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Effects of Chitosan on Lipid Metabolism and Colon Physiology in Rats
|Authors: ||Hsien-Tsung Yao|
|Contributors: ||NTOU:Department of Food Science|
|Issue Date: ||2011-06-30T07:38:41Z
|Abstract: ||本研究主要探討幾丁聚醣對大白鼠脂質代謝及腸道生理之影響，結果發現，幾丁聚醣會明顯降低血漿總膽固醇、very low density lipoprotein cholesterol (VLDL-C)及low density lipoprotein cholesterol (LDL-C)，並增加(high density lipoprotein cholesterol) HDL-C 濃度，而其中以VLDL-C下降最多。幾丁聚醣會明顯降低VLDL上游離及酯化型膽固醇，並增加三酸甘油酯的比例，降低VLDL表面脂質/核心脂質的比值，顯示幾丁聚醣會改變VLDL脂質組成與顆粒大小。此外，幾丁聚醣會增加糞便脂質的排出，降低肝臟游離、酯化型膽固醇及三酸甘油酯含量，但會提高肝臟脂肪酸合成酶活性。 幾丁聚醣在有維生素C (1%)的添加下，短期間(1週)會明顯降低禁食與餐後三酸甘油酯濃度，並延緩血糖濃度上升，但長期(9週)添加高量維生素C (1%)的添加下，卻會降低血漿胰島素濃度，增加血漿三酸甘油酯及肝臟膽固醇酯的堆積。此外，幾丁聚醣會增加糞便膽固醇的排出，但並不會改變糞便膽酸的含量，而維生素C的添加對糞便脂質的排出並無促進作用。值得注意的是，長期攝食高去乙醯度之幾丁聚醣(DDA: 97%)會增加大白鼠的氧化壓力，增加血漿thiobarbituric reactive substance (TBARS)值、LDL氧化及紅血球溶血率。幾丁質及幾丁聚醣在腸道中會被腸內細菌分解成低分子量的幾丁寡醣，給予大白鼠幾丁質水解物後會明顯提升盲腸中乙酸及乳酸的濃度，而盲腸內容物pH值亦有偏低的趨勢，但幾丁寡醣並不會影響糞便中短鏈脂肪酸濃度，且糞便中總厭氧菌、Bifidobacterium及Lactobacillus的細菌數亦無明顯差異。但幾丁聚醣在盲腸中並不易被腸內菌所利用，其被盲腸內細菌發酵所產生之短鏈脂肪酸含量明顯少於纖維素被盲腸內細菌發酵所產生之短鏈脂肪酸含量，且大白鼠盲腸中乳酸濃度亦明顯較低，這些結果可能是造成盲腸pH值較高的原因。此外，若將菊醣添加在幾丁聚醣飲食中，不但會增加大白鼠盲腸及糞便中短鏈脂肪酸濃度，亦會降低盲腸及糞便pH值，且糞便細菌酵素黏液素酶及β-醛醣酸酶活性皆會明顯下降。另一方面，幾丁聚醣會明顯降低糖尿病大白鼠血膽固醇、血糖、VLDL-C及LDL-C，而HDL-C亦會明顯提高，顯示幾丁聚醣亦有利於糖尿病之脂質代謝與醣代謝。此外，本研究發現幾丁聚醣亦會降低糖尿病大白鼠前段小腸雙醣酶及肝臟六碳醣激酶活性。雖然幾丁聚醣會降低糖尿病大白鼠血清中維生素E的濃度，但卻會降低血清TBARS值；有趣的是，菊醣添加亦會進一步降低糖尿病大白鼠血清及肝臟TBARS值。|
These studies were designed to investigate the nutritional modification of chitosan on lipid metabolism and colon physiology in rats. Lower plasma total cholesterol, very low-density lipoprotein cholesterol (VLDL-C), low-density lipoprotein cholesterol (LDL-C) and higher high-density lipoprotein cholesterol (HDL-C) were observed in rats fed on a diet containing chitosan. Rats fed with chitosan diet had increased triglyceride percentages and decreased free cholesterol, cholesteryl ester and phospholipid percentages in VLDL lipid composition. Chitosan significantly decreased the surface lipid proportions and increased the core lipid proportions in VLDL particle, suggesting that chitosan may alter the lipid composition and particle size in VLDL. Rats fed the chitosan diet with 1% sodium ascorbate supplementation had lower fasting and postprandial plasma triglyceride concentration after one week of feeding period. However, higher plasma triglyceride and lower insulin concentration level was observed in rats fed with the chitosan diet with 1% sodium ascorbate supplementation when the experiment was done for night weeks. Chitosan significanty increased fecal total lipids and cholesterol content, but did not change the fecal total bile acids excretion. No synergism effect was observed in fecal lipids excretion in rats fed with the chitosan diet with sodium ascorbate supplementation. It was worthy noting that plasma thiobarbuturic reactive substance (TBARS), LDL lipid peroxidation, red blood cell (RBC) hemolysis was significantly increased while plasma total antioxidant status (TAS) was significantly decreased in rats fed the chitosan diet for night weeks. Liver free cholesterol and cholesteryl ester content was significantly decreased in rats fed the chitosan diet. However, liver cholesteryl ester content was dramatically increased in rats fed with the chitosan diet with sodium ascorbate sulpplementation. On the other hand, some degradation products of chitin and chitosan, such as N-acetylchitooligosaccharides, exhibit various physiological activities. Our results showed that rats fed the chitin hydrolysate had significantly increased cecal acetate and L-lactate concentration but did not change the fecal short chain fatty acid (SCFA) concentration. There was also no significant difference in fecal total anaerobes, bifidobacterium and lactobacillus number after the chitin hydrolysate treatment. Chitosan significantly decreased cecal acetate and butyrate concentration but increased fecal acetate, propionate and butyrate concentration. In addition, rats fed with a chitosan diet had higher total cecal weight and pH value. It was interesting to note that inulin supplement induced an increase in cecal and fecal SCFA concentration, especially in propionate and butyrate, and a decrease in pH value in rats fed with the chitosan diet. Fecal mucinase and bglucuronidase activity was also significantly reduced in rats fed with a diet with chitosan treatment. In diabetic rats, chitosan dramatically decreased plasma glucose, total cholesterol and increased HDL-C concentration, suggesting that chitosan may also improve glucose and lipid metabolism in diabetic rats. Although chitosan reduced serum a-tocopherol concentration, lower serum TBARS value was found in diabetic rats fed with the chitosan diet. In addition, lower proximal intestinal disaccharidase and higher liver hexokinase activities were observed in diabetic rats after the chitsan treatment. It was interesting that inulin supplement induced a decrease in serum and liver TBARS value in diabetic rats fed with the chitosan diet.
|Appears in Collections:||[食品科學系] 博碩士論文|
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