1. Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany, and Dipartimento di Scienze Chimiche, Università del Piemonte, Orientale, Alimentari, Farmaceutiche e Farmacologiche, Via Bovio 6, 28100 Novara, Italy