Objective:To investigate the changes of plasma high density lipoprotein cholesterol (HDL-C) and metabolic indicators in obese patients after laparoscopic sleeve gastrectomy (LSG).Methods:The retrospective cohort study was conducted. The clinical data of 69 obese patients who were admitted to the Tenth People′s Hospital of Tongji University from August 2013 to March 2017 were collected. There were 32 males and 37 females, aged (33±12)years, with a range from 18 to 65 years. Of 69 patients, 44 patients with preoperative HDL-C concentration <1.04 mmoL/L were allocated as low HDL-C group, and 25 patients with preoperative HDL-C concentration ≥1.04 mmoL/L were allocated as normal HDL-C group. Sixty-nine patients underwent LSG. Observation indicators: (1) analysis between preoperative HDL-C and clinical indicators; (2) follow-up; (3) stratified analysis of plasma HDL-C. Follow-up was conducted using outpatient examination and hospitalization review to detect changes of plasma HDL-C, insulin resistance index, uric acid, free fatty acids and body mass every 3 months after operation up to September 2017. Measurement data with normal distribution were represented as Mean± SD, and comparison between groups was analyzed using the t test. Measurement data with skewed distribution were represented as M ( P25, P75), and comparison between groups was analyzed using the Mann-Whitney U test. Count data were expressed as absolute numbers or percentages, and comparison between groups was analyzed using the chi-square test. Pearson correlation coefficient was used to analyze measurement data with normal distribution, and Spearman correlation was used to analyze measurement data with skewed distribution. Repeated measurement data were analyzed by ANOVA. Results:(1) Analysis between preoperative HDL-C and clinical indicators: results of correlation analysis showed that the preoperative plasma HDL-C concentration was negative correlated with the body mass, height, abdominal circumference, insulin resistance index and triglyceride in 69 patients ( r=-0.246, -0.307, -0.262, -0.253, -0.301, P<0.05), and the preoperative plasma HDL-C concentration was not correlated with the age, body mass index (BMI), fasting blood glucose, glycosylated hemoglobin, alanine aminotransferase, aspartate aminotransferase, gamma glutamyltransferase, uric acid, creatinine, free fatty acid, fasting serum insulin, total cholesterol and low density lipoprotein cholesterol ( P>0.05). The preoperative plasma HDL-C concentration was still negative correlated with the body mass in 69 patients after adjusting for age, BMI, fasting blood glucose, glycosylated hemoglobin, fasting serum insulin and insulin resistance index ( r=-0.277, P<0.05). (2) Follow-up: 69 patients were followed up postoperatively for 6 months (6 months, 12 months). The plasma HDL-C concentration, insulin resistance index, uric acid, free fatty acids, body mass of low HDL-C group at postoperative 3 and 6 months were (0.96±0.18)mmol/L, 2.20(0.51, 11.66), (411±93)μmol/L, 0.57 mmol/L (0.20 mmol/L, 1.00 mmol/L), (92±18)kg and (1.11±0.18)mmol/L, 2.19(0.71, 8.75), (389±100)μmol/L, 0.40 mmol/L(0.13 mmol/L, 1.10 mmol/L), (86±17)kg, respectively. The above indicators of normal HDL-C group at postoperative 3 and 6 months were (1.17±0.24)mmol/L, 2.22(0.24, 7.04), (379±105)μmol/L, 0.60 mmol/L(0.27 mmol/L, 1.10 mmol/L), (84±16)kg and (1.34±0.20)mmol/L, 1.60(0.36, 5.56), (359±92)μmol/L, 0.42 mmol/L (0.16 mmol/L, 2.90 mmol/L), (80±18)kg, respectively. There was significant difference in the changes of postoperative plasma HDL-C concentration between the two groups ( F=41.443, P<0.05), and there was interaction between groups and time points ( F=6.252, P<0.05). There was significant difference between different time points ( F=29.900, P<0.05). There was significant difference in the changes of postoperative insulin resistance index between the two groups ( F=4.313, P<0.05), and there was no interaction between groups and time points ( F=2.298, P>0.05). There was significant difference between different time points ( F=29.800, P<0.05). There was no