK9 inhibition via siRNA could be overcome.

Which Lipids Should Be Analyzed for Diagnostic Workup and Follow-up of Patients with Hyperlipidemias?

PURPOSE OF REVIEW

To summarize and discuss the clinical use of lipid and apolipoprotein tests in the settings of diagnosis and therapeutic follow-up of hyperlipidemia.

RECENT FINDINGS

The joint consensus panel of the European Atherosclerosis Society (EAS) and the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) recently produced recommendations on the measurement of atherogenic lipoproteins, taking into account the strengths and weaknesses of analytical and clinical performances of the tests. Total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, and calculated non-HDL cholesterol (= LDL + remnant cholesterol) constitute the primary lipid panel for hyperlipidemia diagnosis and cardiovascular risk estimation. LDL cholesterol is the primary target of lipid-lowering therapies. Non-HDL cholesterol or apolipoprotein B should be used as secondary therapeutic target in patients with mild-to-moderate hypertriglyceridemia, 2-10 mmol/l (175-880 mg/dl). Lipoprotein (a) is included in LDL cholesterol and should be measured at least once in all patients at cardiovascular risk, including to explain poor response to statin treatment.

Quantifying Atherogenic Lipoproteins: Current and Future Challenges in the Era of Personalized Medicine and Very Low Concentrations of LDL Cholesterol. A Consensus Statement from EAS and EFLM

BACKGROUND

The European Atherosclerosis Society-European Federation of Clinical Chemistry and Laboratory Medicine Consensus Panel aims to provide recommendations to optimize atherogenic lipoprotein quantification for cardiovascular risk management.

CONTENT

We critically examined LDL cholesterol, non-HDL cholesterol, apolipoprotein B (apoB), and LDL particle number assays based on key criteria for medical application of biomarkers. (a) Analytical performance: Discordant LDL cholesterol quantification occurs when LDL cholesterol is measured or calculated with different assays, especially in patients with hypertriglyceridemia >175 mg/dL (2 mmol/L) and low LDL cholesterol concentrations <70 mg/dL (1.8 mmol/L). Increased lipoprotein(a) should be excluded in patients not achieving LDL cholesterol goals with treatment. Non-HDL cholesterol includes the atherogenic risk component of remnant cholesterol and can be calculated in a standard nonfasting lipid panel without additional expense. ApoB more accurately reflects LDL particle number. (b) Clinical performance: LDL cholesterol, non-HDL cholesterol, and apoB are comparable predictors of cardiovascular events in prospective population studies and clinical trials; however, discordance analysis of the markers improves risk prediction by adding remnant cholesterol (included in non-HDL cholesterol) and LDL particle number (with apoB) risk components to LDL cholesterol testing. (c) Clinical and cost-effectiveness: There is no consistent evidence yet that non-HDL cholesterol-, apoB-, or LDL particle-targeted treatment reduces the number of cardiovascular events and healthcare-related costs than treatment targeted to LDL cholesterol.

SUMMARY

Follow-up of pre- and on-treatment (measured or calculated) LDL cholesterol concentration in a patient should ideally be performed with the same documented test method. Non-HDL cholesterol (or apoB) should be the secondary treatment target in patients with mild to moderate hypertriglyceridemia, in whom LDL cholesterol measurement or calculation is less accurate and often less predictive of cardiovascular risk. Laboratories should report non-HDL cholesterol in all standard lipid panels.

Effects of blood lipid stability on progression of carotid atherosclerosis

Objective:

To evaluate the effects of blood lipid stability on progression of carotid atherosclerosis.

Methods:

A total of 416 patients who had physical examination in our hospital annually from January 2010 to December 2015 were selected and divided into a progression group (n=216) and a non-progression group (n=200) according to the intima-media thickness measured by carotid ultrasound. The levels of lipid-related parameters within five years were retrospectively analyzed to calculate the smoothness index (SI = x±/s).

