Characteristic Of Muscle Fiber Type And Lipid Metabolism In Diet-induced Obesity And Obesity Resistance Rats

Research purposeTo observe the characteristic of muscle fiber type and lipid metabolism in obesity and obesity resistance rats, the rat models were established by high fat diet. Muscle fiber composition, fatty infiltration of liver, and blood biochemical indicators including fasting plasma lipid, fasting plasma glucose and fasting insulin were detected. The experience is mainly aim at to explore the mechanism and metabolism characteristic in obesity and obesity resistance rats, and to provide experimental evidence for prevention and treatment of obesity.Research method50 healthy male SD rats were randomly divided into normal control group (n=10) and high fat group (n=40), which were respectively fed with basic diet and high-fat diet for 8 weeks. Rats in diet-induced obesity group (the DIO group, n=10, the 10 rats with higher body weights) and Diet-induced obesity resistance group (the DIO-R group, n=10, the 10 rats with lower body weights) were then selected according to their body weights in high fat group. After the body weight and length were measured, the CON, DIO and DIO-R rats were fasting 12h and anaesthetized. Their venous blood of vena cava inferior, gastrocnemius muscle and liver were collected afterward. Measurements covered body shape index which including weight, body length, and Lee's index, blood parameters including blood triglyceride (TG), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), fasting plasma glucose, fasting insulin and insulin resistance index, the percentage of muscle fiber type I and type II which were calculated by number micro-metering system after ATP enzymatic histochemical stain, and the measurement of fatty liver including liver wet weight, liver/body ratio, and microscopic observations after HE staining. Spssl6.0 software package was used for data statistic including description statistics and one-way ANOVA.Research result1. The measurement result of body sharp indicesThe differences of weight between DIO group (548.0±9.2g) and DIO-R group (460.9±17.0g), DIO group and CON group (482.2±37.3g) was highly significant (P<0.01). There were significant difference of Lee's index (P<0.05) between DIO group (305.9±12.0) and DIO-R group (294.8±9.0). The differences of body length among the 3 groups, of weight and Lee's index between DIO-R group and CON group, of Lee's index between DIO group and CON group (300.3±12.6) were not significant (P>0.05).2. The percentage of muscle fiber typeTypeⅠvs. typeⅡmuscle fiber percentages of DIO group and DIO-R group were respectively 28.16±1.07% vs.71.84±1.07% and 30.52±1.27% vs.69.48.±1.27%, there was a highly significant difference between the two groups (P<0.01). However, there were no significant differences (P>0.05) when they were compared with CON group (29.21±2.56% vs.70.79±2.56%).3. The results of blood biochemical parametersThe different level of TC between DIO group and DIO-R group was highly significant (P<0.01,1.01±0.26mmol/L and 0.75±0.14 mmol/L respectively), and the level of FIN between the 2 group was significantly different(P<0.05,21.40±9.59mIU/L and 14.20±4.34mIU/L respectively). There are no significant differences among other indices of group DIO, DIO-R and CON.4. The severity of liver fatty infiltrationWhen been compared with CON group which was fed with basic diet, the high fat diet induced DIO and DIO-R group showed a serious liver fatty infiltration by the integrate analysis of liver wet weight, liver/body ratio, unaided eye observation and microscope observation. However, the severity of liver fatty infiltration of DIO-R group was not as serious as DIO group.Conclusions1. It is a practical method to set up DIO and DIO-R rat models by feeding high fat diet for 8 weeks.2. The DIO-R rats has higher percentage of typeⅠmuscle fiber and lower percentage of typeⅡmuscle fiber when been compared with DIO rats.3. High fat induced obesity resistance rats have a lower level of blood lipid and insulin than high fat induced obesity rats.4. When being fed with high fat diet, DIO-R rats can relieve the severity of liver fatty infiltration by self accommodate. However, long-term high fat diet can induce fatty liver in no matter DIO rats or DIO-R rats.