The Effect of Melissa officinalis Extract on Streptozotocin-Induced Diabetes in Rats: A Stereological Study on Pancreatic Islets and Beta-cells

Background & Objective: Melissa officinalis (MO) was shown to possess antioxidant and anti-inflammatory properties and is traditionally believed to have antihyperglycemic effects. This study aims to evaluate the protective effects of MO on streptozotocin (STZ) induced pancreatic damage and thereupon diabetes in rats. Materials & Methods: To induce diabetes mellitus (DM) in rats, STZ (60 mg/kg) was injected intraperitoneally. Forty eight rats were randomly divided into four groups: control 1 (C1) consisted of healthy rats, control 2 (C2) consisted of non-treated diabetic rats, and treatment groups 1 and 2 (T1, T2) were the diabetics orally treated with 150 and 300 mg/kg MO for 14 days, respectively. After euthanizing the animals, their pancreases were extracted and sent for stereological evaluations. Volume density (Vv; %), the absolute volume of the islets (mm3), numerical density of beta cells (Nv; per mm3), and their total number (×106), were measured. P-value<0.05 was considered as statistically significant. Results: The treatment groups showed significant improvements in volume density and total volume of the islets as well as the numerical density and the total number of the beta cells (P<0.001). The treatment groups also had significantly lower blood sugar compared to the untreated group (P=0.008). Conclusion: According to our results, MO has shown promising effects on the pancreatic beta cells against toxic chemicals such as STZ. However, further studies are needed to examine the beneficial effects and possible adverse effects of MO in laboratory models and also in humans.