Effects of Roux-en-Y gastric bypass on the jejunal gluconeogenesis in obese rats

Objective To investigate the effects and mechanism of Roux-en-Y gastric bypass(RYGB)on the jejunal gluconeogenesis in obese rats. Methods Forty high fat diet-induced obese rats were divided into the blank group, sham surgery ad libitum fed (SA) group, sham surgery pair-fed (SPF) group and RYGB group according to the random number table, with 10 rats in each group. (1) The body weight and food intake of rats were regularly measured. (2)The oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) were done before operation and at postoperative week 2, 10 to evaluate glucose tolerance and insulin tolerance in rats. (3) The fasting serum TC, TG and free fatty acid were monitored at postoperative week 10. (4) Jejunal tissues of rats were abstracted for pathological examination. (5)The mRNA and protein expressions of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) were detected by RT-PCR and Western blot test, respectively. Measurement data were presented as ±s. Comparisons among the groups were analyzed using one-way ANOVA and pairwise comparisons were analyzed using LSD test. Repeated measures data were analyzed by the repeated measures ANOVA. Results (1)The body weight was changed from preoperation (325±9)g to (451±18)g at postoperative week 10 in the blank group, from (327±11)g to (446±14)g in the SA group, from (330±8)g to (442±15)g in the SPF group, from (328±10)g to (364±23)g in the RYGB group, showing significant difference in the changing trends among the 4 groups (F=422.03, P 0.05). There was significant difference in the body weight from week 4 to week 10 after surgery between the RYGB group and the blank group, SA group and the SPF group, respectively (P 0.05). From week 2 to week 10 after surgery, there was significant difference between the RYGB group and the blank group or the SA group, respectively (P<0.05). (2)The areas under the curve of OGTT was changed from preoperation (1 162±58)mmol/(L·minutes) to (1 181±66)mmol/(L·minutes) at postoperative week 10 in the blank group, from (1 168±135)mmol/(L·minutes) to (1 175±116)mmol/(L·minutes) in the SF group, from (1 159±92)mmol/(L·minutes) to (1 117±75)mmol/(L·minutes) in the SPF group, and from (1 189±108)mmol/(L·minutes) to (940±90)mmol/(L·minutes) in the RYGB group. The areas under the curve of ITT was changed from preoperative (533±80)mmol/(L·minutes) to (512±95)mmol/(L·minutes) at postoperative week 10 in the blank group, from (498±75)mmol/(L·minutes) to (545±73)mmol/(L·minutes) in the SF group, from (519±125)mmol/(L·minutes) to (538±92)mmol/(L·minutes) in the SPF group, and from (513±78)mmol/(L·minutes) to (426±36)mmol/(L·minutes) in the RYGB group. There were significant differences in the areas under the curve of OGTT and ITT among the 4 groups (F=14.03, 6.58, P<0.05). (3)The fasting serum TC, TG and FFA level were (5.41±0.19)mmol/L, (6.97±0.25)mmol/L, (1.51±0.08)mmol/L in the blank group, (5.51±0.16)mmol/L, (6.88±0.32)mmol/L, (1.53±0.05)mmol/L in the SA group, (5.32±0.41)mmol/L, (6.71±0.28)mmol/L, (1.44±0.11)mmol/L in the SPF group, (4.04±0.20)mmol/L, (4.05±0.29)mmol/L, (0.98±0.09)mmol/L in the RYGB group, with significant differences among the 4 groups (F=67.56, 234.92, 83.47, P<0.05). (4)The postoperative pathological examinations showed hypertrophy, bowel wall thickening, villus increasing of jejunum tissues of rats in the RYGB group compared with the blank group, the SA group, and the SPF group. (5)The jejunum mucosa mRNA and protein expressions of PEPCK and G6Pase were 1.00±0.11, 1.00±0.16, 105±11, 77±17 in the blank group, 1.04±0.14, 1.08±0.13, 96±10, 66±10 in the SA group, 1.07±0.19, 0.96±0.13, 99±15, 79±13 in the SPF group, and 1.44±0.10, 1.33±0.11, 129±16, 99±13 in the RYGB group, with significant differences among the 4 groups (F=19.80, 13.52, 11.85, 9.29, P<0.05). Conclusion RYGB can improve the metabolic conditions of obese rats, the mechanism of which may be related with increased jejunal gluconeogenesis. Key words: Obesity; Gluconeogenesis; Roux-en-Y gastric bypass