Paired Subcutaneous and Visceral Adipose Tissue Aquaporin-7 Expression in Human Obesity and Type 2 Diabetes: Differences and Similarities between Depots

Context: AQP7 is considered to be the sole adipose glycerol channel, and its regulation is crucial for glycemia control. Objectives: In this work, we aimed to further characterize AQP7 in human adipose tissue in obesity and type 2 diabetes (T2D): 1) to assess AQP7 expression levels in paired abdominal adipose tissue depots (sc and visceral); 2) to relate it with gene expression of genes involved in lipid metabolism; and 3) to confirm that AQP7 is mainly expressed in the adipocytes. Design: We conducted a transversal study of gene expression in paired samples of sc adipose tissue (SAT) and visceral adipose tissue (VAT). Patients: Caucasian lean and obese subjects (n = 62, matched for age and gender) and T2D subjects (n = 11, matched for age, gender, and BMI with their control group) participated in the study. Main Outcome Measure: We measured AQP7 expression levels in paired SAT and VAT. Results: We have proved the presence of AQP7 mRNA and protein in the adipocyte rather than the stromovascular fraction of adipose tissue (P = 0.001) and in mature adipocytes when differentiated in vitro. Increased AQP7 mRNA expression levels in VAT from T2D obese subjects (P < 0.05) were found. AQP7 transcript levels ratio of SAT vs. VAT changed with the presence of obesity and T2D. Interestingly, there were positive associations between AQP7 and both lipogenic and lipolytic genes in a similar manner in both adipose depots. Conclusions: Taken together, these data suggest a subtle regulation between adipose depots of the sole adipose aquaporin, AQP7, which is unbalanced in obesity and T2D. (J Clin Endocrinol Metab 95: 3470-3479, 2010)