Safety and Efficacy of Human Microbiota Transplantation for Overweight and Obese Type 2 Diabetes Mellitus

This is a randomized, double-blind, placebo-controlled study evaluating fecal microbiota transplantation from lean healthy donors to reduce the patients' weight. Patients wishing to participate will be evaluated whether they qualify for the study regarding the aforementioned inclusion and exclusion criteria. The details of the experiment and potential risks or discomforts involved in it will be presented, after which the patients will sign informed consent forms. In this study, patients will be randomly assigned to the experimental group and the control group in a 2:1 ratio according to a random allocation table. The table will be formulated on the basis of the random numbers generated by SPSS. The study will comprise of three parts: 1. Baseline - two weeks of run-in and screening period. * Ensure that each patient reads and signs informed consent. * Collect demographic data. * Ask about past medical history, current medical history, surgical history, allergy history, etc. * Ask about previous medication and combination medication. * Complete the FFQ questionnaire. * Collect information about vital signs, physical examination, BMI, ECG, conventional index and therapeutic effect index. * Collect 2 tubes of stool samples for fecal metagenomics sequencing and three tubes of blood samples for measuring serum metabolomics and inflammatory index (IL-6). * Review whether patients qualify for participate in the study according to the inclusion and exclusion criteria. * Dietitian will give diet, exercise lifestyle intervention guidance to patients. 2. FMT/ placebo intervention-patients will receive three interventions every two weeks. Four donors of any gender will be recruited for this study. Patients will receive 200ml FMT from donors with the same gender or receive the same amount of placebo FMT. FMT will be packaged in a 50ml sterile syringe or in an enema bag/surgical nutrition bag, the outer package of which will be affixed with the unique identifiable bar code label generated according to the biological specimen bank of the Department of Laboratory Medicine. The placebo FMT will be mainly composed of normal saline and glycerin and will be packaged in the same way as FMT. The night before receiving FMT or placebo FMT via nasointestinal tube, patients will go through proton pump inhibitors(oral 20mg esomeprazole or 40mg omeprazole). The end of the nasointestinal tube should reach at least the patient's duodenum, or reach the patient's jejunum if the patient cooperate. To prevent aspiration, the patient's upper body must maintain an upright posture of 45 degrees for 4 hours after the infusion. Before the first intervention, information about drug combination, vital signs, physical examination, BMI, body composition analysis and adverse events of patients will be collected, and advice of diet and lifestyle will be given to patients. Before the second intervention and before the third intervention, information about drug combination, vital signs, physical examination, BMI, renal function, liver function, blood fat, fasting blood glucose/C-peptide/insulin, body composition analysis and adverse events of patients will be collected, and advice of diet and lifestyle will be given to patients. 3. Follow-up meetings - total follow up of 6 weeks after FMT/placebo intervention. Meetings will occur 2 weeks and 6 weeks after the third intervention. During every follow-up meeting, information about drug combination, vital signs, physical examination, BMI, inflammatory biomarkers, renal function, liver function, blood fat, HbAlc, fasting blood glucose/C-peptide/insulin, 2-hour postprandial blood glucose/C-peptide/insulin, body composition analysis and adverse events of patients will be collected, and advice of diet and lifestyle will be given to patients. In the second follow-up meeting, there will be a fecal metagenomics sequencing and a serum metabonomics analysis.