Relation of Serum Lipoprotein(a) Levels to Lipoprotein and Apolipoprotein Profiles and Atherosclerotic Diseases in Japanese Patients with Heterozygous Familial Hypercholesterolemia: Familial Hypercholesterolemia Expert Forum (FAME) Study

Serum Lipoprotein(a) Levels and Their Association with Atherosclerotic Cardiovascular Disease in Japan

AIMS

To investigate the distribution of lipoprotein(a) (Lp(a)) and its association with atherosclerotic cardiovascular disease (ASCVD) in Japanese patients at high risk for ASCVD using a health insurance database.

METHODS

Between July 2013 and June 2021, patients eligible for ASCVD prevention according to the 2017 Japan Atherosclerosis Society (JAS) guidelines with documented Lp(a) test results were extracted from the Medical Data Vision claims database and divided into three groups: primary prevention high-risk (Group I), secondary prevention (Group II) and secondary prevention high-risk (Group III). Data on lipid levels, cardiovascular morbidity risk factors and lipid-lowering treatments were extracted.

RESULTS

Of 700,580 patients with documented low-density lipoprotein cholesterol (LDL-C), 2,967 (0.42%) were tested for Lp(a). In 2,170 eligible patients, the median [interquartile range] serum concentration of Lp(a) was 13.9 [7.5-24.6] mg/dL, with 151 patients (7.0%) above the recommended risk threshold of ≥ 50 mg/dL. Lp(a) levels increased with risk across all prevention groups. Being in the highest Lp(a) quintile (Q5) was associated with an increased frequency of ASCVD (28.9% versus 18.9% in the lowest quintile (Q1) for unstable angina; 18.7% versus 10.1% for myocardial infarction; 27.9% versus 17.0% for ischemic stroke). In the secondary prevention groups, the proportion of patients meeting an LDL-C target of ＜70 mg/dL decreased from 30.2% in Q1 to 19.0% in Q5 for Group II and from 32.9% to 16.3% for Group III.

CONCLUSIONS

Despite a high prevalence of Lp(a) ≥ 50mg/dL in Japanese patients at high risk for ASCVD, it found that the Lp(a) testing rate was very low.

Impact of High-Density Lipoprotein Function, Rather Than High-Density Lipoprotein Cholesterol Level, on Cardiovascular Disease Among Patients With Familial Hypercholesterolemia

BACKGROUND

Recently, the function of high-density lipoprotein (HDL), rather than the HDL cholesterol (HDL-C) level, has been attracting more attention in risk prediction for coronary artery disease (CAD).

METHODS AND RESULTS

Patients with clinically diagnosed familial hypercholesterolemia (FH; n=108; male/female, 51/57) were assessed cross-sectionally. Serum cholesterol uptake capacity (CUC) levels were determined using our original cell-free assay. Linear regression was used to determine associations between CUC and clinical variables, including low-density lipoprotein cholesterol and the carotid plaque score. Multivariable logistic regression analysis was used to test factors associated with the presence of CAD. Among the 108 FH patients, 30 had CAD. CUC levels were significantly lower among patients with than without CAD (median [interquartile range] 119 [92-139] vs. 142 [121-165] arbitrary units [AU]; P=0.0004). In addition, CUC was significantly lower in patients with Achilles tendon thickness ≥9.0 mm than in those without Achilles tendon thickening (133 [110-157] vs. 142 [123-174] AU; P=0.047). Serum CUC levels were negatively correlated with the carotid plaque score (Spearman's r=0.37; P=0.00018). Serum CUC levels were significantly associated with CAD, after adjusting for other clinical variables (odds ratio=0.86, 95% CI=0.76-0.96, P=0.033), whereas HDL-C was not.

CONCLUSIONS

HDL function, assessed by serum CUC level, rather than HDL-C level, adds risk stratification information among FH patients.

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.

Familial Hypercholesterolemia and Lipoprotein(a): A Gordian Knot in Cardiovascular Prevention

Familial hypercholesterolemia (FH) is the most frequent genetic disorder resulting in increased low-density lipoprotein cholesterol (LDL-C) levels from childhood, leading to premature atherosclerotic cardiovascular disease (ASCVD) if left untreated. FH diagnosis is based on clinical criteria and/or genetic testing and its prevalence is estimated as being up to 1:300,000−400,000 for the homozygous and ~1:200−300 for the heterozygous form. Apart from its late diagnosis, FH is also undertreated, despite the available lipid-lowering therapies. In addition, elevated lipoprotein(a) (Lp(a)) (>50 mg/dL; 120 nmol/L), mostly genetically determined, has been identified as an important cardiovascular risk factor with prevalence rate of ~20% in the general population. Novel Lp(a)-lowering therapies have been recently developed and their cardiovascular efficacy is currently investigated. Although a considerable proportion of FH patients is also diagnosed with high Lp(a) levels, there is a debate whether these two entities are associated. Nevertheless, Lp(a), particularly among patients with FH, has been established as a significant cardiovascular risk factor. In this narrative review, we present up-to-date evidence on the pathophysiology, diagnosis, and treatment of both FH and elevated Lp(a) with a special focus on their association and joint effect on ASCVD risk.

How Can We Identify Very High-Risk Heterozygous Familial Hypercholesterolemia?

