Takeshi Naitoh

Identification of a Novel Gene Family Encoding Human Liver-specific Organic Anion Transporter LST-1

We have isolated a novel liver-specific organic anion transporter, LST-1, that is expressed exclusively in the human, rat, and mouse liver. LST-1 is a new gene family located between the organic anion transporter family and prostaglandin transporter. LST-1 transports taurocholate (K m = 13.6 μm) in a sodium-independent manner. LST-1 also shows broad substrate specificity. It transports conjugated steroids (dehydroepiandrosterone sulfate, estradiol-17β-glucuronide, and estrone-3-sulfate), eicosanoids (prostaglandin E2, thromboxane B2, leukotriene C4, leukotriene E4), and thyroid hormones (thyroxine,K m = 3.0 μm and triiodothyronine,K m = 2.7 μm), reflecting hepatic multispecificity. LST-1 is probably the most important transporter in human liver for clearance of bile acids and organic anions because hepatic levels of another organic anion transporter, OATP, is very low. This is also the first report of the human molecule that transports thyroid hormones.

Molecular characterization and functional regulation of a novel rat liver-specific organic anion transporter rlst-1

BACKGROUND & AIMS Recently, we isolated a new complementary DNA (cDNA) encoding human liver-specific organic anion transporter (LST-1), representing the multispecificity of human liver. The aim of this study was to isolate a rat counterpart of human LST-1 and examine the expression regulation of its messenger RNA (mRNA) to clarify the molecular basis of cholestasis. METHODS A rat liver cDNA library was screened with human LST-1 cDNA as a probe. Xenopus oocyte expression system was used for functional analysis. Northern blot analyses were performed using the isolated cDNA (termed rlst-1). The bile duct ligation model and the cecum ligation and puncture model were used for expression analyses. RESULTS rlst-1 encodes 652 amino acids, predicting at least 11 transmembrane regions. The overall homology with human LST-1 was 60.2%, which is the highest among all known organic anion transporters. rlst-1 also belongs to the same new gene family as human LST-1, located between the organic anion transporter family and the prostaglandin transporter. rlst-1 preferably transports taurocholate (K(m), 9.45 micromol/L) in an Na(+)-independent manner. The rlst-1 mRNA is exclusively expressed in the liver. In both the bile duct ligation model and the cecum ligation and puncture model, mRNA expression levels of rlst-1 were down-regulated. CONCLUSIONS rlst-1 is a counterpart of human LST-1 and is one of the important transporters in rat liver for the clearance of bile acid. The expression of rlst-1 may be under feedback regulation of cholestasis by biliary obstruction and/or sepsis.

Immunohistochemical distribution and functional characterization of an organic anion transporting polypeptide 2 (oatp2)

The rabbit polyclonal antibody against rat organic anion transporting polypeptide 2 (oatp2) was raised and immunoaffinity‐purified. Western blot analysis for oatp2 detected two bands (∼74 and 76 kDa) in rat brain and a single band (76 kDa) in the liver. By immunohistochemical analysis, the oatp2 immunoreactivity was specifically high at the basolateral membrane of rat hepatocytes. Functionally, the oatp2‐expressing oocytes were found to transport dehydroepiandrosterone sulfate, δ1 opioid receptor agonist [d‐Pen2,d‐Pen5]enkephalin, Leu‐enkephalin, and biotin significantly, as well as the substrates previously reported. These data reveal the exact distribution of the rat oatp2 at the protein level in the liver, and that oatp2 appears to be involved in the multispecificity of the uptaking substrates in the liver and brain.

IFSO-APC Consensus Statements 2011

AbstractAssociations of BMI with body composition and health outcomes may differ between Asian and European populations. Asian populations have also been shown to have an elevated risk of type 2 diabetes, hypertension, and hyperlipidemia at a relatively low level of BMI. New surgical indication for Asian patients should be discussed by the expert of this field. Forty-four bariatric experts in Asia-Pacific and other regions were chosen to have a voting privilege for IFSO-APC Consensus at the 2nd IFSO-APC Congress. A computerized audience-response voting system was used to analyze the agreement with the sentence of the consensus. Of all delegates, 95% agreed with the necessity of the establishment of IFSO-APC consensus statements, and 98% agreed with the necessity of a new indication for Asian patients.IFSO-APC Consensus statements 2011Bariatric surgery should be considered for the treatment of obesity for acceptable Asian candidates with BMI ≥ 35 with or without co-morbiditiesBariatric/GI metabolic surgery should be considered for the treatment of T2DM or metabolic syndrome for patients who are inadequately controlled by lifestyle alternations and medical treatment for acceptable Asian candidates with BMI ≥ 30The surgical approach may be considered as a non-primary alternative to treat inadequately controlled T2DM, or metabolic syndrome, for suitable Asian candidates with BMI ≥ 27.5. Other eight sentences are agreed with by majority of the voting delegates to form IFSO-APC consensus statements. This will help to make safe and wholesome the progress of bariatric and metabolic surgery in Asia.

