Effects of Renally Excreted low-calorie Sweeteners On URinary gluCose Excretion and whole-body glucose homeostasis: A double-blind, randomised, placebo-controlled Trial in healthy and type 2 diabetes participants (RESOURCE-Trial).

Participants who pass the screening will be randomised according to a schedule determined by the Royal Adelaide Hospital Investigational Drugs Pharmacy to one of 3 intervention groups in a double-blind, parallel design. Each group will receive one of the following supplements (doses calculated based on acceptable daily intake (ADI) at 60 kg of body weight) in 3 divided doses to be taken in gelatin capsules with each meal for 2 weeks: (i) Ace-K (total dose 900 mg daily or 300 mg three times daily), (ii) sucralose (total dose 300 mg daily or 100 mg three times daily), or (iii) placebo (cellulose only) Only the designated pharmacists at the Royal Adelaide Hospital Investigational Drugs Pharmacy will dispense the study compounds. Each capsule will be packaged at the same weight by the addition of cellulose. Compliance with taking capsules will be reinforced by daily mobile phone messages and weekly telephone calls and emails, and will be evaluated by counting the numbers of capsules remaining on the final study visit. Each participant will attend the Adelaide Health and Medical Science Building Clinical Research Facility] for two hyperglycaemic clamp study visits, immediately before and at the end of the 2-week intervention (Days 0 and 14). Participants will commence their first dose of capsules with the lunch on Day 0 after baseline evaluation, and ingest the last dose of capsules on the morning of Day 14 for post-interventional evaluation. A faecal sample will be collected before the two study days, with subsequent microbiome testing using 16S rRNA sequencing. Participants will also complete a 3-day food diary before commencing the study and each week during the study period, using Research Food Diary (Xyris Software Pty Ltd, Brisbane, QLD, Australia). On the evening preceding each study day (~1900h), participants will consume a standardised evening meal (frozen beef lasagne, McCain Foods Proprietary Ltd, VIC, Australia; 2472kJ) with water. Following this meal, participants will be asked to fast from solids and liquids (water may be consumed until midnight) until the following morning, when they will attend the AHMS CRF at 0800h. This will be reinforced by a telephone call from one of the investigators. For participants with type 2 diabetes who are taking oral anti-diabetic medication(s), they will be instructed to withhold the doses for ~48h until the end of each study visit. The participant’s body weight will be recorded, and an intravenous cannula will be placed into a vein of each forearm for intravenous dextrose infusion and blood sampling, respectively. Then, a hyperglycaemic clamp will be performed from t = -30 to 120 min (to maintain blood glucose at 10 mmol/L in healthy participants, and 15 mmol/L in participants with type 2 diabetes; these levels of hyperglycaemia have been shown to induce profound urinary glucose excretion in our pilot studies [Protocol No: 2022/HRE00300]). This will be achieved by intravenous administration of an initial bolus of 25% dextrose (volume calculated to elevate blood glucose to the target level from baseline), followed by a 25% dextrose infusion at a rate adjusted according to blood glucose concentrations measured every 5 min using a Yellow Springs Instrument (YSI) analyser. Following an initial 30 min of stabilisation of the hyperglycaemic clamp, participants will be asked to empty their bladder at t = 0 min. Participants will consume 400 mL water every 30 min from t = -30 to 60 min (1600 mL water in total). At the post-intervention visit (Day 14), participants will ingest the final morning dose of the assigned treatment at t = -30 min. Urine samples will be collected at t = 60 and 120 min. The glucose concentration in the urine will be measured immediately using a YSI analyser. “Arterialised” venous blood will be sampled every 30 min, kept warm with a heat pad, between t = -30 and 120 min for measurement of plasma insulin. Fasting serum creatinine, transaminases and lipids levels will be measured. After the final blood sample is collected, participants will be served a light lunch. Once the blood concentration has stabilised >4 mmol/L for healthy participants and >5 mmol/L for participants with type 2 diabetes, they will be free to leave the laboratory. The total amount of blood drawn during the study visits will be ~200 mL.