Vol. 3, Issue 1 (2015)
To investigate the effect of lycopene on thyroid functions activity in streptozotocin-induced diabetic rats. A total of thirty (30) Wistar rats of both sexes weighing between 150-200 g were completely randomized in six groups (1-6) comprising five rats each. Normal control animals in group 1 received 0.5 ml of olive oil used in dissolving lycopene. Animals in group 2-5 which were induced with diabetes by intraperitoneal administration of streptozotocin (60 mg/kg body weight) were respectively administered 0.5 ml olive oil, 10, 20 and 40 mg/kg body weight of lycopene. The diabetic animals in group 6 received glibenclamide (standard antidiabetic drug). Administration of lycopene was done once daily for 28 days. After 28 days of treatment of diabetic animals with the graded doses of lycopene, blood glucose level significantly (P < 0.05) decreased from 364.4 ± 44.50 mg/dL to 108.8 ± 16.74 mg/dL when compared with diabetic untreated group. Serum insulin levels decreased significantly (P < 0.05) in the diabetic untreated animals (DC) to 3.02 ± 0.24 µIU/mL following streptozotocin (STZ) treatment from 12.04 ± 0.93 µIU/mL in normal control (NC) when compared. There was significantly (P>0.05) difference between and within groups in the diabetic lycopene treated groups. However, administration of various all doses of lycopene to diabetic rats did not produce any significant (P > 0.05) increase on serum insulin level 4.02 ± 0.70 mg/dL, 3.96 ± 1.41 mg/dL and 5.06 ± 0.96 mg/dL when compared with diabetic control (DC) group. Treatment of diabetic animals with 2 mg/kg of glibenclamide (standard antidiabetic drug) produced a significantly (P < 0.05) elevated serum insulin level (7.76 ± 0.42 µIU/mL) when compared with the diabetic control group (3.02 ± 0.24 µIU/mL). The level of T3 was significantly (P < 0.05) reduced to (1.00 ± 0.09) in the diabetic untreated animals in comparison with those recorded in rats of normal control group that produced (1.44 ± 0.12) when compared. Following oral administration of lycopene and glibenclamide, the levels of T3 was significantly (P < 0.05) elevated to (1.06 ± 0.08, 1.34 ± 0.09, 1.52 ± 0.12) and (1.36 ± 0.08) in diabetic animals when compared to diabetic control group. However, the highest increase was recorded with the 40 mg/kg of lycopene even better with the standard drug (glibenclamide). The total thyrosine (T4) level was significantly (P < 0.05) lowered in streptozotocin-induced diabetic animals that were not treated to (67.20 ± 1.28) when compared with normal control rats that recorded (71.60 ± 3.14). On treatment with lycopene and glibenclamide there was a significant (P<0.05) increase on T4 level to (77.00 ± 2.07) only with the highest dose (40 mg/kg) of lycopene when compared with diabetic control animals. With no significant changes (P > 0.05) observed with 10 and 20 mg/kg of lycopene when compared with diabetic untreated rats Overall, these findings established the fact that lycopene through its antioxidant effect exhibited antidiabetic activity and thus can be recommended for use in the treatment of diabetes. It may also contribute to protection against thyroid damage and associated hormones.
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