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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 2, March/April 2021
AFRICA
87
The modulating effects of green rooibos (
Aspalathus
linearis
) extract on vascular function and antioxidant
status in obese Wistar rats
Zimvo Obasa, Mignon Albertha van Vuuren, Barbara Huisamen, Shantal Lynn Windvogel
Abstract
Purpose:
Obesity is associated with the development of risk
factors for cardiovascular disease (CVD) and polyphenols
have been shown to possess ameliorative effects against obesi-
ty-induced CVD risk factors. Rooibos (
Aspalathus linearis
)
is rich in polyphenols, therefore we investigated the cardio-
protective effects of aspalathin-rich green rooibos
(GRT) on
obesity-induced CVD risk factors in obese Wistar rats.
Methods:
Adult male Wistar rats (
n
= 20 per group) were fed
a control or a high-fat diet (HFD) for 16 weeks and treated
with GRT (60 mg/kg/day) for six weeks. Blood pressure was
monitored throughout. Vascular reactivity was measured and
Western blots of cell-signalling proteins (eNOS, AMPK and
PKB) were performed in aortic tissues. Effects on oxidative
stress were determined by measuring antioxidant enzyme
activity and thiobarbituric reactive substance (TBARS) levels
in the liver.
Results:
HFD animals had (1) increased blood pressure,
(2) impaired vasodilation, (3) attenuated PKB and AMPK
expression, (4) decreased antioxidant enzyme activity, (5)
increased malondialdehyde (MDA) levels, and (6) increased
phosphorylated eNOS levels. Treatment with GRT extract
significantly alleviated these obesity-induced CVD risk
factors.
Conclusion:
Supplementation with GRT extract alleviated
cardiovascular risk factors in the HFD animals, suggesting a
therapeutic potential for GRT in obesity-induced cardiovas-
cular risk.
Keywords:
obesity, blood pressure, vascular reactivity, oxidative
stress, glucose homeostasis, Afriplex GRT
TM
extract
Submitted 18/6/19, accepted 2/10/20
Published online 18/2/21
Cardiovasc J Afr
2021;
32
: 87–97
www.cvja.co.zaDOI: 10.5830/CVJA-2020-048
Cardiovascular disease (CVD), the leading cause of death
globally, accounted for 17.7 million deaths in 2016, and is mostly
prevalent in low- to middle-income countries.
1
Behavioural risk
factors for CVD include a sedentary lifestyle, tobacco smoking
and alcohol abuse, which manifest as obesity, hypertension,
type 2 diabetes, dyslipidaemia and raised blood glucose levels in
individuals.
2
Obesity is a major global health problem and is on the rise,
especially in developing countries where it is mostly prevalent
in the adult population.
2
It results when there is an energy
imbalance between caloric intake and caloric expenditure,
3
and is
associated with development of the metabolic syndrome (MetS),
a conglomerate of cardiometabolic risk factors that elevate CVD
risk.
4,5
The MetS is characterised by insulin resistance, elevated
blood pressure, impaired glucose homeostasis, atherogenic
dyslipidaemia and systemic inflammation.
4,5
Obesity is also
associated with the development of endothelial dysfunction
6
and
oxidative stress.
7
Rooibos (
Aspalathus linearis
), a leguminous shrub indigenous
to the Cederberg Mountains of the Western Cape in South
Africa, has numerous health-promoting properties, such as
anti-hypertensive,
8
antidiabetic,
9,10
anti-hyperglycaemic,
9-12
anti-
inflammatory,
13
antioxidant,
14
anti-cancer
15
and anti-obesity
effects.
16
This is mainly attributed to its polyphenolic composition,
particularly aspalathin, auniquemajor active flavonoid compound,
and nothofagin, a 3-dehydroxydihydrochalcone glucoside.
12
When the rooibos plant is harvested, it is processed into
fermented (oxidised) and unfermented (un-oxidised) products,
which may be used to make herbal infusions and extracts.
17,18
The unfermented ‘green’ rooibos is commonly used to
prepare aspalathin-rich extracts due to the preservation of its
polyphenolic content.
9
Afriplex GRT
TM
(GRT) extract, a spray-
dried powder with a high aspalathin content, used in this study,
was prepared from unfermented rooibos.
To date, no studies have been performed investigating the
relationship between the ameliorative effects of this GRT extract
on obesity-induced CVD risk factors. Therefore, in view of
the known health benefits of rooibos, we set out to determine
whether GRT extract could improve obesity-induced CVD risk
factors in an animal model.
Methods
Adult male Wistar rats weighing between 150 and 210 g and
approximately seven to eight weeks old were obtained from the
central animal facility of the Faculty of Medicine and Health
Sciences at Stellenbosch University. They were housed in cages
containing four rats per cage and maintained under a 12-hour
day/night cycle at 24–25°C. Animals had
ad libitum
access to
food and water.
Centre for Cardio-metabolic Research in Africa (CARMA),
Division of Medical Physiology, Faculty of Medicine and
Health Sciences, Stellenbosch University, Cape Town,
South Africa
Zimvo Obasa, MSc,
maqeda@sun.ac.zaMignon Albertha van Vuuren, PhD
Barbara Huisamen, PhD
Shantal Lynn Windvogel, PhD
Biomedical Research and Innovation Platform, South
African Medical Research Council, Tygerberg, South Africa
Barbara Huisamen, PhD