2006 Volume 55 Issue 6 Pages 291-297
Male Wistar rats aged 10 weeks were fed ad libitum a powdered diet (AIN93G; no fat) containing 7 wt% of fresh virgin soybean oil (control) or used frying oil recovered from Japanese food manufacturing companies (recovered oil) for 8 weeks and subjected to anthropometric measurements, hematological analyses, and histological evaluations of liver and kidneys. Mild feeding conditions were chosen to mimic the human situation, and Wistar rats were chosen as a healthy model. All the rats grew well, and no gross symptoms attributable to recovered oil were observed. The experimental group did not show any differences in food intake, body weight gain, and weights of liver, kidney and adipose tissue when compared to the control group. In the serum of the experimental group, a remarkably high level of phospholipids was detected, along with increased glucose, triacylglycerol, and cholesterol levels. Microscopic observations indicated frequent lesions in renal cells and nuclear losses of tubular epithelium in the experimental group. No consistent effects on blood pressure or heart rate were observed. It was suggested that ingestion of the recovered oil altered blood composition and damaged kidneys, resulting in promotion of lifestyle-related diseases.