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Trial registered on ANZCTR


Registration number
ACTRN12617000837325p
Ethics application status
Submitted, not yet approved
Date submitted
2/06/2017
Date registered
7/06/2017
Date last updated
7/06/2017
Type of registration
Prospectively registered

Titles & IDs
Public title
The GLARE (Glucose Lowering Antioxidant-Rich Food Extracts) Study: Can Antioxidant-Rich food extracts reduce your risk of diabetes?
Scientific title
The GLARE (Glucose Lowering Antioxidant-Rich Food Extracts) Study: Impact of antioxidant-rich food extracts on postprandial blood glucose response in people with prediabetes.
Secondary ID [1] 292109 0
Nil known
Universal Trial Number (UTN)
U1111-1196-7749
Trial acronym
GLARE
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Prediabetes 303531 0
Dysglycaemia 303532 0
type 2 diabetes 303533 0
postprandial blood glucose 303543 0
Condition category
Condition code
Metabolic and Endocrine 302940 302940 0 0
Diabetes
Diet and Nutrition 302941 302941 0 0
Obesity
Metabolic and Endocrine 302960 302960 0 0
Metabolic disorders

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
The acute effect of four antioxidant-rich food extracts on postprandial blood glucose and insulin response in people with prediabetes will be investigated.

The following four antioxidant-rich products will be tested in this study: Amla berry extract (Sharman Ltd, Nelson, New Zealand); Grape seed extract (NutraLife, New Zealand Ltd),; Rooibos tea extract (Rooibos Ltd, Clanwilliam, South Africa) and Olive Leaf Extract (COMVITA, NZ)

Dose: For this study we will have 2.0 times the total antioxidant capacity (i.e approx 640 mg) as was performed in Chepulis et al. (2016) study. Antioxidant activity (as determined by ORAC assay) of each product used in this study, will be measured by Callaghan Innovation (Wellington, New Zealand. For the purposes of comparison a vitamin E sample (with a known effective concentration half-life (EC50) of 0.44 mg/mL) is included. EC50 values of the tests samples will be calculated as mg/mL. Each test sample will have equivalent total antioxidant activity and on a weight per weight basis the number of capsules (for 2x antioxidant capacity) consumed by the participant orally before the OGTT will be determined once antioxidant activity for the product has been assessed.

The test session will include: An OGTT with placebo control capsule or antioxidant-rich food extract capsule administered 10 minutes before the glucose drink (75 g glucose in 200 mL water). Participants will be cannulated and observed over a 2 hour period with blood samples taken at T=0, 15, 45, 60, 90, and 120 minutes. The participant will be fasted (approx 10 hrs) before starting test session. A researcher and assistant will be present throughout the OGTT.


All participants (recruitment of 20) will undergo 5 test sessions (placebo control and 4 antioxidant-rich food extracts. There will be a minimum of 48 hrs washout period between each test session. The full testing should take between 8-10 weeks.

Between Test Sessions:
All participants will be asked to keep their diet and lifestyles as constant as possible throughout the study and to refrain from engaging in any strenuous physical activity (walking is fine) or consumption of alcohol in the 24-hour period prior to each test session. Participants will also be asked to avoid the active test foods/extracts for at least seven days prior to the first test session and throughout the duration of the test period (including avoiding other teas and formulations where the extracts may be present. A list of such foods/teas and formulations will be provided to participants).

Chepulis, L., Al-Aubaidy, H., Page, R. (2016) Effect of selected antioxidant food extracts on postprandial glucose responses in healthy individuals. Functional Foods in Health and Disease, 6(8): 493-505
Intervention code [1] 298255 0
Treatment: Other
Intervention code [2] 298256 0
Prevention
Comparator / control treatment
The placebo control capsule will contain Cellulose, NF microcrystalline. The placebo capsule will be of similar colour and shape as the capsules containing the antioxidant-rich food extracts.
Control group
Placebo

Outcomes
Primary outcome [1] 302339 0
postprandial blood glucose incremental area under curve
Timepoint [1] 302339 0
blood sample taken at -10,0,15,30,45, 60, 90, 120 minutes after glucose drink
Secondary outcome [1] 335565 0
postprandial blood insulin incremental area under curve
Timepoint [1] 335565 0
blood sample taken at -10, 0, 15, 30,45, 60, 90, 120 minutes after glucose drink
Secondary outcome [2] 335566 0
antioxidant capacity as determined via ORAC assay. Data expressed as Trolox equivalents (TE) per volume sample
Timepoint [2] 335566 0
blood sample taken at -10, 0, 15, 30,45, 60, 90, 120 minutes after glucose drink
Secondary outcome [3] 335613 0
pancreatic beta-cell function as determined by Insulin Secretion Sensitivity Index-2
Timepoint [3] 335613 0
Blood sample at T=-10, 0, 15,30.45.60.90,120 minutes after glucose drink
Secondary outcome [4] 335678 0
hepatic insulin sensitivity as calculated by the homeostasis model assessment of insulin resistance (HOMA-IR)
Timepoint [4] 335678 0
Blood sample at T=-10, 0, 15, 30.45.60.90,120 minutes after glucose drink
Secondary outcome [5] 335679 0
Matsuda-DeFronzo insulin sensitivity index (ISI-M)
Timepoint [5] 335679 0
Blood sample at T=-10, 0, 15, 30.45.60.90,120 minutes after glucose drink

Eligibility
Key inclusion criteria
1.. Glycated haemoglobin (HbA1c) between 41-49 mmol/mol.
2. Body mass index (BMI) between 20-35 kg/m2 at time of screening.
Minimum age
40 Years
Maximum age
60 Years
Gender
Both males and females
Can healthy volunteers participate?
No
Key exclusion criteria
1. On any medication that has an effect on blood glucose levels.
2. Has renal or cardiac impairments
3. Has asthma or on asthma-related medication
4. Known allergies to any of the antioxidant extracts (amla berry, grapeseed, olive leaf or rooibos tea).
5. Smoker

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)
Researcher conducting participant allocation will be different to the researcher involved in participant screening. Allocation will remain hidden from the researcher performing the screening by keeping the information in a secure computer database.

