C H A P T E R 4 7
Lipid-lowering agents
747
■■
Fats are metabolised with the aid of bile acids, which
act as a detergent to break fats into small molecules
called micelles. Micelles are absorbed into the
intestinal wall and combined with proteins to become
chylomicrons, which can be transported throughout
the circulatory system.
■■
Some fats are used immediately for energy or are
stored in adipose tissue; others are processed in
the liver to LDLs, which are associated with the
development of CAD. LDLs are broken down in the
periphery and leave many remnants (e.g. fats) that
must be removed from blood vessels. This process
involves the inflammatory reaction and may initiate
or contribute to atheroma production.
■■
Some fats are processed into HDLs, which are able to
absorb fats and remnants from the periphery and offer
a protective effect against the development of CAD.
■■
Cholesterol is an important fat that is used to make
bile acids. It is the base for steroid hormones and
provides the necessary structure for cell membranes.
All cells can produce cholesterol.
■■
HMG-CoA reductase is an enzyme that controls the
final step in the production of cellular cholesterol.
■■
People taking lipid-lowering drugs need to include
diet, exercise and lifestyle changes to reduce the risk
of CAD.
■■
Bile acid sequestrants bind with bile acids in the
intestine and lead to their excretion in faeces. This
results in lower bile acid levels as the liver uses
cholesterol to produce more bile acids. The end result
is a decrease in serum cholesterol and LDL levels as
the liver changes its metabolism of these fats to meet
the need for more bile acids.
■■
HMG-CoA reductase inhibitors, or statins, block
the enzyme HMG-CoA reductase, resulting in lower
serum cholesterol levels, a resultant breakdown of
LDLs and a slight increase in HDLs.
■■
The cholesterol absorption inhibitor ezetimibe works
in the brush border of the small intestine to prevent
the absorption of dietary cholesterol, which leads to
increased clearance of cholesterol by the liver and a
resultant fall in serum cholesterol.
■■
Other agents used to lower cholesterol include fibrates
and nicotinic acid. Often lipid-lowering agents are
used in combination to lower the cholesterol at
different sites.
■■
Research is being done on the effects of blocking
the endocannabinoid system, resulting in weight
loss, improved lipid profiles and decreased
proinflammatory and prothrombotic states.
Questions have not been answered about the safety
or effectiveness of drugs that block this system.
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ONLINE RESOURCES
An extensive range of additional resources to enhance teaching
and learning and to facilitate understanding of this chapter may
be found online at the text’s accompanying website, located on
thePoint at
These include Watch and
Learn videos, Concepts in Action animations, journal articles,
review questions, case studies, discussion topics and quizzes.
WEB LINKS
Healthcare providers and students may want to consult
the following Internet sources:
Information on research, alternative methods of
therapy and pharmacology.
Information on research, alternative methods of
therapy and pharmacology.
/
simvastinsept2011.htm
New Zealand Medicines and Medical Devices
Authority.
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