Pediatric Research Institute Hospital Sant Joan de Déu, Barcelona, Spain. CIBER Diabetes y Enfermedades Metabólicas Asociadas, Madrid, Spain. Biochemistry and Molecular Biomedicine, Institute of Biomedicine, University of Barcelona, Barcelona, Spain. CIBER Fisiopatologia de la Obesidad y Nutrición, Madrid, Spain. Pediatric Endocrinology, Dr. Josep Trueta Hospital, Girona, Spain. Girona Institute for Biomedical Research, Girona, Spain. Department of Development & Regeneration, University of Leuven, Leuven, Belgium. Biochemistry and Molecular Biomedicine, Institute of Biomedicine, University of Barcelona, Barcelona, Spain fvillarroya@ub.edu.