Background: Gastric bypass surgery is a fast-growing modality in the treatment of morbid obesity and is accepted as one of the best therapeutic options with good results. Although gastric bypass surgery predisposes patients to nutrient deficiencies from malabsorption, the specific pathways and mechanisms of this process are still largely unknown. This study is the first to examine the effects of gastric bypass on absorption of the amino acid glutamine in rat small intestine.
Methods: Twelve week-old male Zucker rats were randomized to control and treatment groups. Control group rats received a sham operation and treatment group rats received a Roux-en-Y gastric bypass surgery. Rats were pair-fed post-operatively and daily weights were recorded. Rats were sacrificed at approximately 1.5 months after surgery and the small intestine was harvested from both control and treatment groups. Levels of glutamine transporter activity, mRNA and protein were measured in the biliopancreatic limb, roux limb and common limb using H-3 glutamine, northern and western blot techniques, respectively. Data were mean ± SE and analyzed with t-test with p<0.05.
Results: Gastric bypass surgery resulted in a significant weight loss averaging 200 grams in the bypass group compared with the control group (p<0.01). Gastric bypass surgery resulted in an increase of glutamine transport activity in the biliopancreatic limb (3.8-fold) and in the roux limb (1.4-fold) and a 1.7-fold decrease of glutamine transport activity in the common limb. The predominant glutamine transporter B0AT1 protein levels were 6-fold and 10-fold higher in the biliopancreatic and roux limbs, respectively and 5-fold lower in the common limb in the bypass group compared with the control group. B0AT1 mRNA levels were 1.5-fold higher in the biliopancreatic limb and 1.6-fold higher in the roux limb in the bypass group compared with the control group. There was no difference in B0AT1 mRNA levels in the common limb.
Conclusion: Gastric bypass surgery selectively alters absorption of the amino acid glutamine in various segments of the small intestine. These findings enhance our understanding of regulation of intestinal nutrient absorption and may help guide post-operative nutritional management following gastric bypass surgery.