Low lipoprotein(a) concentration is associated with cancer and all-cause deaths: a population-based cohort study (the JMS cohort study)

Lack of significant associations between single nucleotide polymorphisms in LPAL2-LPA genetic region and all cancer incidence and mortality in Japanese population: The Japan public health center-based prospective study

BACKGROUND

High lipoprotein (a) level is an established cardiovascular risk, but its association with non-cardiovascular diseases, especially cancer, is controversial. Serum lipoprotein (a) levels vary widely by genetic backgrounds and are largely determined by the genetic variations of apolipoprotein (a) gene, LPA. In this study, we investigate the association between SNPs in LPA region and cancer incidence and mortality in Japanese.

METHODS

A genetic cohort study was conducted utilizing the data from 9923 participants in the Japan Public Health Center-based Prospective Study (JPHC Study). Twenty-five SNPs in the LPAL2-LPA region were selected from the genome-wide genotyped data. Cox regression analysis adjusted for the covariates and competing risks of death from other causes, were used to estimate the relative risk (hazard ratios (HR) with 95% confidence intervals (CI)) of overall and site-specific cancer incidence and mortality, for each SNP.

RESULTS

No significant association was found between SNPs in the LPAL2-LPA region and cancer incidence or mortality (overall/site-specific cancer). In men, however, HRs for stomach cancer incidence of 18SNPs were estimated higher than 1.5 (e.g., 2.15 for rs13202636, model free, 95%CI: 1.28-3.62) and those for stomach cancer mortality of 2SNPs (rs9365171, rs1367211) were estimated 2.13 (recessive, 95%CI:1.04-4.37) and 1.61 (additive, 95%CI: 1.00-2.59). Additionally, the minor allele for SNP rs3798220 showed increased death risk from colorectal cancer (CRC) in men (HR: 3.29, 95% CI:1.59 - 6.81) and decreased CRC incidence risk in women (HR: 0.46, 95%CI: 0.22-0.94). Minor allele carrier of any of 4SNPs could have risk of prostate cancer incidence (e.g., rs9365171 dominant, HR: 1.71, 95%CI: 1.06-2.77).

CONCLUSIONS

None of the 25 SNPs in the LPAL2-LPA region was found to be significantly associated with cancer incidence or mortality. Considering the possible association between SNPs in LPAL2-LPA region and colorectal, prostate and stomach cancer incidence or mortality, further analysis using different cohorts is warranted.

Lipoprotein(a)-related cardiovascular and all-cause mortalities in Korean adults

AIMS

There are inconsistent results on the association between lipoprotein(a) and mortality-related outcomes due to a lack of evidence from large-scale observational studies of Asians. This study aims to evaluate the effects of lipoprotein(a) on mortality-related outcomes in the Korean population.

METHODS AND RESULTS

This cohort study included 275 430 individuals (mean age: 38 years; 50.1% men) enrolled in the Kangbuk Samsung Health Study between 2003 and 2016. The median follow-up period was 6.6 years. Cox proportional hazards analysis was used to estimate the adjusted hazard ratios (HRs) for evaluating mortality risk based on lipoprotein(a) levels and specific lipoprotein(a) categories. The median lipoprotein(a) value was 18.5 mg/dL, and the proportion of lipoprotein(a) ≥50 mg/dL was 12.8%. Multivariable Cox regression analysis showed that the group with lipoprotein(a) ≥50 mg/dL had a significantly increased risk of cardiovascular mortality (HR[95% CI]: 1.83[1.26, 2.64]) and all-cause mortality (1.20[1.03, 1.41]) than the group with lipoprotein(a) < 50 mg/dL without increased risk of cancer mortality (1.05[0.81, 1.34]). The relationship between lipoprotein(a) and cardiovascular mortality was significant regardless of low-density lipoprotein cholesterol. Specifically, lipoprotein(a) ≥100 mg/dL was associated with more than twice as increased a risk of cardiovascular mortality (2.45[1.12, 5.34]) than lipoprotein(a) < 10 mg/dL. In subgroup analyses, there was an interaction in the relationships between the two lipoprotein(a) categories and cardiovascular mortality for only high-density lipoprotein cholesterol.

CONCLUSIONS

High lipoprotein(a) concentration is an independent predictor of cardiovascular mortality in the Korean population, regardless of low-density lipoprotein cholesterol levels.

Circulating lipoprotein (a) and all-cause and cause-specific mortality: a systematic review and dose-response meta-analysis

AIMS

To investigate the association between circulating lipoprotein(a) (Lp(a)) and risk of all-cause and cause-specific mortality in the general population and in patients with chronic diseases, and to elucidate the dose-response relations.

METHODS AND RESULTS

We searched literature to find prospective studies reporting adjusted risk estimates on the association of Lp(a) and mortality outcomes. Forty-three publications, reporting on 75 studies (957,253 participants), were included. The hazard ratios (HRs) and 95% confidence intervals (95%CI ) for the top versus bottom tertile of Lp(a) levels and risk of all-cause mortality were 1.09 (95%CI: 1.01-1.18, I²: 75.34%, n = 19) in the general population and 1.18 (95%CI: 1.04-1.34, I²: 52.5%, n = 12) in patients with cardiovascular diseases (CVD). The HRs for CVD mortality were 1.33 (95%CI: 1.11-1.58, I²: 82.8%, n = 31) in the general population, 1.25 (95%CI: 1.10-1.43, I²: 54.3%, n = 17) in patients with CVD and 2.53 (95%CI: 1.13-5.64, I²: 66%, n = 4) in patients with diabetes mellitus. Linear dose-response analyses revealed that each 50 mg/dL increase in Lp(a) levels was associated with 31% and 15% greater risk of CVD death in the general population and in patients with CVD. No non-linear dose-response association was observed between Lp(a) levels and risk of all-cause or CVD mortality in the general population or in patients with CVD (P_nonlinearity > 0.05).

