Impact of Consumption of Beta-glucans on the Intestinal Microbiota and Glucose and Lipid Metabolism

Impact of Consumption of Beta-glucans on the Intestinal Microbiota and Glucose and Lipid Metabolism in a Population With Metabolic Syndrome

The purpose of this study is to investigate if daily consumption of barley beta-glucans effect lipid and glucose metabolism and alter intestinal microbiota composition in participants with metabolic syndrome or with high risk for metabolic syndrome development. It is assumed that 4-week intervention with beta-glucans will improve some clinical signs of metabolic syndrome and alter composition of intestinal microbiota. Variation in microbiota composition will be investigated with emphasis on Bacteroidetes and Firmicutes ratio. Furthermore it is presupposed that consumption of beta-glucans will stimulate growth of beneficial intestinal bacteria from genus Lactobacillus and Bifidobacteria and consequently effect production of short chain fatty acids in population with metabolic syndrome. Moreover it is presupposed that 4-week consumption of beta-glucans will have influence on glucose metabolism and will consequently improve insulin resistance within people with metabolic syndrome or high risk for metabolic syndrome development. It is assumed that 4-week consumption of beta-glucans will improve specific plasma lipid content in population with metabolic syndrome.

In study it will be investigated whether daily consumption of barley beta-glucans integrated in bread product effects lipid and glucose metabolism and alter the composition of intestinal microbiota in a population with metabolic syndrome or with high risk for metabolic syndrome development. 70 participants with metabolic syndrome will be enrolled in study. Participants will daily consume 200 g of bread with high amount of beta-glucans. Hypothesis: 4- week consumption of beta-glucans alters composition of intestinal microbiota and changes ratio of bacteria from phylum Bacteroidetes and Firmicutes. Furthermore consumption of beta-glucans stimulates growth of beneficial intestinal bacteria from genus Lactobacillus and Bifidobacteria and consequently effects production of short chain fatty acids in population with metabolic syndrome. 4- week consumption of beta-glucans has influence on glucose metabolism and consequently improves insulin resistance within people with metabolic syndrome. 4 - week consumption of beta-glucans improves specific plasma lipid content in population with metabolic syndrome. Study will be designed as double blind, randomised, placebo controlled clinical trial and performed regarding to CONSORT 2010 recommendations for randomised clinical trials. Patient enrollment will be performed in several community health centres in Slovenia in association with family medicine doctors. Appropriate patients with metabolic syndrome or with high risk for metabolic development will be suggested to participate in clinical trial. Candidates will be suggested to participate in a two month study. If there will not be recruited enough participants for two month study they will be suggested for participation in one month study. Candidates interested in participating in study will be informed about study design and terms and conditions of study by main investigator. Study will be performed after successful recruitment of first 20 or more participants. Study will be performed three times, so that 70 participants will be recruited in complete study. Participants will consume bread with high beta-glucans content (around 3, 4 g beta-glucans per 100 g of bread) during 8 or 4 week period. Before beginning of study participants will have two week washout period without consuming any pre- and pro-biotics. They will remain their usual eating habits during study period except taking any antibiotics or pre- and pro-biotic. Participants will give blood and stool samples a day before intervention with barley beta-glucans. Blood sampling will involve oral glucose test for insulin resistance determination and sampling for specific lipid content determination. They will also have option to give a blood sample for genetic investigation of genes associated with lipid metabolism (apoE). Blood and stool sampling will be repeated day after intervention period. The same parameters as before intervention period except genetic analysis will be investigated. 72-hour dietary recall will be performed during intervention period individually to evaluate daily nutrient and energetic input of each participant.

Metabolic syndrome, 4 -week intervention, Randomised placebo controlled parallel study, Beta-glucans, Abdominal fat, Dyslipidemia, Insulin resistance, Hypertension, Gut Microbiota Composition, Oral Glucose Tolerance Test, Lipid Profile, Real-Time Polymerase Chain Reaction, Denaturating Gradient Gel Electrophoresis

Experimental food is bread with high amount of barley beta-glucans. Experimental bread contains approximately 3,4 % (w/w) beta-glucans. Participants will consume 6 g of beta-glucans daily (approximately 200 g of bread per day). Beta-glucans are natural polysaccharides found in grain endosperm and are mostly represented in oat and barley. Beta-glucans are linear homopolymers of D- glycopyranosyl residues with mixed linkage (1-4, 1-3)-β-D-glucans. Their molecular structure enable beta-glucans their functional action that mostly depends of their viscosity and solubility (1). Testing bread has integrated flour with high amount of barley beta-glucans (ReducholTM). Beta-glucans are concentrated in flour up to 15 % with dry milling, sieving and air classification of barley flour.

