Roux‐en‐Y gastric bypass decreases endotoxemia and inflammatory stress in association with improvements in gut permeability in obese diabetic rats

Abstract Background Postoperative modulation of the gut microbiome has been suggested to contribute to the metabolic benefits after metabolic surgery, but the mechanisms underlying these metabolic benefits remain unknown. Previously, we reported that Roux‐en‐Y gastric bypass (RYGB) surgery in Zucker diabetic fatty (ZDF) rats increased the abundance of Proteobacteria and Gammaproteobacteria. However, theoretically, these Gram‐negative bacteria may elevate lipopolysaccharide (LPS) levels. Therefore, in this study we further investigated the potential mechanisms by which RYGB improves glucose homeostasis, endotoxemia, and inflammatory stress in ZDF rats. Methods Rats were divided into three groups: (a) an RYGB group (RY); (b) a sham‐operated group pair‐fed with the RY group; and (c) a sham‐operated group fed ad libitum. Changes in LPS, cytokine levels, intestinal permeability (evaluated using the fluorescein isothiocyanate‐dextran method), and intestinal epithelial tight junction proteins zona occludins (ZO)‐1, occludin, and claudin‐1 were assessed 10 weeks postoperatively. Results Rats that underwent RYGB exhibited sustained weight loss and reduced glucose, as well as lower cytokine and LPS concentrations, than rats in the control groups. In the colonic epithelium, ZO1 and claudin‐1 ( Cldn1 ) mRNA levels were higher in the RY than control groups. Intestinal permeability declined in the RY group and was positively correlated with LPS levels and negatively correlated with ZO‐1, occludin, and claudin‐1 expression. Conclusions The results demonstrate that RYGB can reduce the extent of endotoxemia and inflammation, which is associated with improved tight junction integrity and intestinal barrier strength. These effects may explain why a low level of inflammation is maintained after RYGB and the postoperative increase in Gram‐negative bacteria.