Glossary

ABCA1	ATP-binding cassette transporter A1, a cell membrane transporter that facilitates the delivery of cholesterol from cells to lipid-poor apolipoprotein A-I in the extracellular space.
ABCG1	ATP-binding cassette transporter G1, a cell membrane transporter that promotes the transfer of cholesterol from cells to large alpha-migrating, spherical HDL.
ApoA-I	Apolipoprotein A-I, the main protein in HDL that accounts for about 70% of the total HDL protein. Atheroprotective lipoprotein; important function in promoting the efflux of cholesterol from cells, and has anti-oxidant and anti-inflammatory properties.
ApoA-I_Milano	A variant of apoA-I with potent cholesterol efflux capacity
ApoA-I mimetics	Investigational agents that mimic the effect of apoA-I
ApoA-II	Apolipoprotein A-II, the second main protein in HDL that accounts for about 20% of the total HDL protein. Although its main function is not known, apoA-II increases the stability of the HDL particle
ApoA-IV	Apolipoprotein IV, the third most abundant HDL apolipoprotein. ApoA-IV is distinct from apoA-I and apoA-II because a significant proportion of it can dissociate readily from HDL and circulates in a lipid-free form
ApoB	Apolipoprotein B, the main protein component of LDL; atherogenic lipoprotein
Atherogenic	Promoting atherosclerosis
Atheroprotective	Protecting against atherosclerosis
Atherosclerosis	An inflammatory disorder that is caused by the accumulation of atherogenic lipoproteins in the artery wall
Cholesterol	A soft fatty waxy substance transported in the blood by lipoproteins. It is also present in all cells in the body. Cholesterol is used in producing cell membranes and some hormones, as well as other functions in the body
CETP	Cholesteryl ester transfer protein. This is involved in redistribution of cholesteryl esters from HDL, where they are formed, to other plasma lipoprotein fractions. Plays a major role in the metabolism and remodelling of HDL
Discoidal HDL	Two or three molecules of apolipoprotein A-I, the main protein component of HDL, plus phospholipid with or without unesterified cholesterol. A nascent form of HDL that exist only transiently before being converted to spherical HDL
Dyslipidaemia	Abnormalities in lipid metabolism
Fibrates	Fibrates mainly reduce triglycerides, as well as reducing LDL cholesterol and increasing HDL cholesterol (by 5-20%). These agents work by activating peroxisome proliferator-activated receptors (Jane—some fibrates also activate PPAR beta/gamma and delta. Rather than get into this it may be better to simply say they activate PPARs
HDL	High-density lipoprotein, the smallest and most dense of the plasma lipoproteins. HDL are categorised 1) on the basis of density: HDL₂< HDL₃ 2) on the basis of size: HDL2_b>HDL2_a>HDL3_a>HDL3_b>HDL3_c 3) on the basis of apolipoprotein composition: A-I HDL (apoA-I only) and A-I/A-II HDL (both apoA-I and apoA-II) 4) on the basis of surface charge: alpha-migrating (spherical HDL) and pre-beta-migrating (discoidal HDL and lipid-poor apoA-I)
HDL cholesterol	High-density lipoprotein cholesterol, good cholesterol. HDL cholesterol is a powerful inverse predictor of coronary heart disease
HL	Hepatic lipase, a triglyceride lipase. HDL triglyceride is the preferred substrate
Hypomorphic allele	An allele that reduces the expression of its target protein without eliminating it entirely.
LCAT	Lecithin:cholesterol acyltransferase; an enzyme that catalyses the esterification of cholesterol in HDL, and accounts for most of the cholesteryl esters that circulate in the plasma. Plays a major role in the metabolism and remodelling of HDL
LDL cholesterol	Low-density lipoprotein cholesterol; bad cholesterol
Lipid-poor apoA-I	A single molecule of apolipoprotein A-I, the main protein component of HDL, with a few molecules of phospholipid
Lipoprotein	Protein that carries cholesterol in the blood
Lipoprotein(a); Lp(a)	A genetic variant of low-density lipoprotein. An increased level is associated with increased risk of heart disease
Lipoprotein lipase	A triglyceride lipase that hydrolyses triglycerides in very low-density lipoproteins and chylomicrons in a process that is accompanied by the transfer of phospholipids and apolipoproteins to HDL
LXR	Liver X receptor agonist, an investigational agent that is a potent inducer of ABCA1
Metabolic syndrome	A cluster of abnormalities including central obesity, insulin resistance, dyslipidaemia, mild hypertension and a pro-inflammatory state
Nicotinic acid (niacin)	A form of vitamin B3, a naturally occurring vitamin. Nicotinic acid is the most potent drug available for raising HDL cholesterol (by up to 30%)
Plaque	A build-up of fatty substance in the inner lining of the artery
PLTP	Phospholipid transfer protein. This is involved in the transfer of phospholipids between HDL and other plasma lipoprotein fractions. Plays a major role in the metabolism and remodelling of HDL
PON	Paraoxonase, an important anti-oxidant that circulates in the plasma mainly bound to HDL particles
PPAR	Peroxisome proliferator-activated receptor, a nuclear transcription factor
Risk factors	Conditions that increase the individual’s risk of developing heart disease
SIP	Sphingosine-1-phosphate (SIP), a sphingolipid constituent of HDL that is responsible for vasodilatory effects
Spherical HDL	Two or three molecules of apolipoprotein A-I, the main protein component of HDL, plus phospholipid, unesterified cholesterol, cholesteryl esters and triglyceride, with or without apolipoprotein II. Most HDL exists in spherical form.
SR-B1	Scavenger receptor B1, an HDL receptor present mainly in the liver (as well as extraheptic tissue), that promotes selective uptake of HDL cholesterol
Total cholesterol	Sum of all cholesterol types in the blood
Triglycerides	A form of fat that comes from food and is also made in the body
VLDL	Very low-density lipoprotein
ACCORD	Action to Control Cardiovascular Risk in Diabetes. A substudy is investigating the effect of combination treatment with fenofibrate and simvastatin on clinical outcome in subjects with or at risk of cardiovascular disease
AIM-HIGH	Atherothrombosis Intervention in Metabolic Syndrome with Low HDL-cholesterol/High Triglyceride and Impact on Global Health Outcomes. This study is evaluating the effect of combination treatment with prolonged-release nicotinic acid and simvastatin on clinical outcome in subjects with cardiovascular disease and low HDL cholesterol and elevated triglycerides
ARBITER 2 and 3	ARterial Biology for the Investigation of the Treatment Effects of Reducing Cholesterol. These studies evaluated the effect of combination treatment with prolonged-release nicotinic acid and a statin for 1-2 years on progression of atherosclerosis in subjects with low HDL cholesterol and coronary heart disease. A surrogate cardiovascular endpoint, carotid intima-media thickness, was the primary endpoint
BIP	Bezafibrate Infarction Prevention study, a secondary prevention trial with bezafibrate in men
DAIS	Diabetes Atherosclerosis Intervention Study, a study in subjects with type 2 diabetes designed to investigate the effect of fenofibrate treatment on angiographic parameters of atherosclerosis
FIELD	Fenofibrate Intervention and Event Lowering in Diabetes study in patients with type 2 diabetes (78% with no prior cardiovascular disease).
HATS	HDL-Atherosclerosis Treatment Study. This study evaluated the effect of combination treatment with immediate-release nicotinic acid and simvastatin on angiographic measurements of atherosclerosis progression in subjects with coronary heart disease
HHS	Helsinki Heart Study, a primary prevention trial in men with gemfibrozil
ILLUMINATE	Investigation of Lipid Level Management to Understand Its Impact in Atherosclerotic Events in subjects with or at high risk of coronary heart disease; a trial involving torcetrapib
ILLUSTRATE	Investigation of Lipid Level Management Using Coronary Ultrasound to Assess Reduction of Atherosclerosis by CETP Inhibition [using torcetrapib] and HDL Elevation
PROCAM	Prospective Cardiovascular Münster study. An observational study that showed an inverse relationship between HDL cholesterol and coronary heart disease risk
RADIANCE	Rating Atherosclerotic Disease Change by Imaging with a New CETP inhibitor [torcetrapib] in patients with heterozygous familial hypercholesterolaemia (RADIANCE 1), or mixed dyslipidaemia (RADIANCE 2).
VA-HIT	Veterans Affairs HDL Intervention Trial, a secondary prevention trial with gemfibrozil in men with low levels of LDL cholesterol and HDL cholesterol

HDLForum

Glossary

Editors

Professor Kerry-Anne Rye

Professor Philip Barter

Professor John Chapman