Effect Of Swimming Training On Tumor Necrosis Factor-α And Uncoupling Protein 2 Expression In Visceral Adipose Tissue Of High-fat-diet Rat

PURPOSE:With the development of economy, Chinese people's diet pattern also changed, transforming from low fat and more vegetable pattern to high fat and few vegetable diet pattern. The investigation of Chinese health and nutrition in 2004 showed that high fat diet and insufficient physical activity were important influencing factors resulting in overweight, obesity, diabetes and hyperlipoidemia. Aerobic exercise is the acknowledged effective method to prevent and treat obesity. The traditional viewpoint think obesity and weight reduction by exercise are resulted from the change of energy balance. Adipose tissue's main function is energy store. Along with the molecular biology technology widely being applied, the researcher discovered that the adipose tissue also was an endocrine organ. It may secrete many kinds of hormones and cytokines which can participate energy adjustment through autocrine and paracrine. The uncoupled protein (UCPs) family has important contribution of affecting rest metabolism rate. UCP₂ is rich in the white adipose tissue. Tumor necrosis factor (TNF)- alpha is one of the cytokines which the fatty tissue secretes. Many studies reported that TNF- alpha enhanced the UCP₂ expression in adipose tissue in vivo and in vitro. TNF- alpha of the adipose tissue in obese people and fat animal model remarkably elevated, but the UCP₂ expression dropped. This change possibly had important influence to the obesity occurrence. There is little research about the exercise's influence on the cytokine and the UCPs in the fatty tissue. No domestic or foreign researchs are reported about the exercise's effect on TNF- alpha and the UCP2 of white adipose tissue under the high fat diet condition.The purpose of the present experiment is to observe the change of UCP₂mRNA and TNF- α mRNA in adipose tissue, as well as TNF- α concentration in adipose tissues and blood after 12 weeks high-fat-diet with swimming training, to discuss the effect of swimming training on preventing obesity, to analyze energy metabolic regulation of adipose tissue by swimming training in different diet pattern. It will provide further theoretical evidences for the recognition of obesity as well as weight reduction by exercise. METHODS:Thirty 4-week-old male SD rats were randomly assigned to four groups: control group(C);high-fat-diet group (H);swimming-trained group (E);high fat diet combined with swimming-trained (HE) group. The rats in H and HE groups were fed by high fat diet,and the rats in C and E groups were fed by standard rodent chow ad libitum. Lipid energy percentage of high fat diet and standard diet was 35% and 11 %, respectively. Animals in the exercise-trained groups were trained by swimming exercise for 12 weeks (90min/day, 5days/week). At the end of experiment, all rats were killed, and the blood, epididymal fat as well as perirenal fat were obtained. UCP2 mRNA and TNF-a mRNA in adipose tissue were tested by reverse transcription-polymerase chain reaction (RT-PCR). Serum and adipose TNF-a concentration were tested by enzyme-linked immunosorbentassay (ELISA). RESULTS:The results showed that, the body weight and serum free fatty acids (FFA) of H group were significantly higher than that of C group, and the H group presented the obesity tendency. UCP2mRNA and TNF- alpha mRNA in the white adipose tissue as well as serum TNF- alpha of H group was significantly higher than that of the HE group and C group. Compared with HE group and C group, adipose TNF- alpha concentration of H group increased, but no statistic significant difference. Total intake calory of HE group in experimental period had no significantly difference with that of H group, but was significantly higher than that of E group. Compared with C group, the body fat content of HE group and E group was lower, but body weight and serum FFA had no difference. UCP2mRNA, TNF- alpha mRNA, and TNF- alpha content in adipose tissue of HE group were remarkably higher than E group and C group, but the TNF- alpha in serum had no significantly difference with E and C groups. CONCLUSIONS:1. The increase of UCP2mRNA expression after high fat diet and high fat diet with swimming training is a kind of compensation mechanism and its role is to prevent body adipose tissue accumulation.2. TNF- alpha content in adipose tissue of high fat diet rats was reduced by 12 weeks swimming training, and it may avoid the impairment which is induced by high TNF- alpha.3. TNF- alpha secreted by adipose tissue adjust the UCP2 in adipose tissue. The swimming training may enhance the adjustment of TNF- alpha to UCP2 in adipose tissue of high fat diet rats, and prevent the fat excessive accumulation.