ZOBO REDUCES DIABETES-INDUCED KIDNEY DISEASE RISK

The popular zobo drink made from the
calyx (flower part) of roselle (Hibiscus
sabdariffa) has been successfully used in
traditional medicine to treat various
diseases such as cough, hypertension,
stomach disorders, loss of appetite, upper
respiratory congestion, nerve and heart
disorders and menstrual difficulties. But
recent studies suggest that although it
could be used to reduce the risk of kidney
damage in diabetics, high doses could lead
to kidney damage.
CAN drinking high doses of the popular
zobo drink lead to kidney damage? Results
of a recent study suggest that aqueous
extract of Hibiscus sabdariffa (HSE) has no
harmful effect on the liver but when
consumed in high doses could be harmful
to the kidney. “Further research aimed at
identifying the chemical composition and
potential toxic agent(s) in HS is
recommended,” the researchers wrote.
Commonly called zobo or roselle in Nigeria,
Hibiscus sabdariffa belongs to the plant
family malvaceae.
The study titled: “Toxicilogical effects of
aqueous extract of Hibiscus Sabdariffa on
the liver and kidney,” was published in
Journal of College of Medicine.
The aim of the study is to show the effect
of graded doses of aqueous extract of HS
on major excretory organs (liver and
kidney) of albino Wistar rats. This may be
helpful in determining the safety or
otherwise of its consumption at different
concentrations.
The researchers wrote: “There were no
significant changes in the histology of the
liver throughout the period of HS
administration in all the groups. However,
there were significant histological changes
in the kidney, which were more
pronounced at higher doses (80 and
160mg/kg). There was shrinkage of
glomerular tuft, increase in urinary pole,
increase in size of tubular lumen and
tubular damage. These effects were more
marked as the duration of administration of
the extract progressed with greatest effect
observed at 12th week.”
Another study found that Hibiscus
sabdariffa might help treat kidney stones
via uricosuric activity. The study titled:
“Uricosuric effect of Roselle (Hibiscus
sabdariffa) in normal and renal-stone
former subjects,” was published in Journal
of Ethnopharmacology.
Uricosuric agents are used to lower the uric
acid level in the blood and to prevent the
formation of uric acid crystals in the joints
and kidneys. These drugs are often used to
treat gout, a disease in which uric acid
crystals deposit in joints and cause pain. By
decreasing plasma uric acid levels, these
drugs decrease the deposition of crystals in
joints, eventually decreasing inflammation
and thereby reducing the pain of gout.
Researchers from Thailand conducted a
study with nine subjects with no history of
kidney stones and nine with a history of
kidney stones. A cup of tea made from 1.5
grams of dry roselle was provided to
subjects twice daily (morning and evening)
for 15 days.
After taking the tea, both groups showed
increases in oxalate and citrate. In the non-
kidney stone group, increases in uric acid
excretion and clearance were observed. In
the patients with kidney stones, both uric
acid excretion and clearance were
significantly increased.
The study authors concluded that roselle
has a uricosuric effect and they suggested
that the chemical constituents exerting this
effect should be identified.
Also, researchers have shown that aqueous
(water) extracts of HSE is capable of
reducing lipid peroxidation, increasing
catalase and glutathione activities
significantly in diabetic kidney, and
decreasing the plasma levels of triglyceride,
low-density lipoprotein (LDL) and increasing
high-density lipoprotein (HDL) value.
Lipid peroxidation is a well-defined
mechanism of cellular damage in both
animals and plants that occurs in vivo
during aging and in certain disease states.
Catalase is an antioxidant enzyme found in
living organisms that changes hydrogen
peroxide to water and oxygen. Hydrogen
peroxide is formed as a toxic waste product
of metabolism. It must be quickly converted
into other, less dangerous, chemicals. To
manage this problem, the enzyme catalase
is frequently used to rapidly catalyse the
decomposition of hydrogen peroxide into
harmless oxygen and water.
Glutathione is an antioxidant compound
found in living animal and plant tissue.
Glutathione is the major endogenous
antioxidant produced by the cell.
Glutathione participates directly in the
neutralization of free radicals, reactive
oxygen compounds, and maintains
exogenous antioxidants such as vitamins C
and E in their reduced (active) forms. In
addition, through direct conjugation,
glutathione plays a role in the detoxification
of many xenobiotics (foreign compounds)
both organic and inorganic. Glutathione is
an essential component of the human
immune response.
