The Characteristics Of Insulin Resistance Syndrome Rat Model Induced By Types Of Fat

Objective Previous studies have indicated that the development of insulin resistance syndrome(IRS) were closely related to high-fat diets.The particular type and source of dietary fat, however, may have its own impact on the characters of IRS.Rats were fed a series of high-fat diets, identical but for fat source: lard,bean oil,hydrogenated-coconut oil and butterfat. The influence of different diets on rats'blood biochemical parameters, insulin sensitivity index, hepatic,panceatic island,coronary artery scathe, adiponectin content in plasma and its mRNA express in adipose tissue were analyzed, which can provid reference for establishment and empirical study of this animal model.Methods Forty 7-weeks-old healthy male SD rats assigned at random into five groups. The normal group was fed on standard laboratory chow(10.97% of calories as fat) and experimental groups were fed on isocaloric high fat diets(46.15% of calories as fat)for 6 weeks.Serum glucose(GLU), triglyeride(TG), HDL-cholesterol, cholesterol (CHO) and insulin were measured fortnightly interval. The insulin sensitivity was estimated by ISI index,ISI =㏑ 1/(FPG×FINS). At the end of the experiment, hepatic,panceatic island and coronary artery pathological examination was observed, moreover, the adiponectin mRNA expression was tested by RT-PCR.Results1. Hydrogenated-coconut oil group consumed the most chow,while lard group consumed the least; at the end, butterfat group were the heaviest of all groups, but lard group were the lightest;2. The glucose level of all groups increased, but there was no obvious different among the five groups. The bean oil group had considerably lower glucose level compared with normal group on the 15th day(P﹤0.05);3. Serum TG was significantly increased in butterfat group compared with other high-fat groups(P﹤0.05)in the end;4. High-fat feeding groups exhibited obviously lower HDL-cholestero(lP﹤0.05) than normal group, especially the bean oil group;5. Serum insulin increased in High-fat feeding groups,but normal group decreased. Moreover, it was significantly high in Lard,butterfat and bean oil groups compared with normal group(P﹤0.05)in the end;6. As for ISI, butterfat group had been lower than normal group(P﹤0.05)since the 29th day, in addition, butterfat and lard groups were both lower than normal group(P﹤0.05)in the end; 7. However there were mild difference in TC among the five groups;8. Hepatic was impaired in High-fat feeding groups including focalne necrosis, inflammatory cell infiltration and much vacuole; however,pancreatic islet and coronary artery were not impaired;9. High-fat feeding groups exhibited lower adiponectin level than normal group especially the butterfat group;in Hydrogenated-coconut oil group,seruma adiponectin content was positively related to HDL-c(r=0.784,p=0.021),TG (r=0.768,p=0.026)and TC(r=0.949,p=0.0003),while in Lard group it was negatively related to glucose(r=-0.742,p=0.035) and weigh(tr=-0.721,p=0.044);10. There was no significant different in the adiponectin mRNA expression between high-fat feeding groups and normal group.Conclusion1. High butterfat chows had the best effect of the four high fat feeds on establishment of IRS rat model, and lard was better than bean oil, but hydrogenated-coconut oil was the worst;2. High butterfat chows had the greatest sustained effect on TG , weight gain and glucose level;3. High Lard chows appears to produce the greatest level of serum insulin, the lowest ISI, but this group has the lowest energy intake and weight, moreover seruma adiponectin level was negatively related to glucose and weight;4. High Bean oil chows had the greatest effect on HDL-c and glucose, it could induce serum insulin significantly increased but decreased latter;5. High Hydrogenated-coconut oil chows could induce serum insulin significantly decresed but increased latter, and seruma adiponectin level was positively related to HDL-c,TG and TC;6. High-fat feeding did not induce fasting serum glucose and cholesterol of rat increased in 6 weeks;7. Hepatic was impaired by high-fat feeding for 6 weeks; however,pancreatic islet and coronary artery were not impaired;8. Serum adiponectin content decreased in rat fed with high-fat diet, but the mRNA expression level of adiponectin did not decrease .