Vitamin D Supplementation in CAD and Postchallenge Hyperglycemia

Effects of Vitamin D Supplementation in Coronary Artery Disease Patients With Postchallenge Hyperglycemia and Vitamin D Deficiency on Endothelial Function and Insulin Sensitivity

The main aim of the investigation is to clarify, whether vitamin D supplementation in coronary artery disease patients with vitamin D deficiency and postchallenge hyperglycemia has an impact on endothelial dysfunction and parameters of insulin sensitivity and beta-cell function.

An improvement of endothelial dysfunction as a cardiovascular surrogate parameter could be translated in a reduced risk for future cardiovascular events, which is of major interest, since patients with postchallenge hyperglycemia face a significantly higher cardiovascular risk than patients with normal glucose tolerance. Furthermore an improvement in insulin sensitivity and/or beta-cell function would identify vitamin D as an important strategy for the prevention of type 2 diabetes. In consideration of the rapidly increasing prevalence of diabetes and the failure of current prevention strategies this could be an important, safe and cheap way to support ongoing lifestyle modifying programs. Our study of course investigates surrogate cardiovascular and insulin sensitivity parameters. Assuming a beneficial effect of vitamin D in our study, this concept would have to be proven in further large outcome as well as diabetes prevention trials.

Inclusion Criteria:

• Age 40-75
• Postchallenge hyperglycemia (2h-whole blood glucose value in oral glucose tolerance test above 119 mg/dl, normal fasting glucose)
• Angiographically verified coronary artery disease (>50% stenosis)
• Serum 25-OH- vitamin D < 20 ng/ml in winter/spring/autumn and <25 ng/ml during june-september
• Stable antihypertensive therapy in the last 3 month

Exclusion Criteria:

• Acute coronary syndrome or cerebrovascular event within the previous 1 month
• BMI > 40 kg/m²
• Serum creatinine >2.5 times the upper limit of normal
• GOT or GPT > 3 times the upper limit of normal
• Heart failure > NYHA class II
• Uncontrolled hypertension (>160/100 mmHg)
• New onset of statins, ACE-inhibitors or ARBs within the previous 4 weeks
• History of urolithiasis
• Hypercalcaemia
• Major psychiatric disorders
• Ongoing treatment with spironolactone, canrenoate, eplerenone, amiloride, triamterene and aliskiren.
• Treatment with antipsychotic drugs
• Regular significant antioxidants, vitamins or protein supplementation
• Immunosuppressive therapy
• Glucocorticoid therapy
• Ongoing chemotherapy
• Pregnancy
• Any other disease with an estimated life expectancy below 1 year.