The purpose of this study is to determine the effect of a commercial dietary fiber supplement on patients with type 2 diabetes mellitus, in the way of glucose control, insulin action in the body, and the gut microbiota (bacteria) abundance.

Fiber supplements such as psyllium are known to be beneficial to glycemic control in patients with type 2 diabetes mellitus (T2DM). Gut microbiota has a role in regulating host energy metabolism and systemic inflammation by several pathways such as short-chain fatty acid production, fasting-induced adipose factor expression, endocannabinoid system, and gut epithelial permeability. As dietary components can influence the composition of the microbiota, we hypothesized that fiber supplements could modify gut microbiota and consequently affect glycemic control and inflammatory condition in patients with T2DM.

The primary outcome was to assess the effect of fiber on glucose control (by comparing fasting glucose and glycoalbumin), insulin secretion and sensitivity. Secondary outcomes were the changes abundance of microbiota, incretins, and lipopolysaccharide (LPS).

Inclusion Criteria (all of the followings):

• Among type 2 diabetic patients who visit Diabetes Center at Samsung Medical Center

• 2 or more of following are required:

  1. use of lipid-lowering drugs and / or triglyceride ≥ 150 mg/dL, high-density lipoprotein < 40 mg/dL in men and < 50 mg/dL in women
  2. waist circumference > 90 cm in men and > 80 cm in women
  3. antihypertensive medication and / or blood pressure ≥ 130/85 mmHg

• Hemoglobin A1c level 7.0 - 9.0% (6.5 - 9.0% in age 50-60 years old)

• Patients who are treated with combination therapy of sulfonylurea and metformin at least 6 months and in steady-glucose-controlled state.

Exclusion Criteria (at least one of the followings):

• Patients using insulin, alpha-glucosidase inhibitor, meglitinide, thiazolidinedione, or incretin agent (both oral or injectables)
• Recently diagnosed (within 6 months) acute diabetic complication such as diabetic ketoacidosis and hyperosmolar hyperglycemic state
• Clinically significant cardiovascular disease
• Patients treated with oral or intravenous antibiotics last 12 months
• Patients who took fiber supplements last 6 months
• Fasting serum c-peptide level < 1 ng/mL
• Duration of type 2 diabetes > 10 years