Significant associations between lipoprotein(a) and corrected apolipoprotein B-100 levels in African-Americans

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.

Lipoprotein(a) and the risk of recurrent coronary heart disease: the Dubbo Study

OBJECTIVE

Elevated Lipoprotein(a) [Lp(a)] has not been firmly established as a risk factor for recurrent coronary heart disease (CHD). The present analysis explored this relationship in senior citizens.

METHODS

This was a longitudinal study in 607 subjects, all with prevalent CHD, mean age 71 years, followed for 16 years. Baseline examinations of lipids and other CHD risk factors were conducted in 1988-89 in Dubbo, Australia. The independent contribution of Lp(a) to a further CHD event was examined in proportional hazards regression models.

RESULTS

There were 399 incident CHD cases. Median Lp(a) in CHD cases was 130 mg/L (Interquartile range 60-315) and in non-cases 105 mg/L (45-250) (p < .07, U-Test). 26% of CHD cases and 19% of non-cases had Lp(a) 300 + mg/L; 18% of CHD cases and 8% of non-cases had Lp(a) 500 + mg/L. Lp(a) in Quintile 5 of its distribution (355 + mg/L), using Lp(a) Quintile 1 (<50mg/L) as reference, significantly predicted recurrent CHD with Hazard Ratio 1.53 (95% CI 1.11-2.11, p = .01). Prediction was independent of other risk factors. Lp(a) 500 + mg/L versus lower, significantly predicted recurrent CHD with Hazard Ratio 1.59 (1.16-2.17, p < .01). Prediction was similarly significant for Lp(a) 300 + mg/L versus lower, with Hazard Ratio 1.37 (1.09-1.73, p < .01).

CONCLUSION

Elevated Lp(a) is an independent and significant predictor of recurrent CHD in senior citizens. Upper reference Lp(a) levels of 500 mg/L (≈125nmol/L) or 300 mg/L (≈75nmol/L) both appear to be appropriate. The clinical benefit of therapy to reduce elevated Lp(a) remains to be confirmed.

Apolipoprotein B and Cardiovascular Disease: Biomarker and Potential Therapeutic Target

Apolipoprotein (apo) B, the critical structural protein of the atherogenic lipoproteins, has two major isoforms: apoB48 and apoB100. ApoB48 is found in chylomicrons and chylomicron remnants with one apoB48 molecule per chylomicron particle. Similarly, a single apoB100 molecule is contained per particle of very-low-density lipoprotein (VLDL), intermediate density lipoprotein, LDL and lipoprotein(a). This unique one apoB per particle ratio makes plasma apoB concentration a direct measure of the number of circulating atherogenic lipoproteins. ApoB levels indicate the atherogenic particle concentration independent of the particle cholesterol content, which is variable. While LDL, the major cholesterol-carrying serum lipoprotein, is the primary therapeutic target for management and prevention of atherosclerotic cardiovascular disease, there is strong evidence that apoB is a more accurate indicator of cardiovascular risk than either total cholesterol or LDL cholesterol. This review examines multiple aspects of apoB structure and function, with a focus on the controversy over use of apoB as a therapeutic target in clinical practice. Ongoing coronary artery disease residual risk, despite lipid-lowering treatment, has left patients and clinicians with unsatisfactory options for monitoring cardiovascular health. At the present time, the substitution of apoB for LDL-C in cardiovascular disease prevention guidelines has been deemed unjustified, but discussions continue.

