(OR24-02-23) Effect of Gastric Bypass on Intestinal Adaptations and Dietary Protein Bioavailability in Rats

Objectives: Roux-en-Y Gastric Bypass (RYGB) has often been associated with protein deficiency but was not ascribed to protein malabsorption. We hypothesized that dietary amino acids (AA) are more sequestered by the small intestine mucosa due to adaptative hypertrophy after RYGB. Our study aimed to assess intestinal adaptations and dietary protein bioavailability after RYGB in rats, at different times after post-surgery recovery.

Methods: Diet-induced obese Wistar rats received RYGB surgery. The control group was composed of pair-fed Sham-operated rats. Rats were fed a test meal including ¹⁵N-labeled protein, 1 month (RYGB: n=9, Sham: n=8) or 3 months (RYGB: n=7, Sham: n= 8) after surgery and were euthanized 6h later. Protein digestibility, dietary nitrogen (N) sequestration in organs, and dietary N lost through urea were assessed by determination of ¹⁵N recovery in digesta, organs, and urinary/plasma urea respectively. Intestinal morphometry was studied. Results are presented as mean ± sem.

Results: Protein digestibility was similar in Sham and RYGB rats at both times after recovery and was 94.2±0.3%. The small intestine was hypertrophied in RYGB rats 1 month after surgery, weighing 9.1±0.2g vs 7.0±0.3g for Sham rats (P=0.003). Moreover, villus height and crypt depth were higher in the alimentary limb and ileum than in corresponding segments in Sham rats. In the gastrointestinal tract, dietary N sequestration differed only in the ileum mucosa. It was higher in RYGB than in Sham rats 1 month after surgery (respectively 0.48±0.2% vs 0.3±0.09% of N ingested, P=0.03). Dietary N recovered in liver, muscle, and skin was lower in RYGB than in Sham rats 1 month after surgery, this effect decreased at 3 months. The proportion of dietary N recovered in urinary and plasma urea was higher in RYGB than in Sham rats at both times, leading to an increase in total deamination (respectively 13.2±0.9% vs 10.1±0.5% of N ingested, P< 0.01).

Conclusions: This study confirms that RYGB did not affect protein digestibility but induced intestinal mucosa hypertrophy. However, the increase of dietary AA sequestration was only confirmed in the ileum. The transitory decrease of dietary AA recovered in other organs was associated with a marked increase in postprandial deamination after RYGB, an effect whose mechanisms warrant further studies.

Funding Sources: This study was funded by the doctoral school ABIES.