CONCLUSION

This study provides further evidence that higher Lp(a) levels are associated with higher risk of all-cause mortality and CVD-death in the general population and in patients with CVD. These findings support the ESC/EAS Guidelines that recommend Lp(a) should be measured at least once in each adult person's lifetime, since our study suggests those with higher Lp(a) might also have higher risk of mortality.

Association of lipoprotein(a) with all-cause and cause-specific mortality: A prospective cohort study

BACKGROUND

A growing number of studies have demonstrated a causal association between lipoprotein(a) [Lp(a)] and atherosclerotic cardiovascular diseases (ASCVDs), but its association with all-cause and cause-specific mortality remains unclear. Therefore, this study aimed to explore the association of Lp(a) with all-cause and cause-specific mortality.

METHODS

This prospective cohort study included 8,525 participants from the third National Health and Nutrition Examination Survey. Lp(a) was considered an exposure variable, all-cause and cause-specific mortality were used as outcome variables, and all participants were followed from the interview date until death or December 31, 2015. COX proportional hazards regression models, stratified analysis, sensitivity analysis, restricted cubic spline plots and Kaplan-Meier survival curves were used to analyze the association of Lp(a) with all-cause and cause-specific mortality.

RESULTS

After adjusting for traditional cardiovascular risk factors, Lp(a) remained strongly associated with all-cause and CVDs-related mortality (P for trend = 0.007 and < 0.001). Subgroup analyses showed that higher Lp(a) remained associated with higher risk of all-cause mortality in those > 60 years of age, with a BMI < 30 kg/m², and without diabetes, whereas the association between Lp(a) and CVDs-related mortality remained stable in participants ≤ 60 years of age, male, with a BMI < 30 kg/m², with hypertension, without diabetes, or without CVDs (P < 0.05). In sensitivity analyses, we found that the association of Lp(a) with all-cause and CVDs-related mortality remained robust after excluding individuals who died within one year of follow-up (P for trend = 0.041 and 0.002).

CONCLUSIONS

Lp(a) was associated with the risk of all-cause and CVDs-related mortality.

Lipoprotein(a) and cardiovascular and valvular diseases: A genetic epidemiological perspective

Rates of atherosclerotic cardiovascular diseases (CVD) in the Western world have spectacularly decreased over the past 50 years. However, a substantial proportion of high-risk patients still develop heart attacks, strokes and valvular heart diseases despite benefiting from state-of-the-art treatments including lipid-lowering therapies. Over the past 10-15 years, it has become increasingly clear that Lipoprotein(a) (Lp[a]) is a critical component of this so-called residual risk. Genetic association studies revealed that Lp(a) is robustly, independently and causally associated with a broad range of cardiovascular and valvular heart diseases. Up to 1 billion people around the globe may have an Lp(a) level that places them in a high-risk category. Lp(a) is strongly associated with calcific aortic valve stenosis (CAVS), coronary artery disease (CAD), peripheral arterial disease (PAD) and to a lesser extent with ischemic stroke (IS) and heart failure (HF). Because of this strong association with cardiovascular and valvular heart diseases, Lp(a) even emerged as one of the most important genetic determinants of human lifespan and healthspan. Here, we review the evidence from the largest and most informative genetic association studies and prospective studies that have investigated the association between Lp(a) and human lifespan, healthspan, CVD, CAVS and non-cardiovascular diseases. We present Lp(a) threshold values that may be clinically relevant and identify other cardiovascular risk factors that may modulate the absolute risk of CVD in individuals with high Lp(a) levels. Finally, we identify key clinical and research questions that require further investigation to eventually and optimally reduce CVD risk in patients with high Lp(a) levels.

A case of hyperlipoprotein(a)emia undergoing catheter interventions for coronary artery disease, aortic valve stenosis, and peripheral artery disease

A 79-year-old woman was admitted to our hospital for ischemic necrosis of the right first toe. During having normal lipid profiles, such as low-density lipoprotein cholesterol and triglyceride, plasma levels of lipoprotein(a) (Lp(a)] were abnormally high (141 mg/dL). She had a history of heart failure (HF) due to aortic valve stenosis (AS) and drug-eluting coronary stenting due to angina pectoris. To avoid worsening of HF and limb ischemia during minor amputation, she underwent balloon aortic valvuloplasty and endovascular therapy. She was also placed on proprotein convertase subtilisin/kexin type 9 inhibitors (140 mg of evolocumab) every 2 weeks, which decreased her plasma Lp(a) levels to 105 mg/dL (26% decrease) at discharge. Elevated plasma Lp(a) levels could strongly affect the development of AS and progression of systemic atherosclerosis. The screening and treatment of increased plasma Lp(a) are imperative for patients with AS having peripheral arterial disease.

Associations of Lipoprotein(a) With Coronary Atherosclerotic Burden and All-Cause Mortality in Patients With ST-Segment Elevation Myocardial Infarction Treated With Primary Percutaneous Coronary Intervention

Background: The coronary atherosclerotic burden in patients with ST-segment elevation myocardial infarction (STEMI) has been identified as the main predictor of prognosis. However, the association of lipoprotein(a) [Lp(a)], a well-established proatherogenic factor, with atherosclerotic burden in patients with STEMI is unclear.

Methods: In total, 1,359 patients who underwent percutaneous coronary intervention (PCI) for STEMI were included in analyses. Three prespecified models with adjustment for demographic parameters and risk factors were evaluated. Generalized additive models and restricted cubic spline analyses were used to assess the relationships of Lp(a) with Gensini scores and the no-reflow phenomenon. Kaplan–Meier curves were generated to explore the predictive value of Lp(a) for long-term all-cause mortality. Furthermore, mRNA expression levels of LPA in different groups were compared using the GEO database.

