Chitosan and its derivative, chitosan oligosaccharide (CO), possess hypolipidemic and anti-obesity effects. However, it is still unclear if the mechanisms are different or similar between chitosan and CO. This study was designed to investigate and compare the effects of CO and high-molecular-weight chitosan (HC) on liver lipogenesis and lipid peroxidation, adipose lipolysis, and intestinal lipid absorption in high-fat (HF) diet-fed rats for 12 weeks. Rats were divided into four groups: normal control diet (NC), HF diet, HF diet+5% HC, and HF diet+5% CO. Both HC and CO supplementation could reduce liver lipid biosynthesis, but HC had a better effect than CO on improving liver lipid accumulation in HF diet-fed rats. The increased levels of triglyceride decreased lipolysis rate, and increased lipoprotein lipase activity in the perirenal adipose tissue of HF diet-fed rats could be significantly reversed by both HC and CO supplementation. HC, but not CO, supplementation promoted liver antioxidant enzymes glutathione peroxidase and superoxide dismutase activities and reduced liver lipid peroxidation. In the intestines, CO, but not HC, supplementation reduced lipid absorption by reducing the expression of fabp2 and fatp4 mRNA. These results suggest that HC and CO have different mechanisms for improving lipid metabolism in HF diet-fed rats.

Chitosan oligosaccharide is known to ameliorate hypercholesterolemia and diabetes. However, some studies found that chitosan oligosaccharide might induce mild to moderate hepatic damage in high-fat (HF) diet-induced obese rats or diabetic rats. Chitosan oligosaccharide can be as a dietary supplement, functional food, or drug. Its possible toxic effects to normal subjects need to be clarified. This study is designed to investigate the effects of chitosan oligosaccharide on plasma and hepatic lipid metabolism and liver histomorphology in normal Sprague-Dawley rats. Diets supplemented with 5% chitosan oligosaccharide have been found to induce liver damage in HF diet-fed rats. We therefore selected 5% chitosan oligosaccharide as an experimental object. Rats were divided into: a normal control diet group and a normal control diet +5% chitosan oligosaccharide group. The experimental period was 12 weeks. The results showed that supplementation of 5% chitosan oligosaccharide did not significantly change the body weight, food intake, liver/adipose tissue weights, plasma lipids, hepatic lipids, plasma levels of AST, ALT, and TNF-α/IL-6, hepatic lipid peroxidation and anti-oxidative enzyme activities, fecal lipids, and liver histomorphology in normal rats. These findings suggest that supplementation of 5% chitosan oligosaccharide for 12 weeks may not induce lipid metabolism disorder and liver toxicity in normal rats.