Roux-en-Y Gastric bypass (RYGB) promotes improvement in type 2 diabetes (T2D) shortly after surgery, with metabolic mechanisms yet to be elucidated. This study aimed to investigate the relationship between food intake, tryptophan metabolism, and gut microbiota on the glycemic control of obese T2D women after RYGB surgery. Twenty T2D women who underwent RYGB were evaluated before and three months after surgery. Food intake data were obtained by a seven-day food record and a food frequency questionnaire. Tryptophan metabolites were determined by untargeted metabolomic analysis, and the gut microbiota was determined by 16S rRNA sequencing. The glycemic outcomes were fasting blood glucose, HbA1C, HOMA-IR, and HOMA-beta. Linear regression models were applied to assess the associations between the changes in food intake, tryptophan metabolism, and gut microbiota on glycemic control after RYGB. All variables changed after RYGB (p < 0.05), except for tryptophan intake. Jointly, the variation in red meat intake, plasma indole-3-acetate, and Dorea longicatena was associated with postoperative HOMA-IR {R² 0.80, R² adj 0.74; p < 0.01}. Red meat intake decreased three months after bariatric surgery while indole-3-acetate and Dorea longicatena increased in the same period. These combined variables were associated with better insulin resistance in T2D women after RYGB.

Key words: Dental Pulp; Culture Media; Glucose; Glutamine; Regenerative Medicine

Roux-en-Y gastric bypass (RYGB) is one of the most performed bariatric surgical techniques. However, RYGB commonly results, as side effects, in nutritional deficiencies. This study aimed to examine changes in the expression of vitamin A pathway encoding genes in the gastrointestinal tract (GI) and to evaluate the potential mechanisms associated with hypovitaminosis A after RYGB. Intestinal biopsies were obtained through double-balloon endoscopy in 20 women with obesity (age 46.9±6.2 years; body mass index [BMI] 46.5±5.3 kg/m² [mean±SD]) before and three months after RYGB (BMI, 38.2±4.2 kg/m²). Intestinal mucosal gene microarray analyses were performed in samples using a Human GeneChip 1.0 ST array (Affymetrix). Vitamin A intake was assessed from 7-day food records and serum retinol levels were evaluated by electrochemiluminescence immunoassay. Our results showed the following genes with significant downregulation (p≤0.05): LIPF (−0.60), NPC1L1 (−0.71), BCO1 (−0.45), and RBP4 (−0.13) in the duodenum; CD36 (−0.33), and ISX (−0.43) in the jejunum and BCO1 (−0.29) in the ileum. No significant changes in vitamin A intake were found (784±694 retinol equivalents [RE] pre-operative vs. 809±753 RE post-operative [mean±SD]). Although patients were routinely supplemented with 3500 international units IU/day (equivalent to 1050 μg RE/day) of oral retinol palmitate, serum concentrations were lower in the post-operative when compared to pre-operative period (0.35±0.14 μg/L vs. 0.52±0.33 μg/L, respectively – P=0.07), both within the normal range. After RYGB, the simultaneous change in expression of GI genes, may impair carotenoid metabolism in the enterocytes, formation of nascent chylomicrons and transport of retinol, resulting in lower availability of vitamin A.

Although sphingolipids are key players in lipotoxicity and metabolic diseases, their response to bariatric surgery and their relation to metabolic improvement remain unclear. This pilot study investigated plasma sphingolipid remodeling after Roux‐en‐Y gastric bypass (RYGB) and its associations with clinical and biochemical markers of postoperative metabolic improvement in women with obesity and type 2 diabetes (T2DM). Plasma samples, anthropometric, body composition, and biochemical data (glucose, HbA1c, insulin, C‐peptide, and lipid profile) were collected from 30 participants before and 3 months after surgery. T2DM remission was defined according to ADA 2021 criteria. Plasma sphingolipids were identified using untargeted metabolomics, which involved ultra‐performance liquid chromatography coupled with mass spectrometry. Univariate and multivariate analyses were performed using Jamovi (version 2.2.5) and MetaboAnalyst (versions 5.0 and 6.0). RYGB led to reductions in body weight and anthropometric measures, with improved body composition. Patients demonstrated glycemic improvement, with 18 achieving remission of T2DM. The lipid profile also improved, with a decline in total cholesterol driven by reductions in pro‐atherogenic fractions. Among 32 plasma sphingolipids identified, 21 changed significantly after surgery. Sphingolipids showed strong‐to‐robust correlations with the lipid profile, particularly SM(d18:1/20:0) and SM(d18:1/22:0) with total cholesterol and LDL‐c after surgery, but moderate and poor correlations with body composition, and glycemic markers, respectively. Plasma sphingolipids underwent significant remodeling after RYGB, with strong associations with plasma cholesterol, particularly with SM(d18:1/20:0) and SM(d18:1/22:0). These findings suggest that specific sphingolipid species may contribute to or reflect plasma lipid adaptations to surgery and warrant further investigation as potential metabolic biomarkers. Trial Registration: This protocol is part of a broader umbrella study registered at www.clinicaltrials.gov under the identifier NCT01251016

Roux‐en‐Y gastric bypass (RYGB) surgery is known to improve lipid profiles in individuals with obesity, but the degree of improvement varies. Emerging evidence suggests a role for sphingolipids in modulating cholesterol metabolism. This study investigated the relationship between plasma sphingolipid changes and cholesterol improvements in women with obesity and Type 2 diabetes mellitus (T2DM) following RYGB. Patients from the SURMetaGIT study were evaluated before and 3 months after surgery. Biochemical and sphingolipid analyses, anthropometric measures, and body composition were assessed. A nonhierarchical cluster analysis assessed distinct phenotypes in response to cholesterol after surgery. The p value from multiple comparison tests was adjusted using the false discovery rate (FDR) method. A metabolite fold change [log ₂ (postoperative mean/preoperative mean)] of 1.2 and an adjusted p value < 5% were considered statistically significant. A linear regression model was used to investigate the relationship between sphingolipids and cholesterol levels. Finally, a binary logistic regression model was developed to identify the predictive value of specific discriminative sphingolipids in the lipid improvement after RYGB. Distinct sphingolipid remodeling patterns were observed, with specific sphingolipids, including Cer(d18:1/24:0), SM(d18:1/22:0), and SM(d18:1/24:0), presenting a strong positive correlation with cholesterol levels, independent of weight loss and T2DM remission. The binary logistic regression showed preoperative Cer(d18:1/24:0) could be the strongest candidate predictor of plasma lipid improvement after surgery (accuracy of 78%; AUC 0.87). These findings suggest that specific sphingolipids, notably preoperative Cer(d18:1/24:0), seemed to have a potential role in predicting cholesterol improvement after RYGB. External validation in independent cohorts is warranted before clinical applicability can be established. Trial Registration: ClinicalTrials.gov identifier: NCT01251016