The Impact Of Dietary Fatty Acid Components On Rat's Insulin Resistance And Glucose Metabolism

Objective: Previous studies have indicated that components and amounts of dietary fatty acid were closely related to the development of insulin resistance. Different fatty acids may have its own impact on insulin action and glucose metabolism, and the underlying mechanisms may vary. Aimed at studying the impact of fatty acids on glucose tolerance in observed subjects, this project had designed an in vivo study on rats by giving long-term dietary interventions. Diets with different compositions of dietary fat were used, i.e. diet either high in saturated, monounsaturated, polyunsaturated fatty acids or mixed high fat diet. The impact of different diets on rats' plasma glucose, insulin secretion, glucose metabolism and insulin sensitivity were analyzed.Methods: Fifty 10-weeks-old healthy male Wister rats were assigned at random into five groups. The control group was fed with normal chew and experimental groups were fed with high fat diet by adding mixed fat, tea oil, bean oil or tallow oil into the normal chew. After feeding for 10 weeks, fasting plasma free fatty acids were analyzed by high performance liquid chromatogram, fasting plasma insulin, plasma glucose, triglyceride and cholesterol and so on were also analyzed. Intravenous glucose tolerance test was followed and insulin action andinsulin resistance level were estimated by Minimal Model method. Other indexes of insulin resistance and glucose metabolism were also calculated.Results: 1. Experiment results showed that the body weight of the rats was of no difference among different diet groups. 2. The framework of fasting plasma free fatty acids in the rats was highly correlated with the components of the fatty acids they diet in (P < 0.05). 3. Of all the high fatty acid intake groups, results of the fasting glucose and area under the curve of glucose of the intravenous glucose tolerance test were remarkably higher than that of the control group (P < 0.05) , while no significant differences were detected among all the high fatty acids intake groups. Although same fasting insulin level were found among groups, area under the curve of insulin of the intravenous glucose tolerance test were higher in the high saturated fatty acids diet group compared with that of the high monounsaturated fatty acids diet group (P < 0.05) . 4. The insulin sensitivity index of the control group was the highest among all the groups, followed by the mixed high fat and the high monounsaturated fatty acids diet group(P < 0.05). And the index of the above three were higher than that of the high saturated and high polyunsaturated fatty acids diet group (P < 0.05) . Other indexes, i.e. acute insulin response, indicated that the components of diet had obvious impacts on controlling insulin secretion as well as exerting insulin action.Conclusions: 1. Long term high fat diet intervention, by adding mixed fat, tea oil, bean oil or tallow oil to the normal chew, can leads to dyslipidosis. 2. In rats, high fat intake (up to 40% of energy come from fat, no matter it is from eithersaturated, monounsaturated, polyunsaturated or mixed fatty acids) result in insulin resistance. Diet high in saturated and polyunsaturated fat, in particular, induce greater insulin resistance than other kind of diet. 3. Different kinds of fatty acids may have different impact not only on insulin sensitivity but also on glucose clearance rate, and they therefore influenced the whole body glucose tolerance. 4. Under the same feeding pattern, no difference was found on rats' body weight among normal diet group and high diet groups. Still high fat diet was found to be unfavourable to rats' lipid and glucose metabolism, and different types of dietary fatty acids have different impact.