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Dive into the research topics where Masaru Koizumi is active.

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Featured researches published by Masaru Koizumi.


Journal of Gastroenterology | 2006

Clinical diagnostic criteria of autoimmune pancreatitis: revised proposal.

Kazuichi Okazaki; Shigeyuki Kawa; Terumi Kamisawa; Satoru Naruse; Shigeki Tanaka; Isao Nishimori; Hirotaka Ohara; Tetsuhide Ito; Seiki Kiriyama; Kazuro Inui; Tooru Shimosegawa; Masaru Koizumi; Koichi Suda; Keiko Shiratori; Koji Yamaguchi; Taketo Yamaguchi; Masanori Sugiyama; Makoto Otsuki

In 1961, Sarles et al.1 asked the following question regarding the particular cases of pancreatitis with hypergammaglobulinemia: “Chronic inflammatory sclerosis of the pancreas—an autoimmune pancreatic disease?” As similar cases were rarely observed, a relationship between such pancreatitis and autoimmunity was viewed skeptically during the following several decades. In 1992, Toki et al.2 have reported 4 cases with unusual diffuse irregular narrowing of the main pancreatic duct and diffuse enlargement of the entire pancreas due to lymphocyte infiltration. In 1995, Japanese investigators3 firstly proposed a concept of “autoimmune pancreatitis (AIP)”, in which the patients showed diffusely enlarged pancreas, narrowing pancreatogram, increased serum IgG, presence of autoantibodies, fibrotic changes with lymphocytic infiltration and steroidal efficacy. Thereafter, many AIP cases have been reported from Japan, and AIP has been accepted as a new clinical entity.4,5 The histopathological findings of AIP show massive infiltration of lymphoplasmacytes with fibrosis, which is consistent with lymphoplasmacytic sclerosing pancreatitis (LPSP).6 Many Japanese investigators have paid great attention to AIP, especially with regard to its unique pancreatic images,2 IgG4,7 disease-associated autoantibodies,8 extrapancreatic lesions,6,9–14 and steroidal efficacy.14,15 Currently in Japan, diagnosis of AIP is based on the “diagnostic criteria 2002 of autoimmune pancreatitis”16 proposed by the Japan Pancreas Society. However, the accumulation of many AIP cases shows that the concept of AIP has changed slightly to include extrapancreatic lesions and associated disorders, which suggests that the current diagnostic criteria are becoming inadequate. In 2003, the Research Committee of Intractable Diseases of the Pancreas, supported by the Japanese Ministry of Health, Labour and Welfare (Chairman, M. Otsuki), began to review the current diagnostic criteria in light of recently acquired information and knowledge. The team organized a working group (WG), consisting of the team members and researchers specializing in autoimmune pancreatitis, to develop a proposal for the revision of the current diagnostic criteria. On 7 October 2005 and 22 April 2006, the Research Committee of Intractable Diseases of the Pancreas and the Japan Pancreas Society jointly held open forums to discuss the proposed amendments. This report describes the background of the proposed amendments and the final proposal for the revised version of the clinical diagnostic criteria of AIP.


Diabetes | 2006

Blockade of Pancreatic Islet–Derived Ghrelin Enhances Insulin Secretion to Prevent High-Fat Diet–Induced Glucose Intolerance

Katsuya Dezaki; Hideyuki Sone; Masaru Koizumi; Masanori Nakata; Masafumi Kakei; Hideo Nagai; Hiroshi Hosoda; Kenji Kangawa; Toshihiko Yada

The gastric hormone ghrelin and its receptor, growth hormone secretagogue receptor (GHSR), are expressed in pancreas. Here, we report that ghrelin is released from pancreatic islets to regulate glucose-induced insulin release. Plasma concentrations of ghrelin, as well as insulin, were higher in pancreatic veins than in arteries. GHSR antagonist and immunoneutralization of endogenous ghrelin enhanced glucose-induced insulin release from perfused pancreas, whereas exogenous ghrelin suppressed it. GHSR antagonist increased plasma insulin levels in gastrectomized and normal rats to a similar extent. Ghrelin knockout mice displayed enhanced glucose-induced insulin release from isolated islets, whereas islet density, size, insulin content, and insulin mRNA levels were unaltered. Glucose tolerance tests (GTTs) in ghrelin knockout mice showed increased insulin and decreased glucose responses. Treatment with high-fat diet produced glucose intolerance in GTTs in wild-type mice. In ghrelin knockout mice, the high-fat diet–induced glucose intolerance was largely prevented, whereas insulin responses to GTTs were markedly enhanced. These findings demonstrate that ghrelin originating from pancreatic islets is a physiological regulator of glucose-induced insulin release. Antagonism of the ghrelin function can enhance insulin release to meet increased demand for insulin in high-fat diet–induced obesity and thereby normalize glycemic control, which may provide a potential therapeutic application to counteract the progression of type 2 diabetes.


