Context: Aquaporin-7 is required for efflux of glycerol from adipocytes and influences whole-body glucose homeostasis in animal studies

Objective: To test the hypothesis that AQP7 gene expression levels may be affected by presence of obesity and type 2 diabetes in humans.

Design: Obesity study cohort: 12 lean; 22 non-severely obese and 13 severely obese subjects. Type 2 Diabetes study cohort: 17 lean and 39 obese type 2 diabetic patients. sMCP-1, glycerol, sTNFR1, sTNFR2 and sIL-6 circulating levels measured by ELISA. Subcutaneous adipose tissue gene expression of: AQP7, MCP-1, IL-6, TNF, PPAR and SREBP1c genes by real time PCR. AQP7 gene mutation analysis was performed.

Results: Severely obese women showed lower AQP-7 expression levels compared with lean and non-severely obese (p<0.001). Moreover, circulating glycerol concentration was lower in severely obese subjects, but no correlation with AQP7 adipose tissue expression was observed. AQP7 expression was negatively related with proinflammatory genes (MCP-1: r=-0.203, p=0.044 and TNF: r=-0.209, p=0.036). Concerning adipogenic factors, AQP7 expression levels were found to be positively determined by PPAR mRNA expression levels (r=0.265, p=0.012). AQP7 expression did not show differences regarding the presence of type 2 diabetes.

Conclusion: Expression of AQP7 is down-regulated in women with severe obesity. The expression of this glycerol channel is not affected by type 2 diabetes.