Overview

This study is a prospective, single-center, parallel-design,1:1 randomized controlled trial with triple blinding. It aims to investigate the effects of fecal microbiota transplantation (FMT) on cognitive function in patients with long-term type 1 diabetes (T1D), as well as its effects on other complications, glycemic control, insulin dosage, insulin resistance, peripheral blood immune cells, serum metabolites, and safety. This study is divided into two phases for recruiting participants. The first phase recruits 10 individuals (experimental group: 5, control group: 5), while the second phase recruits 30 individuals (experimental group: 15, control group: 15).The main research objectives are as follows:

1. To observe the difference in cognitive function between the FMT group and the placebo group, with the indicators including cognitive scale scores, changes in brain MRI imaging indicators and brain age at week 24 compared to baseline.
2. To observe the difference in other complications between the FMT group and the placebo group, with the indicators including changes in urinary albumin/creatinine ratio, fundus photography, carotid intima-media thickness, and arterial pulse wave velocity at week 24 compared to baseline.
3. To observe the difference in glycemic control, insulin dosage, insulin resistance, peripheral blood immune cells, gut microbiota, and serum metabolites between the FMT group and the placebo group.
4. To evaluate the safety of FMT.

Eligibility

Inclusion Criteria:

1. According to the definition of type 1 diabetes mellitus (T1DM) by the World Health Organization (WHO), the diagnostic criteria are as follows: (i) clinically diagnosed as T1D by endocrinologists; (ii) insulin dependence from disease onset and diabetic ketoacidosis (DKA)/diabetic ketosis (DK) at diagnosis; (iii) positive for at least one of islet autoantibodies for glutamic acid decarboxylase antibody [GADA], insulinoma-associated protein 2 antibody [IA-2A], and zinc transporter 8 antibody [ZnT8A]; or negative for all three islet autoantibodies, but diagnosed before age 30.
2. Age between 18 and 60 years, with a diabetes duration of 10 years or more
3. Glycated hemoglobin levels ranging from 6.5% to 9.0%.

Exclusion Criteria:

1. Use of any hypoglycemic medication other than insulin in the two months prior to randomization.
2. Participation in other clinical trials within the two months prior to randomization.
3. Use of antimicrobial drugs, probiotics, intestinal microbiota regulators, and other drugs with significant impact on gut microbiota within the two months prior to randomization.
4. Gastrointestinal diseases: celiac disease, irritable bowel syndrome, Crohn's disease, etc.
5. Severe infections, severe heart, liver, kidney diseases, tumors, and other inflammatory or autoimmune diseases.
6. Pregnant or lactating women, or women planning pregnancy during the study period.
7. Severe mental health disorders such as schizophrenia, major depression, bipolar disorder, alcohol or substance abuse, etc.
8. Neurological disorders such as Parkinson's disease, progressive supranuclear palsy, epilepsy, multiple sclerosis, traumatic brain injury, stroke, etc.
9. Post-implantation of metal materials or contraindications for other MRI examinations.
10. Severe episodes of unconscious hypoglycemia within the past two months.