Beneficial effects of Aloe vera in treatment of diabetes: Comparative in vivo and in vitro studies

Abstract

In the present investigation, the antidiabetic effect of Aloe vera leaf pulp extract was studied in vivo and in vitro as compared to glimiperide. Diabetes was induced experimentally in adult male albino rats by single-dose intraperitoneal injection of streptozotocin (50 mg/kg body weight). The in vitro study was performed using isolated islets of pancreas from adult female albino rats. Both aloe extract (10 ml/kg, p.o.) and glimiperide (10 mg/kg, p.o.) significantly decreased serum glucose and significantly increased serum insulin levels as compared to control diabetic rats. Serum levels of malondialdehyde (MDA) and superoxide dismutase (SOD) were significantly decreased while blood glutathione (GSH) was significantly increased by aloe treatment as compared to diabetic rats. Effect of aloe was better than the effect of glimiperide. Regarding the in vitro study, both aloe (10 μl/l) and glimiperide (10 μmol/l) significantly increased both basal and stimulated insulin secretion from the isolated islets of pancreas as compared to control. These results show a promising antidiabetic effect of aloe for further clinical trials regarding clinical use of aloe extract for treating type II diabetes.

Full text

ORIGINAL ARTICLE
Beneficial effects of Aloe vera in treatment of
diabetes: Comparative in vivo and in vitro studies
Amira Mourad Hussein Abo-Youssef
*
, Basim Anwar Shehata Messiha
Department of Pharmacology and Toxicology, Faculty of Pharmacy, Beni-Sueif University, Egypt
Received 4 December 2011; accepted 31 March 2012
Available online 10 January 2013
KEYWORDS
Aloe;
Diabetes;
Glimiperide;
Rats
Abstract In the present investigation, the antidiabetic effect of Aloe vera leaf pulp extract was stud-
ied in vivo and in vitro as compared to glimiperide. Diabetes was induced experimentally in adult male
albino rats by single-dose intraperitoneal injection of streptozotocin (50 mg/kg body weight). The
in vitro study was performed using isolated islets of pancreas from adult female albino rats.
Both aloe extract (10 ml/kg, p.o.) and glimiperide (10 mg/kg, p.o.) significantly decreased serum glu-
cose and significantly increased serum insulin levels as compared to control diabetic rats. Serum levels
of malondialdehyde (MDA) and superoxide dismutase (SOD) were significantly decreased while
blood glutathione (GSH) was significantly increased by aloe treatment as compared to diabetic rats.
Effect of aloe was better than the effect of glimiperide. Regarding the in vitro study, both aloe (10 ll/l)
and glimiperide (10 lmol/l) significantly increased both basal and stimulated insulin secretion from
the isolated islets of pancreas as compared to control. These results show a promising antidiabetic
effect of aloe for further clinical trials regarding clinical use of aloe extract for treating type II diabe-
tes.
ª 2012 Faculty of Pharmacy, Cairo University. Production and hosting by Elsevier B.V. All rights
reserved.
1. Introduction
Diabetes mellitus is a serious chronic metabolic disorder char-
acterized by a decrease or cessation of insulin secretion in re-
sponse to normal physiological stimuli, or reduced
responsiveness of peripheral tissues to insulin.
1
The metabolic
abnormalities of diabetes cause mitochondrial superoxide
overproduction in endothelial cells of both large and small ves-
sels, as well as in the myocardium. Therefore, oxidative stress
plays a major role in the development of diabetes complica-
tions, both microvascular and cardiovascular complications.
2,3
Many authors claimed for antidiabetic and antioxidant po-
tential of aloe in experimentally-induced diabetes.
4,5
The glu-
cose lowering effects of Aloe vera were suggested to be
mediated, at least partially, through its potent anti-oxidant ef-
fect.
6,7
Recent approaches suggest that treatment of diabetes
should not only focus on insulin secretion but also on antiox-
idant protection of the b-cell. This may facilitate the repair of
b-cells undergoing damage by oxidative stress secondary to
hyperglycemia.
8
*
Corresponding author. Address: 14 Bashar Ibn Bord St.Nasr City,
Cairo, Egypt. Tel.: +20 022748371, mobile: +0122 24 24 884.
E-mail address: dramira73@hotmail.com (A.M.H. Abo-Youssef).
Peer review under responsibility of Faculty of Pharmacy, Cairo
University
Production and hosting by Elsevier
Bulletin of Faculty of Pharmacy, Cairo University (2013) 51, 7–11
Cairo University
Bulletin of Faculty of Pharmacy, Cairo University
www.elsevier.com/locate/bfopcu
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1110-0931 ª 2012 Faculty of Pharmacy, Cairo University. Production and hosting by Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.bfopcu.2012.03.002

