Effect of protamine in obesity induced by high-fat diets in rats

Objective: Protamine has been shown to have an inhibitory effect on protein lipase in vitro; the objective of this study was to evaluate the antiobesity activity effect of protamine in obese induced rats, and to evaluate the effect of protamine on postprandial hypertriacylglyceridemia in rats by intragastric administration of a lipid emulsion containing corn oil. Design: Two experiments were carried out: (1) In a parallel study in rats, we administered a lipid emulsion containing corn oil plus 0, 200 or 500 mg kg-1 of protamine intragastrically. (2) In a randomized parallel prospective rats experiment, rats were fed with a high-fat diet and 0, 200 or 500 mg of protamine per kg of animal weight during 5 weeks. Subjects: Male Sprague-Dawley rats. Measurements: In experiment 1, plasma triacylglycerol levels after oral administration of lipid emulsion were determined. In experiment 2, weight gain, concentrations of plasma triacylglycerol, plasma total cholesterol and albumin were determined, and the subcutaneous and visceral adipose tissues were weighed. Results: Plasma triacylglycerol concentration in rats administered with 200 or 500 mg kg-1 of protamine was significantly lower than that in rats in the control group (200 mg kg-1 of protamine, P<0.05 at 1, 2, 3 and 4 h; 500 mg kg-1 of protamine P<0.05 at 2, 3 and 4 h). In rats fed with a high-fat diet, and 200 and 500 mg kg-1 of protamine, there was a decreased body weight gain by 52 and 66 g, respectively, reduced visceral fat by 5 and 8 g, respectively and subcutaneous tissue weights by 12 and 15 g, respectively. Plasma triacylglycerol was 17 and 45 mg per 100 ml lower in rats fed with high-fat diet plus 200 and 500 mg kg-1 of protamine, respectively. And cholesterol concentrations were 18 and 22 mg per 100 ml lower in both protamine groups, respectively. Conclusion: Our study demonstrates that protamine reduce weight gain and body fat accumulation through the inhibition of dietary fat absorption.