Journal of Hepato-biliary-pancreatic Surgery | 2006

JPN Guidelines for the management of acute pancreatitis: epidemiology, etiology, natural history, and outcome predictors in acute pancreatitis

Miho Sekimoto; Tadahiro Takada; Yoshifumi Kawarada; Koichi Hirata; Toshihiko Mayumi; Masahiro Yoshida; Masahiko Hirota; Yasutoshi Kimura; Kazunori Takeda; Shuji Isaji; Masaru Koizumi; Makoto Otsuki; Seiki Matsuno

Acute pancreatitis is a common disease with an annual incidence of between 5 and 80 people per 100 000 of the population. The two major etiological factors responsible for acute pancreatitis are alcohol and cholelithiasis (gallstones). The proportion of patients with pancreatitis caused by alcohol or gallstones varies markedly in different countries and regions. The incidence of acute alcoholic pancreatitis is considered to be associated with high alcohol consumption. Although the incidence of alcoholic pancreatitis is much higher in men than in women, there is no difference in sexes in the risk involved after adjusting for alcohol intake. Other risk factors include endoscopic retrograde cholangiopancreatography, surgery, therapeutic drugs, HIV infection, hyperlipidemia, and biliary tract anomalies. Idiopathic acute pancreatitis is defined as acute pancreatitis in which the etiological factor cannot be specified. However, several studies have suggested that this entity includes cases caused by other specific disorders such as microlithiasis. Acute pancreatitis is a potentially fatal disease with an overall mortality of 2.1%–7.8%. The outcome of acute pancreatitis is determined by two factors that reflect the severity of the illness: organ failure and pancreatic necrosis. About half of the deaths in patients with acute pancreatitis occur within the first 1–2 weeks and are mainly attributable to multiple organ dysfunction syndrome (MODS). Depending on patient selection, necrotizing pancreatitis develops in approximately 10%–20% of patients and the mortality is high, ranging from 14% to 25% of these patients. Infected pancreatic necrosis develops in 30%–40% of patients with necrotizing pancreatitis and the incidence of MODS in such patients is high. The recurrence rate of acute pancreatitis is relatively high: almost half the patients with acute alcoholic pancreatitis experience a recurrence. When the gallstones are not treated, the risk of recurrence in gallstone pancreatitis ranges from 32% to 61%. After recovering from acute pancreatitis, about one-third to one-half of acute pancreatitis patients develop functional disorders, such as diabetes mellitus and fatty stool; the incidence of chronic pancreatitis after acute pancreatitis ranges from 3% to 13%. Nevertheless, many reports have shown that most patients who recover from acute pancreatitis regain good general health and return to their usual daily routine. Some authors have emphasized that endocrine function disorders are a common complication after severe acute pancreatitis has been treated by pancreatic resection.


Pancreas | 1996

K-ras mutation and p53 protein accumulation in intraductal mucin-hypersecreting neoplasms of the pancreas.

Kennichi Satoh; Tooru Shimosegawa; Shigeki Moriizumi; Masaru Koizumi; Takayoshi Toyota

Intraductal mucin-hypersecreting neoplasm of the pancreas (IMHN) is a unique tumor that is composed of tumor cells with different cell atypia. K-ras and p53 alterations have been shown to occur in pancreatic duct cell carcinoma (PDC). but they have not been well documented in the individual lesion of IMHN. The aim of this study was to examine the relation of the genetic alterations of K-ras and p53 in IMHN to the tumorigenesis of the pancreas. In 32 microscopically dissected lesions of seven cases of IMHN, the K-ras mutation was investigated by primer-mediated, mutant-enriched, polymerase chain reaction-restriction fragment length polymorphism. Mutant p53 expression was examined in the adjacent serial sections by immunohistochemistry. In IMHN, alterations of K-ras and p53 were frequently observed (71.9 and 50%, respectively). The frequency became higher as the grade of cell atypia increased. Simultaneous alterations of the two genes were detected in carcinoma and its accompanying hyperplastic and dysplastic lesions. It is suggested that alterations of K-ras and p53 may be early events in the tumorigenesis of IMHN and may cooperate to produce neoplastic transformation of the pancreatic duct epithelium.