Treatment and prevention of lipoprotein(a)-mediated cardiovascular disease: the emerging potential of RNA interference therapeutics

Lipid- and lipoprotein-modifying therapies have expanded substantially in the last 25 years, resulting in reduction in the incidence of major adverse cardiovascular events. However, no specific lipoprotein(a) [Lp(a)]-targeting therapy has yet been shown to reduce cardiovascular disease risk. Many epidemiological and genetic studies have demonstrated that Lp(a) is an important genetically determined causal risk factor for coronary heart disease, aortic valve disease, stroke, heart failure, and peripheral vascular disease. Accordingly, the need for specific Lp(a)-lowering therapy has become a major public health priority. Approximately 20% of the global population (1.4 billion people) have elevated levels of Lp(a) associated with higher cardiovascular risk, though the threshold for determining ‘high risk’ is debated. Traditional lifestyle approaches to cardiovascular risk reduction are ineffective at lowering Lp(a). To address a lifelong risk factor unmodifiable by non-pharmacological means, Lp(a)-lowering therapy needs to be safe, highly effective, and tolerable for a patient population who will likely require several decades of treatment. N-acetylgalactosamine-conjugated gene silencing therapeutics, such as small interfering RNA (siRNA) and antisense oligonucleotide targeting LPA, are ideally suited for this application, offering a highly tissue- and target transcript-specific approach with the potential for safe and durable Lp(a) lowering with as few as three or four doses per year. In this review, we evaluate the causal role of Lp(a) across the cardiovascular disease spectrum, examine the role of established lipid-modifying therapies in lowering Lp(a), and focus on the anticipated role for siRNA therapeutics in treating and preventing Lp(a)-related disease.

Diet and Lp(a): Does Dietary Change Modify Residual Cardiovascular Risk Conferred by Lp(a)?

Lipoprotein(a) [Lp(a)] is an independent, causal, genetically determined risk factor for cardiovascular disease (CVD). We provide an overview of current knowledge on Lp(a) and CVD risk, and the effect of pharmacological agents on Lp(a). Since evidence is accumulating that diet modulates Lp(a), the focus of this paper is on the effect of dietary intervention on Lp(a). We identified seven trials with 15 comparisons of the effect of saturated fat (SFA) replacement on Lp(a). While replacement of SFA with carbohydrate, monounsaturated fat (MUFA), or polyunsaturated fat (PUFA) consistently lowered low-density lipoprotein cholesterol (LDL-C), heterogeneity in the Lp(a) response was observed. In two trials, Lp(a) increased with carbohydrate replacement; one trial showed no effect and another showed Lp(a) lowering. MUFA replacement increased Lp(a) in three trials; three trials showed no effect and one showed lowering. PUFA or PUFA + MUFA inconsistently affected Lp(a) in four trials. Seven trials of diets with differing macronutrient compositions showed similar divergence in the effect on LDL-C and Lp(a). The identified clinical trials show diet modestly affects Lp(a) and often in the opposing direction to LDL-C. Further research is needed to understand how diet affects Lp(a) and its properties, and the lack of concordance between diet-induced LDL-C and Lp(a) changes.

Proprotein convertase subtilisin/kexin type 9 inhibitors and lipoprotein(a)-mediated risk of atherosclerotic cardiovascular disease: more than meets the eye?

PURPOSE OF REVIEW

Evidence continues to mount for elevated lipoprotein(a) [Lp(a)] as a prevalent, independent, and causal risk factor for atherosclerotic cardiovascular disease. However, the effects of existing lipid-lowering therapies on Lp(a) are comparatively modest and are not specific to Lp(a). Consequently, evidence that Lp(a)-lowering confers a cardiovascular benefit is lacking. Large-scale cardiovascular outcome trials (CVOTs) of inhibitory mAbs targeting proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) may address this issue.

RECENT FINDINGS

Although the ability of PCSK9i to lower Lp(a) by 15-30% is now clear, the mechanisms involved continue to be debated, with in-vitro and in-vivo studies showing effects on Lp(a) clearance (through the LDL receptor or other receptors) and Lp(a)/apolipoprotein(a) biosynthesis in hepatocytes. The FOURIER CVOT showed that patients with higher baseline levels of Lp(a) derived greater benefit from evolocumab and those with the lowest combined achieved Lp(a) and LDL-cholesterol (LDL-C) had the lowest event rate. Meta-analysis of ten phase 3 trials of alirocumab came to qualitatively similar conclusions concerning achieved Lp(a) levels, although an effect independent of LDL-C lowering could not be demonstrated.

