Aquaporin 7 (AQP7) is an aquaglyceroprotein responsible for the secretion and uptake of glycerol from the adipocyte. The modulation of the expression of this membrane transport protein might play an important role in the susceptibility to the development of obesity, The aim of the present study was to compare the AQP7 gene expression in subcutaneous abdominal fat in lean vs. obese high fat intakers with a similar daily physical activity pattern. Twelve young men, 6 lean (BMI = 23.2 +/- 0.4 kg/m(2)) and 6 obese (35.0 +/- 1.1 kg/m(2)) with a similar habitual dietary intake of fat (45.5 +/- 2.5 vs. 43.5 +/- 1.7% daily energy from fat for lean and obese, respectively) and physical activity (16.0 +/- 5.7 vs. 17.2 +/- 5.1 METs h/week for lean and obese, respectively), were recruited. Subcutaneous abdominal fat biopsies were obtained and total RNA was extracted and purified. Pools of RNA from lean and obese individuals were probed into Affymetrix GeneChip Human U133A. The microarray analysis revealed that AQP7 gene was down-regulated in obese compared to lean subjects. The results of the microarray analysis were confirmed by real-time PCR studies. In summary, our data show that the AQP7 gene is differentially expressed in adipose tissue of lean and obese individuals. The down-regulation of the AQP7 gene could be implicated in the susceptibility to obesity by reducing glycerol release and promoting the accumulation of lipids in the adipose tissue. (c) 2005 Elsevier Inc. All rights reserved.