The Effect of Whole Grain on Gut Microbiome and Metabolic Health

Study Overview
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Brief Summary
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Objective: To identify how specific changes of the whole grain content in the diet affect the host-gut microbiome interactions with implications for metabolic health . Design: A randomized, controlled, single-blinded, cross-over intervention trial consisting of two 8-week intervention periods, separated by a 6-week wash-out period. A total of 60 participants will be included. Intervention: low vs. high whole grain intake.

Detailed Description
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The study is designed as a randomized, controlled, single-blinded, cross-over intervention trial consisting of two 8-week interventions periods, separated by a 6-week wash-out period. A total number of 60 participants will be included. Participants consume, in randomized order, a diet rich in whole grain in the active treatment period and a refined grain diet during the control period. Measurements: Insulin sensitivity will be assessed by means of a meal challenge test and by the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) which is the primary outcome of this study. Secondary outcomes include metabolic and inflammatory markers, appetite hormones, transit time, and GM composition. Furthermore, selected control measures are included; 4-day food records and a study intervention diary.

Official Title
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Gut, Grain and Greens (3G): The Effect of Wholegrain on Gut Microbiome and Metabolic Health

Conditions
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Metabolic Disease, Injury of Gastrointestinal Tract

Intervention / Treatment
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* Other: Whole grain
* Other: Refined grain


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Body mass index (BMI): 25 - 35 kg/m2 No medical prescribed diet Weight stable No blood donation during the study Intense sporting activities less than 10h/ week Alcohol consumption less than 14 units/ week (female) and 21 units/ week (male) Signed written consent Exclusion Criteria: Pharmacological treatment; hypertension, diabetes and blood lipid regulation Lactating (or lactating, 6 weeks ago), pregnant (or pregnant, 3 months ago) or wish to become pregnant during the study Participation in another biomedical trial 1 month prior to study start Diagnosed with any form of diabetes, celiac disease or chronic pancreatitis Reported chronic gastrointestinal disorders Antibiotic treatment for 3 month prior to study start Intake of vitamin, mineral, or pre- or probiotic supplements for 1 month prior to study start Blood hemoglobin < 7.0 mmol/l Blood donation within 1 month prior to study start

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 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

Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Placebo Comparator: Refined grain<br>Refined grain diet: Participants consume less than 10 g of whole grain per day (corresponds to the whole grain intake below the 10th percentile of the population) | Other: Refined grain<br>* Refined grain diet: Participants consume less than 10 g of whole grain per day (corresponds to the whole grain intake below the 10th percentile of the population)<br>|
| Active Comparator: Whole grain<br>Whole grain diet: Participants consume more than 75g of whole grain per day (corresponds to the whole grain intake of the 90th percentile of the population) | Other: Whole grain<br>* Whole grain diet: Participants consume more than 75g of whole grain per day (corresponds to the whole grain intake of the 90th percentile of the population)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| HOMA-IR | Homeostasis Model Assessment of fasting Insulin Resistance (HOMA-IR: glucose (mmol/l( x insulin (pmol/l)/22.5) | At the end of the intervention periods | 
| Metagenomic profile | Altered quantitative metagenomics at bacterial gene- and species levels, which is a non-specific outcome, but included as the main hypothesis of the project is to test if HOMA-IR is affected via changes in the gut microbiome. | At the end of the intervention periods | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Mean intestinal transit time | Participants are instructed in swallowing capsules containing different small non-invasive and non-absorbable plastic pellets for 6 consecutive days. On the seventh day they are having an X-ray of the abdomen taken. | At the end of the intervention periods | 
| Gastrointestinal permeability, Lactulose/ mannitol ratio | 5 hours urine collection following intake of lactulose and mannitol | At the end of the intervention periods | 
| Colonic fermentation | Measurement of breath hydrogen excretion (at before and 30, 60, 90, 120, 150, 180 after intake of standard breakfast) and plasma short-chain fatty acids (fasting and 30, 60, 120, 180 minutes after standard breakfast) | At the end of the intervention periods | 
| Saliva microbial flora | Determination of fasting microbial composition of flora. | At the end of the intervention periods | 
| Blood pressure | Measurement of supine systolic and diastolic blood pressure (3 times) | At the end of the intervention periods | 
| Appetite hormones | Determination of different appetite hormones in fasting and postprandial blood samples (30, 60, 120, 180 minutes after standard breakfast) | At the end of the intervention periods | 
| Blood lipid profile | Measurement of different blood lipids in fasting and postprandial blood samples (30, 60, 120, 180 minutes after standard breakfast) | At the end of the interventions periods | 
| Body composition | Measurement of body fat mass and percentage via bio-impedance | At the end of the intervention periods | 
| Subjective appetite sensation | Assessment of subjective appetite sensation via visual analogue scales | At the end of the intervention periods | 
| Energy intake | Assessment of energy intake at an ad libitum meal 3 hours after a standard breakfast | At the end of the intervention periods | 
| Ex vivo cytokine production | Production of cytokines (such as IL-1beta, IL-6) in stimulated whole blood cultures. | At the end of the intervention periods | 
| Gene expression | Assessed by mRNA qPCR in whole blood and cells from whole blood stimulation. Main focus is put on genes involved in immune function and metabolic regulation. | At the end of the intervention periods | 
| Immune cell profiling | Assessed by flow cytometry of whole blood. | At the end of the intervention periods | 
| Immune markers | Fasting plasma cytokines, hsCRP, and LPS/LPS-BP | At the end of the intervention periods | 
| Blood immune cell content | Assessed by hematological cell counts | At the end of the intervention periods | 
| Markers og glucose hemostasis | Measurement of plasma concentrations of Insulin, Proinsulin and HbA1c | At the end of the intervention periods | 
| Markers of one-carbon metabolism | Assessed by plasma homocystein, SAM/SAH and betain | At the end of the intervention periods | 
| Plasma adipokines | Leptin and adiponectin | December 2015 |