Assessment of Cardiac Oxidative Status of Diabetic
Wistar Rats Exposed to Methanol Fraction of Ethanol
Extract of Dialium Guineense Stem Bark Volume 57- Issue 2
Abu OD1*, Umar AB2, Ekperusi SE3 and Ohikhuare F4
1Department of Biochemistry, Faculty of Life Sciences, University of Benin, Nigeria
2Department of Biochemistry, Faculty of Life Sciences, Ambrose Alli University, Nigeria
3Department of Biomedical Science, Faculty of Science and Engineering, University of Wolverhampton, UK
4Department of Chemistry and Biochemistry, College of Letters and Science, University of Wisconsin, USA
Received: June 20, 2024; Published: June 26, 2024
*Corresponding author: Abu OD, Department of Biochemistry, Faculty of Life Sciences, University of Benin, Nigeria
The present study investigated the cardiac oxidative status of diabetic Wistar rats exposed to methanol
fraction of ethanol extract of Dialium guineense (MEDG) stem bark. Male Wistar albino rats (n = 25, mean
weight = 215 ± 15 g) were randomly assigned to five groups of 5 rats each: normal control, diabetic control,
metformin, MEDG (200 mg/kg body weight, bwt) and MEDG (300 mg/kg bwt) groups. A single intraperitoneal
injection of 50 mg/kg bwt STZ was used to induce diabetes mellitus in the rats. The diabetic rats were treated
for 21 days with either metformin (50 mg/kg bwt) or MEDG stem bark. Activities of antioxidant enzymes
such as catalase, superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR)
as well as molecules like glutathione (GSH), total protein (TP), malondialdehyde (MDA) and nitric oxide (NO)
were measured in heart homogenate (20 %). The results showed that induction of diabetes mellitus with
STZ significantly increased the fasting blood glucose (FBG) concentrations of the rats, while decreasing the
activity/concentration of antioxidant enzymes/molecules (p < 0.05). However, treatment of the diabetic
Wistar albino rats with MEDG stem bark markedly reduced the FBG concentration and body weights of rats
but enhanced the activity/concentration of antioxidant enzymes/molecules in cardiac tissue (p < 0.05). These
results indicate that MEDG has the potential to promote antioxidant defense in the heart of STZ-induced
diabetic rats.
As a meshwork of cardiac muscle cells interconnected by contiguous
cytoplasmic bridges the heart pumps blood through blood vessels
of the circulatory system [1,2]. Chemical-induced cardiac injury constitutes
serious health risk to humans [3-5]. Besides its hepatotoxic
effect STZ can negatively impact the heart [4]. Defined as the toxicity
that affects the heart, cardiotoxicity is of special interest to researchers
in the field of medicine [6]. It continues to top safety concerns
principally because of lack of sufficient knowledge of the underlying
mechanisms [7]. Cardiotoxicity is characterized by abnormality of
cardiac electrical activity and contractile dysfunction, ultimately leading
to heart failure. Cardiovascular adverse effects can lead to cardiac
arrhythmias [8,9]. Oxidative and nitrative stress, and formation
of protein adduct are established mechanisms of chemical-induced
cardiotoxicity. Protein adduct formation causes cardiac muscle cell
inflammation, perturbation of calcium homeostasis, apoptosis (programmed
cell death), cardiomyocyte swelling, nuclear splitting, vacuolization,
and alteration in signalling pathways [10]. Reactive oxygen
species (ROS) produced as a result of oxidative stress cause damage
to cellular structures within vascular wall, thereby triggering several
redox-sensitive transcriptional pathways, shifting the cell towards a
pro-atherogenic transcriptomic profile [11].
