FABP4 Response After Roux-en-Y Gastric Bypass

Heterogeneous Fatty Acid-Binding Protein 4 (FABP4) Responses After Roux-en-Y Gastric Bypass: A Retrospective Observational Cohort Study of Adipokine Remodeling Dissociated From Weight Loss, Inflammation, and Incretin Dynamics

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.

Inclusion Criteria:

• Adults who underwent Roux-en-Y gastric bypass (RYGB), performed by a single surgeon
• Completed baseline, 3-month, and 6-month clinical and anthropometric assessments

Exclusion Criteria:

• Use of GLP-1 receptor agonists at any study time point
• Use of insulin at any study time point
• Missing 6-month FABP4 measurement (excluded from FABP4-based longitudinal/group analyses; n=1)