An observational study in Obesity (BMI>30), Obesity (BMI > 35) and Insulin Resistance, sponsored by Istanbul University. Completed. Open to participants aged 18 Years to 65 Years. Per ClinicalTrials.gov, last updated 2026-08-19.
Sponsored by Istanbul University · Observational
This retrospective observational cohort study examined serum fatty acid-binding protein 4 (FABP4) dynamics in 28 adults who underwent Roux-en-Y gastric bypass (RYGB), followed at baseline, 3 months, and 6 months. Anthropometric, metabolic, and inflammatory parameters were assessed alongside FABP4, fasting GLP-1, and PYY. Patients were classified as FABP4 responders (decrease from baseline to 6 months) or rebound/non-responders. The study investigated whether FABP4 trajectory after RYGB is associated with the magnitude of weight loss, systemic inflammation, and fasting incretin change.
Sixteen of the 28 participants had previously been enrolled in the control (probiotic-only, non-prebiotic) arm of a completed, registered randomized trial of pre-/probiotic supplementation after RYGB at the same institution (ClinicalTrials.gov Identifier: NCT03517345); these participants received no prebiotic intervention. The remaining 12 participants underwent RYGB by the same surgeon during a comparable period and were not enrolled in that trial. Blood samples from both subgroups had originally been collected and stored at -80°C as part of their respective prospective clinical follow-up. FABP4 concentrations were subsequently measured in these banked, single freeze-thaw samples using a commercial ELISA assay, blinded to patients' weight-loss and inflammatory outcomes, and merged with the anthropometric and biochemical data collected at the corresponding original visits. Because FABP4 assay and the present statistical analysis were performed after clinical follow-up had already been completed for both subgroups, this study is registered retrospectively.
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This study's enrollment of 28 is below the median of 114 across 2,154 observational studies indexed under Obesity.
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Adults undergoing Roux-en-Y gastric bypass (RYGB) performed by a single surgeon at Istanbul University, Istanbul Faculty of Medicine. The cohort comprised 16 patients previously enrolled in the control (probiotic-only) arm of a completed randomized trial (NCT03517345) and 12 additional consecutive patients undergoing RYGB by the same surgeon during a comparable period who were not enrolled in that trial. Patients using GLP-1 receptor agonists or insulin at any study time point were excluded.
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Exclusion Criteria:
Description: Patients with a decrease in serum FABP4 from baseline to 6 months after Roux-en-Y gastric bypass (n=9)
Description: Patients with no decrease or an increase in serum FABP4 from baseline to 6 months after Roux-en-Y gastric bypass (n=18)
Measure: Change in serum FABP4 level from baseline to 6 months after RYGB
Description: FABP4 measured by ELISA; patients classified as responders (decrease) vs. rebound/non-responders (no decrease or increase)
Time frame: Time Frame: Baseline, 3 months, 6 months
Change in BMI from baseline to 3 and 6 months
Change in BMI from baseline to 3 and 6 months
Time frame: Baseline, 3 months, 6 months
Change in body weight from baseline to 3 and 6 months
Change in body weight from baseline to 3 and 6 months
Time frame: Baseline, 3 months, 6 months
Change in fat mass (bioelectrical impedance) from baseline to 3 and 6 months
Change in fat mass and fat-free mass (bioelectrical impedance) from baseline to 3 and 6 months
Time frame: Baseline, 3 months, 6 months
Change in fat-free mass (bioelectrical impedance) from baseline to 3 and 6 months
Change in fat mass and fat-free mass (bioelectrical impedance) from baseline to 3 and 6 months
Time frame: Baseline, 3 months, 6 months
Change in HOMA-IR from baseline to 3 and 6 months
Change in HOMA-IR from baseline to 3 and 6 months
Time frame: Baseline, 3 months, 6 months
Change in IL-6 from baseline to 3 and 6 months
Change in hsCRP and IL-6 from baseline to 3 and 6 months
Time frame: Baseline, 3 months, 6 months
Change in hsCRP from baseline to 3 and 6 months
Change in hsCRP and IL-6 from baseline to 3 and 6 months
Time frame: Baseline, 3 months, 6 months
Change in fasting GLP-1 from baseline to 3 and 6 months
Change in fasting GLP-1 and PYY from baseline to 3 and 6 months
Time frame: Baseline, 3 months, 6 months
Change in fasting PYY from baseline to 3 and 6 months
Change in fasting GLP-1 and PYY from baseline to 3 and 6 months
Time frame: Baseline, 3 months, 6 months
Baseline-Adjusted 6-Month Change in Body Mass Index (BMI) by FABP4 Response Group
6-month change in BMI (kg/m²) was compared between FABP4 responder and rebound (non-responder) groups using an ANCOVA model adjusted for baseline (preoperative) serum FABP4 concentration (log-transformed). FABP4 response group was defined by the direction of change in serum FABP4, measured by enzyme-linked immunosorbent assay (ELISA), from baseline to 6 months after Roux-en-Y gastric bypass.
Time frame: Baseline, 3 months, 6 months
Odds Ratios for Predictors of 6-Month FABP4 Rebound: Early (0-3-Month) BMI Change, Age, and Sex
Odds ratios (OR) with 95% confidence intervals were estimated using a multivariable logistic regression model to identify predictors of FABP4 rebound status at 6 months after Roux-en-Y gastric bypass. Covariates included early (0-3-month) percentage change in body mass index (BMI), age (years), and sex (male/female). FABP4 rebound was defined as an increase in serum FABP4 concentration, measured by enzyme-linked immunosorbent assay (ELISA), from baseline to 6 months postoperatively.
Time frame: Baseline, 3 months, 6 months
No study locations are listed for this record.
Plan to share: Yes — Types of Supporting Information: Study Protocol Statistical Analysis Plan Analytic Code IPD Sharing Time Frame: Beginning 12 months and ending 36 months following publication of the primary manuscript. IPD Sharing Access Criteria: De-identified individual participant data will be made available to researchers who provide a methodologically sound proposal, following review and approval by the corresponding author and the Istanbul University Istanbul Faculty of Medicine Clinical Research Ethics Committee, and subject to a signed data access agreement. Requests should be directed to the corresponding author.
Supporting information: Study protocol, Statistical analysis plan, Analytic code
Time frame: Beginning 12 months and ending 36 months after publication of the primary manuscript, upon reasonable request to the corresponding author.
Access criteria: De-identified individual participant data, the study protocol, statistical analysis plan, and analytic code will be made available to qualified researchers who submit a methodologically sound proposal to the corresponding author. Requests will be reviewed for scientific merit and data protection compliance and require approval from the Istanbul University Istanbul Faculty of Medicine Clinical Research Ethics Committee and a signed data access/use agreement prior to release, in order to protect participant confidentiality given the modest single-center cohort size (n=27).
No publications or documents are linked to this record.
This study is completed, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.
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