This clinical trial is designed to evaluate the alteration of gut microbiome in healthy subjects after a 12-week metformin and/or probiotics administration.

Gut microbiome dysbiosis have been linked with the onset and progression of several diseases. Metformin and probiotics have been confirmed to function partly by regulating the gut microbiome. The investigators are now wondering if metformin/probiotics treatment will change the gut microbiota in healthy subjects and show some benefits.

In this study, about 60 healthy subjects will be enrolled. Participants will be randomly assigned into one of the following three groups: Metformin powder (0.5g tid po), Probiotics powder (0.5g tid po), Placebo powder (0.5g tid po), for 12 weeks.

Blood and stool samples will be collected before and after treatment. Fasting glucose levels, fasting insulin levels, serum lipid profiles, inflammation markers and alteration of gut microbiota will be evaluated.

Inclusion Criteria:

1. Between 20-60 years of age.
2. Healthy subjects without known diseases.

Exclusion Criteria:

1. During pregnancy and lactation period.
2. Impaired liver function, impaired renal function, mental disease, severe infection, severe anemia, severe heart disease and neutropenia disease.
3. Use of metformin/antibiotics within 3 months.
4. Immunodeficient or use of immunosuppressive drugs.
5. Previous history of gastrointestinal surgery or diseases (such as peptic ulcer, irritable bowel syndrome, inflammatory bowel disease or other gastrointestinal disorder).
6. Medical conditions or diseases that may affect subject safety or confound study results in the opinion of the investigator.