GS. Changes in one-carbon metabolism after duodenal-jejunal bypass surgery. Am J Physiol Endocrinol Metab 310: E624 -E632, 2016. First published January 19, 2016 doi:10.1152/ajpendo.00260.2015.-Bariatric surgery alleviates obesity and ameliorates glucose tolerance. Using metabolomic and proteomic profiles, we evaluated metabolic changes in serum and liver tissue after duodenal-jejunal bypass (DJB) surgery in rats fed a normal chow diet. We found that the levels of vitamin B 12 in the sera of DJB rates were decreased. In the liver of DJB rats, betaine-homocysteine S-methyltransferase levels were decreased, whereas serine, cystathionine, cysteine, glutathione, cystathionine -synthase, glutathione S-transferase, and aldehyde dehydrogenase levels were increased. These results suggested that DJB surgery enhanced trans-sulfuration and its consecutive reactions such as detoxification and the scavenging activities of reactive oxygen species. In addition, DJB rats showed higher levels of purine metabolites such as ATP, ADP, AMP, and inosine monophosphate. Decreased guanine deaminase, as well as lower levels of hypoxanthine, indicated that DJB surgery limited the purine degradation process. In particular, the AMP/ATP ratio and phosphorylation of AMP-activated protein kinase increased after DJB surgery, which led to enhanced energy production and increased catabolic pathway activity, such as fatty acid oxidation and glucose transport. This study shows that bariatric surgery altered transsulfuration and purine metabolism in the liver. Characterization of these mechanisms increases our understanding of the benefits of bariatric surgery. gastric bypass surgery; metabolomics; proteomics; metabolism DIABETES AFFECTS ALMOST 10% of the general population and is a leading cause of disability, morbidity, and mortality (15). Although glycemic control and risk factor management have improved, the prevalence of diabetes is still increasing (8, 9). Furthermore, current drug-based therapies for diabetes rarely lead to remission. Thus, there is an urgent need for new therapeutic options.Bariatric surgery provides a reliable treatment that results in substantial and sustained weight loss in morbidly obese patients and provides a substantial improvement in cases of type 2 diabetes mellitus (T2DM) (5, 6). Bariatric surgery is significantly better than intensive medical therapy for the glycemic control of T2DM at 1-2 years (10,13,24,38). However, the mechanism by which bariatric surgery results in the remission of T2DM remains unclear. Moreover, given that the initial body mass index and postoperative weight loss values are poor predictors of the efficacy of bariatric surgery in patients with diabetes and metabolic syndrome (27, 41), the improvement in glycemia after bariatric surgery is not simply a consequence of sustained weight loss. Therefore, understanding the underlying mechanism of bariatric surgery with respect to the resolution of T2DM is important for the development of more effective and less invasive T2DM therapeutic strategie...