Abstract: Objective To explore the effects of vitamin B₁₂ on blood lipid,liver lipid and immunoglobulin in rats with high-fat diet. Methods After 28 days of feeding high fat feed,30 sprauge-dawley（SD） male rats were divided into three groups equally and randomly by total cholesterol（TC）,including high-dose vitamin B₁₂ group（vitamin B₁₂ dose was 0.06 mg/kg）,low-dose vitamin B₁₂ group（vitamin B₁₂ dose was 0.04 mg/kg） and high-fat diet group,and the animals were fed by high fat diets continuously. Another 10 SD rats were given conventional diet as the control group. All rats were oral gavaged daily for 40 days. The high-fat diet group and the control group were given an equivalent amount of normal saline. The intracanthal venous blood samples of the animals were collected at the 0,20th and 40th day after intervention,to measure the levels of TC,triacylglycerol（TG）,low density lipoprotein cholesterol（LDL-C） and high density lipoprotein cholesterol（HDL-C）,and the body weight of the animals were recorded. At the end of experiment,the liver tissue was collected for measuring the levels of TC,TG,LDL-C,HDL-C in liver tissue homogenate. The ELISA method was used to determine the levels of immunoglobulin M（IgM）,IgG and IgA. Results At 0 day of intervention,the levels of serum TC,TG and LDL-C in high-fat diet group and vitamin B₁₂ intervention groups were higher than those in the control group,and the differences were statistically significant（all P<0.05）. At 20th day of intervention,the levels of serum TC,TG and LDL-C in high-fat diet group were higher than those in the control group,and the differences were statistically significant（all P<0.05）,while the levels of serum TC and LDL-C in low-dose and high-dose vitamin B₁₂ groups were higher than those in the control group,and the differences were statistically significant（all P<0.05）. At 40th day of intervention,the levels of serum TC and LDL-C in high-fat diet group were higher than those in the control group,and the differences were statistically significant（all P<0.05）. At 20th day of intervention,the levels of serum TC,TG and LDL-C in low-dose and high-dose vitamin B₁₂ groups were lower than those in the high-fat diet group,and the differences were statistically significant（all P<0.05）. At 40th day of intervention,the level of serum TC in high-dose vitamin B₁₂ group and the the level of LDL-C in low-dose and high-dose vitamin B₁₂ groups were lower than those in the high-fat diet group,and the differences were statistically significant（all P<0.05）. At 40th day of intervention,the levels of liver TC,TG and LDL-C in the high-fat diet group were were significantly higher than those in the control group（all P<0.05）,and the levels of IgM and IgG were significantly lower than those in the control group（all P<0.05）. The levels of liver TC and LDL-C inl ow-dose and high-dose vitamin B₁₂ groups and level of liver TG in high-dose vitamin B₁₂ group were significantly lower than those in the high-fat diet group（F=20.614,28.734,51.540,all P<0.05）,and the levels of IgM and IgG were significantly higher than those in the high-fat diet group（F=14.584,20.911,both P<0.05）. Conclusion The vitamin B₁₂ can effectively regulate the levels of blood lipid,liver lipid,IgM and IgG in rats with high-fat diet.

Key words: Vitamin B₁₂, High-fat diet, Blood lipid, Liver lipid, Immunoglobulin