Results: Patients in the highest tertile according to Lp(a) levels had an increased incidence of heart failure during hospitalization. Furthermore, patients with high levels of Lp(a) (>19.1 mg/dL) had sharply increased risks for a higher Gensini score (P_{for trend} = 0.03) and no-reflow (P_{for trend} = 0.002) after adjustment for demographic parameters and risk factors. During a median follow-up of 930 days, 132 deaths (9.95%) were registered. Patients with high levels of Lp(a) (>19.1 mg/dL) had the worst long-term prognosis (P_{for trend} < 0.0001). In a subgroup analysis, patients with higher Lp(a) still had the highest all-cause mortality. Additionally, the mRNA expression levels of LPA in patients with STEMI with lower cardiac function were higher than those in other groups (P = 0.003). A higher coronary atherosclerotic burden was correlated with higher LPA expression (P = 0.01).

Conclusion: This study provides the first evidence that Lp(a) (at both the protein and mRNA levels) is independently associated with coronary atherosclerotic lesions and prognosis in patients with STEMI treated with PCI.

Clinical Trial Registration:http://www.chictr.org.cn/index.aspx, identifier: ChiCTR1900028516.

High lipoprotein(a) and high risk of mortality

AIMS

Several lipoprotein(a)-lowering therapies are currently being developed with the long-term goal of reducing cardiovascular disease and mortality; however, the relationship between lipoprotein(a) and mortality is unclear. We tested the hypothesis that lipoprotein(a) levels are associated with risk of mortality.

METHODS AND RESULTS

We studied individuals from two prospective studies of the Danish general population, of which 69 764 had information on lipoprotein(a) concentrations, 98 810 on LPA kringle-IV type 2 (KIV-2) number of repeats, and 119 094 on LPA rs10455872 genotype. Observationally, lipoprotein(a) >93 mg/dL (199 nmol/L; 96th-100th percentiles) vs. <10 mg/dL (18 nmol/L; 1st-50th percentiles) were associated with a hazard ratio of 1.50 (95% confidence interval 1.28-1.76) for cardiovascular mortality and of 1.20 (1.10-1.30) for all-cause mortality. The median survival for individuals with lipoprotein(a) >93 mg/dL (199 nmol/L; 96th-100th percentiles) and ≤93 mg/dL (199 nmol/L; 1st-95th percentiles) were 83.9 and 85.1 years (log rank P = 0.005). For cardiovascular mortality, a 50 mg/dL (105 nmol/L) increase in lipoprotein(a) levels was associated observationally with a hazard ratio of 1.16 (1.09-1.23), and genetically with risk ratios of 1.23 (1.08-1.41) based on LPA KIV2 and of 0.98 (0.88-1.09) based on LPA rs10455872. For all-cause mortality, corresponding values were 1.05 (1.01-1.09), 1.10 (1.04-1.18), and 0.97 (0.92-1.02), respectively. Finally, for a similar cholesterol content increase, lipoprotein(a) was more strongly associated with cardiovascular and all-cause mortality than low-density lipoprotein, implying that the mortality effect of high lipoprotein(a) is above that explained by its cholesterol content.

CONCLUSION

High levels of lipoprotein(a), through corresponding low LPA KIV-2 number of repeats rather than through high cholesterol content were associated with high risk of mortality. These findings are novel.

Hyperlipoproteinemia (a) is associated with breast cancer in a Han Chinese population

To investigate the relationship between serum lipoprotein (a) (LP(a)) levels and breast cancer as well as the clinicopathologic characteristics of breast cancer in a Han Chinese population.This study included 314 breast cancer patients, 51 patients with benign breast tumors, and 185 healthy control subjects. All study subjects were Han Chinese with similar socio-economic backgrounds, who were local residents of Zhoushan, Zhejiang, China or who had lived in Zhoushan for a long period of time. Serum concentrations of LP(a) were determined using a latex-enhanced immunoturbidimetric assay. Clinicopathological characteristics of patients were retrieved from medical records, which included the histopathological type, grade, stage, and molecular subtype of the disease, the expression of estrogen receptor (ER), progesterone receptor (PR), HER2, and Ki67, and the level of reproductive hormones. Correlations between 2 groups were evaluated using the Spearman correlation analysis. Associations among ≥3 groups were interpreted using the Kruskal-Wallis H test or the logistic regression test.Elevated serum LP(a) levels were detected in breast cancer patients compared with healthy control subjects, but no significant differences in LP(a) were detected between breast cancer and benign tumor or between benign tumor and healthy control. In breast cancer patients, serum LP(a) levels were inversely associated with HER2 expression, but they were not significantly correlated with any other clinicopathologic characteristics of breast cancer evaluated in this study.Elevated serum LP(a) levels were associated with breast cancer in a Han Chinese population.

Apolipoprotein(a), an enigmatic anti-angiogenic glycoprotein in human plasma: A curse or cure?

Angiogenesis is a finely co-ordinated, multi-step developmental process of the new vascular structure. Even though angiogenesis is regularly occurring in physiological events such as embryogenesis, in adults, it is restricted to specific tissue sites where rapid cell-turnover and membrane synthesis occurs. Both excessive and insufficient angiogenesis lead to vascular disorders such as cancer, ocular diseases, diabetic retinopathy, atherosclerosis, intra-uterine growth restriction, ischemic heart disease, stroke etc. Occurrence of altered lipid profile and vascular lipid deposition along with vascular disorders is a hallmark of impaired angiogenesis. Among lipoproteins, lipoprotein(a) needs special attention due to the presence of a multi-kringle protein subunit, apolipoprotein(a) [apo(a)], which is structurally homologous to many naturally occurring anti-angiogenic proteins such as plasminogen and angiostatin. Researchers have constructed different recombinant forms of apo(a) (rhLK68, rhLK8, RHACK2, KV-11, and AU-6) and successfully exploited its potential to inhibit unwanted angiogenesis during tumor metastasis and retinal neovascularization. Similar to naturally occurring anti-angiogenic proteins, apo(a) can directly interfere with angiogenic signaling pathways. Besides this, apo(a) can also exert its anti-angiogenic effect indirectly by inducing endothelial cell apoptosis, by inhibiting endothelial progenitor cell functions or by upregulating nuclear factors in endothelial cells via apo(a)-bound oxPLs. However, the impact of the anti-angiogenic potential of native apo(a) during physiological angiogenesis in embryos and wounded tissues is not yet explored. In this context, we review the studies so far done to demonstrate the anti-angiogenic activity of apo(a) and the recent developments in using apo(a) as a therapeutic agent to treat impaired angiogenesis during vascular disorders, with emphasis on the gaps in the literature.

