Transcutaneous Auricular Vagus Nerve Stimulation for Poor Weight-Loss Response to Incretin Receptor Agonists

This is a prospective, single-center, randomized, participant-blinded, sham-controlled, parallel-group study conducted at the Department of Endocrinology, Nanjing Drum Tower Hospital. The study will enroll 24 overweight or obese participants with a suboptimal weight-loss response, defined as a body weight reduction of no more than 10% after at least 12 weeks of tirzepatide treatment. Eligible participants will be randomized in a 1:1 ratio to the taVNS plus tirzepatide 5 mg group or the sham stimulation plus tirzepatide 5 mg group for 12 weeks. Before and after intervention, all participants will undergo standardized assessments, including lifestyle questionnaires, anthropometric measurements, body composition analysis, autonomic function evaluation, laboratory testing, and assessment of hepatic steatosis and fibrosis. Autonomic function assessment will include heart rate variability, cardiovascular autonomic reflex tests, sudomotor function, and brain MRI. Liver-related assessments will include FibroTouch and liver MRI. During follow-up, body weight will be monitored weekly by telephone or WeChat, waist circumference, hip circumference, and body composition will be reassessed every 4 weeks, and device use will be monitored through an app to ensure adherence and protocol consistency. The primary endpoint is the between-group difference in percent change in body weight from baseline to week 12. Secondary endpoints include changes in body composition and fat distribution, glucose- and lipid-related metabolic parameters, liver function and hepatic steatosis/fibrosis-related parameters, and autonomic function measures. Exploratory analyses will evaluate changes in brain imaging phenotypes after 12 weeks of intervention.