Interaction of dietary carbohydrate, protein and marginal copper on lipid metabolism in rats

A study was conducted to explore the effects of the Chinese diet on lipid metabolism. Male weaning Sprague-Dawley rats (N = 40) were fed purified diets for 7 weeks. These diets varied in carbohydrate (rice or corn starch, 62.2%), protein (casein or soybean, 15%) and copper (2.5-8 ppm) in a 2 x 2 x 2 factorial design. Rats receiving marginal levels of copper had significantly lower final body weights and feed efficiencies compared to rats fed adequate levels of copper (p <0.05). The total cholesterol (TC) and low density lipoprotein-cholesterol (LDL-C) levels in serum were lower in rats fed rice starch with casein or soy protein diets compared to rats fed corn starch (p <0.05). Serum triglyceride levels were affected by copper levels (p <0.001). High density lipoprotein-cholesterol (HDL-C)/TC was higher in rats fed rice starch/soy protein than in rats fed other diets. Groups receiving marginal levels of copper exhibited characteristic signs of copper deficiency: reduced serum copper, hypoceruloplasminemia, and higher relative heart weights (p <0.05). Liver total lipids and cholesterol were influenced by dietary factors; rice starch/soy protein groups had lower values than corn starch/casein groups (p <0.05). Copper adequate groups had lower total liver cholesterol than did the marginal copper groups (p <0.003). In conclusion, the growth and liver cholesterol level of rats were influenced by marginal copper level. Rice starch/soybean diet have protective effects on it.