Yasuhiro Ito

Angiopoietin-like Protein 2 Promotes Chronic Adipose Tissue Inflammation and Obesity-Related Systemic Insulin Resistance

Recent studies of obesity have provided new insights into the mechanisms underlying insulin resistance and metabolic dysregulation. Numerous efforts have been made to identify key regulators of obesity-linked adipose tissue inflammation and insulin resistance. We found that angiopoietin-like protein 2 (Angptl2) was secreted by adipose tissue and that its circulating level was closely related to adiposity, systemic insulin resistance, and inflammation in both mice and humans. Angptl2 activated an inflammatory cascade in endothelial cells via integrin signaling and induced chemotaxis of monocytes/macrophages. Constitutive Angptl2 activation in vivo induced inflammation of the vasculature characterized by abundant attachment of leukocytes to the vessel walls and increased permeability. Angptl2 deletion ameliorated adipose tissue inflammation and systemic insulin resistance in diet-induced obese mice. Conversely, Angptl2 overexpression in adipose tissue caused local inflammation and systemic insulin resistance in nonobese mice. Thus, Angptl2 is a key adipocyte-derived inflammatory mediator that links obesity to systemic insulin resistance.

Angiopoietin-related growth factor antagonizes obesity and insulin resistance

Angiopoietin-related growth factor (AGF), a member of the angiopoietin-like protein (Angptl) family, is secreted predominantly from the liver into the systemic circulation. Here, we show that most (>80%) of the AGF-deficient mice die at about embryonic day 13, whereas the surviving AGF-deficient mice develop marked obesity, lipid accumulation in skeletal muscle and liver, and insulin resistance accompanied by reduced energy expenditure relative to controls. In parallel, mice with targeted activation of AGF show leanness and increased insulin sensitivity resulting from increased energy expenditure. They are also protected from high-fat diet–induced obesity, insulin resistance and nonadipose tissue steatosis. Hepatic overexpression of AGF by adenoviral transduction, which leads to an approximately 2.5-fold increase in serum AGF concentrations, results in a significant (P < 0.01) body weight loss and increases insulin sensitivity in mice fed a high-fat diet. This study establishes AGF as a new hepatocyte-derived circulating factor that counteracts obesity and related insulin resistance.

Activated Protein C Induces Endothelial Cell Proliferation by Mitogen-Activated Protein Kinase Activation In Vitro and Angiogenesis In Vivo

Activated protein C (APC), a natural anticoagulant, has recently been demonstrated to activate the mitogen-activated protein kinase (MAPK) pathway in endothelial cells in vitro. Because the MAPK pathway is implicated in endothelial cell proliferation, it is possible that APC induces endothelial cell proliferation, thereby causing angiogenesis. We examined this possibility in the present study. APC activated the MAPK pathway, increased DNA synthesis, and induced proliferation in cultured human umbilical vein endothelial cells dependent on its serine protease activity. Antibody against the endothelial protein C receptor (EPCR) inhibited these events. Early activation of the MAPK pathway was inhibited by an antibody against protease-activated receptor-1, whereas neither late and complete activation of the MAPK pathway nor endothelial cell proliferation were inhibited by this antibody. APC activated endothelial nitric oxide synthase (eNOS) via phosphatidylinositol 3-kinase–dependent phosphorylation, followed by activation of protein kinase G, suggesting that APC bound to EPCR might activate the endothelial MAPK pathway by a mechanism similar to that of VEGF. APC induced morphogenetic changes resembling tube-like structures of endothelial cells, whereas DIP-APC did not. When applied topically to the mouse cornea, APC clearly induced angiogenesis in wild-type mice, but not in eNOS knockout mice. These in vitro events induced by APC might at least partly explain the angiogenic activity in vivo. This angiogenic activity of APC might contribute to maintain proper microcirculation in addition to its antithrombotic activity.

Angiopoietin-related growth factor (AGF) promotes epidermal proliferation, remodeling, and regeneration.

We report here the identification of an angiopoietin-related growth factor (AGF). To examine the biological function of AGF in vivo, we created transgenic mice expressing AGF in epidermal keratinocytes (K14-AGF). K14-AGF mice exhibited swollen and reddish ears, nose and eyelids. Histological analyses of K14-AGF mice revealed significantly thickened epidermis and a marked increase in proliferating epidermal cells as well as vascular cells in the skin compared with nontransgenic controls. In addition, we found rapid wound closure in the healing process and an unusual closure of holes punched in the ears of K14-AGF mice. Furthermore, we observed that AGF is expressed in platelets and mast cells, and detected at wounded skin, whereas there was no expression of AGF detected in normal skin tissues, suggesting that AGF derived from these infiltrated cells affects epidermal proliferation and thereby plays a role in the wound healing process. These findings demonstrate that biological functions of AGF in epidermal keratinocytes could lead to novel therapeutic strategies for wound care and epidermal regenerative medicine.