Laparoscope-Assisted Versus Conventional Restorative Proctocolectomy with Rectal Mucosectomy

Abstract To assess the advantages of a laparoscope-assisted proctocolectomy with ileal J-pouch anal anastomosis compared with conventional procedures, we retrospectively analyzed the results of the two procedures as follows: Eleven patients including five patients with familial adenomatous polyposis (FAP) and six with ulcerative colitis (UC) underwent a laparoscope-assisted proctocolectomy and hand-sewn ileal J-pouch anal anastomosis at our department from June 1997 to November 1999. This laparoscope-assisted colectomy (LAC) group was then compared with a group of 13 patients who had undergone conventional ileal pouch anal anastomosis using a standard laparotomy from 1986 to 1997. The median operative time of the LAC group was 8 h 23 min, which was 81 min longer than that of the standard colectomy (SC) group. The number of days during which eating was prohibited were similar in the two groups but the median postoperative hospital stay was significantly shorter in the LAC group (24.1 days). In the LAC group, the small incisions showed better cosmetic results and there was also a remarkable reduction in the degree of postoperative pain. In conclusion, a laparoscope-assisted proctocolectomy with ileal J-pouch anal anastomosis can be employed widely in patients with FAP and also in selected patients with UC.

Inhibitor of apoptosis protein family as diagnostic markers and therapeutic targets of colorectal cancer

The apoptosis and antiapoptotic signaling pathways are important for regulating carcinogenesis and cancer progression, and for determining prognosis. Molecules involved in apoptosis represent potential cancer diagnostic markers and therapeutic targets. The inhibitor of apoptosis protein (IAP) family includes several important molecules involved in apoptosis that might represent such targets. Increasing evidence has demonstrated that the IAP family of proteins is integral for antiapoptotic and nuclear factor-κB signal transduction, and enhanced expression of IAPs contributes to colon carcinogenesis and its poor prognosis, as well as to drug resistance of tumors. X-linked IAP, cIAP1, cIAP2, and survivin are prognostic markers of colorectal cancer, and survivin and cIAP2 are also utilized to predict the effect of anticancer treatment in colorectal cancer patients. Novel therapies such as YM155 and LY2181308 targeting survivin, AEG35156 and phenoxodiol targeting X-linked IAP, AT-406 as a Smac mimetic, and survivin peptides are currently being evaluated in clinical trials. This report reviews the involvement of the IAP family in colorectal adenocarcinoma in order to summarize the role of the IAP family members as diagnostic and therapeutic targets, and to provide an overview of the future course of research in this area.

Hand-assisted laparoscopic digestive surgery provides safety and tactile sensation for malignancy or obesity

AbstractBackground: Some of the persistent problems associated with laparoscopic surgery stem from the inability of the surgeon to palpate the abdominal contents during the operation. This lack of tactile sensation can lead to poor abdominal exploration, difficulty in extracting the organs, and a relatively long operation time compared to conventional procedures. The Dexterity Pneumo Sleeve is a new device that allows the surgeon to insert his or her hand into the abdominal cavity through a small incision while preserving the pneumoperitoneum. Methods: Recently, 13 of our patients underwent hand-assisted advanced laparoscopic surgery using this device. In this series, we had two cases of gastrectomy, two cases of gastric bypass for morbid obesity, two Whipple cases for periampullary tumor, and seven cases of bowel resection. On the basis of this series, we were able to assess the utility of this device. Results: Satisfactory pneumoperitoneum was maintained in 12 of 13 cases. The length of the skin incision was 7.8 cm on average, which was almost the same size as surgeons glove. The device proved to be very useful for tissue retraction and abdominal exploration in all cases and for intracorporeal knot tying in some cases. Conclusions: We found that the device permitted an easier dissection, resection, and anastomosis. It also helped to decrease the operation time.