Based on these facts, this research is designed to correlate
antioxidant and antidiabetic effects of aloe in experimentally-
induced diabetes in vivo. The results will also be supported
by an in vitro study on isolated pancreatic islets.
2. Materials and Methods
2.1. Animals
Adult male albino rats of Wistar strain weighing about 200–
250 g were used for the in vivo experiments. Adult female albino
rats of Wistar strain weighing 150–200 g were used for the
in vitro experiments. Animals were obtained from the National
Research Center, Cairo, Egypt. The animals were housed in
plastic cages (28 cm · 43 cm · 18 cm) and were maintained un-
der conventional laboratory conditions throughout the study.
They were fed standard pellet chow (El-Nasr Chemical Co.,
Cairo, Egypt) and were allowed water ad libitum. Animals de-
scribed as fasted had been deprived of food for 18 h but had been
allowed free access to water. This design is accepted by the ethics
committee in the Faculty of Pharmacy Beni Sueif University.
2.2. Preparation of A. vera leaf pulp extract
A. vera leaves, over 3 years old, were washed, weighed, peeled
and the leaf pulp (gel together with latex) was scratched with a
spoon.
5
The pulp was homogenized with a homogenizer (Ul-
tra-Turrax T25, IKA Labortechnik, Germany), mixed with
an equal volume of phosphate buffered saline (0.1 M,
pH = 7), homogenized again, kept at 4 C overnight then fil-
tered through cloth. The clear filtrate was kept at 20 Cin
small portions until use. The yield of fresh aloe pulp was about
35% v/w in terms of starting fresh leaf weight.
2.3. Induction of experimental diabetes
After fasting for 18 h, diabetes was induced by intraperitoneal
injection of streptozotocin (Sigma, St. Louis, MO, USA) dis-
solved in 0.1 M cold sodium citrate buffer, pH 4.5, at a dose
of 50 mg/kg.
9
The control rats received the vehicle alone.
The animals were allowed to drink 5% glucose solution over-
night to overcome the drug induced hypoglycemia. After 96 h
of streptozotocin injection, rats with moderate diabetes having
glycosuria and hyperglycemia (blood glucose range of above
250 mg/dl) were considered as diabetic rats and used for the
experiment.
2.4. Isolation of rat pancreatic islets
Pancreatic islets from adult female albino rats
10
were isolated
according to the collagenase digestion technique.
11
Batches
of five islets were picked up using stereomicroscope and trans-
ferred into small tubes each containing 1 ml KRH buffer sup-
plemented with 0.5% bovine serum albumin and glucose either
3 mmol/l (basal concentration) or 16.7 mmol/l (stimulatory
concentration) and the test agent under study was added.
The tubes were covered and incubated at 37 C in a shaking
water bath for 1 h with intermittent hand shaking every
15 min. At the end of incubation period the tubes were trans-
ferred into ice bath and mixed with vortex mixer and then ali-
quots of 0.5 ml were for insulin determination.
2.5. Experimental design in vivo
The rats were divided into four groups, each of six animals, as
follows:
Group I: Normal control rats.
Group II: STZ-induced diabetic control rats.
Group III: Diabetic rats given glimiperide (10 mg/kg) in
aqueous solution daily using an intragastric tube for 14 days.
Group IV: Diabetic rats given A. vera (10 ml/kg) daily
using an intragastric tube for 14 days.
After 14 days of the treatment, Blood samples were col-
lected from the retro – orbital venous plexus following the
technique described by Coccheto and Bjornsson (1983).
12
Briefly, rats were subjected to light ether anesthesia then blood
was collected using heparinized microhematocrit capillary
tubes into Wassermann tubes. Serum was separated by centri-
fugation at 3000 rpm for 10–15 min for the determination of
serum glucose, insulin, SOD and MDA levels. For the assess-
ment of blood GSH level blood samples were hemolyzed by
the addition of cold distilled water.
2.6. Experimental in vitro
Using isolated rat pancreatic islets, two main groups of exper-
iments were performed to study the effects of A. vera (20 lg/
ml) and glimiperide (10 lmol/l) on basal (3 mmol/l glucose)
and stimulated- insulin secretion (16.7 mmol/l glucose).
2.7. Determination of serum glucose and insulin
Fasting serum glucose was estimated by glucose oxidase meth-
od.
13
Insulin in samples, either from in vitro or in vivo experi-
ments was estimated using Enzyme Linked Immunosorbent
Assay (ELISA).
14
2.8. Determination of serum malondialdehyde (MDA),
superoxide dismutase (SOD) and glutathione (GSH)
Serum MDA was estimated by the method of Mihara and
Uchiyama (1978).
15
SOD activity was measured based on the
ability of the enzyme to inhibit the autoxidation process of
pyrogallol method of Marklund and Marklund (1974).
16
Glu-
tathione was estimated by the method of Beutler et al. (1963).
17
2.9. Statistical analysis
Data were expressed as the mean ± standard error of the mean
(s.e.m); and comparison between the different treatments was car-
ried out using one way ANOVA followed by Tukey–Kramer mul-
tiple comparisons test. Significance was accepted at p < 0.05.
3. Results
3.1. Effect of two weeks daily dose administration of A. vera and
glimiperide on serum glucose and insulin levels of streptozotocin-
induced diabetic male rats
Table 1 shows the level of serum glucose and serum insulin in
normal and STZ induced diabetic rats. There was a significant
8 A.M.H. Abo-Youssef, B.A.S. Messiha

