Glucose metabolism in a rat model of gastric by-pass surgery

Objectives The effects of Roux-en-Y Gastric Bypass (RYGB) point to the important role of the GI tract in regulation of energy balance and metabolism. RYGB is the most effective treatment for severe obesity. In this study, we propose that the improvement in glucose metabolism that takes place after RYGB can be accounted for by metabolic changes that occur in the anatomically reorganized intestine. Furthermore, we propose that the effectiveness of RYGB proves that the manipulation of intestinal metabolism provides the unique opportunity to regulate whole-body metabolism and treat obesity, diabetes and other metabolic disorders.

Methods Obese CD-1 rats weighing ~ 1 kg were operated with the RYGB procedure. Briefly, the stomach is divided to create a small gastric pouch. Food travels from the esophagus to a gastric pouch and then to the jejunum directly bypassing the stomach the duodenum and part of the proximal jejunum. ~ 5 weeks after surgery the operated animals and shams were fasted overnight, injected with 1-2 mCi of FDG and 60 min later imaged by μPET.

Results There was intense FDG uptake in the Roux limb but no detectable FDG in the jejunum of sham rats. To confirm the results of the PET/CT and to quantify the differences in the glucose uptake across different regions of the intestine and the relative contribution of each tissue to the overall glucose uptake, we measured biodistribution in other sets of rats. The results of this analysis were similar to PET/CT which demonstrated a 2-fold increase in the glucose uptake of the Roux limb. Thus, glucose uptake increases primarily in the Roux limb, but also in all intestinal segments of the GI tract along nutrient flow, suggesting that luminal factors may be responsible for this effect.

Conclusions FDG PET can serve as a biomarker for monitoring experimental gastric by-pass surgery with an eye to refining the procedures.