Heathly Volunteers

The goal of this clinical trial is to learn whether a single dose of XBD173, a medicine that binds to a protein called the 18 kiloDalton Translocator Protein (TSPO), affects how the body processes glucose in healthy volunteers aged 18 to 75 years. The main questions it aims to answer are: * Does a single dose of XBD173 change fasting blood glucose levels compared with placebo? * Does a single dose of XBD173 change blood glucose levels after participants drink a glucose solution compared with placebo? Researchers will compare XBD173 with a placebo, which does not contain the active medicine, to see whether activating TSPO affects glucose metabolism in the fasting state and after a glucose drink. Participants will: * Attend a screening visit to confirm eligibility, including a medical history, physical examination and blood tests. * Attend four study visits after fasting overnight: two visits involving a glucose drink and two visits without a glucose drink. * Receive a single oral dose of XBD173 at some visits and placebo at other visits. The order will be randomised, and neither participants nor the study team conducting the assessments will know which treatment is given during each visit. * Have repeated blood samples taken through a cannula to measure glucose, insulin and other markers related to metabolism and inflammation. * Have resting energy use measured by breathing under a transparent canopy connected to a standard metabolic measurement device. * Have blood pressure, heart rate, height and weight measured. * Undergo measurement of blood vessel function using a cuff.

The expected outcome of this study is that continuous 8-week supplementation with the PI-YSP-0111 prebiotic formulation will exert beneficial effects on gut microbiota modulation and liver health.