The study seeks to explore the cardiovascular effects of co-agonism at the glucagon and (glucagon-like peptide-1) GLP-1 receptor. Glucagon and exenatide will be intravenously infused into participants with type 2 diabetes (T2DM). Overall, the aim of the study is to further the investigator's understanding on the role these endogenous substances have on normal cardiac physiology, myocardial energetics and myocardial glucose uptake through a series of PET and MRI imaging studies

This is a single-centre, single-blinded pilot study designed to understand the role the GLP-1 receptor agonist, exenatide, and glucagon receptor co-agonism has on normal cardiac physiology, myocardial energetics and myocardial glucose utilisation.

Part A - Overweight participants with type 2 diabetes will act as their own control and will undergo a series of three imaging studies (in a randomised order) as detailed below:

1. Cardiac positron emission tomography-magnetic resonance imaging (PET-MRI) with fluorine-18-fluorodeoxyglucose (18F-FDG) with placebo (0.9% saline) infusion
2. Cardiac PET-MRI with 18F-FDG with co-infusion of exenatide and glucagon
3. Cardiac PET-MRI with 18F-FDG with infusion of glucagon

Part B - Overweight participants with type 2 diabetes will act as their own control and will undergo a series of two imaging studies (in a randomised order), followed by one optional visit as detailed below:

1. 7T Phosphorus (P) 31 magnetic resonance spectroscopy (MRS) (31P-MRS) with placebo (0.9% saline) infusion
2. 7T 31P-MRS with co-infusion of glucagon and exenatide 3 (optional) 7T 31P-MRS with infusion of glucagon

Study outcome measures are detailed below

Inclusion Criteria:

• Written informed consent to participate
• Aged >18 years
• Clinical diagnosis of T2DM, either diet controlled or treated with metformin (to be withheld on the morning of the imaging visit)
• BMI ≥25kg/m2
• Current non-smoker

Exclusion Criteria:

• Females of childbearing potential (Part A only) / current pregnancy (all parts)
• Sustained Hypertension (sustained BP >160/100mmHg) or hypotension (systolic BP below 90 mmHg)
• Clinically significant heart disease
• Implanted heart pacemaker or implantable cardioverter defibrillator (ICD)
• Known active malignancy other than skin cancer
• Known renal failure (creatinine >150µmol/L)
• Known type one diabetes mellitus / known or clinically suspected diagnosis of a monogenic form of diabetes
• Poorly controlled blood glucose
• Current daily use of anti-diabetic medication including Insulin, GLP-1 based agonists, DPP4i or any other medication known to interact with either of the study drugs (exenatide or glucagon)
• Current involvement in the active treatment phase of other research studies, (excluding observational/non-interventional).
• Contraindication for MRI/PET scan, i.e. any reason which precludes MRI imaging according to local policy (ie internal pacemaker/defibrillator, metal fragments, claustrophobia)
• Participation in research studies in the last 3 years involving radiation (if the effective dose exceeded 10mSv). This does not include any diagnostic or therapeutic exposures which were clinically justified.
• Any other clinical reason which may preclude entry in the opinion of the investigator

Imaging analysis performed by Antaros Medical (blinded to infusion)