Comparison of the Effects of Roux-en-Y Gastric Bypass and Ileal Transposition Surgeries on Food Intake, Body Weight, and Circulating Peptide YY Concentrations in Rats

Roux-en-Y gastric bypass (RYGB) surgery is one of the most effective treatments for obesity producing long-term weight loss. The anorexia and weight loss from RYGB could be due to gastric restriction, malabsorption, enhanced lower gut stimulation, increased energy expenditure, and/or other metabolic adaptations. In ileal transposition (IT) surgery, a segment of the ileum is transposed to the upper jejunum with no gastric restriction or malabsorption. Our objective is to compare the effects of RYGB and IT surgeries on food intake, body weight, and plasma concentrations of the anorexigenic lower gut hormone Peptide YY (PYY) in rats. Adult male Sprague-Dawley rats were subjected to either RYGB (n = 9), IT (n = 9) or sham surgeries (n = 16). A subset of sham animals were either pair-fed to RYGB (n = 9) or ad lib fed (n = 7) on a highly palatable mixed nutrient liquid food (Ensure). Food intake, body weight and plasma PYY concentrations were measured. The data demonstrate that (1) RYGB produces a sustained reduction in food intake and weight gain, (2) the anorexic effects of IT are relatively transient lasting for 5 weeks, (3) the reduction in weight gain resulting from IT is similar to that of animals pair-fed to RYGB, and (4) RYGB and IT surgeries are associated with elevated postprandial plasma PYY concentrations. We demonstrate in our rat models that RYGB surgery produces a greater reduction in food intake and weight gain than IT surgery, and that both surgeries are associated with enhanced plasma concentrations of Peptide YY.