The Effects of Heated Oils Used in Fast Food Restaurants on Metabolic, Inflammatory and Oxidative Stress Markers, Blood Pressure, and Liver Histology in Sprague-Dawley Rats

[Background]Long and repeated heating causes multiple physical and chemical changes in oil, which may result in serious biological damages upon consumption.[Objectives]This study investigated the effects of heated oils used in fast food restaurants on metabolic, inflammatory, and oxidative stress markers in rats.[Methods]The experimental clinical study was performed during summer 2016 in Shiraz, Iran. For 13 weeks, 32 Sprague-Dawley rats received one of the four diets: Group 1: basal diet mixed with 15% w/w heated oil containing total polar compounds (TPC) = 12.5% (TPC 12.5); Group 2: basal diet with 15% unheated oil used in group 1 (control TPC 12.5); Group 3: basal diet with 15% heated oil with TPC = 35% (TPC 35); and Group 4: basal diet with 15% unheated oil used in group 3 (control TPC 35). At weeks six and 13, blood samples were collected for determination of fasting glucose, lipid profile, liver enzymes, and inflammatory and oxidative stress markers. Blood pressure was measured on the 13th week. Histopathological examination of liver slices was performed after euthanization of rats. Statistical analysis was done using the SPSS software.[Results]On the 13th week, the TPC 35 group had higher plasma glucose (+40.4 mg/dL, P < 0.05), triglycerides (+13.6 mg/dL, P < 0.05), aspartate transaminase (+34.3 U/L, P < 0.05), interleukin-1β (+453 pg/L, P < 0.01), and blood pressure (+16/5 mmHg, P < 0.05) than the control and higher glucose (+59.3 ng/L, P < 0.001), aspartate transaminase (+55.5 U/L, P < 0.05), total cholesterol (+6.5 mg/dL, P < 0.05), and 8-isoprostane (+8.5 mg/dL, P < 0.05) than the values on week six. On the 6th week, Low Density Lipoprotein (LDL)-cholesterol was higher in the TPC 35 group than TPC 12.5 (+4.0 mg/dl, P < 0.05) and the level of serum malondialdehyde was higher in the TPC 35 than the control (+0.49 μmol/L, P < 0.001). On the 13th week, more histological changes were observed in rats of the heated oil groups.[Conclusions]Long-term consumption of fried foods from fast food restaurants may have detrimental impact on blood pressure, serum glucose and lipids, inflammatory and oxidative stress markers, and liver histology.