Diabetes mellitus is a disease characterized by chronic hyperglycemia
[12-15]. A number of diabetics frequently combine oral antidiabetic
medications with herbal supplements. In Africa, there are more
than 500 plants that are known to have medicinal properties [16]. Dialium
guineense (Velvet Tamarind) is a medicinal plant used in folklore
medicine for the treatment of infections (diarrhea, severe cough,
bronchitis, wound, stomachaches, malaria fever, jaundice, ulcer and
hemorrhoids) [17]. It is a tall, tropical, fruit-bearing tree, belonging
to the Leguminosae family, and has small, typically grape-sized edible
fruits with brown hard inedible shells. In Africa, it grows in dense forests
along the southern edge of the Sahel. The plant grows naturally in
West African countries, Central African Republic, and Sudan [18]. In
Nigeria, it is known by different names: Icheku (Igbo), Awin (Yoruba),
Tsamiyarkurm (Hausa) and Amughen (Bini) [19, 20]. The aim of this
study was to investigate the cardiac oxidative status of diabetic Wistar
rats exposed to MEDG stem bark.
The standard antidiabetic drug, metformin, was purchased from
Micronova Laboratories (India), and STZ was a product of British
Drug House (BDH) Chemicals Ltd. (England). Absolute ethanol, chloroform
and other solvents were obtained from Bell, Sons & Co. (England),
while formaldehyde was purchased from Thermo Fisher Scientific
Ltd. (USA). All the chemicals and solvents used in this study
were of analytical grade.
Collection of Plant Material
The authenticity of the stem barks of D. guineense, which were
obtained from Auchi, Edo State, Nigeria, was verified by Dr. Henry
Akinnibosun of the Department of Plant Biology and Biotechnology,
University of Benin, Benin City, Nigeria. The prepared plant specimen
was deposited in the herbarium of same department (No. UBHD330).
Plant Extraction
The plant’s stem bark was washed and shade-dried for 2 weeks at
room temperature, and thereafter ground into powder using a blender.
A portion (500 g) of powdered plant material was steeped in 5,000
mL of 100 % ethanol. The resulting extract was filtered through muslin
cloth and freeze-dried with a lyophilizer. The ethanol extract was
subsequently fractionated with absolute methanol [21,22].
Animals
Male Wistar albino rats (n = 25, mean weight = 215 ± 15 g) were
bought from the Department of Anatomy, University of Benin, Nigeria
and housed in wooden cages. They were acclimatized for fourteen
days before commencement of the study and had free access to feed
and water.
Experimental Design
The rats were randomly assigned to five groups (5 rats per group):
normal control, diabetic control, metformin, MEDG (200 mg/kg bwt)
and MEDG (300 mg/kg bwt) groups. Diabetes mellitus was induced in
the rats via intraperitoneal injection of STZ at a dose of 50 mg/kg bwt.
The diabetic rats were then treated with either metformin (50 mg/kg
bwt) or the extract, for 21 days.
Tissue Sample Collection and Preparation
At the end of day 21 of treatment, the rats were euthanized under
mild chloroform anaesthesia after an overnight fast. Their hearts
were excised and used to prepare 20 % tissue homogenate. The homogenate
was centrifuged at 2000 rpm for 10 min to obtain clear supernatant.
Biochemical Analyses
The activities of catalase, SOD and GPx were determined [23-25].
cardiac levels of TP, MDA, GSH, and NO were also measured [26-29].
The activity of GR was determined using a previously described method
[30].
Data Analysis
Data are presented as mean ± SEM (n = 5). Statistical analysis
was performed using SPSS version 21. Statistical differences between
means were compared using Duncan multiple range test. Statistical
significance was assumed at p < 0.05.
Effect of MEDG Stem Bark on Weight and Blood Glucose of
Rats
Induction of diabetes mellitus with STZ significantly increased the
blood glucose concentrations of the rats (p < 0.05). However, treatment
of the diabetic rats with MEDG stem bark markedly reduced the FBG
concentration and body weights of rats (p<0.05) (Table 1 and Figure 1).
Data are weight and FBG parameters and are expressed as mean ± SEM
(n = 5).
Figure 1
Table 1: Weight and Blood Glucose Parameters.
