Nesfatin-1 enhances glucose-induced insulin secretion by promoting Ca(2+) influx through L-type channels in mouse islet β-cells

Nucleobindin-2 (NUCB2)-derived nesfatin-1 located in the brain has been implicated in the satiety and control of energy metabolism. Nesfatin-1 is also produced in the periphery and present in the plasma. It has recently been reported that NUCB2/nesfatin-1 is localized in pancreatic islet β-cells in mice and rats and released from islets. However, its function in islets remains largely unknown. This study examined direct effects of nesfatin-1 on insulin release from pancreatic islets and on cytosolic Ca(2+) concentration ([Ca(2+)](i)) in single β-cells from ICR mice. In the presence of 8.3 mmol/L glucose, nesfatin-1 at 10(-10)-10(-9) mol/L tended to increase and at 10(-8) mol/L increased insulin release from isolated islets, while at 2.8 mmol/L glucose nesfatin-1 had no effect. Furthermore, nesfatin-1 at 10(-10)-10(-8) mol/L increased [Ca(2+)](i) in single β-cells in the presence of 8.3 but not 2.8 mmol/L glucose. The nesfatin-1-induced [Ca(2+)](i) increase and insulin release were inhibited by removal of extracellular Ca(2+) and by addition of nitrendipine, a blocker of voltage-dependent L-type Ca(2+) channels. Unexpectedly, the [Ca(2+)](i) responses to nesfatin-1 were unaltered by inhibitors of protein kinase A (PKA) and phospholipase A(2) (PLA(2)). These results indicate that nesfain-1 potentiates glucose-induced insulin secretion by promoting Ca(2+) influx through L-type Ca(2+) channels independently of PKA and PLA(2) in mouse islet β-cells.

Ultrasound predictors of mortality in monochorionic twins with selective intrauterine growth restriction

OBJECTIVES

The aim of this study was to evaluate the use of ultrasound assessment to predict risk of mortality in expectantly managed monochorionic twin fetuses with selective intrauterine growth restriction (sIUGR).

METHODS

This was a retrospective study of 101 monochorionic twin pregnancies diagnosed with sIUGR before 26 weeks of gestation. All patients were under expectant management during the observation period. At the initial evaluation, the presence or absence of each of the following abnormalities was documented: oligohydramnios; stuck twin phenomenon; severe IUGR < 3(rd) centile of estimated fetal weight; abnormal Doppler in the umbilical artery; and polyhydramnios in the larger twin. The relationships between these ultrasound findings and mortality of sIUGR fetuses were evaluated using multiple logistic regression analysis.

RESULTS

Of 101 sIUGR twins, 22 (21.8%) fetuses suffered intrauterine demise and nine (8.9%) suffered neonatal death; 70 (69.3%) survived the neonatal period. Multiple logistic regression analysis revealed that the stuck twin phenomenon (odds ratio (OR): 14.5; 95% CI: 2.2-93.2; P = 0.006) and constantly absent diastolic flow in the umbilical artery (OR: 29.4; 95% CI: 3.3-264.0; P = 0.003) were significant risk factors for mortality.

CONCLUSIONS

Not only abnormal Doppler flow in the umbilical artery but also severe oligohydramnios should be recognized as important indicators for mortality in monochorionic twins with sIUGR.

Long-term infusion of brain-derived neurotrophic factor reduces food intake and body weight via a corticotrophin-releasing hormone pathway in the paraventricular nucleus of the hypothalamus

