SA JOURNAL OF DIABETES & VASCULAR DISEASE
DRUG TRENDS
VOLUME 7 NUMBER 1 • MARCH 2010
39
Southern African Hypertension Society congress report,
Johannesburg, 2010
Hypertension in low- and middle-
income countries
Prof YK Seedat, Emeritus Professor, Univer-
sity of KwaZulu-Natal, Durban
Cardiovascular disease accounts for 30%
of the global mortality and much of the
disease burden is carried by the developing
word. Cardiovascular disease is common in
sub-Saharan Africa, India and Saudi Arabia,
and the prevalence is rising all the time. Both
the public health and risk-factor burdens are
underestimated, and 80% of the attribut-
able health burden is carried by the devel-
oping world. This is according to Prof YK
Seedat of the University of KwaZulu-Natal.
‘Both race and ethnicity are fundamen-
tal markers of lifelong variations in lifestyle,
rather than variations in genetics’, he said.
‘Sub-Saharan Africa is the poorest region
in the world with the biggest gap between
rich and poor. Lower income correlates
with lower life expectancy.’
‘Blood pressure-related diseases are
therefore a global health priority but the
absence of appropriate primary healthcare
services is a major obstacle to addressing
the problem effectively in low- and mid-
dle-income countries. Consequently there
are low levels of awareness, treatment
and control. Low-cost hypertension pro-
grammes are urgently needed.’
The problem will get worse. ‘Hyperten-
sion will continue to rise in the developing
world as a result of ongoing urbanisation,
increased tobacco use, dietary changes and
growing obesity. Ischaemic heart disease is
anticipated to be the leading cause of the
disease burden in developing countries by
2020. It’s beyond the scope of these coun-
tries to address all the risk factors, as the
expensive investigations and drugs required
are simply unavailable. Additional barriers
include competing priorities such as HIV/
AIDS, inadequate epidemiological data and
a failure to recognise the importance and
cost-effectiveness of preventive strategies.’
Looking to the future, Prof Seedat feels
that ‘primordial prevention’ is critical. ‘We
need to decrease the social, economic
and cultural determinants of hyperten-
sion through non-pharmacological lifestyle
measures, of which dietary salt restriction
is probably the most important. These
changes need to be encouraged from an
early age. At the same time, we need to
address the poor presentation of the nec-
essary messages from government and the
media. And all of this needs to done as
cost-effectively as possible because most
sub-Saharan African countries have severe
resource constraints.’
Prof Seedat cited a World Health Organ-
isation (WHO) recommendation that the
higher the risk, the more intensive inter-
vention should be – and that it needs to be
delivered equitably at primary healthcare
level. ‘We need to increase the efficiency
and volume of pharmaceutical production,
ensure that patients receive the lowest
effective dose, publicise the lowest prices
and stimulate competition’, he concluded.
The renin–angiotensin system of
adipose tissue highlights a greater
role for RAAS blockers in treating
hypertension in the metabolic
syndrome
Prof Rhian Touyz, Ottawa Hospital Research
Institute, Canada
Obesity and nutrient overload results in
dysfunctional adipocytes that cause vascu-
lar injury through the release of angiotensin
II and pro-inflammatory cytokines.
‘The presence of a functional RAAS
system in adipocytes clearly plays an
important role in normal physiology.
Recent research
1
on human arteries has
shown that adipocytes from healthy adi-
pose tissue secrete adiponectin, which is
the main modulator of vascular tone, by
increasing nitric oxide bioavailability’, Prof
Rhian Touyz pointed out. ‘In obesity, the
perivascular adipose tissue (PVAT) becomes
dysfunctional and promotes hyper-reactive
endothelial function and inflammation –
essentially the same features as are seen in
the vascular phenotype of hypertension.’
This is important for antihypertensive
drug selection and raises the profile of
agents that are blockers of the RAAS system
(Table 1). Interestingly, recent evaluation of
antihypertensive drugs with regard to the
release of adiponectin from adipocytes
2
has shown that telmisartan, and to a lesser
extent losartan, increased production and
secretion of adiponectin compared to thi-
azides, atenolol, captopril and nifedipine.
The protective effect of telmisartan in
patients with the metabolic syndrome is
also due to decreased insulin resistance
and increased adipocyte differentiation.
3
Patients gain less weight on telmisartan
than on other ARBs such as valsartan; a
further important factor to consider when
treating obese and overweight patients.
4
Recent clinical research in patients,
5
using
computer tomography to measure visceral
fathasalsoshownthattelmisartantreatment
reduced visceral obesity in treated patients.
Greenstein AS, Khavandi K, Withers SB,
1.
Sonoyama K, Clancy O,
et al
.
Circulation
2009;
119
(12): 1661–1670.
Brody R, Peleg E, Grossman E, Sharabi Y.
2.
Am
J Hypertens
2009;
22
(10): 1126–1129.
Janki J, Schapp M,
3.
et al
.
J Hypertens
2006;
24
(9): 1809–1816.
Sugimoto K,
4.
et al
.
Hypertension
2006;
47
:
1003–1009.
Shimobukuro,
5.
et al
.
J Hypertens
2007;
25
(4):
841–848.
Lessons from the Canadian
Hypertension Education Program
(CHEP) guidelines
Prof Rhian Touyz, Ottawa Hospital Research
Institute, Canada
Prof Rhian Touyz reviewed the recently
published 2009 CHEP guidelines, which
are updated annually. ‘The WHO is placing
a great emphasis on reducing the global
hypertension burden, which is projected to
increase by 60% between now and 2025’,
Table 1.
Relationship between obesity and the
RAAS
Abdominal obesity and ectopic fat deposition
•
is the key determinant of the metabolic
syndrome
Reducing abdominal obesity and ectopic fat
•
reduces all components of the metabolic
syndrome
Increased RAAS in obese patients with the
•
metabolic syndrome improves adipocyte tissue
function and adipocyte differentiation, thereby
reducing visceral abdominal obesity.
