Type 1 Diabetes, Immunology, Genetics & Endogenous Insulin Production

Background \& Introduction:

Type 1 Diabetes (T1D) is a disease caused by the autoimmune destruction of pancreatic beta cells. It commonly presents in childhood with elevated blood sugars and long-term insulin treatment is required. People diagnosed with T1D have some pancreatic beta cells remaining at diagnosis and these remaining insulin producing cells were thought to be lost within the first few months or years after diagnosis. The underlying mechanism for destruction of beta cells is T-cell driven autoimmunity with genetic, environmental and immune associations that point towards the immune system as being the key to pancreatic beta cells loss. Extensive research has focussed on trying to prevent, halt or reverse immune attack in T1D using immunosuppression or immunomodulation with a variety of drugs and vaccines. These efforts have been largely unsuccessful and demonstrate that although we know that autoimmunity is critical to the development of T1D we still do not know enough about specific mechanisms to successfully stop this process. By better understanding the role of the immune system in T1D, this may ultimately lead to better treatments or reversal of T1D.

Contrary to conventional understanding, not all people with T1D lose insulin production soon after diagnosis. Modern assays that can detect low levels of endogenous insulin have shown that many people with T1D make low levels of insulin for many years after diagnosis. There are also a smaller group of patients who make significant amounts of insulin despite having T1D for many years. Conversely, there are some patients who seem to lose all endogenous insulin very quickly after diagnosis.

Urine C-peptide Creatinine ratio is a new technique that allows assessment of endogenous insulin production in a urine sample that is posted from home. This has allowed the assessment of insulin production in over 1000 patients with T1D in the South West of England with identification of patients still making significant amounts of insulin after years of T1D, and other patients who have lost insulin production very rapidly.

Retained endogenous insulin production may represent a slower autoimmune process, with a dampening of the immune response by regulation within the autoimmune system (tolerance), or a "burning out" of the process of autoimmunity as can happen in some other autoimmune diseases. Similarly, very rapid loss of insulin production may represent the opposite, more aggressive end of the spectrum.

We aim to study this by comparing immunological characteristics of patients with T1D, with a range of diabetes duration, and still making significant insulin with similar groups who are making none.

Hypotheses:

People with long duration T1D and maintained endogenous insulin production have an altered balance of islet destructive T cells (islet-specific auto reactive CD4 helper and CD8 killer T cells) and islet protective T cells (regulatory T-cells) and may have different genetic risk factors for autoimmune disease.

Study Aim:

To improve our understanding of insulin production in individuals diagnosed with Type 1 diabetes.

TIGI is an observational case control study. All potential participants will be identified from either routine clinical care or from existing research cohorts managed by the Peninsula Research Bank as part of the NIHR Exeter Clinical Research Facility (ECRF). Potential participants who appear to meet the entry criteria will be given written information on the project, followed by the opportunity to discuss the project in more detail with a member of the research team. The research team will be responsible for the recruitment process.

Participants will be recruited under UK wide ethics.

All participants (or their legal guardians) will be required to provide written informed consent and will be informed of their right to withdraw from the stud at any time with prejudice or jeopardy to any future clinical care.

Participants will be asked to attend the NIHR Exeter Clinical Research Facility for a single appointment, having fasted overnight. To reduce patient burden, participants who are unable to visit the research facility will be offered an appointment locally (e.g. home or GP surgery). They will have been asked to provide a urine sample to be collected 2 hours after their main meal on the day before the study visit (for analysis of UCPCR).

Blood samples will be collected at baseline (fasting) and at 0, 30,60, 90 \& 120 minutes post meal for adult participants attending the research facility. For children under 16 years of age and all participants recruited at home, samples will be collected at 90 minutes post meal only.

Baseline data will include: Height (m), weight (kg), age of diagnosis, current and previous insulin treatment and family history of diabetes.

Blood samples will be collected for Serum C-peptide and other routine biochemistry, DNA extraction (for HLA typing and T1D risk SNP typing), Peripheral blood mononuclear cells (PBMCs) for analysis of auto reactive and regulatory T-cells, and plasma and serum samples for storage for future analysis.

All samples will be appropriately labelled in accordance with the 1998 Data Protection Act. Biological samples collected from participants will be transported, stored, accessed and processed in accordance with national legislation relating to the use and storage of human tissue for research purposes. Participants will have the opportunity to consent to gift samples at the end of the study for future research.

Safety: Blood samples will be collected by staff trained in venepuncture. Any potential discomfort or side -effects will be equivalent to that experienced in routine clinical care. Risk of hyperglycemia (from having a meal without their usual mealtime insulin): Participants will be closely monitored during and after their visit by the diabetes specialist research team. Appropriate advice/support will be given if required.

Potential Benefit: In the short term we hope to gain an improved understanding of the causes of T1D. In the longer term this work may lead to improved therapeutic, vaccine and transplantation treatments for T1D.

Adverse Effects: Should any unforeseen adverse events arise that possibly, probably or definitely related to a study procedure, they wil be reported to the Sponsor and CI within 24 hours of the research team becoming aware of the event.

Confidentiality: All information related to study participants will be kept confidential and managed in accordance with the Data Protection Act, NHS Caldicott Guardian, The Research Governance Framework for Health \& Social Care and Research Ethics Committee Approval.

Participant date will be held in link-anonymised format, with personal identifiable data only accessible to personnel with training in data protection who require this information to perform their study role.

Record Retention \& Archiving: When the research study is complete, it is a requirement of the Research Governance Framework and Sponsor Trust Policy that the records are kept for a further 15 years.

Statistics \& Sample Size:

The main analysis will be to assess if there is a difference in the immune phenotype of patients with the most (High C-peptide) and the least (Low C-peptide) persistent endogenous insulin relative to duration.

We will recruit at least 110 patients in each group in keeping with previous recruitment in Exeter. We predict a minimum of 100 will have confirmed extreme C-peptide in each group. This will give 90% power to detect at p<0.01, a difference of 0.6 standard deviation in measures of immune function and a difference in proportions of 30 (50 v 80)%. Previous studies have shown differences of >1 SD in the mean suppressive function of autoreactive T cells and a difference in proportion of 39%.

The total sample size for this project will be at least 250, to achieve the required number of patients with extreme C-peptide as detailed above.

Both groups will have a range of diabetes duration.

Monitoring of this study will ensure compliance with Good Clinical Practice. The Investigators will permit monitoring, audits, REC review and regulatory inspections by providing the Sponsor(s), Regulators and REC direct access to source data and other documents.

NHS indemnity will apply to participants and UK public liability insurance is provided by the University of Exeter.

Project development and user involvement:

The study team will have access to the user representative group of the NIHR Exeter Clinical Research Facility (ECRF). In keeping with the NHS Patient Carer and Public Involvement (PCPI) strategy the ECRF invites user representatives to contribute to the development of various projects within its portfolio. These individuals have agreed to maintain contact and regular meetings have been established at which researchers discuss the development of current projects within the ECRF.

This work is funded by a patient-focused diabetes charity, JDRF. On completion of the study, the data will be analysed and a final study report will be prepared and submitted to the funder, sponsor and ethics committee. Results will be written up and submitted for publication in peer reviewed journal(s). Abstracts will be submitted to national and international conferences. Written information in the form of a letter/newsletter outlining the key findings of the study will be posted on the study web page.