The goal of DIATAG study is the identification of biomarkers of T1D evolution in a pediatric cohort.

Type 1 diabetes (T1D) is a common chronic disease in childhood. Clinical presentation at onset of T1D can vary among patients from long-standing diabetes triad symptoms (polyuria, polydipsia and weight loss) to coma and ketoacidosis. The initial clinical presentation of T1D was shown to have long-term influence on glycemic control of the patient. The investigators initiated a collaborative consortium including six pediatric clinics in Belgium to better characterize new-onset T1D patients.

Hypothesis :

1. Different subgroups of T1D patients might exist, underlying different physiopathology of T1D :

   • The investigators will first investigate the presence of biomarkers in different fluids (e.g. urine, blood, feces,...).
   • The investigators will correlate results with clinical parameters of glycemic control. Dynamic tests (HOMA and stimulated C peptide) will be realized at 2 defined time points of the follow-up.

2. Glucose variability can be influenced by external factors (e.g. diet, physical activity, Quality of Life (QoL),...) The investigators will evaluate those external factors using approved questionnaires. They will presented to the patient and its parents at 2 defined time points.

Inclusion Criteria:

1. Type 1 diabetes de novo according to American Diabetes Association criteria:

   1. Polyuria, polydipsia, weight loss ± ketoacidosis
   2. Fasting blood glucose ≥126 mg/dL AND/OR blood glucose ≥200 mg/dL at the 120th minute of an Oral Glucose Tolerance Test (OGTT) AND/OR HbA1c ≥6.5% AND/OR a patient with symptoms of hyperglycemia/hyperglycemic crisis (see 8. a. 2.) with random blood glucose ≥200 mg/dL.
   3. Presence in the serum of one or more anti-islet autoantibodies (anti-insulin, anti-IA2, anti-GAD65, anti-ZnT8)

2. Age between 6 months and 18 years.

3. Male or female.

4. Positive for one or more autoantibodies typically associated with Type 1 Diabetes (TD1).

5. Free written and oral consent.

Exclusion Criteria:

1. Children under 6 months of age.
2. Treatment that interferes with insulin secretion and insulin sensitivity (e. g. sulfonylureas, diazoxide, somatostatin, methylxanthine derivatives, corticosteroids, biguanide, incretins).
3. Presence of celiac disease (diagnosis based on pathological duodenal biopsy), recently diagnosed (within 1 month), at the time of inclusion.
4. Autoimmune/auto-inflammatory disease (other than type 1 diabetes) or active malignant disease present at inclusion.
5. Obesity defined by a Body Mass Index (BMI) with a z-score >+3 Standard Deviation.
6. Hepatic, renal or adrenal insufficiency.
7. History of spinal cord allograft.
8. History of post-hemolytic-uremic diabetes.
9. Absence of anti-pancreatic islet auto-antibodies.
10. Dysmorphic with suspicion of underlying genetic syndrome.
11. Participation in another study within the previous 3 months, with administration of blood derivatives or potentially immunomodulating treatments.