Defining the Decline in Endogenous Insulin Secretion in Type 1 Diabetes Diagnosed After 30 Years of Age.

Study Overview
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Brief Summary
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The study aims is to find out if people with type 1 diabetes diagnosed in later life (after age 30) have the same rapid loss of insulin secretion (measured using C-peptide) that occurs in younger adults with type 1 diabetes. The investigators will recruit 135 participants aged over 30 years with a clinical diagnosis of type 1 diabetes and diabetes duration ≤100 days. The investigators will also recruit a comparison group of 61 participants aged 18-30 with a clinical diagnosis of type 1 diabetes and diabetes duration ≤100 days. C-peptide will be measured during mixed meal tolerance tests (MMTT) performed at baseline, 6 months and a year. This study also aims to test a new more practical way of monitoring insulin secretion at home using a finger prick 'blood spot' rather than time consuming tests in a hospital. Finger-prick C-peptide samples will be collected after the MMTT and by the participants at home throughout the year.

Detailed Description
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The study aims to evaluate progression of type 1 diabetes. Primary analysis will be conducted on those with >=1 diabetes autoantibody positive (GAD, IA2 ZNT8). Sensitivity analysis will be performed by repeating all analysis defining T1D as a) double antibody positivity and b) single antibody positivity combined with a high genetic risk score for T1D (T1DGRS>5th centile of a control population). Further aims will be to evaluate the utility of dried blood spot testing to detect change in C-peptide and the utility of home test results as a marker of hypoglycaemia and glucose variability.

Official Title
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Defining the Decline in Endogenous Insulin Secretion in Type 1 Diabetes Diagnosed After 30 Years of Age.

Conditions
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Diabetes Mellitus, Type 1, Progression

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Adults with a clinical diagnosis of Type 1 diabetes within the previous 100 days. Aged >30 at the time of Type 1 diabetes diagnosis OR (additional early onset Type 1 diabetes cohort) aged ≥18 and ≤30 at the time of Type 1 diabetes diagnosis. Insulin treated at the time of recruitment Able and willing to provide informed consent. Exclusion criteria Pregnancy Known monogenic diabetes Known secondary diabetes (diabetes considered likely due to medication, cystic fibrosis, pancreatitis, pancreatic cancer, pancreatic surgery, hemochromatosis or Cushing's syndrome).

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Late Onset<br>Participants diagnosed with Type 1 diabetes at over 30 years of age. | |
| 18 to 30<br>Participants diagnosed with Type 1 diabetes between 18 and 30 years of age | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| C-peptide value at a year | 12 month (Mixed Meal Tolerance Test) MMTT area under the curve (AUC) C-peptide. | 12 months | 
| Change in C-peptide over a year | Rate of change of MMTT AUC C-peptide over 12 months assessed at regular study visits | 12 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| C-peptide value at 12 months | Mean C-peptide at 12 months assessed using MMTT and home blood samples | 12 months | 
| Glucose variability & hypoglycemia | Glucose variability & hypoglycemia as measured by continuous glucose monitoring (CGM) | 12 months | 
| Change in dried blood spot C-peptide | Rate of change in home dried blood spot C-peptide over 12 months | 12 months |