Serum lipoprotein(a) and risk of mortality in patients on peritoneal dialysis

BACKGROUND

Elevated serum lipoprotein(a) [Lp(a)] level is an independent risk factor for atherosclerotic diseases in the general population and hemodialysis patients. However, the association between Lp(a) levels and mortality has received little attention in peritoneal dialysis (PD) patients.

OBJECTIVE

The objective of the study was to evaluate the association of Lp(a) levels with all-cause and cardiovascular (CV) mortality in PD patients.

METHODS

This retrospective cohort study was conducted in PD patients enrolled from January 1, 2006 to December 31, 2015, and followed until December 31, 2018. Cox regression models were performed to assess the association of serum Lp(a) levels with all-cause and CV mortality in PD patients.

RESULTS

In total, 1492 incident PD patients were eligible for the study. During a median follow-up period of 45.1 months, 402 all-cause and 210 CV deaths occurred. Multivariate Cox regression analysis revealed that the first and third tertiles of Lp(a) levels were significantly associated with increased risk for all-cause mortality [hazard ratio (HR) = 1.33, 95% confidence interval (95% CI) = 1.01-1.75, P = .041; HR = 1.53, 95% CI = 1.18-1.98, P = .001, respectively] when compared with the second tertile, and the third tertile of Lp(a) level was independently associated with an 80% increased risk of CV mortality (HR = 1.80, 95% CI = 1.26-2.56, P = .001). Moreover, our results showed that the HRs per log unit higher Lp(a) level for all-cause and CV mortality were 1.53 (95% CI = 1.05-2.22, P = .027) and 2.41 (95% CI = 1.44-4.03, P < .001), respectively.

CONCLUSIONS

Our results suggest that both low and high serum Lp(a) levels are risk markers for all-cause death, but only a higher baseline serum Lp(a) level is an independent risk factor for CV mortality in PD patients.

Low reactivity of tumor MUC1-binding natural anti-α-galactoside antibody is a risk factor for breast cancer

Natural plasma anti-α-galactoside antibody (anti-Gal) reactivity was reported to vary inversely with the individual’s lipoprotein(a) [Lp(a)] size. Since MUC1 mucin over-expressed in tumors bear surrogate peptide ligands for anti-Gal, we examined if high anti-Gal reactivity in small size/high titer Lp(a) individuals correlated with lower incidence of breast cancer. Newer protocol for size determination revealed that Lp(a) in controls were significantly smaller than in breast cancer patients ( P =  0.0023; n = 46 in either group). Activity per unit plasma volume and specific reactivity (reactivity per unit immunoglobulin) of anti-Gal were significantly lower in cancer patients ( P = 0.0033). Specific reactivity lower than the mean of controls was a risk factor for breast cancer with odds ratio (OR) 3.2 (95% confidence interval [CI]: 1.368–7.557). Immunochemical staining using fluorescein isothiocyanate-labeled anti-Gal revealed absolute inactivity towards normal cells and strong recognition of cancer cells by the antibody. O-Glycosylation of MUC1, though more frequent than in normal cells, was incomplete in tumor cells as revealed by binding of the O-glycan-specific lectin jacalin, accounting for the access of anti-Gal to its peptide ligand in cancer MUC1. As tumor advanced and MUC1 with increasing affinity for anti-Gal was synthesized by the tumor, the specific reactivity of circulating anti-Gal also increased, apparently due to antigenic stimulation or affinity maturation by the proliferating MUC1, indicating that pre-cancer anti-Gal reactivity in patients should have been much lower than measured after detection of cancer and that lower reactivity of the antibody is a stronger risk factor for breast cancer than indicated by the OR above. Reactivity towards a given group of tumor MUC1 antigens increased in proportion to anti-Gal specific reactivity. Results suggested tumor-specific MUC1 as likely target for anti-Gal-mediated anti-cancer defense and offer infusion of small Lp(a) or high reactivity anti-Gal as possible immunopotentiation measures.

Impact statement

This paper offers a molecular explanation for the positive correlation of individuals’ lipoprotein(a) [Lp(a)] size with breast cancer incidence, found more pronounced using interference-free assays. It established unambiguously the marked affinity of human anti-Gal antibody towards cancer phenotype of the cell surface MUC1 and inertness towards normal cell MUC1. This selectivity enabled small Lp(a) molecules, known to produce higher specific reactivity anti-Gal by affinity maturation, to achieve more efficient immune defense so that women with specific reactivity lower than the mean value of normal subjects ran cancer risk with odds ratio (OR) above 3.2. However, increasing O-glycosylation and decreasing O-glycan length of MUC1 with tumor advance increased anti-Gal specific reactivity, indicating antigenic stimulation and/or affinity maturation of the antibody by tumor MUC1. Thus, pre-cancer anti-Gal specific reactivity should be lower than that measured on detection and the above OR actually higher. Results suggest small Lp(a) and high specific reactivity anti-Gal infusions as therapeutic options.

High Lipoprotein(a) Level Is Independently Associated with Adverse Clinicopathological Features in Patients with Prostate Cancer

Background

The effect of lipoprotein(a) (Lp(a)) on prostate cancer (PCa) is unclear. The aim of this study was to investigate the association between serum Lp(a) levels and clinicopathological features in patients with PCa.

