Genetic Dyslipidemia and Cardiovascular Diseases

Home , Dyslipidemia, Hypobetalipoproteinemia, Tangier disease

Sultan Qaboos University Genetic Dyslipidemia and Cardiovascular Diseases

Fahad AL Zadjali, PhD

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2/14/18 DISCLOSURE OF CONFLICT

No financial relationships with commercial interests

2/14/18 Lipoprotein metabolism

Genetic diseases: - LDL-cholesterol - HDL-cholesterol - Triglycerides - Combines WHO / Fredrickson classification of primary hyperlipidaemias

Familial hypercholestrolemia Genetics defects in ApoB: synthesis and truncated apoB Familial hypobetalipoproteinemia (FHBL) VLDL

TG VLDL B MTP & CE lipid B B TG CE

ApoB synthesis

B TG CE

LDL Familial hypobetalipoproteinemia

LDL-C very low in homozygotes and fat malabsoprion

retinitis pigmentosa Acanthocytosis

Heterozygotes have decreased levels of LDL-C and apoB usually asymptomatic and have a decreased risk of CVD Abetalipoproteinemia (ABL): deficiency of MTP

- Recessive disorder

- Deficiency of all apoB containing lipoproteins (chylomicrons, VLDL and LDL

Fat malabsorption

Acanthocytosis

Retinitis pigmentosa Familial Combined Hypolipidemia

- Mutation in Angiopoietin-like protein 3 (ANGPTL3) - increased activity of lipoprotein lipase - Increase clearance of VLDL LDL and HDL - Low TG and low T.Cholesteorl - No evidence of atherosclerosis Defects in HDL cholesterol levels

Complete deficiency of HDL: APOAI LCAT ABCA1

Hyperalphalipoproteinemia HL CETP Lecithin:Cholesterol Acyl Transferase Deficiency (LCAT) - Convert cholesterol into cholesterol ester in HDL

- deficiency results in accumulation of free cholesterol: corneal opacities Anemia Renal failure Atherosclerosis ABCA1 deficiency (Tangier disease) APOA1 deficiency (Familial HypoAlpha Lipoproteinemia) ATP-binding cassette transporter ABCA1 deficiency (Tangier Disease)

Mediates efflux of cholesterol to newly formed HDL.

Chol. esters accumulation in macrophages:

Orange tonsils Corneal deposits Hepatomegaly/Splenomegaly Peripheral neuropathy Premature CVD APOA1 deficiency (Familial Hypo-Alph Lipoproteinemia)

Very low HDL-C levels (<10mg/dl)

§ Premature CVD § Positive Family History § Corneal opacities Hyper-Alpha-Lipoprotenemia HDL-C > 90th percentile CETP mutation, SR-B1 APOA1 overexpression Copenhagen City Heart Study

Johannsen et al JACC 2012; 60:2041 Isolated high triglyceride levels Familial Hypertriglyceridemia

Eruptive xanthomas Lipemia retinalis

Palmar crease xanthomas High TC and TG Familial Combined hyperlipidemia increase in TC/TG in at least two members of the same family intra-individual and intrafamilial variability of the lipid phenotype increased risk of premature coronary heart disease (CHD)

Increased production of ApoB and VLDL (high LDL, TG and low HDL)

Genetic loci: apoAI-CIII-AIV USF1 TXNIPgene High TC and TG Familial Dysbetalipoproteinemia Type III

Autosomal Recessive trait

- Apo E mutation (E2/E2) - Rapid progressive atherosclerosis (PAD + CAD) WHO / Fredrickson classification of primary hyperlipidaemias

Familial hypercholestrolemia Type IIA Familial Hypercholesterolemia

LDLRAP1

Michael M Page, Aust Prescr 2016 Defects in LDLR • Autosomal dominant hypercholesterolemia (ADH1) è classical FH

• Attributes to 60-90% of FH cases.

• Loss of function mutations >1700 variants

LDLR Home University College London www.ucl.ac.uk/ldlr Population Specific Mutations LDLR mutations in Saudi Arabia Alallaf F. et. al. Open Cardiovasc Med J. 2017 Oman LDLR mutations:

Novel

cDNA Protein c.G1145T p.G382V

c.1214_1216del p.405_406del

c.1319_1332del p.R440fs c.711delC p.R237fs c.C1502T p.A501V c.T1054C p.C352R c.271delG p.G91fs c.504_510del p.D168fs c.G1171A p.A391T c.G1027A p.G343S c.G1285A p.V429M c.G397A p.D133N Apo B 100 gene defects • Autosomal dominant hypercholesterolemia 2 (ADH 2) or Familial defective apoB100 (FDB)

• Attributes to about 5% of FH cases

• Loss of function mutations

Amanda J 2004, clinical Chemistry Amanda J 2004, clinical Chemistry

29 exons

2/3 of mutations are in exon 26 LDLR-binding domain Proprotein convertase subtilisin/kexin type 9 (PCSK9)

• Autosomal dominant hypercholesterolemia 3 (ADH 3)

• Gain of function mutations ( around 50)

• attributes to 1-3% of FH cases.

