Lipoprotein(a) Mass Levels Increase Significantly According to APOE Genotype: An Analysis of 431 239 Patients

Lipoprotein(a) and cardiovascular disease

Elevated plasma levels of lipoprotein(a) (Lp(a)) are a prevalent, independent, and causal risk factor for atherosclerotic cardiovascular disease and calcific aortic valve disease. Lp(a) consists of a lipoprotein particle resembling low density lipoprotein and the covalently-attached glycoprotein apolipoprotein(a) (apo(a)). Novel therapeutics that specifically and potently lower Lp(a) levels are currently in advanced stages of clinical development, including in large, phase 3 cardiovascular outcomes trials. However, fundamental unanswered questions remain concerning some key aspects of Lp(a) biosynthesis and catabolism as well as the true pathogenic mechanisms of the particle. In this review, we describe the salient biochemical features of Lp(a) and apo(a) and how they underlie the disease-causing potential of Lp(a), the factors that determine plasma Lp(a) concentrations, and the mechanism of action of Lp(a)-lowering drugs.

Association of Apolipoprotein E (APOE) Polymorphisms With Serological Lipid and Inflammatory Markers

Background  The study aims to assess the association of apolipoprotein E (APOE) gene polymorphisms with serological lipid and inflammatory markers to determine their potential role in predicting the risk of cardiovascular diseases (CVDs) and Alzheimer's disease (AD).  Methodology  A total of 915 individuals underwent testing for lipid and inflammatory biomarkers at Vibrant America Clinical Laboratory. Clinical data, blood lipid and inflammatory profiles, and APOE genotyping were analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).  Results Compared to the E3/E3 genotype, individuals with E2/E3 genotypes showed higher levels of high-density lipoprotein (HDL), triglycerides, apolipoprotein A (APOA), high-sensitivity C-reactive protein (hs-CRP), and myeloperoxidase (MPO). E2/E4 genotype carriers had higher levels of HDL, triglycerides, Lp(a), and N-terminal pro b-type natriuretic peptide (BNPNT). E3/E4 genotypes were associated with elevated levels of total cholesterol, LDL, Lp(a), hs-CRP, small-density low-density lipoprotein (SDLDL), oxidized LDL (OXLDL), MPO, LDL-CAL, PLAC, and APOB. The E4/E4 group displayed higher concentrations of total cholesterol, LDL, APOB, Lp(a), hs-CRP, SDLDL, OXLDL, MPO, LDLCAL, and PLAC compared to E3/E3 carriers. These findings highlight the potential atherogenic effect of the ε4 allele and the protective effect of the ε2 allele based on lipid and inflammatory marker profiles.  Conclusions This study provides strong evidence linking APOE gene polymorphism to abnormal serum lipid and inflammatory profiles. Individuals carrying the ε4 alleles exhibited dysregulated lipid metabolism and abnormal inflammatory markers, increasing their risk of CVD and AD. Early detection and prompt diagnosis are crucial for implementing therapeutic, dietary, and lifestyle interventions to mitigate risks and prevent or delay lipid and inflammation-related disorders.

Influence of triglyceride concentration in lipoprotein (a) as a function of dyslipidemia

BACKGROUND

Recently, an inverse relationship between the blood concentration of lipoprotein(a) (Lp(a)) and triglycerides (TG) has been demonstrated. The larger the VLDL particle size, the greater the presence of VLDL rich in apoliprotein E and in subjects with the apoE2/E2 genotype, the lower Lp(a) concentration. The mechanism of this inverse association is unknown. The objective of this analysis was to evaluate the Lp(a)-TG association in patients treated at the lipid units included in the registry of the Spanish Society of Atherosclerosis (SEA) by comparing the different dyslipidemias.

PATIENTS AND METHODS

Five thousand two hundred and seventy-five subjects ≥18 years of age registered in the registry before March 31, 2023, with Lp(a) concentration data and complete lipid profile information without treatment were included.

RESULTS

The mean age was 53.0 ± 14.0 years, with 48% women. The 9.5% of subjects (n = 502) had diabetes and the 22.4% (n = 1184) were obese. The median TG level was 130 mg/dL (IQR 88.0-210) and Lp(a) 55.0 nmol/L (IQR 17.9-156). Lp(a) concentration showed a negative association with TG concentration when TG values exceeded 300 mg/dL. Subjects with TG > 1000 mg/dL showed the lowest level of Lp(a), 17.9 nmol/L, and subjects with TG < 300 mg/dL had a mean Lp(a) concentration of 60.1 nmol/L. In subjects without diabetes or obesity, the inverse association of Lp(a)-TG was especially important (p < 0.001). The median Lp(a) was 58.3 nmol/L in those with TG < 300 mg/dL and 22.0 nmol/L if TG > 1000 mg/dL. No association was found between TG and Lp(a) in subjects with diabetes and obesity, nor in subjects with familial hypercholesterolemia. In subjects with multifactorial combined hyperlipemia with TG < 300 mg/dL, Lp(a) was 64.6 nmol/L; in the range of 300-399 mg/dL of TG, Lp(a) decreased to 38. 8 nmol/L, and up to 22.3 nmol/L when TG > 1000 mg/dL.

CONCLUSIONS

Our results show an inverse Lp(a)-TG relationship in TG concentrations > 300 mg/dL in subjects without diabetes, obesity and without familial hypercholesterolemia. Our results suggest that, in those hypertriglyceridemias due to hepatic overproduction of VLDL, the formation of Lp(a) is reduced, unlike those in which the peripheral catabolism of TG-rich lipoproteins is reduced.

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.

Associations of Lipoprotein(a) Level with Cerebral Small Vessel Disease in Patients with Alzheimer's Disease

BACKGROUND

This study aimed to examine the association of lipoprotein(a) [Lp(a)] level with the burden of cerebral small vessel disease (CSVD) in patients with Alzheimer's disease (AD).

METHODS

Data from 111 consecutive patients with AD admitted to Nanjing First Hospital from 2015 to 2022 were retrospectively analyzed in this study. Serum Lp(a) concentrations were grouped into tertiles (T1-T3). Brain magnetic resonance imaging (MRI) was rated for the presence of CSVD, including enlarged perivascular spaces (EPVS), lacunes, white-matter lesions, and cerebral microbleeds (CMBs). The CSVD burden was calculated by summing the scores of each MRI marker at baseline. A binary or ordinal logistic regression model was used to estimate the relationship of serum Lp(a) levels with CSVD burden and each MRI marker.

RESULTS

Patients with higher tertiles of Lp(a) levels were less likely to have any CSVD (T1, 94.6%; T2, 78.4%; T3, 66.2%; p = 0.013). Multivariable analysis found that Lp(a) levels were inversely associated with the presence of CSVD (T2 vs. T1: adjusted odds ratio [aOR] 0.132, 95% confidence interval [CI] 0.018-0.946, p = 0.044; T3 vs. T1: aOR 0.109, 95% CI 0.016-0.737, p = 0.023) and CSVD burden (T3 vs. T1: aOR 0.576, 95% CI 0.362-0.915, p = 0.019). The independent relationship between Lp(a) levels and individual CSVD features was significant for moderate-to-severe EPVS in the centrum semiovale (T2 vs. T1: aOR 0.059, 95% CI 0.006-0.542, p = 0.012; T3 vs. T1: aOR 0.029, 95% CI 0.003-0.273, p = 0.002) and CMBs (T3 vs. T1: aOR 0.144, 95% CI 0.029-0.716, p = 0.018).

CONCLUSIONS

In this study, serum Lp(a) level was inversely associated with CSVD in AD patients.

Association of vitamins, minerals, and lead with lipoprotein(a) in a cross-sectional cohort of US adults

Lipoprotein(a)(Lp[a]) is a low-density lipoprotein-cholesterol (LDL-C)-like particle with potent pro-atherothrombotic properties. The association of Lp(a) with several circulating factors, including vitamins, remains unresolved. We performed an observational analysis using the National Health and Nutrition Examination Survey III cohort, a cohort used to monitor the nutrition status of US-citizens. We used multivariable linear regression to test associations of Lp(a) and LDL-C with levels of serum vitamins and minerals and whole-blood lead. Analyses controlled for factors known to associate with Lp(a) (age, sex, race/ethnicity, statin use, hemoglobin A1c, body mass index, hypertension, diabetes, glomerular filtration rate, alcohol intake, and saturated fat intake). LDL-C was corrected for Lp(a) mass. Multiple sensitivity tests were performed, including considering factors as categorical variables (deficient, normal, elevated). Among 7,662 subjects, Lp(a) correlated (β-coefficient) positively (change per 1 conventional unit increase) with carotenoids (lycopene (0.17(0.06,0.28), p=0.005), lutein (0.19(0.07,0.30), p=0.002), β-cryptoxanthin (0.21(0.05,0.37), p=0.01), β-carotene (0.05(0.02,0.09), p=0.003), and α-carotene (0.15(0.01,0.30), p=0.04)) and lead (0.54(0.03,1.05), p=0.04) levels when tested as continuous variables. LDL-C had similar associations. Lp(a) did not associate with vitamins A, B12, C, or E retinyl esters, folate, RBC-folate, selenium, ferritin, transferrin saturation, or calcium. With factors as categorical variables, Lp(a) but not LDL-C negatively associated with elevated vitamin B12 (-5.41(-9.50, -1.53), p=0.01) and folate (-2.86(-5.09, -0.63), p=0.01). In conclusion, Lp(a) associated similarly to LDL-C when vitamins, minerals, and lead were tested as continuous variables, while only Lp(a) correlated with vitamin B12 and folate when tested as categorical variables. These observations are hypotheses generating and require further studies to determine causality.

