Managing Insulin Pumps for Exercise - Study 1

People with Type 1 Diabetes Mellitus (T1DM) like to take part in sport and exercise, but problems with metabolism and blood glucose control can make this difficult. Some people with T1DM administer their insulin via an insulin pump, also know as continuous subcutaneous insulin infusion (CSII) therapy, in which a background or basal level of insulin is constantly infused under the skin by a special pump, with bolus doses of insulin given to accompany food. Clinical experience suggests that this may be particularly useful for managing diabetes for exercise, but there is limited experimental evidence to support this. The aim of this research , which is divided into three parts, is to investigate the hypothesis that the physiological response to sub-maximal (moderate) exercise of a person with type 1 diabetes treated with CSII, can be made to approximate more closely to the physiological response of a healthy individual by a prior reduction of their basal insulin infusion rate. This first part of the research is designed to compare metabolic response to exercise between people without diabetes and people with T1DM running there insulin pump at the usual basal rate.

For the first part of the study, participants will be either people with type 1 diabetes treated with insulin pump therapy or volunteers without diabetes. The 2 groups will be matched as far as possible by age, body mass index and usual level of activity. Participants will attend an exercise laboratory on 2 occasions. On the first occasion, which can take place at any time of day, formal written consent will be obtained for participation in the study. Participants will then undergo measurement of maximal exercise capacity (VO2 MAX). On the second occasion they will attend 2 hours after a lunch containing 60 grams of carbohydrate (advice will be given on how this can be achieved). A cannula will be inserted on arrival and blood samples obtained. Arterialised samples will be obtained by using a heated hand technique. Once the cannula has been inserted participants with type 1 diabetes will be asked to reduce the basal insulin infusion rate on their insulin pump to 70% of normal until the end of the study visit. After 30 minutes a further set of blood samples will be obtained, and participants will then start to exercise for 1 hour at 50% VO2 MAX. A further set of blood samples will be obtained at the end of the hour of exercise. Participants will then rest for 30 minutes before a final set of blood samples is taken. At this point the cannula will be removed and the study visit ends. Participants with diabetes will be given the choice to return basal insulin infusion rate to normal at this point. A snack will be offered.

Blood glucose will be monitored every 10 minutes and also if a participant feels symptoms of hypoglycaemia. If hypoglycaemia occurs the protocol will be stopped and carbohydrate given until the blood glucose level returns to the normal range.

Eligibility Criteria:
Inclusion Criteria:

For participants with Type 1 Diabetes Mellitus

* Participant is willing and able to give informed consent for participation in the study.
* Male or Female, aged between 18 and 65 years
* Diagnosed with Type 1 diabetes mellitus
* Treated with CSII for at least 3 months
* Exercises regularly for more than 1 hour per week

For participants without Type 1 Diabetes Mellitus

* Participant is willing and able to give informed consent for participation in the study
* Male or female, aged between 18 and 65 years
* Exercises regularly for more than 1 hour per week

Exclusion Criteria:

For participants with type 1 Diabetes Mellitus

* People with any one of the following complications of diabetes:

  1. stage 2+ diabetic retinopathy
  2. renal impairment (with creatinine \>150micromol/l)
  3. known history or symptoms of cardiovascular disease
  4. foot ulceration
  5. peripheral vascular disease
* Known pregnancy or breastfeeding
* Untreated or unstable respiratory disease
* Known hypoglycaemia unawareness
* Treatment with drugs known to interfere with glucose metabolism

For participants without Type 1 Diabetes Mellitus

* Known pregnancy or breastfeeding
* Untreated or unstable respiratory disease
* Diagnosis of impaired fasting glucose, impaired glucose tolerance or diabetes mellitus
* Treatment with drugs known to interfere with glucose metabolism