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

在本研究中，我们调查了AQPap和缺乏AQPap的小鼠肥胖之间的关系。WT和KO小鼠的体重没有差异，但KO小鼠在12周龄后变得肥胖。AQPap KO小鼠的脂肪组织重量在20周龄时显著高于WT小鼠。组织学分析显示KO小鼠的WAT中肥大脂肪细胞增加。KO小鼠表现出与肥胖相关的全身胰岛素抵抗。我们还证明，在3 T3-L1脂肪细胞中敲低AQPap增加细胞内甘油含量，提高甘油激酶活性，增强油酸摄取，并最终导致TG积累（PNAS 2005）。此外，我们研究了AQPap对脂肪细胞分化的影响。从WT或AQPap KO小鼠的WAT中分离基质血管细胞（stromal vascular cells，SVCs），诱导分化为脂肪细胞，并在诱导后2、4和6天检测脂肪细胞油红O染色和过氧化物酶体增殖物激活受体（PPAR）基因表达。来自WT和KO小鼠的SVC脂肪细胞之间没有差异。在肾上腺素诱导的脂解状态下，KO小鼠SVC脂肪细胞中甘油的中浓度显著低于WT小鼠。这些结果表明AQPap是一种甘油通道，不影响脂肪细胞的分化。我们还利用3 T3-L1脂肪细胞或293细胞鉴定了一个叉头型转录因子Foxol作为AQPap的启动子之一，并通过凝胶迁移试验证实Foxo 1与胰岛素反应元件（IRE）1位点结合。

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.