• Promotes degradation of LDLR Mapping of common natural mutation of PCSK9 to the surface of the molecule.

Eric N. Hampton et al. PNAS 2007;104:14604-14609

Cohen JC. N Engl J Med. 2006;354:1264-72 Typical Features of FH

Heterozygous FH Homozygous FH

• Cholesterol 7.0-14 mmol/L • Cholesterol 10-28 mmol/L

• One major genetic defect in • Two major genetic defects in LDL LDL metabolism metabolism

• Arcus cornealis and Achilles • Tendon and cutaneous tendon xanthomas often xanthomas often before age 10 present years

• CHD onset 30-60 years • CHD onset in childhood

• Most respond to drugs, but • Poorly responsive to drugs; individual response variable apheresis often indicated Autosomal Recessive Hypercholesterolemia (ARH) LDLRAP1

• Very rare

• Only patients with homozygous or compound heterozygous LDLRAP1 mutations are affected Genetic testing for Familial dyslipidemia

Next generation sequencing

EDTA-blood tube Saliva sample Spectrum of mutations in SQUH

20.5

LDLR

39.3 ApoB 2.6 PCSK9

LDLRAP1

no mutation

37.6 Double heterozygous mutation è Homozygous FH

normal HeFH HeFH HoFH

X X X X X

2 1 normal 1 normal 2 defective normal 1 defective 1 defective LDLR LDLR LDLR LDLR Large deletion / duplication of LDLR

Thoracic Key ® Multiplex Ligation-dependent Probe amplification

Run on samples with negative mutations from NGS and no double hit mutations 20% to 40% of individuals with clinical HeFH are mutation- negative in the 4 genes of FH. Polygenic Hypercholesterolemia

• Individuals with elevated LDL-C similar to HeFH

• No Mutation detected in the 4 known genes, No deletion/duplication of LDLR.

• Identification is important as it will comprise the efficiency of cascade screening Meta-analysis of plasma lipid concentrations in >100,000 individuals of European descent

12 SNPs è genotype and quantify LDL-C polygenic score

Teslovich TM et. al. Nature 2010 Gene SNP Minor Allele Common GLGC Allele weight for score calculation CELSR2 rs629301 G T 0.15 ABCG8 rs4299376 G T 0.071 SLC22A1 rs1564348 C T 0.014 HFE rs1800562 A G 0.057 MYLIP rs3757354 T C 0.037 ST3GAL4 rs11220462 A G 0.050 NYNRIN rs8017377 A G 0·029 APOE rs429358 C T -- APOE rs7412 T C -- PCSK9 rs2479409 G A 0.052 APOB rs1367117 A G 0·10 LDLR rs6511720 T G 0.18

LDL-C-raising SNPs reported by GWAS Futema M, Clin Chem 2015 Diagnostic workflow for cascade testing in patients with familial hypercholesterolemia

Talmud PJ, The lancet 2013 Cardiologists Neurologists Recognize and Identify Index case Intenists Opthalmologists Raise Dermatologists awareness Pediatricians GPs Clinical chemists

Cascade genetic screening process Genetic field workers & Clinical pathologists Genetic and lipid profile testing Laboratory workers & Send referral letter with report

Cardiologists Neurologists Intenists Opthalmologists Dermatologists Start lipid lowering therapy Pediatricians & GPs Prevent CVD / death Clinical chemists COST-EFFECTIVNESS OF GENETIC CASCADE SCRENEING

e.g Spanish National Program for FH (NPFH)

9000 FH cases with 10 years follow-up data: 1- prevented 847 coronary events & 203 deaths per year

2- gain of 29,608 Euros per quality-adjusted life years 19,691,492 EUROS

Lazaro, P et. al. J clinic. lipid. 2017 Log-Linear Effect of Lower LDL-C on CHD

Cumulative Effect of Lifelong LDL-C

Ference, BA et al. J Am Coll Cardiol 2015;doi:10.1016/j.jacc.2015.02.020). Cannon CP, et al. AHA, November, 17 2014. Conclusion • FH is caused by mutation of 4 genes LDLR, apoB100, PCSK9, LDLRAP1

• Identified mutations è apply cascade screening for 1st degree relatives

• Genetic cascade screening and cost-effective measure.