Protective effect of thymoquinone against high-fructose diet-induced metabolic syndrome in rats

Thymoquinone (TQ), a bioactive constituent of Nigella sativa (Linn.) seed, which is commonly used as a spice in Asian food, has been reported to possess a wide range of biological effects. The present study evaluated the effect of TQ on high-fructose diet (HFD)-induced metabolic syndrome (MetS) in male Wistar rats. MetS was induced by 60 % HFD over 42 days. TQ (25, 50 and 100 mg/kg, p.o. once daily) was administered along with HFD for 42 days. Pioglitazone (10 mg/kg, p.o. once daily) was used as a standard drug. Plasma glucose, triglycerides, total cholesterol and HDL-cholesterol were estimated on days 0 and 42. Change in blood pressure, oral glucose tolerance and insulin resistance were measured. Hepatic thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), superoxide dismutase (SOD) and catalase levels were estimated as measures of hepatic oxidative stress. Hepatic mRNA of PPAR-alpha and PPAR-gamma was also studied. TQ prevented the characteristic features of HFD-induced MetS, such as hyperglycaemia, hypertriglyceridemia, hypercholesterolaemia and elevated systolic blood pressure. TQ also prevented impaired glucose tolerance and insulin resistance. It also ameliorated HFD-induced increase in hepatic TBARS and depletion of SOD, catalase and GSH. TQ prevented reduction in hepatic mRNA of PPAR-alpha and PPAR-gamma in HFD rats, and the effects were comparable to those of pioglitazone. This study demonstrates protective effect of TQ against HFD-induced MetS on rats which might have been mediated via PPAR mechanism.