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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
Effects of small intestinal quinine (bitter agonist) on gut function and blood glucose in healthy, lean volunteers.
Scientific title
Effects of intraduodenal quinine (bitter agonist), on upper gastrointestinal (GI) functions, energy intake and blood glucose, in healthy, lean volunteers.
Secondary ID [1] 291843 0
Nil known
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Obesity 303090 0
Type 2 Diabetes 303091 0
Healthy Human Gastrointestinal Physiology 303092 0
Condition category
Condition code
Diet and Nutrition 302548 302548 0 0
Oral and Gastrointestinal 302549 302549 0 0
Normal oral and gastrointestinal development and function
Metabolic and Endocrine 302550 302550 0 0

Study type
Description of intervention(s) / exposure
The intervention in this study consists of the intraduodenal infusion of a quinine or control solution over a 60 minute period during which the measurement of gut motility, blood glucose, gut hormone concentration, insulin concentrations, appetite perceptions and energy intake during a buffet meal will be measured.

Subjects enrolled into the study will receive, in randomized, double-blind fashion
(i) 0.625mg/min quinine,
(ii) 1.25mg/min quinine,
(iii) 3.75mg/min quinine.
(iv) saline (control)
each occurring at separate visits. Each visit will last 3-6hrs in duration, and will be separated by 3-7 days. Visits will be carried out in the clinic room facility of the Discipline of Medicine, University of Adelaide by staff members trained in the required techniques, and will be conducted on an individual basis.

Subjects will be asked to consume a standardised dinner meal the night before each visit by no later than 6pm, After fasting for 14 hrs overnight and refraining from exercise and alcohol for 24 hrs, subjects will arrive at the laboratory at 8am . Upon arrival, subjects will be intubated with a 17-channel manometric catheter that will be inserted through an anaesthetised nostril and allowed to pass through the stomach and into the duodenum by peristalsis. The manometric catheter consists of 16 side holes spaced at 1.5 cm intervals, measuring pressures in the antrum, pylorus, and duodenum (APD pressures). An additional channel (with the side hole positioned approx 14 cm distal to the pylorus when the catheter is in position) is used for intraduodenal infusions. The correct positioning of the catheter will be maintained by continuous measurement of the transmucosal potential difference (TMPD) between the most distal antral channel and the most proximal duodenal channel. All manometric channels will be perfused with degassed, distilled water, except for the two TMPD channels, which will be perfused with degassed 0.9% saline, at 0.15 ml/min. An intravenous cannula will be placed into a right forearm vein for regular blood sampling to measure plasma hormone concentrations. Once the catheter has been positioned correctly, fasting motility will be monitored continuously, and immediately after the end of phase III activity of the fasting migrating motor complex (MMC), during a period of motor quiescence (t=-15 - 0 min), a 10 ml venous blood sample (baseline) will be taken, and the subject will complete a visual analogue scale questionnaire (VAS) to assess appetite-related perceptions (fullness, hunger, etc.) and gastrointestinal symptoms (nausea and bloating). At t = 0 min (during phase I of the MMC), the 60-min intraduodenal infusion (either (i), (ii), or (iii) as outlined above) will commence . APD pressures will be measured continually over the 60-min period. Blood samples will be collected and VASs completed every 15 min from t = 0 to 60 min. At t = 60 min, the manometric catheter will be removed and subjects will be presented with a cold, buffet-style meal. Subjects will be allowed 30 min to freely consume food until they are comfortably full. At t = 90 min, a final blood sample will be taken, and VAS administered. The intravenous cannula will then be removed and subjects will be allowed to leave the laboratory. A total of 70 ml of blood will be taken on each study day (280 ml over all study visits).

