The High Density Lipoprotein and Endothelial Function, Niacin and Nitric Oxide Study (The High-Ennd Study)

Inclusion Criteria: * Statin treatment for at least 3 weeks * Reduced HDL: \< 40 mg/dL (1.03 mmol/L) in men or \< 50 mg/dL (1.29 mmol/L) in women * Plus TWO of the following (thereby defining the patients to have metabolic syndrome (Grundy et al.; Circulation 2005)): * Elevated waist circumference: ≥ 102 cm (≥ 40 inches) in men or ≥ 88 cm (≥ 35 inches) in women * Elevated triglycerides: ≥ 150 mg/dL (1.7 mmol/L * Elevated blood pressure: ≥ 130 mmHg systolic blood pressure or ≥ 80 mmHg diastolic blood pressure or anti-hypertensive treatment * Elevated fasting glucose: ≥ 100 mg/dL or on drug treatment for elevated fasting glucose Exclusion Criteria: * Hypersensitivity to niacin * Active liver disease or impaired liver function * Persistent elevation of transaminases * Cholestasis * Gastric ulcer * Acute coronary syndrome * Gout * Pregnancy, lactation * Active infections * Cancer * Untreated concomitant diseases * Renal insufficiency or renal failure * Hypothyreosis * Alcoholism * Myopathies * Muscle pain under therapy with fibrates or statins * Hereditary muscle diseases in family history