An interventional study of Quinine and L-leucine in Healthy, sponsored by University of Adelaide. Completed at 1 site in Australia. Open to male participants aged 18 Years to 55 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2024-12-10.
Sponsored by University of Adelaide · Not applicable, Interventional, and Other
In this study, participants will receive, in a randomized, double-blind fashion, an intragastric bolus administration of either (i) 300 mg quinine, (ii) 5 g L-leucine, (iii) a combination of (i)+(ii), or (iv) control, before 350 ml (500 kcal) of a mixed-nutrient drink, to evaluate the effects on postprandial blood glucose, gastric emptying, and the hormone responses to the mixed-nutrient drink. Study visits will be separated by 3-7 days and participants will receive one treatment per visit.
On each study visit, the participant will be intubated with a nasogastric feeding tube. At t= - 60 min (08:30 am), a baseline blood sample, visual analogue scale questionnaire (VAS), and breath sample will be collected and quinine or control will be administered through the feeding tube. 30 min later (at t= - 30 min), L-leucine or control will be administered over 2 min after which the feeding tube will be removed immediately. At t = -45, -30, -15, and -1 min further blood samples will be collected and VAS completed. At t = -1 min, participants will consume, within 1 minute, a mixed-nutrient drink, labelled with 100 mg of 1-13C-acetate for measurement of gastric emptying by breath sampling. Blood samples, VAS, and breath samples will be taken at regular intervals between t = 0-180 min.
This trial aims to assess the effects of intragastric administration of quinine, combined with L-leucine, on postprandial blood glucose, gastric emptying, gut and gluco-regulatory hormones, as well as GI symptoms in response to a mixed-nutrient drink.
Each participant will be studied on 4 occasions, separated by 3-7 days. Participants will receive, in randomized, double-blind fashion, an intragastric bolus of (i) 300 mg quinine, (ii) 5 g L-leucine, (iii) combination of (i)+(ii), or (iv) control. Due to the low water solubility, L- leucine will be provided as a suspension using 5 ml of 'the suspending agent' Ora-Plus (manufactured by Perrigo, Minneapolis). Visits will be carried out at the Clinical Research Facility, Adelaide Medical School, University of Adelaide, by staff and students trained in the required clinical research techniques.
Participants will consume a standardized dinner meal (400g McCain's beef lasagne) the night before each study visit by no later than 7 pm. After fasting for 13.5 hours overnight and refraining from alcohol and exercise for 24 hours, participants will arrive at the Clinical Research Facility by 8:30 am. Upon arrival, participants will be intubated with a nasogastric, custom-built soft silicon feeding tube (outer diameter: 4mm; Dentsleeve, Mississauga, Ontario, Canada) that will be inserted through an anaesthetized nostril and placed in the stomach. An intravenous cannula will be placed into a right forearm vein for regular blood sampling. At t = -60 min, a venous baseline blood sample (6 ml) will be collected and the participant will complete a visual analogue scale questionnaire (VAS) to assess GI symptoms (nausea and bloating). Immediately thereafter, the participant will receive a 10- ml intragastric bolus of either 300 mg quinine-hydrochloride (Q-HCl) or water (control), and 30 min later, at t -30 min, an intragastric bolus of L-leucine (100 ml suspension consisting of 5 g L- leucine, 5 ml Ora-Plus and 90 ml 0.9% saline) or control (5 ml Ora-Plus and 95 ml saline) over 1 min after which time the catheter will be removed immediately. At t = -1 min, the participant will consume, within 1 min, a mixed-nutrient drink (Nestle, 500 kcal, 350 ml, 56 g carbohydrates) labelled with 100 mg of 1-13C-acetate for measurement of gastric emptying by breath sampling. Breath samples will be collected in sealed breath bags at baseline (prior to quinine administration) and at regular intervals between t = 0-180 min, for subsequent analysis of 13CO2 concentration in exhaled breath. Blood samples for the measurement of glucose and plasma concentrations of hormones will be taken regularly (12 sampling time points in total), and participant complete VAS questionnaires. At t = 180 min, after final blood and breath samples and VAS measurements, the intravenous cannula will be removed and the participant will be served a light lunch, after which they will be allowed to leave the laboratory.
