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Trial registered on ANZCTR

Registration number

ACTRN12621000311853

Ethics application status

Approved

Date submitted

15/02/2021

Date registered

19/03/2021

Date last updated

19/03/2021

Date data sharing statement initially provided

19/03/2021

Type of registration

Retrospectively registered

Titles & IDs

Public title

Kawakawa tea and its effect on glucose absorption in healthy human volunteers

Scientific title

Impact of acute kawakawa tea ingestion on postprandial glucose metabolism in healthy human volunteers

Secondary ID [1]

None

Universal Trial Number (UTN)

U1111-1261-6413

Trial acronym

TOAST

Linked study record

Health condition

Health condition(s) or problem(s) studied:

Type 2 Diabetes Mellitus

Cardiovascular disease

Condition category

Condition code

Metabolic and Endocrine

Diabetes

Cardiovascular

Other cardiovascular diseases

Intervention/exposure

Study type

Interventional

Description of intervention(s) / exposure

This study will examine the postprandial glycaemic response after an acute (single) ingestion of either water or kawakawa tea (4g per 250ml of hot water). As previously reported (1), the postprandial state lasts for approximately 4-5 h post-meal period. Participants under the supervision of the clinical coordinator will complete a screening assessment and, if eligible for entry into the trial, will be required in fasted condition to consume either a kawakawa tea infusion (4g per 250ml of hot water) or only hot water within 10 minutes based on their randomisation schedule. Following the intervention, a high glycaemic breakfast containing two slices of white bread, along with 15g of fruit jam and 250ml of rice milk, will be provided after 30 minutes, and participants will be asked to finish within 10 minutes. Blood will be sampled at regular intervals following their visit in fasting state at 0 min and then postprandial following tea or hot water at 30, 45, 60, 90, 120, 180 mins from a cannula inserted into an arm vein. Urine samples will be collected in a fasting state at 0 min, and then 0-4hrs urine will be collected postprandial following tea or hot water consumption. Since this is a two-arm, two-way cross over study, the participants will be required to come again for the intervention after a washout period of at least 48hrs.

References
1. Monnier L, Colette C. Target for glycemic control: concentrating on glucose. Vol. 32 Suppl 2, Diabetes care. 2009.

Intervention code [1]

Prevention

Intervention code [2]

Treatment: Other

Comparator / control treatment

Hot water-(250ml)

Control group

Active

Outcomes

Primary outcome [1]

To examine the effects of kawakawa tea intake prior to consumption of high glycaemic meal on postprandial plasma glucose metabolism in healthy individuals

Timepoint [1]

Blood samples collected at fasting and then after the intervention at 30, 45, 60, 90, 120, and 180 mins will be utilised to measure the biochemical parameters of glucose absorption using an Autoanalyser.

Secondary outcome [1]

To measure the impact of kawakawa tea ingestion on the inflammatory cytokines such as IL-6, IL-1, TNF-ALPHA, NF-Kb and other cytokines that are part of different inflammatory pathways, using PBMC gene expression.

Timepoint [1]

Blood samples collected at fasting and then after the intervention at 30, 45, 60, 90, 120, and 180 mins will be analysed for changes in gene and microRNA expression.

Secondary outcome [2]

To measure the impact of kawakawa tea ingestion on plasma insulin,

Timepoint [2]

Blood samples collected at fasting and then after the intervention at 30, 45, 60, 90, 120, and 180 mins will be analysed for changes in these biochemical measures using Roche Cobas e411 by electro-chemiluminescence immunoassay.

Secondary outcome [3]

To measure the impact of kawakawa tea ingestion on blood lipids including Cholesterol (Total, High-density lipoprotein cholesterol, and low-density lipoprotein cholesterol (LDL-C) and triglycerides.

Timepoint [3]

Blood samples collected at fasting and then after the intervention at 30, 45, 60, 90, 120, and 180 mins will be analysed by Roche Cobas c311 autoanalyser by enzymatic colorimetric assay

Secondary outcome [4]

To measure the impact of kawakawa tea ingestion on metabolomic changes in the Urine samples

Timepoint [4]

Both fasting urine and samples collected post-intervention at 60, 120 and 180 minutes will be analysed using LC-MS.

Eligibility

Key inclusion criteria

• Gender: both males and females. To control for menstruation cycle variation in results, female participants would be required to come in the same phase of their cycle for both the intervention visits.
• Age: 18-45 yr.
• BMI: 18-25 kg/m2
• Non-smokers
• Self-reported not consuming dietary supplements
• No medical conditions

Minimum age

18 Years

Maximum age

45 Years

Sex

Both males and females

Can healthy volunteers participate?

Yes

Key exclusion criteria

Participants will be excluded from participation if they:
• Are taking dietary supplements or herbal remedies which may affect the study outcome
• Are allergic to pepper, nutmeg or similar spices
• Are diagnosed with gastrointestinal disease (i.e. celiac, Crohn’s, colitis, etc.) or pre-existing metabolic disease
• Are currently taking medications expected to interfere with normal digestive or metabolic processes including proton pump inhibitors, laxatives, etc.
• Have used antibiotics within the previous one month or were on long-term antibiotic therapy.
•Have a medical history precluding a healthy state: a history of myocardial infarction, angina, stroke, cancer or pre-existing diabetes.

Study design

Purpose of the study

Prevention

Allocation to intervention

Randomised controlled trial

Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)

Participants will be randomised to receive the intervention or the control as the first in a crossover sequence using computer-generated sequences.

