J Neurogastroenterol Motil  https://doi.org/10.5056/jnm19036
Effects of Intraduodenal Infusion of the Bitter Tastant, Quinine, on Antropyloroduodenal Motility, Plasma Cholecystokinin, and Energy Intake in Healthy Men
Vida Bitarafan,1 Penelope C E Fitzgerald,1 Tanya J Little,1 Wolfgang Meyerhof,2 Tongzhi Wu,1,3 Michael Horowitz,1,3 and Christine Feinle-Bisset1*
1Adelaide Medical School and National Health and Medical Research Council of Australia (NHMRC) Centre of Research Excellence in Translating Nutritional Science to Good Health, University of Adelaide, Adelaide, Australia
2Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
3Endocrine and Metabolic Unit, Royal Adelaide Hospital, Adelaide, Australia
Correspondence to: Christine Feinle-Bisset, PhD
Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide SA 5005, Australia
Tel: +61-8-8313-6053, E-mail: christine.feinle@adelaide.edu.au
Received: February 14, 2019; Revised: March 22, 2019; Accepted: April 7, 2019; Published online: May 16, 2019.
© The Korean Society of Neurogastroenterology and Motility. All rights reserved.

cc This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Background/Aims
Nutrient-induced gut hormone release (eg, cholecystokinin [CCK]) and the modulation of gut motility (particularly pyloric stimulation) contribute to the regulation of acute energy intake. Non-caloric bitter compounds, including quinine, have recently been shown in cell-line and animal studies to stimulate the release of gastrointestinal hormones by activating bitter taste receptors expressed throughout the gastrointestinal tract, and thus, may potentially suppress energy intake without providing additional calories. This study aims to evaluate the effects of intraduodenally administered quinine on antropyloroduodenal pressures, plasma CCK and energy intake.
Methods
Fourteen healthy, lean men (25 ± 5 years; BMI: 22.5 ± 2.0 kg/m2) received on 4 separate occasions, in randomized, double-blind fashion, 60-minute intraduodenal infusions of quinine hydrochloride at doses totaling 37.5 mg (“Q37.5”), 75 mg (“Q75”) or 225 mg (“Q225”), or control (all 300 mOsmol). Antropyloroduodenal pressures (high-resolution manometry), plasma CCK (radioimmunoassay), and appetite perceptions/gastrointestinal symptoms (visual analog questionnaires) were measured. Ad libitum energy intake (buffet-meal) was quantified immediately post-infusion. Oral quinine taste-thresholds were assessed on a separate occasion using 3-alternative forced-choice procedure.
Results
All participants detected quinine orally (detection-threshold: 0.19 ± 0.07 mmol/L). Intraduodenal quinine did not affect antral, pyloric or duodenal pressures, plasma CCK (pmol/L [peak]; control: 3.6 ± 0.4, Q37.5: 3.6 ± 0.4, Q75: 3.7 ± 0.3, Q225: 3.9 ± 0.4), appetite perceptions, gastrointestinal symptoms or energy intake (kcal; control: 1088 ± 90, Q37.5: 1057 ± 69, Q75: 1029 ±7 0, Q225: 1077 ± 88).
Conclusion
Quinine, administered intraduodenally over 60 minutes, even at moderately high doses, but low infusion rates, does not modulate appetite-related gastrointestinal functions or energy intake.
Keywords: Cholecystokinin; Energy intake; Gastrointestinal hormones; Pylorus; Quinine


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