Transcript B - Australian Atherosclerosis Society

It’s all relative: Genetic dyslipidaemia
CVD risk factors, and especially lipid metabolism,
exemplify gene / environment interactions
• Mainly genetic
• Co-dominant mutations: Either genetic allele affected
• Recessive mutations: Both genetic alleles affected
• Polymorphisms and SNPs: Alleles consistent with
“normal” and markers in proximity to significant genetic effects.
Genome-wide association studies (GWAS).
• Mainly environmental or secondary to
other disorders.
A missing piece of the genetic puzzle
Clinical
Effect
Pathogenic mutations
Autosomal Autosomal
recessive
dominant
Uncommon genes
with large effect
Polymorphisms
Common genes with small effect
Gene Prevalence
Genetic hyper and hypo cholesterolaemia
• Dominant Monogenic Hypercholesterolaemia
•
•
•
•
Familial hypercholesterolemia (FH)
Familial defective apo-100 (FDB-100)
PCSK9 gain-of-function (FH-3)
Hyperalphalipoproteinaemia (CETP deficiency, non-atherogenic?)
• Recessive Monogenic Hypercholesterolaemia
• Autosomal recessive hypercholesterolemia (ARH)
• Lysosomal acid lipase deficiency: Wolman’s disease and
Cholesterol ester storage disease
• Dominant Monogenic LDL deficiency
• PCSK9 loss-of-function
• Recessive Monogenic LDL deficiency
• Abeta and hypobeta – lipoproteinaemia
• Chyomicron retention disease
Familial Hypercholesterolaemia:
What goes wrong?
NORMAL
FH
Metabolic Defect in Familial
Hypercholesterolemia
B -100
INTESTINE
VLDL
Chylomicrons
B -48
CIII
B
LPL
R
E
LDL-R
CII E
CII
B
LIVER
LRP
AI
E
HDL
AII
CE
AI
LCAT
FC
SRB1
Other
Tissues
IDL
CIII
FH
SRB1
E
AI
LPL
B
HL
LDL
.
O
B
Macrophage
ABCA1
OxLDL
SR-A
DAVIGNON 2006
Metabolic Defect in
Familial Defective ApoB-100
Defective apoB B
INTESTINE
 ApoB
Chylomicrons
B -48
B
LPL
R
VLDL
CIII
E
B
LIVER
LRP
AI
FDB
SRB1
E
AI
HDL
AII
CE
B
LDL
AI
LCAT
FC
SRB1
LPL
LDL-R
CII E
CII
B -100
Other
Tissues
E
IDL
CIII
HL
.
O
B
Macrophage
ABCA1
OxLDL
SR-A
DAVIGNON 2006
PCSK9 regulates the surface expression of
LDLRs by targeting for lysosomal degradation
1. Qian YW, et al. J Lipid Res. 2007;48:1488-1498.
2. Horton JD, et al. J Lipid Res. 2009;50:S172-S177.
3. Zhang DW, et al. J Biol Chem. 2007;282:18602-18612.
Gain-of-Function Mutations in PCSK9
Cause Familial Hypercholesterolaemia (FH)
PCSK9 Variant
D374Y
•
Population
Clinical Characteristics
Premature CHD
British, Norwegian
families,
1 Utah family
Tendon xanthomas
Severe hypercholesterolemia
S127R
French, South African,
Norwegian families
Tendon xanthomas; CHD, early
MI, stroke
R215H
Norwegian family
Brother died at 31 from MI; strong
family history of CVD
Associated with:
•
•
•
High serum LDL-C2
Premature CHD and MI2
In vitro testing in many identified mutations show decreased levels of LDLRs3
1. Abifadel M, et al. Hum Gen. 2009;30:520-529.
2. Horton JD, et al. J Lipid Res. 2009;50:S172-S177.
3. Cameron J, et al. Hum Mol Genet. 2006;15:1551-1558.
*For a full list of ADH mutations, please see refer to Abifadel reference.
What is “FH”? What does it cause?
• FH is
•
•
•
Metabolic
•
•
•
•
•
Co-dominant mutation of genes affecting
formation or function of the LDL-receptor
This causes metabolic and clinical
consequences including precocious
cardiovascular disease (CVD)
Increased LDL,
Reduced clearance of remnants including LDL’s
precursor, IDL.
Increased Lp(a)?
Reduced HDL?
Clinical
•
•
•
•
•
•
•
•
Dominant: 50% of each generation. Risk 50:50
Premature CHD, CVD and PVD
Aortic stenosis
Tendon xanthomas (11%) specific?
Corneal arcus (27%) non-specific > 40y?
Xanthelasmas (12%) nonspecific
No signs highly sensitive
FH IS NOT JUST HIGH CHOLESTEROL IN A
PATIENT AND THEIR RELATIVE(S)
FH: Why is it important?
