Macrophages infiltrate adipose tissue in obesity and are involved in the induction of inflammation, thereby contributing to the development of obesity-associated metabolic disorders. Here, we show that the macrophage-derived soluble protein AIM is endocytosed into adipocytes via CD36. Within adipocytes, AIM associates with cytosolic fatty acid synthase (FAS), thereby decreasing FAS activity. This decreases lipid droplet size, stimulating the efflux of free fatty acids and glycerol from adipocytes. As an additional consequence of FAS inhibition, AIM prevents preadipocyte maturation. In vivo, the increase in adipocyte size and fat weight induced by high-fat diet (HFD) was accelerated in AIM-deficient (AIM(-)(/-)) mice compared to AIM(+/+) mice. Moreover, injection of recombinant AIM in AIM(-)(/-) mice suppresses the increase in fat mass induced by HFD. Interestingly, metabolic rates are comparable in AIM(-)(/-) and AIM(+/+) mice, suggesting that AIM specifically influences adipocyte status. Thus, this AIM function in adipocytes may be physiologically relevant to obesity progression.

During intrauterine life, the mammalian embryo survives via its physical connection to the mother. The uterine decidua, which differentiates from stromal cells after implantation in a process known as decidualization, plays essential roles in supporting embryonic growth before establishment of the placenta. Here we show that female mice lacking death effector domain-containing protein (DEDD) are infertile owing to unsuccessful decidualization. In uteri of Dedd -/-mice, development of the decidual zone and the surrounding edema after embryonic implantation was defective. This was subsequently accompanied by disintegration of implantation site structure, leading to embryonic death before placentation. Polyploidization, a hallmark of mature decidual cells, was attenuated in DEDD-deficient cells during decidualization. Such inefficient decidualization appeared to be caused by decreased Akt levels, since polyploidization was restored in DEDD-deficient decidual cells by overexpression of Akt. In addition, we showed that DEDD associates with and stabilizes cyclin D3, an important element in polyploidization, and that overexpression of cyclin D3 in DEDD-deficient cells improved polyploidization. These results indicate that DEDD is indispensable for the establishment of an adequate uterine environment to support early pregnancy in mice. IntroductionApproximately 10%-15% of couples experience infertility during their reproductive years, owing mainly to implantation failure. Among the reasons underlying such failure, defective development of functional decidua at the implantation site within the uterus has recently been highlighted (1-3). In response to implantation, stromal cells immediately surrounding the mucosal crypt where the embryo is embedded proliferate extensively and undergo differentiation into polyploid decidual cells, forming an avascular primary decidual zone, followed by a broad, well-vascularized secondary decidual zone. It is believed that this decidual structure is important for the provision of nutrition to the developing embryo and also acts as a barrier against uncontrolled trophoblast proliferation until the placenta develops. Analyses of mutant mice that show female infertility, such as in knockout mice for homeobox A10 (Hoxa10) (4, 5) or IL-11 receptor (6), have contributed to the investigation of the molecular mechanisms involved in decidualization. Recent evidence has implicated cell-cycle regulation as being essential for both the proliferation and differentiation of stromal cells. In particular, Das and colleagues reported that cyclin D3-dependent activation of cyclin-dependent kinase 4 (Cdk4) or Cdk6 appears to be involved sequentially in those two events during decidua formation (7). In addition to these essential elements, in this report, we present data indicating that the death effector domaincontaining (DED-containing) protein DEDD is indispensable for the maturation of decidual cells and support of female fertility in mice.We previously found that the DEDD protein, initially described as...