Type 1 diabetes is condition in which progressive autoimmune destruction of insulin-producing beta-cells leads to absolute insulin deficiency. At the time of clinical presentation, it is estimated that 50-80% of beta-cell function has been lost. Good glycaemic control from diagnosis has been shown to preserve beta-cell function. The recent identification of immuno-interventions able to reduce autoimmune destruction and preserve beta-cell function has lead to an increased urgency to develop such tools.

With mixed-meal stimulated serum C-peptide being a gold standard, there are currently no tests that are suited for use in clinical practice to detect and monitor residual beta cell function. There is a therefore a need for a test that is sufficiently sensitive to assess beta cell function reserve in Type 1 diabetes for clinical practice purposes, which will be simple, reproducible and suitable for use even in the non-observed setting.

Using mixed meal stimulation of plasma C-peptide (stable by-product in insulin secretion that reliably reflects insulin production) response as a reference, we propose to compare mixed meal stimulated urinary C-peptide as potential candidate for this application. This is a pilot investigation in which a sample of 30 participants will be recruited.

It is anticipated that the current project will identify a simple method for analysing beta cell reserve in Type 1 diabetes. This will then be applied to screening clinic populations of recently diagnosed patients with type 1 diabetes. The aim will be to identify subjects who may be suitable for early intensified insulin regimes (e.g. insulin pump therapy) and novel immuno-intervention strategies designed to preserve residual beta cell function and improve long-term outcomes. Currently such immunointervention has been reserved for subjects within 3 months of diagnosis only, excluding a significant number of subjects who may potentially benefit.

Inclusion Criteria:1. 1. Type 1 diabetes diagnosed in the last 5 years 2. Age 18-45 years 3. BMI between 18.5 and 29.9 4. Insulin requirement less than 0.8 units/kg

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Exclusion Criteria:

1. HbA1c higher than 10% 2. Ongoing steroid treatment or chemotherapy 3. Pregnancy and breast feeding 4. eGFR less than 50ml/min/1.73m2

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Subjects with Type 1 diabetes diagnosed in the last 5 years