CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 8, September 2012
462
AFRICA
Review Article
The effects of medicinal plants on renal function and
blood pressure in diabetes mellitus
CT MUSABAYANE
Abstract
Diabetes mellitus is one of the most common chronic global
diseases affecting children and adolescents in both the devel-
oped and developing nations. The major types of diabetes
mellitus are type 1 and type 2, the former arising from inad-
equate production of insulin due to pancreatic
β
-
cell dysfunc-
tion, and the latter from reduced sensitivity to insulin in the
target tissues and/or inadequate insulin secretion. Sustained
hyperglycaemia is a common result of uncontrolled diabe-
tes and, over time, can damage the heart, eyes, kidneys and
nerves, mainly through deteriorating blood vessels supplying
the organs. Microvascular (retinopathy and nephropathy)
and macrovascular (atherosclerotic) disorders are the lead-
ing causes of morbidity and mortality in diabetic patients.
Therefore, emphasis on diabetes care and management is on
optimal blood glucose control to avert these adverse outcomes.
Studies have demonstrated that diabetic nephropathy
is associated with increased cardiovascular mortality. In
general, about one in three patients with diabetes develops
end-stage renal disease (ESRD) which proceeds to diabet-
ic nephropathy (DN), the principal cause of significant
morbidity and mortality in diabetes. Hypertension, a well-
established major risk factor for cardiovascular disease
contributes to ESRD in diabetes. Clinical evidence suggests
that there is no effective treatment for diabetic nephropathy
and prevention of the progression of diabetic nephropathy.
However, biomedical evidence indicates that some plant
extracts have beneficial effects on certain processes associ-
ated with reduced renal function in diabetes mellitus. On the
other hand, other plant extracts may be hazardous in diabe-
tes, as reports indicate impairment of renal function. This
article outlines therapeutic and pharmacological evidence
supporting the potential of some medicinal plants to control
or compensate for diabetes-associated complications, with
particular emphasis on kidney function and hypertension.
Keywords:
diabetes mellitus, diabetic nephropathy, medicinal
plants, hypertension
Submitted 11/12/11, accepted 6/3/12
Cardiovasc J Afr
2012;
23
: 462–468
DOI: 10.5830/CVJA-2012-025
Diabetes mellitus is a global disease affecting both the developed
and developing nations. Epidemiological data suggest that at
least one in 20 deaths are attributable to diabetes and related
complications, a proportion which increases to at least one
in 10 deaths in adults aged 35 to 64 years.
1
The figure is
considered to be an underestimate since most individuals die
from cardiovascular and renal-related complications.
2
World
Health Organisation data show that the age-standardised death
rate for diabetics in South Africa is 85 per 100 000. Death rates
in other sub-Saharan African countries range from 21 to 49 per
100 000,
compared with 18 in the USA and six per 100 000 in
the UK.
3
The principal causes of mortality in type 1 and 2 diabetes
patients are disorders grouped as microvascular (retinopathy
and nephropathy) and macrovascular (atherosclerotic)
complications.
4,5
Macrovascular diseases account for the majority
of deaths in type 2 diabetes patients, and the presence of
hypertension is associated with a four- to five-fold increase in
mortality.
6
A causal relationship between chronic hyperglycaemia
and diabetic microvascular disease, long inferred from various
animal and clinical studies,
7
has now been established by data
from the Diabetes Control and Complications Trial (DCCT)
controlled clinical study.
8
Conventional diabetes therapy using blood glucose-lowering
agents such as sulphonylureas, insulin therapy,
α
-
glucosidase
inhibitors, peroxisome proliferator gamma (PPAR-
γ
)
agonists
and biguanides has limitations. For instance, insulin therapy does
not achieve glycaemic control in patients with insulin resistance,
and oral hypoglycaemic agents may lose their efficacy after
prolonged use. Previous studies elsewhere suggest that insulin
is not only ineffective in preventing type 1 diabetes in patients
at risk of developing this condition, but it can also cause
cardiovascular disease.
9,10
Furthermore, conventional drugs are
not easily accessible to the general population in developing
countries due to socio-economic conditions.
11,12
Hence there is
an urgent need to find affordable treatments that are effective in
slowing the progression of diabetic complications.
Traditional herbal medicine is used by many rural African
communities to treat a range of diseases, including diabetes.
Anecdotal evidence suggests that diabetic complications are less
common in rural populations, attributable to either the beneficial
effect of plant medicines or to the fact that other risk factors
that aggravate diabetes in the urban context are less prevalent
in rural situations. The World Health Organisation not only
encourages the use of plant medicines, but also recommended
scientific evaluation of the hypoglycaemic properties of plant
extracts.
13
Estimates indicate that more than 70% of the world’s
Department of Human Physiology, Faculty of Medicine,
University of KwaZulu-Natal, Durban, South Africa
CT MUSABAYANE, BSc (Hons), PhD (human physiol),
