| Summary: | 碩士 === 輔仁大學 === 食品營養學系 === 84 === The purpose of this study was to investigate the effect of dietary cholesterol and fasting on lipid metabolism in rats, and dietary fat levels on lipid metabolism in fasted rats. In experiment 1, twenty-eight Wistar rats aged 4 weeks were divided into 4 groups, fed diet with (NC) or without 1% cholesterol (N) for 4 weeks. At the termination of feed, two groups of rats were fasted 24 hours (fasted groups) and the others received the diets freely (fed groups). Serum and liver lipid content and tissue fatty acid composition were determined. Serum total cholesterol and triacylglycerol were not significantly different between N and NC groups. The concentration of serum triacylglycerol in fasted grpups were markedly lower than that of fed groups. Liver triacylglycerol was affected by dietary cholesterol, fasting and their interaction. NC groups caused the decrease of 18:0 and 20:4(n-6) level, but increased 18:l(n-9) and 18:2(n-6) contents in serum, liver and liver microsome. Fasting increased 18:0 and 20:4(n-6) level, and decreased the relative content of 18:l(n-9) fatty acid in serum and liver. The quantitative content of all fatty acid in serum were decrease after 24 hours fasting. A significant inverse correlation was observed between the 20:4(n-6) in triacylglycerol and total liver triacylglycerol in serum. And the proportional composition of 20:4(n-6) in cholesterol ester was significantly inversely correlated with total cholesterol in both liver and serum.
In experiment 2, rats fed the diet with high fat (20%) or low fat (5%) for 8 weeks. At the end of feeding, rats were fasted 24 hours. The concentration of serum total lipid and triacylglycerol were markedly lower in high fat diet than those of low fat diet. Total lipids and triacyiglycerol of liver in high fat diet had higher tendency than low fat diet, but not significantly different. The levels of dietary fat didn''t influence serum ketone body concentration. High fat diets had higher serum 18:2(n-6) and n-6 long-chain fatty acids. The level of 18:2(n-6) in liver of high fat diet was significantly higher than low fat diet, while 16:0 and 18:l(n-9) in tissue significantly decreased in dietary high fat.
The results suggest that there appeared to be an interaction of dietary cholesterol with fasting with respect to lipid metabolism. In addition, dietary fat levels influenced the serum lipids content and tissue fatty acid composition in fasted rats, but didn''t affect the concentraction of ketone body in serum.
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