Effect of Intact GLP-1 (7-36) and GLP-1 Metabolite (9-36) on Coronary and Peripheral Vascular Function in Adults

Several studies have shown beneficial effects of glucagon-like-peptide-1 (GLP-1) on the cardiovascular system. Native GLP-1 is secreted from L-cells in the intestine as GLP-1(7-36) 1 but is rapidly metabolised by the ubiquitous enzyme dipeptidyl-peptidase-4 (DPP4) to the metabolite GLP-1(9-36). However, the physiological effect of GLP-1 on the cardiovascular system is complex and there seems to be a dual function with intact GLP-1 (7-36), acting through the GLP-1 receptor, and the GLP-1 (9-36) metabolite acting independently of the GLP-1 receptor.

The aim of the study is to investigate the acute effects of intact GLP-1 and GLP-1 metabolite on coronary microcirculation and endothelial function in adults.

Method 20 adults with obesity are recruited to a double-blind randomized cross-over study.

The first 10 included adults will receive 2½ hours infusion of intact GLP-1 (7-36) together with a DPP-IV inhibitor and 2½ hours infusion of saline, on two separate occasions. The infusions will be given in randomized order with a minimum of 24 hours washout period.

The next 10 included adults will receive 2½ hours infusion of GLP-1 (9-36) metabolite and 2½ hours infusion of saline. These will also be given in randomized order with a minimum of 24 hours washout period. Endothelial function and CFR will be measured before and after one, respectively two, hours of infusion.

The effect of GLP-1 infusions on microvascular function is evaluated by coronary flow reserve (CFR), the ratio between echocardiographic measured coronary flow velocity in LAD during adenosine induced myocardial hyperaemia and rest. The effect on endothelial function is assessed by flow mediated dilation (FMD).

Inclusion criteria

• Age 35-70 years
• BMI > 25 kg/m2.
• Central obesity (measured by waist circumference, defined as ≥ 94cm for men and ≥ 80 cm for women)
• Non smokers (6 months abstinent is required)
• Normal creatinine
• For fertile women; negative pregnancy test and use of safe anticonception.
• Speak and understand Danish or English
• Mental ability to follow and understand the study

Exclusion criteria

• Known Diabetes
• Known hypertension (untreated hypertension ≤ 160/100 at inclusion is accepted)
• Haemoglobin < 6.5 mmol/l
• Allergy towards Januvia or Exenatide, Adenosin or Glycerylnitrate
• Documented significant stenosis of the left anterior descending artery (LAD) at coronary angiography or CT-angiography or regional dysfunction documented during dipyridamol stress-echocardiography. If stress test at baseline shows significant stenosis the patient will be excluded from the study.
• Pregnancy
• Severe asthma
• Active cancer, severe co-morbidity with limited life-expectancy, severe hepatic co-morbidity, chronic alcohol abuse, atrial fibrillation, chronic or previous acute pancreatitis, inflammatory bowel disease.