SUMMARY

Although it is not possible to conclude that PCSK9i specifically lower Lp(a)-attributable risk, patients with elevated Lp(a) could derive incremental benefit from PCSK9i therapy.

Schimke immunoosseous dysplasia and management considerations for vascular risks

Schimke immunoosseous dysplasia (SIOD) is a multisystemic condition characterized by early arteriosclerosis and progressive renal insufficiency, among other features. Many SIOD patients have severe, migraine-like headaches, transient neurologic attacks, or cerebral ischemic events. Cerebral events could be exacerbated or precipitated by hypertension, and it is unclear how these are related to arteriosclerotic changes as dyslipidemia is also a feature of SIOD. The correlation between hypercholesterolemia and cardiovascular risk in SIOD is unclear. Also, the etiology and management of headaches is not well characterized. Here we report our clinical observations in the management of SIOD in a patient who was diagnosed in school age despite early signs and symptoms. We describe biallelic variants, including a previously unreported c.1931G>A (p.Arg644Gln) variant in SMARCAL1. We specifically investigated whether migraine-like headaches and progressive nephropathy may be related to blood pressure dysregulation. We found a correlation between tighter blood pressure regulation using ambulatory blood pressure monitoring and a subjective decrease in headache symptoms. We discuss blood pressure medication management in SIOD. We also characterize dyslipidemia relative to atherosclerosis risks and provide new management strategies to consider for optimizing care.

Effect of antiretroviral therapy on allele-associated Lp(a) level in women with HIV in the Women's Interagency HIV Study

We previously demonstrated an association between lipoprotein (a) [Lp(a)] levels and atherosclerosis in human immunodeficiency virus (HIV)-seropositive women. The effects of antiretroviral therapy (ART) on Lp(a) levels in relation to apo(a) size polymorphism remain unclear. ART effects on allele-specific apo(a) level (ASL), an Lp(a) level associated with individual apo(a) alleles within each allele-pair, were determined in 126 HIV-seropositive women. ART effects were tested by a mixed-effects model across pre-ART and post-ART first and third visits. Data from 120 HIV-seronegative women were used. The mean age was 38 years; most were African-American (∼70%). Pre-ART ASLs associated with the larger (4.6 mg/dl vs. 8.0 mg/dl, P = 0.024) or smaller (13 mg/dl vs. 19 mg/dl, P = 0.041) apo(a) sizes were lower in the HIV-seropositive versus HIV-seronegative group, as was the prevalence of a high Lp(a) level (P = 0.013). Post-ART ASL and prevalence of high Lp(a) or apo(a) sizes and frequency of small size apo(a) (22 kringles) did not differ between the two groups. ART increased Lp(a) level (from 18 to 24 mg/dl, P < 0.0001) and both ASLs (P < 0.001). In conclusion, regardless of genetic control, Lp(a) can be modulated by HIV and its treatment. ART initiation abrogates HIV-induced suppression of Lp(a) levels and ASLs, contributing to promote CVD risk in HIV-seropositive individuals.

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.

Lipoprotein(a) and the Apolipoprotein B/A1 Ratio Independently Associate With Surgery for Aortic Stenosis Only in Patients With Concomitant Coronary Artery Disease

Background

Aortic stenosis (AS) has different clinical phenotypes, including AS with or without concomitant coronary artery disease (CAD). It is unknown whether these phenotypes share the same risk factors. In particular, lipoprotein(a) [Lp(a)] and apolipoproteins (Apo) are associated with AS, but it is unknown whether these associations differ among phenotypes. In this prospective analysis we examined the impact of Lp(a) and Apo in subgroups of patients with AS.

