Low-Density Lipoprotein Cholesterol Level cannot be too Low: Considerations from Clinical Trials, Human Genetics, and Biology

Familial hypercholesterolemia with special focus on Japan

Familial hypercholesterolemia (FH) is an inherited disorder characterized by increased low-density lipoprotein LDL) cholesterol and atherosclerotic cardiovascular disease. Although initial genetic analysis linked FH to LDL receptor mutations, subsequent work demonstrated that a gain-of-function mutation in the proprotein convertase subtilisin/kexin type 9 (PCSK9), which causes LDL-R degradation, was shown to be the cause of FH. In this review, we describe the history of research on FH, its clinical phenotyping and genotyping and advances in treatment with special focus on Japan.

Partitioned polygenic risk scores identify distinct types of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) encompasses an excess of triglycerides in the liver, which can lead to cirrhosis and liver cancer. While there is solid epidemiological evidence of MASLD coexisting with cardiometabolic disease, several leading genetic risk factors for MASLD do not increase the risk of cardiovascular disease, suggesting no causal relationship between MASLD and cardiometabolic derangement. In this work, we leveraged measurements of visceral adiposity and identified 27 novel genetic loci associated with MASLD. Among these loci, we replicated 6 in several independent cohorts. Next, we generated two partitioned polygenic risk scores (PRS) based on the mechanism of genetic association with MASLD encompassing intra-hepatic lipoprotein retention. The two PRS suggest the presence of at least two distinct types of MASLD, one confined to the liver resulting in a more aggressive liver disease and one that is systemic and results in a higher risk of cardiometabolic disease.

Association between remnant cholesterol and incident atherosclerotic cardiovascular disease, heart failure, and atrial fibrillation

BACKGROUND

It remains unclear if remnant cholesterol is associated with atherosclerotic cardiovascular disease (ASCVD) (myocardial infarction, angina pectoris and stroke), heart failure (HF), and atrial fibrillation (AF) under primary prevention settings.

OBJECTIVE

We aimed to clarify this issue among a general population without a history of ASCVD, HF or AF.

METHODS

Analyses were conducted with a nationwide health claims database collected in the JMDC Claims Database between 2005 and 2022 (n = 1,313,722; median age, 42 years; 54.6% men). We assessed the associations between remnant cholesterol calculated as total cholesterol minus HDL cholesterol minus LDL cholesterol and composite CVD outcomes, including, ASCVD, HF, and AF using Cox proportional hazard model, dividing the individuals into tertiles of remnant cholesterol (T1-T3).

RESULTS

The mean follow-up duration was 3.0 years. In total, 43,755 events were recorded. Remnant cholesterol was significantly associated with composite CVD outcomes after adjustments (T3 vs T1: hazard ratio [HR]; 1.07, 95% confidence interval [CI]: 1.04-1.10, p-trend<0.001). Remnant cholesterol was associated with myocardial infarction (T3 vs T1:HR: 1.20, 95% CI: 1.06-1.34, p-trend=0.002), angina pectoris (T3 vs T1:HR: 1.09, 95% CI: 1.05-1.14, p-trend<0.001), stroke (T3 vs T1:HR: 1.08, 95% CI: 1.02-1.14, p-trend=0.007), and HF (T3 vs T1:HR: 1.08, 95% CI: 1.04-1.12, p-trend<0.001), while we found a marginal inverse association between remnant cholesterol and AF (T3 vs T1:HR: 0.92, 95% CI: 0.86-1.00, p-trend=0.054).

CONCLUSION

Remnant cholesterol was positively associated with ASCVD and HF, while we found a marginal inverse association between remnant cholesterol and AF.

Case report: Unusual coexistence between familial hypercholesterolemia and familial hypobetalipoproteinemia

Type 1 familial hypobetalipoproteinemia (FHBL1), characterized by low levels of apolipoprotein B (ApoB)-containing lipoproteins, elevation of transaminases, and hepatic steatosis, is a rare disease the prevalence of which is 1 in 3,000 among general population. Here we report an extremely rare family where phenotypes of familial hypercholesterolemia (FH) are canceled by coexistence of FHBL1 caused by an truncating mutation in apolipoprotein B (APOB).