Methods

A total of 376 consecutive pathologically diagnosed PCa patients were enrolled and were classified as a low-intermediate-risk group or a high-risk group. The association of Lp(a) and the other lipid parameters including total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), TC/HDL-C, LDL-C/HDL-C, and remnant cholesterol (RC) with clinicopathological parameters was tested by univariate and multivariate logistic regression analyses.

Results

The high-risk PCa patients tended to have higher Lp(a) levels (p = 0.022) while there was no significant difference regarding the other lipid parameters (p > 0.05) compared to low-intermediate-risk counterparts. Patients with PSA ≥ 100 ng/ml had significantly higher Lp(a) levels than subjects with PSA < 100 ng/ml (p = 0.002). Univariate logistic regression analyses revealed that high Lp(a) levels were correlated with high-risk PCa (Q4 vs. Q1, HR = 2.687, 95% CI: 1.113-6.491, p = 0.028), while the other lipid parameters were not correlated with high-risk PCa. In the stepwise multivariate regression analysis, the association between Lp(a) levels and high-risk PCa remained significant (Q4 vs. Q1, HR = 2.890, 95% CI: 1.148-7.274, p = 0.024) after adjusting for confounding factors including age, body mass index, hypertension, diabetes, coronary artery disease, and lipid-lowering drugs.

Conclusions

This is the first study showing the positive association between high Lp(a) and adverse clinicopathological features of PCa. PCa patients with high Lp(a) tends to be more aggressive and should receive more attention in clinical practice.

Activity of MUC1 cancer antigen-binding plasma anti-α-galactoside antibody correlates inversely with size of autologous lipoprotein(a)

Variation in ligand-binding affinity of natural plasma anti-α-galactoside antibody (anti-Gal) is a plausible reason for differing anti-cancer defense among individuals since serine- and threonine-rich peptide sequences (STPS) in the cancer-specific MUC-1 antigen are surrogate ligands for this antibody. As affinity of a natural antibody could be modulated by systemic antigens by processes including affinity maturation, we examined the contribution of the size of lipoprotein(a) [Lp(a)], an efficient autologous anti-Gal-binding macromolecule that possesses variable numbers of STPS due to genetically determined size polymorphism, towards the specific activity (activity per unit mass) of anti-Gal. Binding of purified Lp(a) to FITC-labeled anti-Gal, measured in terms of increase in fluorescence of the latter, was inhibited by LDL in proportion to Lp(a) size presumably because LDL molecules also bind noncovalently and in proportion to Lp(a) size at the O-glycosylated and STPS-rich region of Lp(a). For the same reason, circulating forms of smaller Lp(a) which carried fewer or no noncovalently attached LDL molecules were more efficient ligands for the antibody than the same number of larger ones ( P < 0.0001). Result suggested that smaller Lp(a), with their STPS ligands less obstructed by adhering LDL, would be more effective systemic antigens for anti-Gal. In confirmation of this, the specific activity of anti-Gal decreased with Lp(a) size (r − 0.5443; P < 0.0001) but increased with Lp(a) concentration (r 0.6202; P < 0.0001) among 73 normal plasma samples. IgG to IgM ratio, an index of immunoglobulin class switching characteristic of affinity maturation, was decidedly higher for anti-Gal in small Lp(a) individuals than in their large Lp(a) counterparts ( P = 0.0014). Results indicated that modulation of activity of anti-Gal by Lp(a) size may account for the lower incidence of cancer reported in people carrying more plasma Lp(a) which are generally smaller as well.

Using topic modeling via non-negative matrix factorization to identify relationships between genetic variants and disease phenotypes: A case study of Lipoprotein(a) (LPA)

Genome-wide and phenome-wide association studies are commonly used to identify important relationships between genetic variants and phenotypes. Most studies have treated diseases as independent variables and suffered from the burden of multiple adjustment due to the large number of genetic variants and disease phenotypes. In this study, we used topic modeling via non-negative matrix factorization (NMF) for identifying associations between disease phenotypes and genetic variants. Topic modeling is an unsupervised machine learning approach that can be used to learn patterns from electronic health record data. We chose the single nucleotide polymorphism (SNP) rs10455872 in LPA as the predictor since it has been shown to be associated with increased risk of hyperlipidemia and cardiovascular diseases (CVD). Using data of 12,759 individuals with electronic health records (EHR) and linked DNA samples at Vanderbilt University Medical Center, we trained a topic model using NMF from 1,853 distinct phenotypes and identified six topics. We tested their associations with rs10455872 in LPA. Topics enriched for CVD and hyperlipidemia had positive correlations with rs10455872 (P < 0.001), replicating a previous finding. We also identified a negative correlation between LPA and a topic enriched for lung cancer (P < 0.001) which was not previously identified via phenome-wide scanning. We were able to replicate the top finding in a separate dataset. Our results demonstrate the applicability of topic modeling in exploring the relationship between genetic variants and clinical diseases.

Lipoprotein (a): a promising prognostic biomarker in patients with hepatocellular carcinoma after curative resection

Purpose

This study aimed to explore serum lipoprotein (a) (Lp(a)) levels and investigate their prognostic value in hepatocellular carcinoma (HCC) patients after curative resection.

Materials and methods

One cohort of 102 healthy individuals, one cohort of 172 HCC patients, and one cohort of 171 HCC patients undergoing curative resection were studied to evaluate serum Lp(a) levels and their prognostic significance, using Kaplan-Meier curves and log-rank tests.

Results

The Lp(a) levels in HCC patients were significantly lower than those in healthy individuals. Furthermore, the levels in HCC patients were significantly associated with recurrence. HCC patients were stratified into high Lp(a) (>20 mg/L) and low Lp(a) (≤20 mg/L) groups, using an optimal cutoff point for the Lp(a) of 20 mg/L. Low Lp(a) levels significantly correlated with tumor recurrence and survival time; HCC patients with low Lp(a) levels had higher recurrence rates and shorter survival time than those with high Lp(a) levels; Lp(a) was an independent prognostic factor for relapse-free survival and overall survival, and retained its prognostic value for α-fetoprotein ≤400 ng/mL and tumor size ≤5 cm subgroups in the training and validation cohorts.

