Intervention With a GABA Supplement in Prediabetics

Study Overview
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Brief Summary
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In this double-blind parallel placebo controlled intervention study the effects of 3 times daily 500 mg gamma-aminobutyric acid (GABA) supplementation on glucose tolerance and cardiovascular health will be assessed in prediabetics.

Official Title
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The Effects of a GABA Supplement Versus a Placebo on Glucose Tolerance and Blood Pressure in Prediabetics

Conditions
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Prediabetes, Hypertension

Intervention / Treatment
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* Dietary Supplement: GABA
* Other: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age between 50 and 70 BMI higher or equal to 27 kg/m2 Impaired fasting glucose (fasting glucose ≥ 6.1 and ≤ 6.9 mmol/L) or/and Impaired glucose tolerance (glucose levels ≥ 7.8 and ≤ 11.1 mmol/L, 2-hours after an OGTT or/and glucose levels ≥8.6 mmol/L, 1-hour after an OGTT) Exclusion Criteria: Has been diagnosed with diabetes Having other conditions, like liver, pancreatic, cardiovascular, gastro-intestinal or endocrine diseases, that could influence the study results Use of medications or supplements that could influence the study results Sensitive to medical skin adhesives More than 5kg weight change in the past 12 weeks Excessive alcohol consumption (>21 glasses/week for men and >14 glasses/week for women on average) Being an employee of Wageningen University, division Human Nutrition and Health Currently a research subject in other research

Ages Eligible for Study
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Minimum Age: 50 Years
Maximum Age: 70 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Randomized placebo controlled double blind parallel study design
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: GABA<br>GABA is a nutrient commonly present in our diet in for example tomatoes and potatoes. It is also commercially sold as dietary supplement. A dose of 500 mg, 3 times daily is used | Dietary Supplement: GABA<br>* The dietary supplement GABA will be taken orally 3 times daily, before each main meal<br>|
| Placebo Comparator: Placebo<br>The placebo consists of capsules containing powdered cellulose. | Other: Placebo<br>* Gelatin capsule containing powdered cellulose<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postprandial glycaemic response during a 2 hour oral glucose tolerance test (OGTT) | A 2 hour oral glucose tolerance test with 75gr glucose | blood will be drawn at baseline and after 30, 60 and 120 minutes, before and after the 12 weeks intervention | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postprandial insulin and glucagon response during a 2 hour OGTT, | A 2 hour oral glucose tolerance test with 75gr glucose | blood will be drawn at baseline and after 30, 60 and 120 minutes, before and after the 12 weeks intervention | 
| Plasma free fatty acids |  | before and after the 12 weeks intervention | 
| HbA1c |  | before and after the 12 weeks intervention | 
| Glucose variability | The participants wear a flash glucose monitoring sensor with which their interstitial glucose is measured every 15 minutes. | 5 days during which they eat their habitual diet, before and after the 12 weeks intervention | 
| Blood pressure | Single measurement and a dynamic measurement: Mean day systolic and diastolic blood pressure Mean night systolic and diastolic blood pressure Time below or above 120/80 mmHg | Dynamic measurement: 24 hours, before and after the 12 weeks intervention | 
| Heart rate |  | before and after the 12 weeks intervention | 
| Concentrion of markers of inflammation in blood | C-reactive protein and cytokines like IL-6 and TNF-alpha | before and after the 12 weeks intervention | 
| Concentration of triglycerides in blood |  | before and after the 12 weeks intervention | 
| Concentration of LDL and HDL cholesterol in blood |  | before and after the 12 weeks intervention | 
| Concentration of ALAT and ASAT in blood |  | before and after the 12 weeks intervention | 
| Acute effects of GABA on postprandial glucose | Assessed with an OGTT during which interstitial glucose is measured with flash glucose monitoring | 2 hours, after a single administration of 500 mg GABA | 
| Acute effects of GABA on blood pressure | Assessed with an ambulatory blood pressure monitor | for 24 hours during which GABA is taken 3 times, each time before the main meal | 
| Sleep quality | Pittsburgh Sleep Quality Index (PSQI) questionnaire, the outcome is a global PSQI score (range: 0-21), with higher scores indicating poorer sleep quality. | before and after the 12 weeks intervention | 
| Feelings of depression | Patient Health Questionnaire (PHQ-9), the higher the score the more depressed a person is. | before and after the 12 weeks intervention | 
| Feelings of anxiety | General Anxiety Disorder (GAD-7) questionnaire, the higher the score, the more anxious a person is. | before and after the 12 weeks intervention | 
| Plasma GABA concentration |  | before and after the 12 weeks intervention | 
| Plasma glutamate concentration |  | before and after the 12 weeks intervention |