Human genetics and its impact on cardiovascular disease

Cardiovascular disease (CVD) is a major cause of death worldwide. Given that CVD is a highly heritable trait, researchers have attempted to fully understand the genetic basis of CVD for a long time. The human genome comprises 3,100 Mbp per haploid genome and 6,200 Mbp in total (diploid genome). However, there is a tendency for rare genetic variations to exhibit a large effect size, whereas common genetic variations have a small effect on diseases, because of natural selection. In this sense, dividing genetic variations into two groups based on allele frequency (and effect sizes on diseases) is a good idea. We know there are several important genes (especially lipid-related genes) in which rare genetic variations are apparently associated with CVD risk, while a polygenic risk score comprising common genetic variations appears to work quite well among general populations. That information can be used not only for risk stratification but also for discoveries for novel pharmacologic targets. In this review article, we provide the important and simple idea that human genetics is important for CVD because it is a highly heritable trait, and we believe that it will lead to precision medicine in this field.

Individualized Treatment for Patients With Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is one of the most common and, therefore, important inherited disorders in preventive cardiology. This disease is mainly caused by a single pathogenic mutation in the low-density lipoprotein receptor or its associated genes. Moreover, it is correlated with a high risk of cardiovascular disease. However, the phenotype severity even in this monogenic disease significantly varies. Thus, the current study aimed to describe FH and its importance and the factors (inherited and acquired) contributing to differences in phenotype severity. Different lipid-modification therapies according to these factors can lead to individualized treatments, which are also essential in the general populations.

Effects of artificial intelligence-SsupporTed Automated NutRiTional Intervention on LDL cholesterol Control in Patients with Familial Hypercholesterolaemia (iSTART-FH): protocol for a randomised controlled trial

Introduction

Familial hypercholesterolaemia (FH) is an autosomal dominant inherited genetic disease that has an extremely elevated cardiovascular risk because of their significantly elevated low-density lipoprotein (LDL) cholesterol. Nutritional intervention is needed in improving LDL cholesterol control in patients with FH but requires a considerable burden in manpower. Artificial intelligence (AI)-supported and mobile-supported nutritional intervention using this technique may be an alternative approach to traditional nutritional counselling in person. This study aims to test the hypothesis that AI-supported nutritional counselling is more effective in reducing LDL cholesterol than the in-person, face-to-face method in terms of improving LDL cholesterol control in patients with FH.

Methods and analysis

This is a single-centre, unblinded, cross-over, randomised controlled study comparing the efficacy of AI-supported automated nutrition therapy with that of conventional human nutrition counselling in patients with FH. Patients with FH are recruited and randomly assigned to AI-supported nutrition counselling (n=30) and to face-to face nutrition counselling (n=30). We are using an Asken, a mobile application that has been specially modified for this study so that it follows the recommendations by the Japan Atherosclerosis Society. We started patient recruitment on 1 September 2020, and is scheduled to continue until 31 December 2022.

Ethics and dissemination

This study is being conducted in compliance 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 study protocol was approved by the Institutional Review Board of Kanazawa University on 13 April 2020 (IRB no. 2623-3); all recruited patients are required to provide written informed consent. We will disseminate the final results at international conferences and in a peer-reviewed journal.

Trial registration number

UMIN000040198.

Effect of Cumulative Exposure to Low-Density Lipoprotein-Cholesterol on Cardiovascular Events in Patients With Familial Hypercholesterolemia

BACKGROUND

Recent studies suggest that cumulative exposure to low-density lipoprotein-cholesterol (LDL-C) leads to the development of atherosclerotic cardiovascular disease (ASCVD). However, few studies have investigated whether this link extends to individuals with familial hypercholesterolemia (FH), a relevant patient population.Methods and Results:We retrospectively investigated the health records of 1,050 patients with clinical FH diagnosis between April 1990 and March 2019. We used Cox proportional hazards models adjusted for established ASCVD risk factors to assess the association between cholesterol-year-score and major adverse cardiovascular events (MACEs), including death from any cause or hospitalization due to ASCVD events. Cholesterol-year-score was calculated as LDL-C max × [age at diagnosis/statin initiation] + LDL-C at inclusion × [age at inclusion - age at diagnosis/statin initiation]. The median follow-up period for MACE evaluation was 12.3 (interquartile range, 9.1-17.5) years, and 177 patients experienced MACEs during the observation period. Cholesterol-year-score was significantly associated with MACEs (hazard ratio, 1.35; 95% confidence interval, 1.07-1.53; P=0.0034, per 1,000 mg-year/dL), independent of other traditional risk factors including age and LDL-C, based on cross-sectional assessment. Cholesterol-year-score improved the discrimination ability of other traditional risk factors for ASCVD events (C-index, 0.901 vs. 0.889; P=0.00473).

