Benefits of Retained Insulin for Good Health

The purpose of this study is to understand the possible benefits of restoring insulin secretion in people living with diabetes, and to understand how insulin secretion can be best measured in people living with diabetes.

Most people living with type 1 diabetes stop making their own insulin, this means that insulin injections are needed to survive. It also means their blood glucose is variable, meaning it is very difficult to control blood glucose levels. This is in contrast to type 2 diabetes, where most people keep making their own insulin, and loss of insulin production is uncommon.

Previous research has shown that some people with type 1 diabetes keep making some of their own insulin, and this can be very helpful for their blood glucose control. However, there is limited information on long term benefits of making insulin, and other possible benefits, such as on wellbeing, have not been studied. It is important that the full benefits of making insulin are known as new treatments have been developed to preserve insulin secretion in type 1 diabetes, and/or to restore insulin secretion. These treatments are expensive and can have side effects, and have been studied only in small studies for a short amount of time. It is important to fully understand the likely long-term benefits of preserving or restoring insulin secretion to know whether healthcare providers like the NHS should fund these treatments.

At present research studies that are testing new treatments to preserve or restore a person's insulin production need to frequently test insulin secretion, using a test called a mixed meal tolerance test that needs to be undertaken in a hospital setting and takes at least 2.5 hours. This makes these studies difficult to take part in, and expensive to run. Insulin production can now be measured at home, on a finger-prick test, but more information is needed on the best way to do the home test for these kinds of studies.

This research has two parts. In the first part of this research the investigators will measure insulin secretion (using a test called C-peptide) in 500 people with insulin treated diabetes who have already taken part in a large recent study that measured their insulin secretion, and other important measures such as their quality of life and use of healthcare services, every year for up to 4 years after diabetes diagnosis. There will be assessment of participants' quality of life and other measures related to diabetes. The investigators will use this information, and the information already collected in the study, to understand the effects of retaining or loosing insulin production over up to 9 years from diabetes diagnosis, and compare whether this differs in type 1 and 2 diabetes.

In the second part of this research the investigators will recruit 200 participants with type 1 diabetes who have had their insulin secretion measured in part one of this research, in other research or in clinical care. Information from this previous testing will be used to ensure participants are recruited with a range of insulin production. Participants will attend a research facility for assessment of their insulin production over 2 hours after a liquid meal similar to a milkshake. Participants will then undertake this test at home, using finger-prick samples after the same liquid meal, and after 3 of their own normal meals. Participants will also monitor their glucose over 2 weeks using a device called a continuous glucose monitor. This information will be used to understand if home measures are as accurate as the test in the research facility, and work as well in predicting a person's risk of low glucose (hypoglycaemia) and how variable their glucose is.

The end result of this research will be important information to inform the design of studies of new treatments to preserve or restore insulin secretion for people living with diabetes and understand the likely long-term benefits of these treatments.

ARM 1

Inclusion criteria

• Previously recruited to the StartRight study (NCT03737799) with consent to be contacted for further research
• Clinical diagnosis of diabetes & Insulin treated
• Able and willing to provide informed consent/assent.
• Aged 18 years or older.

ARM 2

Inclusion criteria

• Clinical diagnosis of Type 1 diabetes
• Known C-peptide, measured as part of previous research or as part of diabetes clinical care OR Where C-peptide is not measured, participant must be within 7 years of diagnosis and have at least 1 positive islet antibody, measured at any time since diabetes diagnosis.
• Where measured C-peptide is >600pmol/L, previous positive islet autoantibodies.
• Able and willing to provide informed consent
• Aged 18 years or older

Exclusion criteria

• Renal failure defined by eGFR <30mL/min/1.73 m²