Methods and Results

We identified 336 patients (mean age at survey 56.7 years, 48% female) who underwent surgery for AS after a median 10.9 years (interquartile range 9.3 years), participants in 1 of 3 large population surveys. For each patient, 2 matched referents were allocated. Lp(a) and Apo were analyzed in the baseline samples. Uni‐ and multivariable logistic regression analyses were used to estimate risks related to a 1 (ln) standard deviation increase in Lp(a) and the ratio of Apo B to Apo A1 (Apo B/A1 ratio). High levels of Lp(a) predicted surgery for AS in 203 patients with concomitant CAD (odds ratio [95% confidence intervals]) (1.29 [1.07‐1.55]), but not in 132 patients without CAD (1.04 [0.83‐1.29]) in the fully adjusted model. Similarly, a high Apo B/A1 ratio predicted surgery in patients with concomitant CAD (1.43 [1.16‐1.76]) but not in those without CAD (0.87 [0.69‐1.10]).

Conclusions

High levels of Lp(a) and a high Apo B/A1 ratio were associated with surgery for AS in patients with concomitant CAD but not in those with isolated AS. This finding may lead to a new avenue of research for targeted risk factor interventions in this population.

The roles of apo(a) size, phenotype, and dominance pattern in PCSK9-inhibition-induced reduction in Lp(a) with alirocumab

An elevated level of lipoprotein (a) [Lp(a)] is a risk factor for CVD. Alirocumab, a monoclonal antibody to proprotein convertase subtilisin/kexin type 9, is reported to reduce Lp(a) levels. The relationship of Lp(a) reduction with apo(a) size polymorphism, phenotype, and dominance pattern and LDL cholesterol (LDL-C) reduction was evaluated in a pooled analysis of 155 hypercholesterolemic patients (75 with heterozygous familial hypercholesterolemia) from two clinical trials. Alirocumab significantly reduced total Lp(a) (pooled median: -21%, P = 0.0001) and allele-specific apo(a), an Lp(a) level carried by the smaller (median: -18%, P = 0.002) or the larger (median: -37%, P = 0.0005) apo(a) isoform, at week 8 versus baseline. The percent reduction in Lp(a) level with alirocumab was similar across apo(a) phenotypes (single vs. double bands) and carriers and noncarriers of a small size apo(a) (≤22 kringles). The percent reduction in LDL-C correlated significantly with the percent reduction in Lp(a) level (r = 0.407, P < 0.0001) and allele-specific apo(a) level associated with the smaller (r = 0.390, P < 0.0001) or larger (r = 0.270, P = 0.0183) apo(a) sizes. In conclusion, alirocumab-induced Lp(a) reduction was independent of apo(a) phenotypes and the presence or absence of a small size apo(a).

LDL-cholesterol Predicts a First CHD Event in Senior Citizens, Especially So in Those With Elevated Lipoprotein(a): Dubbo Study of the Elderly

OBJECTIVE

The analysis was designed to explore the combined effects of LDL-cholesterol and lipoprotein(a) (Lp(a)) in predicting incident coronary heart disease (CHD) in senior citizens without prior CHD.

METHODS

This is a prospective cohort study in Dubbo NSW which has followed 2805 men and women 60 years and older for 16 years since 1988-1989. Subjects with prior CHD (n=607) were excluded from this analysis. Incident CHD events were identified by hospital record linkage. The contributions of LDL and Lp(a) to CHD events and their combined effects were evaluated in proportional hazards regression models.

RESULTS

There were 689 CHD events over 16 years in a cohort of 2198 men and women without prior CHD. LDL-cholesterol (corrected for cholesterol content of Lp(a)) and Lp(a) modelled in quartile categories each independently predicted CHD, but exclusively in Quartile 4 (Q4) for each parameter. Using the combination of LDL Q1 and Lp(a) Q1 as a reference group, LDL Q4 (>4.90mmol/L) most clearly predicted CHD in combination with Lp(a) Q4 (>276mg/L), hazard ratio 1.95 (95%CI 1.31-2.90).