Triglycerides are a type of lipid found in
blood. When food is consumed, calories are
released by the oxidation of food. The
calories, which the body does not exhaust,
are converted into energy resources called
triglycerides which are stored in the fat cells
of the body and are used to supply energy
when required. Under the action of certain
hormones these triglycerides are broken
into simpler, absorbable forms of fatty acids
to liberate energy.
LDL is “bad” cholesterol, while HDL is “good”
cholesterol.
According to the study published in
Evidence-Based Complementary and
Alternative Medicine, HSE, in histological
examination, improves hyperglycemia-
caused osmotic diuresis in renal proximal
convoluted tubules (defined as hydropic
change) in diabetic rats.
Hyperglycemia or Hyperglycæmia, or high
blood sugar, is a condition in which an
excessive amount of glucose circulates in
the blood plasma.
Osmotic diuresis is increased urination
caused by the presence of certain
substances in the small tubes of the
kidneys.
The proximal convoluted tubule is the most
proximal segment of the renal tubular
portion of the nephron. It is responsible for
the reabsorption of glucose, amino acids,
various ions and water.
The study also reveals that up-regulation of
Akt/Bad/14-3-3? and NF-?B-mediated
transcription might be involved.
The researchers concluded: “In conclusion,
our results show that HSE possesses the
potential effects to ameliorate diabetic
nephropathy via improving oxidative
status and regulating Akt/Bad/14-3-3?
signaling.”
The study is titled: “Aqueous extract from
Hibiscus sabdariffa linnaeus ameliorate
diabetic nephropathy via regulating
oxidative status and Akt/Bad/14-3-3? in an
experimental animal model.”
Several studies point out that oxidative
stress maybe a major culprit in diabetic
nephropathy. Diabetic nephropathy is
kidney disease or damage that occurs in
people with diabetes. HSE has been
demonstrated as having beneficial effects
on anti-oxidation and lipid-lowering in
experimental studies.
This study investigated the effects of
Hibiscus sabdariffa L. on diabetic
nephropathy in streptozotocin induced type
1 diabetic rats.
Diabetic mellitus (DM) is a consequence of
chronic metabolic aberrations including
hyperlipidemia. High glucose facilitating the
glycolysis and adenosine triphosphate
generation would cause huge reactive
oxygen species (ROS) production. Under
physiological circumstances, ROS involve
some signaling molecules and follow
defense mechanisms such as phagocytosis,
neutrophil function and shear-stress
induced vasorelaxation.
However, excessive oxidative stress could
damage proteins, lipids, and DNA and
eliminate anti-oxidative enzymes or
molecules. Ujihara et al. observed that
oxidized LDL level was significantly higher
in diabetic patients with macroalbuminuria.
They suggested that oxidized-LDL might
play an important role in diabetic
nephropathy.
Experimentally, the oxidative level of LDL
can be determined by detecting lipid
peroxidation. Antioxidant defense
mechanisms include free radical scavengers
and enzyme systems, such as superoxide
dismutase (SOD), glutathione peroxidase
(GSH) and catalase (CAT). Previous studies
showed that these anti-oxidative molecules
were reduced in diabetes.
In addition to the devastating damage
effect on macromolecules, oxidative stress
can be involved in cellular signal
transduction including Akt signaling
pathway. Akt is a principal mediator of
biological functions of insulin in glucose
metabolism. Phosphorylated Akt can
regulate apoptosis via activating Bad to
associate with 14-3-3? protein and also to
activate nuclear factor-kappa B (NF-?B) to
regulate transcription.
Recent studies showed the importance of
phosphoinositide 3-kinases (PI3-K) and Akt
signaling pathway in diabetic nephropathy
including regulation of renal mesangial
hypertrophy and renal tubular cells
proteolysis. It has been well known that
hyperglycemia and insulin could modulate
Akt activity in diabetic renal tissue.
However, the results are not compatible.
Furthermore, the correlation between
oxidative stress and Akt signaling in
diabetic renal tissues has not been well
clarified.
A wide variety of natural products have
been found to possess capacity to control
metabolic problems and oxidative stress in
diabetes. Hibiscus sabdariffa Linnaeus is
usually used as a beverage. The
constituents in the flowers of Hibiscus
species are polyphenolic acids, flavonoids,
and anthocyanins.
Previous studies found that HSE possessed
anti-oxidative characteristics and had anti-
atherosclerotic effects. Recent
pharmacological studies also showed that
HSE significantly reduced blood pressure in
humans and in experimental animals.