تأثير بعض المركبات العطرية الطبيعية في مسارات الضغط التأكسدي في الجرﺬ

Effect of Some Natural Aroma Compounds on Oxidative Stress Pathways in the Rat"

                                "Humans have been exposed to oxidative stress for many years. The stress may be internal and chemically-induced, or may be external and physically induced like γ-irradiation exposure, both of which are accompanied by harmful effects on the body systems.  Free radicals are known to be derived either from normal essential metabolic processes in the body, or from external sources such as exposure to radiation, air pollutants and industrial chemicals. Streptozotocin (STZ) is a specific diabetogenic agent used to induce diabetes mellitus in animal models through the production of toxic radicals in pancreatic ß-cells.

The use of alternative and traditional medical systems is increasing throughout the world, and as a consequence many traditional medicines have come under renewed scrutiny, and are being investigated for both efficacy and safety. Many plant-derived substances, collectively termed “phytonutrients”, or “phytochemicals”, are becoming increasingly known for their antioxidant free-radical-scavenging activity. In the present study, turmeric and ginger were used.

Curcumin is the active principle of Curcuma longa (turmeric), which is a perennial herb, and is a member of the Zingiberaceae (ginger) family. The rhizome is the portion of the plant used extensively in traditional Indian medicine in particular. Ginger (Zingiber Officinale Roscoe) is one of the world’s best known spices, and has been universally used throughout history for its health benefits. Ginger is also a member of the Zingiberaceae  family and the part used is the dried rhizome.

The aim of this study was to evaluate the oxidative damage that occurs as a result of exposure to an external (γ-radiation) or an internal stressor (STZ); and to examine the antioxidant defense status in STZ-diabetic or γ-rays- exposed rats pretreated with either curcumin or ginger oil, to clarify their possible protective role against the produced stress.

 A total of 200 male adult albino Wistar rats, weighing about 150-170 g, were used as the experimental animals in the present investigation. Rats were divided into 9 groups as follows:

Group 1: Normal Control rats.

Group 2: Curcumin-treated rats.

Group 3: Ginger oil-treated rats.

Group 4: STZ-diabetic rats.

Group 5: Curcumin + STZ rats.

Group 6: Ginger oil + STZ rats.

Group 7: Irradiated Rats.

Group 8: Curcumin + Irradiated rats.

Group 9: Ginger oil + Irradiated rats.

Group 1 served as normal control rats. Groups 2 and 3 were treated by oral intubation with curcumin (50 mg/kg b.wt.) or ginger oil (33 mg/kg b.wt.) respectively, for 10 successive days. In groups 4, 5, and 6, rats were injected intraperitoneally with STZ (45 mg/kg b.wt.) to induce diabetes on the 10th day of aroma compound’s oral administration. Rats in groups 7, 8 and 9, were exposed to a single dose of γ-irradiation (6 Gy) on the 10th day of aroma compound’s oral administration. In groups 5, 6, 8 and 9, rats were treated with curcumin or ginger oil like groups 2 and 3 for a similar period of time. On the 10th and the 20th days after STZ injection or γ-rays exposure, rats were sacrificed, blood samples collected and plasma prepared.. The body weight, the levels of plasma glucose, lipid peroxidation, triglycerides, total cholesterol, LDL-cholesterol and HDL-cholesterol; also, GSH and the enzymatic defense system (blood GSH-PX, SOD, CAT, G6PD and plasma GSSG-R) were assayed.

The present results showed that, compared to normal controls, STZ-treated rats, and those exposed to γ-radiation, exhibited a continued reduction in body weight, significant hyperglycemia (P<0.001), (with a 295.9% increase in the diabetic versus 73% in the irradiated group), hypertriglyceridemia and hypercholesterolemia. LDL-Ch increased 287.7% and 115.5% in the diabetic and irradiated groups respectively, while HDL-Ch decreased in both groups, but was significant only in the former. Plasma MDA concentration was also highly elevated in the diabetic (P<0.001) as well as the irradiated groups (P<0.01), while blood GSH concentration was reduced, only significantly in the diabetic group; also blood GSH-PX activity in the diabetic group was significantly reduced (P<0.001) 10 and 20 days post STZ, while it showed a slight decrease, followed by a significant (P<0.01) increase, on those days in the irradiated group compared to normal controls. Blood SOD and CAT activities increased significantly (P<0.001) in both groups, also plasma GSSG-R activity was elevated but more significantly towards the end of the experiment, G6PD activity was also significantly elevated in the diabetic (P<0.001) and irradiated (P<0.01) groups compared to normal controls.

On the other hand, the pretreatment of rats with either curcumin or ginger oil, caused insignificant increases in body weight at the end of the experiment compared to the diabetic or irradiated controls. Both of the aroma compounds reduced the hyperglycemia observed in the nontreated groups (P<0.001), reduced the triglycerides, total cholesterol and LDL-cholesterol, compared to the diabetic or irradiated groups, while they caused nonsignificant increases in HDL-cholesterol of diabetic and irradiated groups. Curcumin or ginger oil pretreatment caused significant reductions in LPO, elevation of blood GSH concentration and GSH-PX activity, compared to the diabetic or irradiated groups. At the end of the experiment, curcumin and ginger oil also reduced the activity of SOD and CAT, curcumin being more effective. Pretreatment also caused slight/or significant changes (P<0.05) in the activity of GSSG-R and G6PD respectively, compared to the diabetic and irradiated controls. Ginger oil was more effective in reducing G6PD the irradiated group compared to its control. Thus, both curcumin and ginger oil, were shown to have hypoglycemic, radioprotective and antioxidant effects. They enhanced the antioxidant defense systems against reactive oxygen species produced under hyperglycemia or irradiation exposure conditions.

In general, the present study revealed that the hyperglycemia, hyperlipidemia, hypercholesterolemia, increased lipid peroxidation and disturbances in the antioxidant defense status, in the STZ-diabetic as well as in the irradiated rats, were substantially improved by the pretreatment with either curcumin or ginger oil, thus recommending their daily use in the diet."