Participants will daily consume bread with high content of beta-glucans. They will approximately consume 6 g beta-glucans per day in 200 g of bread. Intervention period will be 4 weeks. Meanwhile the participants will remain their usual eating habits except consuming any pro- or pre-biotics

Participants will daily consume placebo bread without any added beta-glucans (approximately 200 g per day). Intervention period will be 4 weeks. Meanwhile the participants will remain their usual eating habits except consuming any pro- or pre-biotics.

Fecal sampling for microbiologic analysis of microbiota composition: Composition of intestinal microbiota will be determined with a combination of two molecular techniques denaturating gradient gel electrophoresis (DGGE) and quantitative real time PCR (RT-PCR).

Oral Glucose Tolerance Test (OGTT) for Insulin Resistance Determination (Outcome Measures of Plasma Insulin Concentrations)

Pharmacokinetic outcome measures: Determination of insulin resistance with OGTT testing. Before and after oral consumption of 75 g of glucose, plasma insulin concentrations were measured at following times: 0 min - before oral consumption of 75 g glucose 30 min, 60 min and 120 min - after oral consumption of 75 g glucose

Oral Glucose Tolerance Test (OGTT) for Insulin Resistance Determination (Outcome Measures of Plasma Glucose Concentrations)

Pharmacokinetic outcome measures: Determination of insulin resistance with OGTT testing. Before and after oral consumption of 75 g of glucose, plasma glucose concentrations were measured at following times: 0 min - before oral consumption of 75 g glucose 30 min, 60 min and 120 min - after oral consumption of 75 g glucose

Before the intervention, systolic and diastolic blood pressure were measured. Measurement was performed to obtain parameters for metabolic syndrome definition. Measurements after dietary intervention weren't performed.

Fecal sampling for SCFA determination: Content of specific SCFA (butyric acid, acetic acid and propionic acid) will be determined in fecal samples using Gas Chromatography.

Before the diet intervention, triglyceride levels were measured in test (consuming bread with added beta glucans) and in control group (consuming bread without added beta glucans).

Fecal sampling for microbiologic analysis of microbiota composition: Composition of intestinal microbiota will be determined with a combination of two molecular techniques denaturating gradient gel electrophoresis (DGGE) and quantitative real time PCR (RT-PCR).

Fecal sampling for SCFA determination: Content of specific SCFA (butyric acid, acetic acid and propionic acid) will be determined in fecal samples using Gas Chromatography.

After the diet intervention, triglyceride levels were measured in test (consuming bread with added beta glucans) and in control group (consuming bread without added beta glucans).

Oral Glucose Tolerance Test (OGTT) for Insulin Resistance Determination (Outcome Measures of Plasma Glucose Concentrations)

Pharmacokinetic outcome measures: Determination of insulin resistance with OGTT testing. Before and after oral consumption of 75 g of glucose, plasma glucose concentration measurements were performed at following times: 0 min - before oral consumption of 75 g glucose 30 min, 60 min and 120 min - after oral consumption of 75 g glucose

Oral Glucose Tolerance Test (OGTT) for Insulin Resistance Determination (Outcome Measures of Plasma Insulin Concentrations)

Pharmacokinetic outcome measures: Determination of insulin resistance with OGTT testing. Before and after oral consumption of 75 g of glucose, plasma insulin concentration measurements were performed at following times: 0 min - before oral consumption of 75 g glucose 30 min, 60 min and 120 min - after oral consumption of 75 g glucose

Inclusion Criteria are parameters used for metabolic syndrome determination according to International Diabetes Federation (IDF) consensus worldwide definition of Metabolic Syndrome: Participant must have central obesity: defined as waist circumference ≥ 80 cm for European woman and ≥ 94 cm for European men. Beside central obesity candidates participating in this study must have total cholesterol concentration ≥ 5 mmol/l before entering the study. Plus any two of the following four factors: HDL-cholesterol content: man ≤ 1,03 mmol/, women ≤ 1,23 mmol/l Triglycerides content ≥ 1,7 mmol/l Fasting blood glucose ≥ 5,6 mmol/l Hypertension: systolic blood pressure ≥ 130 mm Hg and diastolic blood pressure ≥ 85 mm Hg If participant will have diagnosed metabolic syndrome and meet age criteria will be included in study. Exclusion Criteria: Diabetes type II Thyroid disorder Kidney disorder Antibiotic treatment

(1) Izydorczyk MS,Dexter JE. Barley beta-glucans and arabinoxylans: Molecular structure, physicochemical properties, and uses in food products-a Review. Food Research International 41: 850-868, 2008