Genetic analysis of familial hypercholesterolemia in Asian Indians: A single-center study

Familial hypercholesterolemia

Familial hypercholesterolemia is a common genetic disorder of autosomal inheritance associated with elevated LDL-cholesterol. It is estimated to affect 1:250 individuals in general population roughly estimated to be 5 million in India. The prevalence of FH is higher in young CAD patients (<55 years in men; <60 years in women). FH is underdiagnosed and undertreated. Screening during childhood and Cascade screening of family members of known FH patients is of utmost importance in order to prevent the burden of CAD. Early identification of FH patients and early initiation of the lifelong lipid lowering therapy is the most effective strategy for managing FH. FH management includes pharmaceutical agents (statins and non statin drugs) and lifestyle modification. Inspite of maximum dose of statin with or without Ezetimibe, if target levels of LDL-C are not achieved, Bempedoic acid, proprotein convertase subtilisin/kexin type 9 (PCSK9) Inhibitors/Inclisiran can be added.

Genetic Spectrum of Familial Hypercholesterolaemia in the Malaysian Community: Identification of Pathogenic Gene Variants Using Targeted Next-Generation Sequencing

Familial hypercholesterolaemia (FH) is caused by mutations in lipid metabolism genes, predominantly in low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), proprotein convertase subtilisin/kexin-type 9 (PCSK9) and LDL receptor adaptor protein 1 (LDLRAP1). The prevalence of genetically confirmed FH and the detection rate of pathogenic variants (PV) amongst clinically diagnosed patients is not well established. Targeted next-generation sequencing of LDLR, APOB, PCSK9 and LDLRAP1 was performed on 372 clinically diagnosed Malaysian FH subjects. Out of 361 variants identified, 40 of them were PV (18 = LDLR, 15 = APOB, 5 = PCSK9 and 2 = LDLRAP1). The majority of the PV were LDLR and APOB, where the frequency of both PV were almost similar. About 39% of clinically diagnosed FH have PV in PCSK9 alone and two novel variants of PCSK9 were identified in this study, which have not been described in Malaysia and globally. The prevalence of genetically confirmed potential FH in the community was 1:427, with a detection rate of PV at 0.2% (12/5130). About one-fourth of clinically diagnosed FH in the Malaysian community can be genetically confirmed. The detection rate of genetic confirmation is similar between potential and possible FH groups, suggesting a need for genetic confirmation in index cases from both groups. Clinical and genetic confirmation of FH index cases in the community may enhance the early detection of affected family members through family cascade screening.

The Prevalence and Genetic Spectrum of Familial Hypercholesterolemia in Qatar Based on Whole Genome Sequencing of 14,000 Subjects

Familial hypercholesterolemia (FH) is an inherited disease characterized by reduced efficiency of low-density lipoprotein-cholesterol (LDL-C) removal from the blood and, consequently, an increased risk of life-threatening early cardiovascular complications. In Qatar, the prevalence of FH has not been determined and the disease, as in many countries, is largely underdiagnosed. In this study, we combined whole-genome sequencing data from the Qatar Genome Program with deep phenotype data from Qatar Biobank for 14,056 subjects to determine the genetic spectrum and estimate the prevalence of FH in Qatar. We used the Dutch Lipid Clinic Network (DLCN) as a diagnostic tool and scrutinized 11 FH-related genes for known pathogenic and possibly pathogenic mutations. Results revealed an estimated prevalence of 0.8% (1:125) for definite/probable cases of FH in the Qatari population. We detected 16 known pathogenic/likely pathogenic mutations in LDLR and one in PCSK9; all in a heterozygous state with high penetrance. The most common mutation was rs1064793799 (c.313+3A >C) followed by rs771019366 (p.Asp90Gly); both in LDLR. In addition, we identified 18 highly penetrant possibly pathogenic variants, of which 5 were Qatari-specific, in LDLR, APOB, PCSK9 and APOE, which are predicted to be among the top 1% most deleterious mutations in the human genome but further validations are required to confirm their pathogenicity. We did not detect any homozygous FH or autosomal recessive mutations in our study cohort. This pioneering study provides a reliable estimate of FH prevalence in Qatar based on a significantly large population-based cohort, whilst uncovering the spectrum of genetic variants associated with FH.

