Plasma esterase-1 (ES-1) activity is increased in rats fed high-fat diets

The question addressed is whether the amount and type of dietary fat affects esterases in plasma. Rats were fed semipurified diets containing 2.0 to 19.4% (w/w) of fat in the form of coconut fat or corn oil. Fat was added to the diets at the expense of isocaloric amounts of carbohydrates. Plasma total esterase activities measured with 4-nitrophenylacetate as substrate were slightly increased with increasing fat intakes. However, an increase in fat concentration of the diet was associated with a pronounced increase in the activity of the so-called ES-1 isozyme in plasma. ES-1, which represents very little plasma total esterase activity, was quantified densitometrically as the high-mobility, anodal esterase band on polyacrylamide gel electrophoresis. The positive association between amount of dietary fat and ES-1 activity was identical for coconut fat and corn oil.