The test sample (placebo or antioxidant-rich food extract) will be randomised at each test session until the participant has been administered and had OGTT with all test samples.

Participant will not know what test sample they are being administered.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Researcher will have all prepared test samples ready for each test session and will know what test sample the participant is receiving at their test session.

Simple randomisation using computerised sequence generator will be used to determine the order in which the participant receives each treatment (test sample) for each test session.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s


Intervention assignment
Crossover
Other design features
Phase
Not Applicable
Type of endpoint(s)
Efficacy
Statistical methods / analysis
Sample Size:
A 95% confidence level, 80% power and a = 0.05; beta = 0.10. The SD (based on Moore et al, 2001 study) is 100 mmol. We are aiming for an effect reduction of 100 mmol. Accordingly, 16 subjects will need to be recruited. to obtain statistically significant results. To account for 20% participant drop-out, a total of 20 subjects will be recruited for this study.

The mean IAUC of placebo control will be compared to IAUC values of carbohydrate plus antioxidant using a repeated measures ANOVA with Scheffe Post Hoc analyses to examine impact of antioxidant on postprandial blood glucose and insulin response. The data may not be normally distributed and therefore may require nonparametric statistics using Kruskal Wallis for instance with Mann-Whitney U test as post hoc option. A P value of 0.05 or less will be considered to be significant.

Recruitment
Recruitment status
Not yet recruiting
Date of first participant enrolment
Anticipated
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
Accrual to date
Final
Recruitment outside Australia
Country [1] 8949 0
New Zealand
State/province [1] 8949 0
Auckland

Funding & Sponsors
Funding source category [1] 296645 0
University
Name [1] 296645 0
Massey University
Address [1] 296645 0
Palmerston North 4442, New Zealand
Country [1] 296645 0
New Zealand
Primary sponsor type
University
Name
Massey University
Address
School of Food and Nutrition, College of Health, Palmerston North 4442, New Zealand
Country
New Zealand
Secondary sponsor category [1] 295603 0
None
Name [1] 295603 0
Address [1] 295603 0
Country [1] 295603 0

Ethics approval
Ethics application status
Submitted, not yet approved
Ethics committee name [1] 297872 0
HDEC
Ethics committee address [1] 297872 0
Ministry of Health, 133 Molesworth Street, PO Box 5013, Wellington 6011
Ethics committee country [1] 297872 0
New Zealand
Date submitted for ethics approval [1] 297872 0
25/05/2017
Approval date [1] 297872 0
Ethics approval number [1] 297872 0

Summary
Brief summary
People with prediabetes (an intermediate state of hyperglycaemia diagnosed by glycated haemoglobin (HbA1c) range of 41 – 49 mmol/mol) are at high-risk of developing type 2 diabetes mellitus (T2DM). Currently, the estimated conversion rate of prediabetes to T2DM is 5-10% annually.
Food-based antioxidants are being investigated for their ability to be able to modulate blood glucose levels. A recent study has shown that 4 antioxidant-rich food extracts (Amla berry-, Grape seed-,Rooibos tea- and Green tea- extracts) significantly decreased the postprandial blood glucose response in healthy subjects response by 25-40% compared to a glucose-control (all p < 0.05). Little is known about whether these food supplements/extracts can be used to improve glycaemic control in persons with prediabetes
Hyperglycaemia and insulin resistance are the main pathophysiological changes behind the development of prediabetes and T2DM. Prediabetes has been recognised as being the key period during which interventions may lead to a slowing or a prevention of development of T2DM. This proposed study will initiate investigations into the use of antioxidant-rich food extracts as an intervention for reducing postprandial hyperglycaemia in people with prediabetes and reducing progression of prediabetes to T2DM.

Overall Aim of this Study:
To examine the acute effects of specific antioxidant-rich food extracts (rooibos tea, amla berry, olive leaf extract and grapeseed extract) in reducing postprandial blood glucose response in people with prediabetes.

Secondary Aim of this Study:
To examine the acute term effects of four antioxidant-rich food extracts on insulin response and antioxidant capacity in people with prediabetes
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 75330 0
A/Prof Rachel Page
Address 75330 0
School of Food and Nutrition, PO Box 756, Massey University, Wellington 6140
Country 75330 0
New Zealand
Phone 75330 0
+64 4 8015799
Fax 75330 0
Email 75330 0
r.a.page@massey.ac.nz
Contact person for public queries
Name 75331 0
A/Prof Rachel Page
Address 75331 0
School of Food and Nutrition, PO Box 756, Massey University, Wellington 6140
Country 75331 0
New Zealand
Phone 75331 0
+64 4 8015799
Fax 75331 0
Email 75331 0
r.a.page@massey.ac.nz
Contact person for scientific queries
Name 75332 0
A/Prof Rachel Page
Address 75332 0
School of Food and Nutrition, PO Box 756, Massey University, Wellington 6140
Country 75332 0
New Zealand
Phone 75332 0
+64 4 8015799
Fax 75332 0
Email 75332 0
r.a.page@massey.ac.nz

No information has been provided regarding IPD availability
Summary results
No Results