C H A P T E R 4 7
Lipid-lowering agents
733
unit in the formation and maintenance of cell mem-
branes. Cholesterol is usually provided through the diet
and the fat metabolism process just described. If dietary
cholesterol falls off, the body is prepared to produce
cholesterol to ensure that the cell membranes and the
endocrine system are intact.
Every cell in the body has the metabolic capability
of producing cholesterol. The enzyme
hydroxymethyl-
glutaryl-coenzyme A (HMG-CoA) reductase
regulates
the early, rate-limiting step in the cellular synthesis of
cholesterol. If dietary cholesterol is severely limited, the
cellular synthesis of cholesterol will increase.
Hyperlipidaemias
When the levels of lipids in the blood increase, hyperlip-
idaemia occurs. This can result from excessive dietary
intake of fats or from genetic alterations in fat metab-
olism leading to a variety of elevated fats in the blood
(e.g. hypercholesterolaemia, hypertriglyceridaemia,
alterations in LDL and HDL concentrations). Cultural
variations related to lipid levels have also been identified
(see Box 47.4).
-used as energy
-absorbed into circulation
-atheroma develops
-injured vessel
-inflame vessel
-becomes remnants
To heart—enter circulation
and reach periphery—stored
as fat
Chylomicrons absorbed
into lymphatic system
7
8
Liver processes fats
to LDLs, HDLs—enter
circulation and reach
periphery
9
Micelles absorbed into
small intestine wall,
packaged as chylomicrons
6b
Bile recycled to liver
5
Bile breaks fat into
micelles
6a
Dietary fats
1
Stomach
2
Small intestine
3
Gallbladder contracts
and relases bile into
small intestine
4
FIGURE 47.1
Metabolism of fats in the body.
Rosuvastatin and Asian people
Rosuvastatin reaches higher serum levels in Asian
people than in other populations. Higher serum levels
are associated with an increased risk for rhabdomyolysis.
It is recommended that this drug be reserved for use in
non-Asian people.
Dietary modifications are often successful in treating
hyperlipidaemia that is caused by excessive dietary intake
of fats. Drug therapy is needed if the cause is genetically-
linked alterations in lipid levels or if dietary limits do not
decrease the serum lipid levels to an acceptable range.
The NHF (2012) recommends the following standard
goals for lipid levels: LDLC <1.8; HDLC >1.0;TG <2.0;
and NHDLC <2.5. Antihyperlipidaemic agents such as
bile acid sequestrants, HMG-CoA inhibitors, fibrates,
niacin, cholesterol absorption inhibitors and, in some
cases, hormones (in women) may be used.These drugs
are often used in combination and should be part of an
overall healthcare regimen that includes exercise, dietary
restrictions and lifestyle changes.
See the Critical thinking scenario for additional
information on treating hyperlipidaemia.
Cultural considerations
BOX 47.4