Distinct Roles of Ephrin-B2 Forward and EphB4 Reverse Signaling in Endothelial Cells

Objective—The transmembrane ligand ephrin-B2 and its receptor tyrosine kinase EphB4 are specifically expressed on arterial and venous endothelial cells, respectively, and bidirectional signals mediated by both proteins play an important role in vascular development. However, how such bidirectional signals are required for cell-cell adhesion or repulsion remains unclear. Methods and Results—Using a cell line and sorted primary endothelial cells, we show that ephrin-B2 forward signaling through the EphB4 receptor inhibits cell adhesion, whereas EphB4 reverse signaling by the transmembrane ephrin-B2 ligand does not. Cell migration is also inhibited on immobilized ephrin-B2-Fc but not on EphB4-Fc protein. Conclusions—Ephrin-B2 forward signaling and EphB4 reverse signaling differentially affect cell adhesion and migration between arterial and venous endothelial cells.

Ephrin-B2 Induces Migration of Endothelial Cells Through the Phosphatidylinositol-3 Kinase Pathway and Promotes Angiogenesis in Adult Vasculature

Objective—Ephrin-B2 plays a key role in vascular development. The purpose of this study was to elucidate the molecular mechanisms of ephrin-B2 signaling through the EphB receptor in endothelial cells and to determine whether ephrin-B2 contributes to in vivo angiogenesis in adult mice. Methods and Results—A chemotaxis assay on a polycarbonate membrane revealed that ephrin-B2/Fc chimeric protein induced migration of human umbilical vein endothelial cells (HUVECs) at a level 98% greater than control (P <0.01). To determine the signaling pathways activated in the HUVECs by Eph stimulation, phosphatidylinositol-3 kinase (PI3 kinase) activity was determined in an immune complex PI3 kinase assay. Serum-starved HUVECs were stimulated with ephrin-B2/Fc and compared with unstimulated cells. PI3 kinase activity in stimulated cells was higher than that seen in unstimulated cells. In a chemotaxis assay, the PI3 kinase-specific inhibitor LY294002 blocked the migratory response of HUVECs induced by addition of ephrin-B2/Fc. Finally, ephrin-B2/Fc promoted angiogenesis in vivo in corneal neovascularization and Matrigel plug assays in adult mice, whereas LY294002 reduced angiogenesis in Matrigel that was induced by ephrin-B2/Fc. Conclusions—Ephrin-B2/Fc induces the migration of HUVECs through the PI3 kinase signaling pathway. Ephrin-B2/Fc promotes in vivo angiogenesis in adult mice, suggesting that it contributes to adult angiogenesis.

Angiopoietin-Related Growth Factor Enhances Blood Flow Via Activation of the ERK1/2-eNOS-NO Pathway in a Mouse Hind-Limb Ischemia Model

Objective—Transgenic mice overexpressing angiopoietin-related growth factor (AGF) exhibit enhanced angiogenesis, suggesting that AGF may be a useful drug target in ischemic disease. Our goal was to determine whether AGF enhances blood flow in a mouse hind-limb ischemia model and to define molecular mechanisms underlying AGF signaling in endothelial cells. Methods and Results—Intramuscular injection of adenovirus harboring AGF into the ischemic limb increased AGF production, which increased blood flow through induction of angiogenesis and arteriogenesis, thereby reducing the necessity for limb amputation. In vitro analysis showed that exposing human umbilical venous endothelial cells to AGF increased nitric oxide (NO) production through activation of an ERK1/2-endothelial NO synthetase (eNOS) signaling pathway. AGF-stimulated eNOS phosphorylation, NO production, and endothelial cell migration were all abolished by specific MEK1/2 inhibitors. Moreover, AGF did not restore blood flow to ischemic hind-limbs of either mice receiving NOS inhibitor L-NAME or eNOS knockout mice. Conclusion—Activation of an ERK1/2-eNOS-NO pathway is a crucial signaling mechanism by which AGF increases blood flow through induction of angiogenesis and arteriogenesis. Further investigation of the regulation underlying AGF signaling pathway may contribute to develop a new clinical strategy for ischemic vascular diseases.

