Effect of Probiotic Supplements on Metabolic Control of People With Type 2 Diabetes Mellitus in Greece

Eligible participants will be randomized using a computer generator (www.randomization.com), which randomizes each subject to a single treatment by using the method of randomly permuted blocks, to receive either a multi-strain probiotic supplement (in the form of a capsule [LactoLevure^R]) or a matching placebo capsule, once a day. The probiotic capsule contains the species: Lactobacillus Acidophilus, Lactobacillus plantarum, Bifidobacterium lactis, Saccharomyces boulardii (in the following quantities of colony-forming units [CFU]: Lactobacillus Acidophilus 1.75x10^9 CFU, Lactobacillus plantarum 0.5x10^9 CFU, Bifidobacterium lactis 1.75x10^9 CFU, Saccharomyces boulardii 1.5x10^9 CFU). The capsules (probiotics brand name LactoLevure^R and placebo) are prepared and donated to the study personnel by an unrestricted research grant from Uni-Pharma Greece, the producer of LactoLevure^R (Uni-Pharma Pharmaceutical Laboratories S.A., Kifisia, Greece), who will have no other interference with the planning, the conduction, or the analysis of the results of the study. The probiotic and placebo capsules will have an identical appearance and packaging. Neither the participants nor the investigators will be aware of the treatment assignments in this double-blinded study. Additionally, participants will be asked not to change their diet and exercise habits and to refrain from consuming yoghurt or other similar dietary supplements during the study. Care will be taken not to change the other pharmaceutical medicines during the study (participants who will have to initiate insulin treatment will be excluded from further follow-up and analysis in the study).

Sample size calculation will be based on previous similar studies considering 80% power at α = 0.05 to detect a difference in metabolic indices. All participants will be given verbal and written information about the study and will sign an informed consent form according to the recommendations of the Declaration of Helsinki.

Participants will be seen every 3 months in the outpatient Diabetes center of the Laiko General Hospital, National and Kapodistrian University of Athens Medical School, in Athens, Greece (as is customary for diabetic patients) and will be monitored regarding their glycemic control (HbA1c and fasting blood glucose), lipid parameters, liver and renal function, and anthropometric variables changes (weight and waist circumference, blood pressure). Furthermore, participants will be asked to give a stool sample at the study's beginning and end (6 months) for gut microbiota analysis. A questionnaire will also be administered at the last visit (6 months) asking about patients' tolerance and satisfaction with the treatment (frequency of constipation, diarrhea, bowel function, bloating, gas production, and abdominal pain).

Inclusion criteria

• T2D diagnosis of >6 months' duration
• Age 18-90 years
• A body-mass index (BMI) >18.5 kg/m^2
• HbA1c level >6 percent (%)
• on stable antidiabetic medications (oral or injectable glucagon-like peptide 1 receptor agonists [GLP-1 RAs]) for 8 weeks before the screening

Exclusion criteria

• Type 1 or other type of diabetes
• Pregnancy or wishing to become pregnant during the study
• End-stage kidney failure on dialysis, presence of other diseases, including cancer or severe hepatic insufficiency (transaminases >3.5x above normal)
• The use of other probiotic products or antibiotics over the previous 6 months
• Participation in other clinical trials
• Insulin administration
• The presence of other medical conditions that in the opinion of the investigators could jeopardize compliance with the protocol (e.g., malabsorption syndrome or an inability to take orally administered medications)