Journal of Hepato-biliary-pancreatic Surgery | 2006

JPN Guidelines for the management of acute pancreatitis: medical management of acute pancreatitis

Kazunori Takeda; Tadahiro Takada; Yoshifumi Kawarada; Koichi Hirata; Toshihiko Mayumi; Masahiro Yoshida; Miho Sekimoto; Masahiko Hirota; Yasutoshi Kimura; Shuji Isaji; Masaru Koizumi; Makoto Otsuki; Seiki Matsuno

The basic principles of the initial management of acute pancreatitis are adequate monitoring of vital signs, fluid replacement, correction of any electrolyte imbalance, nutritional support, and the prevention of local and systemic complications. Patients with severe acute pancreatitis should be transferred to a medical facility where adequate monitoring and intensive medical care are available. Strict cardiovascular and respiratory monitoring is mandatory for maintaining the cardiopulmonary system in patients with severe acute pancreatitis. Maximum fluid replacement is needed to stabilize the cardiovascular system. Prophylactic antibiotic administration is recommended to prevent infectious complications in patients with necrotizing pancreatitis. Although the efficacy of the intravenous administration of protease inhibitors is still a matter of controversy, there is a consensus in Japan that a large dose of a synthetic protease inhibitor should be given to patients with severe acute pancreatitis in order to prevent organ failure and other complications. Enteral feeding is superior to parenteral nutrition when it comes to the nutritional support of patients with severe acute pancreatitis. The JPN Guidelines recommend, as optional measures, blood purification therapy and continuous regional arterial infusion of a protease inhibitor and antibiotics, depending on the patient’s condition.


Current Diabetes Reviews | 2008

Ghrelin Regulates Insulin Release and Glycemia: Physiological Role and Therapeutic Potential

Toshihiko Yada; Katsuya Dezaki; Hideyuki Sone; Masaru Koizumi; Boldbaatar Damdindorj; Masanori Nakata; Masafumi Kakei

Insulin release from pancreatic islet beta-cells is stimulated by glucose. Glucose-induced insulin release is potentiated or suppressed by hormones and neural substances. Ghrelin, a novel acylated 28-amino acid peptide isolated from stomach, is the endogenous ligand for the growth hormone (GH) secretagogue-receptor (GHS-R). Circulating ghrelin is produced predominantly in stomach. Ghrelin is a potent stimulator of GH release and feeding as well as exhibiting positive cardiovascular effects. In relation to the glucose metabolism, initial studies indicated that low plasma ghrelin levels are associated with elevated fasting insulin levels, insulin resistance, and obesity. It has recently been demonstrated that ghrelin suppresses glucose-induced insulin release via G alpha(i2) subtype of GTP-binding proteins and delayed outward K(+) (Kv) channels, representing a novel signaling mechanism, and that the ghrelin originating from islets regulates insulin release and thereby glycemia. Furthermore, elimination of ghrelin enhances insulin release to prevent or ameliorate glucose intolerance in high-fat diet fed mice and ob/ob mice. This review focuses on the physiological roles of ghrelin in regulating insulin release and glycemia, the insulinostatic mechanisms of ghrelin in islet beta-cells, and the potential of ghrelin-GHS-R system as the therapeutic target to treat type 2 diabetes.


Journal of Hepato-biliary-pancreatic Surgery | 2006

JPN Guidelines for the management of acute pancreatitis: severity assessment of acute pancreatitis.

Masahiko Hirota; Tadahiro Takada; Yoshifumi Kawarada; Koichi Hirata; Toshihiko Mayumi; Masahiro Yoshida; Miho Sekimoto; Yasutoshi Kimura; Kazunori Takeda; Shuji Isaji; Masaru Koizumi; Makoto Otsuki; Seiki Matsuno

This article addresses the criteria for severity assessment and the severity scoring system of the Ministry of Health and Welfare of Japan; now the Japanese Ministry of Health, Labour, and Welfare (the JPN score). It also presents data comparing the JPN score with the Acute Physiology and Chronic Health Evaluation (APACHE) II score and the Ranson score, which are the major measuring scales used in the United States and Europe. The goal of investigating these scoring systems is the achievement of earlier diagnosis and more appropriate and successful treatment of severe or moderate acute pancreatitis, which has a high mortality rate. This article makes the following recommendations in terms of assessing the severity of acute pancreatitis: (1) Severity assessment is indispensable to the selection of proper initial treatment in the management of acute pancreatitis (Recommendation A). (2) Assessment by a severity scoring system (JPN score, APACHE II score) is important for determining treatment policy and identifying the need for transfer to a specialist unit (Recommendation A). (3) C-reactive protein (CRP) is a useful indicator for assessing severity (Recommendation A). (4) Contrast-enhanced computed tomography (CT) scanning and contrast-enhanced magnetic resonance imaging (MRI) play an important role in severity assessment (Recommendation A). (5) A JPN score of 2 or more (severe acute pancreatitis) has been established as the criterion for hospital transfer (Recommendation A). (6) It is preferable to transfer patients with severe acute pancreatitis to a specialist medical institution where they can receive continuous monitoring and systemic management.