Results:

The cross-sectional TG, HDL-C, ApoAI, ApoB, ApoE and Lpa levels were similar in the two groups (p>0.05). The non-progression group had significantly higher TC ((4.15±0.82 vs. 4.50±1.04) mmol/L) and LDL-C ((2.53±0.76 vs. 2.99±1.03) mmol/L) levels than those of the progression group (p<0.05). The progression group had significantly lower TC SI (5.29±1.28 vs. 5.65±1.76), TG SI (2.13±0.71 vs. 2.79±0.82), LDL-C SI (3.66±1.17 vs. 4.36±1.58), ApoB SI (3.37±0.88 vs. 3.62±0.95) and Lpa SI (1.53±0.49 vs. 1.62±0.43) than those of the non-progression group (p<0.05).

Conclusion:

Compared with cross-sectional results, SI was better correlated with the progression of atherosclerosis. The progression group had lower SI values.

Membrane Protein Quantity Control at the Endoplasmic Reticulum

The canonical function of the endoplasmic reticulum-associated degradation (ERAD) system is to enforce quality control among membrane-associated proteins by targeting misfolded secreted, intra-organellar, and intramembrane proteins for degradation. However, increasing evidence suggests that ERAD additionally functions in maintaining appropriate levels of a subset of membrane-associated proteins. In this 'quantity control' capacity, ERAD responds to environmental cues to regulate the proteasomal degradation of specific ERAD substrates according to cellular need. In this review, we discuss in detail seven proteins that are targeted by the ERAD quantity control system. Not surprisingly, ERAD-mediated protein degradation is a key regulatory feature of a variety of ER-resident proteins, including HMG-CoA reductase, cytochrome P450 3A4, IP3 receptor, and type II iodothyronine deiodinase. In addition, the ERAD quantity control system plays roles in maintaining the proper stoichiometry of multi-protein complexes by mediating the degradation of components that are produced in excess of the limiting subunit. Perhaps somewhat unexpectedly, recent evidence suggests that the ERAD quantity control system also contributes to the regulation of plasma membrane-localized signaling receptors, including the ErbB3 receptor tyrosine kinase and the GABA neurotransmitter receptors. For these substrates, a proportion of the newly synthesized yet properly folded receptors are diverted for degradation at the ER, and are unable to traffic to the plasma membrane. Given that receptor abundance or concentration within the plasma membrane plays key roles in determining signaling efficiency, these observations may point to a novel mechanism for modulating receptor-mediated cellular signaling.

High prevalence of apolipoprotein B dyslipoproteinemias in non-alcoholic fatty liver disease: The lifelines cohort study

OBJECTIVE

Cardiovascular disease (CVD) is a major adverse consequence of non-alcoholic fatty liver disease (NAFLD). The association of NAFLD with various apolipoprotein B (apoB) dyslipoproteinemias is unclear. We determined the prevalence of specific apoB dyslipoproteinemias in subjects with suspected NAFLD.

METHODS

This study was conducted among 22,865 fasting adults living in the northern part of the Netherlands (Lifelines Cohort Study). Six apoB dyslipoproteinemias were defined using an algorithm derived from apoB, total cholesterol and triglycerides. NAFLD was defined as Fatty Liver Index (FLI) ≥60. Advanced hepatic fibrosis was defined as NAFLD fibrosis score (NFS) ≥0.676.

RESULTS

4790 participants (20.9%) had an FLI≥60. NAFLD subjects were older, more likely to be men, more obese and more often had diabetes and metabolic syndrome (P<0.001 for each). Among NAFLD subjects, any apoB dyslipoproteinemia was present in 61.5% vs. 16.5% in subjects without NAFLD (P<0.001). Elevated chylomicrons were not observed in NAFLD. In univariate analysis, NAFLD was associated with a higher prevalence of each apoB dyslipoproteinemia vs. subjects with an FLI<60 (P<0.001), except for low density lipoprotein (LDL) dyslipoproteinemia. Additionally, each apoB dyslipoproteinemia was independently associated with NAFLD in age- and sex-adjusted logistic regression analysis, including the apoB dyslipoproteinemias together (P<0.001). The prevalence of apoB dyslipoproteinemias was not altered in subjects with NFS ≥0.676.

