Leptin is an adipocyte-derived hormone that plays a key role in energy homeostasis, yet resistance to leptin is a feature of most cases of obesity in humans and rodents. In vitro analysis suggested that the suppressor of cytokine signaling-3 (Socs3) is a negative-feedback regulator of leptin signaling involved in leptin resistance. To determine the functional significance of Socs3 in vivo, we generated neural cell-specific SOCS3 conditional knockout mice using the Cre-loxP system. Compared to their wild-type littermates, Socs3-deficient mice showed enhanced leptin-induced hypothalamic Stat3 tyrosine phosphorylation as well as pro-opiomelanocortin (POMC) induction, and this resulted in a greater body weight loss and suppression of food intake. Moreover, the Socs3-deficient mice were resistant to high fat diet-induced weight gain and hyperleptinemia, and insulin-sensitivity was retained. These data indicate that Socs3 is a key regulator of diet-induced leptin as well as insulin resistance. Our study demonstrates the negative regulatory role of Socs3 in leptin signaling in vivo, and thus suppression of Socs3 in the brain is a potential therapy for leptin-resistance in obesity.

Endothelial secretion of von Willebrand factor (VWF) from intracellular organelles known as Weibel-Palade bodies (WPBs) is required for platelet adhesion to the injured vessel wall. Here, we demonstrate that WPBs are in some cases found near or within autophagosomes and that endothelial autophagosomes contain abundant VWF protein. Pharmacological inhibitors of autophagy, or knockdown of the essential autophagy genes Atg5 or Atg7, inhibits the in vitro secretion of VWF. Furthermore, while mice with an endothelial specific deletion of Atg7 have normal vessel architecture and capillary density, these animals exhibit impaired epinephrine-stimulated VWF release, reduced levels of high molecular weight VWF multimers and a corresponding elevation of their bleeding times. Endothelial deletion of Atg5 or pharmacological inhibition of autophagic flux results in a similar in vivo alteration of hemostasis. Thus, autophagy regulates endothelial VWF secretion and transient pharmacological inhibition of autophagic flux may be a useful strategy to prevent thrombotic events.

Suppressor of cytokine signaling 1 (SOCS1) is an important negative regulator for cytokines; however, the role of SOCS1 in Th17 differentiation has not been clarified. We generated T cell-specific SOCS1-deficient mice and found that these mice were extremely resistant to a Th17-dependent autoimmune disease model, experimental autoimmune encephalomyelitis. SOCS1-deficient naive CD4+ T cells were predominantly differentiated into Th1 and poorly into Th17 in vitro. These phenotypes were canceled in IFN-γ−/− background, suggesting that a large amount of IFN-γ in SOCS1-deficient T cells suppressed Th17 differentiation. IL-6 plus TGF-β enhanced retinoic acid receptor-related orphan receptor (ROR)-γt expression and suppressed IFN-γ production in wild-type T cells, whereas these effects were severely impaired in SOCS1-deficient T cells. These phenotypes can be partly explained by STAT3 suppression by enhanced SOCS3 induction through hyper-STAT1 activation in SOCS1-deficient T cells. In addition, SOCS1-deficient T cells were much less sensitive to TGF-β. Suppression of Th1 differentiation by TGF-β was impaired in SOCS1-deficient T cells. TGF-β-mediated Smad transcriptional activity was severely inhibited in SOCS1-deficient cells in the presence of IFN-γ. Such impairment of TGF-β functions were not observed in SOCS3-overexpressed cells, indicating that suppression of Smads was independent of SOCS3. Therefore, SOCS1 is necessary for Th17 differentiation by suppressing antagonistic effect of IFN-γ on both STAT3 and Smads. Induction of SOCS3 can partly explain IFN-γ-mediated STAT3 suppression, while other mechanism(s) will be involved in IFN-γ-mediated Smad suppression. SOCS1-deficient T cells will be very useful to investigate the molecular mechanism for the STAT1-mediated suppression of Th17 development.

SummaryThe physiological role of autophagic flux within the vascular endothelial layer remains poorly understood. Here, we show that in primary endothelial cells, oxidized and native LDL stimulates autophagosome formation. Moreover, by both confocal and electron microscopy, excess native or modified LDL appears to be engulfed within autophagic structures. Transient knockdown of the essential autophagy gene ATG7 resulted in higher levels of intracellular 125 I-LDL and oxidized LDL (OxLDL) accumulation, suggesting that in endothelial cells, autophagy may represent an important mechanism to regulate excess, exogenous lipids. The physiological importance of these observations was assessed using mice containing a conditional deletion of ATG7 within the endothelium. Following acute intravenous infusion of fluorescently labeled OxLDL, mice lacking endothelial expression of ATG7 demonstrated prolonged retention of OxLDL within the retinal pigment epithelium (RPE) and choroidal endothelium of the eye. In a chronic model of lipid excess, we analyzed atherosclerotic burden in ApoE À/À mice with or without endothelial autophagic flux. The absence of endothelial autophagy markedly increased atherosclerotic burden. Thus, in both an acute and chronic in vivo model, endothelial autophagy appears critically important in limiting lipid accumulation within the vessel wall. As such, strategies that stimulate autophagy, or prevent the agedependent decline in autophagic flux, might be particularly beneficial in treating atherosclerotic vascular disease.Key words: autophagy; lipids; atherosclerosis; mouse.Cardiovascular disease, driven in part by the accumulation of modified lipids within the vessel wall, represents the leading cause of death in developed nations (Go et al., 2013). Considerable attention and study has been directed at the molecular consequences following the subendothelial deposition of lipids. These consequences include the recruitment of inflammatory cells and the subsequent engulfment of this deposited subendothelial lipid by resident macrophages (Chinetti-Gbaguidi et al., 2014;Randolph, 2014). In contrast, relatively little is known regarding the steps proximal to lipid deposition and what regulatory role, if any, the endothelium might play in this process. While evidence is limited for the case of the endothelium, in other cell types it appears that autophagy may play a critical role in maintaining overall lipid homeostasis. For instance, mice bearing ATG5-deficient macrophages appear to exhibit increased plaque formation when bred with pro-atherogenic mouse strains (Liao et al., 2012;Razani et al., 2012). While the basis for this increased plaque burden is undoubtedly complex, evidence suggests that macrophage-specific ATG5 deletion results in impaired lipophagy (Sergin & Razani, 2014). Lipophagy refers to the specific degradation of lipids by the autophagic machinery. This concept was perhaps first described in the liver where genetic disruption of macroautophagy led to the accumulation of lipid droplets (Singh...

Mucosal microbial dysbiosis occurs at both inflamed and non-inflamed sites in UC patients. The taxa showing altered abundance in UC patients might mediate colonic inflammation.