elevation in serum glucose level and significant decrease in ser-
um insulin level during diabetes when compared with corre-
sponding control group.
Administration of A. vera and glimiperide tended to bring
the values of serum glucose and insulin levels to near normal.
3.2. Effect of two weeks daily dose administration of A. vera and
glimiperide on serum MDA, blood GSH and blood SOD levels of
streptozotocin-induced diabetic male rats
Results are graphically illustrated in Figs. 1–3. There was a sig-
nificant increase in serum MDA and significant decrease in
blood GSH and SOD during diabetes as compared to
corresponding control group. Administration of A. vera gel ex-
tract and glimiperide significantly decreased serum MDA level
and significantly elevated blood GSH and SOD levels.
3.3. Effect of A. vera and glimiperide on basal and stimulated-
insulin secretion from isolated pancreatic islets of female rats
Results are graphically illustrated in Figs. 4 and 5. These
graphs show the effect of A. vera and glimiperide on basal
and stimulated- insulin secretion from isolated pancreatic islets
of female rats.
Both A. vera and glimiperide significantly raised both basal
and stimulated- insulin secretion as compared to the normal
control value (3 mmol/l glucose).
Table 1 Effect of two weeks daily dose administration of Aloe vera and glimiperide on serum glucose and insulin levels of
streptozotocin-induced diabetic male rats.
Groups Serum glucose level (mg/dl) Serum insulin level (ng/ml)
Normal control 82.24 ± 5.17 7.05 ± 0.76
Diabetic control 331.88 ± 29.72
*
2.82 ± 0.66
*
Diabetic + A. vera 93.66 ± 26.92
a
6.78 ± 0.98
a
Diabetic + glimiperide 117.43 ± 21.96
a
6.26 ± 0.65
a
Values are given as mean ± s.e.m for groups of six animals each.
Values are statistically significant at p < 0.05.
Diabetic control was compared to normal control rats.
Diabetic + A. vera and diabetic + glimiperide were compared with diabetic control.
*
Significantly different from the normal control.
a
Significantly different from the diabetic control.
Values are given as mean ± s.e.m for groups of six animals each.
Values are statistically significant at p < 0.05.
Diabetic control was compared to normal control rats.
Diabetic + Aloe vera and diabetic + glimiperide were compared with diabetic control.
* significantly different from the normal control.
a significantly different from the diabetic control.
Figure. 1 Effect of two weeks daily dose administration of Aloe
vera and glimiperide on serum MDA level of streptozotocin-
induced diabetic male rats.
Figure. 2 Effect of two weeks daily dose administration of Aloe
vera and glimiperide on blood GSH level of streptozotocin-
induced diabetic male rats.
Beneficial effects of Aloe vera in treatment of diabetes: Comparative in vivo and in vitro studies 9

