OBJECTIVE: Chitin and chitosan are polymers containing more than 5000 acetylglucosarnine and glucosamine units, respectively, and their molecular weights are over one million Daltons. The present study assessed the effects of chitin-chitosan on the activity of pancreatic lipase in vitro and on the degree of fat storage induced in mice by the oral administration of a high-fat diet for nine weeks. DESIGN: Mice were fed a high-fat diet and treated with chitin-chitosan for nine weeks. Experiments were also carried out to clarify whether or not chitin-chitosan inhibited pancreatic lipase activity in assay systems using triolein emulsified with lecithin, gum arabic or Triton X-100. RESULTS: Chitin-chitosan prevented the increase of body weight, hyperlipidaemia and fatty liver induced by a high-fat diet. Chitin-chitosan inhibited hydrolysis of triolein, emulsified with phosphatidyicholine, but not that of triolein emulsified with gum arabic and Triton X-100. These results suggest that the site of inhibitory action of chitin-citosan may not be the enzyme but its substrate. CONCLUSION: The anti-obesity effects of chitin-chitosan in high-fat diet-treated mice might be partly due to the inhibition of intestinal absorption of dietary fat. Consequently, chitin-chitosan might cause improvement of the fatty liver and hyperlipidaemia in mice fed a high fat diet through inhibiting intestinal absorption of dietary fat.

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