Abstract: 【Objective】This experiment was conducted to investigate the effect of dietary fat source and dosages on growth performance, health status, serum lipid indicators and liver cholesterol metabolism-related gene mRNA expression level and to explore the mechanism of dietary fats source and dosage on hepatic cholesterol metabolism of mice. Results will contribute to select a suitable amount and type of oil for mammal.【Method】 Forty eight 3-week-old healthy KM mice whose body weights were 16-19 g were randomly assigned into four groups with 4 replicates per group and 3 mice each. Mice were fed: normal diet (control group); 4% bean oil diet (group B); 4% emulsified coconut powder diet (group L); 8% emulsified coconut powder diet (group H)for fourteen days, respectively. During the whole experiment, daily feeding times, feed quantity and remaining amount of feed of each time were recorded. All animals were fed and watered ad libitum. According to the recorded data, body weight and average daily feed intake (ADFI), the average daily gain (ADG), feed gain ratio (F/G) were calculated. Blood distribution, health index and liver weight of mice were measured. The concentrations of triglyceride (TG), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), and low density lipoprotein cholesterol (LDL-C) in serum were determined. The expression of mRNA of 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), cholesterol 7 alpha-hydroxylase (CYP7A1) and low density lipoprotein-receptor (LDLR) in liver were determined by real time PCR.【Result】Supplementation of 4% bean oil significantly increased body weight, ADFI and liver index of mice compared with the control group (P＜0.05), but had no significant effects on ADG, F/G or liver weight (P＞0.05). Supplementation of 4% emulsified coconut powder failed to significantly change growth performance of mice compared with the control group (P＞0.05). Supplementation of 8% emulsified coconut powder significantly increased ADFI of mice compared with the control group (P＜0.05), but had no significant effects on other growth performance (P＞0.05). Healthy status: Fat had no significant effects on blood distribution and health index (P＞0.05). Compared with the control group, TC and HDL-C levels in the serum significantly decreased in 4% bean oil group (P＜0.05), TG and LDL-C levels have no significant difference. Supplementation of 4% emulsified coconut powder had no significant effects on serum lipid index of mice (P＞0.05). Supplementation of 8% emulsified coconut powder significantly decreased serum TC levels (P＜0.05), but had no significant effects on TG, HDL-C and LDL-C levels (P＞0.05). Supplementation of 8% emulsified coconut powder significantly increased the expression of mRNA of CYP7A1 of mice compared with the control group (P＜0.05). Four percent bean oil diet and 4% emulsified coconut powder diet had no significant effects on the expression of mRNA of CYP7A1 (P＞0.05). There were no significant differences in the expression of mRNA of HMGCR and LDLR among four groups (P＞0.05). 【Conclusion】 Supplementation of bean oil increased the growth performance on ADFI and body weight of mice, decreased serum total cholesterol and high-density lipoprotein cholesterol. Supplementation of high doses emulsified coconut powder improved ADFI and decreased serum total cholesterol, and increased CYP7A1 mRNA expression in liver of mice. Compared to the high dosage of emulsified coconut powder, low dosage had no significant effects on improving lipid metabolism of mice. Fat in the diet probably affected liver cholesterol metabolism by regulating the gene expression levels of cholesterol metabolism-related enzymes in the liver to maintain cholesterol metabolism homeostasis in mice.

Key words: fat source, lipid index, cholesterol metabolism, gene expression