Brain-derived neurotrophic factor (BDNF) has been implicated in learning, depression and energy metabolism. However, the neuronal mechanisms underlying the effects of BDNF on energy metabolism remain unclear. The present study aimed to elucidate the neuronal pathways by which BDNF controls feeding behaviour and energy balance. Using an osmotic mini-pump, BDNF or control artificial cerebrospinal fluid was infused i.c.v. at the lateral ventricle or into the paraventricular nucleus of the hypothalamus (PVN) for 12 days. Intracerebroventricular BDNF up-regulated mRNA expression of corticotrophin-releasing hormone (CRH) and urocortin in the PVN. TrkB, the receptor for BDNF, was expressed in the PVN neurones, including those containing CRH. Both i.c.v. and intra-PVN-administered BDNF decreased food intake and body weight. These effects of BDNF on food intake and body weight were counteracted by the co-administration of alpha-helical-CRH, an antagonist for the CRH and urocortin receptors CRH-R1/R2, and partly attenuated by a selective antagonist for CRH-R2 but not CRH-R1. Intracerebroventricular BDNF also decreased the subcutaneous and visceral fat mass, adipocyte size and serum triglyceride levels, which were all attenuated by alpha-helical-CRH. Furthermore, BDNF decreased the respiratory quotient and raised rectal temperature, which were counteracted by alpha-helical-CRH. These results indicate that the CRH-urocortin-CRH-R2 pathway in the PVN and connected areas mediates the long-term effects of BDNF to depress feeding and promote lipolysis.

Intra-islet PACAP protects pancreatic β-cells against glucotoxicity and lipotoxicity

Pituitary adenylate cyclase-activating polypeptide (PACAP), a potent insulinotropin, is localized in pancreatic islets. Hyperglycemia and hyperlipidemia impair islet β-cell functions, being recognized as glucotoxicity and lipotoxicity. In this study, we examined whether endogenous PACAP protects islet β-cells against the toxicities. Pancreatic islets were prepared from wild-type and PACAP-null mice, and cultured for 2 days in control conditions containing 5.6 mM glucose, those with elevated 25 mM glucose and those supplemented with 0.4 mM palmitate. After culture in control conditions, a rise in the superfusate glucose concentration from 2.8 mM to a physiologic 8.3 mM increased cytosolic Ca(2+) concentration ([Ca(2+)](i)) in both wild-type and PACAP-null mouse islets. In contrast, after culture with high glucose or palmitate, the glucose-induced first phase [Ca(2+)](i) increases were severely impaired in islets of PACAP-null mice while they were preserved in islets of wild-type mice. Treatment with high glucose or palmitate also impaired glucose-induced insulin secretion in islets and increased mRNA expression of uncoupling protein 2 (UCP2) in islets of PACAP-null, but not wild-type, mice. These data indicate that islet-produced PACAP protects β-cells from deteriorating action of high glucose and palmitate at least partly by blocking the elevation of UCP2, suggesting an anti-diabetic role for PACAP.

Voltage-dependent metabolic regulation of Kv2.1 channels in pancreatic beta-cells

Voltage-gated potassium channels (Kv channels) play a crucial role in formation of action potentials in response to glucose stimulation in pancreatic beta-ells. We previously reported that the Kv channel is regulated by glucose metabolism, particularly by MgATP. We examined whether the regulation of Kv channels is voltage-dependent and mechanistically related with phosphorylation of the channels. In rat pancreatic beta-cells, suppression of glucose metabolism with low glucose concentrations of 2.8mM or less or by metabolic inhibitors decreased the Kv2.1-channel activity at positive membrane potentials, while increased it at potentials negative to -10 mV, suggesting that modulation of Kv channels by glucose metabolism is voltage-dependent. Similarly, in HEK293 cells expressing the recombinant Kv2.1 channels, 0mM but not 10mM MgATP modulated the channel activity in a manner similar to that in beta-cells. Both steady-state activation and inactivation kinetics of the channel were shifted toward the negative potential in association with the voltage-dependent modulation of the channels by cytosolic dialysis of alkaline phosphatase in beta-cells. The modulation of Kv-channel current-voltage relations were also observed during and after glucose-stimulated electrical excitation. These results suggest that the cellular metabolism including MgATP production and/or channel phosphorylation/dephosphorylation underlie the physiological modulation of Kv2.1 channels during glucose-induced insulin secretion.

