Adaptation Process of the Transposed Ileum during Early Postoperative Period after Ileal Transposition

The intestine undergoes diverse changes to adapt the altered environment after bariatric surgery, which have various implications in the molecular mechanisms of bariatric surgery. Ileal transposition (IT) is an experimental surgery to investigate the role of the distal ileum in bariatric surgeries. To systematically investigate the gut adaptation process in IT, we performed a gene expression profiling of the transposed ileum compared to the ileum in situ at different postoperative time points. Sprague-Dawley rats fed a chow diet underwent IT or sham surgery. In IT, 10 cm of the distal ileal segment was transposed distal to the Treitz ligament. In sham surgery, the intestine was resected at the same anatomical location and anastomosed in situ. Either 1 or 4 weeks after surgery, total RNA was extracted from the ileal tissue and used for microarray analysis. Principal component analysis showed that the difference between 1 and 4 weeks was the largest. The difference between IT and sham groups were larger at 4 weeks than 1 week. A total of 1792 differentially expressed genes (DEGs) were identified including 659 and 1133 DEGs at 1 and 4 weeks, respectively. Interestingly, only 45 and 24 DEGs were commonly up- or down-regulated at the two time points, remaining 96.1% of DEGs were uniquely regulated at either time points. The network analysis showed that the affected biologic processes were related to structural (cell adhesion and immune responses) and functional (glucose and fatty acid metabolism) adaptations. Up-regulated extracellular proteins and their interacting integrins at 1 week, and cytokines, chemokines and their receptors at 4 weeks were interlinked. In glucose metabolism, up-regulation of GLUT2, HK3 and down-regulation of G6PC suggested enhanced glucose uptake and glycolysis. Collectively, our results suggest that the adaptation process of the transposed ileum dynamically evolve during early postoperative period incorporating structural and functional changes.