University of Adelaide is the lead sponsor of 42 studies on the registry; 6 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Exclusion Criteria:
In this arm, participants will receive a 10 ml intragastric bolus of 300 mg quinine followed 30 min later by 100 ml intragastric bolus of control for L-leucine.
Other: Quinine · Other: Control
In this arm, participants will receive a 10 ml intragastric bolus of control for quinine followed 30 min later by 100 ml intragastric bolus of 5 g L-leucine.
Other: L-leucine · Other: Control
In this arm participants will receive a 10 ml intragastric bolus of 300 mg quinine followed 30 min later by 100 ml intragastric bolus of 5 g L-leucine.
Other: Combination of quinine and L-leucine
In this arm, participants will receive a 10 ml intragastric bolus of control solution followed 30 min later by 100 ml intragastric bolus of control solution.
Other: Control
Quinine, which is a bitter compound, extracted from the bark of the cinchona tree and has been shown in our previous studies to lower blood glucose in doses of 300-600 mg, will be 'active' in this condition.
L-leucine, which is a branched-chain amino acid, and one of the building blocks of protein, therefore is part of our daily diet, will be 'active' in this condition.
In this condition, both quinine and L-leucine will be administered as 'active'.
In the condition, where quinine is 'active', control for L-leucine (5 ml oraplus and 95 ml saline) will be administered. In the condition, where L-leucine will be 'active', control for quinine (10 ml distilled water) will be administered.
Change from baseline plasma glucose concentration after a mixed-nutrient drink for 3 hours
Plasma glucose concentrations (mmol/L) will be assessed using glucose oxidase method
Time frame: Blood samples will be taken repeatedly within each study visit (i.e. at baseline (t= 0 minute), after administration of study treatments (t= -45, -30, -15 minutes) and after a mixed-nutrient drink (t= 0, 15, 30, 45, 60, 90, 120 and 180 minutes).
Gastric emptying of a mixed nutrient drink
Measurement of 13CO2 in breath samples, expressed as percentage of 13CO2 recovery per hour
Time frame: Breath samples will be taken repeatedly on each study visit (i.e. t= 0 (baseline), 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 75, 90, 105,120, 135, 150, 165, 180 minutes) to construct a gastric emptying profile on each day.
Plasma concentration of insulin after a mixed-nutrient drink
Plasma insulin concentrations (mU/L) will be assessed using an ELISA immunoassay.
Time frame: Blood samples will be taken repeatedly within each study visit (i.e. at baseline (t= 0 minute), after administration of study treatments (t= -45, -30, -15 minutes) and after a mixed-nutrient drink (t= 0, 15, 30, 45, 60, 90, 120 and 180 minutes).
Plasma concentration of glucagon after a mixed-nutrient drink
Plasma glucagon concentrations (pg/mL) will be measured by radioimmunoassay
Time frame: Blood samples will be taken repeatedly within each study visit (i.e. at baseline (t= 0 minute), after administration of study treatments (t= -45, -30, -15 minutes) and after a mixed-nutrient drink (t= 0, 15, 30, 45, 60, 90, 120 and 180 minutes).
Gastrointestinal symptoms (nausea and bloating)
Gastrointestinal symptoms will be measured using a 100-mm Visual Analogue Scale (VAS) questionnaire. The minimum value means no feeling at all, and the highest value means feeling very much.
Time frame: Visual Analogue ratings will be collected repeatedly within each study visit (i.e. at baseline (t = 0 minute), after administration of treatments (t= -45, -30, -15 minutes) and after mixed-nutrient drink (t= 0, 15, 30, 45, 60, 90, 120 and 180 minutes).
Plan to share: No — The datasets generated during and/or analysed during the current study are not publicly available due to the ethical statement and informed consent that require privacy of data.
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University of Adelaide