Dietary Protein Bioavailability in Bariatric Surgery Rat Models

Abstract

IntroductionBariatric surgery is an efficient treatment of massive obesity but can trigger nutritional deficiencies, especially regarding vitamins and proteins. Protein wasting may be observed, but with large variations of prevalence. Additionally to an insufficient protein intake, protein malabsorption logically appears as a risk factor. However, there is little data on protein digestion after bariatric surgery. This study aimed to clarify the risk of protein malabsorption in two rat models of bariatric surgery, sleeve gastrectomy (SG) and Roux‐en‐Y gastric by‐pass (RYGB).MethodsRats were fed a high fat diet for 3 months. They underwent RYGB (n=9) or SG (n=7) surgeries. Each group was paired with a sham pair‐fed group (n=4/group). During 15 d post‐surgery, dietary intake, weight and body composition were measured. At day 15 post‐surgery, rats were given a test meal containing 15N labeled proteins and sacrificed 6 h after the meal. Non‐absorbed 15N labeled dietary protein was quantified 6 h after the test meal in gastrointestinal segments (stomach, duodenum, jejunum, ileum, caecum and colon) by elemental analyzer coupled to isotope ratio mass spectrometer. Small intestine morphology was studied by histology.Results3/9 rats and 7/7 rats survived to RYGB and SG, respectively. On d 15 post‐surgery, dietary intake was 49 % and 36 % decreased in RYGB and SG groups (P<0.001), respectively. Fat mass decreased by 32 % in both RYGB and SG groups and 21 % in sham pair‐fed groups (P=0.07). Lean mass loss ranged between 10 % in RYGB to 4 % in sham pair‐fed groups without any significant difference between groups. Hypoalbuminemia was observed in all groups. Non‐absorbed dietary nitrogen was similar between groups in small intestinal segments whereas it was higher in colon in RYGB compared to SG rats (2.8 ± 0.3 vs 1.1 ± 0.2 %, P=0.01). True protein digestibility was 93 ± 1.3 %, without any difference between groups. Histology revealed a hypertrophy of the jejunum mucosa after RYGB and SG and ileum mucosa after RYGB.ConclusionThis study did not show protein malabsorption after RYGB compared to SG or sham operated rats. Jejunum hypertrophy may have compensated the reduction of absorption area and preserved protein bioavailability. Further studies are needed to confirm this result.