| Part One The influence of high-fat diet on3cell function and lipid m.etabolism during the process of obesity in SD rats[Objective] To observe the influence of high-fat diet on3cell function and lipid metabolism during the process of obesity in SD rats.[Methods] A total of36SD rats(5-weeks old) was randomly divided into normal diet group(ND), high-fat diet group(HD) and calorie-restricted high-fat diet group (LHD). The rats in ND group were given ordinary diet (350Kcal/100g) which contained13%fat,64%carbohydrates and2.3%protein, while those in the HD group were given high-fat diet (460Kcal/100g) contained47%fat,39%carbohydrate and14%protein. The composition of diet given to the rats in the LHD group was the same as that of HD group while the calorie of diet was controlled as the same as that of ND group. The distribution of body fat, fasting blood glucose (FBG) and insulin (FINS)level as well as the lipid profile including triglycerides (TG), cholesterol (TC),low-density lipoprotein cholesterol (LDL-ch), high-density lipoprotein cholesterol (HDL-ch) and free fatty acids (FFA) were compared among the three groups. The β cell function was evaluated by hyperglycemic clamps tests.[Results] After being fed with high-fat diet for12weeks, the increment of body weight and Lee Index of the rats in the HD group were significantly higher than those of the ND group and LHD group (P<0.05), while there was no significant difference between the LHD group and ND group(P>0.05). The epididymal and perirenal fat deposition of rats in the HD group were significantly more serious than that of the ND group(P<0.05). The epididymal fat deposition of the rats in the LHD group was significantly more serious than that of the ND group (P<0.05), while there was no significantly difference in the perirenal fat deposition between the two groups(P>0.05). The level of TC, FINS, LDL-ch, TG and HOMA-IR were all significantly higher than those of the ND group (P<0.05), while only TG level was significantly higher than those of the LHD group(P<0.05). There was no significant difference in above indexes except for the TG level and HOMA-IR between the LHD and ND group(P>0.05). The results of the hyperglycemic clamps tests showed that the glucose infusion rate of the rats in HD group was significantly lower than that of the LHD and ND group (P<0.05). At the same time, compared to the HD group and LHD group, the insulin secretion rate of the rats in the HD and LHD group was significantly lower than that of the ND group (P<0.05).[Conclusions]Obesity, dyslipidemia (increase in TC, TG and LDL-ch level) and insulin resistance could be induced by high-fat diet of12-weeks in SD rats. Calorie restricted high-fat diet could alleviate the obesity and dyslipidemia induced by high-fat diet, while it had little effect on insulin resistance.Part Two The influence of high-fat diet on oxidative stress, hepatic and pancreatic structure during the process of obesity in SD rats[Objective] To observe the influence of high-fat diet on oxidative stress, hepatic and pancreatic structure during the process of obesity in SD rats.[Methods] The rats involved in the study were the same as those in part one. After being fed with high-fat diet for12weeks, the levels of catalase (CAT) and glutathione peroxidase (GSH Px) in plasma as well as the levels of superoxide dismutase (SOD) and malondialdehyde (MDA) in the pancreatic homogenate were tested. Hematoxylin-eosin (HE) stained method was used to investigate the morphological change of liver and pancreas. And terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) was used to observe the islet cell apoptosis.[Results] After being fed with high-fat diet for12weeks, the levels of GSH Px and CAT in plasma and SOD in pancreatic homogenate of the rats in HD and LHD group were significantly lower than those in ND group (P<0.05), while the levels of MDA in pancreatic homogenate of the rats in HD and LHD group were significantly higher (P<0.05). There was no significant difference in the above indexes between the HD and LHD group (P>0.05). The liver HE stained slices showed that the steatosis and inflammatory cell infiltration were the most serious in the HD group and the steatosis was moderate in the LHD group with unobvious inflammatory cell infiltration. There was no liver steatosis in the ND group. The pancreatic HE and Tunel stained slices showed that the islet of the rats in HD and LHD group were significantly smaller and the islet cell apoptosis were more serious than those of the ND group.[Conclusions] High-fat diet of12-weeks could not only exacerbate the oxidative stress of SD rats, but also lead to liver steatosis, islet volume decrease and cell apoptosis. Calorie-restricted high-fat diet had little effect on oxidative stress and islet cell apoptosis induced by simple high-fat diet, but it could alleviate liver steatosis induced by high-fat diet. |
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