Heterozygous familial hypercholesterolemia (HeFH) is a genetic disorder that elevates low-density lipoprotein cholesterol and increases the risk of premature atherosclerotic cardiovascular disease (ASCVD). However, despite their atherogenic lipid profiles, the cardiovascular risk of HeFH varies in each individual. Their variety of phenotypic features suggests the need for better risk stratification to optimize their therapeutic management. The current review summarizes three potential approaches, including (1) definition of familial hypercholesterolemia (FH)-related risk scores, (2) genetic analysis, and (3) biomarkers. The International Atherosclerosis Society has recently proposed a definition of severe FH to identify very high-risk HeFH subjects according to their clinical characteristics. Furthermore, published studies have shown the association of FH-related genetic phenotypes with ASCVD, which indicates the genetic analysis's potential to evaluate individual cardiovascular risks. Biomarkers reflecting disease activity have been considered to predict the formation of atherosclerosis and the occurrence of ASCVD in HeFH subjects. Incorporating these risk stratifications will be expected to allocate adequate intensity of lipid-lowering therapies in HeFH subjects, which ultimately improves cardiovascular outcomes.

Assessment of Associations Between Serum Lipoprotein (a) Levels and Atherosclerotic Vascular Diseases in Hungarian Patients With Familial Hypercholesterolemia Using Data Mining and Machine Learning

Background and aims: Premature mortality due to atherosclerotic vascular disease is very high in Hungary in comparison with international prevalence rates, though the estimated prevalence of familial hypercholesterolemia (FH) is in line with the data of other European countries. Previous studies have shown that high lipoprotein(a)- Lp(a) levels are associated with an increased risk of atherosclerotic vascular diseases in patients with FH. We aimed to assess the associations of serum Lp(a) levels and such vascular diseases in FH using data mining methods and machine learning techniques in the Northern Great Plain region of Hungary.

Methods: Medical records of 590,500 patients were included in our study. Based on the data from previously diagnosed FH patients using the Dutch Lipid Clinic Network scores (≥7 was evaluated as probable or definite FH), we trained machine learning models to identify FH patients.

Results: We identified 459 patients with FH and 221 of them had data available on Lp(a). Patients with FH had significantly higher Lp(a) levels compared to non-FH subjects [236 (92.5; 698.5) vs. 167 (80.2; 431.5) mg/L, p < .01]. Also 35.3% of FH patients had Lp(a) levels >500 mg/L. Atherosclerotic complications were significantly more frequent in FH patients compared to patients without FH (46.6 vs. 13.9%). However, contrary to several other previous studies, we could not find significant associations between serum Lp(a) levels and atherosclerotic vascular diseases in the studied Hungarian FH patient group.

Conclusion: The extremely high burden of vascular disease is mainly explained by the unhealthy lifestyle of our patients (i.e., high prevalence of smoking, unhealthy diet and physical inactivity resulting in obesity and hypertension). The lack of associations between serum Lp(a) levels and atherosclerotic vascular diseases in Hungarian FH patients may be due to the high prevalence of these risk factors, that mask the deleterious effect of Lp(a).

Prospective Registry Study of Primary Dyslipidemia (PROLIPID): Rationale and Study Design

Introduction: Primary dyslipidemias are inherited disorders in plasma lipoprotein metabolism that lead to serious cardiovascular and other complications. The Japanese Ministry of Health, Labor and Welfare (MHLW) covers medical expenses, under the Research Program on Rare and Intractable Diseases, for homozygous familial hypercholesterolemia (FH), familial chylomicronemia, sitosterolemia, cerebrotendinous xanthomatosis, lecithin:cholesterol acyltransferase deficiency, Tangier disease, and abetalipoproteinemia. Apolipoprotein A1 deficiency, heterozygous FH, and type III hyperlipoproteinemia are covered by the MHLW Pediatric Chronic Disease Program. Heterozygous FH and type III hyperlipoproteinemia are also important for their relatively common prevalence and, accordingly, high impact on Japanese public health by significant contribution to the overall prevalence of cardiovascular diseases. Therefore, a systemic survey of these diseases is mandatory to estimate their actual situation, such as prevalence, clinical manifestations, and prognoses among the Japanese population. The impact of these rare and intractable diseases on cardiovascular and other complications will likely be higher among Japanese people than other ethnicities because the general Japanese population has many cardioprotective aspects. The current study intends to conduct a multicenter registry of these diseases to assess their demographics and clinical features comprehensively.

Methods and Analysis: The Prospective Registry Study of Primary Dyslipidemia is a registry-based prospective, observational, multicenter cohort study in Japan, enrolling patients who fulfill the Japanese clinical criteria of the primary dyslipidemias listed above, from 26 participating institutes from August 2015 to March 2023. A total of 1,000 patients will be enrolled in the study and followed for 10 years. Clinical parameters are collected, including physical and laboratory findings, genetic analysis, drugs, lifestyle management, and clinical events, especially cardiovascular events. The primary endpoint of this study is the new onset of cardiovascular disease and acute pancreatitis, and the secondary endpoint is death from any causes.

Ethics and Dissemination: This study complies with the Declaration of Helsinki, the Ethical Guidelines for Medical and Health Research Involving Human Subjects, and all other applicable laws and guidelines in Japan. The institutional review boards have approved this study protocol at all participating institutes. The final results are to be published at appropriate international conferences and in peer-reviewed journals.