Effect of Omega-3 Fatty Acid Supplementation on the Postprandial Metabolism of Apolipoprotein(a) in Familial Hypercholesterolemia

AIM

Lipoprotein(a) (Lp(a)) is a low-density lipoprotein-like particle containing apolipoprotein(a) (apo(a)) that increases the risk of atherosclerotic cardiovascular disease (ASCVD) in familial hypercholesterolemia (FH). Postprandial redistribution of apo(a) protein from Lp(a) to triglyceride-rich lipoproteins (TRLs) may also increase the atherogenicity of TRL particles. Omega-3 fatty acid (ω3FA) supplementation improves postprandial TRL metabolism in FH subjects. However, its effect on postprandial apo(a) metabolism has yet to be investigated.

METHODS

We carried out an 8-week open-label, randomized, crossover trial to test the effect of ω3FA supplementation (4 g/day) on postprandial apo(a) responses in FH patients following ingestion of an oral fat load. Postprandial plasma total and TRL-apo(a) concentrations were measured by liquid chromatography with tandem mass spectrometry, and the corresponding areas under the curve (AUCs) (0-10h) were determined using the trapezium rule.

RESULTS

Compared with no ω3FA treatment, ω3FA supplementation significantly lowered the concentrations of postprandial TRL-apo(a) at 0.5 (-17.9%), 1 (-18.7%), 2 (-32.6%), and 3 h (-19.2%) (P＜0.05 for all). Postprandial TRL-apo(a) AUC was significantly reduced with ω3FA by 14.8% (P＜0.05). By contrast, ω3FA had no significant effect on the total AUCs of apo(a), apoC-III, and apoE (P＞0.05 for all). The decrease in postprandial TRL-apo(a) AUC was significantly associated with changes in the AUC of triglycerides (r=0.600; P＜0.01) and apoB-48 (r=0.616; P＜0.01).

CONCLUSIONS

Supplementation with ω3FA reduces postprandial TRL-apo(a) response to a fat meal in FH patients; this novel metabolic effect of ω3FA may have implications on decreasing the risk of ASCVD in patients with FH, especially in those with elevated plasma triglyceride and Lp(a) concentrations. However, the clinical implications of these metabolic findings require further evaluation in outcome or surrogate endpoint trials.

Diagnosis of Familial Dysbetalipoproteinemia Based on the Lipid Abnormalities Driven by APOE2/E2 Genotype

BACKGROUND

Familial dysbetalipoproteinemia (FDBL) is a monogenic disease due to variants in APOE with a highly variable phenotype. Current diagnostic lipid-based methods have important limitations. The objective is twofold: to define characteristics of dysbetalipoproteinemia (DBL) based on the analysis of APOE in patients from a lipid unit and in a sample from the general population, and to propose a screening algorithm for FDBL.

METHODS

Lipids and APOE genotype from consecutive unrelated subjects from Miguel Servet University Hospital (MSUH) (n 3603), subjects from the general population participants of the Aragon Workers Health Study (AWHS) (n 4981), and selected subjects from external lipid units (Ext) (n 390) were used to define DBL criteria and to train and validate a screening tool.

RESULTS

Thirty-five subjects from MSUH, 21 subjects from AWHS, and 31 subjects from Ext were APOE2/2 homozygous. The combination of non high-density lipoprotein cholesterol (non-HDLc)/apoB 1.7 plus triglycerides/apoB 1.35, in mg/dL (non-HDLc [mmol/L]/apolipoprotein B (apoB) [g/L] 4.4 and triglycerides [mmol/L]/apoB [g/L] 3.5), provided the best diagnostic performance for the identification of subjects with hyperlipidemia and APOE2/2 genotype (sensitivity 100 in the 3 cohorts, and specificity 92.8 [MSUH], 80.9 [AWHS], and 77.6 [Ext]). This improves the performance of previous algorithms. Similar sensitivity and specificity were observed in APOE2/2 subjects receiving lipid-lowering drugs.

CONCLUSIONS

The combination of non-HDLc/apoB and triglycerides/apoB ratios is a valuable tool to diagnose DBL in patients with hyperlipidemia with or without lipid-lowering drugs. FDBL diagnosis requires DBL and the presence of a compatible APOE genotype. Most adult APOE2/2 subjects express DBL, making FDBL as common as familial hypercholesterolemia in the population.

New Horizons: Revival of Lipoprotein (a) as a Risk Factor for Cardiovascular Disease

The status of lipoprotein (a) [Lp(a)] as a cardiovascular risk factor has been resurrected by advances in genetics. Mendelian randomization studies show a causal link of Lp(a) with coronary artery disease (CAD), peripheral artery disease (PAD), and calcific aortic valve stenosis (CAVS). The genetics of Lp(a) is complex and extends beyond the kringle-IV type 2, as it is also dependent on ancestry. The plasma concentration of Lp(a) is determined by the hepatic production of apolipoprotein(a) [apo(a)] component of Lp(a), supporting the use of nucleic acids that inhibit the messenger RNA (mRNA) gene transcript for apo(a). Analytical barriers to measurement of Lp(a) are being addressed using isoform independent assays and a traceable standard. The association of Lp(a) and atherosclerotic cardiovascular disease is higher for myocardial infarction than PAD and CAVS. Increased risk of type 2 diabetes mellitus associated with low Lp(a) levels is perplexing and requires further investigation. The greatest advancement in Lp(a)-lowering therapies is based on using RNA therapeutics that are now being investigated in clinical trials. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition lowers Lp(a) modestly, but whether cardiovascular benefit is independent of low-density lipoprotein lowering remains unclear. Opportunistic and selective testing for Lp(a) is supported by moderate evidence, with the case for universal screening premature. Modification of behavioral and clinical risk factors may be targeted to mitigate Lp(a)-mediated risk of cardiovascular disease. Clinical practice guidelines have been developed to address gaps in care of high Lp(a), but full implementation awaits the findings of clinical outcome trials using RNA-directed therapies currently underway.

Gene-gene interaction detection with deep learning

The extent to which genetic interactions affect observed phenotypes is generally unknown because current interaction detection approaches only consider simple interactions between top SNPs of genes. We introduce an open-source framework for increasing the power of interaction detection by considering all SNPs within a selected set of genes and complex interactions between them, beyond only the currently considered multiplicative relationships. In brief, the relation between SNPs and a phenotype is captured by a neural network, and the interactions are quantified by Shapley scores between hidden nodes, which are gene representations that optimally combine information from the corresponding SNPs. Additionally, we design a permutation procedure tailored for neural networks to assess the significance of interactions, which outperformed existing alternatives on simulated datasets with complex interactions, and in a cholesterol study on the UK Biobank it detected nine interactions which replicated on an independent FINRISK dataset.

Triglyceride Metabolism Modifies Lipoprotein(a) Plasma Concentration

BACKGROUND

Lipoprotein(a) (Lp(a)) is a significant cardiovascular risk factor. Knowing the mechanisms that regulate its concentration can facilitate the development of Lp(a)-lowering drugs. This study analyzes the relationship between triglycerides (TGs) and Lp(a) concentrations, cross-sectionally and longitudinally, and the influence of the number and composition of TG-rich lipoproteins, and the APOE genotype.

METHODS

Data from Aragon Workers Health Study (AWHS) (n = 5467), National Health and Nutrition Examination Survey III phase 2 (n = 3860), and Hospital Universitario Miguel Servet (HUMS) (n = 2079) were used for cross-sectional TG and Lp(a) relationship. Lp(a) intrasubject variation was studied in AWHS participants and HUMS patients with repeated measurements. TG-rich lipoproteins were quantified by nuclear magnetic resonance in a subsample from AWHS. Apolipoproteins B and E were quantified by Luminex in very low-density lipoprotein (VLDL) isolated by ultracentrifugation, from HUMS samples. APOE genotyping was carried in AWHS and HUMS participants. Regression models adjusted for age and sex were used to study the association.

RESULTS

The 3 studies showed an inverse relationship between TG and Lp(a). Increased VLDL number, size, and TG content were associated with significantly lower Lp(a). There was an inverse association between the apoE concentration in VLDL and Lp(a). No significant association was observed for apolipoprotein (apo)B. Subjects carrying the apoE2/E2 genotype had significantly lower levels of Lp(a).

CONCLUSION

Our results show an inverse relationship Lp(a)-TG. Subjects with larger VLDL size have lower Lp(a), and lower values of Lp(a) were present in patients with apoE-rich VLDL and apoE2/E2 subjects. Our results suggest that bigger VLDLs and VLDLs enriched in apoE are inversely involved in Lp(a) plasma concentration.

