TG-rich lipoproteins as drivers of atherosclerosis

VIIth ISA Amsterdam 2015Xchange session 16: TG-rich lipoproteins

2015 May 25 1500-1630 h

Robert Hegele MD FRCPC FACPhegele@robarts.caWestern University

London, Canada

TG: driver or passenger?

Overview

HTG:- epidemiology

- genetics- clinical trials

Case report

- 54 year-old male, fire-fighter, BMI 25.9

- dyslipidemia x 10 yrs: rosuvastatin 40 mg

- type 2 diabetes x 5 yrs: metformin, gliclazide

- hypertension x 3 yrs: trandolapril

- pre-Rx TC 11.7; TG 44.0; HDL-C 0.75

- switch to fenofibrate 160 mg daily

- post-Rx TC 5.61; TG 9.93; HDL-C 0.96

Case report

LipidSeq analysis

1. monogenic HTG: LMF1 p.R451W htz.

2. polygenic HTG: 23/28 (>99th percentile)

Dx: partial LMF1 deficiency + polygenic HTG

Plasma TG distributionSource: Canadian Heart Health Surveys (N=19390)

50.6% femalesmean=1.55 mmol/Lmedian=1.27 mmol/Lstandard deviation=1.19 mmol/L

Hypertriglyceridemia (TG > 95th percentile)

1:600

HTG proposed definition

Hegele RA et al. Lancet Diabetes Endocrinol. 2014; 2:655-66.

HTG: associated features

- abdominal obesity

- insulin resistance

- hypertension

- low HDL-C

- NAFLD

- increased small dense LDL

- low grade inflammation

- pro-coagulant state

- endothelial dysfunction

- arterial wall thickening + stiffness

TG level: a marker

TGRL: IDL, VLDL & CM remnants

non-fasting lipids

non-HDL-C

apo B

small dense LDL

HDL-C

monogenic HTG rare variants

TG-rich lipoprotein metabolism

Lewis et al. Endo Rev 2015; 36: 131-47.

Monogenic HTG (chylomicronemia)disorder gene OMIM numbers prevalence

lipoprotein lipase deficiency

LPL 609708; 238600 >150 mutations> 95% of cases

apolipoprotein C-II deficiency

APOC2 608083; 207750 ~15 mutations~20 families

glycosylphosphatidyl-inositol anchored HDL binding protein 1 deficiency

GPIHBP1 612757 ~15 mutations~20 families

apolipoprotein A-V deficiency

APOA5 606368 ~10 mutations~10 families

lipase maturation factor 1deficiency

LMF1 611761; 246650 2 mutations3 families

glycerol-3-phosphate dehydrogenase 1 deficiency

GPD1 138420; 614480 2 mutations2 families

Brahm AJ, Hegele RA. Nat Rev Endocrinol 2015; epub ahead of print

Monogenic low TG

disorder gene OMIM numbers

abetalipoproteinemia MTP 157147; 200100

familialhypobetalipoproteinemia

APOB 107730

familial combined hypolipidemia

ANGPTL3 604774; 605019

apolipoprotein C-III deficiency

APOC3 107720

Brahm AJ, Hegele RA. Nat Rev Endocrinol 2015; epub ahead of print

polygenic HTG rare variants

CREB3L3

GPIHBP1

LMF1

ZHX3

APOC2

APOB

GCKR

LPL

APOA5

Johansen et al. Circulation CVG 2012; 5:66-72

Polygenic HTG - rare variants

Johansen et al. Nat Genet 2010; 42:684-87

CREB3L3

GPIHBP1

LMF1

ZHX3

APOC2

APOB

GCKR

LPL

APOA5

GWAS and non-GWAS loci; OR 2.4 (1.8 – 3.0)Johansen et al. Circulation CVG 2012; 5:66-72

Polygenic HTG - rare variants

Johansen et al. Nat Genet 2010; 42:684-87

polygenic HTG common variants

Polygenic risk scores in HTGSNP location gene TG-raising allele effect on TG

(mmol/L)rs10889353 1:63118196 ANGPTL3 A 0.05rs7557067 2:21208211 APOB A 0.08rs1260326 2:27730940 GCKR T 0.12rs714052 7:72864869 MLXIPL A 0.16rs7819412 8:11045161 XRK6 A 0.04rs328 8:19819724 LPL C 0.19rs12678919 8:19844222 TRIB1 A 0.25rs2954029 8:126490972 FAD Cluster A 0.11rs174547 11:61570783 APOA1.C3.A4/5 C 0.06rs964184 11:116648917 APOA1.C3.A4/5 G 0.30rs3135506 11:116662407 APOA1.C3.A4/5 C 0.15rs662799 11:116663707 APOA1.C3.A4/5 G 0.14rs17216525 19:19662220 NCAN C 0.11rs7679 20:44576502 PLTP C 0.07

