Effects of Thymoquinone on Plasma Leptin, Insulin, Thyroid Hormones and Lipid Profile in Rats Fed A Fatty Diet

The purpose of this study was to investigate the effects of thymoquinone (TQ) on plasma hormone levels, which regulate energy metabolism, and on the lipid profile of rats fed a standard and fatty diets. The study was performed on four experimental groups for 6 weeks using Wistar Albino rats weighing 200-260 g, aged 5-6 months, with 10 rats in each group. 1) The control group: Rats were fed a standard diet and given 1 ml 0.9% saline /kg body weight/day by gastric gavage. 2) The TQ group: Rats were fed a standard diet and given 50 mg TQ/kg body weight/day dissolved in 1 ml 0.9% saline, by gastric gavage. 3) The fatty diet (FD) group: Rats were fed an experimental diet containing 50% animal fat and given 1 ml 0.9% saline/kg body weight/day by gastric gavage. 4) The FD+TQ group: Rats were fed an experimental diet containing 50% animal fat and given 50 mg TQ/kg body weight/day dissolved in 1 ml 0.9% saline by gastric gavage. At the end of the experimental period, plasma insulin, thyroxine (T-4), high-density lipoprotein (HDL) and low-density lipoprotein (LDL) levels were significantly decreased in the TQ group compared with the control group while the plasma glucose level was increased (P<0.01). In the FD group compared to the control group, HDL and carnitine levels were significantly decreased while plasma leptin, glucose, total triiodothyronine (T-3), T-4, free triiodothyronine (FT3), free thyroxine (FT4), trigliseride (TG), LDL and very low-density lipoprotein (VLDL) levels were significantly increased. Compared to the FD group, in particular, leptin, T-3, FT4, TG, LDL and VLDL levels were significantly decreased in the FD+TQ group except for increased glucose. The study concludes that TQ may be a natural source for the provention of the harmful effects of a fatty diet, due to the dropped levels of leptin, TG, LDL, VLDL and could be considered for use in the field of preventive medicine.