The significance of adipocyte-specific glycerol channel, aquaporin adipose for life-style related diseases.

在本研究中，我们研究了AQPap缺乏小鼠AQPap与肥胖的关系。WT和KO小鼠的体重没有差异，但KO小鼠在12周龄后开始肥胖。20周龄时AQPap KO小鼠脂肪组织重量显著高于WT小鼠。组织学分析显示KO小鼠WAT肥厚性脂肪细胞增多。KO小鼠表现出与肥胖相关的全身胰岛素抵抗。我们还证明，3T3-L1脂肪细胞中AQPap的敲低会增加细胞内甘油含量，提高甘油激酶活性，增强油酸摄取，最终导致TG积累（PNAS 2005）。此外，我们还研究了AQP对脂肪细胞分化的影响。分别从WT和AQPap KO小鼠的WAT中分离基质血管细胞（SVCs）分化为脂肪细胞，分别在诱导后2、4和6 d检测脂肪细胞油红O染色和PPAR基因表达。来自WT和KO小鼠的SVC脂肪细胞没有差异。在肾上腺素诱导的脂溶状态下，KO小鼠SVC脂肪细胞中甘油的中浓度明显低于WT小鼠。这些发现表明AQPap是一个不影响脂肪细胞分化的甘油通道。我们还可以在3T3-L1脂肪细胞或293细胞中鉴定出叉头型转录因子Foxol作为AQPap的启动子之一，并通过凝胶移位实验确认Foxo 1结合胰岛素反应元件（IRE） 1位点。我们的一系列研究结果发表在2005年的News & Views of Nature杂志上，此外，我们还在2006年的BBA杂志上发表了AQPap和甘油代谢的综述。

In the present study, we investigated the relationship between AQPap and obesity in mice lacking AQPap. There is no difference in body weight of WT and KO mice, but KO mice become obese after 12 weeks of age. Adipose tissue weights of AQPap KO mice are significantly heavier than WT mice at 20 weeks of age. Histlogical analysis shows an increase in hypertrophic adipocytes in WAT of KO mice. KO mice exhibit whole body insulin resistance associated with obesity. We also demonstrated that knock down of AQPap in 3T3-L1 adipocytes increases intracellular glycerol contents, elevates glycerol kinase activities, enhances oleic acid uptake, and finally results in TG accumulation (PNAS 2005).Furthermore, we investigated the effect of AQP ap on the differentiation of adipocytes. The stromal vascular cells (SVCs) which are isolated from WAT of WT or AQPap KO mice are differentiated to adipocytes and the adipocytes after 2,4 and 6 days from induction are examined the staining by oil red O and the genetic expression of PPAR. There are no differences between SVC adipocytes derived from WT and KO mice. The medium concentration of glycerol is significantly lower in SVC adipocytes from KO mice than in those from WT mice during the lipolytic state induced by epinephrine. These findings suggest that AQPap is a glycerol channel without the effects on the differentiation of adipocytes. We could also identify a fork-head type transcriptional factor, Foxol, as one of the promoters for AQPap using 3T3-L1 adipocytes or 293 cells and confirm the Foxo 1 binds insulin response element (IRE) 1 site by gel shift assay.Our series of these results were presented in News ＆ Views of Nature 2005 and moreover, we published the review for AQPap and glycerol metabolism in BBA 2006.