In addition, on one further occasion, oral detection thresholds for bitter taste will be assessed using 3-Alternative Forced Choice procedure, an established technique for the quantification of oral taste detection thresholds. Samples for the assessment of bitter taste will be prepared using quinine dissolved in deionised water. All samples will be presented at room temperature, under a red light to minimise visual cues. Participants will wear nose-clips to ensure detection of differences is not due to smell, and will be asked to rinse their mouths with water after each set of samples. There will be 1 min between presentations of sample sets. A set of samples will be presented as three trays of three samples, each tray containing one sample of the quinine concentration being tested and two samples of deionised water. The subject will taste the samples from left to right on each tray and choose the one sample that tastes ‘odd’ compared to the other two. If the subject does not choose the three samples containing quinine in that set, they will be presented with the next set of samples at a higher concentration. Once the subject selects the three correct samples containing quinine, this will be recorded as their detection threshold.
Intervention code [1] 297956 0
Treatment: Other
Comparator / control treatment
Control group

Primary outcome [1] 301971 0
Energy intake at the buffet meal. The weight of the foods will be recorded before and after being offered to the subjects and energy intake and macronutrient composition calculated subsequently using commercially available software (Foodworks, Xyris Software, Highgate Hill, QLD, Australia).
Timepoint [1] 301971 0
A buffet meal will be presented immediately following each intraduodenal infusion (t = 60 - 90 min). The subject will be allowed to freely consume food until comfortably full for 30 minutes.
Primary outcome [2] 301972 0
Antropyloroduodenal motility (number of antral, duodenal and isolated pyloric pressure waves, and basal pyloric pressure) will be measured using a 17-channel manometric assembly (Dentsleeve, Mui Scientific).
Timepoint [2] 301972 0
Baseline (t = -15 - 0 min) and during intraduodenal infusion (t = 0 - 60 min).
Primary outcome [3] 301973 0
Plasma concentrations of gastrointestinal hormones (e.g. CCK, GLP-1, PYY, GIP and ghrelin), insulin and glucose will be assessed by Enzyme-linked Immunosorbent Assay (ELISA) or Radio Immnunosorbent Assay (RIA).

This intervention is of an exploratory nature to characterise the effects of varying doses of quinine. As such, it is unknown which plasma hormone concentrations may prove to be of importance. Hence these have been grouped into one composite primary outcome.
Timepoint [3] 301973 0
15 minute intervals from t=-15 - 60 min, and 90 min.
Secondary outcome [1] 334407 0
Appetite sensations (hunger, fullness, thirst, desire to eat, amount of food the subject thinks they could eat) and gastrointestinal symptoms (nausea, bloating) will be measured using a 100mm Visual Analogue Scale (VAS). This VAS has been extensively employed in published studies conducted by the investigator.

This intervention is of an exploratory nature to characterise the effects of varying doses of quinine. As such, it is unknown which appetite sensations or gastrointestinal symptoms may prove to be of importance. Hence these have been grouped into one composite secondary outcome.
Timepoint [1] 334407 0
15 minute intervals from t=-15 - 60 min, and 90 min.
Secondary outcome [2] 334420 0
Blood glucose will be assessed using a hospital grade portable glucmometer.
Timepoint [2] 334420 0
15 minute intervals from t=-15 - 60 min, and 90 min.
Secondary outcome [3] 334421 0
Oral bitter taste threshold will be assessed using 3-AFC technique.
Timepoint [3] 334421 0
To be conducted at a visit separate to the ID infusions.

Key inclusion criteria
A total of 12 healthy, lean (BMI 19-25 kg/m2) male subjects, aged between 18 - 55 years will be included. Subjects will be required to be weight stable (ie <5% fluctuation) at study entry, which will be ascertained by a stable body weight in the preceding 4 weeks.
Minimum age
18 Years
Maximum age
55 Years
Can healthy volunteers participate?
Key exclusion criteria
Significant gastrointestinal symptoms, disease or surgery;
Use of prescribed or non-prescribed medications (including vitamins and herbal supplements) which may affect energy metabolism, gastrointestinal function, body weight or appetite (eg domperidone and cisapride, anticholinergic drugs (eg atropine), metoclopramide, erythromycin, hyoscine, orlistat, green tea extracts, Astragalus, St Johns Wort etc.)
Lactose intolerance/other food allergy(ies)
Current gallbladder or pancreatic disease
Cardiovascular or respiratory diseases
Those with low ferritin levels (less than 30 ng/mL), or who have donated blood in the 12 weeks prior to taking part in the study
Any other illnesses as assessed by the investigator (including chronic illnesses not explicitly listed above)
High performance athletes
Current intake of greater than 2 standard drinks on greater than 5 days per week
Current smokers of cigarettes/cigars/marijuana
Current intake of any illicit substance
Inability to comprehend study protocol
Restrained eaters (score >12 on the three factor eating questionnaire)