Lipoprotein (a) in familial hypercholesterolaemia

PURPOSE OF REVIEW

The role of lipoprotein (a) in atherogenesis has been the subject of argument for many years. Evidence that it is raised in familial hypercholesterolaemia has been disputed not least because a mechanism related to low density lipoprotein (LDL) receptor mediated catabolism has been lacking. Whether lipoprotein (a) increases the already raised atherosclerotic cardiovascular disease (ASCVD) risk in familial hypercholesterolaemia is also more dubious than is often stated. We review the evidence in an attempt to provide greater clarity.

RECENT FINDINGS

Lipoprotein (a) levels are raised as a consequence of inheriting familial hypercholesterolaemia. The mechanism for this is likely to involve increased hepatic production, probably mediated by PCSK9 augmented by apolipoprotein E. The extent to which raised lipoprotein (a) contributes to the increased ASCVD risk in familial hypercholesterolaemia remains controversial.Unlike, for example, statins which are effective across the whole spectrum of LDL concentrations, drugs in development to specifically lower lipoprotein (a) are likely to be most effective in people with the highest levels of lipoprotein (a). People with familial hypercholesterolaemia may therefore be in the vanguard of those in whom theses agents should be exhibited.

SUMMARY

Inheritance of familial hypercholesterolaemia undoubtedly increases the likelihood that lipoprotein (a) will be raised. However, in familial hypercholesterolaemia when ASCVD incidence is already greatly increased due to high LDL cholesterol, whether lipoprotein (a) contributes further to this risk cogently needs to be tested with drugs designed to specifically lower lipoprotein (a).

Familial Hypercholesterolemia and Elevated Lipoprotein(a): Cascade Testing and Other Implications for Contextual Models of Care

Elevated lipoprotein(a) [Lp(a)], a predominantly genetic disorder, is a causal risk factor for atherosclerotic cardiovascular disease (ASCVD) and calcific aortic valvular disease, particularly in patients with familial hypercholesterolemia (FH), a Tier I genomic condition. The combination from birth of the cumulative exposure to elevated plasma concentrations of both Lp(a) and low-density lipoprotein is particularly detrimental and explains the enhanced morbidity and mortality risk observed in patients with both conditions. An excellent opportunity to identify at-risk patients with hyper-Lp(a) at increased risk of ASCVD is to test for hyper-Lp(a) during cascade testing for FH. With probands having FH and hyper-Lp(a), the yield of detection of hyper-Lp(a) is 1 individual for every 2.1-2.4 relatives tested, whereas the yield of detection of both conditions is 1 individual for every 3-3.4 relatives tested. In this article, we discuss the incorporation of assessment of Lp(a) in the cascade testing in FH as a feasible and crucial part of models of care for FH. We also propose a simple management tool to help physicians identify and manage elevated Lp(a) in FH, with implications for the care of Lp(a) beyond FH, noting that the clinical use of RNA therapeutics for specifically targeting the overproduction of Lp(a) in at risk patients is still under investigation.

Genetic and Mechanistic Insights into the Modulation of Circulating Lipoprotein (a) Concentration by Apolipoprotein E Isoforms

PURPOSE OF REVIEW

Lipoprotein (a) [Lp(a)] is a highly atherogenic lipoprotein species. A unique feature of Lp(a) is the strong genetic determination of its concentration. The LPA gene is responsible for up to 90% of the variance in Lp(a), but other genes also have an impact.

RECENT FINDINGS

Genome-wide associations studies indicate that the APOE gene, encoding apolipoprotein E (apoE), is the second most important locus modulating Lp(a) concentrations. Population studies clearly show that carriers of the apoE2 variant (ε2) display reduced Lp(a) levels, the lowest concentrations being observed in ε2/ε2 homozygotes. This genotype can lead predisposed adults to develop dysbetalipoproteinemia, a lipid disorder characterized by sharp elevations in cholesterol and triglycerides. However, dysbetalipoproteinemia does not significantly modulate circulating Lp(a). Mechanistically, apoE appears to impair the production but not the catabolism of Lp(a). These observations underline the complexity of Lp(a) metabolism and provide key insights into the pathways governing Lp(a) synthesis and secretion.

Effect of Pelacarsen on Lipoprotein(a) Cholesterol and Corrected Low-Density Lipoprotein Cholesterol

BACKGROUND

Laboratory methods that report low-density lipoprotein cholesterol (LDL-C) include both LDL-C and lipoprotein(a) cholesterol [Lp(a)-C] content.

OBJECTIVES

The purpose of this study was to assess the effect of pelacarsen on directly measured Lp(a)-C and LDL-C corrected for its Lp(a)-C content.

METHODS

The authors evaluated subjects with a history of cardiovascular disease and elevated Lp(a) randomized to 5 groups of cumulative monthly doses of 20-80 mg pelacarsen vs placebo. Direct Lp(a)-C was measured on isolated Lp(a) using LPA4-magnetic beads directed to apolipoprotein(a). LDL-C was reported as: 1) LDL-C as reported by the clinical laboratory; 2) LDL-C_corr = laboratory-reported LDL-C - direct Lp(a)-C; and 3) LDL-C_corrDahlén = laboratory LDL-C - [Lp(a) mass × 0.30] estimated by the Dahlén formula.

RESULTS

The baseline median Lp(a)-C values in the groups ranged from 11.9 to 15.6 mg/dL. Compared with placebo, pelacarsen resulted in dose-dependent decreases in Lp(a)-C (2% vs -29% to -67%; P = 0.001-<0.0001). Baseline laboratory-reported mean LDL-C ranged from 68.5 to 89.5 mg/dL, whereas LDL-C_corr ranged from 55 to 74 mg/dL. Pelacarsen resulted in mean percent/absolute changes of -2% to -19%/-0.7 to -8.0 mg/dL (P = 0.95-0.05) in LDL-C_corr, -7% to -26%/-5.4 to -9.4 mg/dL (P = 0.44-<0.0001) in laboratory-reported LDL-C, and 3.1% to 28.3%/0.1 to 9.5 mg/dL (P = 0.006-0.50) increases in LDL-C_corrDahlén. Total apoB declined by 3%-16% (P = 0.40-<0.0001), but non-Lp(a) apoB was not significantly changed.

CONCLUSIONS

Pelacarsen significantly lowers direct Lp(a)-C and has neutral to mild lowering of LDL-C_corr. In patients with elevated Lp(a), LDL-C_corr provides a more accurate reflection of changes in LDL-C than either laboratory-reported LDL-C or the Dahlén formula.

Lipoprotein(a) as predictor of coronary artery disease and myocardial infarction in a multi-ethnic Asian population

BACKGROUND AND AIMS

The role of Lp(a) in multi-ethnic Asian populations with coronary artery disease (CAD) has not been well established. The aims of this study were (i) to investigate whether Lp(a) is a predictor of CAD, and (ii) amongst patients with CAD, to ascertain whether Lp(a) is a predictor of acute myocardial infarction (AMI) and severity of CAD.

METHODS

We compared three cardiovascular phenotypes from patients recruited at coronary angiography. CAD was defined as ≥50% coronary artery stenosis and subdivided into a group with AMI history (CAD+AMI+) and a group without (CAD+AMI-). Minimal CAD group (CAD-) was defined as normal or <30% coronary artery stenosis and no AMI. The severity of CAD was defined using the modified Gensini score.

RESULTS

We studied 2025 patients comprising 94.5% men and 61.4% of Chinese ethnicity. The median Lp(a) level was highest in CAD+AMI+, followed by CAD+AMI- and CAD- (26.2, 20.1, and 15.8 nmol/L respectively). Similarly, the frequency of patients with Lp(a) ≥120 nmol/L were in the same order (11.8%, 9.1% and 2.4%). Lp(a) levels were highest among Asian Indians, followed by Malays and Chinese patients (p < 0.001). Lp(a) levels and Lp(a) ≥120 nmol/L were significant predictors of CAD (Odds ratio (OR) = 1.12 per 10 nmol/L increment, p < 0.001, and OR = 5.41 p = 0.004 respectively). Among patients with CAD, higher Lp(a) levels were associated with increased AMI risk (OR = 1.02 per 10 nmol/L increment, p = 0.024). Lp(a) ≥120 nmol/L was positively associated with CAD severity (p = 0.020).

CONCLUSIONS

Plasma Lp(a) concentration is a positive predictor of CAD and AMI in a mostly male South East Asian population.

