Lipids and Atherosclerotic Disease

Decreasing Risk in the New Millennium

Mary Malloy, M.D.

Atherogenic Lipoproteins and HDL

• LDL - Rationale for new treatment goals• Triglyceride-bearing lipoproteins (chylos,

VLDL, IDL) and risk for CVD• HDL - Many species, many roles; low level

as an important risk factor for CVD• Lipoprotein (a) - new insights

LDL Species

• LDL particle diameters distribute in 5 quantized sub-populations; gender offset

• Hepatic lipase -514 polymorphism is a major determinant of LDL diameter

• Most of the “small, dense” LDL effect relates to the level of triglycerides

• Large diameter LDL of FH are atherogenic

LDL-C Elevation: Primary Disorders

• Familial Hypercholesterolemia (1/500)• Familial Combined Hyperlipidemia (1/100)• Ligand Defective apo B-100 (1/500)• Cholesterol 7 alpha Hydroxylase Deficiency• Autosomal Recessive Hypercholesterolemia• PCSK9 (gain of function mutations)

Aggressive Reduction of LDL• Quantitative Angiographic Trials

– FATS, SCOR: regression correlated with LDL reduction

• IVUS Study– ASTEROID: 40 mg resuvastatin, baseline vs. 24mon;

LDL 61(53 % reduction); HDL increased 13.8% on trial; significant reduction in plaque diameter

• Outcomes Trials– TNT: 10,000 men and women with CAD; 80 vs. 10 mg

of atorvastatin for 4.9 years; on trial LDL 77 vs. 101 mg/dL; 22% decreased relative risk in intensively treated group; p<0.001

JUPITER

• Outcome trial - 17,804 individuals with essentially normal lipids but with hsCRP > 2.0 treated with 20 mg resuvastatin vs. placebo. Trial stopped at 1.9 years because significance reached.

• On trial median LDL in treated group 55 mg/dL (vs. 108), HDL 49, TG 118

• Primary endpoint (MI, stroke, unstable angina, revascularization, CV death) reduced by 50%; CRP reduced by 37% (a marker, not an agonist).

LDL - How Low Is Safe?

• Biological model– Heterozygous Familial

Hypobetalipoproteinemia: apoB-100 mutations; PCSK9 deficiency; other

• LDL-C in 20-30 mg/dL range associated with longevity; no adverse effects

• “Natural” vs drug induced - are the effects the same?

PCSK9

• Adjuvant role in LDL endocytosis• Gain of function mutations: Degradation of

LDL receptors - elevated LDL-C (rare)• Loss of function mutations: increased LDL

receptor recycling - reduced LDL-C (25-30 mg/dL) Lifelong low levels of LDL-C; longevity; African Americans

• Plasma levels of PCSK9 can be measured

Achieving LDL Treatment Goals

• Diet: low in saturated fat and cholesterol; zero trans fats; weight control

• Drugs: statins, cholesterol absorption inhibitor, resins, niacin

• Drug combinations: needed to address associated lipoprotein abnormalities or very high LDL-C

• LDL-C goal is 50 at UCSF Lipid Clinic if CAD, PVD, or risk equivalents are present (NCEP goal is 70 and dropping)

Statins - Effects Beyond LDL• Alter cell membranes so as to restrict activity of proteolytic

enzymes that propagate the coagulation cascade• Decrease prenylation of Ras protein (affects many cell

functions)• Anti-inflammatory - associated with reduction in LpPLA2,

hsCRP & SAA (reduction of CRP correlates also with TG reduction); reduce production of inflammatory cytokines (CD40L, IFN-γ, TNF-α, IL-1β, IL-6, IL-8); induce production of anti-inflammatory cytokines (TGF- β,IL-4, IL-10); improved NO release

• Decrease Rho Kinase activity (regulation of LPS-induced platelet-endothelial interactions; NO bioavailability)