CONCLUSION

The present findings may have important practical implications in clinical management. If Lp(a) is assessed in senior citizens without prior CHD and found to be genuinely low, elevated LDL-cholesterol may not require active intervention.

Is the ratio of apoB/apoA-1 the best predictor for the severity of coronary artery lesions in Chinese diabetics with stable angina pectoris? An assessment based on Gensini scores

Background

There is a paucity of data about the best lipid ratio predicting the severity of coronary artery disease (CAD) in patients with diabetes mellitus. We determined the relationship between five conventional lipid ratios and the extent of coronary artery lesions in Chinese Type 2 diabetics with stable angina pectoris (SAP).

Methods

A prospective cohort study within 373 type 2 diabetic patients diagnosed with stable CAD by coronary angiography was performed. All patients were classified into three groups according to the tertiles of Gensini scores (GS, low group < 8 points n = 143; intermediate group 8–28 points, n = 109; high group > 28 points, n = 121). Association between the ratios of apolipoprotein (apo) B and apoA-1, total cholesterol and high density lipoprotein cholesterol (TC/HDL-C), triglycerides and HDL-C (TG/HDL-C), low density lipoprotein cholesterol and HDL-C (LDL-C/HDL-C), Non-HDL-C/HDL-C and GS were evaluated using the receivers operating characteristic (ROC) curves and multivariate logistic regression models.

Results

The ratio of apoB/apoA-1, TC/HDL-C, LDL-C/HDL-C, and Non-HDL-C/HDL-C were correlated with Gensini scores. Area under the ROC curves for predicting high Gensini scores in the ratios of apoB/apoA-1, TC/HDL-C, LDL-C/HDL-C and Non-HDL-C/HDL-C were 0.62, 0.60, 0.59 and 0.60, respectively (P < 0.005 for all). According to multivariate logistic regression analysis after adjusted with demographic characteristic and other lipid parameters, the ratio of apoB/apoA-1 is qualified as an independent discriminator for the severity of CAD. However, after further adjusting different baseline variables, such as left ventricular ejective fraction, hemoglobin A1c, leukocytes count and serum creatinine, none of the above lipid ratios remained.

Conclusions

Compared with other lipid parameters, the ratio of apoB/apoA-1 appears to be more significantly correlated with the extent of coronary artery lesions in Chinese diabetics, but it was not an independent predictor in these settings.

Role of lipoprotein(a) in predicting the severity of new on-set coronary artery disease in type 2 diabetics: A Gensini score evaluation

The objective of the study was to investigate the usefulness of serum lipoprotein(a) level in predicting the severity of new on-set coronary artery disease in type 2 diabetics. A total of 1254 new on-set, consecutive coronary artery disease patients were classified into two groups: diabetes group (n = 380) and non-diabetes group (n = 874). The relationship between serum lipoprotein(a) levels and the severity of coronary artery disease assessed by Gensini score was analysed. Data showed that the diabetes group had higher serum triglyceride and high sensitivity C-reactive protein levels but lower high-density lipoprotein cholesterol levels (all p < 0.05). The multivariate logistic regression analysis suggested that lipoprotein(a) was an independent predictor for high Gensini score (odds ratio = 1.82, 95% confidence interval: 1.10-3.12, p = 0.029) after adjusting for traditional cardiovascular risk factors. Additionally, lipoprotein(a) levels were positively correlated with Gensini score (rho = 0.15, p = 0.014) and significantly elevated according to the tertiles of Gensini score (p = 0.008) in diabetics. However, no such results were observed in non-diabetics. Our data indicate that lipoprotein(a) is an independent predictor for the severity of new on-set coronary artery disease patients accompanied by type 2 diabetes, suggesting that these patients may benefit from lipoprotein(a) management in clinical assessment.