Methods used to generate the sequence in which subjects will be randomised (sequence generation)

The allocation sequence will be set up through a web-based secure database. Sequences will not be accessible to the research team prior to allocation.

Masking / blinding

Open (masking not used)

Who is / are masked / blinded?

Intervention assignment

Crossover

Other design features

Randomised, Open-label, Two-arm, Two-period crossover trial

Phase

Not Applicable

Type of endpoint/s

Efficacy

Statistical methods / analysis

Differences in the primary endpoints will be compared between treatment groups using Repeated measure ANOVA or non-parametric tests where appropriate and followed-up with posthoc tests. The relationship between secondary end-points will be assessed using multiple regression analysis.

Recruitment

Recruitment status

Recruiting

Date of first participant enrolment

Anticipated

Actual

15/03/2021

Date of last participant enrolment

Anticipated

1/06/2021

Actual

Date of last data collection

Anticipated

30/09/2021

Actual

Sample size

Target

Accrual to date

Final

Recruitment outside Australia

Country [1]

New Zealand

State/province [1]

Auckland

Funding & Sponsors

Funding source category [1]

University

Name [1]

Liggins Institute, The University of Auckland

Address [1]

85 Park Road, Grafton, Auckland 1023.

Country [1]

New Zealand

Primary sponsor type

University

Name

Liggins Institute, The University of Auckland

Address

85 Park Road, Grafton, Auckland 1023.

Country

New Zealand

Secondary sponsor category [1]

None

Name [1]

None

Address [1]

None

Country [1]

Ethics approval

Ethics application status

Approved

Ethics committee name [1]

Southern Health and Disability Ethics Committee

Ethics committee address [1]

Ministry of Health
Health and Disability Ethics Committees
133 Molesworth Street, Thorndon
Wellington 6011

Ethics committee country [1]

New Zealand

Date submitted for ethics approval [1]

23/11/2020

Approval date [1]

12/02/2021

Ethics approval number [1]

20/STH/236

Summary

Brief summary

Kawakawa (Piper excelsum) is endemic to New Zealand, where it is widely used for food, therapeutic and traditional ceremonial purposes by Maori. Kawakawa leaves and fruits are reported to contain various active compounds including phenylpropanoids: myristicin, elemicin, piperine; lignans: diayangambin; and amides: piperchabamide, which are shown to possess therapeutic properties and are utilised for a wide range of health conditions not only limited to skin diseases but for the treatment of genitourinary, gastrointestinal as well as respiratory diseases.

Despite the traditional use of kawakawa and its use in commercial products, no studies have been conducted to examine whether kawakawa would impact postprandial glucose metabolism, an important factor responsible for the development of type 2 diabetes (T2DM) and cardiovascular disease (CVDs). Therefore, we aim to examine the effects of kawakawa tea ingestion on postprandial glucose flux using a human randomized controlled intervention

Trial website

Trial related presentations / publications

Public notes

Contacts

Principal investigator

Name

Prof Richard Mithen

Address

Liggins Institute University of Auckland 85 Park Road Grafton Auckland 1023

Country

New Zealand

Phone

+64 27 201 7675

Fax

[email protected]

Contact person for public queries

Name

Richard Mithen

Address

Liggins Institute University of Auckland 85 Park Road Grafton Auckland 1023

Country

New Zealand

Phone

+64 27 201 7675

Fax

[email protected]

Contact person for scientific queries

Name

Farha Ramzan

Address

Liggins Institute University of Auckland 85 Park Road Grafton Auckland 1023

Country

New Zealand

Phone

+64224505345

Fax

[email protected]

Data sharing statement

Will the study consider sharing individual participant data?

Yes

Will there be any conditions when requesting access to individual participant data?

Persons/groups eligible to request access:
• Data will be available to investigators who provide a methodologically sound proposal approved by the Study Steering Committee, for use to achieve the aims in the approved proposal. Proposals should be directed to the principal investigator. To gain access, requests will need to sign a data access agreement.

Conditions for requesting access:
• -

What individual participant data might be shared?

• All of the Individual participant data (including data dictionaries) collected during the trial will be available after de-identification, along with the study protocol.

What types of analyses could be done with individual participant data?

• For use to achieve the aims in an approved proposal.

When can requests for individual participant data be made (start and end dates)?

From:
Data will be available beginning 3 months following the first publication of study results and ending 36 months following publication.

To:
-

Where can requests to access individual participant data be made, or data be obtained directly?

• Proposals should be directed to the principal investigator ([email protected]). To gain access, requests will need to sign a data access agreement.

Are there extra considerations when requesting access to individual participant data?

What supporting documents are/will be available?

Doc. No.	Type	Email	Attachment
10682	Study protocol	[email protected]	Study-related document.docx
10683	Informed consent form	[email protected]	Study-related document.doc
10684	Ethical approval	[email protected]	Study-related document.pdf

Results publications and other study-related documents

Documents added manually

No documents have been uploaded by study researchers.

Documents added automatically

Source	Title	Year of Publication	DOI
Dimensions AI	Acute Effects of Kawakawa (Piper excelsum) Intake on Postprandial Glycemic and Insulinaemic Response in a Healthy Population	2022	https://doi.org/10.3390/nu14081638

N.B. These documents automatically identified may not have been verified by the study sponsor.

Trial Review

Documents added manually

Documents added automatically