VOLUME 11 NUMBER 3 • SEPTEMBER 2014
115
SA JOURNAL OF DIABETES & VASCULAR DISEASE
REVIEW
The effects of medicinal plants on renal function and
blood pressure in diabetes mellitus
CT MUSABAYANE
Correspondence to: CT Musabayane
Department of Human Physiology, Faculty of Medicine,
University of KwaZulu-Natal, Durban
e-mail:
Previously published in
Cardiovasc J Afr
2012;
23
(8): 462
S Afr J Diabetes Vasc Dis
2014;
11
: 115–120
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 inade-
quate 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 supply-
ing the organs. Microvascular (retinopathy and nephropathy)
and macrovascular (atherosclerotic) disorders are the leading
causes of morbidity and mortality in diabetic patients. There-
fore, emphasis on diabetes care and management is on opti-
mal blood glucose control to avert these adverse outcomes.
Studies have demonstrated that diabetic nephropathy is
associatedwith increased cardiovascularmortality. Ingeneral,
about one in three patients with diabetes develops end-stage
renal disease (ESRD) which proceeds to diabetic nephropathy
(DN), the principal cause of significant morbidity and
mortality in diabetes. Hypertension, a wellestablished 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 associated with reduced renal
function in diabetes mellitus. On the other hand, other plant
extracts may be hazardous in diabetes, 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
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 population uses
resources derived from traditional medicine to control diabetes.
14
Medicinal-plant home remedies are used as crude extracts or
standard, enriched fractions in pharmaceutical preparations.
Research summarised in a recent review
15
showed that several
southern African plant species used by rural communities
as traditional medicines had hypoglycaemic effects in
streptozotocininduced (STZ) diabetic rat. Furthermore, some
species had antihypertensive properties.
16-19
The impact on the
kidney varies, with some species being reno-protective, whereas
others had a deleterious effect on kidney function. By identifying
the bio-active compound, oleanolic acid (OA), which confers reno
