International Journal of Drug Development and Research

Key words

Diabetes, Aloevera gel, anti-inflammatory activity, homocysteine, folic acid.

INTRODUCTION:

Diabetes mellitus often simply referred to as diabetes is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced [1]. The symptoms of diabetes are excessive urine production (polyuria), excessive thirst and increased fluid intake (polydypsia), blurred vision, unexplained weight loss and lethargy [2].

Impaired endothelial function is a common feature in type 2 diabetes [3]. Folic acid, a B-vitamin, has potential to enhance endothelial function in several pathological conditions including coronary artery disease, smoking, familial hypercholesterolemia, and type 2 diabetes [4]. Folic acid levels serve as a “biomarker” of endothelial function. Alloxan is widely used to induce diabetes in a wide variety of species by damaging the insulin secreting pancreatic =-cell, resulting in decrease in endogenous insulin release [5], [6]. Glibenclamide often used as a standard drug is a common oral hypoglycemic drug which stimulates insulin secretion from the existing pancreatic cells [7].

Today the medical research is towards herbal or alternate system of medicine. The uses of medicinal plants in the treatment of diabetes mellitus are common practices in wide areas especially in Eastern States where people depend solely on herbal treatment [8]. Aloe vera is a stemless, droughtresisting succulent of the lily family. It is indigenous to hot countries and has been used medicinally for over 5000 years by Egyptian, Indian, Chinese and European cultures. Aloe vera gel is the mucilaginous aqueous extract of the leaf pulp of Aloe vera. It contains over 70 biologically active compounds [9]. Aloe vera extracts are useful in the treatment of wound and burn healing, minor skin infections, sebaceous cyst, diabetes and elevated blood lipids in humans [10]. The present attempt was carried out to evaluate the impact of Aloe vera supplementation on the inflammatory biomarkers, Homocysteine and Folic acid in Alloxan induced diabetic rats.

MATERIALS AND METHODS

Dose preparation:

Aloe vera gel:

Mature fresh leaves of Aloe barbadensis were washed with water. The leaves were cut transversely into pieces. The thick epidermis was selectively removed and fleshy solid gel was cut into small pieces. The gel was refluxed with absolute ethanol and dried in heating mantle. Dried powder was administered with the dosage of 300mg/kg b.wt [11].

Procurement of animals:

The rats were kept as groups separately in individual stainless steel hoppers. The animals were characterized by strain, source, sex, weight and age. The animals were kept individually for feeding in conventional laboratory diets with an unlimited supply of drinking water.

Induction of experimental diabetes:

Alloxan monohydrate was used for induction of diabetes in rats. The solution was made in normal water and administered with the single dose of 150mg/kg body weight, i.m. [12]. Alloxan monohydrate was procured from the National chemicals Pvt. Ltd.

Experimental Design:

The rats were randomly divided into four groups of six animals each.

Group I: Control Rats.

Group II: Alloxan induced diabetic rats.

Group III: Alloxan induced diabetic rats supplemented with Aloe barbadensis (Aloe vera) gel (300mg/kg b.w., oral).

Group IV: Alloxan induced diabetic rats treated with Glibenclamide.

Study protocol

The experiment was carried out for 21 days. At the end of experimental period, rats were sacrificed by cervical decapitation. Blood was collected, centrifuged the plasma separated was used for biochemical estimation. Homocysteine was determined by ELISA method [13]. Folic acid was determined by ELISA method [14]. All the animal experiments were duly approved by the Institutional Animal Ethics Committee (743/03/abc/CPCSEA dt 3.3.03) Guidelines. (IAEC)

The data obtained in present investigation was subjected to statistical analysis. All results are expressed as Mean ± S.D. Student‘t’ test was performed using SPSS soft ware version 12.0.

RESULTS:

The level of plasma homocysteine in the experiment groups is shown in Fig. 1. Alloxan-induced diabetic rats exhibited a significant elevation in the levels of homocystine (15.26%) when compared to normal rats. Alloxan-induced diabetic rats when supplemented with Aloe vera showed a significant decrease in the levels of homocystine (12.16 %) when compared to alloxan-induced diabetic rats. Glibenclamide treated diabetic rats recorded a significant decrease in the levels of homocystine (10.27%) when compared to alloxan-induced diabetic rats.

