[Changes in lipid metabolism of Wistar rats by changing a high fat to a low fat diet and vice versa]

Wistar rats, 24 weeks of age, with alimentary obesity after fat feeding (50% fat in the diet) for 19 weeks were restricted to fat (3% fat in the diet) for 4 weeks in order to compare the alterations of body and organ weights as well as those of lipid concentrations in epididymal adipose tissue, liver and serum with earlier results [1], obtained before food changing. On these conditions decreases of body weight by about 20%, of the relative mass of epididymal adipose tissue and of the triglyceride content per fat cell were observed. In liver a decline of triglycerides and cholesterylesters (by about 2/3 and 1/3, respectively) and in serum a drop of free fatty acids, but increases of phospholipids, and of free and esterified cholesterol were found. In another series, animals of the same age that had been fed the low fat diet for 19 weeks were administered the high fat diet for 4 weeks and also compared with the state before. Thereby the body weight (by about 20%) and the relative mass of the epididymal adipose tissue gained, but lipid concentrations in this tissue were not affected. In liver the concentrations of triglycerides and cholesteryl esters increased threefold and tenfold, respectively; in serum augmented contents of triglycerides and phospholipids were observed. Besides the changes in adipose tissue, reasons for the forced accumulation of cholesteryl esters in the liver during fat feeding and their retarded removal out of the liver after fat restriction are especially discussed in comparison with that of the triglycerides.