Cumulative Probability of Clinical CAD
1.0
Non-FH Women
0.9
0.8
0.7
Non-FH Men
FH Women
FH Men
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Age
MED PED Registry 2001.
Why FH matters: Prevalence and Impact
• Prevalence:
• 0.2 – 0.5% (1 : 200-500)
Atherosclerosis 173:55-68
• > 8 x 106 affected world-wide.
Seminars in Vasc Med 4:87-92
• > 40,000 Australians
• Equal numbers of unaffected
relatives
• Up to 1:60 in local groups with
“founder effect”.
• Detection rates 0 – 44%
• World’s best 20-40%
• World average (including
Australia) < 5%
• Impact:
• 5 – 10% of CHD events under
age 60. J Lipid Res 34:269-77
• CVD death in >80% of FH
cases.
• Absolute CVD risk differs from
general population models.
• High risk profile from birth,
• Interaction differs (smoking,
gender) Circulation 97:1837-47
• Risk algorithms underestimate
risk
Eur Heart J 19:A2-11
• Missed and misdiagnosed
Molecular Medicine
meets Public Health
Diagnostic
criteria
Detecting
index cases
Optimal
components
Clinical
services
Laboratory
protocol
Clinical
protocol
Process
Case detection:
Dutch Lipid
Clinic Score?
Adults
Diagnosis
assessment
Children,
Adolescents
Model of
Care for
FH
Genetic
testing
Management
Adults
Cascade
Screening
Process
Children,
Adolescents
LDLApheresis
Severe triglyceride elevation due to recessive
impairment of lipoprotein lipase




Chylomicrons persist after fasting, massive levels of TG.
Homozygous deficiency of Lipoprotein Lipase (LPL)
Homozygous deficiency of the cofactor for L PL, Apo CII
Impaired transport of LPL to site of action (endothelium) due to homozygous
defect in ANGPTL or GPIHBP
 Combined overproduction and undercatabolism of triglyceride-rich lipoproteins
sufficient to saturate LPL, eg in Apo AV mutations.
Metabolic Defects affecting Lipoprotein Lipase
Dietary
fat
INTESTINE
B -100
Chylomicrons
B -48
VLDL
CII
B -48
CR
B
LIVER
E
HDL
AII
IDL
CIII
SRB1
E
CE
AI
LCAT
FC
SRB1
E
LRP
FFA + MG
AI
CIII
LDL-R
E
CII LPL
AI
LPL
Other
Tissues
B
HL
LDL
.
O
ApoB-48 R
B
VLDLR
ABCA1 Macrophage
OxLDL
SR-A
DAVIGNON 2006
Metabolic defects saturating in LPL, eg Apo AV mutations
Sugar
fat
calories
INTESTINE
Chylomicrons
CII
LPL
CII
CR
E
AV
AI
B -48
VLDL
CIII
E
B
E
LRP
SRB1
CETP
AI
B
sdLDL
TG CE
FC LCATVLDLR
Other
Tissues
IDL
CIII
HL
E
AII CE
LPL
aGP + FFATG
LDLR
HDL
SRB1
Normal
B -100 or reduced
VLDL
TG rich catabolism
AV
Overproduction
HSL of VLDL
B -48
AI
ADIPOSE
TISSUE
ABCA1
Macrophage
.
O
SR-A
B
CD-36
OxLDL
LOX-1
SR-PSOX
DAVIGNON 2006
Algorithm for Diagnosis of Apo B Dyslipoproteinemias
HyperApo B
> 1.2 g/L
NormoApo B
< 1.2 g/L
NormoTG
< 1.5 mmol/L
HyperTG
> 1.5 mmol/L
TG:Apo B >
0.12
NomoTG
> 1.5 mmol/L
Hyper TG
> 1.5 mmol/L
LDL
VLDL + LDL
TG:Apo B <
0.12
Apo B > 0.75
g/L
Apo B < 0.75
g/L
TC:Apo B >
6.2
TC:Apo B < 6.2
Chylo + VLDL
Chylo
Chylo + VLDL
Remnants
VLDL
■ Complete
(FHC)
or partial LPL
deficiency
associated
with
a secondary
factor
■ Complete LPL
deficiency
(FHC)
■ Primary apoCII
deficiency
■ Familial
dysbetalipoproteinemia
(type III)
■ Hepatic lipase
deficiency
■ (Primary cause
associated with
a secondary
factor)
Lipoproteins
Normal
Primary
Causes
■ Normal
■ Hypoalphalipoproteinemia
■ Familial
hyperTG
■ Partial LPL
deficiency
■ FH
■ Polygenic
■ FDB
■ PCSK9
deficiency
■ ARH
deficiency
■ CYP7A1
deficiency
■ Hypoalphalipoproteinemia
■ FCH
■ βSitosterolemia
Abbreviations: apo, apolipoprotein; ARH, autosomal recessive hypercholesterolemia; CAPD, continuous ambulatory peritoneal
dialysis; Chylo, chylomicrons; CP7A1, cytochrome P450 7A1; DM2, diabetes mellitus type 2; dysbeta; dysbetalipoproteinemia;
FCH, familial combined hyperlipidemia; FDB, familial defective apoB; FH, familial hypercholesterolemia; FHC, familial
hyperchylomicronemia; HAART, highly active antiretroviral therapy; LPL, lipoprotein lipase; PCOS, polycystic ovary syndrome;
SLE, systemic lupus erythematosus; TC, total cholesterol; TG, triglyceride.