Journal of Hepato-biliary-pancreatic Surgery | 2006

JPN Guidelines for the management of acute pancreatitis: surgical management

Shuji Isaji; Tadahiro Takada; Yoshifumi Kawarada; Koichi Hirata; Toshihiko Mayumi; Masahiro Yoshida; Miho Sekimoto; Masahiko Hirota; Yasutoshi Kimura; Kazunori Takeda; Masaru Koizumi; Makoto Otsuki; Seiki Matsuno

Acute pancreatitis represents a spectrum of disease ranging from a mild, self-limited course to a rapidly progressive, severe illness. The mortality rate of severe acute pancreatitis exceeds 20%, and some patients diagnosed as mild to moderate acute pancreatitis at the onset of the disease may progress to a severe, life-threatening illness within 2–3 days. The Japanese (JPN) guidelines were designed to provide recommendations regarding the management of acute pancreatitis in patients having a diversity of clinical characteristics. This article sets forth the JPN guidelines for the surgical management of acute pancreatitis, excluding gallstone pancreatitis, by incorporating the latest evidence for the surgical management of severe pancreatitis in the Japanese-language version of the evidence-based Guidelines for the Management of Acute Pancreatitis published in 2003. Ten guidelines are proposed: (1) computed tomography-guided or ultrasound-guided fine-needle aspiration for bacteriology should be performed in patients suspected of having infected pancreatic necrosis; (2) infected pancreatic necrosis accompanied by signs of sepsis is an indication for surgical intervention; (3) patients with sterile pancreatic necrosis should be managed conservatively, and surgical intervention should be performed only in selected cases, such as those with persistent organ complications or severe clinical deterioration despite maximum intensive care; (4) early surgical intervention is not recommended for necrotizing pancreatitis; (5) necrosectomy is recommended as the surgical procedure for infected pancreatic necrosis; (6) simple drainage should be avoided after necrosectomy, and either continuous closed lavage or open drainage should be performed; (7) surgical or percutaneous drainage should be performed for pancreatic abscess; (8) pancreatic abscesses for which clinical findings are not improved by percutaneous drainage should be subjected to surgical drainage immediately; (9) pancreatic pseudocysts that produce symptoms and complications or the diameter of which increases should be drained percutaneously or endoscopically; and (10) pancreatic pseudocysts that do not tend to improve in response to percutaneous drainage or endoscopic drainage should be managed surgically.


Cancer | 1993

An immunohistochemical study of the c-erbB-2 oncogene product in intraductal mucin-hypersecreting neoplasms and in ductal cell carcinomas of the pancreas.

Kennichi Satoh; Hironobu Sasano; Tooru Shimosegawa; Masaru Koizumi; Tadashi Yamazaki; Fukuji Mochizuki; Nobuyuki Kobayashi; Tsuyoshi Okano; Takayoshi Toyota; Takashi Sawai

Background. Intraductal mucin‐hypersecreting neoplasm of the pancreas (IMHN) is a unique tumor that has a tendency to spread intraductally. The clinical outcome of IMHN generally is far better than that of pancreatic ductal cell carcinoma. Because of the presence of various cell atypia within the same tumor, it sometimes is difficult to make an accurate histopathologic diagnosis and, therefore, predict its biologic behavior. It has been shown that overexpression of c‐erbB‐2 protein in breast cancer with lymph node metastases is related to a poor prognosis. Overexpression of c‐erbB‐2 protein has been reported as an infrequent event in pancreatic ductal cell carcinoma, but little is known in the case of IMHN.


Journal of Hepato-biliary-pancreatic Surgery | 2006

JPN Guidelines for the management of acute pancreatitis: treatment of gallstone-induced acute pancreatitis.

Yasutoshi Kimura; Tadahiro Takada; Yoshifumi Kawarada; Koichi Hirata; Toshihiko Mayumi; Masahiro Yoshida; Miho Sekimoto; Masahiko Hirota; Kazunori Takeda; Shuji Isaji; Masaru Koizumi; Katsusuke Satake; Makoto Otsuki; Seiki Matsuno

Gallstones, along with alcohol, are one of the primary etiological factors of acute pancreatitis, and knowledge of the etiology as well as the diagnosis and management of gallstones, is crucial for managing acute pancreatitis. Because of this, evidence regarding the management of gallstone-induced pancreatitis in Japan was collected, and recommendation levels were established by comparing current clinical practices with optimal clinical practices. The JPN Guidelines for managing gallstone-induced acute pancreatitis recommend two procedures: (1) an urgent endoscopic procedure should be performed in patients in whom biliary duct obstruction is suspected and in patients complicated by cholangitis (Recommendation A); and (2) after the attack of gallstone pancreatitis has subsided, a laparoscopic cholecystectomy should be performed during the same hospital stay (Recommendation B).

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Naohiro Sata

Jichi Medical University

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Hideo Nagai

Jichi Medical University

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Makoto Otsuki

University of Occupational and Environmental Health Japan

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