Conclusion

Lp(a) was a promising and useful marker for assessing and monitoring recurrence and prognosis of patients with HCC, and improving Lp(a) levels may be a promising therapeutic strategy in HCC patients.

Modified risk associations of lipoproteins and apolipoproteins by chronic low-grade inflammation

INTRODUCTION

Lipoproteins and the apolipoproteins (apo) that they carry are major determinants of cardiovascular diseases (CVD) as well as metabolic, renal and inflammatory chronic disorders either directly or through mediation of risk factors. The notion that elevated low-density lipoprotein cholesterol (LDL-C) and apoB levels are related to the acquisition of CVD and, high-density lipoprotein cholesterol (HDL-C) and apoA-I indicate protection against CVD has been challenged in the past decade. Advanced age, adiposity, ethnicity or impaired glucose intolerance rendered autoimmune activation in an environment of pro-inflammatory state/oxidative stress and may disrupt the linear risk association between lipoproteins. Areas covered: This review summarizes the modified risk associations of lipoproteins and apolipoprotein by an environment of chronic systemic low-grade inflammation with special emphasis on the non-linear relationship of lipoprotein(a) [Lp(a)], a biomarker of renewed interest in cardiometabolic risk. Expert commentary: It seems that autoimmune activation in an environment of pro-inflammatory state/oxidative stress not only disrupts the linear risk association between lipoproteins, but also may cause interference in immunoassays. Hence, methodological improvement in immunoassays and much further research focusing on population segments susceptible to a pro-inflammatory state is necessary for further advances in knowledge.

Blood lipids and lipoproteins in relation to incidence and mortality risks for CVD and cancer in the prospective EPIC-Heidelberg cohort

BACKGROUND

Circulating concentrations of lipid biomarkers are associated with risk of cardiovascular diseases (CVD). The evidence for a relationship with cancer risk, however, is not entirely consistent. This study aims to assess the relationships of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), apolipoprotein (a) (apo(a)), apoB-100, and lipoprotein(a) (Lp(a)) with risk of common cancer forms and total cancer mortality in comparison to incidence and mortality of CVD.

METHODS

We selected a case-cohort sample out of the prospective EPIC-Heidelberg study, including a random subcohort (n = 2739), and cases of cancer (n = 1632), cancer mortality (n = 761), CVD (n = 1070), and CVD mortality (n = 381). Concentrations of lipid biomarkers were measured in pre-diagnostic blood samples. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Prentice-weighted Cox regression models.

RESULTS

High levels of circulating apoB-100 and TG were inversely associated and high HDL-C levels were positively associated with breast cancer risk (highest vs. lowest quartile (Q4 vs. Q1), HR_apoB 0.71, 95% CI 0.52-0.98; HR_TG 0.65, 0.46-0.92; and HR_HDL 1.39, 1.01-1.93). Higher levels of Lp(a) were associated with an increase in prostate cancer risk (Q4 vs. Q1, HR_Lp(a) 1.43, 1.02-2.03) and high levels of apo(a) were associated with a decrease in lung cancer risk (Q4 vs. Q1, HR_apo(a) 0.52, 0.30-0.91). High TC, HDL-C, apo(a), and Lp(a) levels were associated with a reduction in total cancer mortality (Q4 vs. Q1, HR_TC 0.71, 0.54-0.94; HR_HDL 0.67, 0.50-0.91; HR_apo(a) 0.71, 0.54-0.93; and HR_Lp(a) 0.74, 0.57-0.98). All lipid biomarkers were associated with risk of myocardial infarction, whereby TC, apoB-100, TG, and Lp(a) were positively and HLD-C and apo(a) inversely associated with risk. Only high levels of TG were associated with an increased risk of stroke. None of the lipids were associated with risk of colorectal cancer and with risk of CVD mortality after multivariable adjustments.

CONCLUSIONS

This prospective study demonstrates inverse associations of lipid biomarkers with cancer incidence and mortality, with the exception of positive associations of HDL-C and Lp(a) with breast and prostate cancer risk, respectively. Thus, the observed cancer risk pattern clearly differs from the CVD risk pattern.

Genetics of coronary artery disease: discovery, biology and clinical translation

Coronary artery disease is the leading global cause of mortality. Long recognized to be heritable, recent advances have started to unravel the genetic architecture of the disease. Common variant association studies have linked approximately 60 genetic loci to coronary risk. Large-scale gene sequencing efforts and functional studies have facilitated a better understanding of causal risk factors, elucidated underlying biology and informed the development of new therapeutics. Moving forwards, genetic testing could enable precision medicine approaches by identifying subgroups of patients at increased risk of coronary artery disease or those with a specific driving pathophysiology in whom a therapeutic or preventive approach would be most useful.

Lipoprotein(a) and its role in inflammation, atherosclerosis and malignancies

Lipoprotein (a) (Lp(a)) is a modified low-density lipoprotein (LDL) particle with an additional specific apolipoprotein (a), covalently attached to apolipoprotein B‑100 of LDL by a single thioester bond. Increased plasma Lp(a) level is a genetically determined, independent, causal risk factor for cardiovascular disease.

The precise quantification of Lp(a) in plasma is still hampered by mass-sensitive assays, large particle variation, poor standardization and lack of assay comparability.

The physiological functions of Lp(a) include wound healing, promoting tissue repair and vascular remodeling. Similarly to other lipoproteins, Lp(a) is also susceptible for oxidative modifications, leading to extensive formation of pro-inflammatory and pro-atherogenic oxidized phospholipids, oxysterols, oxidized lipid-protein adducts in Lp(a) particles, that perpetuate atherosclerotic lesion progression and intima-media thickening through induction of M1-macrophages, inflammation, autoimmunity and apoptosis. The oxidation-specific epitopes of modified lipoproteins are major targets of pre-immune, natural IgM antibodies, that may attenuate the pro-inflammatory and pro-atherogenic effects of Lp(a).