The impact of surgical outcome after pancreaticoduodenectomy in elderly patients

BackgroundThe elderly population has increased in many countries. Indications for cancer treatment in elderly patients have expanded, because surgical techniques and medical management have improved remarkably. Pancreaticoduodenectomy (PD) requires high-quality techniques and perioperative management methods. If it is possible for elderly patients to withstand an aggressive surgery, age should not be considered a contraindication for PD. Appropriate preoperative evaluation of elderly patients will lead to their safer management. The purpose of the present study was to evaluate the safety of PD in patients older than 75 years and to show the influence of advanced age on the morbidity and mortality associated with this operation.Patients and methodsSubjects were 98 patients who underwent PD during the time period from April 2005 to April 2011. During this study, 31 patients were 75 years of age or older (group A), and the other 67 patients were less than 75 years old (group B). Preoperative demographic and clinical data, surgical procedure, pathologic diagnosis, postoperative course and complication details were collected prospectively and they were analyzed in two group.ResultsThere was no statistical difference between patient groups in terms of gender, comorbidity, preoperative drainage, diagnosis, or laboratory data. Preoperative albumin values were lower in group A (P = 0.04). The mean surgical time in group A was 408.1 ± 73.47 min. Blood loss and blood transfusion were not significantly different between both groups. There was no statistical differences in mortality rate (P = 0.14), morbidity rate (P = 0.43), and mean length of hospital stay (P = 0.22) between both groups.Long-term survival was also no statistically significant difference between the two groups using the log-rank test (P = 0.10).ConclusionIt cannot be ignored that the elderly population is getting larger. We must investigate the management of elderly patients after PD and prepare further for more experiences of PD. If appropriate surgical management is provided to elderly patients, we suggest that PD will lead to no adverse effects after surgery, and PD can be performed safely in elderly patients. We conclude that age should not be a contraindication to PD.

Frequency and risk factors for neovascular glaucoma after vitrectomy in eyes with proliferative diabetic retinopathy.

Purpose:To investigate the rate and risk factors for neovascular glaucoma (NVG) after vitrectomy in proliferative diabetic retinopathy (PDR). Methods:Five hundred and twelve patients (512 eyes) with PDR who underwent vitrectomy between January 1, 2003 and June 30, 2009 at Kumamoto University Hospital, Japan, were retrospectively evaluated. Postoperative NVG was defined as neovascularization in the anterior segment and intraocular pressure (IOP) ≥22 mm Hg after vitrectomy. Kaplan-Meier survival analysis was applied to calculate the rate of NVG after vitrectomy. Risk factors for NVG after vitrectomy were identified by multivariable analysis using the Cox proportional hazards model. Results:The mean follow-up period was 422 days. Twenty-seven of 512 patients (5.3%) developed postoperative NVG after vitrectomy. The probability of NVG occurrence at 6 and 12 months after vitrectomy was 6.0% and 7.1%, respectively. Male sex [relative risk (RR)=4.247; P=0.0032), younger age (RR=0.956/y; P=0.0237), higher baseline IOP (RR=1.203/mm Hg; P=0.0335), preoperative neovascularization in the anterior chamber angle (RR=8.899; P<0.0001), and presence of NVG in the fellow eye (RR=5.355; P=0.0013) were significant risk factors for postoperative NVG. Conclusions:The frequency of NVG in PDR eyes within 1 year after vitrectomy was estimated as 7.1%. The risk is independently associated with male sex, younger age, higher baseline IOP, preoperative neovascularization in the angle, and NVG in the fellow eye.

Endoscopic management of pancreatic duct injury by endoscopic stent placement: a case report and literature review

Recently, the diagnostic evaluation of pancreatic injury has improved dramatically. On the other hand, it is occasionally difficult to diagnose pancreatic injury, because there are no specific signs, symptoms, or laboratory findings. Radiological imaging also often fails to identify pancreatic injury in the acute phase. Delayed diagnosis results in significant morbidity and mortality. Most cases of pancreatic injury with suspicion or pancreatic duct disruption require surgery. Endoscopic retrograde cholangiopancreatography is one of the most accurate modalities for ductal evaluation and therapy and might enable one to avoid unnecessary surgery. We describe endoscopic management of pancreatic duct injury by endoscopic stent placement. A 45-year-old woman was admitted after a traffic accident. A computed tomography scan showed pancreatic parenchyma disruption at the pancreatic head. Endoscopic retrograde cholangiopancreatography demonstrated disruption of the pancreatic duct with extravasation into the peripancreatic fluid collection. A 5-French endoscopic nasopancreatic drainage (ENPD) tube was placed. Her symptoms dramatically improved. ENPD tube was exchanged for a 5-French 5-cm pancreatic stent. Subsequent follow-up CT revealed remarkable improvement. On the 26th day, the patient was discharged from the hospital without symptoms or complications. In this report, a pancreatic stent may lead to rapid clinical improvement and enable surgery to be avoided. On the other hand, the reported complications of long-term follow-up make the role of stenting uncertain. Thus, close attention should be paid to stenting management in the follow-up period. A pancreatic stent is useful for pancreatic ductal injury. If pancreatic ductal injury is managed appropriately, a pancreatic stent may improve the clinical condition, and also prevent unnecessary surgery.