Unravelling lipoprotein metabolism with stable isotopes: tracing the flow

Dysregulated lipoprotein metabolism is a major cause of atherosclerotic cardiovascular disease (ASCVD). Use of stable isotope tracers and compartmental modelling have provided deeper understanding of the mechanisms underlying lipid disorders in patients at high risk of ASCVD, including familial hypercholesterolemia (FH), elevated lipoprotein(a) [Lp(a)] and metabolic syndrome (MetS). In patients with FH, deficiency in low-density lipoprotein (LDL) receptor activity not only impairs the catabolism of LDL, but also induces hepatic overproduction and decreases catabolism of triglyceride-rich lipoproteins (TRLs). Patients with elevated Lp(a) are characterized by increased hepatic secretion of Lp(a) particles. Atherogenic dyslipidemia in MetS patients relates to a combination of overproduction of very-low density lipoprotein-apolipoprotein (apo) B-100, decreased catabolism of apoB-100-containing particles, and increased catabolism of high-density lipoprotein-apoA-I particles, as well as to impaired clearance of TRLs in the postprandial state. Kinetic studies show that weight loss, fish oils, statins and fibrates have complementary modes of action that correct atherogenic dyslipidemia. Defining the kinetic mechanisms of action of proprotein convertase subtilisin/kexin type 9 and angiopoietin-like 3 inhibitors on lipid and lipoprotein mechanism in dyslipidemic subjects will further our understanding of these therapies in decreasing the development of ASCVD. "Everything changes but change itself. Everything flows and nothing remains the same... You cannot step twice into the same river, for other waters and yet others go flowing ever on." Heraclitus (c.535- c. 475 BCE).

Longitudinal Assessment of Lipoprotein(a) Levels in Perinatally HIV-Infected Children and Adolescents

HIV is an independent risk factor of cardiovascular disease (CVD); therefore, perinatally HIV-infected (PHIV) children potentially have a greater CVD risk at older age. Lipoprotein(a) (Lp(a)) is an established risk factor for CVD in the general population. To evaluate a potential increased CVD risk for PHIV children, we determined their lipid profiles including Lp(a). In the first substudy, we assessed the lipid profiles of 36 PHIV children visiting the outpatient clinic in Amsterdam between 2012 and 2020. In the second substudy, we enrolled 21 PHIV adolescents and 23 controls matched for age, sex and ethnic background on two occasions with a mean follow-up time of 4.6 years. We assessed trends of lipid profiles and their determinants, including patient and disease characteristics, using mixed models. In the first substudy, the majority of PHIV children were Black (92%) with a median age of 8.0y (5.7–10.8) at first assessment. Persistent elevated Lp(a) levels were present in 21/36 (58%) children (median: 374 mg/L (209–747); cut off = 300). In the second substudy, the median age of PHIV adolescents was 17.5y (15.5–20.7) and of matched controls 16.4y (15.8–19.5) at the second assessment. We found comparable lipid profiles between groups. In both studies, increases in LDL-cholesterol and total cholesterol were associated with higher Lp(a) levels. A majority of PHIV children and adolescents exhibited elevated Lp(a) levels, probably associated with ethnic background. Nonetheless, these elevated Lp(a) levels may additionally contribute to an increased CVD risk.

Elevated Lipoprotein(a): Background, Current Insights and Future Potential Therapies

Lipoprotein(a) forms a subfraction of the lipid profile and is characterized by the addition of apolipprotein(a) (apo(a)) to apoB100 derived particles. Its levels are mostly genetically determined inversely related to the number of protein domain (kringle) repeats in apo(a). In epidemiological studies, it shows consistent association with cardiovascular disease (CVD) and most recently with extent of aortic stenosis. Issues with standardizing the measurement of Lp(a) are being resolved and consensus statements favor its measurement in patients at high risk of, or with family histories of CVD events. Major lipid-lowering therapies such as statin, fibrates, and ezetimibe have little effect on Lp(a) levels. Therapies such as niacin or cholesterol ester transfer protein (CETP) inhibitors lower Lp(a) as well as reducing other lipid-related risk factors but have failed to clearly reduce CVD events. Proprotein convertase subtilisin kexin-9 (PCSK9) inhibitors reduce cholesterol and Lp(a) as well as reducing CVD events. New antisense therapies specifically targeting apo(a) and hence Lp(a) have greater and more specific effects and will help clarify the extent to which intervention in Lp(a) levels will reduce CVD events.

Lipoprotein(a): Knowns, unknowns and uncertainties

Over the last 10 years, there have been advances on several aspects of lipoprotein(a) which are reviewed in the present article. Since the standard immunoassays for measuring lipoprotein(a) are not fully apo(a) isoform-insensitive, the application of an LC-MS/MS method for assaying molar concentrations of lipoprotein(a) has been advocated. Genome wide association, epidemiological, and clinical studies have established high lipoprotein(a) as a causal risk factor for atherosclerotic cardiovascular diseases (ASCVD). However, the relative importance of molar concentration, apo(a) isoform size or variants within the LPA gene is still controversial. Lipoprotein(a)-raising single nucleotide polymorphisms has not been shown to add on value in predicting ASCVD beyond lipoprotein(a) concentrations. Although hyperlipoproteinemia(a) represents an important confounder in the diagnosis of familial hypercholesterolemia (FH), it enhances the risk of ASCVD in these patients. Thus, identification of new cases of hyperlipoproteinemia(a) during cascade testing can increase the identification of high-risk individuals. However, it remains unclear whether FH itself increases lipoprotein(a). The ASCVD risk associated with lipoprotein(a) seems to follow a linear gradient across the distribution, regardless of racial subgroups and other risk factors. The inverse association with the risk of developing type 2 diabetes needs consideration as effective lipoprotein(a) lowering therapies are progressing towards the market. Considering that Mendelian randomization analyses have identified the degree of lipoprotein(a)-lowering that is required to achieve ASCVD benefit, the findings of the ongoing outcome trial with pelacarsen will clarify whether dramatically lowering lipoprotein(a) levels can reduce the risk of ASCVD.

Lipoprotein(a) in hereditary hypercholesterolemia: Influence of the genetic cause, defective gene and type of mutation

BACKGROUND AND AIMS

Lipoprotein(a) [Lp(a)] concentration in heterozygous familial hypercholesterolemia (heFH) is not well established. Whether the genetic defect responsible for heFH plays a role in Lp(a) concentration is unknown. We aimed to compare Lp(a) in controls from a healthy population, in genetically diagnosed heFH and mutation-negative hypercholesterolemia subjects, and to assess the influence on Lp(a) of the genetic defect responsible for heFH.

METHODS

We conducted a cross-sectional study, performed in a lipid clinic in Spain. We studied adults with suspected heFH and a genetic study of FH genes (LDLR, APOB, APOE and PCSK9) and controls from de Aragon Workers' Health Study. HeFH patients from the Dyslipidemia Registry of the Spanish Atherosclerosis Society (SEA) were used as validation cohort.

RESULTS

Adjusted geometric means (95% confidence interval) of Lp(a) in controls (n = 1059), heFH (n = 500), and mutation-negative subjects (n = 860) were 14.9 mg/dL (13.6, 16.4), 21.9 mg/dL (18.1, 25.6) and 37.4 mg/dL (33.3, 42.1), p < 0.001 in all comparisons. Among heFH subjects, APOB-dependent FH showed the highest Lp(a), 36.5 mg/dL (22.0, 60.8), followed by LDLR-dependent FH, 21.7 mg/dL (17.9, 26.4). These differences were also observed in heFH from the SEA cohort. The number of plasminogen-like kringle IV type-2 repeats of LPA, the hypercholesterolemia polygenic score or LDLc concentration did not explain these differences. In LDLR-dependent FH, Lp(a) levels were not different depending on the affected protein domain.

CONCLUSIONS

Lp(a) is elevated in mutation-negative subjects and in heFH. The concentration of Lp(a) in heFH varies in relation to the responsible gene. Higher Lp(a) in heFH is not explained by their higher LDLc.

The size of apolipoprotein (a) is an independent determinant of the reduction in lipoprotein (a) induced by PCSK9 inhibitors

AIMS

Lipoprotein (a) [Lp(a)] is a lipoprotein species causatively associated with atherosclerosis. Unlike statins, PCSK9 inhibitors (PCSK9i) reduce Lp(a), but this reduction is highly variable. Levels of Lp(a) are chiefly governed by the size of its signature protein, apolipoprotein (a) [apo(a)]. Whether this parameter determines some of the reduction in Lp(a) induced by PCSK9i remains unknown. We aimed to investigate if the Lp(a) lowering efficacy of PCSK9i is modulated by the size of apo(a), which is genetically determined by the variable number of KIV domains present on that protein.

METHODS AND RESULTS

The levels of Lp(a) and the size of apo(a) were assessed in plasma samples from 268 patients before and after treatment with PCSK9i. Patients were recruited at the Outpatient Lipid Clinic of the Charité Hospital (Berlin) between 2015 and 2020. They were hypercholesterolemic at very high CVD risk with LDL-cholesterol levels above therapeutic targets despite maximally tolerated lipid-lowering therapy. Patients received either Alirocumab (75 or 150 mg) or Evolocumab (140 mg) every 2 weeks. Apo(a), apoB100, and apoE concentrations as well as apoE major isoforms were determined by liquid chromatography high-resolution mass spectrometry. Apo(a) isoforms sizes were determined by Western Blot. PCSK9i sharply reduced LDL-cholesterol (-57%), apoB100 (-47%) and Lp(a) (-36%). There was a positive correlation between the size of apo(a) and the relative reduction in Lp(a) induced by PCSK9i (r = 0.363, p = 0.0001). The strength of this association remained unaltered after adjustment for baseline Lp(a) levels and all other potential confounding factors. In patients with two detectable apo(a) isoforms, there was also a positive correlation between the size of apo(a) and the reduction in Lp(a), separately for the smaller (r = 0.350, p = 0.0001) and larger (r = 0.324, p = 0.0003) isoforms. The relative contribution of the larger isoform to the total concentration of apo(a) was reduced from 29% to 15% (p < 0.0001).