Fig.2 reveals the levels of folic acid in the experimental groups. The levels of folic acid were found to be decreased (7.36%) significantly in the alloxan induced diabetic group when compared to normal. Alloxan supplemented group and Glibenclamide treated group reported a significant increase in the activity of folic acid (4.25% & 3.32%) in plasma when compared to alloxan induced diabetic group.

DISCUSSION

Diabetes mellitus is a multifunctional disease with several causes and complex consequences. It remains an important risk factor for cardiovascular disease and increasing rate of childhood and adult obesity. Diabetes is likely to become even more prevalent over the coming decade [15]. Alloxan, a beta cytotoxin, induces diabetes in animals by damaging the pancreas, which decreases the utilization of glucose by the tissues [16]. Alloxan is relatively toxic to insulin producing pancreatic beta cells because it preferentially accumulates in beta cells through uptake via the GLUT2 glucose transporter [17].

Homocysteine, an atherogenic amino acid, has emerged as a novel independent marker of risk for the development of cardiovascular disease and diabetes mellitus (DM) over the past three decades. Hyperhomocysteinemia (HHcy) in DM would be expected to share a similar prevalence of declining glomerular filtration rate and diabetic nephropathy. There are multiple metabolic toxicities resulting in an excess of reactive oxygen species associated with DM and the accelerated atherosclerosis (atheroscleropathy). The water-soluble B vitamins (especially folate and cobalamin-vitamin B12) have been shown to lower HHcy.

Hcy is an intermediate metabolic product of methionine metabolism. Once methionine is demethylated, producing Hcy, it can be further catabolized to cystathionine and cysteine via the transsulfuration pathway. This transsulfuration pathway is dependent on the cystathionine beta synthase enzyme (CBS) and vitamin B6. Vascular cells lack the CBS enzyme and therefore the transsulfuration pathway is not present. In the remethylation cycle termed the Methionine – Folate Cycle, folic acid (folate) serves as the methyl donor to convert Hcy to Methionine.

This reaction is dependent on the Methionine Synthase (MS) enzyme and the cofactor vitamin B12. Folate serves not only as a methyl donor but also as hydrogen and an electron donor. This hydrogen and electron donation capability renders folate as a dual source for stabilization of the tetrahydrobiopterin (BH4) cofactor of the endothelial nitric oxide synthase (eNOS) reaction producing the quintessential endothelial nitric oxide (eNO) and the additional function of being a local endothelial microenvironment antioxidant. These findings have led to the hypothesis of a folate shuttle phenomenon suggesting the existence of a relative endogenous endothelial folate deficiency thereby resulting in a toxic effect of Hcy accumulation within endothelial cells as a result of this folate shuttle.

Insulin acutely increases homocysteine transmethylation, transsulfuration and clearance in control rats, thus stimulating homocysteine removal from plasma. But a reverse mechanism is seen in alloxan induced diabetic rats, a remarkable increase in homocysteine was noticed in diabetic control rats due to the observed lack of insulin.

In the present study, there was an increase in the level of homocysteine and decrease in the level of folic acid in alloxan induced diabetic group of rats when compared to normal. Ethanolic extract of Aloe barbadensis gel, significantly decreased the level of homocysteine and the level of folic acid was significantly elevated when compared to diabetic control. The effects of folic acid on endothelial function have been ascribed to its homocysteine lowering effects [18]. Some studies established that homocysteine acutely and chronically impairs endothelial function by inhibiting the synthesis and release of nitric oxide and enhancing the production of superoxide [18], [19]. Increase in the concentration of the folic acid might lower the homocysteine levels, which enhances the endothelial function [20], [21]. The results also correlated with above findings. In conclusion, the Aloe vera gel extract decreased the level of homocysteine and increased the level of Folic acid in diabetic rats.

Figures at a glance

Figure 1 Figure 2

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