Population specific genetic heterogeneity of familial hypercholesterolemia in South Africa

Prevention of Cardiovascular Burden in COVID-19 Patients Suffering from Familial Hypercholesterolemia: A Global Challenge

A recent meta-analysis of over 20,000 individuals showed that hospitalized COVID-19 patients with acute myocardial injury had more than fourfold higher mortality than those without such injury. Since the COVID-19 pandemic exacerbates already existing health inequalities, there is an urgent need to create measures to protect the most vulnerable patient groups, including those with a pre-existing increased risk of atherosclerotic cardiovascular disease (ASCVD). A typical example is familial hypercholesterolemia (FH), a common genetic disease affecting over 30 million individuals worldwide. If left untreated or undertreated, FH patients suffer from complications of premature ASCVD, such as acute coronary syndromes, resulting in acute myocardial injury/infarction. A recent population-based analysis provided strong evidence suggesting that COVID-19 poses an even higher risk for myocardial injury in FH patients. From the long-term preventive point of view, it is important to note that, in addition to the acutely elevated risk of myocardial injury, an elevated risk of ASCVD and its complications will persist after COVID-19. The decline in outpatient preventive care during the pandemic is likely to influence ASCVD risk and outcomes, particularly in high-risk patients, such as those with FH. This commentary aims to raise global awareness of the challenges that clinicians treating FH patients continue to face during the COVID-19 pandemic, with two low- to middle-income countries, South Africa and Brazil, serving as examples.

Founder variants and population genomes-Toward precision medicine

Human migration and community specific cultural practices have contributed to founder events and enrichment of the variants associated with genetic diseases. While many founder events in isolated populations have remained uncharacterized, the application of genomics in clinical settings as well as for population scale studies in the recent years have provided an unprecedented push towards identification of founder variants associated with human health and disease. The discovery and characterization of founder variants could have far reaching implications not only in understanding the history or genealogy of the disease, but also in implementing evidence based policies and genetic testing frameworks. This further enables precise diagnosis and prevention in an attempt towards precision medicine. This review provides an overview of founder variants along with methods and resources cataloging them. We have also discussed the public health implications and examples of prevalent disease associated founder variants in specific populations.

Novel PCSK9 (Proprotein Convertase Subtilisin Kexin Type 9) Variants in Patients With Familial Hypercholesterolemia From Cape Town

OBJECTIVE

Familial hypercholesterolemia (FH) is characterized by elevated low-density lipoprotein-cholesterol and markedly increased cardiovascular risk. In patients with a genetic diagnosis, low-density lipoprotein receptor (LDLR) mutations account for >90% of cases, apolipoprotein B (APOB) mutations for ≈5% of cases, while proprotein convertase subtilisin kexin type 9 (PCSK9) gain of function mutations are rare (<1% of cases). We aimed to evaluate the functional impact of several novel PCSK9 variants in a cohort of patients with FH by genetic cascade screening and in vitro functionality assays. Approach and Results: Patients with clinically diagnosed FH underwent genetic analysis of LDLR, and if negative, sequential testing of APOB and PCSK9. We analyzed cosegregation of hypercholesterolemia with novel PCSK9 variants. Gain of function status was determined by in silico analyses and validated by in vitro functionality assays. Among 1055 persons with clinical FH, we identified nonsynonymous PCSK9 variants in 27 (2.6%) patients and 7 of these carried one of the 4 previously reported gain of function variants. In the remaining 20 patients with FH, we identified 7 novel PCSK9 variants. The G516V variant (c.1547G>T) was found in 5 index patients and cascade screening identified 15 additional carriers. Low-density lipoprotein-cholesterol levels were higher in these 15 carriers compared with the 27 noncarriers (236±73 versus 124±35 mg/dL; P<0.001). In vitro studies demonstrated the pathogenicity of the G516V variant.

CONCLUSIONS

In our study, 1.14% of cases with clinical FH were clearly attributable to pathogenic variants in PCSK9. Pathogenicity is established beyond doubt for the G516V variant.

Cascade Screening for Familial Hypercholesterolemia in South Africa: The Wits FIND-FH Program

OBJECTIVE

Due to gene founder effects, familial hypercholesterolemia (FH) has a prevalence of ≈1:80 in populations of Afrikaner ancestry and is a major contributor to premature atherosclerotic cardiovascular disease in South Africans of Jewish and Indian descent. No systematic program exists to identify these families. Furthermore, information regarding FH prevalence in Black Africans is sparse. The Wits FIND-FH program was initiated in late 2016 to address these issues. Approach and Results: Based on index subjects with definite or probable FH, first-degree relatives were contacted, informed consent obtained, and targeted medical history, physical examination, and blood samples collected. In patients with likely FH using the Simon Broome criteria, DNA analysis for LDLR (low-density lipoprotein receptor), APOB (apolipoprotein B), PCSK9 (proprotein convertase subtilisin/kexin type 9), and LDLRAP1 (LDLR adaptor protein 1) variants was analyzed by next-generation sequencing. Of the initial 700 subjects screened of whom 295 (42%) were index cases, 479 (68.4%) were clinically diagnosed with probable or definite FH. Genetic analysis confirmed 285 of 479 (59.5%) as having variants consistent with FH. Three subjects met the clinical diagnosis for homozygous FH, but DNA analysis revealed a further 34 patients, including 4 Black African subjects, with ≥2 FH-causing variants.

CONCLUSIONS

Using phenotype cascade screening, the Wits FIND-FH program has screened an average of 30 subjects monthly of whom 68% had a clinical diagnosis of FH with ≈60% genetically confirmed. The program is identifying a small but growing number of Black South Africans with FH. Interestingly, 37 subjects (7.7%) who underwent DNA testing were found to have ≥2 FH-causing variants.

PCSK9 Inhibitors: From Nature’s Lessons to Clinical Utility

Background:

Proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors are a novel class of non-statin lipid lowering therapy that reduce LDL-cholesterol by 50 - 60%. PCSK9 inhibitors decrease LDL-cholesterol by preventing intracellular degradation of LDL receptors; subsequently, a greater number of LDL-receptors are available on the cell surface to extract circulating LDL.

Objective:

To describe the origins of PCSK9 inhibitors and their current use in clinical practice.

Methods:

We performed a narrative review of the PCSK9 inhibitor class of drugs.

Results:

Current data indicate that PCSK9 inhibitors effectively reduce LDL-cholesterol and are well tolerated and safe. PCSK9 inhibitors have also been shown to reduce cardiovascular event rates in patients with stable atherosclerotic cardiovascular disease and in patients with a recent (up to one year) acute coronary syndrome. Given the costs, chronicity of the treatment and the potential budget impact, PCSK9 inhibitors are often limited to patients with the highest absolute risk for major adverse cardiovascular events despite optimal treatment with high-intensity statin and ezetimibe.

Conclusion:

PCSK9 inhibitors have a favorable safety, efficacy and tolerability profile. Postmarketing safety surveillance and real-world studies are needed to further support the long-term safety profile of this class of medicine.

Overview of the current status of familial hypercholesterolaemia care in over 60 countries - The EAS Familial Hypercholesterolaemia Studies Collaboration (FHSC)

BACKGROUND AND AIMS

Management of familial hypercholesterolaemia (FH) may vary across different settings due to factors related to population characteristics, practice, resources and/or policies. We conducted a survey among the worldwide network of EAS FHSC Lead Investigators to provide an overview of FH status in different countries.

METHODS

Lead Investigators from countries formally involved in the EAS FHSC by mid-May 2018 were invited to provide a brief report on FH status in their countries, including available information, programmes, initiatives, and management.

RESULTS

63 countries provided reports. Data on FH prevalence are lacking in most countries. Where available, data tend to align with recent estimates, suggesting a higher frequency than that traditionally considered. Low rates of FH detection are reported across all regions. National registries and education programmes to improve FH awareness/knowledge are a recognised priority, but funding is often lacking. In most countries, diagnosis primarily relies on the Dutch Lipid Clinics Network criteria. Although available in many countries, genetic testing is not widely implemented (frequent cost issues). There are only a few national official government programmes for FH. Under-treatment is an issue. FH therapy is not universally reimbursed. PCSK9-inhibitors are available in ∼2/3 countries. Lipoprotein-apheresis is offered in ∼60% countries, although access is limited.

CONCLUSIONS

FH is a recognised public health concern. Management varies widely across countries, with overall suboptimal identification and under-treatment. Efforts and initiatives to improve FH knowledge and management are underway, including development of national registries, but support, particularly from health authorities, and better funding are greatly needed.

Cholesterol-Lowering Agents

Loss-of-function variants in PCSK9 (proprotein convertase subtilisin-kexin type 9) are associated with lower lifetime risk of atherosclerotic cardiovascular disease) events. Confirmation of these genetic observations in large, prospective clinical trials in participants with atherosclerotic cardiovascular disease has provided guidance on risk stratification and enhanced our knowledge on hitherto unresolved and contentious issues concerning the efficacy and safety of markedly lowering LDL-C (low-density lipoprotein cholesterol). PCSK9 has a broad repertoire of molecular effects. Furthermore, clinical trials with PCSK9 inhibitors demonstrate that reductions in atherosclerotic cardiovascular disease events are more effective in patients with recent myocardial infarction, multiple myocardial infarctions, multivessel coronary artery disease, and lower extremity arterial disease. The potent LDL-C lowering efficacy of PCSK9 inhibitors provides the opportunity for more aggressive LDL-lowering strategies in high-risk patients with atherosclerotic cardiovascular disease and supports the notion that there is no lower limit for LDL-C. Aggressive LDL-C lowering with fully human PCSK9 monoclonal antibodies has been associated by a safety profile superior to that of other classes of LDL-lowering agents. These clinical trials provide evidence that LDL lowering with PCSK9 inhibitors is an effective therapy for lowering cardiovascular events in high-risk patients with LDL-C levels ≥70 mg/dL on maximally tolerated oral therapies, including statins and ezetimibe.

The sequencing and interpretation of the genome obtained from a Serbian individual

Recent genetic studies and whole-genome sequencing projects have greatly improved our understanding of human variation and clinically actionable genetic information. Smaller ethnic populations, however, remain underrepresented in both individual and large-scale sequencing efforts and hence present an opportunity to discover new variants of biomedical and demographic significance. This report describes the sequencing and analysis of a genome obtained from an individual of Serbian origin, introducing tens of thousands of previously unknown variants to the currently available pool. Ancestry analysis places this individual in close proximity to Central and Eastern European populations; i.e., closest to Croatian, Bulgarian and Hungarian individuals and, in terms of other Europeans, furthest from Ashkenazi Jewish, Spanish, Sicilian and Baltic individuals. Our analysis confirmed gene flow between Neanderthal and ancestral pan-European populations, with similar contributions to the Serbian genome as those observed in other European groups. Finally, to assess the burden of potentially disease-causing/clinically relevant variation in the sequenced genome, we utilized manually curated genotype-phenotype association databases and variant-effect predictors. We identified several variants that have previously been associated with severe early-onset disease that is not evident in the proband, as well as putatively impactful variants that could yet prove to be clinically relevant to the proband over the next decades. The presence of numerous private and low-frequency variants, along with the observed and predicted disease-causing mutations in this genome, exemplify some of the global challenges of genome interpretation, especially in the context of under-studied ethnic groups.