CONCLUSIONS

Cumulative LDL-C exposure was strongly associated with MACEs in Japanese patients with FH, warranting early diagnosis and treatment initiation in these patients.

Current Diagnosis and Management of Abetalipoproteinemia

Abetalipoproteinemia (ABL) is a rare autosomal recessive disorder caused by biallelic pathogenic mutations in the MTTP gene. Deficiency of microsomal triglyceride transfer protein (MTTP) abrogates the assembly of apolipoprotein (apo) B-containing lipoprotein in the intestine and liver, resulting in malabsorption of fat and fat-soluble vitamins and severe hypolipidemia. Patients with ABL typically manifest steatorrhea, vomiting, and failure to thrive in infancy. The deficiency of fat-soluble vitamins progressively develops into a variety of symptoms later in life, including hematological (acanthocytosis, anemia, bleeding tendency, etc.), neuromuscular (spinocerebellar ataxia, peripheral neuropathy, myopathy, etc.), and ophthalmological symptoms (e.g., retinitis pigmentosa). If left untreated, the disease can be debilitating and even lethal by the third decade of life due to the development of severe complications, such as blindness, neuromyopathy, and respiratory failure. High dose vitamin supplementation is the mainstay for treatment and may prevent, delay, or alleviate the complications and improve the prognosis, enabling some patients to live to the eighth decade of life. However, it cannot fully prevent or restore impaired function. Novel therapeutic modalities that improve quality of life and prognosis are awaited. The aim of this review is to 1) summarize the pathogenesis, clinical signs and symptoms, diagnosis, and management of ABL, and 2) propose diagnostic criteria that define eligibility to receive financial support from the Japanese government for patients with ABL as a rare and intractable disease. In addition, our diagnostic criteria and the entry criterion of low-density lipoprotein cholesterol (LDL-C) ＜15 mg/dL and apoB ＜15 mg/dL can be useful in universal or opportunistic screening for the disease. Registry research on ABL is currently ongoing to better understand the disease burden and unmet needs of this life-threatening disease with few therapeutic options.

Challenges of Precision Medicine for Atherosclerotic Cardiovascular Disease Based on Human Genome Information

Precision or personalized medicine is currently gaining a lot of attention. Clinical evidence for its effectiveness has been established based on randomized clinical trials accounting for classical risk factors, such as hypertension, diabetes, and serum lipids. However, besides such classical risk factors, the genetic background should be considered, at least for heritable traits, including atherosclerotic cardiovascular disease (ASCVD). Such classical risk factors are almost always incidents that have already occurred in which it may be too late to start treatment, instead of indicators of presymptomatic state. Human genome information is associated with most traits, including ASCVD. Two methods of implementing precision medicine for ASCVD using human genome information are currently being investigated: the use of rare genetic variations that have large effect sizes and polygenic risk scores that are composed of multiple common genetic variations. This review article emphasizes the importance of clinical as well as genetic diagnoses when implementing precision medicine. Precision medicine should be considered based on comprehensive genetic analyses, encompassing rare to common genetic variations.

Familial Hypercholesterolemia: A Narrative Review on Diagnosis and Management Strategies for Children and Adolescents

Familial hypercholesterolemia (FH) is a relatively common inherited disorder caused by deleterious mutation(s) in the low-density lipoprotein (LDL) receptor or its associated genes. Given its nature as a heritable disease, any useful screening scheme, including universal, and cascade screening, allows for the early identification of patients with FH. Another important aspect to note is that early diagnosis associated with appropriate treatment can promote better prognosis. However, most clinical diagnostic criteria for adults have adopted clinical elements, such as physical xanthomas and family history, both of which are usually obscure and/or difficult to obtain in children and adolescents. Moreover, LDL cholesterol levels fluctuating considerably during adolescence, hindering the timely diagnosis of FH. In addition, recent advancements in human genetics have revealed several types of FH, including conventional monogenic FH, polygenic FH caused by common single nucleotide variations (SNV) accumulation associated with elevated LDL cholesterol, and oligogenic FH with multiple deleterious genetic variations leading to substantially elevated LDL cholesterol. The aforementioned findings collectively suggest the need for amassing information related to genetics and imaging, in addition to classical clinical elements, for the accurate diagnosis of FH in this era of personalized medicine. The current narrative review summarizes the current status of the clinical and genetic diagnosis of FH in children and adolescents, as well as provide useful management strategies for FH in children and adolescents based on currently available clinical evidence.