1. Introduction

iabetes mellitus (DM) is considered as one of the most important clinical risk factors involved in some disorders like nephropathy, retinopathy, neuropathy, and cardiovascular diseases, which its prevalence is predicted to be increased daily (1). DM prevalence in Iran is about 5-6%, and at the present, about 4 million Iranians are living with DM or prone to become diabetic (2). Although the most common treatment is insulin and drugs with hypoglycemic effects, but their side effects such as increasing body fat storages, body wasting at the injection site, and hypoglycemic shock are worth to mention; however, these drugs do not have many impact on long term debilitating morbidities. Regarding our daily increasing knowledge about the disease, it is really needed to seek for new medications with fewer side effects (3). Herbal medication usage is of great importance in traditional medicine and such plants have been used for the treatment of many diseases for a long time, whereas there are not still enough scientific evidences about the

effects of most of them (4). From the plants used for diabetes, olive (Olea europia) is of great importance.

Olive is a shrub from oleace species with permanent green leaves, which grows wild with about 5m or more height. Used parts of the tree include the fruit and leaves. This plant has been mentioned in traditional medicine as having the following effects; antihypertensive, anti-atherosclerotic, laxative, giving strength, effective on urinary tracts infection, headache treatment, and antioxidant (5). Also, there are some reports available about the effects of olive leaves in the treatment of malaria (6).

In this study, rats were treated with olive leaves to investigate its anti-diabetic effects. For this purpose, serum glucose level and lipid profile were measured during the study.

2. Materials and Methods

2.1. Collection, identification and preparation of the plant

Olea europia leaves were collected and identified by Karaj Agriculture Faculty taxonomists. Plant leaves were dried at 25°C under shade, then powdered with mechanical grinder. Olive leaves powder was mixed with rats food at a ratio of 6.25%, and the mixture was used as the food for rats under treatment (7).

2.2. Animals

This investigation was an experimental study, in which 30 adult male Wistar rats (weight range from 200 to 250 g) were used (Razi Institute). Rats were kept at animal room, and water and food were provided ad libitum.

2.3. Methods

In this study, only male Wistar rats with a serum glucose level lower than 250 mg/dl at normal conditions without fasting were used (8). Rats were randomly divided into 4 groups including control, control under treatment, diabetic and diabetic under treatment. Control and diabetic groups used only standard food, while control group under treatment and diabetic group under treatment used standard food in combination with the olive leaves powder. Treatment lasted for six weeks. Streptozocin at a dose of 60 mg/kg (single dose) dissolved in normal saline was used intraperitoneally to induce diabetes in rats (8). Diabetes signs including weight loss, polydipsia, and polyuria appeared after 5-7 days. More assurance was obtained after detecting glucosuria and serum glucose level of more than 250 mg/dl.

Blood samples were taken 3 times from rats, the first and second times were performed using capillary tubes from retroorbital capillary vessels, and the third time was performed from the heart. Samples were kept in microtubes at -70°C to measure glucose, cholesterol, triglyceride, HDL and LDL using available commercial kits (ZistChem Co., Tehran).

2.4. Statistical analysis

Data were expressed as positive and negative mean standard deviation. ANOVA test with repeated measures was used to compare each parameter in each group before and after the treatment. Also, one-way ANOVA and Tukey’s post-test were used to compare groups with each other. In addition, p

3. Results

3.1. Serum glucose level

Serum glucose level significantly increased in diabetic rats as compared to control rats (p

3.2. Serum lipids

Serum triglyceride level was higher in diabetic group (p

Moreover, diabetes caused significant elevation of cholesterol and olive leaves consumption led to a significant decrease of cholesterol level in diabetic group under treatment as compared to those without treatment (p

Figure 1. The effect of long-term oral consumption of olive leaves on serum glucose level of control and diabetic rats. ** p

Figure 2. The effect of long-term oral consumption of olive leaves on serum triglyceride in control and diabetic rats. * P

Figure 3. The effect of long-term oral consumption of olive leaves on serum cholesterol in control and diabetic rats. ** p

Figure 4. The effect of long-term oral consumption of olive leaves on serum HDL cholesterol level in control and diabetic rats. $ p

Figure 5. The effect of long-term oral consumption of olive leaves on the LDL cholesterol level in diabetic and control rats. * p