CONCLUSIONS

The size of apo(a) is an independent determinant of the response to PCSK9i. Each additional kringle domain is associated with a 3% additional reduction in Lp(a). This explains in part the variable efficacy of PCSK9i and allows to identify patients who will benefit most from these therapies in terms of Lp(a) lowering.

TRANSLATIONAL PERSPECTIVE

Unlike statins, PCSK9 inhibitors reduce the circulating levels of the highly atherogenic Lipoprotein (a). The underlying mechanism remains a matter of considerable debate. The size of apo(a), the signature protein of Lp(a), is extremely variable (300 to more than 800 kDa) and depends on its number of kringle domains. We now show that each increase in apo(a) size by one kringle domain is associated with a 3% additional reduction in Lp(a) following PCSK9i treatment and that apo(a) size polymorphism is an independent predictor of the reduction in Lp(a) induced by these drugs. In an era of personalized medicine, this allows to identify patients who will benefit most from PCSK9i in terms of Lp(a) lowering.

APOE gene variants in primary dyslipidemia

Apolipoprotein E (apoE) is a major apolipoprotein involved in lipoprotein metabolism. It is a polymorphic protein and different isoforms are associated with variations in lipid and lipoprotein levels and thus cardiovascular risk. The isoform apoE4 is associated with an increase in LDL-cholesterol levels and thus a higher cardiovascular risk compared to apoE3. Whereas, apoE2 is associated with a mild decrease in LDL-cholesterol levels. In the presence of other risk factors, apoE2 homozygotes could develop type III hyperlipoproteinemia (familial dysbetalipoproteinemia or FD), an atherogenic disorder characterized by an accumulation of remnants of triglyceride-rich lipoproteins. Several rare APOE gene variants were reported in different types of dyslipidemias including FD, familial combined hyperlipidemia (FCH), lipoprotein glomerulopathy and bona fide autosomal dominant hypercholesterolemia (ADH). ADH is characterized by elevated LDL-cholesterol levels leading to coronary heart disease, and due to molecular alterations in three main genes: LDLR, APOB and PCSK9. The identification of the APOE-p.Leu167del variant as the causative molecular element in two different ADH families, paved the way to considering APOE as a candidate gene for ADH. Due to non mendelian interacting factors, common genetic and environmental factors and perhaps epigenetics, clinical presentation of lipid disorders associated with APOE variants often strongly overlap. More studies are needed to determine the spectrum of APOE implication in each of the diseases, notably ADH, in order to improve clinical and genetic diagnosis, prognosis and patient management. The purpose of this review is to comment on these APOE variants and on the molecular and clinical overlaps between dyslipidemias.

Alzheimer's Disease Susceptibility Gene Apolipoprotein E (APOE) and Blood Biomarkers in UK Biobank (N = 395,769)

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative condition where the underlying etiology is still unclear. Investigating the potential influence of apolipoprotein E (APOE), a major genetic risk factor, on common blood biomarkers could provide a greater understanding of the mechanisms of AD and dementia risk.

OBJECTIVE

Our objective was to conduct the largest (to date) single-protocol investigation of blood biomarkers in the context of APOE genotype, in UK Biobank.

METHODS

After quality control and exclusions, data on 395,769 participants of White European ancestry were available for analysis. Linear regressions were used to test potential associations between APOE genotypes and biomarkers.

RESULTS

Several biomarkers significantly associated with APOEɛ4 'risk' and ɛ2 'protective' genotypes (versus neutral ɛ3/ɛ3). Most associations supported previous data: for example, ɛ4 genotype was associated with elevated low-density lipoprotein cholesterol (LDL) (standardized beta [b] = 0.150 standard deviations [SDs] per allele, p < 0.001) and ɛ2 with lower LDL (b = -0.456 SDs, p < 0.001). There were however instances of associations found in unexpected directions: e.g., ɛ4 and increased insulin-like growth factor (IGF-1) (b = 0.017, p < 0.001) where lower levels have been previously suggested as an AD risk factor.

CONCLUSION

These findings highlight biomarker differences in non-demented people at genetic risk for dementia. The evidence herein supports previous hypotheses of involvement from cardiometabolic and neuroinflammatory pathways.

The effects of eight serum lipid biomarkers on age-related macular degeneration risk: a Mendelian randomization study

BACKGROUND

Age-related macular degeneration (AMD) is a leading cause of vision loss. Whereas lipids have been studied extensively to understand their effects on cardiovascular diseases, their relationship with AMD remains unclear.

METHODS

Two-sample Mendelian randomization (MR) analyses were performed to systematically evaluate the causal relationships between eight serum lipid biomarkers, consisting of apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), total cholesterol (CHOL), high-density lipoprotein cholesterol (HDL-C), direct low-density lipoprotein cholesterol (LDL-C), lipoprotein A [Lp(a)], triglycerides (TG) and non-HDL cholesterol (non-HDL-C), and the risk of different AMD stages and subtypes. We derived 64-407 genetic instruments for eight serum lipid biomarkers in 419 649 participants of European descent from the UK Biobank cohort. We conducted genome-wide association studies (GWAS) for 12 711 advanced AMD cases [8544 choroidal neovascularization (CNV) and 2656 geographic atrophy (GA) specific AMD subtypes] and 5336 intermediate AMD cases with 14 590 controls of European descent from the International AMD Genomics Consortium.

RESULTS

Higher genetically predicted HDL-C and ApoA1 levels increased the risk of all AMD subtypes. LDL-C, ApoB, CHOL and non-HDL-C levels were associated with decreased risk of intermediate and GA AMD but not with CNV. Genetically predicted TG levels were associated with decreased risk of different AMD subtypes. Sensitivity analyses revealed no evidence for directional pleiotropy effects. In our multivariable MR analyses, adjusting for the effects of correlated lipid biomarkers yielded similar results.

CONCLUSION

These results suggest the role of lipid metabolism in drusen formation and particularly in AMD development at the early and intermediate stages. Mechanistic studies are warranted to investigate the utility of lipid pathways for therapeutic treatment in preventing AMD.

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.

Genome-Wide Association Study Highlights APOH as a Novel Locus for Lipoprotein(a) Levels-Brief Report

OBJECTIVE

Lp(a) (lipoprotein[a]) is an independent risk factor for cardiovascular diseases and plasma levels are primarily determined by variation at the LPA locus. We performed a genome-wide association study in the UK Biobank to determine whether additional loci influence Lp(a) levels. Approach and Results: We included 293 274 White British individuals in the discovery analysis. Approximately 93 095 623 variants were tested for association with natural log-transformed Lp(a) levels using linear regression models adjusted for age, sex, genotype batch, and 20 principal components of genetic ancestry. After quality control, 131 independent variants were associated at genome-wide significance (P≤5×10-8). In addition to validating previous associations at LPA, APOE, and CETP, we identified a novel variant at the APOH locus, encoding β2GPI (beta2-glycoprotein I). The APOH variant rs8178824 was associated with increased Lp(a) levels (β [95% CI] [ln nmol/L], 0.064 [0.047-0.081]; P=2.8×10-13) and demonstrated a stronger effect after adjustment for variation at the LPA locus (β [95% CI] [ln nmol/L], 0.089 [0.076-0.10]; P=3.8×10-42). This association was replicated in a meta-analysis of 5465 European-ancestry individuals from the Framingham Offspring Study and Multi-Ethnic Study of Atherosclerosis (β [95% CI] [ln mg/dL], 0.16 [0.044-0.28]; P=0.0071).

CONCLUSIONS

In a large-scale genome-wide association study of Lp(a) levels, we identified APOH as a novel locus for Lp(a) in individuals of European ancestry. Additional studies are needed to determine the precise role of β2GPI in influencing Lp(a) levels as well as its potential as a therapeutic target.

