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Metabolic Benefits of Drinking Blueberry Tea in Type 2 Diabetes

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ClinicalTrials.gov Identifier: NCT02629952
Recruitment Status : Recruiting
First Posted : December 15, 2015
Last Update Posted : September 13, 2017
Sponsor:
Information provided by (Responsible Party):
Michelle Keske, Menzies Institute for Medical Research

Brief Summary:
Plant derived compounds, e.g. flavonoids from dark chocolate, green tea, or blueberries, show great potential as nutraceuticals for the treatment of various diseases such as type 2 diabetes (T2D). Flavonoids have been suggested to improve glucose metabolism, reduce blood lipids, reduce oxidative stress and improve vascular function. For these reasons we recently investigated the effects of daily consumption of locally produced blueberry tea and demonstrated that this could partially restore insulin sensitivity in an animal model. We propose to translate these findings to assess the efficacy of this nutraceutical as a new treatment for improving glucose tolerance in people with T2D.

Condition or disease Intervention/treatment Phase
Type 2 Diabetes Other: Blueberry Tea Not Applicable

Detailed Description:

Current treatments for T2D are limited, have unwanted side effects, and lose effectiveness over time. There is a growing public interest in the use of complementary and alternative approaches for treating insulin resistance and T2D. Blueberries, blueberry leaves and cinnamon have each been reported to improve insulin sensitivity or insulin action. Blueberry Boost™ is a locally produced Blueberry Tea and is a proprietary blend of dried blueberries (37% wt/wt), blueberry leaves, raspberry leaves, spearmint leaves and cinnamon.

It is well established that improving glycemic control is important for managing insulin resistance and T2D and the associated vascular pathologies that directly contribute to end-organ damage (microvascular disease), hypertension and cardiovascular disease (stroke, heart attack and heart failure). We have recently demonstrated that a unique blueberry tea blend fully restores the vascular insulin sensitivity in muscle of the high-fat fed insulin-resistant rat model and is associated with substantial improvements in muscle glucose uptake and whole body insulin sensitivity. We propose to translate these findings to assess the efficacy of this nutraceutical as a new treatment for improving glucose tolerance in people with T2D.

Aim: Determine whether chronic consumption (4 weeks) of blueberry tea can improve metabolic and vascular health in people with and without T2D.


Study Type : Interventional  (Clinical Trial)
Estimated Enrollment : 36 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)
Primary Purpose: Treatment
Official Title: Metabolic Benefits of Drinking Blueberry Tea in Type 2 Diabetes
Study Start Date : November 2015
Estimated Primary Completion Date : February 2018
Estimated Study Completion Date : February 2018

Resource links provided by the National Library of Medicine


Arm Intervention/treatment
Experimental: Blueberry Tea
3 cups of blueberry tea per day x 4 weeks
Other: Blueberry Tea
Blueberry Tea

No Intervention: No Treatment
No Treatment



Primary Outcome Measures :
  1. Improvement in Glucose Tolerance after 4 weeks of drinking blueberry tea. [ Time Frame: 4 weeks ]
    Oral glucose tolerance test (75g glucose) measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design). Blood glucose and plasma insulin levels measured at 0, 15, 30, 60, 90 and 120 min following consumption of glucose load.


Secondary Outcome Measures :
  1. Improvement in Hemoglobin A1c (HbA1c) levels after 4 weeks of drinking blueberry tea. [ Time Frame: 4 weeks. ]
    HbA1c levels measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).

  2. Improvement in fasting Serum Lipid (cholesterol, HDL, LDL,triglycerides) levels after 4 weeks of drinking blueberry tea. [ Time Frame: 4 weeks ]
    Fasting serum lipids (cholesterol, HDL, LDL,triglycerides) measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).

  3. Improvement in fasting serum pro-inflammatory cytokine (IL-6, IL-1b, CRP, TNFa) levels after 4 weeks of drinking blueberry tea. [ Time Frame: 4 weeks ]
    Fasting serum pro-inflammatory cytokines (IL-6, IL-1b, CRP, TNFa) assessed by ELISA will be measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).