4. Discussion
Results of the present investigation strongly suggest an antidi-
abetic potential for aloe. In-vivo results show decreased serum
glucose and increased serum insulin levels in aloe-treated rats
compared to diabetic controls (Table 1). In agreement, previ-
ous authors claimed for such antidiabetic effect for aloe extract
on experimental animals.
18,19
Our in vitro results support this
finding, where aloe was found to increase the rate of insulin
secretion from pancreatic islets (Figs. 4 and 5).
Many explanations were suggested for this antidiabetic ef-
fect of aloe. The first explanation is the potent antioxidant ef-
fect of aloe extract. Aloe is long known to have antioxidant
potential via suppression of free radical formation and
enhancement of cellular thiol status.
20–22
It is also reported
to stimulate glutathione-S-transferase enzyme activity.
23
Our
results strongly supported the antioxidant potential of aloe,
where it was found to suppress elevated serum MDA levels
and increase blood GSH and SOD levels. Recent approaches
focus on the role of oxidative stress in pancreatic beta cell
damage.
8,24
That is, oxidative stress is involved as a causative
factor in the pathogenesis of diabetes, and hence antioxidants
like aloe may have a true antidiabetic effect via antioxidant
potential.
The anti-inflammatory potential of aloe may be the second
explanation for its antidiabetic effect. Diabetes may be consid-
ered as an inflammatory disease where inflammation partici-
pates in the progression of diabetes, where tumor necrosis
factor-a was found to decrease peripheral insulin sensitivity.
25
Many authors claimed for the anti-inflammatory potential of
aloe due to many of its components like emodin and man-
nose-6-phosphate.
26,27
It was reported that the anti-inflamma-
tory effect of aloe extract is comparable to that of
hydrocortisone.
28
Finally, aloe may act as a hypoglycemic agent through po-
tent inhibition of pancreatic a-amylase activity.
29
This action
decreases starch breakdown and offers good postprandial gly-
cemic control.
These findings are promising for further clinical studies on
aloe extract or extract components in the management of dia-
betes mellitus.
Figure. 4 Effect of Aloe vera and glimiperide on basal insulin
secretion from isolated pancreatic islets of female rats.
Figure. 3 Effect of two weeks daily dose administration of Aloe
vera and glimiperide on blood SOD level of streptozotocin-
induced diabetic male rats.
Figure. 5 Effect of Aloe vera and glimiperide on stimulated-
insulin secretion from isolated pancreatic islets of female rats.
10 A.M.H. Abo-Youssef, B.A.S. Messiha

5. Conflict of interest
None.
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