Low-Density Lipoprotein Cholesterol Corrected for Lipoprotein(a) Cholesterol, Risk Thresholds, and Cardiovascular Events

Background Conventional "low-density lipoprotein cholesterol (LDL-C)" assays measure cholesterol content in both low-density lipoprotein and lipoprotein(a) particles. To clarify the consequences of this methodological limitation for clinical care, our study aimed to compare associations of "LDL-C" and corrected LDL-C with risk of cardiovascular disease and to assess the impact of this correction on the classification of patients into guideline-recommended LDL-C categories. Methods and Results Lipoprotein(a) cholesterol content was estimated as 30% of lipoprotein(a) mass and subtracted from "LDL-C" to obtain corrected LDL-C values (LDL-Ccorr30). Hazard ratios for cardiovascular disease (defined as coronary heart disease, stroke, or coronary revascularization) were quantified by individual-patient-data meta-analysis of 5 statin landmark trials from the Lipoprotein(a) Studies Collaboration (18 043 patients; 5390 events; 4.7 years median follow-up). When comparing top versus bottom quartiles, the multivariable-adjusted hazard ratio for cardiovascular disease was significant for "LDL-C" (1.17; 95% CI, 1.05-1.31; P=0.005) but not for LDL-Ccorr30 (1.07; 95% CI, 0.93-1.22; P=0.362). In a routine laboratory database involving 531 144 patients, reclassification of patients across guideline-recommended LDL-C categories when using LDL-Ccorr30 was assessed. In "LDL-C" categories of 70 to <100, 100 to <130, 130 to <190, and ≥190 mg/dL, significant proportions (95% CI) of participants were reassigned to lower LDL-C categories when LDL-Ccorr30 was used: 30.2% (30.0%-30.4%), 35.1% (34.9%-35.4%), 32.9% (32.6%-33.1%), and 41.1% (40.0%-42.2%), respectively. Conclusions "LDL-C" was associated with incident cardiovascular disease only when lipoprotein(a) cholesterol content was included in its measurement. Refinement in techniques to accurately measure LDL-C, particularly in patients with elevated lipoprotein(a) levels, is warranted to assign risk to the responsible lipoproteins.

Cholesterol-conjugated bovine serum albumin nanoparticles as a tamoxifen tumor-targeted delivery system

In the present study, we introduced cholesterol (CLO)-conjugated bovine serum albumin nanoparticles (BSA NPs) as a new system for indirect targeting drug delivery. Tamoxifen, as an anticancer drug, was loaded on BSA NPs (BSA-TAX NPs); CLO was then conjugated to the BSA-TAX NPs surface for the targeted delivery of NPs system, by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxy succinimide carbodiimide chemistry (CLO-BSA-TAX NPs). The physicochemical properties, toxicity, in vitro, and in vivo biocompatibility of the BSA NPs system were characterized on cancer cell lines (4T1). The results revealed that the BSA NPs system has a regular spherical shape and negative zeta-potential values. The drug release of BSA NPs system has shown controlled and pH-dependent drug release behavior. BSA NPs system was biocompatible but it was potentially toxic on the cancer cell line. The CLO-BSA-TAX NPs exhibited higher toxicity against cancer cell lines than other NPs formulation (BSA NPs and BSA-TAX NPs). It can be concluded that the CLO, as an indirect targeting agent, enhances the toxicity and specificity of NPs system on cancer cell lines. It could potentially be suitable approaches to targeting the tumors in clinical cancer therapy.

Lipoprotein(a) and Its Potential Association with Thrombosis and Inflammation in COVID-19: a Testable Hypothesis

PURPOSE OF REVIEW

The COVID-19 pandemic has infected over > 11 million as of today people worldwide and is associated with significant cardiovascular manifestations, particularly in subjects with preexisting comorbidities and cardiovascular risk factors. Recently, a predisposition for arterial and venous thromboses has been reported in COVID-19 infection. We hypothesize that besides conventional risk factors, subjects with elevated lipoprotein(a) (Lp(a)) may have a particularly high risk of developing cardiovascular complications.

RECENT FINDINGS

The Lp(a) molecule has the propensity for inhibiting endogenous fibrinolysis through its apolipoprotein(a) component and for enhancing proinflammatory effects such as through its content of oxidized phospholipids. The LPA gene contains an interleukin-6 (IL-6) response element that may induce an acute phase-type increase in Lp(a) levels following a cytokine storm from COVID-19. Thus, subjects with either baseline elevated Lp(a) or those who have an increase following COVID-19 infection, or both, may be at very high risk of developing thromboses. Elevated Lp(a) may also lead to acute destabilization of preexisting but quiescent atherosclerotic plaques, which might induce acute myocardial infarction and stroke. Ongoing studies with IL-6 antagonists may be informative in understanding this relationship, and registries are being initiated to measure Lp(a) in subjects infected with COVID-19. If indeed an association is suggestive of being causal, consideration can be given to systematic testing of Lp(a) and prophylactic systemic anticoagulation in infected inpatients. Therapeutic lipid apheresis and pharmacotherapy for the reduction of Lp(a) levels may minimize thrombogenic potential and proinflammatory effects. We propose studies to test the hypothesis that Lp(a) may contribute to cardiovascular complications of COVID-19.

Sleep Duration, Lipid Profile and Insulin Resistance: Potential Role of Lipoprotein(a)

Lipoprotein (a) (Lp(a)) is considered a genetic factor for cardiovascular disease playing an important role in atherogenesis and thrombosis, but the evidence about its association with sleep duration is controversial. We evaluated the relation between self-reported sleep duration and Lp(a). Among 1600 participants of the population-based sample, we selected 1427 subjects without previously known cardiovascular events, who answered the questions about their sleep duration; had valid lipid profile results (total cholesterol, low- and high-density lipoproteins, Lp(a), apolipoprotein AI (ApoAI), ApoB, and ApoB/ApoAI); and did not take lipid-lowering drugs (mean age 46 ± 12 years). We performed a structured interview, which included questions about lifestyle, medical history, complaints, and sleep duration (How long have you been sleeping per night during the last month?). Sleep duration was classified as follows: <6 h/night-short, 6-9 h/night-normal, and ≥10 h/night-long. Overall, 73 respondents (5.2%) were short-sleepers and 69 (4.8%) long-sleepers. Males were slightly more prevalent among short-sleepers. The groups matched by age, body mass index, blood pressure, diabetes mellitus, and hypertension rate. Short-sleepers had lower rates of high total cholesterol (≥5.0 mmol/L), lower Lp(a) levels and lower rates of increased Lp(a) ≥0.5 g/L, and higher insulin and insulin resistance (assessed by the homeostatic model assessment for insulin resistance (HOMA-IR)). ApoAI, ApoB, their ratio, and other lab tests were similar in the groups. The multinomial logistic regression demonstrated that only the short sleep duration was independently (odds ratio (OR) 0.29, 95% confidence interval (CI) (0.09-0.91), p = 0.033) associated with Lp(a) (χ2 = 41.58, p = 0.003). Other influencing factors were smoking and HOMA-IR. Such an association was not found for long-sleepers. In conclusion, a short-sleep duration is associated with Lp(a). The latter might mediate the higher insulin resistance and higher cardiometabolic risks in short-sleepers.

A genome-wide analysis of DNA methylation identifies a novel association signal for Lp(a) concentrations in the LPA promoter

Lipoprotein(a) [Lp(a)] is a major cardiovascular risk factor, which is largely genetically determined by one major gene locus, the LPA gene. Many aspects of the transcriptional regulation of LPA are poorly understood and the role of epigenetics has not been addressed yet. Therefore, we conducted an epigenome-wide analysis of DNA methylation on Lp(a) levels in two population-based studies (total n = 2208). We identified a CpG site in the LPA promoter which was significantly associated with Lp(a) concentrations. Surprisingly, the identified CpG site was found to overlap the SNP rs76735376. We genotyped this SNP de-novo in three studies (total n = 7512). The minor allele of rs76735376 (1.1% minor allele frequency) was associated with increased Lp(a) values (p = 1.01e-59) and explained 3.5% of the variation of Lp(a). Statistical mediation analysis showed that the effect on Lp(a) is rather originating from the base change itself and is not mediated by DNA methylation levels. This finding is supported by eQTL data from 208 liver tissue samples from the GTEx project, which shows a significant association of the rs76735376 minor allele with increased LPA expression. To evaluate, whether the association signal at rs76735376 may actually be derived from a stronger eQTL signal in LD with this SNP, eQTL association results of all correlated SNPs (r2≥0.1) were integrated with genetic association results. This analysis pinpointed to rs10455872 as the potential trigger of the effect of rs76735376. Furthermore, both SNPs coincide with short apo(a) isoforms. Adjusting for both, rs10455872 and the apo(a) isoforms diminished the effect size of rs76735376 to 5.38 mg/dL (p = 0.0463). This indicates that the effect of rs76735376 can be explained by both an independent effect of the SNP and a strong correlation with rs10455872 and apo(a) isoforms.

Relationship Between Low-Density Lipoprotein Cholesterol and Lipoprotein(a) Lowering in Response to PCSK9 Inhibition With Evolocumab

Background

Beyond their potent LDL (low‐density lipoprotein) cholesterol (LDL‐C)–lowering efficacy (50–60%), PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitors also reduce Lp(a) (lipoprotein[a]) levels by 25% to 30%, suggesting a 2:1 response ratio. We aimed to characterize the relationship between LDL‐C and Lp(a) lowering by evolocumab, a PCSK9 inhibitor, in a large clinical trial population and to determine the prevalence of concordant/discordant LDL‐C and Lp(a) responses to PCSK9 inhibition.

Methods and Results

Data were analyzed from 4 randomized, 12‐week, multicenter, phase 3 evolocumab trials. Patients with familial hypercholesterolemia, nonfamilial hypercholesterolemia, or statin intolerance participated in the trials. The main measure was the degree of concordance or discordance of LDL‐C and Lp(a) in response to PCSK9 inhibition; concordant response was defined as LDL‐C reduction >35% and Lp(a) reduction >10%. The study cohort comprised 895 patients (438 female; median age: 59.0 years [interquartile range: 51–66 years]). Baseline mean level of LDL‐C was 133.6 mg/dL (SE: 1.7) and median Lp(a) level was 46.4 mg/dL (interquartile range: 18.4–82.4 mg/dL). A discordant response was observed in 165 (19.7%) patients. With these cutoffs, the prevalence of discordance was higher when considering baseline Lp(a) concentrations >30 mg/dL (26.5%) or >50 mg/dL (28.6%).

