In acute myocardial infarction early restoration of coronary blood flow is the most effective strategy to limit infarct-size. Paradoxically, reperfusion itself also aggravates myocardial injury and contributes to final infarct size, a process termed 'reperfusion injury'. Ischemia and reperfusion (IR)-induced endothelial dysfunction seems to play a pivotal role in this process, resulting in vasoconstriction and reduced blood flow to the already ischemic tissue. Recently, it has been shown that the glucose-lowering drug metformin is able to limit IR-injury in murine models of myocardial infarction, probably by increased formation of the endogenous nucleoside adenosine. In the current research proposal, the investigators aim to translate this finding to the human in vivo situation, using flow-mediated dilation (FMD) of the brachial artery as a well-validated model of (endothelial) IR-injury.

Inclusion Criteria:

• Age 30-50 years
• Written informed consent

Exclusion Criteria:

• Smoking
• Hypertension (in supine position: systolic BP > 140 mmHg, diastolic BP > 90 mmHg)
• Hyperlipidaemia (fasting total cholesterol > 5.5 mmol/L or random > 6.5 mmol/L)
• Diabetes Mellitus (fasting glucose > 7.0 mmol/L or random glucose > 11.0 mmol/L)
• History of any cardiovascular disease
• Concomitant use of medication
• Renal dysfunction (MDRD < 60 ml/min)
• Professional athletes