Investigation of effects of thymoquinone on plasma leptin, carnitine, paraoxonase, thyroid hormones, insulin and glucose with lipid profile in rats fed a fatty diet

The purpose of this study was to investigate the effects of Thymoquinone (TQ) on hormone levels which regulates energy metabolism, and lipid profile in fatty diets. Thymoquinone isolated as the principal active ingredient from the volatile oil of Nigella Sativa (NS), has the beneficial effects such as antioxidant, anticancerogenic, antihyperlipidemic, antidiabetic, antiinflamatuar, gastroprotective, hepatoprotective. The study was performed by four experimental groups for 6 weeks using Wistar Albino rats weighting 200-260g, 5-6 months of age and 10 rats for each group: The groups were as follows; 1) Control Group: Rats were fed with basal diet and given 1 ml %0.9 serum physiologic (SF)/kg body weight/day by gastric gavage. 2) TQ Group: Rats were fed with basal diet and given 50 mg TQ/kg body weight/day dissolved in 1 ml %0.9 SF, by gastric gavage. 3) Fatty diet (FD) group: Rats were fed with experimental diet contained %50 animal fat and given 1 ml %0.9 SF/kg body-weight/day by gastric gavage. 4) FD+TQ group: Rats were fed with experimental diet contained %50 animal fat and given 50 mg TQ/kg body weight/day dissolved in 1 ml %0.9 SF, by gastric gavage.When compared with the Control group, at the end of the 6th week, the body weight decreased in the both TQ and FD+TQ groups while it increased in the FD group. Plasma leptin level decreased in the TQ group, whereas it significantly increased in the FD group comparing with the Control group. In addition, it significantly decreased in the FD+TQ group comparing with FD group (p<0,001). While plasma insulin level decreased in the TQ group (p<0,05), there was no difference for plasma insulin levels between the other experimental groups. Comparing to the Control group, serum glucose levels showed a statistically significant increase in all groups (p<0,001). Comparing with Control group, FT4 significantly decreased in the TQ group but the other thyroid hormones were insignificantly. All thyroid hormones significantly increased in the FD group. Comparing with FD group, TT3 (p<0,001) and FT4 (p<0,01) significantly decreased in the FD+TQ group. While serum paraoxonase decreased in the FD group, it increased in the both TQ and FD+TQ groups. Carnitine levels increased in the TQ group and significantly lowered in the FD group in comparison with Control group, and they were slightly increased by TQ treatment to fatty diet in the FD+TQ group comparing with FD group. Comparing with Control group, HDL and LDL levels were significantly lowered in the TQ group, while the other lipid parameters were slightly decreased. In the FD group comparison with Control group; TG, LDL and VLDL levels significantly increased, HDL significantly decreased and TC slightly increased. In addition, TG, LDL and VLDL levels significantly decreased in the FD+TQ group comparing to the FD group while HDL slightly increased and TC decreased.In conclusion, the TQ treatment decreased the body weight, plasma leptin, TG, LDL and VLDL levels. This results reveal that TQ alleviates the different metabolic disorders caused by dietary fat and may be useful in the field of preventive medicine.