C H A P T E R 4 7
Lipid-lowering agents
731
Risk factors
Strong evidence exists that atheroma development occurs
more quickly in individuals with elevated cholesterol
and lipid levels. People who consume high-fat diets are
more likely to develop high lipid levels. However, indi-
viduals without increased lipid levels can also develop
atheromas leading to CAD, so other factors evidently
contribute to this process. Although the exact mecha-
nism of atherogenesis (atheroma development) is not
understood, certain
risk factors
increase the likelihood
that a person will develop CAD. Metabolic syndrome
occurs when a person has several risk factors: increased
insulin resistance, high blood pressure, altered lipid
levels and a proinflammatory and prothrombotic state,
which seem to increase the risk of CAD development
dramatically. Unmodifiable and modifiable risk factors
are presented in Box 47.1. Different ethnic groups also
have different risk factors, as discussed in Box 47.2, as
do different genders, as discussed in Box 47.3.
Treatment
Because an exact cause of CAD is not known, success-
ful treatment involves manipulating a number of these
risk factors (see Table 47.2). Overall treatment and pre-
vention of CAD should include the following measures:
decreasing dietary fats (decreasing total fat intake and
limiting saturated fats seems to have the most impact on
serum lipid levels); losing weight, which helps to decrease
insulin resistance and the development of type 2 diabetes;
eliminating smoking; increasing exercise levels; decreas-
ing stress; and treating hypertension, diabetes and gout.
■■
CAD is the leading cause of death in the Western
world. It is associated with the development of
atheromas or plaques in arterial linings that lead to
narrowing of the lumen of the artery and hardening
of the artery wall, with loss of distensibility
and responsiveness to stimuli for contraction or
dilation.
■■
The cause of CAD is not known, but many
contributing risk factors have been identified,
including increasing age, male gender, genetic
predisposition, high-fat diet, sedentary lifestyle,
smoking, obesity, high stress levels, bacterial
infections, diabetes, hypertension, gout and
menopause. The presence of many of these factors
constitutes metabolic syndrome.
■■
Treatment and prevention of CAD are aimed at
manipulating the known risk factors to decrease
CAD development and progression.
KEY POINTS
FAT AND BIOTRANSFORMATION
(METABOLISM)
Fats are taken into the body as dietary fats, then broken
down in the stomach to fatty acids, lipids and choles-
terol (Figure 47.1). The presence of these products in the
duodenum stimulates contraction of the gallbladder and
the release of bile.
Bile acids
, which contain high levels
of
cholesterol
(a fat), act like a detergent in the small
intestine and break up the fats into small units, called
micelles, which can be absorbed into the wall of the
small intestine. (Imagine ads for dishwashing detergents
that break up the grease and fats in the dishwashing
water; bile acids do much the same thing.) The bile acids
are then reabsorbed and recycled to the gallbladder,
where they remain until the gallbladder is again stimu-
lated to release them to facilitate fat absorption.
Fats and water do not mix and cannot be absorbed
directly into the plasma. To allow absorption, micelles
are carried on a
chylomicron
, a package of fats and
proteins. This packaging is done by brush enzymes in
Variations in lipoprotein levels
Australia and New Zealand both have high incidences
of coronary artery disease. Certain risk factors are
known to place particular cultural groups at higher risk
than national averages. Amongst the ethnic groups in
New Zealand, death rates of Pacific people are higher
than in Ma– ori in hypertensive disease, cerebrovascular
disease and cardiomyopathy (males).The CHD death
rate in Ma– ori men has fallen since 1996, but risen in
women while rates in Pacific people have increased in
both men and women. (Source:
.
org.nz.Technical Report 82: Cardiovascular Disease in
New Zealand, 2004: A Summary of Recent Statistical
Information.)
In Australia, Indigenous Australians have been
reported to have three times the rate of death from
major coronary events than other Australians. (AIHW
2010. Australia’s health 2010. Cat. no. AUS 122. Canberra:
AIHW.)
There are identified cultural variations in lipid levels
as well. Cultural variations in key lipid parameters have
been identified in the specific ethnic groups below;
however, currently no data exist for Pacific Islander,
Ma– ori people or Indigenous Australians in relation to
lipid profiles.
Cultural variations in key lipid parameters include the
following:
• Serum cholesterol levels: whites > African Americans,
Native Americans
• High-density lipoprotein (HDL) levels: African
Americans, Asians > whites
• Low-density lipoprotein (LDL) levels: African Americans
< whites
• HDL: cholesterol ratio: African Americans < whites
Cultural considerations
BOX 47.2