Healthcare worker-based opportunistic screening for familial hypercholesterolemia in a low-resource setting

Background & objective

Heterozygous familial hypercholesterolemia (FHeH) is important risk factor for premature coronary artery disease (CAD). Strategies for its diagnosis and prevalence have not been well studied in India. We performed healthcare worker-based opportunistic screening to assess feasibility for determining its prevalence.

Methods

A healthcare worker was trained in use of Dutch Lipid Clinic Network (DLCN) criteria for diagnosis of FHeH. Successive eligible individuals (n = 3000 of 3450 screened) presenting to biochemistry laboratories of two hospitals for blood lipid measurements were evaluated for FHeH. Cascade screening or genetic studies were not performed. Descriptive statistics are reported.

Results

We included 2549 participants (men 1870, women 679) not on statin therapy. Health worker screened 25–30 individuals/day in 6–10 minutes each. The mean age was 46.2±11y. Variables of DLCN criteria were more in women vs men: family history 51.1 vs 35.6%, past CAD 48.2 vs 20.1%, arcus cornealis 1.1 vs 0.3%, tendon xanthoma 0.3 vs 0.1%, and LDL cholesterol 190–249 mg/dl in 8.5 vs 2.4%, 250–329 mg/dl in 0.7 vs 0% and ≥330 mg/dl in 0.3 vs 0% (p<0.01). Definite FHeH (DLCN score >8) was in 15 (0.59%, frequency 1:170) and probable FHeH (score 6–8) in 87 (3.4%, frequency 1:29). The prevalence was significantly greater in women, age <50y and in those with hypertension, diabetes and known CAD.

Conclusions

Healthcare worker-led opportunistic screening for diagnosis of FHeH using DLCN criteria is feasible in low-resource settings. The results show significant prevalence of clinically detected definite and probable FHeH in the population studied.

Targeted Exome Sequencing in South Indian patients with Familial Hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is an autosomal dominant genetic disorder with elevated LDL-C levels which can ultimately lead to premature Coronary Artery Disease (CAD).

OBJECTIVES

In presence of limited genetic data on FH in India, the present study was aimed to determine the mutation spectrum in Indian FH patients using a targeted exome sequencing.

METHODS

54 FH cases (31 index cases + 23 extended family members) were categorized according to Dutch Lipid Clinic Network Criteria (DLCNC). Targeted exome sequencing was performed using 23 gene panel associated with lipid metabolism.

RESULTS

All subjects showed the presence of family history of CAD, 38(70%) patients had corneal arcus whereas only 06(11%) subjects had xanthomas. As per the DLCNC, definite, probable, possible and unlikely FH were 48%, 30%, 11% and 11% respectively. Mutations were observed in 12 of the 23 gene panel with CETP, APOA5, EPHX2 and SREBP2 genes were identified for the first time in Indian FH patients. All 19 mutations including a novel frame-shift mutation in LDLR gene were reported for the first time in Indian FH patients. These mutations were identified in 28(52%) subjects and interestingly ∼73% of the clinically identified FH patients didn't harbour mutations in FH classical genes (LDLR, ApoB, PCSK9).

CONCLUSION

This is the first study in the South Indian FH patients to perform targeted exome sequencing. Absence of mutations in the FH classical genes strongly indicates the polygenic nature of FH, further underscoring the importance of targeted exome sequencing for identifying mutations in genetically diverse Indian population.

Shortcomings on genetic testing of Familial hypercholesterolemia (FH) in India: Can we collaborate to establish Indian FH registry?

Familial hypercholesterolemia (FH) is a common autosomal dominant disorder that affects ∼1 in 250–500 individuals globally. The only prevalence study in India shows FH in 15% of patients with premature CAD in North Indians. There are only 6 genetic studies in India of the total mutations, 32% are LDLR mutations, 4% are ApoB, 2% are PCSK9 mutations and the mutational spectrum for 37% is unknown. This calls for widespread genetic screening which could help identify definite FH patients.

European Atherosclerosis Society-Familial Hypercholesterolemia Studies Collaboration (EAS- FHSC) has taken an initiative to develop a worldwide registry of FH. India is also a part of the collaboration and 3 groups from Mumbai, Delhi and Chennai are actively contributing to this registry. We believe this review might help to understand the Indian scenario of FH and investigators across India can contribute in managing FH in India and further help in the detection, diagnosis and treatment.

Evolocumab in patients with homozygous familial hypercholesterolemia in India

BACKGROUND

Evolocumab is a fully human monoclonal antibody inhibitor of proprotein convertase subtilisin/kexin type 9 approved in India for treatment of homozygous familial hypercholesterolemia (HoFH) in patients aged ≥12 years.

