Hypoglycaemic Effect of Lycopene in Streptozotocin-Induced Diabetic Wistar Rats

Abstract

Aim: The study was designed to investigate the hypoglycaemic potential of lycopene in streptozotocin (STZ)-induced diabetic Wistar rats. Methodology: To achieve this, a total of thirty (30) adult Wistar rats of both sexes were used. The animals were made diabetic by single intraperitoneal injection of freshly prepared (60 mg/kg body weight) of STZ. Diabetes was confirmed by the presence of high blood glucose ≥ 200 after 72 hr. Diabetic animals were divided into six (6) groups (1, 2, 3, 4, 5 and 6) comprising five animals each. Animals in Group 1 (Diabetic control) and Group 2 (Normal control) received 0.5 ml of olive oil, while those in groups 2, 3, 4, 5 and 6 were administered 10, 20, 40 and 2 mg/kg b w of lycopene and glibenclamide respectively orally once daily for a period of four weeks. After the last day of treatments, all animals were sacrificed and blood samples collected and the serum separated for determination of serum insulin concentration. The liver tissue was excised and homogenized in equivalent volumes of phosphate buffer for the determination of hepatic glucokinase enzyme activity. Results: The results obtained showed that lycopene at all doses significantly (P < 0.05) decreased the blood glucose concentration steadily from (431.4±48.84 mg/dL) to (171.1±7.65, 118.4±1.97 and 100.8±6.89 mg/dL) after four weeks of treatment. The Serum insulin level was increased from (3.02±0.24 µIU/mL) to (4.02±0.70, 3.96±1.41 and 5.06±0.96 µIU/mL), but was not significant (P>0.05), when compared with diabetic control animals. The activity of hepatic glucokinase was significantly (P<0.05) increased from (8.78±1.11 ng/mL) to (11.96±0.54, 14.23±0.88 and 15.78±0.27 ng/mL), when compared with diabetic control group. Conclusion: It is therefore, suggested that antidiabetic-activity may be linked to enhanced glucokinase enzyme activity and not due to increased serum insulin level as the elevation was not statistically significant (P > 0.05) when compared with the diabetic control group. It is recommended that, lycopene may be used as a dietary component in controlling sustained hyperglycaemia in diabetes.