Cardiac Oxidative Status of Diabetic Rats
Induction of diabetes mellitus with STZ markedly reduced the activities
of the markers of oxidative stress, % GSH, and % NO in cardiac
tissue (p < 0.05). However, treatment of diabetic Wistar albino rats
with MEDG stem bark significantly increased the activities of antioxidant
enzymes and other parameters measured (p < 0.05; Figures 2-4).
Diabetes mellitus refers to a group of metabolic disorders characterized
by a state of chronic hyperglycemia due to defects in insulin
secretion, insulin action or both [31]. Over time, elevated blood glucose
leads to serious damage to the heart, blood vessels, eyes, kidneys
and nerves. This metabolic disorder is often described as “a silent killer”
since it may be asymptomatic at onset. Therefore, the disease usually
goes undiagnosed until major complications arise. Diabetes mellitus
is associated with reduced life expectancy, significant morbidity
as well as diminished quality of life [32-34]. It has been reported that
10 % of global health expenditure is spent on the disease annually
[35,36]. There is profound reason to suggest that this figure might
increase in the coming years giving the myriads of complications that
result from diabetes mellitus. Oxidative stress has a mediatory role
in the pathogenesis of diabetes mellitus and its related complications
via promotion of free radicals production and impairment of antioxidant
defense systems [36]. This study investigated the cardiac oxidative
status of diabetic Wistar rats exposed to MEDG stem bark. In this
study, albino rats of Wistar strain were used, since they are a wellknown
animal model. The results showed that diabetic rats’ heart
measurements were much worse than those of the normal control,
which suggests that diabetic cardiomyopathy was present.
Also, the loss of aorta’s ability to relax when NO is present shows
that endothelial dysfunction also occurred. Compared to normal control
rats, there were also more signs of oxidative stress, and inflammation.
These symptoms of diabetes mellitus are well-known and
are considered to be some of the main causes of the major complications.
Diabetes mellitus tends to damage cell membrane, thereby
enhancing the production of ROS [12,13]. Studies have demonstrated
that diabetic patients experience increased oxidative and nitrosative
stress, which can negatively affect the heart or arteries. In this study,
induction of diabetes mellitus with STZ markedly reduced the activities
of the markers of oxidative stress, % GSH, and % NO in cardiac
tissue. However, treatment of diabetic Wistar rats with MEDG stem
bark significantly increased the activities of antioxidant enzymes and
other parameters measured. It is likely that in the myocardium STZ
aggravated oxidative stress process by suppressing the expression of
SOD, catalase, and GPx.
These results are consistent with those of previous studies [37-
46]. The results suggest that STZ-induced diabetes mellitus promotes
increased production of ROS, while suppressing the synthesis/activity
of antioxidant enzymes/molecules in myocardial tissue. The MEDG
stem bark may contain compounds that exert anti-hyperglycemic effects
as well as oxidative stress-reducing properties in STZ-induced
diabetic rats. Containing important phytochemicals, the medicinal
plant has been demonstrated to exhibit a number of biological/pharmacological
effects [47-83].
According to the findings of this study, methanol fraction of the
ethanol extract of Dialium guineense stem bark is able to alter the oxidative
status of the hearts of diabetic rats. The findings have given
credence to the use of Dialium guineense in Traditional Medicine for
the treatment of diabetes mellitus. However, additional work is required
to ascertain its mode of action and determine whether or not
it is harmful in the long-term.
Ebhohon SO, Ibeh RC, Ejiofor UE, Abu OD, Osegenna SC (2019) Hepato- and nephro-protective effects of methanol extract of Citrullus lanatus rind in Wistar rats fed with used motor engine oil contaminated feed. FUDMA Journal of Sciences 3(4): 246-250.
Abu OD, Imafidon KE, Obayuwana HO, Okwudiri NB (2017) Hepatotoxic effect of methanol extract of citrullus lanatus seeds in Wistar albino rats. Journal of the Nigerian Society of Experimental Biology 17(4): 159-163.
Abu OD, Onoagbe IO, Ojo I (2021) Graded and quantal dose response of total tannins isolated from the stem bark of Dialium guineense. Advanced Research Journal of Medicine and Clinical Science 08(10): 699-703.