PDK-1/FoxO1 pathway in POMC neurons regulates Pomc expression and food intake

Both insulin and leptin signaling converge on phosphatidylinositol 3-OH kinase [PI(3)K]/3-phosphoinositide-dependent protein kinase-1 (PDK-1)/protein kinase B (PKB, also known as Akt) in proopiomelanocortin (POMC) neurons. Forkhead box-containing protein-O1 (FoxO1) is inactivated in a PI(3)K-dependent manner. However, the interrelationship between PI(3)K/PDK-1/Akt and FoxO1, and the chronic effects of the overexpression of FoxO1 in POMC neurons on energy homeostasis has not been elucidated. To determine the extent to which PDK-1 and FoxO1 signaling in POMC neurons was responsible for energy homeostasis, we generated POMC neuron-specific Pdk1 knockout mice (POMCPdk1(-/-)) and mice selectively expressing a constitutively nuclear (CN)FoxO1 or transactivation-defective (Delta256)FoxO1 in POMC neurons (CNFoxO1(POMC) or Delta256FoxO1(POMC)). POMCPdk1(-/-) mice showed increased food intake and body weight accompanied by decreased expression of Pomc gene. The CNFoxO1(POMC) mice exhibited mild obesity and hyperphagia compared with POMCPdk1(-/-) mice. Although expression of the CNFoxO1 made POMCPdk1(-/-) mice more obese due to excessive suppression of Pomc gene, overexpression of Delta256FoxO1 in POMC neurons had no effects on metabolic phenotypes and Pomc expression levels of POMCPdk1(-/-) mice. These data suggest a requirement for PDK-1 and FoxO1 in transcriptional regulation of Pomc and food intake.

Expression of KL-6 mucin, a human MUC1 mucin, in intrahepatic cholangiocarcinoma and its potential involvement in tumor cell adhesion and invasion

AIMS

Aberrant expressions of KL-6 mucin were proved to be associated with worse tumor behaviors of many carcinomas. This study was to evaluate the expression KL-6 mucin, a human MUC1 mucin, in intrahepatic cholangiocarcinoma (CC) and its significance in tumor progression.

MAIN METHODS

KL-6 mucin expressions in 21 patients with CC, 12 with combined hepatocellular and cholangiocarcinoma (cHCC-CC), and 78 with hepatocellular carcinoma (HCC) were detected by immunohistochemical staining. The effects of two glycosylation inhibitors (tunicamycin and benzyl-alpha-N-acetylgalactosamine (BAG)) on CC cell proliferations were assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assays. KL-6 mucin expressions were detected by immunocytochemical staining and western blotting after tunicamycin or BAG treatment. Cell adhesive and invasive properties were evaluated by adhesion tests and transwell chamber assays after tunicamycin or BAG treatment.

KEY FINDINGS

Positive KL-6 mucin staining was observed in all CC tissues and CC areas of cHCC-CC tissues. Immunocytochemical staining and western blotting showed that KL-6 mucin expressions were significantly reduced after both inhibitors treatment. Cell adhesive properties were significantly decreased after both inhibitors treatment, while cell invasive abilities were significantly decreased after BAG but not tunicamycin treatment.

SIGNIFICANCE

This study indicated that KL-6 mucin might be a specific tumor target for CC. Therapeutic strategies that target glycosylation of KL-6 mucin may be useful to control aggressive behaviors of CC.

Regulation of voltage-gated K+ channels by glucose metabolism in pancreatic beta-cells

Regulation of delayed rectifier-type K(+) channels (Kv-channels) by glucose was studied in rat pancreatic beta-cells. The Kv-channel current was increased in amplitudes by increasing glucose concentration from 2.8 to 16.6mM, while it was decreased by 2.8mM glucose in a reversible manner (down-regulation) in both perforated and conventional whole-cell modes. The current was decreased by FCCP, intrapipette 0mM ATP or AMPPNP. Glyceraldehyde, pyruvic acid, 2-ketoisocaproic acid, and 10mM MgATP prevented the down-regulation induced by 2.8mM or less glucose. The residual current after treatment with Kv2.1-specific blocker, guangxitoxin-1E, was unchanged by lowering or increasing glucose concentration. We conclude that glucose metabolism regulates Kv2.1 channels in rats beta-cells via altering MgATP levels.

