Adiponectin Expression and Adipose Tissue Lipolytic Activity in Lean and Obese Women ; Background: The authors evaluated whether adipose adiponectin expression is related to adipose tissue lipolytic activity and fatty acid oxidation rate in lean and obese women. Methods: The study consisted of 60 adult females distributed in a wide range of adiposity (BMI 24.0-53.4 kg/m2). Body composition was estimated by bioelectrical impedance. Respiratory quotient was measured by open-circuit indirect calorimetry. RT-PCR assays were performed to measure TNFa and adiponectin expression in subcutaneous adipose tissue biopsies. Lipolysis studies were performed in fresh tissue samples obtained from subcutaneous abdominal depots during bariatric surgery in 19 morbidly obese females or by an incisional biopsy or during abdominal elective surgery in normal weight and obese females. Glycerol release was measured with a colorimetric endpoint method. Results: Patients with a higher degree of adiposity showed lower adipose tissue adiponectin expression and hormone-sensitive lipase (HSL) activity than women in the low range of adiposity. HSL activity was positively related to adiponectin expression. No relationship was observed between adiponectin and TNFa subcutaneous adipose tissue expression. The positive relationship between respiratory quotient and adiponectin expression was in the limit of statistical significance (P=0.05). Percentage of body fat and mRNA adiponectin explained 26% of the variance of the adipose tissue HSL activity. Conclusions: Low adipose tissue adiponectin expression observed in obese people may contribute to the progression of obesity and its co-morbidities by modulating hormone-sensitive lipase activity and fatty acid oxidation.