Conclusions

We demonstrate high prevalence of discordance in LDL‐C and Lp(a) reduction in response to evolocumab, particularly when considering higher baseline Lp(a) concentrations, indicating the possibility of alternative pathways beyond LDLR (LDL receptor)–mediated clearance involved in Lp(a) reduction by evolocumab.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifiers: NCT01763827, NCT01763866, NCT01763905, NCT01763918.

See Editorial by Nestel

VLDL (Very-Low-Density Lipoprotein)-Apo E (Apolipoprotein E) May Influence Lp(a) (Lipoprotein [a]) Synthesis or Assembly

Objective:

To clarify the association between PCSK9 (proprotein convertase subtilisin/kexin type 9) and Lp(a) (lipoprotein [a]), we studied Lp(a) kinetics in patients with loss-of-function and gain-of-function PCSK9 mutations and in patients in whom extended-release niacin reduced Lp(a) and PCSK9 concentrations.

Approach and Results:

Six healthy controls, 9 heterozygous patients with familial hypercholesterolemia (5 with low-density lipoprotein receptor [ LDLR ] mutations and 4 with PCSK9 gain-of-function mutations) and 3 patients with heterozygous dominant-negative PCSK9 loss-of-function mutations were included in the preliminary study. Eight patients were enrolled in a second study assessing the effects of 2 g/day extended-release niacin. Apolipoprotein kinetics in VLDL (very-low-density lipoprotein), LDL (low-density lipoprotein), and Lp(a) were studied using stable isotope techniques. Plasma Lp(a) concentrations were increased in PCSK9 -gain-of-function and familial hypercholesterolemia- LDLR groups compared with controls and PCSK9 -loss-of-function groups (14±12 versus 5±4 mg/dL; P =0.04), but no change was observed in Lp(a) fractional catabolic rate. Subjects with PCSK9 -loss-of-function mutations displayed reduced apoE (apolipoprotein E) concentrations associated with a VLDL-apoE absolute production rate reduction. Lp(a) and VLDL-apoE absolute production rates were correlated ( r =0.50; P <0.05). ApoE-to-apolipoprotein (a) molar ratios in Lp(a) increased with plasma Lp(a) ( r =0.96; P <0.001) but not with PCSK9 levels. Extended-release niacin-induced reductions in Lp(a) and VLDL-apoE absolute production rate were correlated ( r =0.83; P =0.015). In contrast, PCSK9 reduction (−35%; P =0.008) was only correlated with that of VLDL-apoE absolute production rate ( r =0.79; P =0.028).

Conclusions:

VLDL-apoE production could determine Lp(a) production and/or assembly. As PCSK9 inhibitors reduce plasma apoE and Lp(a) concentrations, apoE could be the link between PCSK9 and Lp(a).

Cardiovascular risk factors in patients with premature cardiovascular events attending the University of Dresden Lipid Clinic

OBJECTIVES

Despite improved treatment, premature cardiovascular (CV) events remain a major health problem. Aim of this study was to evaluate the patterns of risk factors in patients with premature CV events.

METHODS

CV risk factors (CVRF) were evaluated in 130 patients with a history of CV events (myocardial infarction, stroke, limb ischemia, stent and bypass intervention in any vessel bed) under 50 years of age attending our lipid clinic. Patients were also stratified according to their Lp(a) concentrations: group 1: 0-45 nmol/l (<18 mg/dl); group 2: >45-120 nmol/l (>18-50 mg/dl); group 3: >120 nmol/l (>50 mg/dl).

RESULTS

The most common risk factors in our patients were male sex (75%), current (61%) and previous smoking (9%), arterial hypertension (70%), and a positive family history of early CV events (54%) and hyperlipidemia (69%). Only 27% had a BMI >30 kg/m² and 14% had diabetes mellitus. 69% of patients with premature CV disease (CVD) showed Lp(a) levels > 120 nmol/l (>50 mg/dl). Patients with the highest Lp(a) showed a tendency of more frequent positive family histories of hyperlipidemia. They had experienced their first CV event on average 3 years earlier than those with low Lp(a). CV events predominantly involved coronary arteries. 85% of patients experienced at least one coronary event.

CONCLUSION

In patients with premature CV disease male sex, smoking, hypertension, a positive family history and elevated Lp(a) are the most important CV risk factors. Lp(a) should be considered in the management of young patients with CV disease.

Molecular, Population, and Clinical Aspects of Lipoprotein(a): A Bridge Too Far?

There is now significant evidence to support an independent causal role for lipoprotein(a) (Lp(a)) as a risk factor for atherosclerotic cardiovascular disease. Plasma Lp(a) concentrations are predominantly determined by genetic factors. However, research into Lp(a) has been hampered by incomplete understanding of its metabolism and proatherogeneic properties and by a lack of suitable animal models. Furthermore, a lack of standardized assays to measure Lp(a) and no universal consensus on optimal plasma levels remain significant obstacles. In addition, there are currently no approved specific therapies that target and lower elevated plasma Lp(a), although there are recent but limited clinical outcome data suggesting benefits of such reduction. Despite this, international guidelines now recognize elevated Lp(a) as a risk enhancing factor for risk reclassification. This review summarises the current literature on Lp(a), including its discovery and recognition as an atherosclerotic cardiovascular disease risk factor, attempts to standardise analytical measurement, interpopulation studies, and emerging therapies for lowering elevated Lp(a) levels.

Elevated Lipoprotein(a) in Perinatally HIV-Infected Children Compared With Healthy Ethnicity-Matched Controls

Background

HIV-associated cardiovascular disease (CVD) risk in combination antiretroviral therapy (cART)-treated perinatally HIV-infected patients (PHIV+) remains unknown due to the young age of this population. Lipoprotein(a) (Lp(a)) has been established as an independent causal risk factor for CVD in the general population but has not been well established in the population of PHIV+.

Methods

We cross-sectionally compared lipid profiles, including nonfasting Lp(a), together with total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides between 35 cART-treated PHIV+ children aged 8-18 years and 37 controls who were matched for age, sex, ethnicity, and socioeconomic status. We explored associations between Lp(a) and disease- and treatment-related factors (inflammation, monocyte activation, and vascular), biomarkers, and neuroimaging outcomes using linear regression models.

Results

PHIV+ children had significantly higher levels of Lp(a) compared with controls (median, 43.6 [21.6-82.4] vs 21.8 [16.8-46.6] mg/dL; P = .033). Other lipid levels were comparable between groups. Additional assessment of apolipoprotein B, apolipoprotein CIII, apolipoprotein E, and APOE genotype revealed no significant differences. Higher Lp(a) levels were associated with higher plasma apoB levels and with lower monocyte chemoattractant protein-1 and TG levels in PHIV+ children. Lp(a) was not associated with HIV- or cART-related variables or with neuroimaging outcomes.

Conclusions

cART-treated PHIV+ children appear to have higher levels of Lp(a) compared with ethnicity-matched controls, which may implicate higher CVD risk in this population. Future research should focus on the association between Lp(a) and (sub)clinical CVD measurements in cART-treated PHIV+ patients.

Dutch Trial Register number

NRT4074.

NHLBI Working Group Recommendations to Reduce Lipoprotein(a)-Mediated Risk of Cardiovascular Disease and Aortic Stenosis

Pathophysiological, epidemiological, and genetic studies provide strong evidence that lipoprotein(a) [Lp(a)] is a causal mediator of cardiovascular disease (CVD) and calcific aortic valve disease (CAVD). Specific therapies to address Lp(a)-mediated CVD and CAVD are in clinical development. Due to knowledge gaps, the National Heart, Lung, and Blood Institute organized a working group that identified challenges in fully understanding the role of Lp(a) in CVD/CAVD. These included the lack of research funding, inadequate experimental models, lack of globally standardized Lp(a) assays, and inadequate understanding of the mechanisms underlying current drug therapies on Lp(a) levels. Specific recommendations were provided to facilitate basic, mechanistic, preclinical, and clinical research on Lp(a); foster collaborative research and resource sharing; leverage expertise of different groups and centers with complementary skills; and use existing National Heart, Lung, and Blood Institute resources. Concerted efforts to understand Lp(a) pathophysiology, together with diagnostic and therapeutic advances, are required to reduce Lp(a)-mediated risk of CVD and CAVD.