Although the data are still insufficient, recent studies suggest a potential anti-neoplastic role of Lp(a).

Phenotypic Characterization of Genetically Lowered Human Lipoprotein(a) Levels

BACKGROUND

Genomic analyses have suggested that the LPA gene and its associated plasma biomarker, lipoprotein(a) (Lp[a]), represent a causal risk factor for coronary heart disease (CHD). As such, lowering Lp(a) levels has emerged as a therapeutic strategy. Beyond target identification, human genetics may contribute to the development of new therapies by defining the full spectrum of beneficial and adverse consequences and by developing a dose-response curve of target perturbation.

OBJECTIVES

The goal of this study was to establish the full phenotypic impact of LPA gene variation and to estimate a dose-response curve between genetically altered plasma Lp(a) and risk for CHD.

METHODS

We leveraged genetic variants at the LPA gene from 3 data sources: individual-level data from 112,338 participants in the U.K. Biobank; summary association results from large-scale genome-wide association studies; and LPA gene sequencing results from case subjects with CHD and control subjects free of CHD.

RESULTS

One SD genetically lowered Lp(a) level was associated with a 29% lower risk of CHD (odds ratio [OR]: 0.71; 95% confidence interval [CI]: 0.69 to 0.73), a 31% lower risk of peripheral vascular disease (OR: 0.69; 95% CI: 0.59 to 0.80), a 13% lower risk of stroke (OR: 0.87; 95% CI: 0.79 to 0.96), a 17% lower risk of heart failure (OR: 0.83; 95% CI: 0.73 to 0.94), and a 37% lower risk of aortic stenosis (OR: 0.63; 95% CI: 0.47 to 0.83). We observed no association with 31 other disorders, including type 2 diabetes and cancer. Variants that led to gain of LPA gene function increased the risk for CHD, whereas those that led to loss of gene function reduced the CHD risk.

CONCLUSIONS

Beyond CHD, genetically lowered Lp(a) levels are associated with a lower risk of peripheral vascular disease, stroke, heart failure, and aortic stenosis. As such, pharmacological lowering of plasma Lp(a) may influence a range of atherosclerosis-related diseases.

Lipoprotein(a) and vitamin C impair development of breast cancer tumors in Lp(a)+; Gulo-/- mice

Cancer progression is characterized by loss of extracellular matrix (ECM) integrity, which is a precondition for tumor growth and metastasis. In order to elucidate the precise mechanisms of ECM degradation in cancer we used a genetically modified mouse mimicking two distinct human metabolic features associated with carcinogenesis, the lack of endogenous vitamin C synthesis and the production of human Lp(a). Female Lp(a)+; Gulo(−/−) and control wild-type Balb/c mice without these two metabolic features were orthotopically inoculated with 4T1 breast cancer cells (5×10⁵). The transgenic and control mice were divided into 4 different dietary groups in respect to dietary vitamin C intake: i) low ascorbate intake for 6 weeks; ii) high ascorbate intake for 6 weeks; iii) low ascorbate intake for 3 weeks followed by high ascorbate for 3 weeks; iv) high ascorbate intake for 3 weeks followed by low ascorbate for 3 weeks. After 6 weeks, all wild-type mice developed tumors. In contrast, Lp(a)+; Gulo(−/−) mice developed one third less primary tumors (low ascorbate diet) or no primary tumors at all (high ascorbate diet). Significantly, tumors from Lp(a)+; Gulo(−/−) mice immunostained positively for Lp(a) and their size was inversely proportional to Lp(a) serum levels. The results implicate that Lp(a) may play a role in controlling tumor growth and expansion. The most likely mechanism is the competitive inhibition of plasmin-induced ECM degradation due to the homology of Lp(a) components to plasminogen. The confirmation of this pathomechanism could lead to a universal therapeutic target for the prevention and treatment of cancer.

Evidence-based assessment of lipoprotein(a) as a risk biomarker for cardiovascular diseases - Some answers and still many questions

The present article is aimed at outlining the current state of knowledge regarding the clinical value of lipoprotein(a) (Lp(a)) as a marker of cardiovascular disease (CVD) risk by summarizing the results of recent clinical studies, meta-analyses and systematic reviews. The literature supports the predictive value of Lp(a) on CVD outcomes, although the effect size is modest. Lp(a) would also appear to have an effect on cerebrovascular outcomes, however the effect appears even smaller than that for CVD outcomes. Consideration of apolipoprotein(a) (apo(a)) isoforms and LPA genetics in relation to the simple assessment of Lp(a) concentration may enhance clinical practice in vascular medicine. We also describe recent advances in Lp(a) research (including therapies) and highlight areas where further research is needed such as the measurement of Lp(a) and its involvement in additional pathophysiological processes.

Puzzling role of genetic risk factors in human longevity: "risk alleles" as pro-longevity variants

Complex diseases are major contributors to human mortality in old age. Paradoxically, many genetic variants that have been associated with increased risks of such diseases are found in genomes of long-lived people, and do not seem to compromise longevity. Here we argue that trade-off-like and conditional effects of genes can play central role in this phenomenon and in determining longevity. Such effects may occur as result of: (i) antagonistic influence of gene on the development of different health disorders; (ii) change in the effect of gene on vulnerability to death with age (especially, from “bad” to “good”); (iii) gene–gene interaction; and (iv) gene–environment interaction, among other factors. A review of current knowledge provides many examples of genetic factors that may increase the risk of one disease but reduce chances of developing another serious health condition, or improve survival from it. Factors that may increase risk of a major disease but attenuate manifestation of physical senescence are also discussed. Overall, available evidence suggests that the influence of a genetic variant on longevity may be negative, neutral or positive, depending on a delicate balance of the detrimental and beneficial effects of such variant on multiple health and aging related traits. This balance may change with age, internal and external environments, and depend on genetic surrounding. We conclude that trade-off-like and conditional genetic effects are very common and may result in situations when a disease “risk allele” can also be a pro-longevity variant, depending on context. We emphasize importance of considering such effects in both aging research and disease prevention.