KIF6 Arg719 PolymorphismPredicting Statin Efficacy

• Carriers had increased risk (50%) of CHD in 5 prospective studies: ARIC, CHS, WHS, placebo arms of WOSCOPS and CARE

• Carriers had greater statin efficacy in 3 trials: CARE, WOSCOPS, PROVE-IT

• Codes for a molecular motor (a kinesin)• Identification of genotype is available

Statin Myopathy

• Ask the patient about the entire spectrum of muscle complaints (< 5% including all)

• CK elevations: “moderate” > 10X normal; “severe” > 50X normal

• Rhabdomyolosis: evidence of muscle cell destruction or renal failure regardless of CK

• Risk factors include: higher doses, diabetes, polypharmacy, age > 65, ethnicity, female gender, physical activity level, mitochondrial dysfunction, genetics (COQ2, CYP2D6, SLCO1B1 transporter)

Cholesterol Absorption Inhibitor Ezetimibe - Is it “safe”?

• Excellent side effect profile• Only moderately effective in reducing LDL-C• Additive effect with other agents • No increased risk in combined drug Rx• No significant increase in IMT in ENHANCE• SEAS, SHARP, IMPROVE-IT: nominally

significant excess cancer deaths in ezetimibe groups; no increase in cancer incidence

LDL Cholesterol-lowering Drugs in Development

• Apo B antisense drugs • MTP inhibitors - reduce HDL as well as

LDL; GI and liver toxicity (fatty liver)• Squalene synthase inhibitors - elevated liver

enzymes at higher doses• LXR beta agonists• Beta selective (metabolic) thyromemetic

THE FOCUS ON LDL

• Other atherogenic lipoproteins (VLDL, IDL, Lp(a), modified lipoproteins (glycated, oxidized), and the importance of low HDL largely ignored for many years

• Treatment modalities focused on reduction of LDL-C

• Residual risk after LDL-C reduction apparent (65%)

Elevated Triglyceride-rich Lipoproteins

• Important independent risk factor– Framingham, Austin, Rapp and Kane, (others)– IDL most atherogenic (Gofman, Montreal Heart Study)

• Associated with DMII and the “metabolic syndrome”; many secondary causes

• Genetic disorders: LPL or apo CII deficiency; Hepatic lipase deficiency; Dysbetalipoproteinemia

Hypertriglyceridemia

• New disorders at the gene level– GPI anchored HDL binding protein: scaffold

for LPL and its cofactors (mutations probably uncommon)

– Galanin promotor polymorphism (interacts with hypothalamus); transcriptionally regulates LPL

– Apo A-V (mutations common)– Lmf1 (mutations common)

Lmf1 DeficiencyA Novel Disorder

• Critical for post-translational maturation of LPL and HL

• Probable misfolding of proteins - leads to endoplasmic reticulum stress syndrome

• Expressed in tissues that do not express LPL and HL - effects on other proteins

• Unique phenotype: Chylos, VLDL, and IDL increased; pancreatitis and CAD

How Triglycerides Increase Risk of CAD/Stroke

• Increase oxidative stress– Induce endothelial vasomotor dysfunction– Transcriptionally upregulate adhesion molecules, MCP-

1, tissue factor, scavenger receptors• Promote coagulation

– Increase bulk blood viscosity– Factor VII and PAI-1 increased

• Affect metabolism of other lipoproteins– Alter molecular speciation of HDL– Alter LDL particle size and composition

Non-Ischemic Heart Failure and Triglycerides

• Linked to defects in mitochondrial metabolism of lipids in cardiomyocytes

• Apo B-100 synthesized in cardiomyocytes• Carnitine palmitoyltransferase-1 deficiency

– Prototype disorder: accumulation of TG in cardiomyocytes; associated with hyperTG

• Myokines originate in cardiomyocytes

Management of Elevated Triglycerides

• Treatment goals– < 800 mg/dL for prevention of pancreatitis– < 120 mg/dL for prevention of CAD/stroke

