Dietary chitosan improves hypercholesterolemia in rats fed high-fat diets

Abstract

The hypolipidemic mechanism of chitosan was investigated in male Sprague-Dawley rats. Animals were divided into 5 groups (n = 8): a normal fat control group, a high-fat control group (HF), a positive control group (CR), and 2 chitosan groups (CIS1 and CIS2). Chitosan was fed at the beginning (CIS1) and after 2 weeks (CIS2). A commercial diet with 5% (wt/wt) cellulose (HF), cholestyramine (CR), or chitosan (CIS1, CIS2) was fed for 6 weeks. Chitosan did not affect food intake but decreased body weight gain and significantly increased fecal fat and cholesterol excretion, reduced the lipid level in plasma and liver, increased liver hepatic and lipoprotein lipase activities compared with HF (P < .05), and tended to relieve the degenerated fatty liver tissue. No significant differences in all measurements were found between the CIS1 and CIS2 groups although the CIS1 rats exhibited lower lipid levels compared to those in the CIS2 group. The results suggest that chitosan reduced the absorption of dietary fat and cholesterol in vivo and could effectively improve hypercholesterolemia in rats.

Introduction

Coronary heart disease is the leading cause of death in the world. Excessive intake of calories and fats and the accumulation of adipose are major contributing factors. In recent years, many reports have focused on how to decrease plasma lipid concentrations and the absorption of fat in the intestinal tract to reduce diet-related chronic disease. Dietary fiber such as pectin and psyllium show some potent hypolipidemic effect [1].

Chitosan, a polymer of glucosamine, can be defined both chemically and physiologically as a dietary fiber because it cannot be degraded by the digestive enzymes of human [2]. Moreover, it is the only abundant polysaccharide derived from animals, and its cationic characteristics are different from other dietary fibers [3]. It is natural and nontoxic, and growing evidence indicate that it exhibits a marked hypolipidemic activity that would reduce the risk of cardiovascular diseases [4]. Chitosan has potent fat-binding capacity in vitro [5]. In addition, it could lower plasma and liver triacylglycerol (TG) and total cholesterol (TC) levels, increase fecal neutral steroid and bile acid excretion in rats [6], [7], [8], and lower the postprandial plasma TG level in broiler chickens [9]. Maezaki et al [10] was the first to report the hypocholesterolemic effect of chitosan in humans and found that chitosan effectively decreased plasma lipid level and had no side effect.

In many published studies, chitosan was fed to healthy animals. However, the potential benefits of chitosan would have great implications in the human with respect to hyperlipidemia and based on animal studies a mechanism for its actions on blood lipids is important to ascertain. At present, the actions of chitosan include interference of lymphatic absorption of cholesterol and fat [8], [11], increased fecal excretion of neutral steroids [6] and fat [12], and improvement of liver function [13]. All these actions require further study to elucidate a mechanism in animals before studies in human subjects continue. Therefore, to understand the mechanism of hypolipidemic activity of chitosan, we investigated the effect of dietary chitosan in rats on various lipid metabolites that can be translated to studies on hyperlipidemia in the human, and the applications of chitosan is human nutrition.