de Graaf J et al. Nat Clin Pract Endocrinol Metab 2008;4:608-
Autosomal recessive disorders have
revealed HDL metabolism
Nascent HDL
A-I
A-I
LCAT
+
FC
CE
FC
ABCA1
Macrophage
Rapid catabolism
Homozygous (?heterozygous) Apo AI deficiency: Atherogenic
Tangier’s Disease: ABC-AI deficiency: Atherogenic?
LCAT Deficiency: Non-atherogenic?
Apo A1 Milano: Anti-atherogenic?
Event Free Survival ( % )
Carriers of the ApoAI Leu178Pro Variant
Are at Increased Risk of Developing CAD
100
family controls
(n=147)
50
apoAI (L178P) carriers
(n=54)
p = 0.008
0
30
40
50
60
Age ( years)
70
ApoAI  50%
80
HDL-C  63%
18.9 x  CAD risk
Hovingh K et al. J Amer Coll Cardiol 44:1429, 2004
DAVIGNON 2006
Normal ApoAI and ApoAIMILANO Dimer
Lipid Binding In
Vivo Catabolism
35
143
187
99
243
AI
1
25
66
121
165
220
209
LCAT Activation “Receptor”
Cholesterol Efflux
Binding
243
AIm/AIm
243
173
1
173
ss
1
Franceschini G Eur J Clin Invest 26; 733, 1996
DAVIGNON 2006
Role of apolipoprotein E
 Apo E: ligand for hepatic
removal of remnants.
AII
 Apo E knockout model is
atherogenic
FC AI
CII
 E2:E2 only critical if
lipids increase for other
reasons.
C
TG
E
AI
TG
 Apo E2 has lower binding
affinity (E4>E3>E2).
LRP
CHYLOMICRON
LPL
B 48
CIII
AI CE
HDL
C
B 48
CR
TG
E
E
E
OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 Other roles for Apo E
(CNS lipid transport and
neural repair).
E
Lipolysis
products
Metabolic Defects in Remnant Dyslipidaemia
Apo E2 homozygosity plus apo B overproduction or Hepatic Lipase deficiency
INTESTINE
FC
LIVER
LDLR
CE
CE
Degradation (catabolic)
E B
FC/PL
Formation (anabolic)
FC
LPL Chylo
to
AI
ChyloRe
PLTP
LCAT
HL
SR-B1
LRP
Kidney
AI E
AI
HDL3 CE
B
LDL
HL
B
Ox
LDL
E
CE
HDL3
AII
TG
E
AI
AI
HL
B VLDL CE CETP
to
Remn
CE
ABCA1
AI
LCAT
CELL
FC/PL
E
TG CE
HDL2 CE
AII
AII
Modified from
Deeb SS et al. J Lipid Res 44:1279, 2003
Unspecified hereditary Dyslipoproteinemia
Common:
K IV
Type 2
-N
K IV
Type 1
Lipoptotein (a)
Apo(a)
N
LDL
particle
CApoB
LDL
Receptor
Binding
Site on apoB
Rare:
-C
K IV
Types 3-10
KV
Protease
DAVIGNON 2006
Familial Phytosterolemia
Micelle
s
ABCG5 Cholesterol
ABCG8 Phytosterols
DAVIGNON 2006
Genetic dyslipidaemias have motivated
treatment discovery
• Clinical abnormalities represent real human problems
• Massive yield on research into genetic dyslipidaemia
• Familial Hypercholesterolaemia: Receptor mediated endocytosis
Statins, PCSK9 antisense and Abs
• Familial Hyperchylomicronaemia: LPL gene therapy
• Apo A1 Milano:
Synthetic HDL
• Deficiency of Apo B or MTP
MTP inhibitors, Apo B antisense
• CETP Deficiency
CETP inhibitors
• Apo E
Valuable animal k/o model
AAS MASTERCLASS
5-6TH OCTOBER 2012
IT’S ALL RELATIVE : MANAGEMENT OF
GENETIC DYSLIPIDAEMIA
CASE 1
HISTORY…
Miss KM, 21year
old Malay student
nurse July
1997
• Cycling accident at her home town
• Sustained minor soft tissue injury
• Noted to have xanthelasma around her
eyes
• Lipid profile results:
•TC : 15.4 mmol/L
•LDL: 13.9 mmol/L
• Referred to Medical Clinic, home town
• Started Pravastatin 20 mg/ON
• Referred to Specialist Llipid
Clinic
• Hypercholesterolaemia
• ‘Yellowish butterfly patterned
lesion’ around her eyes
• On Pravastatin 20mg ON
• TC 13.7, LDL-c 11.6 mmol/L
6th August
1998
HISTORY……
 Noted ‘yellowish butterfly patterned lesion’ surrounding both
eyes since primary school days
 Asymptomatic, well
 No h/o chest pain, palpitation, shortness of breath or poor
effort tolerance
 No history of intermittent claudication or syncopal attacks.
