OBJECTIVEThe angiopoietin-like protein 4 (Angptl4)/fasting-induced adipose factor (Fiaf) is known as a regulator of peripheral lipid and glucose metabolism. In the present study, we investigated the physiological role of Angptl4 in central regulation of body weight homeostasis.RESEARCH DESIGN AND METHODSHypothalamic Angptl4 expression levels were measured using immunoblot assay during feeding manipulation or after administration of leptin, insulin, and nutrients. The effects of Angptl4 on food intake, body weight, and energy expenditure were determined following intracerebroventricular (ICV) administration of Angptl4 in C57BL/6 mice. Food intake, energy metabolism, and feeding responses to leptin, insulin, and nutrients were compared between Angptl4-null mice and their wild littermates. Finally, the relationship of hypothalamic AMP-activated protein kinase (AMPK) and Angptl4 was studied.RESULTSHypothalamic Angptl4 expression levels were increased upon food intake or administration of leptin, insulin, and nutrients. Furthermore, central administration of Angptl4 suppressed food intake and body weight gain but enhanced energy expenditure. These effects were mediated via suppression of hypothalamic AMPK activities. Consistently, Angptl4-null mice displayed increased body weight and hypothalamic AMPK activity but reduced energy expenditure. Food intake following a fast was significantly greater in Angptl4-null mice, which was normalized by centrally administered Angptl4. Moreover, anorectic responses to leptin, insulin, and glucose were diminished in Angptl4-null mice. In contrast, Angptl4-null mice were resistant to diet-induced obesity, indicating obesity-promoting effects of Angptl4 under the condition of fat-enriched diet.CONCLUSIONSWe have demonstrated that hypothalamic Angptl4 is regulated by physiological appetite regulators and mediates their anorexigenic effects via inhibition of hypothalamic AMPK activity. Therefore, Angptl4 appears to have an important role in central regulation of energy metabolism.

Circulating visfatin is independently associated with diabetes and resistin concentration, but is not related to adiponectin multimers or other metabolic covariates. These data are suggestive of a potential role of visfatin in subclinical inflammatory states.

Adiponectin (APN) is a crucial regulator for many inflammatory processes, but its effect on Th cell-mediated responses has not been fully understood. Thus, we investigated the immune-modulatory effects of APN on dendritic cells (DCs) controlling Th cell polarization. APN induced maturation and activation of DCs, as demonstrated by the increased expression of MHC class II, costimulatory molecules in both mouse and human DCs, and it significantly enhanced production of proinflammatory cytokines. APN triggered degradation of IκB proteins, nuclear translocation of NF-κB p65 subunit, and phosphorylation of MAPKs in DCs. Pretreatment with a phospholipase C (PLC)γ inhibitor and a JNK inhibitor suppressed IL-12 production and NF-κB binding activity. Additionally, PLCγ inhibitor downregulated phosphorylation of JNK, indicating that PLCγ and JNK may be upstream molecules of NF-κB. Importantly, APN-treated DCs significantly induced both Th1 and Th17 responses in allogeneic CD4+ T cells. The addition of a neutralizing anti–IL-12 mAb to the cocultures abolished the secretion of IFN-γ, whereas the blockage of IL-23 and IL-1β suppressed APN-induced IL-17 production. Immunization of mice with OVA-pulsed, APN-treated DCs efficiently led to Ag-specific Th1 and Th17 cell responses. Taken together, these results demonstrated that APN effectively induced activation of DCs through PLCγ/JNK/NF-κB-signaling pathways, leading to enhanced Th1 and Th17 responses.

Hypothalamic feeding circuits are essential for the maintenance of energy balance. There have been intensive efforts to discover new biological molecules involved in these pathways. Here we report that central administration of clusterin, also called apolipoprotein J, causes anorexia, weight loss and activation of hypothalamic signal transduction-activated transcript-3 in mice. In contrast, inhibition of hypothalamic clusterin action results in increased food intake and body weight, leading to adiposity. These effects are likely mediated through the mutual actions of the low-density lipoprotein receptor-related protein-2, a potential receptor for clusterin, and the long-form leptin receptor. In response to clusterin, the low-density lipoprotein receptor-related protein-2 binding to long-form leptin receptor is greatly enhanced in cultured neuronal cells. Furthermore, long-form leptin receptor deficiency or hypothalamic low-density lipoprotein receptor-related protein-2 suppression in mice leads to impaired hypothalamic clusterin signalling and actions. Our study identifies the hypothalamic clusterin-low-density lipoprotein receptor-related protein-2 axis as a novel anorexigenic signalling pathway that is tightly coupled with long-form leptin receptor-mediated signalling.

Context and Objective:Glypican-4 was identified as a novel adipokine capable of enhancing insulin signaling and modulating adipocyte differentiation. We investigated associations between glypican-4 and body composition, insulin resistance, arterial stiffness, and nonalcoholic fatty liver disease (NAFLD) in nondiabetic Asian subjects. Design and Participants:We analyzed baseline cross-sectional data from the Korean Sarcopenic Obesity Study, an ongoing prospective cohort study. NAFLD was diagnosed by unenhanced computed tomography using the liver attenuation index. We also examined the effects of a 3-month combined aerobic and resistance exercise program on glypican-4 levels and cardiometabolic risk factors. Results:Circulating glypican-4 levels were higher in men than in women (1.83 [1.19, 2.78] ng/mL vs 1.17 [0.66, 2.00] ng/mL, P Ͻ .001) and had a significant positive relationship with the waist-to-hip ratio (WHR) (r ϭ 0.20, P ϭ .014) and the ratio of visceral to sc fat area (r ϭ 0.30, P Ͻ .001). Furthermore, glypican-4 levels in women were correlated with cardiometabolic risk factors, including insulin resistance and arterial stiffness, and were independently associated with NAFLD by multiple logistic regression analysis (P ϭ .017, R 2 ϭ 0.33). The 3-month combined exercise training program significantly improved several cardiometabolic parameters and reduced retinol binding protein-4 levels. Changes in glypican-4 levels after the exercise program were significantly different between subjects with an increased WHR compared with those with a decreased WHR (P ϭ .034). Conclusion:A gender-based difference in circulating glypican-4 levels was apparent as these were increased in women with NAFLD and related to body fat distribution, insulin resistance, and arterial stiffness. A dipose tissue plays an important role in controlling systemic energy homeostasis through the secretion of various adipokines that interact with the brain, pancreas, skeletal muscle, and liver (1). Because visceral adipose tissue is more pathogenic than sc adipose tissue, the site of fat accumulation plays a pivotal role in metabolic disorders (2). However, little is known about the factors that determine sites of fat accumulation. Recently, Gesta et al found that glypican-4 is differentially expressed in visceral and sc adipose tissue, and that its expression in Abbreviations: AST, aspartate aminotransferase; baPWV, brachial ankle pulse wave velocity; BMI, body mass index; HOMA-IR, homeostasis model assessment of insulin resistance; NAFLD, nonalcoholic fatty liver disease; VFA/SFA, ratio of visceral to sc fat area; WHR, waist-to-hip ratio.