To elucidate the characteristics of global gut microbiota and fecal/serum metabolites in patients with childhood-onset type 1 diabetes, adult-onset type 1 diabetes or type 2 diabetes.

Type 1 diabetes is caused by autoimmune destruction of pancreatic beta cells, leading to severe insulin deficiency and requiring insulin therapy. It is typically considered a disease of childhood and adolescence, but recent epidemiological data have shown that over half of all new-onset type 1 diabetes cases occur in adults worldwide. There are genetic, immune and metabolic differences between adult- and childhood-onset type 1 diabetes, revealing the underlying molecular basis of type 1 diabetes onset at diverse ages may differ. Accurate diagnosis is of great importance because the best treatment for different types of diabetes is divergent. Misdiagnosing type 2 diabetes as type 1 diabetes can lead to unnecessary initial insulin therapy, resulting in higher costs and more side effects. Thus, it is critical to identify the molecular basis and new diagnostic biomarkers for adult-onset type 1 diabetes.

Nonetheless, environmental exposures, in particular the immense intestinal microbiota and its derivatives, have been widely investigated. Indeed, patients with childhood-onset type 1 diabetes or type 2 diabetes exhibit compositional alterations in gut microbiota. However, gut microbiota in adult-onset type 1 diabetes has not been elucidated, and little is known about the shared and distinct microbial characteristics in adult-onset type 1 diabetes versus childhood-onset type 1 diabetes or type 2 diabetes.

Thus, this study is a cross-sectional study. 4 groups of subjects were recruited for metagenome and metabolome analysis, including healthy controls and patients with childhood-onset type 1 diabetes, adult-onset type 1 diabetes or type 2 diabetes. All subjects recruited meet the inclusion or exclusion criteria and written informed consent was obtained from each participant at enrollment.

Inclusion Criteria:

1. Diabetes diagnosed according to the report of WHO in 1999；
2. Aged between 5 and 70 years old;

Exclusion Criteria:

1. Severe chronic cardiovascular or cerebrovascular disease；
2. Severe abnormalities in liver or renal function;
3. Hyperthyroidism; or other autoimmune diseases;
4. Tumors, surgery or pregnancy;
5. Treatments with oral hypoglycemic agents or immunomodulators;
6. Subjects who had taken probiotics, prebiotics within one week or antibiotics within one month.

Patients with childhood-onset type 1 diabetes, adult-onset type 1 diabetes or type 2 diabetes. Healthy conrols recruited at the Second Xiangya Hospital of Central South University in Changsha.