Alteration of serum lipid profile and its prognostic value in head and neck squamous cell carcinoma

BACKGROUND

Several serum lipid components have been implicated in the development of cancer. However, the prognostic significance of serum lipid components in head and neck squamous cell carcinoma is unknown. Here, we investigated the predictive value of serum lipid profile at diagnosis and in the overall survival of the patients.

METHODS

The study population consists of 136 pathologically confirmed head and neck squamous cell carcinoma cases diagnosed between years 2009 and 2014 at a tertiary medical center. Levels of preoperative serum lipid component's total cholesterol, triglycerides, high-density lipoprotein, low-density lipoprotein, apolipoprotein A, apolipoprotein B, and lipoprotein (a) were compared between patients and normal controls matched for age and gender. Serum lipid profiles and their association with clinical parameters were analyzed. The effects of the serum lipid components on survival were examined using the proportional hazards regression model to estimate hazard ratio.

RESULTS

Significant lower levels of cholesterol, low-density lipoprotein, apolipoprotein A, and apolipoprotein B were found in patients with oral cancer (P < 0.0001). However, a significantly higher level of lipoprotein (a) was found in the cancer group (P < 0.0001). Patients with higher lipoprotein (a) had significantly shorter overall survival than those with lower lipoprotein (a) (P = 0.0042). Multivariate analysis showed that both higher lipoprotein (a) and lymph node metastasis are independent prognostic factors in the patient population (P < 0.01).

CONCLUSION

A higher lipoprotein (a) was associated with poorer prognosis and might be a novel marker in patients with head and neck squamous cell carcinoma.

The involvement of multiple thrombogenic and atherogenic markers in premature coronary artery disease

OBJECTIVE

To examine the association of atherogenic and thrombogenic markers and lymphotoxin-alfa gene mutations with the risk of premature coronary disease.

METHODS

This cross-sectional, case-control, age-adjusted study was conducted in 336 patients with premature coronary disease (<50 years old) and 189 healthy controls. The control subjects had normal clinical, resting, and exercise stress electrocardiographic assessments. The coronary disease group patients had either angiographically documented disease (>50% luminal reduction) or a previous myocardial infarction. The laboratory data evaluated included thrombogenic factors (fibrinogen, protein C, protein S, and antithrombin III), atherogenic factors (glucose and lipid profiles, lipoprotein(a), and apolipoproteins AI and B), and lymphotoxin-alfa mutations. Genetic variability of lymphotoxin-alfa was determined by polymerase chain reaction analysis.

RESULTS

Coronary disease patients exhibited lower concentrations of HDL-cholesterol and higher levels of glucose, lipoprotein(a), and protein S. The frequencies of AA, AG, and GG lymphotoxin-alfa mutation genotypes were 55.0%, 37.6%, and 7.4% for controls and 42.7%, 46.0%, and 11.3% for coronary disease patients (p = 0.02), respectively. Smoking, dyslipidemia, family history, and lipoprotein(a) and lymphotoxin-alfa mutations in men were independent variables associated with coronary disease. The area under the curve (C-statistic) increased from 0.779 to 0.802 (p<0.05) with the inclusion of lipoprotein(a) and lymphotoxin-alfa mutations in the set of conventional risk factors.

CONCLUSIONS

The inclusion of lipoprotein(a) and lymphotoxin-alfa mutations in the set of conventional risk factors showed an additive but small increase in the risk prediction of premature coronary disease.

Inverse association between serum lipoprotein(a) and cerebral hemorrhage in the Japanese population

INTRODUCTION

Although lipoprotein(a) (Lp(a)) is involved in cardiometabolic disease processes, the association between serum Lp(a) and stroke and/or its subtypes has not yet been elucidated among Japanese people. This study investigated the association between Lp(a) and the incidence of stroke and/or its subtypes in the general Japanese population.

MATERIALS AND METHODS

This population-based prospective cohort study included 10,494 community-dwelling participants (4,030 males/6,464 females). The incidence of stroke and its subtypes was the primary outcome. The subjects were divided into tertiles based on their Lp(a) levels, and the risk of all stroke and stroke subtypes was examined using Cox's proportional hazard model.

RESULTS

A total of 393 subjects (199 males and 194 females) with stroke were identified during a follow-up duration of 10.7years. The multivariate-adjusted hazard ratios for all stroke events were 0.55 (95% confidence interval: 0.38-0.81) and 0.69 (0.49-0.99) in the 2nd (9-19mg/dl) and 3rd tertiles (≥20mg/dl) of Lp(a) in reference to the 1st tertile (<9mg/dl) in males, and 0.85 (0.59-1.24) and 0.76 (0.52-1.11) in 2nd (10-22mg/dl) and 3rd tertiles (≥23mg/dl) of Lp(a) in reference to the 1st tertile (<10mg/dl) in females. The multivariate-adjusted hazard ratios for cerebral hemorrhage were 0.26 (0.10-0.67) and 0.34 (0.15-0.76) in the 2nd and 3rd tertiles of Lp(a) in reference to the 1st tertile in males, and were 0.48 (0.23-1.04) and 0.44 (0.21-0.96) in the 2nd and 3rd tertiles of Lp(a) in females.

CONCLUSIONS

Lp(a) was associated with the incidence of cerebral hemorrhage in the general Japanese population, particularly among males, while a similar trend was seen among females. A low Lp(a) level may be a marker of the risk of cerebral hemorrhage in this population.