 No h/o polyuria, polydipsia
 No h/o cold intolerance, lethargy or menstrual disturbance
 No past h/o jaundice, liver or renal diseases
 Not HT, DM
 No past surgical history
- HISTORY…
 The youngest out of 11 siblings
 3 siblings died :
 eldest brother : died @ 43 years – AMI (HC)
 elder brother (6th) : died @ 23 years – AMI (HC,
xanthelasma)
 eldest sister (2nd) : died @ 33 years - ?MI, ? SCD
 Parents - consanguinous marriage (first cousins),
not known to have DM/HPT/CAD
- HISTORY…






Student nurse at a Teaching Hospital, KL
Single
Non smoker
No history of alcohol intake
Exercise - once weekly (jogging), 30minutes
Normal diet, low fiber intake
Physical Examination
Anthropometry:
• BMI :
• Waist circumference :
• Waist-to-hip ratio:
22.1
61cm (<80cm)
0.71 (<0.85)
• PR: 72/min, regular, BP : 120/62 mmHg, DRNM
• Peripheral pulses – present, carotid & renal bruit :
absent
• Other systems: Normal
Xanthelasma
Right Left
Eye
Eye
Grade 4 Grade 4
Corneal Arcus
Corneal Arcus grading:
0 – no arcus observable
1- upper or lower segments affected
2- both segments affected
3- both segments and just confluent
4- heavy confluent arcus
(Wider et al, 1983)
Digital xanthomata
Achilles tendon
xanthomata
Test
Result
Reference
range
**FSL
Baseline
(1997)
1st visit to
the SLC
TC
HDL-c
15.4
1.5
13.7
1.6
< 5.7 mmol/L
> 1.3 mmol/L
LDL-c
Triglycerides
13.9
1.0
11.6
1.1
<3.8 mmol/L
< 1.3 mmol/L
On pravastatin 20 mg / ON x 1 year
Summary of KM’s risk factors
Positive risk factors:
Negative risk factors:
 Markedly elevated TC &
LDL levels
 Strong family history of
premature CAD






HDL > 1.3 mmol/L
Non smoker
Not hypertensive
Not DM
Not overweight/ obese
Premenopausal female
Differential Diagnosis
1° Hypercholesterolaemia
Familial
hypercholesterolaemia (FH)
2° Hypercholesterolaemia TRO
Hypothyroidism
Familial Defective ApoB100
Cholestasis
PCSK9 gain-of-function
mutation (FH-3)
Nephrotic syndrome
Polygenic
hypercholesterolaemia
Tests
TFT
fT4
TSH
Results
Reference Ranges
11.78
1.22
9.10 – 23.8 nmol/L
0.32- 5.00 Iu/L
FPG
Glucose
4.4
<6.1 mmol/L
Renal Profile
Sodium
Potassium
Urea
Creatinine
134
4.2
3.2
66
135 – 150 mmol/L
3.5 – 5.0 mmol/L
2.5 – 6.4 mmol/L
44-80 umol/L
Tests
LFT
Albumin
Total Protein
Bilirubin Total
ALT
ALP
Creatine Kinase
Lp(a)
Results
42
84
16
17
89
42
0.58
Reference Ranges
35-50 g/L
67-88 g/L
< 23 umol/L
<44 U/L
32 – 104 U/L
24-135 U/L
<0.3g/L




ECG – normal
Exercise stress test – normal
ECHO – Normal, no evidence of aortic stenosis
Carotid artery IMT – normal, no evidence of atheromatous
plaques
OTHER INVESTIGATIONS….
Question 1
What are the various criteria for the
diagnosis of FH?