CONCLUSIONS

NAFLD rather than advanced hepatic fibrosis is independently associated with increased prevalence of chylomicrons+very low-density lipoproteins (VLDL) remnants, VLDL, LDL and VLDL+LDL dyslipoproteinemias. ApoB dyslipoproteinemias may contribute to increased CVD risk associated with NAFLD.

Genomic Variants Associated with Resistance to High Fat Diet Induced Obesity in a Primate Model

Maternal obesity contributes to an increased risk of lifelong morbidity and mortality for both the mother and her offspring. In order to better understand the molecular mechanisms underlying these risks, we previously established and extensively characterized a primate model in Macaca fuscata (Japanese macaque). In prior studies we have demonstrated that a high fat, caloric dense maternal diet structures the offspring’s epigenome, metabolome, and intestinal microbiome. During the course of this work we have consistently observed that a 36% fat diet leads to obesity in the majority, but not all, of exposed dams. In the current study, we sought to identify the genomic loci rendering resistance to obesity despite chronic consumption of a high fat diet in macaque dams. Through extensive phenotyping together with exon capture array and targeted resequencing, we identified three novel single nucleotide polymorphisms (SNPs), two in apolipoprotein B (APOB) and one in phospholipase A2 (PLA2G4A) that significantly associated with persistent weight stability and insulin sensitivity in lean macaques. By application of explicit orthogonal modeling (NOIA), we estimated the polygenic and interactive nature of these loci against multiple metabolic traits and their measures (i.e., serum LDL levels) which collectively render an obesity resistant phenotype in our adult female dams.

Lipid phenotypes in patients with nonalcoholic fatty liver disease

OBJECTIVE

There has been conflicting evidence regarding the role of single lipid species in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). We aimed to explore the associations between dyslipidemia phenotypes (combinations of lipid parameters) and the risk of NAFLD.

METHODS

We conducted a cross-sectional analysis using a cohort of 9560 apparently healthy Chinese adults who underwent comprehensive health checkups including abdominal ultrasonography.

RESULTS

Of 3709 participants with NAFLD, 41.8% were classified as normolipemia (NL), 3.8% as combined hyperlipidemia, 3.2% as hypercholesterolemia, 17.7% as dyslipidemia of metabolic syndrome (MetS), 10.2% as isolated low high-density lipoprotein cholesterol (HDL-C), and 23.3% as isolated hypertriglyceridemia. The multivariable-adjusted odds ratios (ORs) (with 95% confidence intervals) for NAFLD in those with combined hyperlipidemia, those with hypercholesterolemia, those with MetS dyslipidemia, those with low HDL-C, and those with hypertriglyceridemia compared with those with NL were 4.79 (3.19-7.20), 1.26 (0.94-1.69), 3.31 (2.74-3.99), 1.13 (0.95-1.34), and 2.63 (2.26-3.08), respectively. The associations between combined hyperlipidemia, MetS dyslipidemia, or hypertriglyceridemia and risk of NAFLD were consistently seen in various evaluated subgroups. The interactions between lipid phenotypes and sex, body mass index (BMI), blood pressure (BP), fasting plasma glucose (FPG), or uric acid (UA) were not significant for NAFLD (all P>0.05).

CONCLUSIONS

There were diverse dyslipidemia phenotypes in patients with NAFLD. Combined hyperlipidemia, MetS dyslipidemia, and hypertriglyceridemia were strongly and independently associated with increased risk of NAFLD. Gender, BMI, BP, FPG, and UA status did not modify the associations between dyslipidemia phenotypes and NAFLD.

Apolipoprotein B improves risk assessment of future coronary heart disease in the Framingham Heart Study beyond LDL-C and non-HDL-C

AIMS

Analyses using conventional statistical methodologies have yielded conflicting results as to whether low-density lipoprotein cholesterol (LDL-C) or non-high-density lipoprotein cholesterol (non-HDL-C) or apolipoprotein B (apoB) is the best marker of the apoB-associated risk of coronary heart disease. The aim of this study was to determine the additional value of apoB beyond LDL-C or non-HDL-C as a predictor of coronary heart disease.