• Lifestyle changes– Exercise; diet; eliminate alcohol; weight control

• Eliminate or treat secondary causes• Drug treatment

– PPAR alpha agonists (Marine omega 3s, fibrates), niacin, statins, combined drug treatment

PPAR-alpha Ligands(Fish Oil and Fibrates)

– Increase adiponectin levels, an adipose-specificsecretory protein known to reduce risks of diabetes and CAD

– Direct fatty acids toward consumptive pathways

– Increase transcription of LPL and apo A-I– Involved in remnant removal

Fibrate Combination Therapy

• Avoid fibrate-statin in chronic kidney disease• Fenofibrate is the agent of choice in combination

therapy (gemfibrozil competes with glycosylation step in statin metabolism)

• Use low to moderate doses of statin with fenofibrate

• Avoid fibrate-ezetimibe or fibrate-resin if patient is at high risk for cholelithiasis or it is suspected

• Fenofibrate-niacin is useful to Rx very high TG

Other Agents That Affect Triglycerides

• PPAR gamma agonists: Pioglitizone reduces TG by increasing clearance rate via increased LPL mass and decreased apo CIII production

• PPAR delta agonists: increase fatty acid oxidation; reduce oxidative stress; increase HDL

• FXR agonists: transcriptional regulators that modulate TG production

HDL• Sixteen molecular complexes; 76 proteins (mass spec)• Roles in:

– Reverse cholesterol transport (prebeta 1)– Transport of sex hormones– Support of adrenal steroidogenesis– Central role in inflammation: Antioxidant activity -

sequestration of transition metals; paraoxonase activity– Innate immune functions: sequestration of endotoxins;

inhibition of infectivity of endogenous C viruses; antiprotozoal activity (trypanosomes, leishmania)

– Sphingolipid transport/signaling: sphingosine-1 P involved in platelet/endothelium interaction

DEFICIENCY OF HDLMost important LP Predictor of Risk?

• Women <55; Men <45 mg/dL• Secondary/Related Conditions:

– High TG, obesity, sedentary lifestyle, DMII, metabolic syndrome, myeloma, lymphocytic leukemia, chronic inflammation (SLE, RA), liver toxicity, smoking, high carbohydrate or very low fat intake, certain drugs

GENETIC DEFICIENCY OF HDL

“Familial Hypoalphalipoproteinemia”ABCA1 mutations (homozygous - Tangier)Apo A-I mutationsLCAT Deficiency; PLTP deficiencyWWOX polymorphism (tryptophan-rich domain oxidoreductase)-transcriptional regulator of genes influencing level of HDL

PCPE2 polymorphism associated with low HDL; a protease involved in maturation of apo A-I

HDL - Yin and Yang

• Functionality may be more important than level in determining risk in individuals

• HDL can be pro-atherogenic in inflammatory disorders (diabetes, lupus, rhumatoid arthritis, etc.)

• HDL is abundant in the artery wall: susceptible to oxidation by MPO from PMNs; attacked by proteases from macrophages

• Modified Apo A-I impairs cholesterol efflux via the ATP-binding cassette transporter A-1 pathway

Does Increasing HDL-C Reduce Cardiovascular Risk?

Framingham, Gordon: a 1% increase in HDL-C resulted in 1.3% reduction in risk

Angiographic trials: reduction of progression of stenosis with HDL raising was independent of LDL reduction

Epidemiologic, arteriographic, and clinical trial evidence: increasing HDL-C is as important as LDL-C reduction in reducing events; the effects are additive (meta-analysis of 23 trials)

Treatment of Low HDL

• Eliminate or treat secondary causes• Diet and exercise• Drug treatment

– Niacin; fenofibrate; (statins)– Reduce levels of atherogenic lipoproteins– Understand effects of the drug on HDL composition

and function; new biomarkers? (oxidative modifications and changes in protein composition)

Niacin

• Reduces levels of triglycerides, IDL, Lp(a), and LDL-C; increases levels of HDL-C