significant difference in the changes of postoperative uric acid between the two groups ( F=1.669, P>0.05), and there was no interaction between groups and time points ( F=0.111, P>0.05). There was significant difference between different time points ( F=12.796, P<0.05). There was significant difference in the changes of postoperative free fatty acids between the two groups ( F=5.465, P<0.05), and there was no interaction between groups and time points ( F=0.504, P>0.05). There was no significant difference between different time points ( F=1.405, P>0.05). There was significant difference in the changes of postoperative body mass between the two groups ( F=5.614, P<0.05), and there was no interaction between groupsand time points ( F=2.174, P>0.05). There was significant difference between different time points ( F=497.496, P<0.05). (3) Stratified analysis of plasma HDL-C. ① Changes of postoperative plasma HDL-C in obese patients of different genders: of 69 patients, the plasma HDL-C concentration of the 32 male patients before operation and at postoperative 3 and 6 months were (0.91±0.19)mmol/L, (1.02±0.24)mmol/L, (1.18±0.23)mmol/L, respectively, and the percentage increase of plasma HDL-C concentration at postoperative 3 and 6 months were 12.00%(4.00%, 12.00%)and 20.00%(12.00%, 39.25%), respectively. The above indicators of the 37 female patients were (1.05±0.21)mmol/L, (1.06±0.22)mmol/L, (1.22±0.22)mmol/L and 0(-9.50%, 8.25%), 12.00%(2.00%, 23.00%), respectively. There was significant difference in the changes of percentage increase of plasma HDL-C concentration between the male and female patients ( F= 6.716, P<0.05), and there was interaction between groups and time points ( F=3.861, P<0.05). There was significant difference between different time points ( F=37.374, P<0.05). ② Changes of postoperative plasma HDL-C in obese patients of different genders in low HDL-C group and normal HDL-C group: of 44 patients in low HDL-C group, the plasma HDL-C concentration of the 24 male patients before operation and at postoperative 3 and 6 months were (0.82±0.12)mmol/L, (0.99±0.21)mmol/L, (1.12±0.22)mmol/L, respectively, and the percentage increase of plasma HDL-C concentration at postoperative 3 and 6 months were 16.00%(-1.75%, 28.75%) and 27.50%(15.75%, 43.50%), respectively. The above indicators of the 20 female patients in low HDL-C group were (0.89±0.08)mmol/L, (0.93±0.14)mmol/L, (1.10±0.14)mmol/L and 1.50%(-8.25%, 16.50%), 18.00%(9.00%, 23.00%), respectively. There was significant difference in the changes of percentage increase of plasma HDL-C concentration between the male and female patients ( F=4.503, P<0.05), and there was interaction between groups and time points ( F=3.594, P<0.05). There was significant difference between different time points ( F=37.096, P<0.05). Of 25 patients in normal HDL-C group, the plasma HDL-C concentration of the 8 male patients before operation and at postoperative 3 and 6 months were (1.15±0.12)mmol/L, (1.12±0.32)mmol/L, (1.32±0.21)mmol/L, respectively, and the percentage increase of plasma HDL-C concentration at postoperative 3 and 6 months were -1.00%(-14.00%, 12.00%), 13.50%(6.75%, 32.50%), respectively. The above indicators of the 17 female patients in normal HDL-C group were (1.23±0.16)mmol/L, (1.20±0.20)mmol/L, (1.36±0.20)mmol/L and 0(-13.75%, 4.25%), 5.50%(0, 28.50%), respectively. There was no significant difference in the changes of percentage increase of plasma HDL-C concentration between the male and female patients ( F=0.209, P>0.05), and there was no interaction between groups and time points ( F=0.176, P>0.05). There was significant difference between different time points ( F=6.481, P<0.05). Conclusions:For patients with low or normal plasma HDL-C concentration preoperative, there are significant differences in the changes of HDL-C, insulin resistance index, free fatty acids and body mass after LSG. There is significant difference in the changes of postoperative percentage increase of plasma HDL-C concentration between male and female patients who with low plasma HDL-C concentration preoperative.