Laparoscopic cholecystectomy, Calot's triangle, and variations in cystic arterial supply

AbstractBackground: The extrahepatic biliary tree with the exact anatomic features of the arterial supply observed by laparoscopic means has not been described heretofore. Iatrogenic injuries of the extrahepatic biliary tree and neighboring blood vessels are not rare. Accidents involving vessels or the common bile duct during laparoscopic cholecystectomy, with or without choledocotomy, can be avoided by careful dissection of Calots triangle and the hepatoduodenal ligament. Methods: We performed 244 laparoscopic cholecystectomies over a 2-year period between January 1, 1995 and January 1, 1997. Results: In 187 of 244 consecutive cases (76.6%), we found a typical arterial supply anteromedial to the cystic duct, near the sentinel cystic lymph node. In the other cases, there was an atypical arterial supply, and 27 of these cases (11.1%) had no cystic artery in Calots triangle. A typical blood supply and accessory arteries were observed in 18 cases (7.4%). Conclusion: Young surgeons who are not yet familiar with the handling of an anatomically abnormal cystic blood supply need to be more aware of the precise anatomy of the extrahepatic biliary tree.

Effect of Hospital Volume on Surgical Outcomes After Pancreaticoduodenectomy: A Systematic Review and Meta-analysis.

Objective:The aim of the study was to evaluate the relationship between hospital volume and outcome after pancreaticoduodenectomy (PD). Summary Background Data:Previous reviews for the hospital volume-outcome relationship after pancreatic resection were limited owing to clinical or methodological heterogeneity, resulting from differences in surgical procedures and high-volume hospital (HVH) definitions across studies. Methods:We conducted a rigorous meta-analysis on the influence of hospital volume on various outcomes after PD using strict inclusion criteria and single cutoff values for HVHs. Results:Thirteen studies based on nationwide databases from 11 countries, and including 58,023 patients in total, were included in this study. The overall pooled odds ratio (OR) for mortality favoring the HVH group was 2.37 [95% confidence interval (CI): 1.95–2.88] with high heterogeneity (I2 = 63%). We therefore classified all included studies into categories according to the cutoff values for HVH as defined in each individual study. The pooled OR for each category of 1 to 19, 20 to 29, and ≥30 PDs per year was 1.94, 2.34, and 4.05, respectively. There were significant differences among these categories (I2 = 58.9%, P = 0.09). The 2 former categories showed no statistical interstudy heterogeneities. The data did not suggest publication bias. These trends persisted in all subgroup analyses. Postoperative length of stay in the HVH group was significantly shorter with mild interstudy heterogeneity. Conclusions:This meta-analysis included studies from different countries with disparate health care systems and provided strong evidence for an inverse association between higher hospital volume and lower mortality after PD. Variations in HVH cutoff values across studies majorly influenced the overall heterogeneity.

A GNAS Mutation Found in Pancreatic Intraductal Papillary Mucinous Neoplasms Induces Drastic Alterations of Gene Expression Profiles with Upregulation of Mucin Genes

GNAS, a gene encoding G protein stimulating α subunit, is frequently mutated in intraductal papillary mucinous neoplasms (IPMNs), which are indolent and slow-growing pancreatic tumors that secrete abundant mucin. The GNAS mutation is not observed in conventional ductal adenocarcinomas of the pancreas. To determine the functional significance of the GNAS mutation in pancreatic ductal lineage cells, we examined in vitro phenotypes of cells of pancreatic ductal lineage, HPDE, PK-8, PCI-35, and MIA PaCa-2, with exogenous expression of either wild-type or mutated (R201H) GNAS. We found that exogenous GNAS upregulated intracellular cyclic adenine monophosphate (cAMP), particularly in mutated GNAS transfectants, and upregulated expression of MUC2 and MUC5AC in HPDE and PK-8 cells. By contrast, exogenous GNAS inhibited expression of mucin genes in PCI-35 and MIA PaCa-2 cells, despite upregulation of cAMP. We examined global gene expression profiles of some of the cells transfected with exogenous mutated GNAS (PK-8, PCI-35, and MIA PaCa-2), and found that PK-8 cells exhibited drastic alterations of the gene expression profile, which contrasted with modest alterations in PCI-35 and MIA PaCa-2 cells. To identify a cause of these different effects of exogenous mutated GNAS on phenotypes of the cells, we examined effects of interactions of the signaling pathways of G protein-coupled receptor (GPCR), mitogen-activated protein kinase (MAPK), and phosphatidylinositol 3-kinase (PI3K) on expression of mucin genes. The MAPK and PI3K pathways significantly influenced the expression of mucin genes. Exogenous GNAS did not promote cell growth but suppressed it in some of the cells. In conclusion, mutated GNAS found in IPMNs may extensively alter gene expression profiles, including expression of mucin genes, through the interaction with MAPK and PI3K pathways in pancreatic ductal cells; these changes may determine the characteristic phenotype of IPMN. PK-8 cells expressing exogenous mutated GNAS may be an ideal in vitro model of IPMN.