• Increases production of apo A-I and may decrease its catabolism; enhances clearance of apoB-100 and apoB-48; inhibits TG synthesis via hepatic DGAT2 inhibition; inhibits lipolysis in adipose tissue via G protein-coupled receptors

• Increases beta oxidation of fatty acids in liver; direct effects on oxidative stress in vascular tissue

• Up-regulates hepatic ABCA1 transporter

Niacin

• Give with close monitoring if DMII presentCDP: niacin Rx equally effective in reducing CV end points in diabetics/non-diabetics

• Avoid in presence of liver disease or active peptic disease• Homocysteine levels increased modestly• AST/ALT may be increased (up to 2 fold)• Monitor for hyperuricemia & Rx as needed• Macular edema - rare, dose-related

NIACINNLA recommendations

• D/C if transaminase levels >3X normal, or <3X normal elevations are associated with elevated bilirubin, nausea, malaise, or fever

• Relatively contraindicated in paroxysmal AF; Established AF is not a contraindication (ventricular response rate not affected); Post cardiothoracic surgery AF is not a contraindication to subsequent use

• Avoid SR niacin in favor of ER or IR (crystalline)

Will Niacin-Statin Combinations Achieve Further CVD Risk Reduction?

• Already evident from meta-analyses of studies with angiographic findings and clinical event reduction

• Ongoing trials: 60-75% risk reduction achievable?AIM-HIGH: 3,300 patients with metabolic syndrome and

CVD; simvastatin vs simvastatin + ER niacinHPS2-THRIVE: 20,000 patients with CAD; simvastatin

vs simvastatin + ER niacin + prostaglandin inhibition

NEW AGENTS TO INCREASE LEVELS OF HDL-C

LXR AGONISTS -– Activate 7 alpha hydroxylase and the

ABCA-1 transporter (associated with HDL formation)

CETP ANTAGONISTS -Impede movement of CE from HDL to other lipoproteins; alter physical/biol properties

NOVEL HDL MIMETICS -A-1 Milano; recombinant Apo A-1

Lipoprotein (a)• Independent risk factor (> 75 nmol/L - Caucasians)• Prolonged half life in artery wall• Promoter of (a) gene contains inflammatory response

element• Inhibits fibrinolysis (binds tPA); reduces fibrin clot

permeability and susceptibility to lysis• Binds oxidized phospholipids; pro-inflammatory• Risk is genotype dependent at one polymorphic site

(I4399M); more important than level vis-a-vis risk• Niacin is the only available treatment; reduce LDL

Apo (a) Variant I4399M

• 3% of US Caucasian population affected– Cardiovascular risk tripled in UCSF study

• Women’s Health Study– Carriers of the variant had doubled

cardiovascular risk– Carriers appeared to benefit more from aspirin

than non-carriers

Lipoprotein (a)

• Implicated in transport of newly described PL adduct - potential involvement in innate immune response

• PL adduct found in cell wall of pneumococcus

• EO6 antibody, innate in humans, reacts with the PL adduct

• J shaped risk curve

Lp(a) in South Asians

• Rates of CAD are 50 to 300% higher than other populations; occurs at younger ages

• Diabetes prevalence is 3 to 6 times higher while other traditional risk factor rates are similar

• Asian Indians have high levels of Lp(a) that correlate independently with age of onset of CAD, severity, progression, and MI

• (African Americans have high levels of Lp(a) but less CAD risk; HDL is higher and TG and LDL are lower

Summary

• Management of most lipid disorders is achievable with lifestyle measures and available drugs; combined drug regimens are often required

• Newly discovered genomic determinants reveal mechanistic elements that will lead to new, individualized venues of treatment

• Qualitative properties of lipoproteins will be important in prediction of risk and management

The Changing Landscape of Lipid Biology

• Inflammation is central to atherogenesis and the generation of unstable plaque leading to MI and stroke

• The biology of lipoproteins is linked to inflammation and the innate immune response