  4. Improvement in fasting serum albumin levels after 4 weeks of drinking blueberry tea.. [ Time Frame: 4 weeks ]
    Fasting serum albumin levels measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).

  5. Fasting serum electrolytes (Na, K, Cl, HCO3). [ Time Frame: 4 weeks ]
    Fasting serum electrolytes (Na, K, Cl, HCO3) measured on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).

  6. Improvement in Resting Blood Pressure (central and brachial blood pressure) after 4 weeks of drinking blueberry tea. [ Time Frame: 4 weeks ]
    Blood Pressure (central and brachial blood pressure) will be measured by Mobil-O-Graph and assessed on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).

  7. Improvement in resting Augmentation Index after 4 weeks of drinking blueberry tea. [ Time Frame: 4 weeks ]
    Augmentation index will be measured by Mobil-O-Graph and assessed on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).

  8. Improvement in large artery stiffness after 4 weeks of drinking blueberry tea. [ Time Frame: 4 weeks ]
    Large artery stiffness will be measured by Mobil-O-Graph and assessed on 3 occasions: at baseline, after 4 weeks of drinking blueberry tea, and after 4 weeks of no treatment (randomized cross-over design).



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Ages Eligible for Study:   18 Years to 75 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • Aged 18-75 years.
  • Normal to overweight (BMI 19-35 kg/m2).
  • On lifestyle or metformin only diabetes treatment.
  • Normotensive (seated brachial blood pressure <140/90 mmHg).
  • No history of T2D (e.g. fasting plasma glucose <7.0mM); or with clinically diagnosed T2D on metformin or lifestyle intervention only (e.g. fasting plasma glucose ≥7.0mM, HbA1c).
  • Willing to drink blueberry tea for 4 weeks (3 times per day with meals).

Exclusion Criteria:

  • Age <18 yrs or >76 yrs
  • Morbidly obese with a BMI ≥36 kg/m2
  • Not on lifestyle and/or metformin only treatment for diabetes (e.g. insulin injections, sulphonylureas).
  • History of myocardial infarction or stroke
  • History of malignancy within past 5 years (except for non-melanoma skin cancers)
  • Current smoker
  • History of severe liver disease
  • History of drug or alcohol abuse
  • Elective major surgery during the course of the study
  • Pregnancy/lactation
  • Currently consuming (or have regularly consumed in the past 2 months) blueberry tea, or supplements containing blueberries, blueberry leaves, raspberry leaves, spearmint or cinnamon.
  • Participation or intention to participate in another clinical research study during the study period.
  • Not willing to consume blueberry tea for 4 weeks.

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT02629952


Contacts
Contact: Michelle A Keske, PhD +61 3 6226 2669 Michelle.Keske@utas.edu.au

Locations
Australia, Tasmania
Menzies Institute for Medical Research Recruiting
Hobart, Tasmania, Australia, 7000
Contact: Michelle A Keske, PhD    +61 3 6226 2669    Michelle.Keske@utas.edu.au   
Contact: Keske         
Sponsors and Collaborators
Menzies Institute for Medical Research
Investigators
Principal Investigator: Michelle A Keske, PhD Menzies Institute for Medical Research

Publications:
Responsible Party: Michelle Keske, Senior Research Fellow, Menzies Institute for Medical Research
ClinicalTrials.gov Identifier: NCT02629952     History of Changes
Other Study ID Numbers: H0014873
First Posted: December 15, 2015    Key Record Dates
Last Update Posted: September 13, 2017
Last Verified: September 2017
Individual Participant Data (IPD) Sharing Statement:
Plan to Share IPD: Undecided

Keywords provided by Michelle Keske, Menzies Institute for Medical Research:
glucose tolerance
type 2 diabetes
blueberry tea

Additional relevant MeSH terms:
Diabetes Mellitus
Diabetes Mellitus, Type 2
Glucose Metabolism Disorders
Metabolic Diseases
Endocrine System Diseases