Effect of Dietary Chitin and Chitosan on Cholesterolemia of Rats

·imÛnek J . , BartoÀová H.: Effect of dietary chitin and chitosan on cholesterolemia of rats. Acta Vet. Brno 2005, 74: 491-499. Chitin – chitosan is being advertised as a food supplement that effectively lowers blood cholesterol concentration and controls obesity. The lard-fed rat was chosen because this model shares similarities with human hypercholesterolemia. The male rats were divided into six groups (A-F), each with 6 rats, and fed 6 weeks ad libitum diets prepared on base of commercial diet by addition of lard (diets D, E F), cholesterol (diet C), chitin (diets B, C, D) and chitosan (diet F). There were no significant differences in weight gain and feed efficiencies in all groups during experimental period. The histology examination of liver slices revealed the most pronounced periacinal (3.0) and centroacinal (1.3) steatosis in animals of the group C. In the F group was detected small periacinal steatosis only. The total serum cholesterol level was significantly increased (P < 0.05) in rats fed high fat diets (D, E, F; 2.21 ± 0.15, 2.25 ± 0.16, 2.27 ±0.23 mmol·l-1) and C group (2.16 ± 0.56 mmol·l-1) in comparison with control group (1.57 ± 0.26 mmol·l-1) and group B (1.68 ± 0.09 mmol·l-1). Similarly HLD-cholesterol levels were in groups B, C, D, E and F increased (1.02 ± 0.05, 0.90 ± 0.18, 1.30 ± 0.18, 1.34 ± 0.11 and 1.38 ± 0.24 mmol·l-1, resp.). While the cholesterol content in liver homogenates was significantly higher in animals fed cholesterol-rich diet (8.79 ± 0.50 mmol·g-1, P < 0.05), chitosan addition significantly depressed the cholesterol concentration (5.76 ± 0.95 mmol.g-1, P < 0.05). Faecal cholesterol excretion was greatest in the rats of C group (13.63 ± 2.93 mmol.g-1, P < 0.05). Also faeces of the animals fed the lard-enriched diets contained nonsignificantly more cholesterol than animals of control group. This effect seems to be reinforced by chitosan component in diet F. According to our results 5% chitin and/or chitosan addition have not prevented any increase in liver weight or the level of plasma cholesterol and also have not reduced the liver cholesterol content in rats fed enriched lard diet. In presence of chitosan higher excretion of faecal cholesterol and lipids were found. Chitin/chitosan, dietary hypercholesterolemia, rats Chitin is the major constituent of arthropods shells such as crabs, shrimps, lobsters and insects. Annual production of chitin was estimated to 1010 to 1011 t, which is close to estimated cellulose production. Although it is not derived from plants, it shares the characteristic with dietary fiber of being a polysaccharide that is indigestible by mammalian digestive enzymes. There can be three sources of chitinolytic enzymes in the animal’s digestive system: from the animal itself, from the endogenous commensal gut microflora, or from the ingested food (Gooday 1990). Chitin – chitosan is being advertised as a food supplement that effectively lowers blood cholesterol concentration and controls obesity. Both are uncritically recommended for curing many other diseases (Asaoka 1996). The mechanism by which chitin and chitosan, deacetylated forms of chitin, exert their action, is still poorly understood. Several studies have shown chitosan to be hypocholesterolemic in animal models (LeHoux and Grondin 1993). Chitosan has been suggested to reduce fat absorption from gastrointestinal tract by binding with anionic carboxyl groups of fatty and bile acids, and it interferes with emulsification of neutral lipids (i.e., cholesterol, other sterols) by binding them with hydrophobic bonds (Yli ta lo et al. 2002). Inhibition of cholesterol absorption reduces absorption of dietary cholesterol, but more importantly, ACTA VET. BRNO 2005, 74: 491–499 Address for correspondence: MVDr. J. ·IMÒNEK, CSc. Institute of Animal Physiology and Genetics Czech Academy of Sciences, VídeÀská 1083 142 20 Prague 4, Czech Republic Phone: +420 267 090 509 Fax:+420 267 090 500 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm prevents reabsorption of biliary cholesterol, which is instead eliminated in the faeces (Cohen 2004). Orally administered chitosan binds fat in the intestine, blocking absorption, and has been shown to lower blood cholesterol in animals and humans (Omrod et al. 1998). Chitosan acts by forming gels in the intestinal tract which entrap lipids but also other nutrients, including fat soluble vitamins and minerals, thus interfering with their absorption (Koide 1998). The hypolipidemic influence of chitosan may also be due to interruption of the enterohepatic bile acid circulation (Razdan and Pet tersson 1996) and the reduction in duodenal bile acid concentration (Razdan et al. 1997). Recently, chitosan has shown promise as a carrier in colon targeting, results suggesting that degradation by colonic bacterial enzymes might be one of the important properties of chitosan for its successful use in drugs colon targeting (Tozaki et al. 1997). In the proposed study, the effects of chitin and chitosan additives on cholesterolemia of rat fed diets with elevated fat contents were investigated. Since the effect of chitosan on decrease of serum cholesterol level in rats has been reported previously, the present study was carried out to compare the effect of chitin, which up to now has not been closely described. The purpose of the present study was to analyze the effect of chitin and chitosan addition on lipid metabolism of rats fed high lipids and cholesterol diets. The lard-fed rat was chosen because this model shares similarities with human hypercholesterolemia. Materials and Methods Animals and diets Young male Wistar rats were used in the study (VELAZ s.r.o., Koleã, CZ) and weighed approximately 175-192 g. They were housed individually in plastic cages at 24 oC with 12-h light (07.00-19.00 h) and dark cycle. All animals were allowed free access to a diet and water throughout the study period, with the exception of the night prior to blood collections for which the animals were fasted. To accustom the rats to the experimental conditions, they were initially fed the special commercial complete diet ST-1 for laboratory rats prepared by Kocanda Mill Co. (Czech Republic). The composition of the diet was as follows (per kg): nitrogenous components 240.0 g, fiber 37.2 g, fat 34.7 g, ash 65.1 g, calcium 13.2 g, phosphorus 8.7 g, sodium 1.8 g, vitamin A 33200 i.u., D3 cholecalcipherol 2500 i.u., alpha tocopherol 107.9 mg, cuprum sulfate pentahydrate 22.6 mg and sodium selenite 0.34 mg, antioxidants (butylhydroxytoluen, etoxyquin and butylhydroxyanizole) and citrex powder. After the 20 days adaptation period the animals were randomly divided into six groups, each with 6 rats, and weekly weighed. The compositions of the six used diets are shown in Table 1. All diets were prepared on base of ST-1 diet by addition of commercial lard (diets D, E F), cholesterol (diet C), chitin (diets B, C, D) and chitosan (diet F). Dietary components (cholesterol, chitin from crab shells and chitosan from crab shells) were purchased from Sigma Chemical Co. Chitosan degree of deacetylation was at least 85%. Powdered crab shell chitin was deproteinized, demineralized and decolorated by the procedures of No and Mayers (1997). All groups (A-F) were fed 6 weeks ad libitum.