Effects of Intragastric Quinine, Alone or Combined With L-isoleucine, on Postprandial Glycaemic Control

Summary

In this study, participants will receive, in randomized, double-blind fashion, an intragastric bolus administration of either (i) 300 mg quinine, (ii) 5 g L-isoleucine, (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, and appetite, 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-isoleucine 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, labeled 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.

Conditions

• Healthy

Interventions

OTHER

Quinine

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.

OTHER

L-isoleucine

L-isoleucine, 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.

OTHER

Combination of quinine and L-isoleucine

In this condition, both quinine and L-isoleucine will be administered as 'active'.

OTHER

Control

In the condition, where quinine is 'active', control for L-isoleucine (5 ml oraplus and 95 ml saline) will be administered. In the condition, where L-isoleucine will be 'active', control for quinine (10 ml distilled water) will be administered. Whereas, in a control condition, both for quinine and L-isoleucine, a control solution will be administered.

Sponsors & Collaborators

• University of Adelaide

  lead OTHER

Principal Investigators

• Christine Feinle-Bisset, PhD · University of Adelaide, Adelaide, South Australia

Study Design

Allocation

RANDOMIZED

Purpose

OTHER

Masking

TRIPLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

55 Years

Sex

MALE

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2023-06-19

Primary Completion

2024-06-24

Completion

2024-06-24

Countries

• Australia

Study Locations