OBJECTIVE

RAMAN (NCT03403374) was a single-country, open-label, phase 4 study evaluating the safety and tolerability of evolocumab in patients with HoFH in India.

METHODS

Patients ≥12 to ≤80 years of age on stable lipid-lowering therapy with fasting low-density lipoprotein cholesterol (LDL-C) >3.4 mmol/L (>130 mg/dL) received evolocumab 420 mg subcutaneously monthly (every 2 weeks if on apheresis). The primary endpoint was patient incidence of treatment-emergent adverse events. Secondary endpoints included percent changes at week 12 in LDL-C and other lipids.

RESULTS

Of 30 enrolled patients, 13 were <18 years of age. Mean±SD baseline levels of LDL-C, apolipoprotein B, and lipoprotein(a) were 12.3 ± 3.5 mmol/L (473.5 ± 135.2 mg/dL), 2.8 ± 0.7 g/L (275.3 ± 69.1 mg/dL), and 201.3 ± 177.6 nmol/L, respectively. Ten patients (33%) reported treatment-emergent adverse events, with 2 (7%) serious adverse events and none leading to discontinuation; no deaths occurred during evolocumab treatment. At week 12, mean (SE) percent changes from baseline in LDL-C, apolipoprotein B, and lipoprotein(a) were -6.4% (4.2), -6.0% (3.7), and -0.2% (4.9), respectively. Reductions in LDL-C among individual patients were variable and greatest in patients ≥18 years of age and with baseline LDL-C <13 mmol/L (<500 mg/dL).

CONCLUSIONS

Evolocumab was safe and well tolerated in patients with HoFH in India with smaller reductions in LDL-C and other lipids than those observed in previous studies with HoFH and different populations.

Screening of PCSK9 and LDLR genetic variants in Familial Hypercholesterolemia (FH) patients in India

Familial Hypercholesterolemia (FH) is an autosomal, dominant, inherited disorder characterized by severely elevated LDL-cholesterol (LDL-C) levels with high risk for Coronary Artery Disease (CAD). There are limited genetic studies especially on genes other than Low Density Lipoprotein receptor (LDLR) conducted in Indian population. Thus, our aim was to screen the entire Proprotein Convertase Subtilisin/Kexin type 9 gene (PCSK9) gene & hotspot exons 3, 4 and 9 of LDLR gene in FH cases and controls. 50 FH cases were categorized into definite, probable and possible cases according to Dutch Lipid Network Criteria (DLNC) who were gender matched with 50 healthy controls. All 12 exons of PCSK9, and hotspot exons 3, 4 & 9 of LDLR gene were screened through High Resolution Melt (HRM) curve analysis. Enzyme linked immunosorbent assay was performed to measure circulating PCSK9 levels. Total cholesterol and LDL-C were significantly high in all three groups of cases. Total 8 nonpathogenic variants in exon 1, 5, 7 and 9 of the PCSK9 gene were detected. In LDLR gene, 3 known pathogenic and 1 benign variant were found in exon 3 & 4. In FH cases, PCSK9 levels were significantly high compared to controls (P = 0.0001), and were directly correlated to LDL-C (P = 0.0001) and Total Cholesterol (P = 0.0001). Our study is first to screen the entire PCSK9 gene in western part of India. Since no pathogenic variants were identified, it is possible that PCSK9 variants are clinically less relevant. However, 3 known pathogenic variants were found in the LDLR gene. These findings support our understanding of the genetic spectrum of FH in India.

Genetic Diagnosis of Familial Hypercholesterolemia in Asia

Familial hypercholesterolemia (FH) is a common genetic disease with an incidence of about 1 in 200-500 individuals. Genetic mutations markedly elevate low-density lipoprotein cholesterol and atherosclerotic cardiovascular disease (ASCVD) in FH patients. With advances in clinical diagnosis and genetic testing, more genetic mutations have been detected, including those in low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), proprotein convertase subtilisin/kexin type 9 (PCSK9), and so on. Globally, most FH patients remain undiagnosed, untreated, or inappropriately treated. Recently, there was a Global Call to Action by the Global Familial Hypercholesterolemia Community to reduce the health burden of FH. Asia, despite being the most populous continent with half of the global population, has low FH detection rates compared to Western countries. Therefore, we aimed to review the current status of FH genetic diagnosis in Asia to understand the gaps in FH diagnosis and management in this region.