A multicenter, phase III study of carboplatin/paclitaxel versus oral uracil-tegafur as the adjuvant chemotherapy in resected non-small cell lung cancer (NSCLC): Planned interim analyses

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Background: Recent studies have demonstrated that adjuvant chemotherapy provides a survival benefit in patients with resected NSCLC. In Japan, uracil-tegafur has been recognized as a standard adjuvant strategy for resected NSCLC, however, carboplatin based adjuvant chemotherapy has not been fully evaluated for the treatment of NSCLC patients in an adjuvant setting. The present phase III study assessed the efficacy and safety of carboplatin/paclitaxel and oral uracil-tegafur as the first study to compare intravenous and oral drugs in resected stage IB-IIIA NSCLC. Methods: The patients with pathological stage IB-IIIA NSCLC who underwent complete resection were randomized 1:1 to carboplatin (AUC 5) /paclitaxel (175 mg/m2) every 3 week for 4 cycles (A arm) or uracil-tegafur (250 mg/m2) daily for 2 years (B arm). The primary endpoint was overall survival (OS) and secondary endpoints were disease-free survival and toxicity. The accrual of 200 patients per arm is required to demonstrate an improvement of OS (15% increase) in the A arm compared to B arm. Randomization was stratified by histology and tumor stage. An interim analysis was planned to perform on the first 200 patients recruited and data of survival and toxicity were examined in the first 100 patients. Results: Between November 2004 and November 2008, 200 patients from 31 Japanese centers were randomized and the first 100 patients were included for interim analysis. Median age was 69 (range; 50–80) years. Ninety-eight patients had PS of 0–1 and 2 patients had PS of 2. Sixty-seven patients were male and 23 patients were female. Sixty patients had adenocarcinoma, 30 had squamous cell carcinoma, and 10 had other histologies. Disease stage was IB in 53, IIA in 14, IIB in 19, and IIIA in 14 patients. Toxicities observed during adjuvant chemotherapy were well tolerable. There was no toxic death. The median survival time of A and B arms combined was 4.1 year. Monitoring Committees approved to continue the present study. Conclusions: The present phase III trial with carboplatin/paclitaxel or uracil-tegafur is feasible with manageable toxicity. The study is on course to achieve its primary endpoint.

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[Roles and functional interplay of the gut, brain stem, hypothalamus and limbic system in regulation of feeding]

The brain controls feeding via two components; homeostatic and accessory regulation. Homeostatic regulation is executed by the hypothalamic centers. Accessory regulation occurs in response to environmental conditions and stimuli such as memory, stress, emotion, reward and hedonic feeling, which are operated by the limbic system, particularly the hippocampus and amygdala. Nutrients and visceral hormones, representing peripheral metabolic states, regulate activity of these brain areas, which is performed by direct action after entering through blood-brain area and by sending information via the vagus nerve and brain stem. We here review how the hippocampus and amygdala as well as gut, brain stem and hypothalamus function and interact with each other to achieve integrative regulation of feeding.

Peripheral administration of nesfatin-1 reduces food intake in mice: the leptin-independent mechanism

Nesfatin-1 is a novel satiety molecule in the hypothalamus and is also present in peripheral tissues. Here we sought to identify the active segment of nesfatin-1 and to determine the mechanisms of its action after peripheral administration in mice. Intraperitoneal injection of nesfatin-1 suppressed food intake in a dose-dependent manner. Nesfatin-1 has three distinct segments; we tested the effect of each segment on food intake. Injection of the midsegment decreased food intake under leptin-resistant conditions such as db/db mice and mice fed a high-fat diet. After injection of the midsegment, expression of c-Fos was significantly activated in the brainstem nucleus tractus solitarius (NTS) but not in the hypothalamic arcuate nucleus; the nicotinic cholinergic pathway to the NTS contributed to midsegment-induced anorexia. Midsegment injection significantly increased expression of proopiomelanocortin and cocaine- and amphetamine-regulated transcript genes in the NTS but not in the arcuate nucleus. Investigation of mutant midsegments demonstrated that a region with amino acid sequence similarity to the active site of agouti-related peptide was indispensable for anorexigenic induction. Our findings indicate that the midsegment of nesfatin-1 causes anorexia, possibly by activating POMC and CART neurons in the NTS via a leptin-independent mechanism after peripheral stimulation.

