| Insulin resistance manifested as impaired insulin sensitivity to body tissues, i.e., insulin cannot dispose glucose effectively with normal insulin level. For some ethical, economic and technique reasons, the objects of research on insulin resistance are mainly rats, which are widely used in the fields of pathogenesis and pathophysiology of insulin resistance. In our study, male OLETF (Otsuka Long-Evans Tokushima Fatty) rats, genetically insulin resistance rat, were investigated for the influence of dietary fat composition on the development of insulin resistance. Part One Influence of Dietary Fat Composition on Factors Associatedwith Insulin Resistance in Male OLETF RatsPurpose: To investigate the influence of dietary fat composition on the development of insulin resistance and associated factors in male OLETF rats.Method: The male OLETF rats were divided into four groups, named group A, C, D and E, with LETO rats as control. Accordingly, the OLETF rats were fed with different diets separately, which were standard, high fat, high fat rich in n-6 PUFA and high fat rich in n-3 PUFA. The items observed from 14 weeks to 24weeks were amount of food ate, body weight, intraabdominal fat, fasting blood glucose, fasting insulin and C peptide, lipid profile, urinary ceruloplasmin index and albumin index. Euglycemic hyperinsulinemic clamp were carried out for the glucose disposal rates.Result: (1) The amount of food ate by OLETF rats were higher than that of LETO rats, with no differences among OLETF rats with different diet. (2) The body weight of OLETF rats was higher than that of LETO rats, with no difference among OLETFrats ate different diet. (3) The amount of intraabdominal fat was lower in LETO rats, and lower in OLETF rats fed with standard diet and high fat diet rich in n-3 PUFA than the rats fed with high fat diet and high fat diet rich in n-6 PUFA. (4) The fasting blood glucose level was lower in LETO rats than that of OLETF rats, with no difference among OLETF rats with different diet. (5) Compared to 14 weeks, the fasting insulin level in 24 weeks did not increase in LETO rats and OLETF rats fed with high fat diet rich in n-3 PUFA, while marked increased in OLETF rats fed with standard diet, high fat diet and high fat diet rich in n-6 PUFA. Yet, the fasting C peptide levels were almost same among all the rats. (6) There were no significant differences in lipid profile among all the OLETF rats, which were higher than that of LETO rats. (7) Urinary ceruloplasmin index and albumin index increased gradually with aging, with the lowest amplification in LETO rats, followed by OLETF rats with standard diet and high fat diet rich in n-3 PUFA. (8) The glucose disposal rate was highest in LETO rats, followed by OLETF rats with standard diet and high fat diet rich in n-3 PUFA.Conclusion: There existed insulin resistance in OLETF rats aged 14 weeks with elevated body weight and intraabdominal fat. Diet rich in n-3 PUFA can improve insulin sensitivity, and ameliorate intraabdominal fat accumulation and urinary ceruloplasmin and albumin excretion. Part Two Influence of Dietary Fat Composition on Glucose Metabolism in Male OLETF RatsPurpose: To analyze the glucose metabolism and insulin secretion after glucose loading in 14 weeks and 24 weeks rats, and observe the effect of diet fat composition on glucose metabolism.Method: The male OLETF rats were divided into four groups, named group A, C, D and E, with LETO rats as control. Accordingly, the OLETF rats were fed with different diets separately, which were standard, high fat, high fat rich in n-6 PUFA andhigh fat rich in n-3 PUFA. OGTT was carried out in 14 weeks and 24 weeks of age, in addition to blood glucose concentration, insulin and C peptide level was also detected before and after glucose loading. Some indices were calculated from the data of OGTT concerning insulin sensitivity and insulin secretion. Result: (1) The occurrence of diabetes was highest in OLETF rats fed with high fat diet rich in n-6 PUFA...
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