•
•
•
•
Dutch Lipid Clinic Network diagnostic scoring
Simon Broome’s criteria
MedPed criteria for FH
NCEP ATPIII criteria
Question 2
According to the Dutch Lipid Clinic Network criteria,
scoring for definite FH is:
• > 8 points
• 6 – 8 points
• 3 – 5 points
Question 3
In determining the Dutch Lipid Clinic diagnostic scoring for
FH, the following are taken into account:
•
•
•
•
•
•
•
•
Baseline LDL-c concentration: Yes/ No
Clinical history of premature CAD: Yes/ No
Clinical history of premature cerebral or PVD: Yes/ No
Tendon xanthoma(ta) in the patient: Yes/ No
Premature corneal arcus in the patient: Yes/ No
Family history of hypercholesterolaemia: Yes/ No
Family history of premature CAD/PVD in 1st degree relatives: Yes/ No
Family history of tendon xanthomata and/or corneal arcus in 1st degree
relatives: Yes/ No
Dutch Lipid Clinic – Diagnostic scoring for FH
Criteria:
Criteria:
• 8 points - DNA Mutation, or LDL-C
> 8.5mmol/L
• 6 points - Tendon xanthomas
• 5 points - LDL-C 6.5 – 8.4mmol/L
• 4 points - premature corneal arcus
< 45 yrs
• 3 points - LDL 5.0 – 6.4mmol/L
• 2 points - 1st degree relative with
xanthomas or premature CA or
childhood LDL > 95th percentile, or
personal premature CAD
• 1 point - 1st deg relative with
premature CAD/ vascular dis or
LDL > 95th percentile, or personal
history of premature cerebral or
PVD, or LDL-c 4.0 – 4.9mmol/L
Family history:
•
1st degree relative with (a) premature CAD or
vascular dis (men<55yrs, women<60yrs) OR (b)
LDL > 95th percentile, in
- 1 point and / or
•
1st degree relative with tendon xanthomata
and/or corneal arcus OR childhood (<18yrs) LDL
> 95th percentile
- 2 points
Clinical history
•
Patient with premature CAD (men<55, women
<60yrs)
- 2 points
•
Patient with premature cerebral or PVD (men<55,
women <60yrs) -1 point
Physical Examination - patient
•
Tendon xanthomas - 6 points
•
premature arcus
- 4 points
Lab Analysis –
•
LDL-c >8.5mmol/>
- 8 points
•
LDL-c 6.5 – 8.4
- 5
•
LDL-c 5.0 - 6.4
-3
•
LDL-c 4.0 – 4.9
-1
DNA analysis
•
Functional DNA Mutation
- 8 points
Definite: > 8 points, Probable: 6 – 8 points, Possible
US MedPed Criteria vs Simon Broome
criteria for the dx of FH
• Total cholesterol cutpoints (mmol/L)
• 1st-degree vs 2nd-degree vs 3rd-degree relatives with FH vs
General population
• Age (years)
•
•
•
•
<20
20–29
30–39
≥40
1st-degree 2nd degree 3rd degree General population
5.7
6.2
7.0
7.5
5.9
6.5
7.2
7.8
6.2
6.7
7.5
8.0
• FH is diagnosed if TC levels exceed the cutpoint
• Key: FH = familial hypercholesterolaemia
7.0
7.5
8.8
9.3
Simon Broome Criteria - Diagnosis of FH
Criteria Description
• (A) TC > 7.5 mmol/L in adults or TC > 6.7 mmol/L in children <16
years, or LDL-c > 4.9 mmol/L in adults or > 4.0 mmol/L in children
• (B) Tendon xanthomas in the patient, or a first-degree or seconddegree relative
• (C ) DNA-based evidence of mutation in the LDLR, or apo- B100
or PCSK9 gene
• (D) Family history of premature CHD (age <50 years in a
second-degree relative or <60 years in a first-degree relative)
• (E) Family history of raised TC >7.5 mmol/L in a first- or seconddegree relative, or >6.7mmol/L in child, brother or sister <16yrs of
age
Diagnosis
• Definite FH diagnosis requires either A + B or A + C
• Possible FH diagnosis requires either A +D or A + E
• Key: FH = familial hypercholesterolaemia
Summary
•
•
•
•
•
Hypercholesterolaemia (LDL-c 13.9mmol/L)
Xanthomata, corneal arcus, xanthelasma
No evidence of personal CAD
Strong family history of premature CAD
Positive family history of HC – 1st and 2nd
degree relative
• Consanguity
• Ruled out secondary causes of HC
CLINICAL DIAGNOSIS
DEFINITE FAMILIAL
HYPERCHOLESTROLEMIA
Question 4:
Should risk estimation tools eg Framingham
Risk Scoring be used for her?
• YES
• NO
CHD Risk Stratification
• CHD estimation tools such as those based on the Framingham
risk scoring SHOULD NOT be used because people with FH are
already at high risk of premature CHD.
• Heterozygous FH has >50% risk of CHD in men by the age of
50years, >30% in women by the age of 60years
NICE Clinical Guideline 2008- Identification and Mx of FH
• 2.5.1 Individuals with FH are at high CHD risk. The 10-year CHD
risk in the FH patient is not adequately predicted by any
conventional risk assessment tools. Therefore, assessment of 10year risk is not recommended.