METHODS AND RESULTS

For each patient from the Framingham Offspring Cohort aged 40-75 years (n = 2966), we calculated the extent to which the observed apoB differed from the expected apoB based on their LDL-C or non-HDL-C. We added this difference to a Cox model predicting new onset coronary heart disease over a maximum of 20 years adjusting for standard risk factors plus LDL-C or non-HDL. The difference between observed and expected apoB over LDL-C or non-HDL-C was highly prognostic of future coronary heart disease events: adjusted hazard ratios 1.26 (95% confidence interval: 1.15, 1.37) and 1.20 (1.11, 1.29), respectively, for each standard deviation increase beyond expected apoB levels. When this difference between observed and expected apoB was added to standard coronary heart disease prediction models including LDL-C or non-HDL-C, prediction improved significantly (likelihood ratio test p-values <0.0001) and discrimination c-statistics increased from 0.72 to 0.73. The corresponding relative integrated discrimination improvements were 11% and 8%, respectively.

CONCLUSIONS

apoB improves risk assessment of future coronary heart disease events over and beyond LDL-C or non-HDL-C, which is consistent with coronary risk being more closely related to the number of atherogenic apoB particles than to the mass of cholesterol within them.

Re-editing the paradigm of Cytidine (C) to Uridine (U) RNA editing

Cytidine (C) to Uridine (U) RNA editing is a post-trancriptional modification that until recently was known to only affect Apolipoprotein b (Apob) RNA and minimally require 2 components of the C to U editosome, the deaminase APOBEC1 and the RNA-binding protein A1CF. Our latest work has identified a novel RNA-binding protein, RBM47, as a core component of the editosome, which can substitute A1CF for the editing of ApoB mRNA. In addition, new RNA species that are subjected to C to U editing have been identified. Here, we highlight these recent discoveries and discuss how they change our view of the composition of the C to U editing machinery and expand our knowledge of the functional attributes of C to U RNA editing.

Lipid phenotypes at the extremes of high-density lipoprotein cholesterol: The very large database of lipids-9

BACKGROUND

Low serum levels of high-density lipoprotein cholesterol (HDL-C) are an important risk factor for atherosclerotic disease. To date, therapeutically raising HDL-C has not been shown to impact risk for cardiovascular events.

OBJECTIVE

We aim to characterize lipid parameters at the extremes of HDL-C.

METHODS

We examined cholesterol profiles from 1,350,908 US adults and children from the Very Large Database of Lipids who were clinically referred for advanced lipoprotein testing from 2009 to 2011. We categorized patients into HDL-C percentile categories (<0.1th, 0.1th-<1st, 1st-5th, 25th-75th, 95th-99th, >99th-99.9th, and >99.9th). Within these groups, we examined HDL-C subclasses, low-density lipoprotein cholesterol (LDL-C), LDL and very-low density lipoprotein densities, non-HDL-C, triglycerides (TG), very-low density lipoprotein cholesterol, and remnant lipoprotein cholesterol (RLP-C), as well as prevalence of Fredrickson-Levy dyslipidemias.

RESULTS

Extremely low HDL-C percentiles were associated with increased LDL density, TG, and especially RLP-C. Very high HDL-C levels (≥ 92 mg/dL) showed increasing HDL2-C/HDL3-C ratio and very low levels of RLP-C and triglyceride-rich lipoproteins. Type IV dyslipidemia had the highest prevalence among classical dyslipidemia and was the most frequent at extremely low HDL-C percentiles.

CONCLUSIONS

These findings demonstrate a high prevalence of elevated triglyceride-rich lipoprotein levels and increased LDL density in patients with extremely low HDL-C levels. The relative contributions of these various changes in lipid profiles of patients with low HDL-C to cardiovascular risk need to be further scrutinized to more fully establish if low HDL-C is truly an independent risk factor for coronary heart disease or simply reflects detrimental shifts in the levels of atherogenic lipoproteins.

