The investigators will evaluate the stool microbiota, serum and fecal bile acid composition, and changes in blood glucose and lipid profile before and after one month of metformin or YH1 treatment.

Inclusion Criteria:

1. Treatment-naïve male patients with type 2 diabetes;
2. Aged 20-65 years;
3. Body mass index (BMI) ≥ 24 kg/m2; 4.7 % ≤ glycated hemoglobin (HbA1c) < 9 %;

5.Low-density cholesterol (LDL-C) ≥ 130 mg/dl; 6.Expected to receive metformin 500 mg tid or YH1 6g tid for one month

Exclusion Criteria:

1. type 1,or other specific types of diabetes;
2. female;
3. history of oral hypoglycemic agents (OHAs) treatment or insulin therapy;
4. use of lipid-lowering drugs within the past six months;
5. serious gastrointestinal (GI) tract diseases, including peptic ulcers and GI tract bleeding;
6. hepatic insufficiency with ALT >72 U/L or renal insufficiency with an eGFR < 60 mL/min/1.73 m2;
7. history of stressful situations, including diabetic ketoacidosis, nonketotic hyperosmolar diabetic coma, infectious disease, or surgery in the previous month;
8. mental illness;
9. current smoking status, alcohol or drug abuse;
10. hemoglobin disease or chronic anemia;
11. underlying conditions that could lead to poor compliance;
12. severe organic diseases, including cancer, coronary heart disease, myocardial infarction or cerebrovascular disease;
13. continuous antibiotic or probiotics use for over 3 days within 3 months prior to enrollment;
14. continuous use of weight loss drug for over 1 month;
15. history of YH1 therapy, or Chinese medicine treatment within the past one month.

Outpatients and treatment-naïve male patients with type 2 diabetes