Short-term Weight Trajectory of Severely Obese Individuals With and Without Pathogenic Satiety-Regulation Melanocortin 3/4 Receptor (MC3/4R) Mutations From a Multi-ethnic Asian Large Bariatric Surgery Program

The melanocortin (3 or 4) receptor (MC3/4R) is involved in regulating satiety and body weight. Therefore, pathogenic mutation in MC3/4R is associated with severe obesity, for which bariatric surgery is one of the treatment options. However, there is limited data on whether individuals with MC3/4R mutation will have differential weight response to surgery, especially among the Asian populations—the epi-center of the evolving global obesity epidemic. From our large prospective Obesity—Metabolism & Intervention Cohort Study (OMICS; N = 654, recruited between 2007 and 2022), 5 individuals with pathogenic MC3/4R mutations (“case”) were identified using candidate-genes panel next-generation sequencing (Illumina iSeq). These subjects were carefully propensity score–matched (baseline body mass index [BMI], age, sex, ethnicity, proportion with diabetes, type of bariatric surgery) in a 1:4 ratio to other controls. We performed linear mixed model analysis (for repeated measurements) to compare their longitudinal weight trajectories (percentage total weight loss, %TWL) over 12 months. The 5 cases with MC3/4R mutations were 48 ± 11 years, BMI 40.8 ± 11.2 kg/m(2), 60% with diabetes, and all males. Their weight at baseline (pre-op), and 6 months and 12 months after surgery were 120 ± 38, 100 ± 31, and 101 ± 30 kg, respectively. Compared with propensity score–matched controls (N = 20), linear mixed model analysis suggested no difference in surgically induced %TWL (β coefficient = −5.8 ± 3.7, P = .13) over 12 months between the groups. Therefore, we conclude that rare pathogenic MC3/4R mutations do not significantly modify weight change (%TWL) in response to bariatric surgery.