Discordance analysis and the Gordian Knot of LDL and non-HDL cholesterol versus apoB

PURPOSE OF REVIEW

Conventional methods, comparing the concentration of cholesterol to particle number as indices of cardiovascular risk, have not produced consistent results, in large part, because they treat these variables as independent and unrelated. However, although highly correlated, apolipoprotein B particles may contain a normal mass of cholesterol or may be cholesterol-depleted or cholesterol-enriched. Discordance analysis compares the predictive power of LDL-C and non-HDL-C to apolipoprotein B and LDL particle numbers in patients in whom they differ, that is, in whom they are discordant. The advantage of discordance analysis is that the results are not diluted by concordant data in which risk predictions cannot differ.

RECENT FINDINGS

The evidence, to date, consistently demonstrates that apolipoprotein B and LDL particle numbers are more accurate indices of cardiovascular risk than LDL-C or non-HDL-C.

SUMMARY

Discordance analysis is a methodological advance that allows the clinical value of closely correlated variables to be determined and demonstrates that cardiovascular risk is more closely related to the number of atherogenic particles than to the total mass of cholesterol within them.

C to U RNA editing mediated by APOBEC1 requires RNA-binding protein RBM47

Cytidine (C) to Uridine (U) RNA editing is a post-transcriptional modification that is accomplished by the deaminase APOBEC1 and its partnership with the RNA-binding protein A1CF. We identify and characterise here a novel RNA-binding protein, RBM47, that interacts with APOBEC1 and A1CF and is expressed in tissues where C to U RNA editing occurs. RBM47 can substitute for A1CF and is necessary and sufficient for APOBEC1-mediated editing in vitro. Editing is further impaired in Rbm47-deficient mutant mice. These findings suggest that RBM47 and APOBEC1 constitute the basic machinery for C to U RNA editing.

Calculation of LDL apoB

OBJECTIVES

This study tests the validity of the Hattori formula to calculate LDL apoB based on plasma lipids and total apoB.

METHODS

In 2178 patients in a tertiary care lipid clinic, LDL apoB calculated as suggested by Hattori et al. was compared to directly measured LDL apoB isolated by ultracentrifugation.

RESULTS

In subjects with plasma triglycerides ≥ 3.0 mmol/L, there was considerable discordance between calculated and measured LDL apoB. In all others, the relation between measured LDL apoB and calculated LDL apoB could be expressed as LDL apoB = 0.86 [total apoB - 0.9 TC (mg/dL) + 0.09 HDL-C (mg/dL) - 0.08 TG (mg/dL)] - 7.0 (r > 0.91; P < 0.0001).

CONCLUSIONS

Our results indicate that LDL apoB can be calculated with reasonable accuracy when triglycerides are <3.0 mmol/L. However, the calculation suggested by Hattori et al. should be corrected based on the regression demonstrated between calculated and measured LDL apoB in subjects with a plasma triglyceride <3.0 mmol/L.

Apolipoprotein B100 quality control and the regulation of hepatic very low density lipoprotein secretion

Apolipoprotein B (apoB) is the main protein component of very low density lipoprotein (VLDL) and is necessary for the assembly and secretion of these triglyceride (TG)-rich particles. Following release from the liver, VLDL is converted to low density lipoprotein (LDL) in the plasma and increased production of VLDL can therefore play a detrimental role in cardiovascular disease. Increasing evidence has helped to establish VLDL assembly as a target for the treatment of dyslipidemias. Multiple factors are involved in the folding of the apoB protein and the formation of a secretion-competent VLDL particle. Failed VLDL assembly can initiate quality control mechanisms in the hepatocyte that target apoB for degradation. ApoB is a substrate for endoplasmic reticulum associated degradation (ERAD) by the ubiquitin proteasome system and for autophagy. Efficient targeting and disposal of apoB is a regulated process that modulates VLDL secretion and partitioning of TG. Emerging evidence suggests that significant overlap exists between these degradative pathways. For example, the insulin-mediated targeting of apoB to autophagy and postprandial activation of the unfolded protein response (UPR) may employ the same cellular machinery and regulatory cues. Changes in the quality control mechanisms for apoB impact hepatic physiology and pathology states, including insulin resistance and fatty liver. Insulin signaling, lipid metabolism and the hepatic UPR may impact VLDL production, particularly during the postprandial state. In this review we summarize our current understanding of VLDL assembly, apoB degradation, quality control mechanisms and the role of these processes in liver physiology and in pathologic states.