1. General Surgery Unit, Department of General and Digestive Surgery, Hospital General Universitario Gregorio Marañón , 28007, Madrid , Spain
2. Endocrine and Metabolic Surgery Unit, Department of General and Digestive Surgery, Hospital General Universitario Gregorio Marañón , 28007, Madrid , Spain
3. Department of Surgery, School of Medicine, Universidad Complutense de Madrid , 28007, Madrid , Spain
4. Health Research Institute Gregorio Marañón, Immunophysiology Department, Hospital General Universitario Gregorio Marañón , 28007, Madrid , Spain