Curr Opin Lipidol 2015; 26:103-13

Polygenic risk scores in HTG

Polygenic risk scores in HTG

2o factors

common(polygenic)

rare (monogenic)

HTG: gene x environment

epidemiologic

Sarwar N et al. Circulation 2007; 115: 450-8

TG and CVD risk

ERFC Circulation 2009; 302: 1993-2000

TG and CVD risk

HDL-C, non-HDL-C

Non-fasting TG and CVD risk

Bansal S et al. JAMA 2007; 298: 309-16

Jorgensen et al. NEJM 2014; 371: 32-41

TG and CVD risk

Severe HTG and death

age SMR 95% CI

CHD

- men 20 - 79 3.04 2.04 – 4.37

- women 20 - 79 5.13 1.88 – 11.2

- overall 20 - 79 3.27 2.28 – 4.55

all-cause

- men 20 - 79 1.62 1.23 – 2.11

- women 20 - 79 1.76 0.94 – 3.01

- overall 20 - 79 1.65 1.29 – 2.08

Neil HAW et al. Atherosclerosis 2010; 211: 618-23.

337 patients; 22.3% female; mean TG 12.6 mmol/L

mechanistic

TGRL: mechanistic role

Direct: - plaque components (CE, FA, B-48)

- remnants penetrate, are retained & taken up by mf

Indirect: - impaired vasodilation, endothelial dysfunction

- inflammation; pro-inflammatory cytokines

- monocyte activation

- stimulate monocyte and endothelial tissue factor - promote thrombin formation

- FBG, factors VII and XII

- impair fibrinolysis, PAI-1

- + effects of HDL

‒ VLDL and remnants from human lesions account for >35% of plaque cholesterol1

‒ arterial exposure to remnants enhances deposition of cholesterol2

‒ HTG VLDL and remnants induce mf foam cell formation, which is enhanced following their oxidation3

‒ human SMCs accumulate CE when exposed to native and oxidized VLDL and VLDL remnants4

‒ VLDL and remnants induce mf foam cell formation and the inflammatory response5

HTG directly promotes atherosclerosis

1) Rapp JH et al. ATVB 1994;14:1767-17742) Proctor SD et al. ATVB 2004;24:2162-2167.3) Whitman SC et al. ATVB 1997;17:1707-1715.4) Argmann CA et al. ATVB. 2004;24:1290-12965) Bojic LA et al. ATVB 2012;32:2919-2928.

VLDL-induced Macrophage Foam Cell Formation

TG

Lipid Storage

Droplets

FA

Free Fatty

Acids

LPL

FAT/CD36

Rowe AH et al. Circ Res2003; 93:717-25

Whitman SC et al. ATVB 1999; 19: 1238-49

Nucleus

LDLRCD36

SRAI/II

VLDLVLDL-REM

Oxidized

Oxidation

CE

Lysosome ACAT

FC

ER

LXR

Oxysterols

HDL3

ApoAI

ABCG1

ABCA1 ABCA1

ABCG1

VLDL-Fatty Acid – Induced Macrophage Inflammatory Cytokine Expression

TG

Lipid Storage

Droplets

LPL

Cytokine

Expression

VLDL

FA

Free Fatty AcidsLPL

CPT-1α

FAT/CD36

p65

p50

pSpS AP-1

Nf-κB

RE

AP-1

RE IRE

p65

p50pSpS AP-1

FoxO1

FoxO1

Bojic LA et al. ATVB 2012; 32:2919-2928

Nucleus

Free Fatty Acids

genetic:common variants

Sarwar et al. Lancet 2010; 375:1634-9.

APOA5 -1131T>C SNP, TG and CHD risk

genetic:rare variants

Jorgensen et al. NEJM 2014; 371: 32-41

APOC3 mutations reduce TG & CVD risk

Crosby et al. NEJM 2014; 371: 22-31

APOC3 mutations reduce TG & CVD risk

controls1.56 mmol/L1.31 mmol/L3.77 mmol/L

TG HDL-C LDL-C

carriers0.961.603.18

P-value6 x 10-9

4 x 10-6

0.05

Do R et al. Nature 2015; 518: 102-106

APOA5 mutations raise TG and CVD risk

controlsTG 1.17 mmol/L*

HDL-C 1.47 mmol/L*LDL-C 2.79 mmol/L#

carriersTG 1.89 mmol/L

HDL-C 1.11 mmol/LLDL-C 2.84 mmol/L

* P=0.007# NS

clinical trials

8

HHS: pre-treatment HDL and TG and CVD

High TG > 2.3 mmol/LLow HDL-C < 1.1 mmol/L

Circulation 1995; 92: 1779-85

Miller M et al. JACC 2008;51:724-30.

