Abstract
BACKGROUND: The fat mass and obesity-associated (FTO) and melanocortin-4 receptor (MC4R) genes have been implicated in the pathophysiology of obesity. However, their regulatory behavior in human gastric tissue and association with postoperative weight loss following metabolic and bariatric surgery (MBS) remain unclear. METHODS: In this prospective case-control study, gastric tissue from 50 patients with obesity undergoing laparoscopic sleeve gastrectomy and 48 non-obese controls was analyzed for FTO and MC4R mRNA expression using quantitative PCR. Adjusted Inverse propensity score weighting (IPSW-adjusted) and age-/sex-adjusted linear regression were applied. Receiver operating characteristic (ROC) curves were used to evaluate discriminatory thresholds. Correlation with 12-month percent total weight loss (%TWL) was assessed. RESULTS: FTO expression was significantly upregulated (mean fold-change: 4.68, p < 0.001) and MC4R downregulated (mean fold-change: - 0.91, p < 0.001) in patients with obesity. ROC analysis identified thresholds of > 1.515 for FTO (AUC = 1.00) and < 0.525 for MC4R (AUC = 1.00), both with high sensitivity and specificity. No significant correlation was observed between gene expression and %TWL at 12-month follow-up. CONCLUSION: Gastric expression of FTO and MC4R accurately discriminates between individuals with and without obesity but does not predict postoperative weight loss outcomes after sleeve gastrectomy. These findings indicate diagnostic potential, whereas prognostic value remains unsubstantial.