Management





Statin therapy - continued, titrated
Add-on lipid lowering
Lifestyle modification
Referred to dietician
Referred to :
- Cardiology
- Plastic surgery
 Family tracing, cascade screening and counselling
Medication
TC
(mmol/L)
TG
HDL
LDL
Baseline, statin naive
15.4
1.0
1.5
13.9
Pravastatin 20 mg /ON
13.7
1.1
1.6
11.6
Pravastatin 20 mg/ON
11.9
1.1
1.0
10.4
Simvastatin 30 mg/ON
13.1
1.1
1.4
11.3
Atorvastatin 80 mg/ON
15.3
1.4
1.2
13.5
Atorvastatin 80 mg/ON
11.7
0.7
1.26
10.1
Atorvastatin 80 mg/ON
11.3
0.7
1.1
9.8
Atorvastatin 80 mg/ON
11.9
0.6
1.4
10.2
Atorvastatin 80 mg/ON
11.5
1.1
1.2
9.8
Simvastatin 80mg &
Ezetimibe 10mg/ ON
8.9
1.2
1.1
7.3
Alternative or add-on lipid lowering
therapy
•
•
•
•
•
Ezetimide
Bile acid binding resin
Fibric acid derivatives
Nicotinic acid
LDL-apharesis
LIFESTYLE MODIFICATION
 Lifestyle modification - reduce LDL-c and other coronary RFs
 Modest, variable degree of LDL reduction ̴ 10%
 Diet – low fat <30% calories, saturated fat < 10% of calories,
cholesterol < 200mg/day, fibre 10-25g/day, caloric deficit 300500kcal/day
 Plant sterol esters or plant stanol esters 2g/day
 Physical activity – 30min/day, moderate intensity, at least 5days
per week




Ideal weight BMI < 23 (Asian)
Smoking
Alcohol intake
HT, DM
Father
Mother
HC
Xanthelasma
1
2
HC
Xanthoma
6
3
3
62
4
SD ?MI
6
7
4
0
3
9
3
8
8
9
10
11
Xanthelasma
CAD+
HC
HC
Xanthoma
33
4
HC
3
CAD+
5
2
3
3
3
3
2
2
6
2
3
2
1
HC
Xanthoma
Those found to have HC
following family screening
FAMILY TREE -
Father
Mother
TC : 8.7
LDL : 6.7
TC : 8.1
LDL : 5.7
1
2
3
4
TC : 8.0
LDL : 6.4
33
39
5
7
TC : 16.2
LDL : 14.8
38
TC : 8.1 40
LDL : 5.7
43
6
33
23
TC : 6.5
LDL : 4.6
8
32
TC : 7.0
LDL : 5.2
9
26
10
11
23
TC : 10.1
LDL : 6.7
21
TC : 4.9
LDL : 2.6
TC : 15.3
LDL : 13.9
TC : 7.7
LDL : 4.6
TC : 8.7
LDL : 6.5
Affected with FH
FH with known mutation
TC : 6.1
LDL : 4.4
TC : 8.7
LDL : 6.5
Died
Family Screening ( Lipid Screening) - 1999
Genetic testing was performed on KM
and her family members
Question 5:
What genes have been implicated in FH?
•
•
•
•
•
LDL Receptor
Lipoprotein lipase
Apo B100
Apo CII
PCSK9
Low Density Protein Receptor (LDLR)
Gene
• Cytogenetic Location: 19p13.2
• Size: 44,469 bases
• Mosaic protein of ~840 amino acids (after removal of
signal peptide); Molecular weight 95,376 Dalton
LDLR PROTEIN
 Made up of a number of
functionally distinct
domains that can
function independently of
each other.
 Ex 1 contains a signal
sequence that localizes
the receptor to the ER for
transport to the cell
surface
 Ex 2-6 code the ligand
binding region
 Ex 7-14 code the EGFP
domain
 Ex 15 codes the
oligosaccharide rich
region
DHPLC RESULTS – LDLR Exon 5
Mutation Screening by DHPLC
Heteroduplex peaks of FH patients
with variant in exon 5
Wash peak
g.763T>A
Homoduplex peak of NC sample (wild type sample)
Heteroduplex peaks of FH
patients
with variant in exon 5
g.763T>A
The DHPLC chromatogram profiles of FH patients showed presence of heteroduplex peaks eluted at
5.2 mins and 5.8 mins at denaturing temperature of 62.8 0C. The presence of heteroduplex peaks were
suggestive of disease-causing variants and subjected to DNA sequencing to confirm the variants.