Endogenous prolactin-releasing peptide regulates food intake in rodents

Food intake is regulated by a network of signals that emanate from the gut and the brainstem. The peripheral satiety signal cholecystokinin is released from the gut following food intake and acts on fibers of the vagus nerve, which project to the brainstem and activate neurons that modulate both gastrointestinal function and appetite. In this study, we found that neurons in the nucleus tractus solitarii of the brainstem that express prolactin-releasing peptide (PrRP) are activated rapidly by food ingestion. To further examine the role of this peptide in the control of food intake and energy metabolism, we generated PrRP-deficient mice and found that they displayed late-onset obesity and adiposity, phenotypes that reflected an increase in meal size, hyperphagia, and attenuated responses to the anorexigenic signals cholecystokinin and leptin. Hypothalamic expression of 6 other appetite-regulating peptides remained unchanged in the PrRP-deficient mice. Blockade of endogenous PrRP signaling in WT rats by central injection of PrRP-specific mAb resulted in an increase in food intake, as reflected by an increase in meal size. These data suggest that PrRP relays satiety signals within the brain and that selective disturbance of this system can result in obesity and associated metabolic disorders.

Validation of Quintero stage III sub-classification for twin-twin transfusion syndrome based on visibility of donor bladder: characteristic differences in pathophysiology and prognosis

OBJECTIVE

To validate the Quintero stage III subclassification for twin-twin transfusion syndrome (TTTS) based on visibility of the bladder of the donor twin.

METHODS

Between July 2002 and August 2006, there were 131 pregnant Japanese women affected by severe TTTS before 26 weeks' gestation, treated with fetoscopic laser surgery at five centers in Japan, whose pregnancies continued beyond 22 weeks. Outcome data were available in all cases and surviving infants were followed up for at least 6 years. This study focused on the Stage III TTTS patients. These were subclassified into Stage III atypical (abnormal Doppler flow with visible donor bladder) and Stage III classical (abnormal Doppler flow with non-visible donor bladder) groups. Perioperative data and postnatal outcomes were compared between the groups.

RESULTS

Seven Stage I, 22 Stage II, 82 Stage III and 20 Stage IV pregnancies continued beyond 22 weeks. There was a significantly higher incidence of absent or reversed end-diastolic velocity in the umbilical artery (UA-AREDV) of the donor in Stage III atypical than in Stage III classical patients (83.8% vs. 53.3%, P = 0.004). Stage III atypical cases also had a significantly higher incidence of arterioarterial (AA) anastomoses (72.9% vs. 17.8%, P < 0.001) and intrauterine fetal demise (IUFD) of the donor (43.2% vs. 13.3%, P = 0.002). However, there were no differences in overall survival or in abnormal brain scans of surviving infants. Donors with both UA-AREDV and AA anastomoses had a significantly higher incidence of IUFD compared with the others (53.3%, P < 0.001).

CONCLUSIONS

Quintero stage III atypical was characterized by a high incidence of AA anastomoses and UA-AREDV of the donor, resulting in IUFD. Subclassification of Stage III based on visibility of the bladder of the donor twin was adequate for and compatible with differentiating prognosis and pathophysiology.

Effect of benzyl-N-acetyl-α-galactosaminide on KL-6 mucin expression and invasive properties of a human pancreatic carcinoma cell line

KL-6 mucin is a type of MUC1 mucin and its aberrant expression has been shown to be associated with aggressive metastasis and poor clinical outcome in tumors. The present study is to investigate the effects of benzyl-N-acetyl-α-galactosaminide (GalNAc-O-bn), an O-glycosylation inhibitor, on KL-6 mucin expression and invasive properties of a human pancreatic carcinoma cell line, Suit-2 cells. Expression profiles of KL-6 mucin in the cells pretreated with or without 5 mM GalNAc-O-bn for 48 h were examined by Western blotting and immunocytochemical staining and invasive properties were examined by transwell chamber assay. Western blotting and immunocytochemical staining showed that the expression profiles of KL-6 mucin changed significantly after GalNAc-O-bn treatment. Meanwhile, the invasive ability of Suit-2 cells decreased significantly after GalNAc-O-bn treatment (p < 0.05). These results suggest that glycosylation of KL-6 mucin may be closely related to aggressive behaviors of pancreatic cancer cells like metastasis and invasion.