Objective To investigate the effects of Roux-en-Y gastric bypass surgery on the obesity-related indexes, glycolipid metabolism indexes and expression of peroxisome proliferator-activatived receptor-γ (PPAR-γ) protein in visceral adipose tissues of rats with metabolic syndrome. Methods After 40 Sprague Dawley (SD) male rats with the age of 7-8 weeks were adaptively fed for 1 week, 30 rats were selected randomly and were fed with high-fat, high glucose and high salt diet combined with sucrose water for 12 weeks, and then 24 rats with metabolic syndrome were screened for eligibility and were allocated into the model group (n=11) and the operation group (n=13) based on the randomized complete block design. Rats of the model group and operation group received transection and reanastomosis of the gastrointestinal tract and Roux-en-Y gastric bypass surgery, respectively. Other 10 rats receiving normal feeding were divided into the control group. After executing rats at postoperative week 5, the levels of PPAR-γ protein in visceral adipose tissues around mesentery, double kidneys and bilateral epididymis were detected by the Western blot. Observation indexes: (1) obesity-related indexes included food intake before operation and at postoperative week 5, body weight, abdominal circumference, Lee's index, visceral adipose weight at postoperative week 5 and visceral adipose coefficient. (2) Glycolipid metabolism indexes included fasting plasma glucose before operation and at postoperative week 5, fasting serum insulin, homeostasis model assessment-insulin resistance (HOMA-IR), total cholesterol (TC), triglyceride (TG), high density lipoprotein- cholesterol (HDL-C), low density lipoprotein- cholesterol (LDL-C) and free fatty acid (FFA). (3) Level of PPAR-γ protein in visceral adipose tissues at postoperative week 5. Measurement data with normal distribution were presented as ±s. Comparison among groups was analyzed using the ANOVA, and comparison between groups was analyzed using the LSD-t test. Repeated measures data were analyzed by the repeated measures ANOVA. Results Three rats in the operation group were dead at postoperative week 1 with a mortality of 3/13 and no death was occurred in other groups. The consumption of food, body weight, abdominal circumference, Lee's index before operation and at postoperative week 5 were (26.9±1.5)g, (499±46)g, (18.2±0.4)cm, 309±9 and (27.7±2.1)g, (547±43)g, (18.6±0.5)cm, 312±8 in the control group, (26.1±1.8)g, (584±42)g, (19.3±0.6)cm, 317±13 and (28.8±1.7)g, (677±39)g, (20.6±0.7)cm, 334±11 in the model group, (25.9±2.1)g, (579±47)g, (19.4±0.5)cm, 311±5 and (17.5±0.8)g, (470±40)g, (18.1±0.4)cm, 302±4 in the operation group, respectively, with no significant difference in the above indexes before operation among the 3 groups (F=0.821, 0.784, 0.813, 0.642, P>0.05), and with significant differences in the changing trends of above indexes of 3 groups between before operation and postoperative week 5 (F=4.650, 3.852, 4.362, 4.042, P 0.05). There were significant differences in the visceral adipose coefficient at postoperative week 5 not only between control group and model group but also between model group and operation group (t=4.435, 4.657, P 0.05). The fasting plasma glucose, fasting serum insulin, HOMA-IR, TC, TG, HDL-C, LDL-C and FFA before operation and at postoperative week 5 were (4.3±0.9)mmol/L, (15.1±4.9)μmol/L, 2.19±1.43, (1.12±0.13)mmol/L, (1.3±0.5)mmol/L, (1.32±0.19)mmol/L, (0.9±0.4)mmol/L, (131±17)mmol/L and (4.3±1.2)mmol/L, (14.8±5.3)μmol/L, 2.29±1.37, (1.07±0.16)mmol/L, (1.2±0.7)mmol/L, (1.28±0.22)mmol/L, (0.8±0.5)mmol/L and (134±19)mmol/L in the control group, (6.1±0.7)mmol/L, (30.1±1.8)μmol/L, 7.86±1.56, (3.32±0.14)mmol/L, (2.5±0.6)mmol/L, (0.81±0.21)mmol/L, (2.8±0.7)mmol/L, (178±18)mmol/L and (6.1±0.7)mmol/L, (31.6±2.1)μmol/L, 8.50±1.66, (3.43±0.12)mmol/L, (2.7±0.5)mmol/L, (0.84±0.24)mmol/L, (3.1±0.5)mmol/L, (182±19)mmol/L in the model group, (6.2±0.6)mmol/L, (29.6±2.7)μmol/L, 7.43±1.03, (3.36±0.15)mmol/L, (2.6±0.5)mmol/L, (0.79±0.17)mmol/L, (2.9±0.6)mmol/L, (180±17)mmol/L and (4.5±0.8)mmol/L, (19.5±1.0)μmol/L, 5.17±0.25, (1.46±0.08)mmol/L, (1.5±0.4)mmol/L, (1.09±0.18)mmol/L, (1.2±0.3)mmol/L, (146±16)mmol/L in the operation group, respectively . There was no significant difference in the above indexes before operation among the 3 groups (F=0.625, 0.746, 0.813, 0.649, 0.754, 0.823, 0.587, 0.648, P>0.05). There were significant differences in the changing trends from before operation to postoperative week 5 among the 3 groups (F=4.714, 14.921, 18.971, 20.544, 5.731, 6.143, 10.276, 6.607, P 0.05). Conclusion Roux-en-Y gastric bypass surgery can reduce the visceral fat accumulation of rats with metabolic syndrome, improve metabolism of glucose and lipid and increase expression of PPAR-γ protein in visceral adipose tissue. Key words: Metabolic syndrome; Gastric bypass; Visceral fat; Glucose and lipid metabolism; Peroxisome proliferator-activatived receptor-γ protein