Despite achieving LDL-C <1.8 mmol/L with a high-dose statin, patients with TG ≥2.3 mmol/L have a 67% higher risk of coronary

events*

Elevated TG levels increase risk of a coronary event, despite LDL-C at goal

*Death, myocardial infarction or recurrent acute coronary syndrome†Calculated from adjusted hazard ratio of TG <200 mg/dL (95% CI) = 0.60 (0.45–0.81)

0

5

10

15

20

25

30-d

ay r

isk o

f death

,M

I or

recurr

ent

ACS (

%)

2.3(n=603)

<2.3(n=2,796)

On-treatment TG (mmol/L)

+67%†

p=0.001

PROVE IT-TIMI 22

13.2%

20.3%

42

Effect of fibrates in HTG subgroups

N Engl J Med 2010; 363:692-695

High TG, low HDL-C subgroups Normolipidemic subgroups

Severe HTG: emerging therapiesdrug class mechanism of

action

advantages disadvantages

MTP inhibition

(lomitapide)

Prevents lipoprotein

precursor lipidation

Small molecule

Reduces TG by 30-40%

Nausea, diarrhea, LFTs; fatty

liver; high cost

LPL gene Rx

(alipogene tiparvovec)

Introduces normal LPL

gene into LPL-

deficient tissues

One time IM injection;

Improves CM kinetics

No enduring effect

LPL deficiency only

DGAT1 inhibition

(several)

Prevents TG

synthesis/re-synthesis

Small molecule

Reduces TG by up to 80%

GI side effects

Possible cross-reactivity with

DGAT2

APOB mRNA

interference

(mipomersen)

Prevents synthesis of

apo B-containing

lipoproteins

Subcutaneous

administration; reduces

atherogenic lipoproteins

Limited efficacy in CM;

injection site reactions, flu-

like symptoms

APOC3 mRNA

interference (ISIS

304801)

Increases LPL activity

and reduces TG-rich

lipoprotein production

Genetically validated

target; reduces TG by up to

70% in chylomicronemia

Limited long term efficacy

and safety data

ANGPTL3 mRNA

interference (ISIS)

Promotes LPL activity Genetically validated target Limited long term efficacy

and safety data

Brahm AJ, Hegele RA. Nat Rev Endocrinol 2015; epub ahead of print

CVD in HTG

severe HTG registry1: SMRadj CHD 3.27 (2.28, 4.55)

1. Neil HAW et al. Atheroscler 2010; 211:618-23.

2. Miller M et al. JACC 2008; 51:724-30.

3. Sarwar N et al. Circulation 2007; 115:450-8.

4. Nordestgaard B et al. JAMA 2007: 298:299-308.

5. Bansal S et al. JAMA 2007; 298: 309-16.

6. Wittrup HH et al. Circulation 1999; 99:2901-7.

7. Sarwar et al. Lancet 2010; 375:1634-9.

8. Do R et al. Nat Genet 2013; 45:1345-52.

9. Crosby J et aI. NEJM 2014; 371:22-31.

10. Jorgensen AB et al. NEJM 2014; 371: 32-41.

11. Do R et al. Nature 2015; 518: 102-6.

on-Rx TG <1.7 mmol: lower CHD events2

epidemiology: fasting3; non-fasting TG4,5

genetics: common LPL GOF/LOF DCHD6

common APOA5 LOF higher CHD7

common 44 SNPsadj higher CHD8

APOC3 LOF lower CHD9,10

APOA5 LOF higher CHD11

Summary: evidence for role in CVD

LDL HDL TG

epidemiologic ++++ ++++ ++

mechanistic: in vitro ++++ ++++ ++

mechanistic: in vivo ++++ +++ ++

genetic - common ++++ +/- +++

genetic - rare ++++ +/- ++

clinical trials ++++ +/- +

Summary: evidence for role in CVD

LDL HDL TG TG+HDL

epidemiologic ++++ ++++ ++ ++++

mechanistic: in vitro ++++ ++++ ++ ++++

mechanistic: in vivo ++++ +++ ++ ++++

genetic - common ++++ +/- +++ ++++

genetic - rare ++++ +/- ++ ++++

clinical trials ++++ +/- + ++