1. Cardiorenal Research Laboratory, Division of Cardiovascular Diseases and Nephrology, Department of Internal Medicine, Mayo Clinic and Foundation, Rochester, Minnesota 55905;
2. Department of Geriatric Medicine and Metabolic Diseases, Second University of Naples, Naples 803131; and
3. Istituto di Clinica Medica L. Condorelli, University of Catania, Catania 95124, Italy