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. 2016 Nov 1;311(5):R979-R987.
doi: 10.1152/ajpregu.00125.2016. Epub 2016 Aug 31.

The Role of Proximal Versus Distal Stomach Resection in the Weight Loss Seen After Vertical Sleeve Gastrectomy

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Free PMC article

The Role of Proximal Versus Distal Stomach Resection in the Weight Loss Seen After Vertical Sleeve Gastrectomy

Bhushan V Kulkarni et al. Am J Physiol Regul Integr Comp Physiol. .
Free PMC article

Abstract

The mechanisms involved in the weight loss seen after vertical sleeve gastrectomy (VSG) are not clear. The rat stomach has two morphologically and functionally distinct proximal and distal parts. The rat model for VSG involves complete removal of the proximal part and 80% removal of the distal part along the greater curvature. The purpose of this study was to understand the potential independent contributions of removal of these distinct gastric sections to VSG outcomes. We prepared four surgical groups of male Long-Evans rats: VSG, sham surgery (control), selective proximal section removal (PR), and selective distal section removal (DR). Gastric emptying rate (GER) was highest after VSG compared with all other groups. However, PR, in turn, had significantly greater GER compared with both DR and sham groups. The surgery-induced weight loss followed the same pattern with VSG causing the greatest weight loss and PR having greater weight loss compared with DR and sham groups. The results were robust for rats fed regular chow or a high-fat diet. Body mass analysis revealed that the weight loss was due to the loss of fat mass, and there was no change in lean mass after the surgeries. In conclusion, removal of the proximal stomach contributes to most, but not all, of the physiological impact of VSG.

Keywords: gastric emptying rate; sleeve gastrectomy; weight loss.

Figures

Fig. 1.
Fig. 1.
Photos of the vertical sleeve gastrectomy (VSG; A), proximal section removal (PR; B), and distal section removal (DR; C) surgeries. For VSG and PR, only one cut was made to remove tissue. For DR, two cuts were made as close to the limiting ridge as possible.
Fig. 2.
Fig. 2.
Timeline of experiments in chow and high-fat diet (HFD)-fed surgical groups.
Fig. 3.
Fig. 3.
Body weight changes after surgery. Body weight trajectories after surgical procedures are depicted for the chow group (A) and for the HFD group (B). The DR group had a similar body mass compared with sham in both the chow and HFD groups. VSG body weights were significantly lower than those of sham and DR in both the chow and HFD groups. PR body weights were significantly lower than those of sham and DR only in the chow group. *Significantly different vs. sham, P < 0.05. $Significantly different vs. DR, P < 0.05.
Fig. 4.
Fig. 4.
Body composition changes after surgery. NMR analysis of body composition presurgery and at day 63 postsurgery in the chow (A–C) and HFD (D–F) groups. Percent change in body fat in A and D show that the gain in body fat was significantly lower for both VSG and PR than for sham and DR in both chow and HFD groups, respectively. Body fat gain was similar in VSG and PR in the chow group, while significantly higher in PR, as compared with VSG in the HFD group. Absolute body fat presurgery and day 63 post-surgery are shown in chow (B) and HFD groups (E), respectively. Although there was a main effect of time, such that lean mass increased over time, there were no statistical differences in lean mass either preoperatively or postoperatively between surgeries in both chow (C) and HFD (F) groups. P < 0.05. Letters above bars that differ indicate a significant difference.
Fig. 5.
Fig. 5.
A: energy intake and fat absorption after surgery. Cumulative food intake of PR and VSG after the surgeries were significantly lower than that of DR in the chow group. B: cumulative food intake of VSG was significantly lower than that of sham, DR, and PR in the HFD group. Both VSG and PR exhibited significantly smaller and more frequent meals than DR and sham when ad libitum access to Ensure Plus was offered to HFD group (C and D). However, the daily intake was still significantly lower than that of sham and DR (E). Only VSG had a significantly lower preference to the HFD in the chow group (F). G: behenate diet test in the chow group indicated that the lipid absorption by the gastrointestinal tract in both VSG and PR was similar to that of sham. However, DR had higher lipid absorption rate than both VSG and PR. *P < 0.05. Significant difference is indicated by letters that differ above the bars.
Fig. 6.
Fig. 6.
Glucose and gastrointestinal hormones in response to surgery. Blood glucose values (A), change in GLP-1 levels from baseline at 10 min (B) and fasting ghrelin levels before a mixed-meal tolerance test (MMT) in the HFD rats (6C). Blood glucose values of DR, PR, and VSG were significantly lower than those of sham at 60 min. DR and PR blood glucose values were significantly lower at 30 min. Fasting ghrelin levels were significantly lower in VSG, as compared with DR, PR, and sham. GLP-1 secretion matched the gastric emptying rate (GER) for the four groups. Different letters indicate statistical significance, P < 0.05. *Significantly different vs. sham, P < 0.05.
Fig. 7.
Fig. 7.
Gastric emptying rate after surgery. Liquid nutrient gastric emptying using the acetaminophen test is depicted for the chow group (A), for the HFD group (B) and the third cohort (E). C: solid gastric emptying, as assessed by analyzing the percent of food remaining in the stomach 2 h after feeding in the chow group. D: analysis is given of planar gamma imaging after rats consumed ad libitum 99mTc sulfur colloid-labeled HF diet to analyze solid gastric emptying in the HFD group. Solid and liquid GER were the highest in VSG, as compared with sham and DR in both HFD and chow groups. GER in PR was significantly lower than in VSG but higher than in both sham and DR except for the liquid GER assessment in the chow group, where it was as high as in VSG. GER was significantly higher in VSG as compared with sham in the third cohort soon (2 wk) after the surgery. Different letters indicate statistical significance, P < 0.05. *Significantly different vs. sham, P < 0.05. $Significantly different vs. DR, P < 0.05. #Significantly different vs. PR, P < 0.05.

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