Elucidating Mechanisms That Underlie Symptomatology of Functional Dyspepsia Using Novel Imaging Technique of SPECT/CT, MRI, High-Resolution Manometry and Biomarkers; and the Therapeutic Validation of Elucidated Mechanisms Using Neuromodulator Compounds

The goal of this study is to investigate the mechanisms of impaired gastric accommodation and emptying, dysfunctional duodenum, and micro-inflammation using novel imaging techniques of SPECT/CT, gastric emptying scintigraphy, MRI, high-resolution manometry, and inflammatory biomarkers, as well as to validate these mechanisms using a therapeutic trial of neuromodulator (mirtazapine) in functional dyspepsia (FD) and health. The main objective[s] it aims to answer are:

• to investigate impaired gastric accommodation through SPECT/CT imaging and high-resolution manometry findings of the stomach fundus.
• to investigate impaired gastric emptying through gastric emptying scintigraphy
• to investigate for a dysfunctional duodenum through MRI imaging of the duodenum.
• to investigate micro-inflammation through SPECT/CT standard uptake value (SUV), inflammatory biomarkers (eosinophils, mast cells, IL-6, IL-10) and mucosal barrier marker (E-cadherin).
• to investigate if a therapeutic trial of a neuromodulator agent, mirtazapine, ameliorates symptoms of FD through improvement in impaired gastric accommodation.

For objectives 1-4, FD patients and healthy volunteers will be consecutively recruited, and all will undergo SPECT/CT, MRI, high-resolution manometry and biomarkers, and data acquired from these tests will be analyzed. For objective 5, the enrolled participants who did all baseline tests/markers are given mirtazapine for four weeks, and all tests/markers, except biomarkers and MRI, are repeated at the end of the trial