Screening a Resource of Recombinant Protein Fragments for Targeted Proteomics

The availability of proteomics resources hosting protein and peptide standards, as well as the data describing their analytical performances, will continue to enhance our current capabilities to develop targeted proteomics methods for quantitative biology. This study describes the analysis of a resource of 26,840 individually purified recombinant protein fragments corresponding to more than 16,000 human protein-coding genes. The resource was screened to identify proteotypic peptides suitable for targeted proteomics efforts, and we report LC-MS/MS assay coordinates for more than 25,000 proteotypic peptides, corresponding to more than 10,000 unique proteins. Additionally, peptide formation and digestion kinetics were, for a subset of the standards, monitored using a time-course protocol involving parallel digestion of isotope-labeled recombinant protein standards and endogenous human plasma proteins. We show that the strategy by adding isotope-labeled recombinant proteins before trypsin digestion enables short digestion protocols (≤60 min) with robust quantitative precision. In a proof-of-concept study, we quantified 23 proteins in human plasma using assay parameters defined in our study and used the standards to describe distinct clusters of individuals linked to different levels of LPA, APOE, SERPINA5, and TFRC. In summary, we describe the use and utility of a resource of recombinant proteins to identify proteotypic peptides useful for targeted proteomics assay development.

Statin therapy increases lipoprotein(a) levels

Aims

Lipoprotein(a) [Lp(a)] is elevated in 20–30% of people. This study aimed to assess the effect of statins on Lp(a) levels.

Methods and results

This subject-level meta-analysis includes 5256 patients (1371 on placebo and 3885 on statin) from six randomized trials, three statin-vs.-placebo trials, and three statin-vs.-statin trials, with pre- and on-treatment (4–104 weeks) Lp(a) levels. Statins included atorvastatin 10 mg/day and 80 mg/day, pravastatin 40 mg/day, rosuvastatin 40 mg/day, and pitavastatin 2 mg/day. Lipoprotein(a) levels were measured with the same validated assay. The primary analysis of Lp(a) is based on the log-transformed data. In the statin-vs.-placebo pooled analysis, the ratio of geometric means [95% confidence interval (CI)] for statin to placebo is 1.11 (1.07–1.14) (P &lt; 0.0001), with ratio &gt;1 indicating a higher increase in Lp(a) from baseline in statin vs. placebo. The mean percent change from baseline ranged from 8.5% to 19.6% in the statin groups and −0.4% to −2.3% in the placebo groups. In the statin-vs.-statin pooled analysis, the ratio of geometric means (95% CI) for atorvastatin to pravastatin is 1.09 (1.05–1.14) (P &lt; 0.0001). The mean percent change from baseline ranged from 11.6% to 20.4% in the pravastatin group and 18.7% to 24.2% in the atorvastatin group. Incubation of HepG2 hepatocytes with atorvastatin showed an increase in expression of LPA mRNA and apolipoprotein(a) protein.

Conclusion

This meta-analysis reveals that statins significantly increase plasma Lp(a) levels. Elevations of Lp(a) post-statin therapy should be studied for effects on residual cardiovascular risk.

Impact of Apolipoprotein(a) Isoform Size on Lipoprotein(a) Lowering in the HPS2-THRIVE Study

Supplemental Digital Content is available in the text.

Background:

Genetic studies have shown lipoprotein(a) (Lp[a]) to be an important causal risk factor for coronary disease. Apolipoprotein(a) isoform size is the chief determinant of Lp(a) levels, but its impact on the benefits of therapies that lower Lp(a) remains unclear.

Methods:

HPS2-THRIVE (Heart Protection Study 2–Treatment of HDL to Reduce the Incidence of Vascular Events) is a randomized trial of niacin–laropiprant versus placebo on a background of simvastatin therapy. Plasma Lp(a) levels at baseline and 1 year post-randomization were measured in 3978 participants from the United Kingdom and China. Apolipoprotein(a) isoform size, estimated by the number of kringle IV domains, was measured by agarose gel electrophoresis and the predominantly expressed isoform identified.

Results:

Allocation to niacin–laropiprant reduced mean Lp(a) by 12 (SE, 1) nmol/L overall and 34 (6) nmol/L in the top quintile by baseline Lp(a) level (Lp[a] ≥128 nmol/L). The mean proportional reduction in Lp(a) with niacin–laropiprant was 31% but varied strongly with predominant apolipoprotein(a) isoform size (P_Trend=4×10⁻²⁹) and was only 18% in the quintile with the highest baseline Lp(a) level and low isoform size. Estimates from genetic studies suggest that these Lp(a) reductions during the short term of the trial might yield proportional reductions in coronary risk of ≈2% overall and 6% in the top quintile by Lp(a) levels.

Conclusions:

Proportional reductions in Lp(a) were dependent on apolipoprotein(a) isoform size. Taking this into account, the likely benefits of niacin–laropiprant on coronary risk through Lp(a) lowering are small. Novel therapies that reduce high Lp(a) levels by at least 80 nmol/L (≈40%) may be needed to produce worthwhile benefits in people at the highest risk because of Lp(a).

Clinical Trial Registration:

URL: https://clinicaltrials.gov. Unique identifier: NCT00461630.

Lipoprotein(a) Particle Production as a Determinant of Plasma Lipoprotein(a) Concentration Across Varying Apolipoprotein(a) Isoform Sizes and Background Cholesterol-Lowering Therapy

Background Elevated lipoprotein(a) (Lp(a)), a low-density lipoprotein-like particle bound to the polymorphic apolipoprotein(a) (apo(a)), may be causal for cardiovascular disease. However, the metabolism of Lp(a) in humans is poorly understood. Methods and Results We investigated the kinetics of Lp(a)-apo(a) and low-density lipoprotein-apoB-100 in 63 normolipidemic men. The fractional catabolic rate ( FCR ) and production rate PR ) were studied. Plasma apo(a) concentration was significantly and inversely associated with apo(a) isoform size ( r=-0.536, P<0.001) and apo(a) FCR ( r=-0.363, P<0.01), and positively with apo(a) PR ( r=0.877, P<0.001). There were no significant associations between the FCR s of apo(a) and low-density lipoprotein-apoB-100. Subjects with smaller apo(a) isoform sizes (≤22 kringle IV repeats) had significantly higher apo(a) PR ( P<0.05) and lower apo(a) FCR ( P<0.01) than those with larger sizes. Plasma apo(a) concentration was significantly associated with apo(a) PR ( r=0.930, P<0.001), but not with FCR ( r=-0.012, P>0.05) in subjects with smaller apo(a) isoform size. In contrast, both apo(a) PR and FCR were significantly associated with plasma apo(a) concentrations ( r=0.744 and -0.389, respectively, P<0.05) in subjects with larger isoforms. In multiple regression analysis, apo(a) PR and apo(a) isoform size were significant predictors of plasma apo(a) concentration independent of low-density lipoprotein-apoB-100 FCR and background therapy with atorvastatin and evolocumab. Conclusions In normolipidemic men, the plasma Lp(a) concentration is predominantly determined by the rate of production of Lp(a) particles, irrespective of apo(a) isoform size and background therapy with a statin and a proprotein convertase subtilisin-kexin type 9 inhibitor. Our findings underscore the importance of therapeutic targeting of the hepatic synthesis and secretion of Lp(a) particles. Lp(a) particle catabolism may only play a modest role in determining Lp(a) concentration in subjects with larger apo(a) isoform size. Clinical Trial Registration URL : http://www.clinicaltrials.gov . Unique identifier: NCT 02189837.

Can Lp(a) Lowering Against Background Statin Therapy Really Reduce Cardiovascular Risk?

PURPOSE OF REVIEW

The association between elevated plasma levels of lipoprotein (a) [Lp(a)] and atherosclerotic cardiovascular disease (ASCVD) has been discussed for many years. Recent genetic findings have confirmed that elevated Lp(a) similar to elevated LDL-cholesterol (LDL-C) might be causally related to premature ASCVD. Lp(a) is relatively refractory to lifestyle interventions. The results of studies with statins and their possible effect on Lp(a) are conflicting. Specific Lp(a) apheresis is used as a treatment against background statin therapy and can decrease Lp(a). The purpose of this review is to discuss whether new drugs which decrease Lp(a) can prevent ASCVD and decrease ASCVD mortality when applied in addition to statins.

RECENT FINDINGS

Some new LDL-C-lowering drugs such as mipomersen and lomitapide decrease elevated Lp(a) in addition to statins but they have some unpleasant adverse effects. Recently, an antisense oligonucleotide against apo(a), AKCEA-APO(a)Rx, has been shown to selectively decrease Lp(a). The most recent advance in LDL-C lowering are PCSK9 inhibitors. Alirocumab and evolocumab do not only significantly reduce LDL-C on top of maximally tolerated statin therapy and prevent ASCVD events, but also further decrease Lp(a). There is no data to indicate whether mipomersen, lomitapide, or IONIS-APO(a)-LRx decrease ASCVD events and mortality. Conclusive evidence is still lacking as to whether the treatment with PCSK9 inhibitors against background statin therapy actually additionally reduces ASCVD risk due to the lowering of Lp(a) or simply due to lowering LDL-C to levels much lower than high-intensity statin treatment as monotherapy. Ongoing trials will probably provide an answer to these questions.

Hyperlipidemias and Obesity

The organs require oxygen and other types of nutrients (amino acids, sugars, and lipids) to function, the heart consuming large amounts of fatty acids for oxidation and adenosine triphosphate (ATP) generation.