Effect of Gastric Bypass on Dietary Protein Digestibility and Dietary Nitrogen Sequestration in the Splanchnic Bed in Rats

Abstract Objectives Roux-en-Y Gastric Bypass (RYGB) decreases the stomach size and bypasses a part of the small intestine. RYGB has been often associated with protein malnutrition but in the light of previous studies, this was not ascribed to protein malabsorption. We hypothesized that dietary amino acids are more sequestered by the small intestine mucosa due to adaptative hypertrophy after RYGB. Our study aimed to quantify the sequestration of dietary nitrogen (N) in the small intestine after RYGB at different times of the post-surgery recovery. Methods Diet-induced obese Wistar rats were operated for RYGB. The control group was composed of pair-fed sham-operated rats. One month (RYGB: n = 9, Sham: n = 8) or three months (RYGB: n = 7, Sham: n = 8) after surgery, rats were fed a test meal including 15N-labeled protein. Protein digestibility and dietary N sequestration in the intestine were assessed by determination of 15N recovery in the digesta and gastrointestinal tract (GIT) tissues 6 h after the meal. Results One month after surgery, protein digestibility in Sham and RYGB rats was 94.0 ± 0.8% and 94.2 ± 1.8% (NS), respectively. Digestibility was similar 3 months after surgery, whatever the group. The GIT was hypertrophied in RYGB after 1 month, an effect that disappeared after 3 months. Dietary N sequestration in the splanchnic bed differed depending on the segment. In the stomach wall as well as the duodenum + jejunum mucosa, N retention was lower in RYGB than in Sham at 1 month, this difference being aggravated at 3 months. In contrast, in the ileum mucosa, there was more N in RYGB than in Sham at 1 month (0.48 ± 0.18% vs 0.3 ± 0.09% of ingested N respectively), these values being similar at 3 months. In the caecum, dietary N was higher in RYGB at 1 month compared to Sham but lower in the colon. No differences between groups were observed in these two segments at 3 months. Conclusions RYGB did not improved protein digestibility, in contrast to the findings of our previous study. Our hypothesis of a higher sequestration in the intestinal wall was confirmed in the ileum and colon only, an effect that tended to be attenuated over time. Funding Sources This study was funded by the doctoral school ABIES.