CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 7, August 2013
266
AFRICA
diabetes in the Japanese population. They concluded that
hyperhomocysteinaemia in diabetes mellitus may contribute
to the development of chronic complications. Vayá
et al
.
established a borderline statistically significant association (
p
=
0.008) between hyperhomocysteinaemia and hyperglycaemia (
p
=
0.054).
15
Hypertension is a condition where the artery walls are stiffer
and present increased resistance to blood flow. This requires the
heart to beat more forcefully and increases the pressure of blood
leaving the heart. High blood pressure is often called the silent
killer because in the initial stages it presents with no symptoms.
It is only after an organ in the body has been irritated or damaged,
that the consequences of high blood pressure are realised.
16
Hypertension places stress on the target organs, including
kidneys, eyes and heart, causing them to deteriorate over
time. Hypertension contributes to 75% of all strokes and heart
attacks.
17
One in three African-Americans has hypertension. One
African-American dies every hour from the disease, and more
than 30% of African-Americans can count hypertension or its
complications as the leading cause of death.
17
The hypothesis that homocysteine may play a role in the
pathogenesis of essential hypertension is based on the fact that
homocysteine induces arteriolar constriction, renal dysfunction
and increased sodium reabsorption, increasing arterial stiffness.
18
Homocysteine increases oxidative stress, which causes oxidative
injury to the vascular endothelium, diminishing vasodilation
by nitric oxide, stimulating proliferation of vascular smooth
muscle cells and altering the elastic properties of the vascular
wall, leading to an increase in hypertension.
18
These authors
concluded that homocysteine may contribute to blood pressure
elevation. Atif
et al
. observed that plasma homocysteine was
raised in most patients with hypertension.
19
The authors found
in their study that 80% of their hypertensive subjects were
hyperhomocysteinaemic.
Karatela and Sainani found a high prevalence of
hyperhomocysteinaemia associated with raised blood pressure,
with raised systolic and diastolic pressures.
10
Nabipour
et
al
. reported significantly higher homocysteine levels in
subjects with high blood pressure.
20
Vayá
et al
. however found
no statistically significant association (
p
=
0.008) between
hyperhomocysteinaemia and hypertension (
p
=
0.229).
15
In large community-based studies, plasma homocysteine was
found to be cross-sectionally associated with blood pressure,
especially systolic pressure, unadjusted for gender and age.
21,22
The authors however found that adjusted for gender and age,
the relationship of plasma homocysteine to the incidence of
hypertension was statistically non-significant.
Experimental investigations evaluating the association of
homocysteine and blood pressure have not yielded consistent
results. Diet-induced hyperhomocysteinaemia has been
demonstrated to elevate blood pressure in some investigations
but to lower it in others.
21
A positive association of total
homocysteine with both systolic and diastolic blood pressure
was reported in several clinical cross-sectional studies.
21
These
authors found no major relationship between baseline plasma
homocysteine level and incidence of hypertension.
Lipids are a group of organic compounds that include, among
others, cholesterol, triglycerides, phospholipids, lipoprotein and
sterols, which are insoluble in water but soluble in non-polar
organic solvents.
23
Fats (solid lipids) constitute approximately
34% of the energy used in the human body.
24-26
Of the lipids,
triglycerides and cholesterols [very low-density lipoprotein
(LDL), LDL and high-density lipoprotein (HDL) cholesterol]
are the components that play a major role in atherosclerosis, the
forerunner of arteriosclerosis.
27
All body cells are capable of LDL cholesterol (LDL-C)
synthesis. This favours deposition of cholesterol in the cells and
blood vessels. LDL-C is therefore atherogenic. HDL transports
cholesterol from the cells to the liver for degradation into bile
salts (sodium taurocholate and deoxycholate).
23
HDL-C is
therefore anti-atherogenic and protective against the development
of atherothrombosis.
High triglyceride levels are significant risk factors for
cardiovascular disease and are a marker for atherogenic remnant
lipoprotein, such as very LDL-C. Even in the presence of tightly
controlled LDL-C levels, evidence indicates that high triglyceride
levels and low HDL-C levels are independent thrombosis and
cardiovascular risk factors.
28
About half of all deaths in developed
countries are caused by homocysteinaemia and dyslipidaemia
(hypercholesterolaemia and hypertriglyceridaemia).
29
According to Rima and Wolfgang, there is an association
between hyperhomocysteinaemia and dyslipidaemia, and
diabetes mellitus is common to hyperhomocysteinaemia
and hypercholesterolaemia.
30
Vayá
et al
. found no
statistically significant association (
p
=
0.008) between
hyperhomocysteinaemia and low HDL-C levels (
p
=
0.491)
and hypertriglyceridaemia (
p
=
0.490).
15
However, Nabipour
et al.
found subjects with lower HDL-C levels had higher
homocysteine levels (
p
=
0.001).
20
Obesity is characterised by excess body fat due to an
imbalance between calorie intake and expenditure. Causes of
obesity include high calorie intake, lack of exercise and genetic
susceptibility or psychiatric illness.
31
Obesity is defined as a
body mass index (BMI) greater than 30 kg/m
2
.
32
Two patterns of obesity are central (visceral) obesity and
peripheral obesity. The former is more common in males and
carries a higher risk of coronary heart disease, as well as various
forms of metabolic derangement, including dyslipidaemia and
impaired glucose tolerance. Peripheral obesity is when fat
accumulates in the gluteo-femoral area. It is more common
in women but less associated with cardiovascular risk, as a
complication of arterial thrombosis.
33
Obesity is an independent
risk factor for the complications of atherosclerotic vascular
disease, such as myocardial infarction and stroke and has been
found to elicit and increase the risk of arterial thrombosis.
6,34
Obesity affects about 1.3 billion people worldwide, and 3.0 to
20.4% of South African males and 25.9 to 54.3% of females.
32,35
Karatela and Sainani observed an increased prevalence of
hyperhomocysteinaemia in overweight and obese subjects.
10
Nabipour
et al.
found no significant association between
homocysteine level and BMI in a study of the relationship
between the metabolic syndrome and homocysteine levels.
20
However, Vayá
et al
. found in four studies that increased
homocysteine levels were related mostly to abdominal obesity.
15
Sanlier and Yabanci found increased body weight to be
associated with hyperhomocysteinaemia, but without gender
differences.
36
El-Sammak
etal.
alsofoundhyperhomocysteinaemia
to increase with age, possibly because of the presence of other
factors that raise plasma total homocysteine levels with age,
especially increased deterioration in other organ functions.
37