DNA SEQUENCING RESULTS
FH Patient
ID
Affecte
d
LDLR
regions
DNA Sequence
Description of variant and effect
KM, SFM &
Exon 5
Reference
g.763T>A; Cysteine (C) to Serine (S);
WC (3
:GCCGGCAGTGTGACCG
Homozygous and Heterozygous
members of a
Variant
mutation C234S
Malay Family)
:GCCGGCAGAGTGACCG
NYK
Exon 9
Reference :
g.1216C>T; Arginine (R) to Tryptophan
CTTCACCAACCGGCACG
(W), Heterozygous mutation R385W
Variant
:
CTTCACCAACTGGCACG
DNA SEQUENCING RESULTS
Reference sequence
from normal control
DNA sequence of
Homozygous FH patient
Affected
LDLR region
Exon 5
DNA Sequence
Reference: GCCGGCAGTGTGACCG
Variant : GCCGGCAGAGTGACCG
Homozygous:
Substitution T>A at
nucleotide position
763 (g.763T>A)
Description of variant and effect
g.763T>A; Cysteine(C) to Serine
(S) at codon 234. Identified as
homozygous mutation C234S.
DNA SEQUENCING RESULTS
Reference sequence
from normal control
DNA sequence of
Heterozygous FH patient
Affected
LDLR region
Exon 5
DNA Sequence
Reference: GCCGGCAGTGTGACCG
Variant : GCCGGCAGAGTGACCG
Heterozygous:
Substitution T>A
at nucleotide
position 763
(g.763T>A)
Description of variant and effect
g.763T>A; Cysteine(C) to Serine
(S) at codon 234. Identified as
heterozygous mutation C234S.
KM is now married with 2 children
Questions 5:
What is the probablity that her children may
have FH with every pregnancy?
• 50%
• 25%
Questions 6:
When should diagnostic tests be done for her children?
• At birth
• By the age of 10 years or earliest opportunity
thereafter
• AD, one affected parent – 1:2 (50%) chance of heterozygous with
every pregnancy
• In children with one affected parent, the following Dx-tic tests
should be done by the age of 10yrs or at the earliest opportunity
thereafter:
- DNA test if the family mutation is known
- LDL-c if the family mutation is not known. To exclude the Dx of FH,
LDL-c should be repeated after puberty - LDL-c concentration
changes at puberty to almost similar to that of adult concentrations
• Cascade testing – combination of DNA testing and LDL-c to
identify affected relatives
• In children at risk of homozygous FH (2 affected parents or
presence of clinical signs eg cutaneous xanthomata), measure
LDL-c before 5yrs of age or at the earliest opportunity thereafter. If
LDL >11mmol/L, clinical Dx of homozygous FH should be
considered
NICE Clinical Guideline 2008- Identification and Mx of FH
Question 7:
Who can be considered for LDL
apheresis treatment?
Adults and children/young people with
• Homozygous FH
• Heterozygous FH
LDL lowering apheresis
• Treatment of adults and children/ young adults with
homozygous FH
- In children with 2 affected parents
- Presence of clinical signs eg cutaneous lipid deposits
(xanthomata)
- LDL-c should be measured before 5 yrs of age, or earliest
opportunity thereafter
- LDL-c > 13mmol/L (adults), > 11mmol/L (children/ young
adults) – consider clinical diagnosis of homozygous FH
• Exceptional cases of heterozygous FH –progressive
symptomatic CHD despite maximal tolerated lipid-modifying
drug therapy, optimal medical and surgical therapy
• Specialist centre
• Cost implication
Question 8:
What are the future lipid lowering
therapy?
