Cross-sectional studies

Recruitment of patients from cross-sectional studies are described elsewhere [cohort 1 (10) and cohort 2 (11)]. In cohort 1, a group of participants with morbid obesity (BMI >35 kg/m²; n = 38) was studied. All these subjects were recruited at the Endocrinology Service of the Hospital of Girona “Dr. Josep Trueta,” were of Caucasian origin, and reported that their body weight had been stable for at least 3 mo before the study. Subjects were studied in the postabsorptive state. BMI was calculated as [weight (kg)]/[height (m)]². The patients had no systemic disease other than obesity, and all were free of any infections in the month before the study. Liver diseases (specifically tumoral disease and hepatitis C virus infection) and thyroid dysfunction were specifically excluded by biochemical work-up. All subjects gave written informed consent, validated and approved by the Ethics Committee of the Hospital of Girona “Dr. Josep Trueta,” after the purpose of the study was explained to them. AT samples were obtained from subcutaneous AT (SAT) and visceral AT (VAT) depots during elective surgical procedures (cholecystectomy, surgery for abdominal hernia, and gastric bypass surgery). Samples of AT were immediately transported to the laboratory (5–10 min). The tissue was handled in strictly aseptic conditions. AT samples were washed in PBS, cut off with forceps and scalpel into small pieces (100 mg), and immediately flash frozen in liquid nitrogen before being stored at −80°C. In cohort 2, SAT from a group of participants (n = 73) with a wide range of obesity (age range, 25–75 yr; BMI, 19.5–85.2 kg/m²) was studied.