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation involves contacting the holder of the randomisation table (study assistant) to inform them of the next subjects details and study dates. The unblinded study assistant is therefore responsible for allocating a randomly generated treatment sequence to the subject and preparing the intraduodenal infusion on each study day.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
The randomisation is generated using a randomization plan generator available at
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s
The people administering the treatment/s
The people assessing the outcomes
The people analysing the results/data
Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)

Funding & Sponsors
Funding source category [1] 296340 0
Government body
Name [1] 296340 0
National Health and Medical Research Council (NHMRC)
Address [1] 296340 0
National Health and Medical Research Council
GPO Box 1421
ACT 2601
Country [1] 296340 0
Primary sponsor type
Christine Feinle-Bisset
Level 5, Adelaide Health and Medical Sciences Building
Cnr North Terrace and George Street
South Australia 5005
Secondary sponsor category [1] 295270 0
Name [1] 295270 0
Tanya Little
Address [1] 295270 0
Level 5, Adelaide Health and Medical Sciences Building
Cnr North Terrace and George Street
South Australia 5005
Country [1] 295270 0

Ethics approval
Ethics application status
Ethics committee name [1] 297571 0
Royal Adelaide Hospital Human Research Ethics Committee
Ethics committee address [1] 297571 0
Central Adelaide Local Heath Network
Royal Adelaide Hospital
North Terrace
SA 5000
Ethics committee country [1] 297571 0
Date submitted for ethics approval [1] 297571 0
Approval date [1] 297571 0
Ethics approval number [1] 297571 0
RAH Protocol No. R20161005 HREC/16/RAH/410

Brief summary
The purpose of this trial is to investigate the dose-related effects of small intestinal administration of the bitter agonist, quinine, a non-nutritive (calorie-free) compound, on the motor and hormone functions of the upper gastrointestinal tract, appetite, energy intake and blood glucose. The relationship between outcomes and the ability to detect bitter in the oral cavity will also be investigated.
We have found previously that specific dietary nutrients, when given into the small intestine in small amounts (and so not contributing significantly to overall energy intake) have the unique ability to substantially stimulate gastrointestinal functions leading to marked energy intake suppression and improvements in postprandial blood glucose. There has been a recent interest in the effects of bitter compounds, some of which also occur in the diet, including thio-urea compounds in certain vegetables or fruit, or quinine in tonic water, with reported effects on gut functions and energy intake suppression.
This study aims to characterise the dose-related effects of quinine, when delivered to the small intestine, in an effort to identify an optimal dose for beneficial effect on the outcomes mentioned herein. This may then guide future research to evaluate hypotheses that observed effects may be further enhanced by combining nutrients with quinine.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 74478 0
Prof Christine Feinle-Bisset
Address 74478 0
Level 5, Adelaide Health and Medical Sciences Building
Cnr North Terrace and George Street
South Australia 5005
Country 74478 0
Phone 74478 0
+61 8 8313 6053
Fax 74478 0
Email 74478 0
Contact person for public queries
Name 74479 0
Prof Christine Feinle-Bisset
Address 74479 0
Level 5, Adelaide Health and Medical Sciences Building
Cnr North Terrace and George Street
South Australia 5005
Country 74479 0
Phone 74479 0
+61 8 8313 6053
Fax 74479 0
Email 74479 0
Contact person for scientific queries
Name 74480 0
Prof Christine Feinle-Bisset
Address 74480 0
Level 5, Adelaide Health and Medical Sciences Building
Cnr North Terrace and George Street
South Australia 5005
Country 74480 0
Phone 74480 0
+61 8 8313 6053
Fax 74480 0
Email 74480 0

No data has been provided for results reporting
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary