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Low density lipoprotein
From Wikipedia, the free encyclopedia.
Low-density lipoprotein (LDL) refers to a class and range of
lipoprotein particles, varying somewhat in their size and contents,
which carry cholesterol in the blood and around the body, for use by
various cells.It is the final stage of VLDL (very low-density
lipoprotein) which is produced by the liver. The LDL contains the
apoprotein B-100 (Apo B-100) among is plasma lipids. It is commonly
referred to as “bad cholesterol” due to the link between high LDL
levels and cardiovascular disease.
Contents [hide]
1 Function
2 Role in disease
3 Recommended range
4 LDL Subtype Patterns

5 References
6 See also
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Function
Generally, LDL transports cholesterol and triglycerides away from
cells and tissues that produce more than they use, towards cells and
tissues which are taking up cholesterol and triglycerides.
[edit]
Role in disease
Because LDL transports cholesterol to the arteries, increased levels
are associated with atherosclerosis, and thus myocardial infarctions,
strokes and peripheral vascular disease. This is why cholesterol
inside LDL lipoproteins is called bad cholesterol. Still, it is not
the cholesterol that is bad; it is instead how and where it is being
transported, and in what amounts over time.
Increasing evidence has revealed that the concentration and size of
the LDL particles more powerfully relates to the degree of
atherosclerosis progression than the concentration of cholesterol
contained within all the LDL particles. Having low concentrations of
large LDL particles is the healthy pattern. Conversely, high
concentrations of small LDL particles, despite the same total
cholesterol content correlates with much faster growth of atheroma
and progression of atherosclerosis.
LDL is formed as VLDL lipoproteins lose triglyceride through the
action of lipoprotein lipase (LPL), and become smaller and denser
containing a higher proportion of cholesterol.
A hereditary form of high LDL is familial hypercholesterolemia (FH).
Increased LDL is termed hyperlipoproteinemia type II (after the dated
Fredrickson classification).
[edit]
Recommended range
The American Heart Association, NIH and NCEP provide a set of
guidelines for fasting LDL levels and risk for heart disease.
Level mg/dl Level mmol/L Interpretation
<100 <2.6 Optimal LDL cholesterol, corresponding to reduced risk for
heart disease
100-129 2.6-3.3 Near optimal LDL level
130-159 3.3-4.1 Borderline high LDL level
160-189 4.1-4.9 High LDL level
Over time, with more clinical research, these recommended levels keep
being reduced. For instance, for people with known atherosclerosis
diseases, the 2004 updated American Heart Association, NIH and NCEP
recommendations are for LDL levels to be lowered to less than 70
mg/dL, unspecified how much lower. It has been estimated from the
results of muptiple human pharmacologic LDL lowering trials that LDL
should be lowered to about 50 to reduce cardiovascular event rates to
near zero. For reference, from longitudinal population studies
following progression of atherosclerosis related behaviors from early
childhood into adulthood, it has been discovered that the usual LDL
in childhood, before the development of fatty streaks is about 35
mg/dL. However, all the above values refer to chemical measures of
lipid concentration, probably not the better approach.
Chemical measures of lipid concentration have long been the clinical
measurement of choice because these lab methods are less expensive
and more widely available. However, there is increasing evidence and
recognition of the value of more sophisticated measurements.
Specifically LDL particle number (concentration), and to a much
lesser extent size, have shown much tighter correlation with
atherosclerotic progression and cardiovascular events than is
obtained using chemical measures of total LDL concentration contained
within the particles. LDL concentration can be low, yet LDL particle
number high and cardiovascular events rates are high. Alternatively,
LDL concentration can be relatively high, yet LDL particle number low
and cardiovascular events are also low. If LDL particle concentration
is tracked against event rates, many other statistical correlates of
cardiovascular events, such as Diabetes Mellitus, obesity and
smoking, loose much their additive predictive power.
[edit]
LDL Subtype Patterns
LDL particles actually vary in size and density, and studies have
shown that a pattern that has more small dense LDL particles –
called “Pattern B” — equates to a higher risk factor for Coronary
Heart Disease (CHD) than does a pattern with more of the
larger “fluffy” LDL particles (”Pattern A”). This is because the
smaller particles are more easily able to penetrate the
endothelium. “Pattern I”, meaning “intermediate”, indicates that most
LDL particles are very close in size to the normal gaps in the
endothelium (approx 260 Angstroms).
The correspondence between Pattern B and CHD has been suggested by
some in the medical community to be much stronger than the
correspondence between the LDL number measured in the standard lipid
profile test. Tests to measure these LDL subtype patterns are not
widely available, so the common lipid profile test is used more
commonly. The lipid profile does not directly measure LDL particles
but instead calculates their value based on other particle lipids via
the Freidwald equation. There has also been noted a correspondence
between higher triglyceride levels and higher levels of smaller,
denser LDL particles and alternately lower triglyceride levels and
higher levels of the larger fluffier LDL. [1] [2]. However, with
ongoing studies, the stronger correlation has been with
quantitatively measured particle concentrations, more so than
particle size and particle lipid content.
[edit]
References
Adult Treatment Panel III Full Report
ATP III Update 2004
HeartPoint: Cholesterol, Advanced Discussion
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See also