• Antisense oligonucleotides (ASO) to inhibit Apolipoprotein B
production –eg Mipomersen
• PCSK9 targeted therapy –eg PCSK9 inhibitor
• Microsomal TG Transfer Protein Inhibitors –eg lomitapide
• Thyroid Mimetics – eg eprotirome
• Cholesterol Ester Transfer Protein (CETP) Inhibitors anacetrapib, dalcetrapib
(1) ANTISENSE OLIGONUCLEOTIDES
(ASO) – MIPOMERSEN
• Subcutaneous 200mg 1x/wk – phase 3 CT, LDL reduction lasted for
4/52 after last dose. No clinically relevant interactions wrt clearance of
statins and ezetimide - impt as add-on therapy
Yu et al Clin Pharmacokinet 2009;48:39-50
• Homo FH (n=51) - Recent double blind CT, sc mipomersen 200mg/wk
vs placebo x26wks – 25% vs 3% LDL reduction, 27% reduction apoB,
21% reduction TC
Raal FJ et al. Lancet 2010;375:998-1006
• Hetero FH (n=124), CAD+ on max tolerated statins: 45% of these high
risk subjects achieved target LDL of < 100mg/dL (2.6mmol/L)
EAS Congress 2011
2. PCSK9 TARGETED THERAPY
• Animal studies – beneficial up to 80% LDL lowering, human
studies not published yet
Frank-Kamenetsky et al. Proc Natl Acad Sci USA
2008;105:11915-20
Chan JC et al. Proc Natl Acad Sci USA 2009;106:9820-5
• Statins and fibrates induce increase PCSK9 expression, thus
PCSK9 inhibition could induce robust LDL reduction as add-on
therapy in FH
3. MICROSOMAL TG TRANSFER PROTEIN (MTP) INHIBITORS
• MTP inhibition with BMS-201038 in homozygous FH (n=6), dose
1mg/kg/day - 50% LDL reduction but noted to induce hepatic steatosis
Cuchel et al. New Engl J Med 2007;356:148-56
• MTP inhibition in homozygous FH (n=10) , dose 60mg/D – 44% LDL
reduction; less steatosis
Cuchel et al.Circulation 2009;120:S441
• Ezetimibe 10mg vs MTP inhibition by lomitapide (5-10mg/ D x4/52) –
20% vs 20-30% in a dose-dependant manner
• Combined therapy (ezetimide + lomitapide) – similar but larger dose
dependent LDL reduction (35-45%); SE: Mild ALT increase, diarrhoea
Samaha et al. Nat Clin Pract Cardivasc Med 2009;2010:906-16
• Potential attractive candidate for lipid lowering in FH patients if
administered in lower doses
4. THYROID MIMETICS
• Thyroid hormone analogues – reduce LDL but associated with
cardiac and bone related SEs
• More recently differential molecular mechanisms (cpds that act
on TR-beta mainly expressed in the liver, do not affect TR-alpha
expressed in brain and heart) – eg eprotirome, selective TR
beta agonists (under Ix)
• Statin + placebo/ eprotirome for 12/52 – 20-30% additional
reduction of LDL; no SE on heart or bone
Ladenson et al. Use of thyroid hormone analoque eprotirome in
statin-treated dyslipidaemia. New Engl J Med 2012;362:906-16
5. CETP (CHOLESTEROL ESTER TRANSFER
PROTEIN) INHIBITORS
•
•
•
X2 approaches to inhibit CETP
(a) Vaccine - CETi-1 synthetic CETP peptide vaccine, immune response anti
CETP- Abs
Animal studies of this vaccine – increase HDL, reduce aortic atherosclerosis
but human studies poor response of autoAB production
Rittershaus et al. Vaccine induced Abs inhibit CETP activity in vivo and reduce aortic
lesions in a rabbit model of atherosclerosis, ATVB 2000;20:2106-12
Davidson et al. The safety and immunogenicity of a CETP vaccine in healthy adults.
Atherosclerosis 2003;169:113-20
(b) Small molecule CETP inhibitors – eg Torcetrapib, anacetrapib, dalcetrapib antagonize CETP activity by binding to it.
• RADIANCE I – 800 FH pts, torce + atorva: No reduction in atherosclerosis
(IMT) despite reduction in LDL (20%) and increase HDL (52%)
Kasteleine JJ et al. Effect of torcetrapid on carotid atherosclerosis in FH.
NEJM 2007;356: 1620-30
5. CETP (CHOLESTEROL ESTER TRANSFER PROTEIN) INHIBITORS
Cont…….
• ILLUMINATE – torce + atorva, prematurely terminated, unexpected
increase in M&M – exact mechanisms unclear ?torce induced
increase BP
Barter et al. Effects of tercetrapid in patients at high risk of coronary
event, NEJM 2007;357:2109-22
Xie et al. Drug discovery using chemical systems biology:identidfication
of the protein-ligand binding network to explain the side effects of CETP
inhibitors. PLoS Comput Biol 2009;5:e1000387
• 2 other CETP inhibitors have no effect on BP – molecule-specific offtarget effect
• Anacetrapid and dalcetrapib – phase 3 clinical trials , mild HC and
pts with CVD risk, effective lipid modifiers
• Pending CV outcome trials (DAL-outcomes I and II and
HPS3/REVEAL)
• CETP inhibition likely to benefit patients with FH
Summary
• A 21year old Malay female student nurse who presented
with
incidental
xanthelasma
and
severe
hypercholesterolaemia associated with a strong family h/o
premature CAD, xanthomata and grade 4 corneal arcus.
There was consanguity between her parents. She is slim,
non-smoker, euglycaemic, normotensive and has good HDLc levels (>1.3mmol/L). Family tracing was performed.
Molecular analyses confirmed the presence of homozygous
FH with exon 5, position 763 T>A mutation of the LDLR,
coding for the LDL binding domain.
• The updates on the present and future management, and
the molecular pathogenesis of FH have been discussed.
Learning Issues
• FH criteria for diagnosis
• High coronary risk category, should not use risk
assessment tools
• LDL Receptor protein and gene
• Genetic testing – when to test for children?
• Lifestyle modification
• Current treatment, targets
• Plasma apheresis – when is it indicated?
• Future lipid lowering therapy